Advances in Child Development and Behavior Volume 1

ADVANCES IN CHILD DEVELOPMENT AND BEHAVIOR

VOLUME I

ConsuIting Editors ICIE MACYHOOBLER

V. MEREDITH HOWARD

Contributors to this Volume Donald M. Baer Sidney W. Bijou Gordon N. Cantor Betty J. House Lewis P. Lipsitt Howard V. Meredith David S. Palermo Hayne W. Reese Charles C. Spiker Joachim F. Wohlwill David Zeaman

ADVANCES IN CHILD DEVELOPMENT AND BEHAVIOR edited by Lewis P. Lipsitt Psychology Department Brown University Providence, Rhode Islund

Charles C. Spiker Institute of Child Behavior and Development State University of Iowa Iowa City, Iowa

VOLUME I

@ 1963 ACADEMIC PRESS New York London

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l i s t of Contributors Numbers in parentheses indicate the page on which the author’s contribution begins.

DONALD M. BAER Developmental Psychology Laboratory, Department of Psychology, University of Washington, Seattle, Washington (197) SIDNEY W. BIJOU Developmental Psychology Laboratory, Department of Psychology, University of Washington, Seattle, Washington (197) GORDON N. CANTOR Institute of Child Behavior and Development, State University of Iowa, Iowa City, Iowa ( 1 ) BETTY J. HOUSE Department of Psychology, University of Connecticut, Storrs, Connecticut (313)

LEWIS P. LIPSITT Psychology Department, Brown University, Providence, Rhode Island ( 147) HOWARD V. MEREDITH Institute of Child Behavior and Development, State University of Iowa, Iowa City, Iowa ( 6 9 ) DAVID S. PALERMO Department of Psychology, The Pennsylvania State University, University Park, Pennsylvania ( 3 1 ) HAYNE W. REESE Department of Psychology, State University of New York at Buffalo,Buffalo, New York ( 1 1 5 ) CHARLES C. SPIKER Institute of Child Behavior and Development, State University of Iowa, Iowa City, Iowa ( 2 3 3 ) JOACHIM F. WOHLWILL Department of Psychology, Clark University, Worcester, Massachusetts (265) DAVID ZEAMAN Department of Psychology, University of Connecticut, Storrs, Connecticut (313)

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Preface During the past decade or so, the field of child development and behavior has experienced a rapid increase in the number of research and theoretical publications. Use of original sources by scientists and students in maintaining a scholarly knowledge both within and outside their areas of specialization has become a most formidable task. The serial publication of Advances in Child Development and Behavior is intended to provide scholarly reference articles in the field and to serve two purposes. On the one hand, it is hoped that teachers, research workers, and students will find these critical syntheses useful in the endless task of keeping abreast of growing knowledge in areas peripheral to their primary focus of interest. There is currently an indisputable need for technical, documented reviews which would facilitate this task by reducing the frequency with which original papers must be consulted, particularly in such secondary areas. O n the other hand, the editors are also convinced that research in child development has progressed to the point that such integrative and critical papers will be of considerable usefulness to researchers within problem areas of great concern to their own research programs. The editors will make no attempt to organize each volume around a particular topic or theme. Rather they will solicit manuscripts from investigators conducting programmatic research on problems of current interest. They will often encourage the preparation of critical syntheses dealing intensively with topics of relatively narrow scope but of potentially considerable interest to the scientific community. Although appearance in the volumes is ordinarily by invitation, unsolicited manuscripts will be welcomed for review if submitted in outline form. The present volume could not have been published without the aid of several persons in addition to those who accepted formal responsibility for its preparation. A special debt of gratitude is owed to Raymond H. Hohle, Richard B. Millward, and Fred Stollnitz, who assisted by the critical reading of manuscripts which the editorial staff found itself unable to handle without additional help. Appreciation is also expressed to the institutions which generously provided the editors with time and facilities to carry out the necessary work: the State University of Iowa and Brown University, the latter celebrating its bicentennial anniversary at the time of this publication.

November, 1963

LEWISP. LIPSITT CHARLESC. SPIKER

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Contents List of Contributors

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Preface Responses of Infants and Children to Complex and Novel Stimulation GORDON N . CANTOR

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1 Introduction . . . . . . . . . . . . II A Frame of Reference . . . . . . . . . A . Berlyne's Discussion of Stimulus SeIection Behaviors B. Scope of the Present Review . . . . . . . 111 Studies of Stimulus Complexity . . . . . . A . Infant Research . . . . . . . . . . B. Child Research . . . . . . . . . . . IV. Studies of Stimulus Novelty . . . . . . . . A . Relevant Research . . . . . . . . . . B . Overview of the Novelty Research and Related Studies V Conclusions . . . . . . . . . . . .

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Word Associations and Children's Verbal Behavior

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DAVID S PALERMO

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1 Historical Interest i n Children's Word Associations .

A . Early German Studies . . . . . . B. First English Studies . . . . . . . C . Woodrow and Lowell Study . . . . D. Studies since Woodrow and Lowell . . II Recent Uses of Word Associations . . A . Studies of Adult Verbal Behavior . . . B. Studies of Children's Language . . . C . Experimental Manipulation of Associations 111. A Normative Study of Word Associations A . Rationale . . . . . . . . . B. The List of Words . . . . . . C . Procedure . . . . . . . . . D . Subjects . . . . . . . . . . E. Results . . . . . . . . . . F Response Classifications . . . . .

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Contents

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IV Experimental Uses of the Normative Data A . Paired- Associate Learning . . . . . B. Associative Clustering In Recall . . . C . Associative Generalization . . . . . D . Future Research . . . . . . . References.

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1 Introduction . . . . . II. Review of the literature .

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HAYNE W. REESE 115

Discriminafion Learning Set in Children

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111 Recent Approaches . . . . . . IV Theoretical Analysis and Conclusions .

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A . Mean Body Weight in Infancy . . . . . . . . 89 B. Mean Body Weight in Early Childhood . . . . . . 92 C . Distribution of Body Weight at Selected Ages from Middle Childhood into Adolescence . . . . . . . . . 95 D. Mean Body Weight in Late Adolescence and Early Adulthood . . . . . . . . . . . . . . . 102 E. Graph of Mean Body Weight Circa 1880 and 1960 . . 104

IV Postscript .

A . Experimental Variables . . . . . . . . . . . B. Subject Variables . . . . . . . . . . . . C . Response Variables . . . . . . . . . . . D . Summary and Conclusions . . . . . . . . . .

References

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A . Mean Stature at Birth . . . . . . . . . . . B. Mean Stature at Ages 1 Year and 3 Years . . . . . C . Distribution of Stature at Age 6 Years . . . . . . D. Stature Comparisons by Geographic Region, Racial Ancestry. and Socioeconomic Status . . . . . . . . . . E. Distribution of Stature at Selected Ages between 9 Years and 16 Years . . . . . . . . . . . . . F. Mean Stature at Age 17 Years and in Early Adulthood . . G. Graph of Mean Stature Circa 1880 and 1960 . . . .

111 Secular Change in Body Weight .

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Change in the Sfature and Body Weighf of North American Boys HOWARD V MEREDITH during the Last 80 Years

1 Introduction . . . . . II Secular Change in Stature .

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116 118 118 121 123 134 135 138 141

Contents LEWIS P. LIPSITT

Learning i n the First Year of Life

. Introduction . . . . . . . . Definition of learning . . . . . The Prenatal Period . . . . . . lnfrahuman Infant learning . . . The First Three Weeks After Birth .

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A . Classical Aversive Conditioning . . . B. Classical Appetitional Conditioning . . C. Operant Learning . . . . . . . D . The Adaptation-Habituation Phenomenon

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VI The Fourth Week and Beyond . . . A . Classical Aversive Conditioning . . . . . . . B. Classical Appetitional Conditioning . . . . . . C. Operant Learning . . . . . . . . . . . D . An Issue: Operant Control versus Operant Learning . VII Summary . . . . . . . . . . . . . .

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Some Mefhodological Confributions from a Functional Analysis of ChildDevelopment SIDNEY W BIJOU and DONALD M BAER

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1 The laboratory-Experimental Method Applied to Past Interactions: A n Example of Abstraction learning . . . II Another Approach to an Experimental Study of Past Experiences . . . . . . . . . . . . . . 111. Some Methodological Problems in the Analysis of Social Reinforcement . . . . . . . . . . . . . . IV laboratory-Experimental Studies of Social Reinforcement . V Field-Experimental Studies of Social Reinforcement . . . VI Concluding Comments . . . . . . . . . . .

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1 Introduction . . . . . . . . . . . . . . I1 The Hypothesis of Stimulus Interaction . . . . . . A . Application of Stimulus Interaction to the Simultaneous and Successive Discrimination Problems . . . . . . . B. Convenient Equations for Special Cases . . . . . . Ill Deduction With the Hypothesis of Stimulus Jnteraction . . A . Stimulus Similarity in the Simultaneous and Successive Discrimination Problems . . . . . . . . . .

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The Hypothesis of Stimulus Interaction and an Explanation of CHARLES C SPIKER Stimulus Compounding

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Contents B. Cue-Position Compounding and Discrimination Problems . 253 C . The Conditional Discrimination . . . . . . . . 261 IV Summary . . . . . . . . . . . . . . . 263

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264

The Development of "Overconstancy" in Space Perception

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JOACHIM F. WOHLWILL

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1 The Problem of "Overconstancy" in Space Perception

A . The Overconstancy Phenomenon . . . . . . . . B. The Evidence of Overconstancy in Adults . . . . . C Determinants of Overconstancy . . . . . . . . D . Theoretical Significance of Overconstancy . . . . . E. Overconstancy as a Problem for a Developmental Psychology of Perception . . . . . . . . . . . . .

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I1 Constancy and Beyond: A Survey of the Developmental literature . . . . . . . . . . . . . . . A . Age Changes in Size Constancy . . . . . . . . B. Age Changes in the Perception of Distance Relationships . C. Discussion . . . . . . . . . . . . . . 111 An Investigation of the Development of Overconstancy i n Distance Perception . . . . . . . . . . . . A . Background and Purpose . . . . . . . . . . B. Method . . . . . . . . . . . . . . . C . Results and Discussion . . . . . . . . . . IV Constancy and Overconstancy: A Reassessment . . . V A Note on Research Strategy in the Study of the Development of Perception . . . . . . . . . . . .

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272 273 274 2 86 290 292 292 296 296 302 307 310

Miniature Experiments i n the Discrimination Learning of Retardates

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BETTY J HOUSE and DAVID ZEAMAN 313

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1 Methodology

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A . Complexity of Discrimination Learning . . B. Complexity. A Partial Outgrowth of Design C. Alternative Designs . . . . . . .

. . I1. Data and Theory . . . . . . . . . . A . Experiment One: Compounding . . . . .

. . . . B . Experiment Two: 1-Dimensional Component Learning . C. Experiment Three : Components-Plus-l-Compound-Cue .

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Contents D. Experiment Four: 1 -Dimensional Problems with a Variable Irrelevant Dimension . . . . . . . . . . . 339 E . Experiment Five: Conflict and Combination of Cues . . 344

111. Mathematical Treatments

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C. Experiments One and Two . . . D. Further Applications of the Models . IV General Summary . . . . . . A. Methodology . . . . . . . B. Findings . . . . . . . . C. Theoretical Implications: Qualitative . D. Theoretical Implications: Quantitative

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Author Index

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Subject Index

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‘~(-ESPONSES OF INFANTS AND CHILDREN TO COMPLEX AND NOVEL STIMULATION

Gordon N. Cuntorl INSTITUTE OF CHILD BEHAVIOR AND DEVELOPMENT, STATE UNIVERSITY OF IOWA

I. INTRODUCTION .

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11. A FRAME OF REFERENCE . . . . . . . . . . . A. BERLYNE’S DISCUSSION OF STIMULUS SELECTION BEHAVIORS . . . . . . . . . . . . . B. SCOPE OF THE PRESENT REVIEW . . . . . . 111. STUDIES OF STIMULUS COMPLEXITY . A. INFANT RESEARCH . . . . . B. CHILD RESEARCH . . . . .

IV. STUDIES OF STIMULUS NOVELTY

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A. RELEVANT RESEARCH . . . . . . . . . . . . B. OVER-VIEW OF THE NOVELTY RESEARCH AND RELATED STUDIES . . . . . . . . . . . . . . . . .

V. CONCLUSIONS REFERENCES

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‘The writer is grateful to Joan H. Cantor for a careful reading of the manuscript and for numerous constructive suggestions. This review was prepared in conjunction with a program of research on children’s responses to novel and complex stimuli (NIMH Grant 06624-01).

I. Introduction The decades of the 1940’s and 1950’s marked a time of mounting interest on the part of psychologists in stimulus selection behaviors, i.e., the tendencies of infrahuman and human organisms to engage in selective orienting, exploratory, and manipulative activities. The large body of information accumulated in this area (preponderantly infrahuman data), together with research findings on a variety of other topics (e.g., latent learning, stimulus deprivation, brain stimulation, consummatory behaviors), has presented serious difficulties for the major extant theories of motivation, including the drive-reduction position of Hullian theory. The indisputable fact that organisms with reduced tissue tensions will persistently and vigorously seek stimulation suggests that “quiescence” does not necessarily constitute the optimal state of affairs pictured by drive-reduction theory. R. W. White (1959), after examining the evidence on exploratory behaviors, concluded that explanations of such phenomena employing the concepts of tissue tension reduction, anxiety reduction, and secondary reinforcement are inadequate. The strength of White’s conviction on this matter is indicated by his pronouncement (White, 1959, p. 305) that, “Twenty years of research have . . . pretty much destroyed the orthodox drive model.” Writing specifically for child psychologists, J. McV. Hunt (1960) has expressed a similar viewpoint. The currently available alternatives to the “orthodox” drive-reduction formulation range from the postulation of special-purpose motives (manipulative drives, exploratory drives, activity drives, curiosity drives) to extremely broad conceptualizations, as represented in Morgan’s (1957) discussion of the central-motive state, Woodworth’s ( 1958) behavior-primacy (as contrasted with need-primacy) theory, R. W. White’s (1959) notion of competence motivation, and Hunt’s ( 1960) incongruity-dissonance principle. Although drive-reduction theory is being hard pressed, scholarly defenses of the position are available (see, e.g., Brown, 1960). Furthermore, the alternative conceptualizations are not without their difficulties. The circularity characterizing much of the thinking about special-purpose motives has been effectively pointed out by both Brown (1960) and Mowrer (1960). The more general formulations are, without exception, vulnerable to charges of vagueness. Without doubt, major issues in motivation theory such as the role of drive reduction have by no means been settled. Under the circumstances, it would seem appropriate that behavior scientists continue to invest time and energy in the study of stimulus selection behaviors, particularly in human subjects. Such phenomena are interesting in their own right, and knowledge

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Responses to Complex and Novel Stimuldtion about them may well play a role in determining the future directions taken by motivation theory. The present review will be devoted to a summary and critical analysis of research on stimulus selection behaviors in infants and children. Rather sharp limitations will be placed upon the types of studies to be considered, the following section serving to detail the nature of these restrictions.

XI. A Frame of Reference A. BERLYNE’S DISCUSSION OF STIMULUSSELECTION BEHAVIORS Of the various workers interested in stimulus selection behaviors, perhaps none has been as persistent and productive as D. E. Berlyne. His efforts at both an empirical and a theoretical level led to the publication in 1960 of his book, Conflict, Arousal, and Curiosity. In the present writer’s view, two major contributions are contained in Berlyne’s volume: (a) an attempt to identify and define several stimulus properties (the so-called “collative” variables) which appear to be importantly related to stimulus selection behaviors; and (b) an inventive use of the concept of conflict in accounting for such relationships. The major hypothesis in Berlyne’s theory suggests that the perception of stimuli high in “collative” properties, i.e., complexity, novelty, uncertainty, surprisingness, and incongruity, results in the arousal of incompatible response tendencies (conflict) in the organism. Such tendencies may be conceptualized, insofar as the human subject is concerned, as involving implicit identifying responses or diverse expectancies of various sorts. Since the presence of such competing tendencies constitutes a state of conflict, the organism is said to maintain commerce with the stimuli in question until the conflict has been resolved. The critic will not find it difficult to question Berlyne’s presentation on a number of counts. One theoretical problem facing Berlyne relates to the question of why the organism, when confronted with a conflict-inducing stimulus, does not simply withdraw from the stimulus in order to achieve conflict reduction. It should be noted at this point that the viability of Berlyne’s conflict theory will not be of central concern here, since a demonstration of its untenability would have no necessary bearing on the significance of the collative variables, two of which will be of major concern in the present review. Thus, if one or more of the collative variables can be clearly defined and can be shown to relate to stimulus selection behaviors, at least one of Berlyne’s emphases will have proven to be fruitful. The extent to which Berlyne has been successful in providing clear definitions of the collative variables remains as another serious question, as does the degree to which the various variables, once clearly defined, will turn out

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Gordon N.Cantor to be independent of one another. In the present writer’s opinion, two of them-complexity and novelty-show the most promise of being characterized by some degree of independence. The remaining concepts-uncertainty, surprisingness, and incongruity-appear to bear considerable likelihood of being highly related to the variables of complexity and/or novelty. For this reason, the present survey will be largely concerned with the available evidence relating infants’ and children’s stimulus selection behaviors to stimulus complexity and novelty, as these two terms have been used by Berlyne. 1. Definition of Stimulus Complexity Stimulus complexity refers to the amount of variety or diversity in a stimulus pattern. Degree of complexity is considered by Berlyne to be positively related to the number of distinguishable elements in a stimulus complex and to the extent of dissimilarity between elements; complexity varies inversely with the degree to which several elements in a complex are responded to as a unit. While the definition of complexity as just outlined provides for a certain degree of communication at an intuitive level, it is clearly unsatisfactory from an operational standpoint. In this connection, Berlyne (1960, p. 38) has observed that, of the various collative variables, complexity presents the severest definitional problems. The most successful attempts at becoming explicit about complexity appear to be contained in studies providing quantifications of the contour and symmetry characteristics of stimuli. TO date, only one study involving infants or children as subjects (Spears, 1962) has made use of this approach, the nature of which will be examined when the Spears experiment is discussed in some detail in Section 111, A, 3. The remaining studies IargeIy utilize intuitive choices of stimuli, depending upon pictorial respresentation of the stimuli so chosen to communicate the author’s meaning of complexity. 2. Definition of Stimulus Novelty Berlyne defines novelty as the presence in a stimulus of some property never perceived previously by the organism (“absolute” novelty) or the presence of familiar elements or qualities in a combination or pattern which is new in the organism’s experience (“relative” novelty). An additional meaning of novelty has to do with the organism’s recent experience; that is, a stimulus may be considered novel because it has not been encountered for a period of days, months, or years (“long-term” novelty) or because it has not been perceived for a period of minutes or hours (“short-term” novelty). From the meanings given above, it is clear that novelty cannot be considered independently of the individual organism’s past experience, whereas

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Responses t o Complex and Novel Stimulation complexity can be so regarded. The difficulties inherent in the task of obtaining firm knowledge of the human subject’s history of experience with stimulation have led, as will be seen, to the general practice in experimental situations of familiarizing the subject with one set or class of stimuli, and then providing a choice between these stimuli and ones not previously encountered in that situation. The assumption is made that the latter stimuli are “novel” in comparison with those seen during the familiarization period.

B.

SCOPE OF

THE

PRESENTREVIEW

Although this discussion will focus primarily on the complexity and novelty variables, occasional reference wil1 be made to apparently related stimulus properties such as uncertainty and incongruity. Indeed, it will at times appear to be a moot question as to what variable is being manipulated in a given experiment. One other major criterion for inclusion of studies in this survey has to do with the nature of the experimental situation faced by the subject. Attention will be restricted to studies in which the subjects merely observe and, in some cases, manipulate stimuli, but have no opportunity to engage in any kind of problem solving activity. The intent here is to rule out complicating variables relating to the subject’s level of aspiration, his desire to obtain the experimenter’s approval, and other achievement-related considerations.

111. Studies of Stimulus Complexity2 A. INFANT

RESEARCH

Because particularly difficult methodological problems arise in studying stimulus selection behaviors in infants, it would appear worthwhile to devote a separate subsection to a consideration of infant research concerned with the complexity variable. Three relevant studies are known to the writer. 1. Bedyne In an experiment concerned with orienting behavior in 14 infants aged 3-9 months, Berlyne (1958a) used four stimulus triads, as described in Table I. Each of the 3 possible pairs of stimuli within a given triad was presented

’For adequate communication, this section ideally should include reproductions of the stimulus materials utilized in the various studies to be reviewed. Because of the prohibitive cost of such a procedure, the alternative approach of providing verbal descriptions of the stimuli will generally be followed. The reader is urged to consult the original references to obtain more direct information regarding the stimuli used.

Gordon N.Cantor twice to all subjects, once in each left-right spatial arrangement. The total set of 24 presentations was ordered in a semi-randomized sequence, onehalf the subjects being given this sequence and the remaining subjects receiving a sequence formed by reversing the temporal order and interchanging the left-right relationships of the stimuli. The subject lay supine or was propped in a sitting position. One experimenter placed the two stimuli for a given trial side by side on a board; a second experimenter, unable to see the stimuli involved, waited until the THE STIMULI

TABLE I BERLYNB’S STUDY

USED IN

Description of stimuli Triad

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2

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Plain black rectangle

Plain gray rectangle

Plain white rectangle

White diamond on black background

Irregular white figure on black background

Randomly distributed black and white dots

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Rectangle--) black, -) white; vertical straight-line demarcation

Rectangle--) white, black; vertical curved-line demarcation

Rectangle-; white, 3 black; vertical jagged-line demarcation

IV

Rectangle-; black, -) white; horizontal straight-line demarcation

Black and white checkerboard design, 4 squares

Black and white checkerboard design, 16 squares

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subject was looking straight ahead and then placed the stimuli in the subject’s field of vision from above. The observing experimenter judged which of the two stimuli the subject fixated first on each trial. When a decision regarding first fixations could not be made (“on one or two occasions”), the same pair was repeated later in the sequence. Analysis of the data indicated that stimuli 11-3 and IV-3 (see Table I) were fixated first significantly more often than were the remaining stimuli in triads I1 and IV, respectively; there were no other significant differences. Berlyne noted that the two stimuli which were “especially attractive” to the subjects contained considerably more contour than the others in their respective triads. No attempt was made to quantify amount of contour in the various stimuli. I n comparison with other procedures to be discussed subsequently, Berlyne’s cannot be considered very precise. The observer’s lack of awareness of which

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Responses to Complex and Novel Stimulation stimuli were being presented on a given trial is an admirable feature of the study, but no evidence is given regarding the reliability of judgments of “first fixations,” nor are the effects of using the rather crude manual presentation procedure known. Perhaps the major question to be raised regarding the study pertains to the measure utilized, i.e., number of first fixations. Some evidence to be reviewed later suggests that an individual’s preference for 1 of 2 stimuli, as indicated by his initial choice behavior, may be unreIated or even inversely related to the amount of time he spends viewing these stimuli when he has eventually observed both of them (see Section 111, By 1). Since no comparison of the stimuli by the subjects was involved in Berlyne’s index, it would probably be more appropriate to speak of the “attention eliciting” property of the stimuli, rather than of a “preference” on the part of the subject. 2. Fdntz

A substantial methodological advance in the study of human infants’ observing responses appears to be contained in the work of Fantz (1958a; 1961). This investigator used the four stimulus diads described in Table I1 to

THESTIMULI

TABLE I1 FANTZ’S STUDY

USED IN

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Description of stimuli Diad

I

1

2

Red and white bull’s-eye pattern

Red and white horizontal stripes

Red and white checkerboard design, 25 squares

Plain red square

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Plain red cross

Plain red circle

IV

Plain red triangle

Plain red triangle

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evaluate pattern vision in 30 infants who ranged in age from 1 to 15 weeks at the time of their initial testing. The fourth diad (identical red triangles) was included for control purposes. The diads, in the order listed, were considered to involve decreasing amounts of complexity. Ten weekly sessions were given to each of 22 subjects. Incomplete data were obtained on eight additional infants. The subject lay on his back on a form-fitting crib designed to prevent gross head and body movements, the

7

Gordon N.Cantor crib being contained within a test chamber. The stimulus pairs were presented 1 ft above the subject’s head and spaced 1 ft apart; each pair was presented twice in succession, with the left-right relationship reversed on the second exposure. In this fashion, 8 test periods, each lasting 30 sec, were given during a weekly session. The subject’s eyes were observed through a &in. hole located in the ceiling of the chamber, midway between the stimuli. The chamber was illuminated so that the experimenter could observe images of the stimuli reflected on the surface of the infant’s eyeball. When a stimulus was fixated, its image coincided with the pupil of the eye. Amount of attention paid by the subject to each pattern was measured by depressing one of two telegraph keys operating separate electric timers whenever the image of that pattern coincided with the pupil. The time scores derived from the two 30-sec exposures of a given stimuIus pair in a given session were summed, these s u m s then being averaged over the ten sessions. In one report on this work, Fantz (1961, p. 68) comments that, “The total time spent looking at the various pairs differed sharply, the more complex pairs drawing the greater attention.” However, no statistical evaluation of this between-diad comparison is reported. A bar graph (Fantz, 1961, p. 70) presenting average seconds of fixation for the eight stimuli reveals that the 22 subjects given 10 weekly tests spent approximately the following amounts of time (out of a possible 60 sec) observing the various diads and individual stimuli: diad I: 29 sec (1-1: 19 sec; 1-2: 10 sec); diad 11: 23.4 sec (11-1: 16.25 sec; 11-2: 7.25 sec); diad 111: 24 sec (111-1: 12.25 sec; 111-2: 11.75 sec); and diad IV: 19 sec (IV-1: 10 sec; IV-2: 9 sec). Thus, while the most and least complex diads elicited the most and least amounts of observing behavior, respectively, the remaining 2 diads were observed for amounts of time of essentially comparable magnitudes. Insofar as the within-diad differences are concerned, Fantz reports significant differences (P < .OOl) for diads I and I1 and no significant differences for diads I11 and IV. In terms of total scores for all 10 weekly sessions, 20 out of 22 subjects showed a preference for the bull’s-eye as opposed to the stripes, while 19 of 22 subjects preferred the checkerboard to the square. The (unspecified) statistical tests were apparently applied to these frequency data rather than to the time scores. With respect to diad I, the subjects at the youngest ages tended to prefer the stripes to the bull’s-eye pattern; however, this preference was reversed at about 7 weeks of age, the subjects from then on preferring the bull’seye. In order to demonstrate that this reversal cannot be attributed to experience in the testing situation, Fantz assembled initial (i.e., first session) observing times for 30 subjects whose first test sessions occurred over an age range of from less than 2 weeks to more than 15 weeks. The 16 subjects first seen prior to age 7 weeks tended, with two exceptions, to prefer the

8

Responses to Complex and Novel Stimulation stripes in these initial sessions, whereas the 14 subjects first tested after age 7 weeks without exception showed a preference for the bull’s-eye. In contrast, a preference for the checkerboard over the square (diad 11) appeared to exist from an early age and was maintained throughout the age span studied. This preference is said to have increased significantly, but the nature of the statistical test involved is not specified. Fantz’s measurement technique would appear to constitute a substantial step in the direction of objectivity in assessment of infant observing behavior. However, no information regarding the reliability of judgment in obtaining the time scores is provided, nor is the variable of stimulus complexity quantified in any fashion. Fantz’s approach to the reporting of statistical details is rather casual. One is led to wonder why tests were not applied to the time scores themselves as well as to the frequency data based on the time scores. The absence of a preference for diad I1 over diad 111, as well as the inexplicable shift in preference from the stripes to the bull’s-eye in diad I, suggest that variables other than complexity, per se, were of importance in this situation. 3. Spears In his infant study concerned with the complexity variable, Spears (1962) was interested in color as well as shape preferences and also with the dominance of color or shape in determining infants’ discriminative responses. Only that part of the research bearing on shape preferences will be reviewed here. Ten 4-month-old subjects were run in each of 5 groups.8 The subject, supported in a sitting position, was exposed to the open end of a box containing a pair of vertically placed stimulus cards located side by side and near the rear of the box. The opening of hinged doors mounted in front of the stimuli permitted the subject visual access to the stimuli. A third hinged door containing a one-way viewing slot was located on the rear of the box, allowing the experimenter to manipulate the stimuli and to observe the subject’s visual fixations. Table 111 indicates the stimuli utilized for the various groups. Spears attempted to quantify the stimuli, using three different measures of complexity: (a) amount of contour; (b) number of “turns”; and (c) degree of symmetry. The contour criterion involved measurement along the transition boundaries of colored and white areas, producing the following values, in increasing order of complexity: X = 0; Di = 94 in.; Ra = 244 in.; Ch = 26 in.; Hex = 344 in.; and Bu = 363 in. The second index, njrmber of turnr, was based on a definition used by Attneave (1957) which involves a

See footnote a, Table 111.

9

Gordon N.Cantor counting the number of independent angles or curves in the contour of a figure. This measure ordered the stimuli as follows, again in increasing order of complexity: X = 0; Bu = 0 ; Di = 2; Ch = 18; Ra = 24; and Hex = 24. The third index, degree of symmetry, was chosen on the basis of discussions of information theory (e.g., Attneave, 1954) which identify TABLE 111

THESTIMULI

USED IN SPEARS' STUDY

Description of stimuli Group5

1

2

2 red squares placed Red and white

diagonally on a white background (RDi)

bull's-eye (RBu)

2 red squares placed Red and white

diagonally on a white background (RDi)

bull's-eye (RBu)

2 red squares placed Red and white

diagonally on a white background (RDi)

bull's-eye (RBu)

2 red squares placed Red and white

diagonally on a white background (RDI)

bull's-eye (RBu)

3

Red and white Random red shapes on white backcheckerboard, 16 squares (RCh) ground (RRa)

Plain red square (RX)

Random red shapes a n white background (RRa)

Plain red square (RX)

Red and white checkerboard, 16 squares (RCh)

Gray and white 2 gray squares bull's-eye (GBu) placed diagonally (GDI)

Yellow and white Blue and white Blue and white hexagonal-shaped hexagonal-shaped bull's-eye (BBu) bull's-eye (YHex) bull's-eye (BHex) a

4

Yellow and white bull's-eye (YBu)

Groups 1, 2, and 3 were used for tests of form preferences only. Groups 5 and 6 allowed for tests of form of color dominance, as well as color and form preferences. Group 4 (not discussed in this review) invo1ved:a test of color preference only.

symmetry as a form of redundancy and regard both of these as the converse of complexity; thus, this criterion equates lack of symmetry with complexity. In a search for means of quantifying degree of symmetry, Spears was led to a volume on esthetics by Birkhoff (1933) which provides one such technique. By combining three symmetry indices suggested by Birkhoff in an arbitrary fashion, Spears found that his forms were ordered as follows, in decreasing order of symmetry (and thus increasing order of complexity) :

10

Responses to Complex and Novel Stimulation Bu = 03; Ch = 16; Hex = 12; Di = 4 ; and Ra = 1. Spears considered the plain red card ( X ) difficult to quantify, indicating that defensible arguments could be mounted for its having infinite symmetry ( X = w ) or minimal symmetry ( X = 1). For a given subject, each of the 6 possible pairs of stimuli was presented on two 15-sec trials, once in each of the 2 left-right spatial arrangements. Half the subjects in a group were given the 1 2 presentations in one random order, the remaining 5 subjects being presented the pairs in the reverse order. A toggle switch wired to a counter and to 2 electric timers was manipulated by the experimenter in the direction of and contiguously with the subject’s eye movements and fixations. If the subject glanced away from both stimuli, the switch was thrown to the central, neutral position. Groups 1-3 were run with the experimenter having knowledge of which stimuli were being presented. However, 6 subjects were run by naive observers to obtain a check on reliability. No details concerning this reliability estimate are provided, the author merely noting, “No differences were apparent in times recorded and preferences shown.” The remaining subjects were run with the experimenter having no knowledge of which stimuli were being presented on a given trial. The results were analyzed using only the f i r ~ t presentations of the 6 possible pairs for each group. In terms of the time scores (i.e., amount of time the subjects spent fixating the various stimuli), a determination was made of the number of subjects in a given group who preferred one member of a stimulus pair over the second member of that pair. By use of a sign test, a statistically significant preference was indicated when one member of a pair was preferred by +“a or 98 subjects in the group. The preference orderings of the various stimuli, together with identifications of the significant differences, are shown in Table IV. TABLE IV RESULTSOF THE SPEARSSTUDY Group

Orderings

1 2

> Ch > Ra > D i > Bu > X > Di Bu > Ch > Di = X RBu > GBu > RDi > GDi YHex > BBu > BHex > YBu

3 5 G

Bu Ra

Significant differences Bu > Di, Ra Bu > Di, Bu Bu > Di, Bu all pairs no pairs

> Di > X, Ra > Di >X

It is of some interest that nine of the 11 obtained significant differences which involve form preference indicate the attention-eliciting character of the bull’s-eye pattern. The fact that the bull’s-eye pattern had the highest

11

Gordon N.Cantor contour value led Spears to conclude that the variable of amount of contour may be of importance in determining infants’ stimulus selection behavior. Additional support for this is found in the failure to obtain a significant difference between Ch and Ra (group 1) or between Bu and Hex (group 6 ). The failure of Ch to be significantly preferred to D i or X (groups 1 and 3 ) , however, provides negative evidence for the contour variable. The index, number of turns, receives some support as a pertinent dimension from the two significant differences between Ra and Di (groups 1 and 2), but several of the findings indicate the variable is unrelated to the subjects’ responses (e.g., the general superiority of Bu and the absence of a significant difference between Bu and Hex). None of the results points to the significance of the symmetry variable; the heavy preference for the highly symmetrical (“simple”) bull’s-eye pattern actually provides negative evidence in this regard. Spears (1962, p. 50) was consequently led to conclude that, . . the practice of equating redundancy and symmetry and considering them as the converse of complexity, variously defined, gains no support from our findings . . . Spears does not indicate why only half of the time score data were utilized, nor is any mention made of the frequency data collected by means of the counter. As in the Fantz study, the time scores were used to generate frequency data (number of subjects preferring one stimulus to another) and no statistical tests were run on the time scores themselves. The use of reliability checks on judgments involved in obtaining the time scores (groups 1-3) and the technique of blind stimulus presentation (groups 5-6) constitute major methodological strengths in this research. Mention should be made of Spears’ careful analysis of position biases in the subjects (found to be negligible) and his check for response consistency as indicated by the absence of nontransitive triads (a considerable degree of intraindividual and intragroup consistency in this regard was found). The study is unique among infant or child research projects in this area in its use of physical measurement techniques designed to objectify the variable of stimulus complexity. While it may turn out to be the case that psychological scaling will provide the most fruitful means of quantifying complexity (Dember and Earl, 1957), the alternative of physical measurement is an attractive one and it is to be hoped that further attempts will be made along these lines. “

.

.”

4. Overview of the Infant Research on Complexity Taken together, the three studies just reviewed offer considerable support for the contention that reliable form preferences can be demonstrated in infants. It is less clear that a variable of stimulus complexity, however defined,

12

Responses to Complex and Novel Stimzllation relates systematically to such preferences. The measure of amount of contour would appear to offer some promise in this regard, however. It is explicitly cited by both Berlyne and Spears, and apparently could be used to account for Fantz’s within-diad differences. As indicated previously, however, some of Spears’ findings do not support the contour explanation; the same may be said of Fantz’s failure to demonstrate a between-diad difference involving his diads I1 and 111. The extreme importance of unbiased stimulus presentations and of objective assessment of orienting responses in infants is apparent; the Spears study appears to fare best in the former regard, the Fantz technique offering the most promise in the latter respect.4

B.

CHILDRESEARCH

1. Spitz and Hoats Three groups of subjects, each containing equal numbers of males and females, were run in this study (Spitz and Hoats, 1961, Experiment # 1 ) : (a) 30 retardates (mean CA = 15.4 years, mean MA = 8.7 years) ; (b) 30 “equal MA” normals (mean CA = 8 years); and (c) 30 “equal CA” normals (mean CA = 16.6 years). Thirty pairs of stimuli, equally divided among 6 classes, were used. For 4 of the classes involved, the members of each stimulus pair appeared to differ in complexity, as defined by Berlyne, the differences being in terms of: (a) irregularity of arrangement of elements in a stimulus pattern (e.g., symmetrically vs. asymmetrically arranged triangles); (b) amount of material (e.g., 6 vs. 8 symmetrically arranged squares) ; (c) heterogeneity of elements (e.g., 4 symmetrically arranged squares vs. symmetrically arranged elements involving 4 different geometric forms) ; and ( d ) irregularity of arrangement (e.g., a diamond vs. an irregular form of about the same area). The remaining two classes, labeled “incongruity” and “incongruous juxtaposition,” appear to contain stimuli differing more in novelty than in complexity. The “incongruity” class involved the pairing of a picture of an ordinary animal with that of an “incongruous” animal having a mismatched head and body (e.g., an elephant’s head on a lion’s body); in the “incongruous juxtaposition” class, one member of a pair consisted of two ordinary pictures (e.g., a car and a rabbit), the second member of the pair being made up of 2 figures with intermixed components obtained from ‘In a report of some work involving a neonate chimpanzee subject, Fantz has described a photographic technique designed to obtain permanent records fixations; the desirability of using such an approach with human infants seems For a description of an elaborate apparatus designed for the study of infants’ tory” behavior, see Rheingold et al. (1962).

(1958b) of ocular apparent. “explora-

13

Gordon N.Cantor the figures in the first member. Twenty-two of the stimulus pairs were taken from Berlyne (1958b), the remaining 8 being developed for use in this study. Each pair was flashed on a screen for a 3-sec period. Following the offset of a pair, the subject was allowed to reproduce one of the members in the pair for any amount of time up to 30 sec by pressing a lever located in front of the member of his choice. For a given subject, note was made of the stimuli so selected by him and the length of time he projected each reproduced figure. For convenience in discussing the results, the authors’ practice will be followed by using the term “complex” to refer indiscriminately to selections of stimuli which involve irregularity, contain greater amounts of material, are of a heterogeneous nature, or are incongruous. Unfortunately, the data most relevant to this review, concerning the tendency of the subjects either to select or avoid the more complex stimuli, are given rather scanty treatment by Spitz and Hoats. With 30 opportunities for each subject to make a choice, one would expect an average of 15 choices of complex stimuli, if the subjects selected indifferently between more and less complex figures. However, the subjects as a group chose only 10.33 complex stimuli, on the average, a finding which conflicts with that of Berlyne (1958b), who found a definite preference for complex figures, using normal adult subjects and a different procedure, but many of the same stimuli. The authors do not test for the statistical significance of this finding, merely concluding that the subjects made a “heavy” selection of the less complex figures. Inspection of subgroup means, however, does indicate that this may be a significant finding, since it appears consistently among 5 of 6 subgroups (broken down according to group and sex) and for 5 of the 6 stimulus classes. Only with respect to the variable of amount of material does this pattern fail to hold up, the subjects in this case showing a slight preference for the more complex figures. Under the assumption that any tendency to choose the more complex stimuli indicates a degree of “perceptual curiosity” in the subjects, Spitz and Hoats proceed to an intensive analysis of subgroup differences in this regard, a consideration which is not particularly germane to the present review. However, in the course of their discussion, the authors make brief mention of one other finding, having to do with the time measure, which is of considerable interest here. Spitz and Hoats report that the median length of time the “equal CA” subjects held their complex choices in view significantly exceeded the length of time they spent observing the less complex choices. A similar difference was found for the “equal MA” group, but at a level which did not reach statistical significance ( P < .lo). No such difference appeared in the retarded group. Thus, while the subjects as a

14

Responses to Complex and Novel Stirnzrlation total group chose to reproduce the complex stimuli less frequently than the simple figures, there was some evidence that the complex stimuli, when chosen, were viewed for longer periods of time. The authors’ decision to include 6 different stimulus classes, plus their concern with individual difference variables (IQ, CA, MA, and sex) and their use of an elaborate counterbalancing procedure to handle the problem of order of stimulus presentations, led to an exceedingly complicated study, the results of which are difficult to evaluate. The greatest strength of the experiment lies, in this reviewer’s opinion, in the objective nature of the stimulus presentation technique and the criterion measures utilized. However, no statistical test of the interaction between stimulus-class categories and stimulus complexity was reported. Instead of performing such an analysis, the authors concentrate on an examination of differences in “perceptual curiosity” among the various subgroups, considering these differences separateIy for each of the six stimulus classes as well as for the 30 stimulus pairs as a whole. The fact that the “equal CA” subjects chose complex figures less frequently, but projected them for longer periods of time, is perhaps the most interesting finding, but one which must be interpreted with caution. This analysis was run separately for the three major groups of subjects, with a clear difference being found for only the one group. The finding that the more complex figures were chosen for reproduction less frequently than were the less complex stimuli certainly points to the need for further research utilizing this procedure and criterion m e a s ~ r e . ~ 2. Smock and Holt

In an experiment described as being concerned with children’s reactions to novelty, Smock and Holt (1962) manipulated several stimulus properties, only one of which relates in any clear-cut fashion to Berlyne’s concept of novelty. Some of the remaining variables appear to involve the concept of complexity, whereas others are not easily categorized in this regard; consequently, a major portion of this study will be reviewed in the present section, with discussion of an additional small segment dealing with stimulus novelty being reserved for Section IV, A, 4. Forty-four first grade children served as subjects. They observed a variety of stimuli via strip film projection and could either cause a given stimulus ‘Additional evidence consistent with this finding was obtained in another study (Spitz and Hoats, 1961, Experiment # 3 ) involving a discrimination learning task in which the positive stimulus was an asymmetrical figure and the negative stimulus a symmetrical figure for half the subjects, the reverse being the case for the remaining subjects.

1s

Gordon N.Cantor to be presented repeatedly for 250 msec intervals by pressing a button, or could change from one figure to another by pressing a lever. Three major sets of stimuli were used, these being labeled: (a) “stimulus ambiguity”; (b) “perceptual conflict”; and (c) “conceptual conflict.” The meanings of these terms are not immediately apparent to this reviewer. Table V indicates the nature of the stimuli comprising the various sets. The authors are not entirely clear regarding the manner in which the criterion measures were handled. Concerning the “stimulus ambiguity” set, e.g., they state (p. 635), “An index of curiosity motivation was obtained . by subtracting the frequency of self-controlled exposures to the less complex (sic) from the more complex (sic) figure.” How this applies to #3 (see Table V) is not evident; presumably, only the responses to the circle and

..

TABLE V SMOCK-HOLT STUDY”

, T H E STIMULI USED IN T H E

Set

Description of the stimuli

“Stimulus Ambiguity”

(1) Square with crosses arranged in 3 X 3 matrix vs. square with crosses

“Perceptual Conflict”

(1) 5 “nonincongruous” (“familiar”) and 2 ”incongruous”b animal pic-

“Conceptual Conflict”

(la) 6 pictures starting with a circle and, by progressive addition of details, ending in a picture of a bear; the series arranged in a“meaningfu1” sequence Same as above, but in a random sequence Same as la, but involving the picture of a clown Same as above, but in a random sequence

irregularly arranged (2) Square with 5 straight (parallel?) lines vs. square with “wavy and dotted” lines (3) 4 figures “ranging from a circle to a form with highly irregular contour” (4) 6 randomly generated nonsense forms “containing either 4 or 24 points” (taken from Attneave, 1954)

tures (2) 5 “nonincongruous” (“familiar”) and 2 “incongruous”b bird pictures

-The authors indicate that “many” of the stimuli were taken from Berlyne (1958b). 6 These figures involved mismatched components, as in the Spitz-Hoats-study.

the most irregular form were used in the analysis. In regard to the “perceptual conflict” set, the authors indicate (p. 635), “The difference in frequency of response to incongruous as compared to nonincongruous pictures, for the sets combined, was used as the index of preference for novelty.” How this could literally be the case is unclear, in view of the fact that

16

Responses to Complex and Novel Stimulation 10 “non-incongruous” and only 4 “incongruous” figures were involved. In the exposure to the “conceptual conflict” set, each subject received one of the series in a “meaningful” order and the other in a random order (with the appropriate counterbalancing being involved). In this case (p. 635), “The measure of curiosity was the difference in total frequency of selfcontrolled exposures to the pictures in the random as compared to the meaningful series.” In discussing their results, the authors use the term “novelty” in referring to all of the comparisons indicated in Table V. An analysis of variance (Type VI design, Lindquist, 1953) was run involving “tasks” as one of the main effects. This variable included the 4 comparisons involved in the “stimulus ambiguity” set plus the remaining 2 sets treated as individual “tasks” (see Table V). The remaining main effects were sex and “novelty.” The analysis, as run, revealed a significant main effect in the direction of more frequent productions of the “novel” stimuli. It is incorrectly concluded that this is the case “on all tasks,” since the “novelty X task” interaction was found to be significant and no tests of simple effects were run. A pooled error term was used to assess all the “within-subjects’’ effects (i.e., all the effects except that for sex), although no information is presented regarding the appropriateness of pooling the individual error terms ordinarily used to assess “within-subjects” effects in this kind of design. Consequently, with the exception of the sex variable and the novelty effect (which, in view of the very large F value, was undoubtedly significant), the results of this analysis must be interpreted with caution. Further analyses involving the sex variable and the relation of the “curiosity” scores to a measure of “perceptual rigidity” are reported. The stimulus presentation technique used in this study would appear to have much to recommend it. The experimental design, statistical analysis, and interpretive material, however, are vulnerable to numerous criticisms, many of which have been mentioned in the discussion thus far. Note should be made of the uncritical and rather inconsistent use of terminology that characterizes the Smock-HoIt report. The indiscriminate use of the term “novelty” seems most unfortunate, The authors themselves at times use the term “complexity” in referring to the “stimulus ambiguity” set; while one may perhaps defend the contention that the “perceptual conflict” set involves a manipulation of stimulus novelty, it is difficult to see the relevance of the term, in any of its common meanings, to the “conceptual conflict” set. As in the case of the Spitz-Hoats study, it is regrettable that Smock and Holt chose to manipulate a disparate variety of stimulus properties. This choice, together with the concern over individual difference variables, seems to have stood in the way of an adequate analysis and interpretation of what appear to be basically interesting and useful data.

17

Gordon N.Cantor 3. R. B. May A theoretical formulation by Dember and Earl (1957) led to the design of a study by May (1962) concerned with stimulus complexity. The experiment involved 2 1 preschoolers as subjects (mean age 4 years, 3 months). The theory proposes that complexity be regarded as a psychological variable, to be assessed by psychological measurement techniques; it thus involves a departure from a premise endorsed implicitly if not explicitly by most workers in the area, namely, that stimuli can meaningfully be ordered on a complexity continuum via physical measurements, Furthermore, the theory attributes “complexity” to the perceiving organism as well as to the perceived stimuli, the organism’s “complexity value” changing as a result of exposure to stimulation. Attention arousing properties are said to inhere in stimuli having complexity values somewhat (but not too much) greater than the momentary complexity value of the organism. Inexplicably, May did not apply a psychological scaling technique to arrive at complexity values for the stimuli used in his study.6 Instead, complexity level was identified with the number of differently colored rectangles appearing on 5 x 8-in. cards. Five levels, involving 2, 3, 5 , 8, or 12 rectangles, were used, with 10 instances of each level being included. I n each case, the rectangles were located in a semirandom arrangement on the card. The subject was first handed the deck of cards considered to be of a “medium” complexity level ( 5 rectangles) and was told in this adaptation phase to examine the cards in this deck. Subsequently, all 5 decks were placed before him in a random order with the instruction that he could look at any of the cards in any of the decks, but could look at only 1 card at a time. In this testing situation, 20 of the 2 1 subjects selected a card from a deck other than the “medium” deck on their first choices. Of these 20 subjects, 16 chose a card having more than 5 rectangles (P = .006, onetailed sign test). Eighteen of 20 subjects whose total selections indicated a preference in either direction chose a majority of their cards from the more complex decks (P < .001, one-tailed sign test). Since a control group given no adaptation experience with the medium complexity deck was not included in the experiment, one cannot conclude that this experience established a “complexity level” in the subjects themselves. However, it is of interest that the subjects did show a preference for the more complex stimuli in the test situation, complexity being defined simply in terms of amount of material involved in the stimuli. ‘ A complexity study by Earl (1957), also stemming from the Dember-Earl theory, did include an elaborate psychological scaling approach. Since the experimental task used by Earl fix., arranging colored wooden blocks to reproduce printed patterns of varying difficulty IeveIs) may be construed as comprising a level-of-aspiration situation, the research will not be reviewed here.

18

Responses to Complex and Novel Stimulation May gathered additional data on the same subjects, using a task involving the copying of “meaningless” tinker toy assemblies varying in shape, color, and number of components. The procedure and results were essentially similar to those of the first experiment. 4. Cantor, Cantor, and Ditrichs In a study involving 60 preschoolers (age range 3 years, 9 months to 5 years, 6 months), Cantor et al. (1963) presented the 6 stimulus triads shown in Fig. I. Two of the triads (111 and V) were patterned after stimuIi used Complexity level Triod db

Low

Medium

High

I

V

Fig. 1. The stimuii rued in the Cantor, Cantor, and Ditrirhs study.

by Berlyne (1958a), the remaining ones being developed for use in this study. Three light-proof boxes were utilized for stimulus presentation purposes. The front face of each box contained a viewing aperture and a hinged panel located just above the aperture. By pressing with his forehead against the panel, the subject caused a light within the box to be turned on and an electric clock to be activated. When the panel was depressed, the subject’s eyes were in front of and close to the viewing aperture, allowing him to see a stimulus placed at the rear of the illuminated box. Release of the panel

19

Gordon N.Cantor deactivated both the light and the clock. Grooves in the rear of the boxes allowed for the insertion of the stimulus panels. The three boxes were arranged in a semicircle in front of the subject with each stimulus from a particular triad inserted in a different box. T h e subject was instructed that he could look as much or as little as he chose at any or all of the stimuli contained in a triad in the time allotted. Changing back and forth among the boxes was encouraged. A 60-sec period was allowed for viewing a given triad. The order of presentation of the triads was randomly determined for each individual. Six subgroups were constituted to allow for counterbalancing of the spatial arrangement of the stimuli within each triad. The mean observing times for the various stimuli are shown in Table VI. An analysis of variance applied to the data indicated that the triad and TABLE VI MEANOBSERVING TIMEI N

SECONDS FOR THE INDIVIDUAL STIMULI 1963) (CANTOR, CANTOR, A N D DITRICHS,

Triads Complexity level Low Medium

High

I

I1

111

IV

V

VI

Overall

6.6 9.4 10.0

10.0

7.4 7.0 10.9

7.8 8.4 8.8

8.6 7.7 8.7

7.1 9.6 9.0

7.9 8.2 9.4

6.9 9.0

spatial arrangement variables did not contribute significantly to the variance. The complexity level main effect, however, was significant. There were no significant interactions. Comparisons of pairs of complexity levels indicated that the subjects spent significantly more time viewing the high- as opposed to the medium- and low-complexity stimuli. The difference between the latter two complexity levels was not significant. The authors made no attempt to quantify the complexity variable. Inspection of the figures indicates the possible relevance of amount of material, number of contour turns, and amount of contour as pertinent dimensions. 5 . Overview of the Child Research on Complexity Clearly, the methodological problems involved in devising objective observing response measures are more easily handled in child as compared with infant research. In all four of the studies reviewed in this section, the subjects made clear-cut instrumental responses which were readily counted and jot timed. There would appear to be some definite advantages in the use of preschool-aged subjects in research on stimulus selection behaviors, since

20

Responses to Complex and Novel Stimtllation such children share to some degree the infant’s lack of overlay of prior learning experiences but are nevertheless capable of engaging in instrumental behaviors amenable to highly reliable measurement. The available child studies are too few in number and too nonoverlapping in nature to permit more than the generalization that definite preferential, selective behaviors can be demonstrated in children (which should surprise nobody). It is to be hoped that future research will include replicative use of some of the stimulus presentation techniques and response measures developed to date. With regard to stimulus materials, there appears to be a serious need for intensive study of a few relatively simple and rigorously delimited stimulus properties which hopefully will supplant the vague notions of “complexity” which are currently prevalent.

IV. Studies of Stimulus Novelty A.

RELEVANTRESEARCH

Casual observation of “real life” behaviors provides numerous illustrations of the fact that novel stimulation will, at least at times, elicit attending and manipulative responses in infants and children. However, one can just as easily document the contentions that novel stimuli on occasion elicit avoidance responses and that familiar stimulation tends to be highly preferred. In view of the ubiquity of these types of phenomena and the relative ease with which they can be studied, it is surprising how little systematic investigation of the novelty-familiarity variable and its relation to infant or child behavior has occurred. The writer is aware of only four studies meeting or approaching the criteria for inclusion in this review. 1. Cantor and Cantor. Twenty black and white drawings,7 ranging from familiar geometric forms to complex and abstract shaded figures, were used in a study by Cantor and Cantor (in press) involving 66 kindergarten children as subjects. Ten of the stimuli comprised one set (A), the remaining figures making up a second set (B). During a familiarization phase, the subject was exposed via automatic strip film presentation to the stimuli in 1 of the 2 sets, half the subjects being given set A and half set B. The ten stimuli were projected, one at a time and for 6-sec intervals, in 5 different random sequences, for a total of 50 such presentations per subject. The subject was then taught to operate ‘These stimuli were taken from the Welsh Figure Preference Test (Welsh, 1959)

and were reproduced with the permission of the Consulting Psychologists Press.

21

Gordon N.Cantor a manipulandum which he used to project the same stimuli through 2 additional sequences ( 2 0 additional projections), with no restriction being placed on the amount of time each stimulus was exposed. The stimuli observed by the subject during this phase were then considered “familiar” for that subject. Following a 5-min rest, 36 of the subjects were given the opportunity to project the 10 “familiar” stimuli and the 10 “novel” stimuli (i,e., the figures not shown during the familiarization phase), each successive pair of stimuli in this testing sequence involving 1 “familiar” and 1 “novel” stimulus. An interval of 2 days separated the familiarization and testing phases for the remaining 30 subjects. Electric clocks were used to measure the amount of time the subject spent projecting (and presumably viewing) each of the stimuli during the 20 projections of the testing phase. Taking into account the counterbalancing variable (i.e., which stimulus set was familiar and which was novel for a given subject) and the delay between familiarization and testing ( 5 min or 2 days), the design may be considered as involving 4 subgroups. The major finding was that all four of the groups spent more time, on the average, projecting the novel as opposed to the familiar stimuli in the testing phase. An analysis of variance applied to the data indicated this was a significant effect. Plotting the means for the novel and familiar stimuli separately revealed that, for all 4 subgroups, the average amounts of time spent projecting the novel stimuli remained essentially stable throughout the testing sequence (“trials”), whereas the times for the familiar stimuli decreased. In the analysis of variance, this finding was reflected in a significant “trials” effect (shorter times in the later “trials”) and a significant “trials” x “novelty-familiarity” interaction. The subjects who were given the test phase 2 days after familiarization projected the stimuli as a whole significantly longer than the subjects given only a 5-min rest, but this variable did not interact significantly with the “novelty-familiarity” variable. That is, the 2 lengths of delay between familiarization and testing did not have a differential effect on the extent to which the subjects projected the novel as opposed to the familiar stimuli. In some unpublished findings, the authors retested 56 of the subjects approximately 4 months following the termination of the above described experiment and found no significant novelty effect. It may perhaps be argued that the first testing experience served to eliminate the difference in novelty in the 2 groups of stimuli. Another possibility is that the amount of familiarization used was too small to have an effect over a 4-month period.

2 . Mendel

One hundred and twenty 3-5-year-old children (divided equally into an experimental and a control group) served as subjects in a novelty study con-

22

Responses to Complex and Novel Stimulation ducted by Mendel (1962). Several copies of each of 16 different toys provided the stimulus materials, the 16 toys being split into 2 sets (A and E). The experimental subject was brought into a room containing 5 tables, one uncovered and the remaining 4 covered, arranged in a semicircle. For half the experimental subjects, the tables contained the following arrays of toys: (a) all 8 toys from set A (uncovered); (b) 6 toys from set A, 2 toys from set E; (c) 4 toys from both set A and set E; (d) 2 toys from set A, 6 toys from set E; and (e) all 8 toys from set E. For the remaining experimental subjects, the reversed arrangement held (i.e., the uncovered table contained all 8 toys from set E, etc.). Twenty different combinations of toys from sets A and E were employed on tables (b), (c), and (d), each of these combinations being used for 3 subjects. The 5 tables were rotated through the 5 spatial positions in the semicircle so that every table appeared in each position 12 times. Each experimental subject was given an 8-min play period with the toys on the uncovered table. After this “habituation” period, the remaining tables were uncovered, and the subject was led past all 5 toy arrays. He was then stationed equidistant from the various tables and told to select the one array of toys he most wanted to play with for an additional period of time. By virtue of the habituation experience, the 5 arrays, in the order listed above, were considered to represent o%, 25%, 50%, 75%, and 100% degrees of novelty for these experimental subjects. The control subjects were treated comparably, with the following exceptions: ( a ) all 5 tables were uncovered when the subject entered the situation; and (b) instead of being given an habituation play period, the subject was engaged in conversation by the experimenter for an 8-min period. Mendel’s report does not indicate the extent to which the subject may have been able to view the various toy arrays during this control phase. It was presumed that the 5 toy arrays did not differ in novelty for the control subjects at the time their choices were made. Table VII shows the major results.

FREQUENCIESOF CHOICEOF

THE

TABLE vrr VARIOUS TOY ARRAYSIN

THE

MENDELSTUDY

Per cent novelty Group

0%

25%

50%

75%

100%

Total

Experimental Control

3

9

11

15

5

14

16 6

21 20

60 60

As may be seen in Table VII, there was an increasing monotonic function relating degree of novelty and n d b e r of experimental subjects selecting the

23

Gordon N.Cantor various arrays. In contrast, the controls’ data formed a W-shaped function, with high points at O%, 50%, and 100% “novelty.” A preconception that the experimental subjects would tend to show the greatest preference for the arrays of intermediate novelty unfortunately led Mendel to perform analyses that do not entirely do justice to her data. Thus, a 2 x 3 chi-square table was assembled involving the 2 treatment groups and three levels of novelty (O%, 25 through 75%, and 100%). A significant chi-square was derived from this analysis, indicating that the 2 groups did not select from the three novelty categories in comparable fashion. Using a partitioning technique, 2 x 2 chi-squares were run involving the treatment variable and the following novelty comparisons: (a) 0% vs. 25-75s; (b) 100% vs. 0-75%; (c) 100% vs. 25-75%; and ( d ) 0% VS. 25--100%. Of the 4 resulting chi-squares, only the first and last were significant. It was concluded from these findings that the experimental subjects showed a greater tendency to avoid the 0% novelty array than did the control subjects, and that this difference was the major contributor to the significant findings. Under the assumption that the control subjects should have been expected to select indifferently from the 5 toy arrays (i.e., should have made 1 2 choices of each array), a chi-square was applied to the 5 control group frequencies, testing the hypothesis of no significant departure from such a rectangular distribution. This hypothesis had to be rejected. Mendel examined such variables as position preferences, individual toy preferences, and sex and age of the subjects, and was unable to conclude that any one of these factors could be used to explain the peculiar pattern of choices exhibited by the control group. In view of the inexplicable nature of the findings for the control subjects, one is led to wonder about the meaningfulness of the experimental-control comparison. The results for the experimental group could also be evaluated through the use of a chi-square analysis comparing the obtained frequency at each of the 5 novelty levels with the theoretically expected frequency of 1 2 (as was done with the control group data). In view of the straight-line function suggested by the data, a significant chi-square obtained from such an analysis would tend to indicate the existence of a significant positive relationship between degree of novelty and frequency of choice. The writer computed this chi-square and found it to be significant ( P < .Ol). The data certainly provide no basis for concluding that a preference for intermediate degrees of novelty was evidenced in the selections of the experimental group. In this connection, a published statement about the Mendel results by Maddi (in Fiske and Maddi, 1961, p. 262) to the effect that, ‘*. . . the intermediate degrees of novelty were most effective in eliciting choice or investigatory responses,” appears unwarranted. The general approach utilized by Mendel in manipulating the novelty

24

Responses to Complex and Novel Stimulation variable would appear to be highly useful. Repetitions of the study are in order to determine if the increasing function for the experimental group can be replicated and to shed some light on the unusual pattern of responses made by the control group. 3. Spit2 and Hoats In a companion experiment to the complexity study discussed in Section 111, B, 1, Spitz and Hoats (1961, Experiment $ 2 ) selected 20 stimuli from those used in the complexity research. The stimuli, drawn from all but the incongruity and incongruous juxtaposition classes, were combined into 10 pairs, only 3 of which duplicated particular pairings appearing in the first study. With one exception, all the stimuli were symmetrical in nature. A “critical” pair, consisting of a symmetrical clover-leaf figure and an irregular random shape, was drawn from the irregularity-of-shape class and was one of the 3 pairs which did appear in the complexity study. In some pilot work, 26 of the 30 retardates run in the first experiment served as subjects again. All 26 of these individuals had chosen to reproduce the symmetrical member of the “critical” pair in the complexity study. This time, the subjects were given the same instructions as before and were then presented the 10 pairs of stimuli, one at a time. Fourteen of the subjects received the critical pair last in the series, whereas this pair appeared fifth in the sequence for the remaining 1 2 subjects. Each of the latter 1 2 subjects again chose to reproduce the symmetrical member of the critical pair, but 5 (35.7%) of the 14 subjects given the critical pair last in the series chose the asymmetrical member. Spitz and Hoats attributed this result to a novelty effect, i.e., the appearance of an asymmetrical stimulus following exposure to nine pairs of symmetrical stimuli constituting a novel event which altered the choice behavior of some of the subjects with respect to the members of the critical pair. Twenty-eight naive retarded subjects, matched for CA, sex, and IQ with the 30 retarded subjects contributing data to the complexity experiment, were then run in the main part of the novelty study. Only the sequence in which the critical stimulus pair appeared last was used. The positions of the stimuli within each pair were counterbalanced, 14 of the subjects receiving a given pair in one spatial arrangement and 14 being given that pair in the reversed arrangement. The two counterbalancing groups did not differ significantly in their tendency to choose the asymmetrical member of the critical pair, so the data from these groups were combined. Ten of the 28 subjects run in this experiment chose to reproduce the asymmetrical stimulus in the critical pair; this was the case for only 3 of the 30 subjects run in the complexity study. A chi-square applied to these

25

Gordon N.Cantor frequencies indicated a significant difference ( P < .05) in the proportion choosing the asymmetrical stimulus. Since a majority of the subjects chose the symmetrical stimulus in the critical pair in both the pilot study and the main experiment, the “novelty” effect cannot be regarded as having been very potent. Nevertheless, the data are suggestive and worthy of being followed up. It is unfortunate that the 30 retardates from the complexity experiment served as a comparison group in the evaluation of the results of the main part of the novelty study. A group exposed to 10 pairs of symmetrical stimuli (with only the tenth pair differing for the 2 groups) would have provided a considerably more appropriate control treatment. It is interesting to note that “familiarity” in this study was generated with respect to a class of stimuli (i.e., symmetrical figures) rather than to certain individual stimuli. 4. Smock and Holt In the study by Smock and Holt (1962) discussed in Section 111, B, 2, an additional task was included which the authors labeled “preference for the unknown.” Each of the 44 subjects ranked 25 toys in order of preference. The subject was then given a choice between 2 boxes containing different toys on each of 7 trials. On a given trial, the subject was allowed to observe the experimenter hide a (“known”) toy under one box, but he was not allowed to see a second (“unknown”) toy being hidden under a second, identical box. The subject was then presented with the 2 boxes and told to choose the box containing the toy he most wanted to play with following the experiment. For the first 4 trials, both toys were of medium preference value; on trials 5 and 6, the known toy was of high and the unknown toy of low preference value; on the final trial, both toys were of high value. The authors report that the mean number of choices of the unknown toys was 4.37, a mean of 3.5 being expected by chance. N o test of the difference between the obtained and hypothesized means was reported. Instead, a test was made of the difference between the “obtained” proportion (63%) and the “expected” proportion (50%) of choices of the unknown toys. The resulting critical ratio of 4.56 ( P < .Ol) led the authors to conclude that the subjects showed a significant preference for choosing the unknown toys. However, this statistical test was inappropriate, since the obtained proportion was not based on 308 independent observations but rather on a total of 7 observations for each of 44 subjects. Consequently, the outcome of this phase of the experiment cannot be assessed. The purpose of including the preference rankings was not indicated nor was the effect of this variable on the subjects’ choices mentioned. Furthermore, the possible effect of the preference values on the “expected” proportion of choices of the unknown toys was not considered.

26

Responses to Complex and Novel Stimulation Although the results of the “preference for the unknown” test remain indeterminate, the technique used is an interesting one. Perhaps the term “uncertainty” would be more appropriate than “novelty” in referring to the character of the “unknown” stimuli in this experiment. Clearly, the experimental manipulation used differs from that employed in each of the studies previously reviewed in this section.

B.

OVERVIEW OF

THE

NOVELTY RESEARCHAND RELATEDSTUDIES

As in the case of the complexity research, the work on children’s responses to novelty has had only a bare beginning; the writer is unaware of the existence of any studies done to date on infant subjects. The evidence that is available on children, however, suggests rather clearly that a preference for novel as opposed to familiar stimuli can, under certain circumstances, be demonstrated. The experimental paradigm used in 3 of the 4 studies reviewed, i.e., the employment of a familiarization procedure followed by a choice situation involving “familiarized” and “unfamiliarized” stimuli, points up the likely role played by an inhibitory process operating with reference to familiar stimuli. Parametric studies manipulating amount of familiarization experience would appear to comprise one fruitful line of attack; in this connection, the pilot phase of the Spitz-Hoats study suggests the relevance of the amount of familiarization variable. Similarly, studies varying the time interval between familiarization and testing, as in the study by Cantor and Cantor, would seem to be in order. The negative results obtained by these investigators with respect to this variable indicate the advisability of using a larger number of delay values. Berlyne’s various definitions of novelty suggest additional lines of investigation. The utility of his concept of “relative” novelty, for example, could be assessed by familiarizing subjects with a group of stimuli and then testing for the comparative interest value of “new” stimuli which are generated by means of different degrees of reorganization of the components contained in the original stimuli. The concepts of “long-term” and “short-term” novelty suggest an experimental paradigm in which subjects are exposed to one group of stimuli, are later exposed to a second group, and are then tested for preferences between the two groups, the temporal interval between the exposures being of varying lengths for different subjects. It should be noted that, in the studies which have used a familiarization procedure, the “novel” stimuli may be regarded as having long-term novelty, the familiar stimuli being characterized by short-term novelty. Although falling outside the scope of this review, studies of discrimination

27

Gordon N.Cantor learning in which analyses reveal subjects’ tendencies to respond to untried, newly introduced, or constantly changing stimuli should be mentioned as bearing considerable relevance to this general problem area. Examples of such research using children as subjects may be found in reports by House et al. (1957), House and Zeaman (1958), EIlis et d l . (1962), and S. H. White (1962).

V. Conclusions Recent publications dealing with stimulus selection behaviors (e.g., Berlyne, 1960; Fiske and Maddi, 1961) make it apparent that a large literature is accumulating in this area. Unfortunately, studies on human infants and on children constitute but a small fraction of the available research. Among chiId psychologists who have shown an interest in the topic, a concern with an individual difference variable of “curiosity” appears in several instances to have played a rather predominant role in determining their choices of the kinds of data to gather. The result in such cases has been a relative lack of emphasis on the stimulus variables involved, as, for example, in the studies by Spitt and Hoats (1961), and Smock and Holt (1962) discussed in the present review. Even clearer instances of this kind of approach may be found in studies which compare various behaviors of children receiving high and low “curiosity” scores, via peer, teacher, or self-ratings, or through the administration of “tests” of curiosity, as, for example, in McReynoIds et a/. (1961) and Maw and Maw (1962). The search for such R-R laws relating individual differences in “curiosity” to stimulus selection constitutes a perfectly legitimate scientific enterprise. From the standpoint of motivational theory, however, this approach has tended to be accompanied by certain terminological usages which suggest the operation of special purpose motives-for example, the occurrence of such notions as “curiosity as an acquired drive” (Spitt and Hoats, 1961, p. 17), “inherent tendencies to seek novel percepts” (McReynolds et al., 1961, p. 394), “curiosity motivation” (Smock and Holt, 1962, p. 631), and “the basic desire to know” (Maw and Maw, 1962, p. 917). While such ideas as these wouId certainly be compatible with the t h i d i n g of several motivational theorists (see Section I), it could hardly be argued that the concepts or suggested relationships involved are uncontroversial in nature. The theoretical questions at issue here are important, indeed; but little or nothing is to be gained, in this reviewer’s opinion, by the use of motivation-like concepts to refer to phenomena which at the present time can be discussed as appropriately in associative as in motivational terms. A frontal attack on this problem would seem to require the use of independent criteria for detecting the presence of motivation-like

Responses t o Complex and Novel Stimulation states in organisms exposed to stimuli high in the so-called “collative” properties (see Section 11, A ) . The use of various autonomic measures would perhaps constitute one such possibility. However, before the motivation issue can be effectively handled, a prior need exists for verification of the assumption that infants and children are in fact attracted by stimuli high in these “collative” properties. The studies reviewed in this paper are suggestive, at best, and one of them (Spitz and Hoats, 1961) provides evidence which is negative in nature. Above all else, there exists an imperative need for objective stipulation of stimulus properties, for unbiased stimulus presentation techniques, and for clearly delineated indices of stimulus selection behaviors. In general, the studies reviewed here offer promising leads in the latter two respects. But, excepting the novelty research and the work on complexity by Spears (1962) and May (1962), the stipulations of stimulus properties leave much to be desired. As previously observed, psychological rather than physical scaling may provide the ultimate answer to this problem, at least with respect to some of the “collative” variables such as complexity and novelty; indeed, there are strong advocates of such a position (see, e.g., Dember and Earl, 1957). But attempts to index these variables through physical measurement techniques have scarcely been tried in infant or child research; it remains to be demonstrated that such an approach is without utility.

REFERENCES Attneave, F. Some informational aspects of visual perception. Psychol. Rev., 1954, 61, 183-193. Attneave, F. Physical determinants of the judged complexity of shapes. J. exp. Psyrhol., 1957, 53, 221-227. Berlyne, D. E. The influence of the albedo and complexity of stimuli on visual fixation in the human infant. Brit. J , Psychd., 1958a, 49, 315-318. Berlyne, D. E. The influence of complexity and novelty in visual figures on orienting responses. J. exp. Psychol., 1958b, 55, 289-296. Berlyne, D . E. Conflict, arousal, and curiosity. New York: McGraw-Hill, 1960. Birkhoff, G. D . Aesthetic measure. Cambridge: Harvard University Press, 1933. Brown, J. S. The motivation of behavior. New York: McGraw-Hill, 1960. Cantor, G . N., Cantor, J. H., & Ditrichs, R. Observing behavior in preschool children as a function of stimulus complexity. Child Develpm., 1963, 34, 683-689. Cantor, J. H., & Cantor, G. N. Observing behavior in children as a function of stimulus novelty. Child Develpm., in press. Dember, W. N., & Earl, R. W. Analysis of exploratory, manipulatory, and curiosity behaviors. Psychol. Rev., 1957, 64, 91-96. Earl, R. W. Problem solving and motor skill behaviors under conditions of free choice. Unpublished doctoral thesis, Univer. of Michigan, 1957.

Gordon N.Cantor Ellis, N. R., Girardeau, F. L., & Pryer, M. W. Analysis of learning sets in normal and severely defective humans. J . romp. physiol. Psychol., 1962, 55, 86C-865. Fantz, R. L. Pattern vision in young infants. Psychol. Rec., 1958, 8, 43-47. Fantz, R. L. Visual discrimination in a neonate chimpanzee. Percept. mot. Skills, 1958b, 8, 59-66. Fantz, R. L. The origin of form perception. Scient. Amer., 1961, 204,No. 5, 66-72. Fiske, D. W., & Maddi, S. R. Functions of varied experience. Homewood, Illinois: Dorsey, 1961. House, B. J., Orlando, R., & Zeaman, D. Role of positive and negative cues in the discrimination learning of mental defectives. Percept. mot. Skills, 1957, 7 , 73-19. House, B. J., & Zeaman, D. Reward and nonreward in the discrimination learning of imbeciles. J . romp. physiol. Psychol., 1958, 51, 614-618. Hunt, J. McV. Experience and the development of motivation: Some reinterpretations. Child Develpm., 1960, 31, 489-504. Lindquist, E. P. Design and analysis of experiments in psychology and education. New York: Houghton Mifflin, 1953. McReynolds, P., Acker, M., & Pietila, C. Relation of object curiosity to psychological adjustment in children. Child Develpm., 1961, 32, 393-400. Maw, W. H., & Maw, E. W. Selection of unbalanced and unusual designs by children high in curiosity. Child Develpm., 1962, 33,917-922. May, R. B. Stimulus selection in preschool children under conditions of free choice. Unpublished paper, Claremont Univer. College, Claremont Cal., 1962. Mendel, G. Choice of play objects as a function of their degree of novelty. Unpublished doctoral dissertation, Univer. of Chicago, 1962. Morgan, C. T. Physiological mechanisms of motivation. In M. R. Jones (Ed.), Nebraska rymposium on motivation. Vol. V, 1-35. Lincoln, Nebraska: Univer. of Nebraska Press, 1957. Mowrer, 0. H. Learning theory and behavior. New York: Wiley, 1960. Rheingold, H. L., Stanley, W. C., & Cooley, J. A. Method for studying exploratory behavior in infants. Science, 1962, 138,No. 3521, 1054-1055. Smock, C. D., & Holt, B. G. Children’s reactions to novelty: an experimental study of “curiosity motivation.” Child Develpm., 1962, 33,631-642. Spears, W. C. The assessment of visual discrimination and preferences in the human infant. Unpublished doctoral thesis, Brown Univer., 1962. Spitz, H. H., & Hoats, D. L. Experiments on perceptual curiosiiy behavior in mental retardates. Final report, NIMH Grant M-4533, Johnstone Training and Research Center, 1961. Welsh, G. S. W e l s h Figure Preference Test (Research Edition). Palo Alto: Consulting Psychologists Press, 1959. White, R. W. Motivation reconsidered: The concept of competence. Psychol. Rev., 1959, 68, 291-333. White, S. H. Research on attenfional processes in learning. Progress report, NIMH Grant M-3639, Univer. of Chicago, 1962. Woodworth, R. S. Dynamics of behavior. New York: Holt, 1958.

30

WORD ASSOCIATIONS AND CHILDREN'S VERBAL BEHAVIOR'

David S . Palermo PENNSYLVANIA STATE UNIVERSITY*

I . HISTORICAL INTEREST IN CHILDREN'S WORD ASSOCIATIONS . . A . EARLY GERMAN STUDIES . . . . . . . . . . . . B. FIRST ENGLISH STUDIES . . . . . . . . . . . . C. WOODROW AND LOWELL STUDY . . . . . . . . . D . STUDIES SINCE WOODROW AND LOWELL . . . . . . I1. RECENT USES OF WORD ASSOCIATIONS . . . . . . . . . A . STUDIES OF ADULT VERBAL BEHAVIOR . . . . . . . B. STUDIES OF CHILDREN'S LANGUAGE . . . . . . . . C. EXPERIMENTAL MANIPULATION OF ASSOCIATIONS . . . 111. A NORMATIVE STUDY OF WORD ASSOCIATIONS

IV

.

A . RATIONALE . . . . . . . . . . B. THE LIST OF WORDS . . . . . . . C PROCEDURE . . . . . . . . . . D SUBJECTS . . . . . . . . . . . E. RESULTS . . . . . . . . . . . F RESPONSE CLASSIFICATIONS . . . . . EXPERIMENTAL USES OF THE NORMATIVE DATA A PAIRED-ASSOCIATE LEARNING . . . . B. ASSOCIATIVE CLUSTERING IN RECALL . C. ASSOCIATIVE GENERALIZATION . . . D FUTURE RESEARCH . . . . . . . . REFERENCES . . . . . . . . . . . .

. . . .

.

32 32 33 34 35

37 37 38 39

. . . . . . . . . . . . .

.

.

.

.

40 40 40

.

. . . . . . .

.

.

.

.

.

. . . . . .

. . . . . . .

.

.

.

.

.

40 41 42 50

. . . . . .

57 58 61

. . . . .

63

. . . . . .

. . . . . . 64 . . . . . . 65

'This chapter and the research reported in the latter part of the chapter were supported by research Grant MH-04286 from the National Institute of Mental Health, Public Health Service and Grant GB 233 from the National Science Foundation The author is indebted to James J. Jenkins for his research collaboration and critical reading of this manuscript. 'This chapter was written while the author was a member of the staff at the Institute of Child Development, University of Minnesota.

.

31

I. Historical Interest in Children’s Word Associations Interest in word associations derives rather directly from a long history of interest in the higher metal processes of man. The relation to the psychology of British Associationism is obvious, but the main impetus for the study of the associative characteristics of words came from the clinical psychologist who has attempted to use the word association test as a tool for the diagnosis and understanding of the areas of sensitivity related to the symptoms of his patients. Interest in the clinical significance of the content and reaction time of words given in response to a word association test preceded by a considerable amount of time the determination of the characteristics of responses obtained from a normal population. In 1910, however, Kent and Rosanoff reported the associative responses of 1000 persons, primarily adults, to a list of 100 words. The normative data obtained by Kent and Rosanoff provided a basis of comparison for use by the clinician and began a long series of studies with that particular list of words which has been useful in the clinical setting and, more recently, has proved valuable in other areas.

A. EARLYGERMAN STUDIES Although a number of studies investigating children’s word associations followed the publication of the Kent-Rosanoff norms, interest in word associations of children dates back to 1898 when Ziehen, according to Rusk (1910) and Woodrow and Lowell (1916)) reported on the oral responses of 45 boys between the ages of 8 and 14 to a list of words presented orally. Ziehen concluded that children tend to think in terms of concrete representations in contrast to the general ideas of adults. Somewhat later, Meumann (1905), the first to use the group administration method with children, presented words orally and obtained written responses from over 800 children in their classrooms. He examined the differences between children of high and low intelligence and concluded that the associations of less intelligent children were inadequate because there were more misinterpretations of the stimulus words, omissions of responses, senseless responses and perseverative responses. Fiirst (1918) obtained word associations from mothers, fathers and their children. She found that children tend to differ less with their parents than among themselves and that the responses of children tend to resemble those of their mothers more than those of their fathers. Woodrow and Lowell review the work of a number of the other early German investigators who have reported on the word associations of various groups of children (Wintler,

32

Children’s Verbal Behavior 1906; Wreschner, 1907; Saling, 1908; Reinhold, 1910; Goett, 1911; and Wimmer, 1909).

B. FIRSTENGLISHSTUDIES Rusk (1910) was the first to report upon the associations of English speaking children. H e tested 22 boys between the ages of 7 and 14 using visual presentation and oral response to eleven different free and constrained association tests of ten words each. He found no relation between speed of association and age, but he did infer that associations to some kinds of words varied in difficulty on the basis of the relationship between speed of reaction and the type of responses required. It was easier to respond to concrete words than to abstract words in a free association test, and practice resulted in more improvement with the concrete words than with the abstract words. He found constrained associations, where particular kinds of responses such as superordinates or coordinates were required, were more difficult than free associations. Work in this country began as a direct result of the publication of the adult frequency tables by Kent and Rosanoff (1910). Eastman and Rosanoff (1912) examined the associations of mentally retarded and delinquent children between the ages of 11 and 17. They found that the responses of this group to the Kent-Rosanoff list revealed more failures to respond, repetitions of the stimulus word, and idiosyncratic responses but fewer popular responses than the normal adult population reported by Kent and Rosanoff. The authors suggest that lack of language skills is, at least in part, a factor in the results because the words of lower frequency of usage yielded the greatest failure of response. The results of a small group of normal children indicated that the children under eight responded in a manner similar to the older retarded group while the children over ten years of age responded as do adults. Otis (1915) confirmed the results of Eastman and Rosanoff. She found that retarded children are slower and more variable in their responses, tend to repeat the stimulus, give nonlogical responses and give phrase responses more frequently but show a steady rise in normal responses with mental age. The developmental trends in the classes of responses given by the retarded children were similar in many respects to those of normal children when the children were matched on the basis of mental age. The results obtained from the group of normal children in the Eastman and Rosanoff study led to the publication by Rosanoff and Rosanoff (1913) of a more extensive set of normative data for a group of 300 normal children, 25 at each age, 4 through 15. The list was presented orally and responses were obtained orally. They found that less than 50% of the responses given by the youngest children were found in the adult norms and the average 4-year-old

33

David S. Palermo failed to respond to nearly 30% of the stimulus words. The charasteristics of the responses obtained from the children, however, rapidly changed to resemble those obtained from adults and by the age of 11 the percentages of common responses, idiosyncratic responses and failure of reaction were about the same as those found ln the adult norms. The age trends found in these data were also obtained when the children were grouped as “dull,” “average,” or “bright” according to teachers’ ratings. The results of this study were replicated in a sample of 300 Negro children reported by Mitchell et al., (1919). The same general age trends were observed in the normative data obtained from this group of children when compared with the white children except the Negro children were somewhat older when they reached the same levels of performance.

C. WOODROW AND LOWELLSTUDY The largest single study of children, however, was reported by Woodrow and Lowell in 1916. This study gives a complete listing of the responses of 1000 fourth and fifth grade children in the Minneapolis Public Schools to each of 90 Kent-Rosanoff words plus an additional 10 words substituted for 10 of the Kent-Rosanoff words considered too difficult for this age gr0up.S The words were presented orally to children in their classrooms and the children responded by writing their association on blanks provided by the experimenters. Oral responses to orally presented stimuli were also obtained from 1000 children to the first nine words in the list in order to determine whether the method of response, oral or written, made a difference in the responses obtained. The latter procedure was followed to be sure that comparisons with the adult norms collected by Kent and Rosanoff would not be biased by the manner in which the data were collected. The results of this study suggest that there are large differences between the word associations of adults and those of children. Differences occurred in both frequency counts and in content of the associations obtained. In contrast to adults, children tend to give fewer contrast, superordinate, coordinate, part-whole, noun-abstract attribute, participles and cause-effect responses and more verbs, verb-object, noun-adjective, adjective-noun, pronouns, sound similarity, contiguity, and whole-part responses. Although frequency of the most popular responses was found to be about the same for the children and adults, only in the case of 39% of the words was the actual first response the same for the two groups and only in the case of five words were the first three responses the same for the two groups. Children, however, were found to give

’

The words eliminated from the Kent-Rosanoff list included mlttton, comfort, command, citizen, trouble, justice, health, memory, religion, and bitter. These were replaced with fun, school, candy, stark, garden, pug, laugh, milk, ghost, and friend.

34

Children’s Verbal Behavior fewer respons with a frequency of one and fewer different responses to any particular stimulus word. The responses given by the children were generally found in the adult norms but the reverse was much less likely to be the case. Little difference was found among the age groups included in the two grades. Differences in the characteristics of the responses obtained orally and those obtained in written form were interpreted as of minor consequence by the authors. These data are particularly interesting because of the site of the sample, the completeness of the report and the similarity of this research to that which will be reported later in this chapter. Many authors interested in the characteristics of the word associations of children have relied heavily upon the results of the Woodrow and Lowell study. As will be demonstrated, some of the results obtained in that study are not replicable with present day children at the same educational level. a s

D. STUDIESSINCE WOODROW AND LOWELL Since the Woodrow and Lowell study, the literature dealing with children’s word associations has been rather limited and the objectives of the studies reported have been rather diverse. In 1928 Elonen and Woodrow developed a scoring system for pathological responses based upon characteristics of individual idiosyncratic responses to the Woodrow and Lowell list and found it to be reliable and to correlate .57 with teacher ratings of normality. Correlations of the average frequency of an individual’s responses, according to the Woodrow and Lowell norms, with the number of the three most popular responses given on the test was .93 and with the number of idiosyncratic responses given was -.63. None of these measures, however, correlated with psychopathic tendencies of the children. McElwee (1931), McFadden (1931) and more recently Horan (1956) have provided additional data relevant to the associations given by mentally retarded children to the Kent-Rosanoff list. McElwee found that his subjects gave more phrase responses, more idiosyncratic responses and fewer common responses than a group of children with normal intelligence. McFadden tested 103 normal and 105 retarded children all of whom had mental ages between 6 and 9. Disregarding phrase and failures of response, the normal and retarded children gave similar kinds of responses when the same mental age groups were compared. The retarded children, however, took slightly less time to complete the test, gave more phrase responses and fewer failures to respond than the normal children. Horan reports that the retarded children in his sample gave responses more similar to those of the adults in the KentRosanoff sample than to the children of the Woodrow and Lowell sample.

3s

David S. Palermo He suggests that one reason for the more mature responses obtained may be the greater amount of experience with language brought about by radio, television, and movies which are available to the child today. Two studies have been concerned with the use of the word association technique in relation to educational problems. Shambaugh and Shambaugh (1928) used the method for determining the most frequently used words of children in grades four through eight. They do not report the associative data of their sample, but they indicate that the most common responses of the lower grades tend to be included in the responses of the children in the higher grades. Many of the most frequently used words, however, were not included in Thorndike’s list of the most common words (1921) nor in Horn’s list of most frequently used words (1926). Traxler (1934) developed a free association test and an association test of antonyms for purposes of determining the relation of speed of associative responding to speed of reading. The correlations obtained ranged from .24 to .48. McGehee (1937) was also interested in speed of associative responses in children. In a sample of children between the ages of 7 and 10 he found no developmental trends in reaction time to 5 5 words selected as familiar and personal. Boys were faster to respond than girls and popular responses were given more rapidly than less popular responses, particularly by girls. No marked differences were found in the content of the responses of the age groups but the boys tended to give slightly greater numbers of the popular responses, the frequency of the popular responses tended to go up with age and failure of response tended to go down with age (McGehee, 1938). Carter (1938) also found little relation between age and speed of responding in a study of the responses of 50 sets of twins 9 to 17 years of age. He does report slower responses to unpleasant words and faster responses on the part of brighter children. Twin resemblances in time scores were low although the relationship was greater for identical twins ( Y = .38) than for fraternal twins (Y = 21). I n connection with the Terman studies of genius, Wyman (1926) developed a multiple-choice form of an association test which was used to evaluate intellectual, social, and activity interests of that population. The general form of the test was later extended by Terman and Miles (1936) for use in their studies of masculinity and femininity. Goodenough (1942) developed a homograph test which was also used as a measure of mascuIinity and femininity. One other extensive normative study, done by Wheat (1931), analyzed the characteristics of the responses of 1323 children in grades four through eight to 25 words selected at random from the Thorndike list of the 500 most frequently used words (1921). H e found that common responses, those with a frequency of at least 10 in a population of 1000, increased with age to a peak at age 11, after which there was no further increase. Downward trends of the uncommon responses and failure of response also leveled off at age 11. These

36

Children’s Verbal Behavior results conform quite closely to those obtained by Rosanoff and Rosanoff (1913). Reliabilities obtained by Wheat over a one week test-retest interval were .69 for common responses and .74 for failure of response while correlations of his various measures of association with intelligence clustered about zero. The frequency of common responses to noun stimuli tended to be higher, while failure of response and uncommon responses tended to be lower in comparison to other parts of speech. In summary, other than the developmental trends which consistently appeared in the common responses, uncommon responses and failure of response categories, the results of these early studies did not prove to be as enlightening as had been anticipated when Kent and Rosanoff first published their norms. The gross analyses of content, frequency and reaction time all proved to be less than satisfactory for the purposes for which they were designed. Until very recently, in the studies which will be discussed below, the interest in word associations of children has received very little research attention, although the clinical interest in the word associations of adults has continued throughout the years to the present time (e.g., Milgram, 1961; Moran et al., 1960).

11. Recent Uses of Word Associations A. STUDIESOF ADULTVERBALBEHAVIOR During the past few years the use of the word association frequency tables has spread to the laboratory of the psychologist interested in verbal learning and verbal behavior where there is evidence that such normative data may prove to be a much more valuable tool for the understanding of language and its functions than has been the case in other areas. In 1954 Russell and Jenkins made available The Complete Minnesota Norms for Responses to 100 words from the Kent-Rosanoff Word Association Test based upon the responses of 1008 college students. The publication of these norms led to much research dealing with a wide variety of verbal learning and verbal behavior problems with adults using the known natural language associates found in the norms. Many investigators working in the verbal area have found that the norms make possible experimental work which otherwise would have entailed extensive preexperimental preparation of materials on large samples of subjects. As a result of the many studies since the norms have been available, there now exists a substantial body of experimental data showing the important role played by simple associative processes in recall (e.g., Jenkins et al., 1958; Deese, 1959; Bousfield, et al., 1960), transfer (e.g., Ryan, 1960; Bastian, 1961; Cramer & Cofer, 1960), mediated generalization (e.g., Russell & Storms, 1955; Cofer & Yarczower, 1957; McGehee & Schultz, 1961; Jarrett & Scheibe, 1963), associative generalization (e.g., Martin, 1960; Mink, 1963), and perception (e.g.,

37

David S. Palermo O’Neil, 1953; Rouse & Verinis, 1963). These studies have materially advanced our understanding of verbal behavior in adults.

B. STUDIESOF CHILDREN’S LANGUAGE Even more recently, psycholinguists have found that characteristics of the word associations of children are related to aspects of the language skills of those children. Ervin (1961) obtained free and constrained associations from children in kindergarten, first, third, and sixth grades and found an increase with age in the proportion of responses in the same grammatical form class as the stimulus word. She further analyzed the responses to her stimulus list in relation to the frequency with which the stimulus words occurred in an early or final position in a sequential analysis of sentences in children’s books, and the transitional probabilities of different grammatical classes of words in such contexts. Her analyses revealed that words which characteristically appear in a medial position in a sentence are less likely to yield a word association response in the same form class than words which are more frequently found in a final sentence position. Further, an analysis of the responses in the word association test which were in a different form class than the stimulus word revealed a correlation of .87 between the transitional probabilities of the two form classes in the word association test and the transitional probabilities in textual materials when the function-words and connective words were eliminated. Brown and Berko (1960) have also shown a relationship between word associations of children and aspects of the development of grammar, In this study a word association test composed of 6 words from each of 6 grammatical classes and a Usage Test involving each of the 6 parts of speech were employed. The latter test involved the use of a pronounceable nonsense syllable in two sentence frames which implied its part of speech, following which the subject used the word in a sentence of his own creation. Sentences were scored as correct if the nonsense word was used in a way appropriate to the part-of-speech. First, second, and third grade children and a group of adults served as subjects. As reported by Ervin, there was an increase with age in the frequency with which responses on the word association test were in the same grammatical form class as the stimulus word. The results of the Usage Test revealed a positive correlation between age and correct usage of the nonsense words in accordance with the part-of-speech. Of greater consequence here was the strong relationship between the amount of same form class responding to the various parts of speech on the word association test and the correct usage of that form class in the Usage Test. Thus, the linguistic skills associated with the correct perception and use of a part of speech were found to be highly correlated with a

38

Children’s Verbal Behavior greater frequency of same form class responding to that part of speech in free association. Taken together, these two studies give strong support to the hypothesis that analyses of responses to a word association test may prove quite useful to the understanding of the acquisition of language in young children. Considering the usefulness of word association norms in the study of verbal learning problems with adults and the findings with respect to language acquisition of children, there would appear to be a need for a comprehensive up-to-date set of word association norms over a wide age range from young children through the adult leveI. Such a set of norms would broaden the scope of the norms available at the college level and would be of considerable use at the present time in examining questions relating to the development of language functions, language habits and the change in associative habits in this country over time. In addition, and equally important, such norms would provide the essential raw data for experimental work on the role of language habits in important behaviors such as recall, learning, perception, and generalization of children and young adults.

c. EXPERIMENTAL MANIPULATION OF ASSOCIATIONS The obvious usefulness of the normative data to the study of these phenomena of verbal learning and behavior would not, of course, obviate the need for experimental manipulation of associative variables in the laboratory. In fact, the child is a particularly appropriate subject for such studies because of his relative lack of verbal experience. The tremendously intricate verbal skills which are possessed by the college sophomore makes it extremely difficult to understand what he may be doing in any particular experiment. The use of children in such experiments may provide a greater chance of pulling apart some of the relevant variables before they become as intertwined as is the case with adults. Studies such as those of Eismann (1955), Norcross and Spiker (1958), Spiker (1960), and Palermo (1961; 1962) in which the verbal associative connections are established within the experimental task must form the foundation of any theoretical analysis which may be developed to account for verbal learning and verbal behavior of children. In addition, the studies of the function of language in discrimination learning (e.g., Norcross, 1958; Kendler et al., 1960), generalization (e.g., Shepard, 1956; Bialer, 1961), concept formation (e.g., Dietze, 1955; Carey and Goss, 1957) and delayed reaction (e.g., Spiker, 1956) in which the labeling or language variable has been experimentally introduced independently of the pre-existing language system of the child have formed an impressive contribution to our understanding of verbal mechanisms and have contributed substantially to theories of verbal behavior and language

39

David 3. Palermo

111. A Normative Study of Word Associations A. RATIONALE Despite the importance of the type of experimental control in the study of language acquisition and function illustrated in the studies mentioned in the preceding section, the value of normative data on the natural language associations of children seemed so potentially useful in such a variety of experimental areas as a tool for research that the present writer in collaboration with Jenkins set out in 1960 to collect normative word association data from subjects in the fourth grade through college (Palermo and Jenkins, 1963). Reassuring evidence of the usefulness of such norms with children became apparent with the publication by Castaneda et al. (1961) of a set of norms for 63 common adjectives4 and the subsequent use of these norms in studies of paired-associate learning and mediation (McCullers, 1961; 1963).

B. THELIST OF WORDS A list of 200 stimulus words was developed for use in the present study. The list included the 100 words in the Kent-Rosanoff list plus 100 additional stimulus words. The Kent-Rosanoff words were used to allow comparisons with older data where appropriate. Since the Kent-Rosanoff list consists primarily of singular nouns and simple adjectives, it was decided to add 100 additional words of other form classes to broaden the norm base and allow greater flexibility in future research based upon these norms. The second list systematically sampled verbs, pronouns, adverbs, etc., which occur at reIatively high frequency levels in the speech and writing of children and young adults. All words in their root form were A or AA on the general count in the ThorndikeLorge list (1944) except kittens which occurs 35 times in a million according to the count. Thus, included in the second 100 words were 10 plural nouns, 10 transitive verbs, 10 intransitive verbs, 3 forms of the verb “to be,” 3 participles, 6 conjunctions, 2 interjections, 10 prepositions, 14 pronouns, 17 adverbs, and 15 additional adjectives, 9 of which are comparative and 3 of which are articles.

C. PROCEDURE Since all of the tests were to be administered in written form, it was necessary to determine how young a group of children could be used. It was ‘Additional associative data on these adjectives plus 176 others have been collected by Castaneda but have not yet been published.

Children’s Verbal Behavior felt that children in the fourth grade were probably as young as could be used. Accordingly, a pilot study was conducted to test the limits by administration of the test to two elementary schools which drew from low socioeconomic level families. It was found that the children in grades four and five of these schools did not have sufficient reading and writing skills to provide usable data. Out of a class of 25 or 30 pupils, typically, only about five scorable sheets were obtained. Thus, it was necessary to limit the sample to children drawn from middle and upper socioeconomic level schools in the lower grades. It was considered desirable to administer the tests in a manner as similar as possible to the one employed in previous studies with adults. Therefore, the instructions were taken from the previous study of Russell and Jenkins (1954) with some additional elaborations to make them clear to the children. Goodenough’s (1942) instructions used with children were of help here, along with the pilot work mentioned earlier. Instructions for administration of the test placed emphasis upon (1) giving the first response produced by the stimulus word, ( 2 ) responding with only one word, (3) the experimenter’s lack of concern with spelling, and (4) speed of responding. The subjects were told that they would be timed and were requested to record the time it took them to finish the test on the back of their booklets at the end of each session. The experimenter indicated the time on the blackboard as each minute passed during the test. Following the instructions the subjects read the stimulus words and responded by writing their association in the spaces provided. Each page contained 25 words. All subjects were given the Kent-Rosanoff list of 100 words plus the list of 100 additional words in that order. In grades four through six, 50 words were presented in each session. The sessions were ordinarily on consecutive school days, although for some classes a single day or a week-end intervened between sessions. All other subjects were given the Kent-Rosanoff list in one session and the second 100 words in the second session. All tests were administered in the regular classroom by the experimenters.

D. SUBJECTS The test was administered to 250 males and 250 females in each of the grades 4-8, 10, and 1 2 in the Minneapolis Public Schools and 500 males and 500 females in introductory psychology classes at the University of Minnesota. Following data collection, each test was examined to determine whether it met criteria for inclusion in the final sample. Test forms were excluded from further analysis if: (1) the subject had not completed the last five words on the first form given him; ( 2 ) the same response word appeared ten or more times on a page of 25 items; (3) ten or more responses appeared which were also

41

David S. Palermo stimulus items on a page of 25 items; (4) the subject was seen to be copying response words from the blackboard or other classroom source during the test; or ( 5 ) responses to more than 10% of the total set of words were “response faults.” Response faults consisted of illegible or incomplete words, omissions, and sentence-like continuations from one response to the next involving four or more consecutive responses. Although these criteria appear complex and arbitrary, their development was necessitated primarily by the behavior of only the youngest subjects. They resulted in the rejection of a very small percentage of the total population tested.6 More than the required number of subjects was tested at each grade level. Final membership in the sample was based upon a random selection of the number specified from the total pool of tests. When a test form was rejected for one of the above reasons, a replacement was drawn at random from the appropriate grade-sex group.

E. RESULTS All the data were transferred to IBM cards. Each response made by each subject to each stimulus word was put on a separate card. The cards were then sorted by stimulus word for each of the 16 grade-sex groups, and the frequency of each response to each of the stimulus words was printed out. Analyses of the data are based upon the printed-out materials and the various combinations of these data which were done by hand. Several different aspects of the analyses which have been completed thus far will be presented and then several types of experimental studies which have made use of the norms will be summarized. 1. Popular Responses The first set of data deals with the mean percentage of subjects giving the five most popular responses in the two sex groups at each grade level. It could be argued that since children have smaller vocabularies than older subjects they would give a smaller number of total responses and, therefore, the more popular responses would tend to be given by a larger number of younger children than in the case of older subjects. On the other hand, it could be argued that since the children have had less common experience with the language, particular associations would not have had time to become as strong as might be the case with older, more linguistically experienced subjects, resulting in smaller percentages of subjects giving the popular responses in the lower grade groups. The data in Table I tend to support the latter hypothesis. The table shows The total number of subjects rejected on the basis of these criteria were 162, 72, 29, 56, 47, 10, 16, and 6 for the grades 4-8, 10, 12, and college, respectively.

42

Children’s Verbal Behuvior the mean percentage of males and females giving the 5 most popular responses in each of the 8 grade groups for all 200 words. Reading down the first two columns, it may be seen that the mean percentage of the most popular response increases with age for both the males and females. The only inversions occur in the tenth grade males and females and the twelfth grade females. The same general trend, with a greater number of inversions, occurs in the second response. Beyond the second most popular response, the mean percentages are about the same regardless of the grade group. It should also be mentioned TABLE I PER CENT OF MALESAND FEMALES IN EACHGRADE MAKINGTHE FIRSTFIVERESPONSES Response rank 1

3

2

Grade

M

F

M

F

M

P

4

24.66 25.37 25.55 28.10 28.85 27.39 28.96 30.30

26.72 27.53 27.84 29.80 30.68 30.60 30.66 33.00

11.75 11.59 11.46 12.19 12.20 11.96 12.13 12.30

12.29 12.31 12.57 12.78 13.03 12.81 12.90 12.90

7.42 7.54 7.52 7.77 7.64 7.20 7.49 7.60

8.06 7.97 8.30 7.97 7.80 7.90 7.78 7.90

5 6 7 8 10 12

College

5

4

M

F

5.10 5.38 5.30 5.59 5.28 5.73 5.50 5.58 5.39 5.44 5.38 5.45 5.34 5.46 5.30 5.40

M

F

3.92 4.02 4.03 4.20 4.16 4.20 4.18 4.19 4.08 4.08 4.12 4.12 4.14 4.12 4.00 4.00

that if the two sublists are considered separately, the percentages run higher for the Kent-Rosanoff list than they do for the second 100 words, suggesting that communality of responding is less strong in a list including more function and fewer content words. It will be noted here that the percentage of subjects making the popular response shows no evidence of a maximum plateau. The data of Wheat (1931), and earlier of Rosanoff and Rosanoff (1913), using a slightly broader classification of common responses, suggested an asymptote of popular responding at age 11. If the percentages of males and of females giving the five most popular responses are compared there is a very consistent tendency for the female percentages to be larger throughout the table. As a matter of fact, the only instance of a larger percentage of males occurs in the twelfth grade on the fifth response. I n contrast to the report of McGehee (1938), throughout the entire grade range used, the females tend to give the popular responses more frequently than the males, and apparently this trend does not disappear until the responses which are well down in the response hierarchy are considered. If it is assumed, as many kinds of data suggest (see McCarthy, 1954), that females

43

David S. Palermo are more advanced in their language development than males, these data might be interpreted as suggesting that more linguistically advanced or experienced persons tend to strengthen particular associations among words as a function of their experience, which is reflected in their responses to a word association test. This interpretation is, of course, consistent with the age trends just discussed. 2. Number of Different Responses On the basis of these data on percentage of subjects making the popular responses, it might be predicted that the mean number of different responses given to each stimulus would be greater for the younger children, despite their smaller vocabulary, than for the older subjects who have a larger pool of responses available for use. Figure 1 presents these data in graphic form for the

82

-

T \

80-

Mole P-J List Female P-J List e--r Male K-R List Femole K-R List

c --e

-

c-

\ \ \

\

74 72 70

68

\

9\

\

\

.

‘7 h‘*’ /’ \

62

-

60

-

56

‘\ \

\

b

\

66 -

-

A

\

-

64

-4

\ G-\__

0 4

5

6

7

10

8

12

College

GRADE

Fig. 1. Mean number of diffeyent responses given by each grade-sex g r o u p for the lists.

fWO

44

Children’s Verbal Behavior males and females separately and for the Kent-Rosanoff list and the 100 additional words which were included. It is apparent that the mean number of different responses given to each stimulus word decreases with age. The college means may not be considered in this comparison because they are based upon a sample twice the size of the other groups. Such an increase in number of subjects increases the mean number of different responses given by 35-50% of which 2 5-35 % is accounted for by idiosyncratic responses. The bottom two curves represent the mean number of responses given to the Kent-Rosanoff list and the top two curves the mean number of responses to the other 100 words. It may be seen that a list composed largely of nouns and adjectives yields a greater degree of response communality than the grammatically heterogeneous list which was appended to the Kent-Rosanoff list. Regardless of the list, the females give fewer different response words on the average than do the males. These data, of course, support the earlier hypothesis that language experience increases the strength of associations. The older, more experienced subjects give fewer different responses than the younger subjects with less experience despite the fact that vocabulary size increases with age. 3 . Response Overlap Between Grades A. Fourth and Fifth Grades. Table I1 presents a comparison of the specific response words occurring in the first five ranks in the fourth and fifth grades. TABLE I1 RESPONSEWORDS OCCURRING IN THE FIRST FIVE RANKSIN THE FOURTHAND FIFTH GRADES

COMPARISON OF THE

Fourth grade Rank

3

4

5

1 18

0 7 10

40 17 14

36 65 39 41

0 1 13

52 57 77

82

-

200

200

200

135

Grade five

1

Rank 1

174

22

3

2

19

3 4 5

6

134 30 6 5 3

21 105

200

Lower Total

2

1 0 0 200

Lower

36

Total 200

200 200 200 200

135

Reading down the first column, it may be found that of the 200 responses which were most popular for grade four, 174 of them were alsa the most frequently given response by grade five, 19 were the second most frequently given re-

45

David S. Palermo sponse by grade five, 6 were the third most frequently given response by grade five, and 1 was the fourth most frequently given response by grade five. NO response given most frequently by grade four was below the fourth rank in grade five. Reading across the top row, it may be seen that 174 of the most popular responses given in grade five were also given as most popular by grade four, 2 2 were in the second rank, 3 in third rank, and 1 in the fourth rank. Reading down the diagonal of the table, it will be observed that 174 of the responses ranked first in grade five held an identical position in grade four, 134 of the words ranked second in grade five held an identical position in grade four, 105 in the third position were identical in both grades, 65 in the fourth position were identical and 57 in the fifth position were identical. I t is clear from this table that there is a good deal of overlap in the responding of the two grades, and that there is considerable agreement on the relative ranks of the various words. There are only 135 out of a possible 1000 words which are in the first five responses of one grade which are not in the first five of the other grade. The stability of the rankings, however, clearly decreases with the rank of the word. This might be expected, since the frequency of the lower ranked words is generally much smaller. B. Twelfth Grade And College. Table iii presents the same kind of comparison for the two groups at the other end of the age scale: the twelfth grade TABLE 111

COMPARISON OF THE RESPONSEWORDS OCCURRING IN THE FIRST FIVE GRADEAND COLLEGE GROUP RANKSIN THE TWBLPTH Twelfth grade

Rank College

1

2

3

4

Rank 1

166 24 5 1 2 2 200

23 122 35 10

7 26 92 39 18 18 200

13 30 63 32 59 200

2

3 4 5 Lower Total

5 5 200

5

3

1 8 18

43 44 86 200

Lower 0

7 20

44 99

-

Total 200 200 200 200 200 170

170

and college group. While the agreement is slightly less between these two groups than between the fourth and fifth grades, it is again quite clear that there is considerable overlap and agreement on the relative ranks of the various words which are in the first 5 responses for the 2 groups. Again the highest agreement is on the primary response, and the degree of stability de-

46

Children's Verbal Behavior creases down the diagonal from the strongest to the weakest of the 5 responses. Only in 170 cases out of a possible 1000 words is a response given by one group in the first 5 ranks not also in the first 5 of the other group. C . All Adjacent Grades. Table IV indicates the comparisons of the 5 most popular response words occurring in identical ranks for all adjacent grade TABLE IV WORDS COMPARISON OF THE FIVEMOSTPOPULAR RESPONSE OCCURRING IN IDENTICAL RANKSFOR ADJACENT GRADEGROUPS Rank Grade comparison

1

2

3

4

5

4 and 5 5 and 6 6 and 7 7 and 8 8 and 10 10 and 12 12 and College

174 171 149 170 166 167 166

134 123 99 124 124 123

105

122

84 65 87 89 89 92

65 74 56 58 59 71 63

57 59 43 50 55 43 44

4 'and College

107

52

33

22

17

groups. Ignoring the last row and reading down the columns, it may be seen that there is a great deal of consistency in the number of responses which are in exactly the same rank from one grade comparison to the next. Even for the fifth ranked word, while the absolute number is smaller, the consistency across groups is marked. Reading across the rows, it may be seen that, regardless of the grade comparison, there is a definite decrease in the stability of the rank position for all comparisons. The mean agreement in the first rank is 166.14 out of the 200 words, for rank two it is 121.28, for rank three 87.28, for rank four 63.71, and for rank five it is 50.14. These data would tend to indicate that there is a good deal of agreement among adjacent grades upon the responses which appear in the various ranks. If the last row is now considered, it is evident that some gradual shifts do take place in the words occurring in the various ranks from fourth grade to the college level. Out of the 200 words, only 107 are most popular for both the fourth grade and the college students, and as may be seen reading across the row, the agreement is considerably lower at all the rank positions. Some major shifts do occur in the responses which are given to the stimulus words as a function of age. D. Fourth Grade And College. Table V gives the complete comparison of the first 5 responses for the fourth grade and college students. The dispersion

47

David S. Pulermo TABLE V COMPARISON OF THE RESPONSEWORDSOCCURRING IN THE FIRST FIVE RANKSIN THE FOURTHGRADEAND COLLEGE GROUP Fourth grade Rank College

1

Rank 1

107 39 18 8

2

3 4 5

Lower Total

2

6

36 52 27 21 14

22 200

200

50

3

4

5

Lower

Total

20 37 33 32 15 63 200

5 23 30 22 27 93 200

8 15 23 17 17 120 200

24 34 69 100 121 348

200 200 200 200 200 348

around the diagonal is much greater than in the previous tables, and 348, ot over one-third, of the responses given by one group do not appear in the first 5 responses of the other group.

4. Comparisons with Woodrow and Lowell Sample Some comparisons have also been made of the data of the combined fourth and fifth grades with the responses of the sample of 1000 fourth and fifth grade children in the Minneapolis Public Schools collected by Woodrow and Lowell in 1916. All comparisons to be discussed involve only those 90 of the 100 Kent-Rosanoff words used by Woodrow and Lowell. Table VI shows TABLE VI MEANFREQUENCY OF CHILDREN IN THE 1916 AND 1961 FOURTHAND FIFTH GRADESAMPLES MAKINGTHE FIRSTFIVE RESPONSES(90 WORDS) Mean frequency Response rank 1st 2nd 3rd

4th 5th Mean number of idiosyncratic responses Mean number of different responses for each stimulus

48

Palerrno-Jenkins

Woodrow-Lowell

322.16 135.50 82.23 55.14 39.61

278.76 129.81 84.31 61.17 47. a7

87.29

48.98

137.82

96.96

Children’s Verbal Behavior the mean frequency of the 5 most popular responses, the mean number of different responses given to each stimulus word and the mean number of idiosyncratic responses given to each stimulus by the 1000 children in each of the two groups. Looking at the mean frequency of the first 5 responses it may be seen that the number of subjects who gave the 2 most popular responses is much larger than was the case 50 years ago. The third, fourth, and fifth ranked responses, however, are given by a larger number of subjects in the Woodrow and Lowell sample than in the present sample. Considering all of the responses, a mean of slightly more than 63% of the subjects in the present sample gave one of the five most popular responses as compared to slightly over 61% of the Woodrow and Lowell sample. In light of this finding, it is somewhat surprising to note that the mean number of different responses given to each stimulus by the present sample is 137.82 as compared to 96.96 for the earlier sample and 87.29 idiosyncratic responses were given by the present sample as compared to only 48.98 for the Woodrow and Lowell sample. It would appear that the distribution of response frequencies for children today is both more peaked at the high frequency end and also more skewed at the low frequency end. Table VII makes a comparison of the rankings of the specific words in the first 5 positions for the 2 groups. In general, the overlap of responses is TABLE VII RESPONSEWORDS OCCURRING I N THE FIRST FIVE 1916 A N D 1961 FOURTH A N D FIFTH GRADE SAMPLES

COMPARISON OF THE

RANKSI N

THE

1961 Children Rank

1916 Children

Rank 1 2

3 4 5 Lower Total

1

2

41 5

19 17

11

8

4 6

5 7 34 90

23

90

3

4

5

7

8 8 10 10 8

1 11

14

9 9 7 53

41 57 -

90

200

12 11 11

5 44 90

46 90

Lower

37 51

Total 90 90 90 90 90 200

less between these 2 groups than was the case in the comparison of the fourth grade children with the college sample in Table V. Here it may be seen, that of the words ranked highest by the children in 1916, only 41, less than half, are in the same rank in 1961. There are 200 response words out of the possible 450 which are in the first 5 ranks of one group which are not in the first

49

David S. Palerrno 5 ranks of the other group. Clearly, some marked changes have occurred in the associations to these words by fourth and fifth grade children since 1916. Later in the chapter an attempt will be made to indicate same of the kinds of changes which have occurred.

F. RESPONSECLASSIFICATIONS Now that it has been established that there are developmental changes which occur in the associations to the 200 word list, and that there are changes which have occurred over time in the associations of children, classification of the responses of the groups in various ways has been started in an effort to determine the nature of the differences. Both semantic and grammatical classifications have been made. Thus far, the semantic categories of superordinates (Palerrno and Jenkins, 1962; 1963), and opposites have been examined and all of the stimuli and the five most frequent responses to those stimuli have been analyzed by grammatical class. 1. Superordinates Looking first at the semantic class of superordination, tabulation has been made of the frequency and percentage of superordinate responses for the males and females in each of the grade groups. The behavioral definition for superordinate responses used by Jenkins and Russell (1960) was employed. I n that study a written test was given to 2 9 undergraduate students in introductory psychology which consisted of a set of 100 sentences of the form is a member of the class .” Each sentence began with one of the Kent-Rosanoff stimulus words. A superordinate response was defined as any completion that was given by 15 or more of the students taking the test. Only the Kent-Rosanoff words were used in this analysis. Figure 2 presents the mean percentage of superordinate responses for each grade level for the totaI 39 words to which superordinate responses could have been given and for the 26 stimulus words to which at least 5 % of the population of one of the groups responded with a superordinate response. I n the lower curve there is an increase in superordinate responses from a mean of 14.79% in grade four to a mean of 15.96% in grade six followed by a steady decline thereafter to the college mean level of 10.00%. I n the case of the more frequently given superordinate responses, there is a slight decline from the mean of 21.89% for the fourth grade to 21.79% for the fifth grade followed by a rise to 23.40% for the sixth grade and then, again, a steady decline to a mean of 14.60% for the college students. While the differences in absolute percentages are not extremely large, the

50

Children's Verbal Behavior consistency of these differences is impressive. Sign tests were applied in comparisons of each adjacent grade group for the total 39 words and for those 26 words to which at least 5 % of the population of one of the groups responded with a superordinate response. The results of these tests are given in Table VII. Comparisons of grades 5-6, 6-7, 7-8, and 10-12 all reach 25 24 23 v,

:

22

Bm

21

a

20

tz

19

(r

18

2 W

W

n 0

n

17

3

v, t-

z n

f

16

15 14

5

13

=

12

W

II 10

4

5

6

7

8

10

12

College

GRADE

Fig. 2. Mean percent superordinate responses by grade for the total 39 words and the 26 words t o which 5% of at least one of the groups responded with the superordinate (Palermo and Jenkins, 1963 1.

at least the .05 level of significance using the total 39 words. Comparisons of grades 5-6, 6-7, 7-8, 8-10, and 12-college all reach at least the .05 level using only the words which yield at least 5 % superordinate responses. An analysis of the curves for each individual word indicates that while the peak of responding may shift to the seventh or eighth grade for some individual words, only in the case of sickness-health was there a complete reversal in the trend shown by the grouped data. The response of health to sickness steadily increased with age.

51

David S. Palermo It is clear from these data that a simple logical analysis of language which suggests that an increase in age or maturity results in an increase in the use of abstract (superordinate) as opposed to concrete semantic content as suggested by Flavell et al. (1958) and others is incorrect insofar as responses to a word association test are concerned. Responses classified as superordinates appear to increase to a maximum at the sixth grade level and decline thereafter. Data currently being collected from children in grades one through three using oral presentation and response will be used to determine the characteristics of the responses of younger children. A. Compared With Woodrow And Lowell Sample. In addition, comparisons have been made of these data on superordinates with those of Woodrow and TABLE VIII OF WORDS IN WHICH ONE CLASS EXCEEDED AN ADJACENT NUMBER CLASSIN SUPERORDINATE RESPONDING All 39 words

Comparison grades 4-5 5-6 6-7

20 26 11

7-8

8

8-10

12 11 15

10-12 12-College 0

b

Lower > Upper > lower Tie upper 4 3 1 2 3 2 2

15 loo 27" 29b 24 26" 22

26 words (5%)

Upper > Lower > lower Tie upper 14 21 6 4

5 8 7

0 0

1 0 0 1 0

12 5b 19" 22b 21*

17 19"

Results of two-tailed sign test significant at 0.05 level. Results of two-tailed sign test significanr at 0.01 level.

Lowell. Since Woodrow and Lowell did not use two of the 39 words (bitter and mutton) to which superordinates could be made according to the definition currently used, the data are based upon only 37 words. The mean percentage of superordinate responses for the present sample was 15.12 as compared to 11.49% in 1916. The same comparisons for the 22 stimulus words to which at least 5 % superordinate responses were given by one of the two groups yielded a mean of 24.61% for the present sample and 18.78% for the 1916 sample. In both cases two-tailed sign tests applied to these data were significant beyond the .05 level. Additional analyses of superordinate responding in the two groups done on the basis of the definition used by Woodrow and Lowell yielded essentially the same results. B. Compared With Adult Studies. The trends in superordinate responding revealed by these data are in contrast to those found for adults by Jenkins

52

Children’s Verbal Behavior and Russell (1960). They report that from 1910 to 1952 there has been a decrease in superordinate responding by adults while here it is found that during the same period there has been an increase in superordinate responding by children in grades four and five. While there may be many interpretations of these findings, the data may be accounted for in a simple fashion if it is assumed first, that superordinate responding is curvilinearly related to linguistic development, rising to a peak during the earlier years and decreasing steadily thereafter, and second, that the rate of linguistic development is more rapid today and proceeds to a higher degree of sophistication than it did in 1910. If these assumptions are correct, it suggests that an extensive age sampling in the 1910 period would have shown a peak of superordinate responding at an age much closer to the adult level. The fourth and fifth grade sample would have been relatively low in this type of responding and the adult sample would have been relatively high. With the increasing linguistic sophistication of our culture, subsequent sampling would have indicated a movement of the peak of such responding backward toward younger ages so that in the 1961 sample the peak is found at the sixth grade, while the adult level of such responses has moved well beyond the peak and become relatively low. The first assumption receives some support from the relation observed between frequency-of-usage of response words and the developmental curve for the use of these responses as superordinates. Superordinate responding in the case of mutton-meat, spider-insect, butterfly-insect, heavy-weight, and cabbage-vegetable does not reach a peak in frequency until the seventh or eighth grade even in the present sample. The responses in these particular cases tend to be much lower in frequency-of-usage according to the Thorndike-Lorge Juvenile count than the other superordinates given by at least 5% of the subjects. Thus, within the limited frequency range of responses used, it is the higher frequency-of-usage superordinates which peak at the earlier ages. It seems reasonable to suppose, then, that high density of linguistic exposure and increased linguistic sophistication should act to move the peak for all superordinate responding backward to the earlier years. Such an hypothesis is consistent with the earlier analyses of Eastman and Rosanoff (1912) and Horan (1956). 2. Oppmite Responses

Analysis of the semantic category of opposites is not yet as complete as that for the superordinates, but again definite trends are apparent in the data which have been examined. The definition of an opposite used here was obtained for another purpose, but it was decided to employ it initially since it was available and was obtained in essentially the same manner as that for superordinates. Each of 122 words taken from the 200 word list was placed

53

David S. Palermo in a sentence frame of the form, is the opposite of where the stimulus word appeared in the first blank and 62 introductory psychology students were instructed to fill in the second blank. A column labeled “no opposite” was also provided and subjects were instructed to check this if they thought a word had no real opposite. The stimuli were selected by taking the 31 words from the Kent-Rosanoff list and the 2 5 words from the second 100 words which seemed most likely to have true opposites and, in addition, a random selection of an equal number of the remaining words in each list to make a total of 122 words. Only those 57 words to which at least 33 of the 62 students agreed upon the opposite were used in the analyses. Table IX shows the mean percentage of opposite responses given by the males and females at each grade level as well as the total mean percentage for the “

I

TABLE IX PERCENTOF MALESAND FEMALES IN EACH GRADBMAKINGOPPOSITE RESPONSES Grade

Male

Female

Total

4

21 .o 20.2 20.6 29.0 34.1 29.0 32.6 36.7

22.1 24.4 23.0 31 .O 34.5 32.7 34.2 40.0

21.5 22.3 21.8 30.0 34.3 30.8 33.4 38.3

5 6 7 8 10 12

College

sexes combined. In contrast to the superordinate data, it may be seen that there is a trend upward from a mean of 21.5% at grade four to a mean of 38.3% at the college level. There are, however, several reversals in the trend. It will be noted, in comparing the males and females, that the females invariably gave a higher percentage of opposites than the males, consistent with the other analyses in which it has been found that if there is a trend with age, the females tend to be more advanced than the males. It might also be noted here that these results are in agreement with what might be predicted from the data reported earlier and a recent analysis of opposite responding by Carroll et al. (1962). The latter authors have shown that opposite responding of adults is a stable and consistent response which is highly correlated with communality of responding. The data of the present study indicate that with increasing age communality of responding increases, suggesting, as was found, that opposite responding would increase with age. The fact that the percentage of subjects making the popular response increases

Children’s Verbal Behavior with age much more smoothly than the percentage of subjects making opposite responses merits further investigation in light of the assertions made by Carroll et d. 3. Grammatical Classes The second type of analysis of the differences in responses as a function of age dealt with the grammatical classification of the stimuli and responses. Each of the stimulus words and the five most frequent responses were grammatically classified according to the Thorndike-Barnhart Comprehensive Desk Dictionary (Barnhart, 1951). The Thorndike-Barnhart Dictionary lists the meanings of words in order of their frequency of usage. In cases in which words could be classified as more than one part of speech, the first and presumably most frequent classification was arbitrarily used. Table X shows the per cent of the 5 most frequent responses which were paradigmatic, or of the same form class as the stimulus word, in each of the PER CENT OF AS THE

TABLE Xj FIVE MOSTPOPULAR RESPONSES CLASSIFIED SAME PART OF SPEECH AS THE STIMULUS

THE

Grade 12

Grade 4

Stimulus word Noun Plural Noun Pronouns Adjectives Comparative Verbs Transitive Intransitive Participle Adverbs Prepositions Conjunctions Interjections

Number of words

Per cent responses

Weighted per cent responses

Per cent responses

Weighted per cent responses

68 11 14 38 9

70.7 25.4 56.3 52.5 22.7

73.1 31.5 65.0 5 9. 6 30.5

71.2 32.6 56.8 42.2 28.9

76.6 43.1 70.1 55.9 53.9

14 15 5 17 10 6 2

28.4 3 1. 1 19.2 30.5 15.7 15.6 20.0

32.0 25.0 14.5 36.3 26.6 1 6. 1 24.7

36.6 38.7 28.0 44.2 21.6 33.3 30.0

4

45.3 42.4 28.7 53.9 36.0 35.6 38.8

12 grammatical classes separately for the fourth and the twelfth grades. Column one shows the number of stimuli in each of the grammatical classes followed in column two by the per cent of the 5 responses which fell in the same grammatical class for grade four. Column three indicates the per cent of the same form class responses weighted by the frequency of those responses in grade

55

David S. Palernzo four. Columns four and five show the per cents and weighted per cents for the twelfth grade. It may be seen, first, that with the exception of the intransitive and participle verb forms, the weighted per cents are higher than the unweighted per cents, indicating that the paradigmatic responses tend to be the more frequently given responses for both the younger and the older subjects. Comparing the fourth with the twelfth grade, the percentage of paradigmatic responses is higher in the twelfth grade than in the fourth grade for all grammatical classes except the total group of adjectives. The comparative adjectives, taken alone, follow the trend of the other grammatical classes but when the entire set of adjectives is considered there is a reversal in the expected trend. The differences between the two groups are relatively small in the case of nouns and pronouns but the rest of the differences appear to be substantial. It will also be noted that the differences between the 2 groups on the weighted per cents are greater than on the unweighted per cents in nearly every case, indicating that not only the number but also the frequency of paradigmatic responses is greater in the older group. Thus, it would appear that with the exception of adjectives, the older subjects tend to give words in the same form class as the stimulus word more frequently than do younger subjects. This is less true of singular nouns and pronouns than of the other parts of speech. Adjectives, however, do not follow this pattern. Just why this should be the case with adjectives rather than nouns, for example, is not clear. Unfortunately, the data for all the grades have not yet been analyzed to determine the complete developmental relationship here. I n terms of the unweighted per cents, the relative amount of paradigmatic responding to nouns,6 adjectives, intransitive verbs, transitive verbs, and adverbs by the fourth grade children agrees with the order obtained by Brown and Berko (1960) for their third grade children except that paradigmatic responding was greater in their sample for transitive verbs than for adverbs. An analysis has been made of the grammatically classified responses of the Woodrow and Lowell sample compared with those of the present fourth and fifth grade sample. Table XI shows the grammatical classification of the 90 words used by Woodrow and Lowell, the number of words in each class, the per cent of paradigmatic responses of each group and the weighted per cent of paradigmatic responses of each group. It may be seen that the present sample tends to give paradigmatic responses with a greater frequency, both weighted and unweighted, in the noun and adjective classes where the number of words is most substantial. Only in the case of the one transitive verb did the 'The nouns in the present study are almost exclusively count nouns. Brown and Berko distinguished between count nouns and mass nouns and while they obtained the greatest amount of paradigmatic responding to count nouns, there was less paradigmatic responding to mass nouns than to any other grammatical class.

Children’s Verbal Behavior Woodrow and Lowell sample give a greater weighted per cent of responses than the present sample. In the case of intransitive verbs and participles the 1961 sample gave a substantial weighted percentage of paradigmatic responses while the Woodrow and Lowell sample gave none. As has been found in every comparison made thus far, the responses of the fourth and fifth grade children today are more similar to the responses of adults today than they are to the responses of the children 50 years ago. These are the main analyses which have been completed, thus far, on the normative data. The collection and analyses of norms are of interest in themselves, but it is a time consuming, frustrating sort of task in which one TABLE XI PER CENT OF THE FIVEMOST POPULAR RESPONSES CLASSIFIED AS THE SAME PART OF SPEECH AS THE STIMULUS FOR THE 1916 AND 1961 SAMPLES Woodrow-Lowell

Stimulus word Noun Plural Noun Adjective Verb Transitive Intransitive Participle

Weighted per cent responses

Palermo-Jenkins

Per cent responses

Weighted per cent responses

51.1

70.0 0.0 57.3

73.6 0.0 62.1

29.1 0.0 0.0

20.0 30.0 20.0

25.2 27.5 12.0

Number of words

Per cent responses

62 1 22

61.9 0.0 34.5

62.6

1 2 2

20.0 0.0 0.0

0.0

can become buried under mountains of data which may be analyzed in a myriad of ways. It is easy to find a variety of age trends, sex differences, and time differences, for example, but with each such analysis there are more questions asked than there are answered. Speculations about reasons for some of the differences obtained in the norms have been presented here but the answers will come from research attempting to manipulate variables which may be relevant to the behavior in question.

IV. Experimental Uses of the Normative Data The primary purpose in collecting these norms was to provide a tool which could be used in determining the effects of known associates on behavior in various other kinds of tasks such as paired-associate learning, recall, semantic generalization, mediated generalization, tachistoscopic recognition, and, it is

57

David S. Palerrno hoped, eventually the broader problem of language itself. A beginning has been made by using the norms in studies of paired-associate learning, clustering in recall and associative generalization.

A. PAIRED-ASSOCIATE LEARNING It has been assumed by most persons who have collected and used word association norms that the ranking of responses by the frequency with which those responses have been given by a large population of subjects, reflects the relative strengths which those responses have for individual subjects, i.e., the norms are assumed to reflect a verbal associative habit family hierarchy. One of the most obvious places to test such an assumption is in a pairedassociate learning task. The first study to be presented, done by Wicklund (1963), was designed to determine the effects of associative strength upon paired-associate learning in children. This problem is of particular interest because of the failure to find differences in paired-associate learning of adults when free associative strength has been varied. While Underwood and Schult (1960) have found differences in paired-associate learning of lists composed of restricted associates varying in strength, Jenkins, in a number of unpublished studies, has had little success in establishing differences in paired-associate learning as a function of free associative strength to the Kent-Rosanoff words. He has found that when college students are presented with a list of pairedassociates composed of pairs with as little as 2% strength, as defined by the norms (i.e., two persons in the normative group of 1008), learning takes place in approximately three trials, one of which is the first exposure and two of which are the criterion trials. Apparently, with adults, even a very low strength pair according to the norms is strong enough that a single exposure in a paired-associate task is enough to produce almost perfect performance. This is not altogether surprising when the pairs of words which have this strength are considered, e.g., dark-love and cheese-dry. The contention, however, when this project began, was that young children would not have such strong associations among words which would, in turn, allow the demonstration of differences in paired-associate learning. Evidence that differences could be demonstrated at extremely high and extremely low associative strengths has already been demonstrated with children by Castaneda et al. (1961) and McCullers (1961) using the norms reported in the first of these studies. Wicklund’s study involved three lists of words in which the stimuli were the same for all three lists. In List I, the responses were the most popular responses for those stimuli as defined by the fourth grade norms. In List 11, the responses were selected from those given by not more than 4.8% nor less than 3.4% of the norm group. I n List 111, the responses were selected

58

Children’s Verbal Behavior from those given by not more than 1.0% nor less than .6% of the norm group. In no case was any response to a particular stimulus given by more than one subject to any other stimulus in the list. The lists consisted of 10 pairs and within the lists, half of the stimulus words had popular responses given by 49 to 64% of the norm group and the other half of the stimulus words had popular responses given by not more than 18.8 nor less than 14.2% of the norm group. Table XI1 presents the actual lists which were used, indicating TABLE XI1 STIMULI

AND RESPONSES USED IN THE OF THE PAIRED-ASSOCIATE STUDY BY

List I1

List I Stimulus words

R

LAMP

LIGHT

HIGH

LO w

QUEEN HAPPY

96 64.0 51.2 54.2 50.6 49.0

Mean = 53.80 SPIDER EARTH

WEB GROUND GOOD

DOORS

WINDOWS

MUSIC

SING

THREELISTS WICKLUND

18.8 16.2 17.2 18.8 14.2

Mean = 17.04

R TABLE UP

SHARP

MAN SAD

List I11

96 4.2 4.8 3.8 3.8 3.4

Mean= 4 . 0 ANIMAL SKY WELL SHUT

SINGING

4.0 3.4 4.4 3.8 3.4

Mean= 3 . 4

R OIL DOWN NO MONEY

MAD

%

0.8 0.6 0.6 0.6 0.6

Mean = 0 . 6 4 UGLY WATER

FRUIT KNOCK DANCING

1 .o 0.6 0.6 0.6 0.6

Mean = 0.68

the high and low strength primary response subdivisions of the lists and the strength of the responses taken from the norms. It will be noted that the lists were designed to evaluate the effects of using high and low strength popular responses and the meaning of using a 4% response given to a stimulus word having a strong popular response as compared to a 4% response given to a stimulus word having a low strength popular response. The latter evaluation relates to a difficult measurement problem in this area which can only be appraised by use of the norms in experiments such as this. For example, the most popular response to lamp is right which is given by 64% of the fourth grade population while the most popular response to spider is web but it is given by only 18.8% of the population. The question of concern here is the associative strength of table to lamp and animal to spider both of which are given by approximately 4% of the population to their respective stimuli. If a large percentage of the subjects give

59

David S. Palermo the popular response to a stimulus word, there are relatively few subjects available to give alternative responses. It is possible that the strength of the alternative responses may be underestimated in such cases when compared with the alternative responses to a stimulus word which has a Iow strength primary response. Each list was presented individually to 25 fourth grade children. The subjects were given the usual paired-associate instructions in which they were asked to say out loud the response paired with each stimulus word. A 2-sec anticipation interval, a 2-sec joint presentation interval, a 2-sec interpair interval and 6-sec intertrial interval were used. The words were typed in large capital letters on small sheets of paper, glued to plastic cards and presented by a Hunter Card Master. Three different orders of each list were used to avoid serial learning. Lists were presented for 15 triaIs or three successive errorless trials, whichever occurred first. TABLE XI11 MEANNUMBER OF ERRORSFOR EACH TYPEOF PAIR IN EACH PAIRED-ASSOCIATE LIST High pairs (mean)

Low pairs (mean)

All pairs

I

3.36

111

9.20 10.68

5.92 10.40 10.56

9.28 19.60 21.24

List

I1

(mean)

Table XI11 presents the mean number of errors made on each half of each list. It may be seen that the mean number of errors increases from List I to List I11 indicating greater difficulty in learning the lists as an inverse function of associative strength, I n addition, it may be seen that in List I the pairs with a low strength primary response are more difficult to learn than those with a high strength primary response. This difference is also apparent in the second list but there is essentially no difference in the third list. An analysis of variance of these data indicated significant differences among lists at the .001 level, significant differences between types of pairs at the ,005 level and an interaction between lists and pairs significant at the .025 level. These results were, of course, very encouraging for a number of reasons. First, the fact that differences in associative strength can be used in a pairedassociate learning problem to vary the difficulty of the task suggests that the children’s norms may have greater utility for some kinds of problems than the adult norms. Not only was it possible to demonstrate differences between very strong and very weak pairs, which has not been demonstrated with the Kent-Rosanoff norms using adults, but gradations of difficulty within the

GO

Children’s Verbal Behavior extremes of associative strength were demonstrated, Second, these results provide an indication that a response of 4% strength to a stimulus with a strong primary response is probably stronger than a response of 4% strength to a stimulus with a weak primary response.

B. ASSOCIATIVE CLUSTERING IN RECALL The norms have also been used in two experiments dealing with associative clustering in recall. Although clustering has been demonstrated with children using generic categories (Bousfield et al., 1958; Osborn, 1960), the first study was designed to determine whether it was possible to obtain associative clustering in recall of fourth grade children. A total of 60 children, 2 fourth grade public school classes, served as subjects. Each class was read a list of 36 words at a speed of approximately one word every 2 sec. The list was composed of 15 stimulus-response pairs taken from the norms. The response in each case was the most popular response to the stimulus and occurred with a mean frequency of 35.3% in the norms. The members of the pairs in the list were arranged in a random order with the restriction that no associated words immediately followed each other either in a forward or a backward direction. The list was preceded by three filler words and followed by three filler words in order to reduce the effects of serial order on clustering in recall. Following the reading of the list, the children were instructed to write down all the words they could remember from the list in any order that they were remembered. Every 30 sec the subjects were asked to draw a line under the last word they had written and they were given as much time as they needed to write down all the words they could recall. The written responses of the children were analyzed for the total number of words recalled, the number of stimulus-response clusters, or pairs, recalled in both a forward and a backward direction, and the percentage of forward and backward clusters as a function of opportunity to cluster. A mean of 8.22 words was recalled by each subject exclusive of the filler words, intrusions and illegible responses. Of the 8.22 words recalled, a mean of 1.55 associative pairs were included of which .80 were forward pairs and .75 were reverse pairs. Since each cluster involves two words, approximately 38% of the responses recalled were recalled in either a forward or a backward cluster. A two-tailed sign test was used to evaluate the differences between the frequency of forward and backward clustering and chance; in both cases the differences were significant beyond the .01 level. Chance clustering was determined by actually counting the number of occurrences of pairs drawn at random from the words used. The mean occurrence of such clusters for each subject was .05. Finally, the data were analyzed for the mean percentage of clusters as a function of

61

David S.Palermo the opportunities for a forward or backward cluster. For example, for a given A-B pair a forward clustering “opportunity” was scored if the child recalled A before he recalled B; a reverse “opportunity” was scored if the child recalled B before he recalled A. The actual occurrence of forward clusters was expressed as a percentage of the forward “opportunities” and the occurrence of reverse clusters was similarly treated. Clustering as a percentage of opportunity was 30.38% in the forward direction and 25.57% in the backward direction. The second study was administered in exactly the same fashion as the first, except that the list to be recalled was composed of three groups of 5 stimuli and their primary responses which differed in associative strength. Five of the stimulus-response pairs had a mean associative strength of 64.4%, 5 had a mean associative strength of 38.8% and 5 had a mean associative strength of 10.8%. Two different classes of fourth grade children composed of a total of 61 children served as subjects. In this study, a mean of 6.85 words was recalled and a mean of 1.16 pairs was included in that total, accounting for approximately 34% of the words recalled. The mean number of pairs in the forward direction was 0.52 and in the backward direction 0.65. Table XIV shows the complete results of both TABLE XIV RESULTSOF

CLUSTERING IN

RECALLSTUDIES Study I1 (15 pairs)

Study I (1 5 pairs)

Mean % strength of pairs Mean number of words recalled Mean forward pairs Mean backward pairs Mean arbitrary pairs % o f total opportunities forward % of total opportunities backward

55.3 8.22 .80 .75 .05

30.38 25.57

H

M

L

64.4

38.8 2.38 .I8 .20

10.8 1.30 .06 .02

3.18 .28 .43 .05 32.69 32.50

.05

22.91 19.67

.05

Total

6.85 .52 .65 .16

10.81 .03

studies of clustering. The results of the first study are given in the first column and the results for the second study are given to the right and presented separately for each level of associative strength. It will be noted that while the amount of clustering in the second study is not overwhelming, there is a definite relationship between associative strength and amount of clustering. The frequency of arbitrary pair clustering is approximately the same as that for the low associative strength pairs. Finally, the table shows the percentage of clustering as a function of opportunities for clustering in the forward

62

Children’s Verbal Behavior and backward direction. Although, in the second study, the absolute number of clusters in the reverse direction is greater than in the forward direction, it may be seen that in terms of opportunities for clustering the forward associations occurred more frequently. Two-tailed sign tests were used to evaluate the statistical significance of these data; for all associative pairs combined, the amount of clustering in both the forward and the backward direction is significantly greater than chance at the .01 level. Again, the results of these two studies seem to be encouraging. If these results are compared with those obtained from adults, (e.g., Jenkins and Russell, 1952; Jenkins et al., 1958), percentage of clustering is considerably less in the recall of the children. Jenkins et al. (1958) found in comparable studies with college students that the percentage of total recall accounted for by clustering was closely related to the average free associative strength of the pairs in the list. The results of the studies with children indicate that the amount of clustering is considerably less than that. Again, the data suggest that the norms for children are reflecting associations which are of less strength, in terms of their influences on performance in other kinds of tasks, than is the case with adults.

C. ASSOCIATIVE GENERALIZATION The last study to be presented here was conducted to determine the amount of generalization, if any, which may be demonstrated to occur from one word to an associate of that word. The procedure was taken from that used by Mink (1963). Each child was shown a list of 1 2 stimulus words from the word association test presented in two different random orders by a memory drum. The subject was instructed to remember the words and to press a telegraph key mounted in front of the drum each time a word appeared. Following the second presentation of the list, another list was presented which was composed of 6 words from the first list, the 6 primary responses to those words (mean associative strength = 63.85%), the other 6 words from the first list and 6 control words which had no associative strength to any of the twelve words in the first list. The second list was presented 6 times and the child was instructed to press the telegraph key each time he recognized a word from the first list. The words were presented for 2 sec each in both lists. Forty-eight fifth grade public school children served as subjects. The results were analyzed in terms of the number of presses of the key to the two sets of stimulus words, the associated words and the control words for the first trial and the total six trials. A t-test for correlated measures was applied to the difference between the mean number of presses to the associated and the control words. The t-value of 8.45 (df = 47, SEdi,,, = .66)

63

David S. Palermo for the total 6 trials was significant beyond the .001 level. A difference significant at the same level of confidence was also obtained for the first trial alone ( t = 5.64, d f = 47, SEdi,,. = .14). The per cent of presses was 83.62 to the first list words with associates in the second list, 83.56 to the first list words with no associates in the second list, 22.80 to the associated words and 7.29 to the control words over the six trials. Only one subject made more responses to the control than to the associated words. Thus, a third type of experimental situation involving the use of the natural language associates obtained from the norms has demonstrated the potency of this variable in the verbal behavior of children. It is somewhat surprising that the amount of associative generalization observed in this study appears to be greater than that found by Mink with adult subjects. The results of the previous two studies had suggested that in situations in which the effects of associative strength are extremely strong in adult learning tasks, as in the case of paired-associate learning, the measure would be found to be sensitive for children but in cases where differences in associative strength are reflected in the adult tasks, there would be less effect on the performance of children. The results of the generalization study do not conform to this interpretation. There are, however, some differences in list length and composition of the second list which make it impossible to make direct comparisons between the child and adult studies and which make it necessary to withhold judgment about the relative effects of associative strength for different age groups in this situation.

D. FUTURERESEARCH These are the beginnings of the more exciting aspects of the research visualized three years ago when this project was begun. There is still a good deal of what might be called “brush-clearing” research to be done. Norms on a smaller population of subjects in the fifth grade have been collected to determine the associations to the primary responses in the norms. These data will provide three word associative chains which may be used in studies of mediated association, for example. In addition to the necessity of obtaining data on chains of associates, it has been necessary to consider the use of nonsense syllables in some of the planned experiments but this requires some information about the effects of nonsense syllables on children’s learning, As a result, George Flamer has recently completed a study of pairedassociate learning to determine whether fourth grade children can learn lists in which nonsense syllables are used as responses and whether nonsense syllable association values obtained from adults affect the learning of fourth grade children. The results of that study have provided a clear affirmative answer to both questions. These kinds of studies seem continually to slow down

G4

Children’s Verbal Behavior the efforts to examine the more interesting problems. In a sense, however, the most interesting part of the research lies ahead, for once the similarities and differences between the behaviors of children and adults are known, it will be possible to investigate some of the variables determining those differences which should be the most fruitful part of this project.

REFERENCES Barnhart, C. L. (Ed.) Thorndike-Barnhart comprehensive desk dictionary. New York: Doubleday, 1951. Bastian, J. Associative factors in verbal transfer. J. exp. Psychol., 1961, 62, 70-79. Bialer, I. Primary and secondary stimulus generalization as related to intelligence level. J. exp. Psychol., 1961, 62, 395-402. Bousfield, W. A,, Esterson, J., & Whitmarsh, G. A. A study of developmental changes in conceptual and perceptual associative clustering. J. genet. Psychol., 1958, 92, 95-102. Bousfield, W. A., Whitmarsh, G. A,, & Berkowitz, H. Partial response identities in associative clustering. J. gen. Psychol., 1960, 63, 233-238. Brown, R., & Berko, J. Word association and the acquisition of grammar. Child. Develpm., 1960, 31, 1-14. Carey, J. E., & Goss, A. E. The role of verbal labeling in the conceptual sorting behavior of children. J. genet. Psychol., 1957, 90, 69-74. Carroll, J. B., Kjeldergaard, P. M., & Carton, A. S. Number of opposites vs. number of primaries as a response measure in free association tests. J. verb. Learn. verb. Behav., 1962, 1, 22-30. Carter, H. D. A preliminary study of free association. I. Twin similarities and the technique of measurement. J. Psychol., 1938, 6, 201-215. Castaneda, A., Fahel, L. S., & Odom, R. Associative characteristics of sixty-three adjectives and their relation to verbai paired-associate learning in children. Child Develpm., 1961, 32, 297-304. Cofer, C. N., & Yarczower, M. Further study of implicit verbal chaining in pairedassociate learning. Psychol. Reps., 1957, 3, 453-456. Cramer, P., & Cofer, C. N. The role of forward and reverse associations in transfer of training. Amer. Psyrhol., 1960, 15, 463. Deese, J. On the prediction of occurrence of particular verbal intrusions in immediate recall. J. exp. Psychol, 1959, 58, 17-22. Dietze, D. The facilitating effect of words on discrimination and generalization. J. exp. Psychol., 1955, 50, 255-260. Eastman, F. C., & Rosanoff, A. J. Association in feeble-minded and delinquent children. Amer. J. Insan., 1912, 69, 125-141. Eisman, B. S. Attitude formation: the development of a color preference response through mediated generalization. J. abnorm. soc. Psychol., 1955, 50, 321-326. Elonen, A. S., & Woodrow, H. Group tests of psychopathic tendencies of children. J. abnorm. soc. Psychol., 1928, 23, 315-327. Ervin, S. M. Changes with age in the verbal determinants of word-association. Amer. J. Psyrhol., 1961, 74, 361-372. Flavell, J. H., Draguns, J., Feinburg, I.. K., & Budin, W. A. A microgenetic approach to word association. J. abnorm. soc. Psychol., 1958, 57, 1-7.

65

David S. Palermo Furst, E. Statistical investigations on word associations and on familial agreement in reaction type among uneducated persons. In C. G. Jung (Ed.), Studies in word association. Trans. M. D. Eder. London: William Heinemam, 1918. Pp. 407-445. Goett, T. Assoziationsversuche an kindern. Ztsch. f. Kinderheilkunde, 1911, 1, 241-345. Goodenough, F. L. The use of free association in the objective measurement of personality. In Q. McNemar, & M. A. Merrill (Eds), Studies in personality. New York: McGrawHill, 1942. Pp. 87-103, Horan, E. M. Word association frequency tables of mentally retarded children. J. consult. Psychol., 1956, 20, 22. Horn, E. A basic writing vocabulary-10,000 words most commonly used in writing. Univer. Iowa Monogr. Educ., 1926,No. 4. Jarrett, R. F., & Scheibe, K. E. Association chains and paired-associate learning. 1. verb. Learn. verb. Behav., 1963,1, 264-268. Jenkins, J. J., Mink, W. D., & Russell, W. A. Associative clustering as a function of verbal association strength. Psychol. Reps., 1958, 4, 127-136. Jenkins, J. J., & Russell, W. A. Associative clustering during recall. J. abnorm. sot. Psychol., 1952, 47, 818-821. Jenkins, J. J., & Russell, W. A. Systematic changes in word association norms: 1910-1952. J. abnorm. soc. Psychol., 1960,60, 293-304. Kendler, T. S., Kendler, H. H., and Wells, D. Reversal and nonreversal shifts in nursery school children. J. romp, physiol. Psychol., 1960,53, 83-88. Kent, G. H., & Rosanoff, A. J. A study of association in insanity. Amer. J . Insan., 1910, 67, 37-96, 317-390. McCarthy, D . Language development in children. In L. Carmichael (Ed.), Manual of child psychology (2nd ed.) New York: Wiley, 1954.Pp. 492-630. McCullers, J. C. Effects of associative strength, grade level, and interpair interval in verbal paired-associate learning. Child Develpm., 1961,32, 773-778. McCullers, J. C. An analysis of some factors underlying intralist associative transfer in paired-associate learning. J. exp. Psychol., 1963, 65, 163-168. McElwee, E. W. Association in normal and subnormal adolescents. Amer. J . Psychiar., 1931, 11, 311-318. McFadden, J. H. Differential responses of normal and feebleminded subjects of equal mental age, on the Kent-Rosanoff free association test and the Stanford Revision of the Binet-Simon intelligence test. Ment. Meas. Monogr., 1931,No.7, 85. McGehee, N. E., & Schulz, R. W. Mediation in paired-associate learning. J. exp. Psychol., 1961, 62, 571-575. McGehee, W. The free word association of elementary school children. J. genet. Psychol., 1937, 50, 441-455. McGehee, W. The free word association of elementary school children: 11. Verbal responses. J. genet. Psychol., 1938,52, 361-374. Martin, J. G . Mediated transfer in two verbal learning paradigms. Unpublished Ph.D. thesis, Univer. of Minnesota, 1960. Meumann, E. Intelligenzprufurngen an kindern der volkschule. Die exp. Pudag., 1905, 1, 86-101. Milgram, N. A. Microgenetic analysis of word associations in schizophrenic and brain damaged patients. J. abnorm. SOC. Psychol., 1961, 62, 364-366. Mink, W. D. Semantic generalization as related to word association. Psycbol. Reps., 1963, 12, 59-67. Mitchell, I., Rosanoff, I. R., & Rosanoff, A. J. A study of association in Negro children. Psychol. Rev., 1919, 26, 354-359.

Children’s Verbal Behavior Moran, L. J., Mefferd, R. B., Jr., & Kimble, J. P., Jr. A standardized twenty alternate form word association test for measurement of daily change in psychiatric condition. Paper presented at the American Psychological Assn. Meetings, 1960. Norcross, K. J. Effects of discrimination performance of similarity of previously acquired stimulus names. J. exp. Psyckof., 1958,56, 305-309. Norcross, K. J., & Spiker, C. C. Effects of mediated associations on transfer in pairedassociate learning. J. exp. Psychol., 1958,55, 129-134. O’Neil, W. M. The effect of verbal association on tachistoscopic recognition. Australian J. Psychol., 1953,5, 42-45. Osborn, W.J. Associative clustering in organic and familial retardates. Amer. J. Ment. Def., 1960,85, 351-357. Otis, M. A study of associations in defectives. J. edrrc. Psychol., 1915, 6, 271-288. Palermo, D.S. Backward associations in the paired-associate learning of fourth and sixth grade children. Psychol. Reps., 1961,9, 227-233. Palerrno, D. S . Mediated association in a paired-associate transfer task. J . exp. Psychol., 1962, 64, 234-238. Palerrno, D. S., & Jenkins, J. J. Superordinates, “maturity” and logical analyses of language. Psychol. Reps., 1962, 10,437-438. Palermo, D. S., & Jenkins, J. J. Frequency of superordinate responses to a word association test as a function of age. J . verb. Learn. verb. Behav., 1963, 1, 378-383. Palermo, D. S., & Jenkins, J. J. Word association norms: Grade school through college. Minneapolis: Univer. Minnesota Press, 1963 (in press). Reinhold, F. Beitrage zur assoziationslehre auf grund von massenversuchen. Ztsch. f . Psychol. x . Physiol. d . Sinnes, 1910,54, 183-214. Rosanoff, I. R., & Rosanoff, A. J. A study of association in children. Psychol. Rev., 1913, 20, 43-89. Rouse, R. O.,& Verinis, J. S . The effect of associative connections on the recognition of flashed words. J. verb. Learn. verb. Behav., 1963,1, 300-303. Rusk, R. R. Experiments on mental association in children. Brit. J, Psychol., 1910, 3, 349-38 5. Russell, W.A., pc Jenkins, J. J. The complete Minnesota norms for responses to 100 words from the Kent-Rosanoff Word Association Test. Tech. Rep. No. 11. Contract N8-ONR-66216, Office of Naval Research, and Univ. of Minnesota, 1954. Russell, W. A., & Storms, L. H. Implicit verbal chaining in paired-associate leaming. J. exp. Psychol., 1955,49, 287-293. Ryan, J. J. Comparison of verbal response transfer mediated by meaningfully similar and associated stimuli. J. exp. Psychol., 1960,60, 408-415. Saling, G. Associative massenversuche. Ztsch. f . Psychol. u. Physiol. d. Sinnes, 1908, 49, 238-2 5 3. Shambaugh, C. G., & Shambaugh, 0. L. An association study of the vocabulary of grade children. J. educ. Res., 1928,18, 40-47. Shepard, W. 0. The effect of verbal training on initial generalization tendencies. Child Develpm., 1956, 27, 311-316. Spiker, C. C. Stimulus pretraining and subsequent performance in the delayed reaction experiment. J. exp. Psyckol., 1956,52, 107-111. Spiker, C. C. Associative transfer in verbal paired associate learning. Child Develpm., 1960, 31, 73-88. Terman, L. M., & Miles, C. C. Sex and personality: Studies in mascxlinity and femininity. New York: McGraw-Hill, 1936.

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David S. Palerrno Thorndike, E. L. T h e teachers’ word book of 10,000 words. New York: Teachers College, Columbia Univer., 1921. Thorndike, E. L., & Lorge, I. The teachers’ word book of 30,000 words. New York: Teachers College, Columbia Univer., 1744. Traxler, A. E. The relation between rate of reading and speech of association. J . educ. Psychol., 1934, 25, 357-365. Underwood, B. J,, & Schulz, R. W. Response dominance and rate of learning paired associates. J. gen. Psychol., 1960, 62, 153-158. Wheat, L. B. Free associations to common words. New York: Teachers College, Columbia Univer., 1931. Wicklund, D. A. The effects of associative strength and type of response hierarchy on paired-associate learning. Paper presented at the Midwestern Psychological A m . Meetings, 1963. Wimmer, A. Uber assoziationsuntersuchungen, besonders schwachsinniger kinder. Monatsschr. f . Psychol. u. Neural., 1909, 25, 169-268. Wintler, J. Experimentelle beitriige zu einer begabungslehre. Die exp. Pudag., 1906, 2, 193-207. Woodrow, H., & Lowell, F. Children’s association frequency tables. Psychol. Monogr., 1916, 22, No. 5 (Whole No. 9 7 ) . Wreschner, A. Die reproduktion und assoziation von vorstellungen. Ztsch. f. Psychol. II. Physiol. d. Sinnes, Erganzungsband, 1907, 3, 1-557. Wyman, J. B. Tests of intellectual, social, and activity interests. In L. M. Terman (Ed.), Genetic Jtudies of genizrs. Yol. 1. Palo Alto, California: Stanford Univer. Press, 1926. Ziehen, T. Die ideenassoziation des kindes. Berlin: Reuther, 1898 (Sammlung uon abhandlungen aus dem gebiete der pkiagogischen Psychologie and Physiologie, 1898, 1, NO. 6, 1-66).

68

CHANGE I N THE STATURE AND BODY WEIGHT OF NORTH AMERICAN BOYS DURING THE LAST 80 YEARS

Howard V . Meredith INSTITUTE OF CHILD BEHAVIOR A N D DEVELOPMENT STATE UNIVERSITY OF IOWA

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70

11. SECULAR CHANGE IN STATURE . . , . . . . . . . . , A. MEAN STATURE AT BIRTH , . . , . . . . . . . B. MEAN STATURE AT AGES 1 YEAR AND 3 YEARS . . . . C. DISTRIBUTION OF STATURE AT AGE 6 YEARS . . . . . D. STATURE COMPARISONS BY GEOGRAPHIC REGION, RACIAL ANCESTRY, AND SOCIOECONOMIC STATUS . . . . . E. DISTRIBUTION OF STATURE AT SELECTED AGES BETWEEN 9 YEARS AND 16 YEARS . . . . . . . . . . . . F. MEAN STATURE AT AGE 17 YEARS AND IN EARLY ADULTHOOD . . . . . . . . . . . . . . . . . G. GRAPH OF MEAN STATURE CIRCA 1880 AND 1960 . . . .

70 70 72 74

I. INTRODUCTION

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85

89

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IV. POSTSCRIPT REFERENCES

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I. Introduction The North American literature on secular change in body size is a conglomerate of products of fact and by-products of conjecture. Products of fact have helped elucidate the direction and magnitude of somatic change in recent generations. By-products of conjecture have suggested varied determinants and impIications of the changes discovered. This chapter is written to synthesize a major segment of present knowledge regarding the direction and magnitude of secular change in respect to human stature and body weight during the first twenty years of postnatal life. It is delimited to the continent of North America (explicitly, the region of North America between latitudes 2 8 O N and 52O N) and to human organisms of one sex (males). The reader should recognize that extensive research has been done on females (Meredith, 1941a) and in other geographic regions (Tanner, 1961). The predominating objective is substantive synthesis, not historical review. Were the chapter intended to review North American studies of secular change it would provide summaries of reports such as those of Harrington (1910), Gray (1927), MacKinnon and Jackson (1931), Bowles (1932), Chenoweth (1937), Boas (1940), Lloyd-Jones (1940), Deegan (1941), Karlan (1941), Meredith (1941a, 1941b), Michelson (1943a), Meredith and Meredith (1944), Trotter and Gleser (1951), Elbel (1954), Blesh (1956), Binning (1958), Hunt (1958), Hathaway and Foard (1960), and Cone (1961). This it does not do. Rather, drawing freely from the aggregate of investigations on stature and body weight of North America boys, it (1) utilizes original combinations of statistics to derive facts and generalizations more precise than previously available, and (2) aligns statistics not before placed in juxtaposition to reveal new items of knowledge,

11. Secular Change in Stature A. MEANSTATURE

AT

BIRTH

Displayed in Table I are means for stature at birth representing different secular periods between 1870 and 1960. Column 3 lists means derived from North American studies of white boys born at hospitals in Iowa, Minnesota, Missouri, New York, and Pennsylvania. Similar means are obtained for the four periods 1895-1914, 1928-1934, 1934-1952, and 1957-1961. From early poolings of stature data for newborn white infants of both sexes (Meredith, 1943), identical means were secured on 2567 infants measured 1910-1925

70

Change in Stature and Body Weight and on 5123 infants measured 1926-1941. Although no secular change in the stature of white full-term neonates is demonstrable for the present century, the mean in Table I for 1865-1872 does differ significantly from each of the succeeding means ( t exceeding 6.0 in all instances). Regarding the question of uncontrolled variation in socioeconomic composition of the samples, identical means for stature at birth were obtained on 1929-1941 data for 2100 white neonates from the lower classes and 1100 white neonates from the middle and upper classes (Meredith, 1943). The reader should not extend this finding beyond the termination of prenatal life; TABLE I STATURE(CM)OF NORTH AMERICAN BOYS AT BIRTH:MEANSREPRESENTING SPACED TIMESDURINGSECULAR PERIODS OF 90 YEARS (LEFT PANEL) AND 50 YEARS (RIGHT PANEL) -

N

Time ~~

American Negro boys

American White boys

1865-1872’ 330 1895-1918 1231 1352 1928-1934’ 1P~4-1952~ 869 1957-1961’ 218

Time

N

1896-1904’ ca. 1930‘ 1944-1956h

ca. 360 47 385

Mean

~~~~~

Mean

~~

49.4 50.9 50.7 50.7

48.8‘ 49.1 50.0

50.6

Stockton-Hough, 1885. Holt,’1897; Montague and Hollingsworth, 1914. 0 Bakwin and Bakwin, 1934; Meredith and Brown, 1937. d Kasius et al., 1957; Norval et al., 1951. * Westafdd ct al.. 1963. I Riggs, 1904. I Freeman and Platt, 1932. Kasius ct a).. 1957; Kessler and Scott, 1950; Pasamanick, 1946; Scott ct a/., 1962. i The reported mean o f 48.4 cm for American Negro infants of both sexes has been raised to an estimated mean for the male portion of the sample. 0

b

socioeconomic differences in stature are found postnatally (Meredith, 1951). In column 6 of Table I are stature means for newborn Amercan Negro boys. These statistics are based on data gathered at hospitals in Connecticut, District of Columbia, Maryland, New York, and Pennsylvania. There is a statistically dependable difference between the means for 18961904 and 19441956 ( t = 6.5). The technique of measuring stature is less standardized at birth than at later ages. An anthropometric board or table is used in some studies (Bakwin and Bakwin, 1934, Kasius et al., 1957), a tape or anthropometer in others (Montague and Hohgsworth, 1914, Norval et at., 1951). Rarely do research reports on newborn infants carry statements pertaining to extension of the subject’s lower limbs and placement of his head with the tragion-orbitale plane

71

Howard V . Meredith at right angles to the long axis of the body (Meredith, 1960). Neither the 1865-1872 investigation on American white neonates, nor the 1896-1904 investigation on American Negro neonates, includes any specification of the procedure by which “total length” was determined. Assuming methodological comparability, the following hypotheses are tenable statistically: (1) the population mean for white boys born 1957-1961 exceeds that for those born 1865-1872 by an amount between the limits of 0.7 cm and 1.7 cm, and (2) the population mean for Negro boys born 1944-1956 exceeds that for those born 1896-1904 by no less than 0.8 cm.’ Gemrulization. The occurrence of secular rise in the mean stature of North American newborn infants is not documented conclusively. Nonetheless, there are studies on full-term boys of two ethnic groups supporting the position that stature at birth was less in the last quarter of the nineteenth century than in the second quarter of the twentieth century by about 1.0 un (0.4 in.), or 2%. The reader is asked to hold in mind the equivocation of this generalization pending examinaton of section 111, A.

B. MEANSTATUREAT AGES1 YEARAND 3 YEARS Table I1 carries means for stature at the end of the first postnatal year characterizing successive times from 1895 to 1955. Grossly, the samples utilized to obtain the values in column 3 are representative of North American white TABLE I1 STATURE (CM) OF NORTHAMERICAN BOYS AGE 1 YEAR:MEANSAT SPACED SECULAR PERIODS OF 60 YEARS (LEFT PANEL) TIMESDURING AND 32 YEARS(RIGHTPANEL) American White boys

American Negro boys

Time

N

Mean

Time

N

Mean

ca. 1895” 1913-1918b 1929-1940‘ 1947-1962d

343 658 327

73.8 74.2 75.8 76.6

1918-1919’ 1934-1940’ 1944-1956s

85 158 150

71.7 75.3 76.4

~

~

~

Holt, 1897. b G u m , 1916; Rude. 1922. 0 Bakwin c t a/., 1934; Peatman and Higsons, 1938; Poole et al.. 1938; Rhoads et al., 1941; Simmons and Todd, 1938; Vickers and Stuart, 1943. d Kasius et a]., 1957; Knott and Poman, 1963. *Woodbury, 1921. Michelson, 1943a; Poole et ul., 1938; Rhoads et ul., 1941. 0 Kasius er a!., 1957; Pasamanick, 1946; Scott el al., 1962.

8

’All statements regarding magnitude of increase in population means are based on one-tailed tests at the 0.01 probability point. 72

Change in Stuture and Body Weight boys adequately cared for nutritionally and medically. They were drawn at health conferences and nutrition clinics for well children, child development research centers, and in pediatric private practice. Column 3 shows progressive increase in mean stature with time. The difference between the terminal means is 2.8 cm. Unfortunately, the number of subjects used in deriving the initial mean is unknown. Evaluation based on the obtained statistics for 1913-1918 and 1947-1962 supports the hypothesis that the population mean for 1947-1962 was greater than that for 1913-1918 by at least 1.9 cm. Parenthetically, the tabled mean for 1913-1918 is 0.2 cm higher than the mean at age 1 year from 3413 measurements of stature on a cross-section of North American white boys taken in 1918-1919 (Woodbury, 1921). Also for American Negro boys, Table I1 manifests an upward movement of mean stature with time. A small part of the difference between the terminal means in Column 6 may be due to variation of the two samples with respect to postnatal care. Although the subjects studied 1918-1919 were appraised at the time of measurement as neither sick nor malnourished, they were not in a program of dietary supervision. A prudent inference is as follows: in relation to the population mean stature of American Negro boys age 1 year enrolled 1944-1956 in programs of dietary supervision, the run of nonpathological 1-year-old American Negro boys in 1918-1919 had a mean stature shorter by more than 3.7 cm. Means for stature from samples of North American white boys age 3 years are presented in Table 111. The statistics in the two panels differ in TABLE 111 STATURE (CM) OF NORTH AMERICAN WHITEBOYSAGE 3 YEARS:MEANS AT SPACED TIMESDURING SECULAR PERIODSOF 55 YEARS (LEFT PANEL) AND 85 YEARS (RIGHT PANEL) American White boys Time

N

Mean

35 2541 259

90.0 92.9 95.1

Above average economically Time ca. 1855d

ca. 1881a 1918-1919* 1931-1942'

1913-1916' 1920-1930' 1931-19370 1938-1945h

N

Mean

8 76 106 286 126

88.7 94.2 95,6 96.6 97.0

Peckham, 1882. Woodbury, 1921. 6 Rhoads, ef ul., 1945; Tuddenharn and Snyder, 1954; Vickers and Stuart, 1943. 4 Bowditch, 1872. *Gum,1916. I Iowa Child Welfare Research Station, 1931; Wallis, 1931; Wilson et u.., 1930. 0 Bayley and Davis, 1935; Peatman and Higgons. 1938; Simmons and Todd, 1938. Meredith, 1948. a

73

Howard V . Meredith regard to socioeconomic status, those on the right representing higher socioeconomic levels than those on the left. There is a difference of 5.1 cm between the terminal means of column 3. The low value is from data collected ca. 1881 in Wisconsin, and the high value from data collected roughly 5 5 years later in California, Massachusetts, and Pennsylvania, The terminal means of column 6, separated in time by approximately 85 years, differ more than 8.0 cm. Regrettably, the earliest mean is based on few measures. Another mean reported before 1900 (Holt, 1897) is of similar magnitude (89.1 cm), but here the number of measures is unknown. The 1913-1916 mean in column 6 is 2.8 cm lower than the highest mean of 97.0 cm obtained nearly 30 years later. Generalization. Gradual increase during the present century is found for mean stature in late infancy and early childhood. At age 1 year, there is sufficient research foundation to indicate that North American Negro and white boys had a greater mean stature in 1955 than in 1915 by at least 2.0 cm (0.8 in.), or 3%. At age 3 years, North American white boys from homes of middle socioeconomic status were taller on the average in 1940 than in 1880 by no less than 4.0 cm (1.6in.), or 4 . 5 3 .

C. DISTRIBUTION OF STATURE AT AGE6 YEARS The quantity of available research is much greater at 6 years, and later childhood ages, than at ages from 1 year after birth to 5 years. Consequently, comparisons in this and succeeding sections can be broader and more solid. Two problems will be treated at age 6 years: (1) secular change in central tendency of the stature distribution and (2) secular change in variability of the stature distribution. Tables IV and V present statistics pertaining to the first problem. Table IV depicts mean stature at successive times for North American white and Negro boys age 6 years. The white samples were drawn as follows: 1875-1880 in Massachusetts and Wisconsin; 18961900 in the District of Columbia, Illinois, and Nebraska; 1921-1727 in 17 eastern, central, and western states, and the province of Ontario; 1932-1939 in 16 states and the province of Ontario; and 1947-1949 in Pennsylvania. Regional sources of the Negro samples were District of Columbia (1896-1878) ; New York, Tennessee, Virginia, and West Virginia (1915-1928) ; California (1936-1938) ; and Pennsylvania (1957-1958). The statistics for stature at age 6 years in the two panels of Table V characterize white boys from the lower and upper portions of the socioeconomic continuum. In the left panel, the first sample is for sons of unskilled workmen, the second and fourth sampIes are for boys attending schools in economicaIly

74

Change in Stature and Body Weight TABLE IV STATURE(CM) OF NORTHAMERICAN BOYSAGE 6 YEARS:MEANSAT SPACED TIMESDURING SECULARPERIODS OP 70 YEARS(LEFT PANEL) AND GO YEARS(RIGHT PANEL) American White boys Time

N

1875-1880" 189619006 1921-1927' 1932-1939d 1947-1949'

1460 661 2241 11,005 1133

Mean

American Negro boys Time

N

Mean

18961898' 1915-1928P 19361938h 1957-1958'

73 343 173 25

112.3 113.9 115.7 118.6

108.8 111.1

114.2 115 . G 116.0

Bowditch, 1877; Peckham, 1881. Hastings, 1901; MacDonald, 1899; Smedley. 1902. 'Brown, 1926: Collins and Clark. 1929; Keyfirz. 1942; Mustard and Waring. 1926; Schwartz ct al., 1928. d Brown, 1936; Keyfitz, 1942; Lloyd-Jones, 1941; O'Brien et al.. 1941. * Hundley et al., 1955. f MacDonald, 1899. 0 Herskovits, 1930; Mustard and Waring, 1926; Roystn and Hulvey. 1929. h Lloyd-Jones, 1941. Krogman. 1960. 0

b

TABLE V STATURE(CM) OF NORTH AMERICAN WHITEBOYSAGE 6 YEARS:MEANS REPRESENTING SPACEDTIMESDURING A SECULAR PERIODOP 73 YEARS Below average economically

Above average economically

Time

N

Mean

Time

N

Mean

1875-1876" 1918-1927* 1937-1939' 1947-1949d

329 599 1535 446

108.4 110.2 114.0 114.5

l875-187Ga 1921-1927' 1937-1939" 1947-1949d

126 619 1572 687

109.1 115.1 115.7 117.4

Bowditch, 1879. Hundley ct al., 1955; Rude, 1922. c O'Brien er al., 1941. d Hundley et a]., 1955. ' Brown, 1926; Hundleg eta)., 1955. 0

b

underprivileged urban areas, and the third sample is for sons of unskilled and semiskilled workmen. In the right panel, the first sample is drawn from the professional and mercantile occupational groups, the second and fourth samples are from schools in economically favored suburban areas, and the third sample is from the skilled, mercantile, and professional groups. On direction of change, each of the four columns of means in Tables IV and V exhibits increase with time. On magnitude of change, it is shown: (1)

75

Howard V . Meredith differences between the extreme values in columns 3 and 6 of Table IV are equivalent to an increment in mean stature approximating 1.0 cm per decade, and ( 2 ) differences between the terminal means of columns 3 and 6 of Table V are as large for boys from the professional and mercantile classes as for boys from the unskilled and semiskilled classes. Either total displacement of the stature distribution, of extension of the upper part of the distribution, could result in higher mean stature. Both phenomena are manifest in Table VI. The entire stature distribution of 6-year-old boys has moved to the right with time, the movement being slightly greater in the upper TABLE VI STATURE(CM)

OF

NORTHAMERICAN WHITEBOYS AGES6 YEARSAND 6.5

Y E A R S : P A I R E D ROWS OF PERCENTILES FROM SAMPLES SEPARATED IN

Time

N

1892e 1939d

481 3269

1892O 19361938f

709 3880

1875-1876' 1937-193gh

1258 4155

0

TIMEBY 45

Ps

Eb

YEARS T O

E

P2o

62

YEARSa

Pm

E

Age 6 years: Ontario 100.5 104.7 109.2 105.8 5.3 110.0 5.3 114.5 5.3 Age 6 years: Missouri, California 101.8 105.3 109.2 108.2 6.4 112.3 7.0 116.9 7.7 Age 6.5 years: Massachrcsetts, 16 States 103.3 107.4 111.4 109.1 5.8 113.2 5.8 117.6 6.2

Pso

E

Pgg

E

112.7 119.0 6.3

116.6 123.2 6.6

113.5 121.2 7.7

118.3 125.7 7.4

115.7 122.3 6.6

119.7 127.0 7.3

The statistics in each row are independent of those in every other row.

* B symbolizes the amount by which the percentile at the left in a particular row excetdr the corresponding percentile in the preceding row. Boas, 1898. d Keyftz, 1942. 0 Porter, 1894. 0

Lloyd-Jones, 1941. Bowditch, 1891. h O'Brien t f al., 1941. f

u

part of the distribution. Specific differences between paired percentiles separated secularly by about 45 years are found to vary from 5.3 cm to 7.7 cm. All of the statistics in Table VI are derived from large samples of North American white public school boys, and the statistics in each row are independent of those in every other row. The reader will observe that Table VI yields findings other than those cited. For example, it indicates (1) the fifth percentile of the stature distribution for 1940 was larger than the twentieth percentile for 1890, and ( 2 ) the eightieth percentile of the stature distribution for 1890 was smaller than the fiftieth percentile for 1940. Generalization. Six-year-old North American white boys were, on the average, shorter in 1880 than 70 years later by at least 6.7 cm (2.6 in.) or 6.2%. The average 6-year-old North American Negro boy was taller in 1960 than 60 years earlier by more than 5.2 cm (2.0 in.), or 4.8%. N o support is

76

Change in Stature and Body Weight found for the position that stature has increased more among boys from homes below average socioeconomically than among boys from homes above average socioeconomically. The stature distribution for 6-year-old North American white boys has shifted substantially to the right, e.g., the fifth percentile of the stature distribution for 1940 exceeds that for 1890 by no less than 2.0 in.

D. STATURECOMPARISONS BY GEOGRAPHIC REGION,RACIAL ANCESTRY, AND SOCIOECONOMIC STATUS At its outset, this report on the phenomenon of secular change was circumscribed in respect to continent, organism, and sex. Control for ethnic background began in Section 11, A. In Section 11, B, analyses were introduced for subpopulations restricted both ethnically and socioeconomically. In the present section there is control for ethnic descent, socioeconomic level, and geographic locality within North America. Table VII is constructed from statistics for North American white public school boys at ages 7 years, 11 years, and 14 years. Juxtaposed in paired rows are means at spaced times based on measures of stature accumulated in delimited geographic regions. The comparisons are arranged in regional order, proceeding from east to west. For different comparisons, the secular period is between 40 years and 53 years. Attention is directed to observing that every row of differences shows increase in magnitude with age. For instance, the initial pair of investigations yields increases during a period approximating one-half century of 3.9 cm at age 7 years, 5.4 cm at age 11 years, and 7.7 cm at age 14 years. Presented in Tables VIII and IX are means at ages 10 years, 14 years, and 15 years. The first three comparisons in Table VIII are for United States white public school boys. Geographic arrangement is the same as in Table VII, but longer secular periods are spanned. For the 80-year period (Wisconsin-Iowa comparison), a difference in population means at age 14 years can be posited as greater than 12.6 cm, or 5.0 in. The remaining comparisons in Table VIII pertain to white boys from different socioeconomic groups. In the “unskilled” and “professional” comparisons, geographic homogeneity is subordinated to length of secular period (the 18751876 samples were drawn in Massachusetts and the 1950 samples in Oregon). The data from “poor neighborhoods” were amassed 1908-1910 in New York on American-born boys of central European ancestry and 1932-1945 in Minnesota and Ontario on white boys attending schools in underprivileged districts of Minneapolis and Ottawa. Data on boys residing in “good neighborhoods” were secured 1900-1913 in Illinois and 1931-1942 in Minnesota and Ohio. The last two comparisons are based on data gathered in the District of Columbia and immediate vicinity. Boys from the semiskilled and unskilled occupational classes are included in the “below average” samples and boys from

77

Howard V. Meredith TABLE VII STATURE (CM) OP

NORTHAMERICAN WHITE

SCHOOLBOYS: PAIRED R O W S OP SAMPLES SEPARATED I N TIMEBY INTERVALS VARYING B 6 T W E E N 40 Y E A R S A N D 53 YEARS"

MEANSPROM ~~

7 years

Time 1875-1876c 1923-1931d 1891a 1937-1939, 1896-18980 1937-1939, 1892* 1939' 1899-1900i 1 948-1958k

ca. 1880' 1923-1924'" 18861890n 1937-1939, 19161919' 1961-1962P 18929 1937-1939' 1898-1899' 1937-1939' 1892' 1936193fY

N

Mean

14 years

11 years

N

Eb

Mean

E

52 years: Masfachusetts 1338 113.7 1328 133.4 473 117.6 3.9 709 138.8 5.4 47 years: Massachusetts, Pennsylvania 160 115.4 248 135.1 271 119.9 4.5 340 139.9 4.8 41 years: District of Columbia and vicinity 533 116.8 862 135.2 466 120.9 4.1 593 140.7 5.5 47 years: Ontario 729 113.9 828 133.7 4080 120.4 6.5 4470 140.7 7.0 53 years: Illinois, Pennsylvania 228 115.8 241 135.1 90 120.7 4.9 175 143.6 8.5 43 years: Wisconsin, North Central States 569 115.3 531 134.3 515 140.1 5.8 492 120.0 4.7 50 ?ears: Missouri, Iowa 465 135.2 527 140.5 5.3 44 years: Missouri, Iowa 332 138.2 78 144.7 6.5 46 years: Missouri, Kansas 1850 114.0 1819 133.8 270 120.2 6.2 356 141.3 7.5 40 years: Nebraska, Colorado 544 115.7 660 134.9 280 119.8 4.1 385 140.7 5.8 4> years: California 171 115.9 225 135.7 4529 122.4 6.5 5471 143.0 7.3

N

Mean

E

1034 148.7 711 156.4

7.7

240 151.2 445 156.7

5.5

1005

784 150.1 158.2

8.1

491 148.4 2905 156.4

8.0

240 151.9 73 164.4 12.5 279 149.1 468 155.7

6.6

404 148.8 198 156.7

7.9

265 152.8 97 163.7 10.9 925 148.6 455 157.6

9.0

435 151 . O 311 157.1

6.1

173 151.9 5398 160.6

8.7

The statistics in each row are independent of those in every other row. symbolizes the amount by which the adjacent mean in a particular row uxccuds the mean at the same age in the preceding row. Peckham, 1881. 0 Bowditch. 1877. m Palmer and Collins. 1935. 1 Shutdeworth, 1939. n Greenwood, 1891. Boas and Wissler, 1905. f O'Brien et al.. 1941. 0 Pylc, 1920. P Knott and Meredith. 1962. 0 MacDonald, 1899. * Boas, 1898. Porter. 1894. Keyfirz, 1942. Hastings, 1901. i Smedley, 1902. Boas, 1895. 6 Lloyd-Jones, 1941. Kroeman. 1960.

0

bB

'

*

78

Change in Stature and Body Weight TABLE VIII

STATURE(CM) OF NORTHAMERICAN WHITE SCHOOLBOYS: PAIREDRows MEANSFROM SAMPLESSEPARATED IN TIMEBY INTERVALS VARYING BETWEEN30 YEARS A N D 80 YEARS ~~

Time 1875-1876" 1948-1958b

ca. 188OC 1961-1962d 1892' 1957-1958f 1875-1876' 1950' 1875-1876O 1950' 19O8-191Oh 1932-1945' 1900-1913' 1931-1942b 1896-1898t 1937-1939m 1896-1 898* 1937-193grn

N

Mean

b

~~

~~

N

E

Mean

15 years

E

77 years: Massachusetts, Pennsylvania 1400 128.8 1034 148.7 187 139.6 10.8 73 164.4 15.7 80 years: Wisconsin, Iowa 279 149.1 97 163.7 14.6 65 years: Calihrnia, Oregon 173 151.9 23 1 130.9 30 164.8 12.9 86 138.6 7.7 74 years: Fathers in unskilled occupations 380 128.9 40 137.8 8.9 7 4 years: Fathers in profissional occupations 27 130.6 43 140.7 10.1 30 years: Homes in poor neighborhoods 113 149.8 105 130.3 99 157.1 7.3 330 134.7 4.4 30 years: Homes in good neighborhoods 124 155.5 78 135.9 214 164.0 8.5 394 140.3 4.4 41 ytars: Families below average economically 350 130.3 231 149.1 201 134.9 4.6 192 155.6 6.5 41 years: Families above average economically 353 132.1 358 151.6 392 136.8 4.7 787 158.9 7.3

Bowditch, 1877. Krogman, 1960. a Peckham, 1881. d Knott and Meredith, 1962. Boas, 1895. I Degutis, 1960; Harrison. 1959; Irving, 1959. 0

~

14 years

10 years

OF

N

Mean

E

159 155.2 79 168.6 13.4 140 158.9 51 170.7 11.8

84 163.1 150 171.1

8.0

Meredith, 1951. Boas, 1911. i Hopkins, 1947; Weisman, 1935. I Bddwin, 1914. k Simmons, 1944; Weisman, 193% 1 MacDonald. 1899. m O'Brien et al., 1941. A

the professional and mercantile classes in the "above average" samples. Similar secular change for different portions of the socioeconomic continuum is apparent. Augmenting the materials displayed in Table VIII are the following findings from studies made in orphanages and private schools. At ages between 7 years, and 1 2 years, boys admitted to the Hebrew Orphan Asylum, New York, averaged 3.1 cm shorter for the period 1905-1917 than for the period 1918-1928

79

Howard V . Meredith (Boas, 1935). At ages between 10 years and 1 5 years, boys attending private schools in Pennsylvania 1889-1893 (Hall, 1896) averaged 7.1 cm shorter than boys attending private schools in several states 1920-1930 (Gray and Ayres, 1931). Compared with boys at private schools in Massachusetts 1875-1876 (Bowditch, 1877), boys at a private school in Iowa 1930-1937 (Meredith, 1941a) were taller at ages between 11 years and 15 years by an average of 7.8 cm. Secular comparisons controlled from geographic region are presented in Table IX on several North American ethnic groups. In respect to American TABLE IX STATURE(CM)OF NORTHAMERICAN SCHOOLBOYS: PAIREDRows MEANSFROM SAMPLES SEPARATED IN TIMEBY INTERVALS VARYING BETWEEN 22 YEARS AND 61 YEARS 10 years

Time

N

Mean

14 years

E

Mean

N

OF

15 years

E

N

Mean

E

61 years: American Negro: District of Columbia, Massachusetts and Pennsylvania 18961898° 335 129.8 1957-1959b 77 136.9 7.1 48 years: American Negro: Missouri, Kansas 1886-l9OOc

1936-1937d 1921-1923" 195619571 1930-1932g 19561957, 1926-1927h 1958-1959i 1908-1910j 1930-1932A 1908-1910 i 1938-1939h 1931-1933' 1957-1958^

80

148.4 156.9

8.5 34 years: American Japanese: Washington, California 28 128.3 33 132.0 3.7 21 years: AmericanJapanese: California 98 130.3 48 154.8 33 132.0 1.7 34 159.3 4.5 32 years: American Italian: Masachusetts 111 130.3 54 136.3 6 . 0 22 years: American Italian: New York, Massachusetts 175 144.8 113 83 152.7 7.9 81 30 years: American Bohemian, Pinn: New York,MinneJota 92 130.6 99 150.1 92 137.0 6 . 4 93 158.5 8 . 4 21 years: American Dutch: Michigan 149 96

MacDonald, 1899. Krogrnan, 1960; Piscopo, 1962. 8 Greenwood, 1891. d McLendon, 1937. a ~pier,'I1929. f Greulich, 1957. a. Preston, 1936; Suski, 1933. a

50 120

h Dearborn ct al., i Piscopo, 1962.

1938.

I Boas, 1911.

Matheny and Meredith, 1947. I Spurgeon d U / . ~1959. m

Steggerda and Densen. 1936.

149.5 159.0

9.5

168.6 171.6

3.0

Change in Statzlre and Body W e i g h t Negro, Japanese, Bohemian, Finn, and Dutch boys, statistics were drawn routinely from the sources indicated. An explanatory note on the two comparisons for boys of Italian ancestry is obligatory. The 1958-1959 mean in the one comparison is for boys from the lower and middle classes, while the 19081910 means in the other comparison are for boys from the lower classes. Utilizing data from Dearborn et al. (1938), it was possible to obtain means on boys of Italian ancestry by combining (1) occupational groups 111, IV, and V for alignment with the 1958-1959 mean, and ( 2 ) occupational groups IV and V for alignment with the 1908-1910 mean. T o the secular increases in stature exhibited in Table IX may be added findings for shorter periods on American Indian and Mexican boys. Stature means on public school boys of Mexican descent are available at ages 9.5 years and 12.5 years from data collected 1924-1925 in Arizona (Paschal and Sullivan, 1925) and 1936-1938 in California (Lloyd-Jones, 1941). The means for 1936-1938 exceed those for 1924-1925 by 2.7 cm and 4.4 cm, respectively. Writing in reference to the entire period between ages 6 years and 18 years, Steggerda and Shaffer (1942) report that stature means for Navajo boys measured in New Mexico and Arizona averaged 1.2 cm less in 1932-1934 than in 1941. Generalization. Juxtaposition of statistics at ages between 7 years and 1 5 years show (1) there has been secular increase in mean stature for North American boys of varied ethnic backgrounds (Negroid, Mongoloid, and Caucasoid), varied socioeconomic classes (unskilled to professional), and varied geographic localities (east coast to west coast), also ( 2 ) the increase has been greater for middle childhood than early childhood, and greater for early adolescence than middle childhood.

E. DISTRIBUTION OF STATURE AT SELECTED AGES BETWEEN9 YEARS AND 16 YEARS This section provides a chronological extension of Section 11, C. Its content (1) illustrates secular changes for different portions of the stature distribution in late childhood and adolescence, and ( 2 ) estimates the magnitude of secular change in mean stature at two ontogenetic points, i.e., ages 10 years

and 15 years. Percentiles characterizing the stature distribution at or near age 10 years are brought together in Table X. Secular displacement is greater than at age 6 years. The minimum and maximum E values (positive changes) are 5.9 cm and 9.1 cm, respectively. For three of the paired-row comparisons, those in which sample size exceeds 500, change is smaller at the lower end of the distribution than at the upper end. Explicitly, for North American white boys age 10 years,

81

Howard V . Meredith it can be inferred that during the one-half century following 1890: (1) the twentieth percentile of the stature distribution increased no less than 6.5 cm, or 2.5 in., and (2) the eightieth percentile of the stature distribution increased no less than 7.5 cm, or 3.0 in. Assembled in Table XI are percentiles for stature at ages from 14 years to 15.5 years. The two comparisons at age 14 years, in common with findings at ages 6 years and 10 years, show larger change at the right tail of the distribuTABLE X STATURE(CM) OF NORTH AMERICAN WHITEBOYS AGES9.5 YEARSAND 10 YEARS: PAIREDROWS OP PERCENTILES FROM SAMPLES BY 45 YEARS T O 62 YEARS5 SEPARATED I N TIME Time

N

1875-1878 1937-1939'

1437 6242

1892d 1939'

865 4437

1892f 19361938'

2087 5140

P6

E

P2o

E

P~oE

Pso

E

Po6

E

Age 9.5 years: MasJachuJettJ, I6 states

1891h 19SOi

256 208

117.9 123.8 5 . 9

122.0 126.4 128.6 6 . 6 133.7 7 . 3 Age 10 years; Ontario 123.7 128.7 118.9 131.0 7 . 3 136.1 7 . 4 126.2 7 . 3 Age 10 yearJ: MiJJOHri, California 120.0 124.6 129.5 133.1 8 . 5 138.3 8 . 8 128.3 8 . 3 Age 10 years: MassachuJetts, Oregon 121.3 125.2 130.3 129.8 8 . 5 134.1 8 . 9 138.8 8 . 5

131.1 138.9 7 . 8

135.8 144.2 8 . 4

133.4 141.4 8 . 0

138.4 146.4 8.0

134.5 143.4 8 . 9

139.5 148.6 9 . 1

135.2 143.4 8 . 2

140.7 148.7 8 . 0

The statistics in each row are independent of those in every other row. Bowditch. 1891. !Porra. 1894. O'Brien nf al., 1941. 0 Lloyd-Jones, 1941. d Boas, 1898. 6 Boas and Wissler, 1905. Keyfitz, 1942. 6 Meredith and Meredith. 1953. 0

b

tion than at the left tail. This differential is reversed by age 1 5 years. Each of the comparisons at ages 1 5 years and 15.5 years exhibits greater secuIar shift for the lower part of the distribution than for the upper part. In respect to the table as a whole, from each of the six comparisons it is found: (1) the twentieth percentile at the earlier time is lower than the fifth percentile at the later time, and (2) the eightieth percentile at the later time is higher than the ninetyfifth percentile at the earlier time. Table XI1 presents composite means for successive secular periods typifying stature at age 10 years of North American white and Negro boys. The data on white boys were amassed 1875-1880 in Massachusetts and Wisconsin; 18961900 in the District of Columbia, Illinois, and Nebraska; 1921-1931 in 20 eastern, central, and western states, also the province of Ontario; 19361940 in 16 states and the provinces of Ontario and Saskatchewan; and 1948-1958

82

Change in Statwe and Body Weight in Pennsylvania, Iowa, Oregon, and Saskatchewan. Collection of the data on American Negro boys took place 1886-1898 in the District of Columbia, and Missouri; 1915-1928 in New York, Tennessee, Virginia, and West Virginia; 1929-1938 in California and Texas; and 1957-1959 in Massachusetts and Pennsylvania. The means in the left panel of Table XI1 ascend from 129.0 cm for 18751800 to 138.3 cm for 1948-1958. It is tenable statistically to infer that the

TABLE XI STATURE(CM) OF NORTHAMERICAN WHITE BOYS AGES14 YEARS TO 15.5 YEARS: PAIREDRows OF PERCENTILES FROM SAMPLES SEPARATED IN TIME BY 45 YEARS T O 70 YEARSa

1892* 1939" 1892d 19361938' 1887-1895' 1961-1962' 1891A 1936-1938e 1892d 1961-19620 1875-1876' 1937-1939"

Age 14 years: Ontario 140.9 147.6 504 134.5 2905 142.2 7.7 148.9 8.0 156.3 8.7 Age 14 years: Missouri, Caltifornia 142.3 148.9 925 137.1 5418 146.6 9.5 153.2 10.9 160.7 11.8 Age 14.S years: Maryland, lowa 150 135 . O 143.1 149.5 72 152.3 17.3 161.4 18.3 169.0 19.5 Age 15 years: Massachusetts, California 182 142.3 150.4 159.2 5242 152.0 9.7 159.4 9.0 167.0 7.8 Age 15 years: Missouri, Xowa 155.3 147.5 490 140.9 79 159.0 18.1 163.0 15.5 169.1 13.8 Age 15.5 years: Mas~achusett~,'l6States 151 .O 158.4 636 143.6 4700 153.7 10.1 161.2 10.2 168.3 9.9

The statistics in each row are independent of those in every other row. .Lloyd-Jones, 1941. Keyfitz. 1942. Moon, 1895. D Knott and Meredith, 1962. d Porter. 1894.

162.4 154.5 164.5 10.0 171.5 9.1 155.8 162.9 168.1 12.3 174.9 12.0 156.8 166.1 174.6 17.8 181.4 15.3 165.8 171.9 173.3 7.5 179.0 7.1 163.5 170.4 174.4 10.9 179.7 9.3 166.3 172.5 174.4 8.1 180.3 7.8

a

Boas, 1898.

Boas and Wissler, 1905. 1891. i OBrien ct a)., 1941.

b

iBowditch,

average stature of North American white boys age 10 years increased more than 8.7 an, or 3.4 in., during the 75 years beginning 1880. The right-panel means from N's exceeding 100 are consistent for direction and magnitude. Average stature of North American Negro boys age 10 years rose more than 6.0 cm, or 2.4 in., during the 50 years beginning 1890. Displayed in Table XI11 are means for stature at age 1 5 years. The 18521886 mean for white youths typifies a broad geographic sample composed mainly of candidates for service on the United States steamer Minnesota and

83

Howard V . Meredith TABLE XI1 STATURE(CM) OF NORTHAMERICAN BOYS AGE 10 YEARS:MEANS AT SPACED TIMESDURINGSECULAR PERIODS OF 75 YEARS (LEFTPANEL)AND 66 YEARS(RIGHTPANEL) American White boys

American Negro boys

Time

N

Mean

Time

N

Mean

1875-1880n 1896-1900h 1921-1931' 193G1940d 1948-1958'

1943 1667 6301 16,164 1001

129.0 131.2 133.8 136.7 138.3

188618981 1915-1928" 1929-1938h 1957-195gi

374 760 360 77

129.7 133.8 136.6 136.9

~~

~

~

~

~

Bowditch, 1877; Peckham, 1881. b Hastings, 1901; MacDonaId, 1899;Smedley, 1902. 'Brown, 1926; Collins and Clark. 1929; Keyfitz, 1942; Mustard and Waring. 1926; Schwartz et al., 1928;Whitacre, 1939. d Binning, 1958; Keyfitz, 1942; Lloyd-Jones, 1941; OBrien rf a/., 1941; Wolff, 1942. 8 Binning, 1958; Deputis, 1960; Eppright and Sidwell. 1954; Krogrnan, 1960; Meredith and Meredith, 1953. I Greenwood, 1891; MacDonald. 1899. Herskovits, 1930;Mustard and Waring, 1926;Royster and Hulvey, 1929. * Lloyd-Jones, 1941; Whitacre, 1939. 6 Krogman, 1960;Piscopo, 1962.

0

TABLE XI11 OF NORTHAMERICAN YOUTHS AGE 15 YEARS: MEANS AT SPACED TIMESDURING SECULAR PERIODS OF 87 YEARS (LEPT PANEL) AND 40 YEARS (RIGHT PANEL)

STATURE (CM)

American White youths

N

Time ~

1852-1886" 1890-1900b 1911-1919' 1930-1940d 1950-1962'

Mean ~

2595 2054 946 13,775 268

American Negro youths Time ~

154.6 157.1 158.8 164.6 169.0

1886-1898' 1915-1928" 1927-1938h

N

Mean ~

266 352 504

~~

153.2 159.2 164.2

Bowditch, 1877; Cordeiro, 1887; Gihon, 1880;Peckham, 1881. Boas, 1895; Boas and Wissler, 1905; Hastings, 1901; Greenwood, 1891; MacDonald, 1899;Porter, 1894; Srnedley. 1902. c Pyk, 1920; Woolley. 1926. d Brown. 1936; Keyfitz. 1942; Lloyd-Jones, 1941;OBrien 8 t al., 1941;Wolff, 1942. Eppright and Sidwell, 1954;Harrison, 1959;Knott and Meredith, 1962;Newcomer and Meredith, 1951. Greenwood. 1891; MacDonald, 1899. 0 Herskovits, 1930;Mustard and Waring. 1926; Roysrer and Hulvey, 1929. Beckham, 1938; Lloyd-Jones, 1941; McLendon. 1937;Whitacre, 1939. a

b

Change in Stature and Body Veight candidates for admission to the United States Naval Academy. The succeeding means in column 3 are from data amassed 1890-1900 on school youths in California, District of Columbia, Illinois, Massachusetts, Missouri, and Nebraska; 1911-1919 on school and employed youths in Missouri and Ohio; 1930-1940 on school, camp, and club youths in 17 states and provinces, with heavy representation of California, Maryland, Ontario, and Utah; and 1950-1962 on school youths in Iowa and Oregon. Accumulation of the measures on American Negro boys took place 1886-1898 in the District of Columbia and Missouri; 1915-1928 in New York, Tennessee, Virginia, and West Virginia; and 19271938 in California, District of Columbia, Illinois, Kansas, New York, and Texas. Table XI11 provides the bases for inferring: (1) the average North American Negro youth age 1 5 years was shorter in 1890 than 40 years later by no less than 9.5 cm, or 5.8r/,, and (2) the average North American white youth age 15 years was taller in 1955 than 85 years earlier by no less than 13.1 cm, or 8.5%. Generulizution. During the last several decades there has been secular increase in the stature of North American Negro and white males, its magnitude rising with age from early childhood into adolescence. The rise in magnitude continues to age 14 years for the eightieth percentile of the stature distribution, and beyond age 1 5 years for the twentieth percentile. Between 1870 and 1955 the North American white male age 1 5 years became taller by 5.2-6.2 in. in absolute mean stature, or 8.5-10.1% in relative mean stature.

F. MEANSTATUREAT AGE 17 YEARS AND

IN

EARLYADULTHOOD

Table XIV lists means for stature on North American youths 17 years of age. The 1852-1886 mean for white youths represents a wide geographic sample comprised largely of candidates for service on the United States steamer Minnesota and candidates for admission to the United States Naval Academy. The succeeding means in column 3 are from data gathered 1896-1900 on school youths in the District of Columbia, Illinois, and Missouri; 1911-1919 on school and employed youths in Missouri and Ohio; 1936-1944 on school, camp, and d u b youths, also United States Selective Service inductees; and 19451958 on United States Selective Service inductees, and youths participating in longitudinal investigations of normal human development. Care has been taken to avoid underestimating the mean for 1945-1958. Karpinos (1961), studying United States Selective Service registrants measured 1957-1958, obtained a mean stature of 171.2 cm on 1560 inducted and disqualified youths between ages 17 years and 18 years. Lowest and highest means for white youths differ by 14.4 cm in Table XI11

85

Howard V . Meredith and by 7.0 cm in Table XIV, indicating decrease in magnitude of secular change following age 1 5 years. It is a reasonable inference that human stature for the average North American white male age 17 years was greater in 1950 than 80 years earlier by an amount neither less than 6.2 cm (2.4 in.) nor more than 7.3 cm (2.9 in.). In column 6 of Table XIV are statistics on North American Negro youths 17 years of age. These statistics allow acceptance of the hypothesis that mean stature for American Negro youths age 17 years was less in 1920 than in 1960 by a minimum of 4.3 cm (1.7 in.). The subjects for 1915-1926 were TABLE XIV STATURE (CM) OF NORTH AMERICAN YOUTHS AGE 17 YEARS: MEANS AT SPACED TIMES DURING SECULAR PERIODS OF 82 YEARS (LEFT PANEL) AND 37 YEARS(RIGHT PANEL)

American White youths

American Negro youths

Time

N

Mean

Time

N

Mean

1852-1886a 1890-1900b 1911-1919c 1936-19444 1945-1958'

3069 394 578 10,002 1199

165.3 166.6 168.6 172.3 172.0

1915-1926' 1934-19410 1957-1958h

55 941 490

165.4 170.8 171.9

Bowditch, 1877; Cordeiro, 1887; Gihon. 1880; Peckham, 1881.

'Greenwood, 1891; MacDonald, 1899; Porter. 18%; Smedley, 1902. * Pyk. 1920; Wooky, 1926.

Lloyd-Jones, 1941; O'Brien ct d., 1941; Randall, 1949; Wolf€, 1942. rKarpinos, 1961; Maresh, 1955; Reed and Stuart, 19S9; Tuddenham and Snyder, 19S4. Herskovits, 1930. D Lloyd-Jones, 1941; Michelson. 1943a. Karpinos, 1961.

school youths, those for 1934-1941 largely enrollees in the United States Civilian Conservation Corps, and those for 1957-1 958 United States Selective Service registrants. Exhibited in Table XV are two columns of stature means on North American white men 20 years of age. The measures for those in column 3 were obtained 1852-1880 on candidates for admission to the United States Naval Academy and American-born men in the United States armed services (soldiers and sailors) ; 1885-1900 on men residing in Connecticut, Nebraska, and Massachusetts; 1942-1947 on United States army separatees; and 1957-1958 on men inducted for military service. Recognizing that the 1852-1880 sample excludes men unaccepted for defense service, comparative use is made of the mean for 1957-1958 inductees rather than the lower 1957-1958 mean of 173.9 cm for

86

Change in Stature and Body Veight inductees and disqualified United States Selective Service registrants (Karpinos, 1961). The measures for the means in column 6 were accumulated 1861-1891 at Amherst College; 1908-1917 at the University of Kansas; 1928-1930 at 10 universities in California, Connecticut, Minnesota, New Jersey, New York, Ohio, Texas, and Wisconsin; and 1947-1952 at more than 100 colleges and universities in 34 states, the District of Columbia, and the province of Ontario. From the assembled statistics of Table XV it is tenable to infer that at age 20 years (1) the average North American white male was taller in 1960 than TABLE XV STATURE (CM) OF NORTH AMERICAN MENAGE 20 YEARS: MLiANS AT SPACED TIMESDURINGSECULAR PERIODS OF 91 YEARS (LEFT PANEL) AND 73 YEARS(RIGHTPANEL) American White men

American White college men

Time

N'

Mean

Time

N

Mean

1852-1880' 1885-1900* 1942-1 947" 1957-1958d

88,328 736 2258 9833

171.6 172.2 173.6 174.7

1861-1891' 1908-191'7 1928-1930s 1947-1952."

270 485 3613 11,899

173.2 173.6 174.7 176.8

Baxter, 1875; Gihon. 1880; Gould. 1869. Hastings, 1901. c RandaI1.'1949. d Karpinos, 1961. Hitchcock, 1892. f Elbel. 1954. @ Diehl, 1933. Elbel, 1954; Hathawai and Foard, 1960; Sturzebecker, 1950. 4

b

*

90 years earlier by an amount within the interval from 2.9 cm to 3.3 un, or 1.1 in. to 1.3 in., and (2) the average North American white college male was taller in 1950 than 75 years earlier by an amount within the limits of 2.6 cm and 4.6 cm. On American Negro men 20 years of age, Gould (1869) obtained a 1861-1865 mean of 168.2 cm for 3648 United States soldiers and sailors, Michelson (1943a) a 1933-1941 mean of 172.1 cm for 1309 enrollees in the United States Civilian Conservation Corps, and Karpinos (1961) a 1957-1958 mean of 174.2 cm for 1421 United States Selective Service inductees. Studies at Yale University (Deegan, 1941) and the University of Kansas (Elbel, 1954) have shown that the relative frequency of male students with statures 182.7 cm or higher (72 in. or above) was near 6% prior to 1910, and approximately 19% in the period 1935-1950. Of the stature records amassed by the American College Health Association on 92,353 college men measured

87

Howard V . Meredith 1948-1950, 24% were in the category “72 in. or above” (Hathaway and Foard, 1960). Using a largely underprivileged sample, Karlan (1941) found that men admitted to a New York prison 1910-1925 had a mean stature dependably lower than men admitted 1925-1940. Additional documentation on the magnitude of stature increase in early adulthood may be drawn from statistics pertaining to the fifth quinquennium of postnatal life. For the nineteenth century, stature means on American-born white men between the age limits of 20 years and 25 years are 172.7 cm from 318,409 soldiers and sailors in the United States armed services 18611865 (Gould, 1869), 172.3 cm from 52,393 United States army recruits measured 1863-1864 (Baxter, 1875) and 171.8 cm from 20,636 United States army recruits measured 1892-1897 (Sternberg, 1892, 1898). Compared with the mean of 175.2 cm from Karpinos (1961) on 89,012 white men 20-25 years of age inducted in the United States armed forces 1957-1958, these three values for the period between 1860 and 1900 are lower by 2.5 cm, 2.9 cm, and 3.4 cm, respectively. Intermediate means of 173.3 cm, 173.3 cm, 174.2 cm, and 174.3 cm have been reported by Bean (1931) on 594 third-generation residents of Virginia measured 1918-1930, Karpinos (1958) on 119,433 United States Selective Service registrants during 1943, Randall (1949) on 5985 United States World War I1 separatees measured 1945-1948, and White (1956) on 2650 American-born man separated from the United States armed services in 1946. The mean from White is based on data for white men age 25 years, the other means are from data for the quinquennium between 20 years and 25 years. Recent efforts to derive population estimates for mean stature of white men 20-25 years of age include a North American synthesis for circa 1955 (Stoudt et al., 1960) and a 1953 Canadian survey (Pett and Ogilvie, 1957). The larger of these estimates (174.5 cm) exceeds the lowest of the means prior to 1900 (171.8 cm) by 2.7 cm. Stature means on American Negro men 20-25 years of age are 169.4 cm for 14,620 soldiers and sailors in the United States defense forces 18611865 (Gould, 1869), 169.7 cm for 5960 United States army inductees measured 1863-1864 (Baxter, 1875), 170.8 cm for 1479 United States army inductees measured 1892-1897 (Sternberg, 1893, 1898), 172.5 cm for 22,370 United States Selective Service registrants measured 1943 (Karpinos, 1958), and 175.0 cm for 10,389 United States Selective Service inductees measured 19571958 (Karpinos, 1961). The rise during the 95-year period encompassed is 5.6 cm, indicating greater secular increase in early adult stature for American Negro men than for American white men. Generalization. Research on North American human males shows that between age 15 years and early adulthood there is progressive reduction in the magnitude of secular increase in stature. Compared with mean stature for North

88

Change in Stature and Body Weight American white males in 1875, mean stature in 1960 is found to be (1) higher at age 15 years by not less than 13.1 cm ( 5 . 2 in.), or 8.5%, and (2) higher in early adulthood by not more than 3.4cm (1.3 in.), or 2.0%.

G. GRAPHOF MEAN STATURE

CIRCA 1880 AND

1960

Major findings of Section I1 in respect to mean stature are summarized schematically in Fig. 1. It is left for the reader to study this graphic condensation and cross-check its contents. In lieu of an epitomizing statement on secular change in the distribution of stature, further perusal of Tables VI, X, and XI is recommended.

111. Secular Change in Body Weight A. MEANBODYWEIGHT IN INFANCY This section pertains to secular change in the mean body weight of North American male infants. Two ethnic groups are considered at each of two infancy ages. Table XVI has been compiled to represent full-term males at birth. The means of column 3 are based on data accumulated at hospitals in Florida, Iowa, TABLE XVI BODYWEIGHT (KG) OF NORTH AMERICAN FULL-TERM BOYS AT BIRTH:MEANS REPRESENTING SPACED TIMES DURING SECULAR PERIODS OF 79 YEARS (LEFT PANEL) A N D 51 YEARS (RIGHT PANEL)

American W h i t e boys

American Negro boys

Time

N

Mean

1865-1895" 1895-1906b 1928-1 945" 1957-1961d

830 701 3589 146,969

3.43 3.44 3.45 3.48

c

Time

N

189C~1904~ ca. 360 1915-1931f 206 1935-1947' 6897 1947-1956h 1179

Mean 3.13% 3.25 3.36 3.25

Stockton-Hough, 1885; Townsend, 1896.

* Griffith and Gittings, 1907; Holt, 1897.

Anderson er a[., 1943; Bakwin and Bakwin, 1934; Cares and Goodwin. 1936; Meredith and Brown, 1939; Norval era[., 1951; Rhoads er al.. 1945. d Baltimore City Health Department, 1957: Florida State Board of Health, 1961; Ohio Department of Health, 1960. e Riggs. 1904. Bakwin, 1932; Baldwin, 1921; Freeman and Platt. 1932. 0 Anderson el a[., 1943; Michelson. 1943b; Rhoads et al.. 1945; Scott et af.. 1950h. h Crump er a[., 1957; Kasius cr a[., 1957; Scott eta[.. 1962. I The reported mean of 3.07 kg for American Negro infants of both sexes has been raised to an estimated mean for the male portion of the sample.

89

Howard V.Meredith

Pig. 1. Schematic curues of mean stature for 1880 and 1960. Inset shows differences between the curues at selecied ages.

90

Change in Stature and Body Weight Maryland, Massachusetts, Minnesota, Missouri, New York, Ohio, Pennsylvania, and the province of Ontario. Data for the means in column 6 were amassed at hospitals in the District of Columbia, Maryland, New York, Ohio, Pennsylvania, and Tennessee. In respect to North American white neonates, an appropriate statistical test allows the inference that the two means tabled for 1865-1895 and 19571961 represent different populations. However, the difference might be due to variation of the criterion used in determining “full-term.” None of the studies between 1865 and 1906 specify the “full-term” criterion employed. Criteria that have been used widely are (1) “birthweight 2.0 kg or above” and (2) “birthweight 2.5 kg or above.” The 1957-1961 sample yields means of 3.43 kg from application of criterion 1 and 3.48 kg from application of criterion 2. It follows that a secular rise in body weight is obtained by assuming the use of criterion 1 in the early studies, but not obtained by assuming the use of criterion 2 in these studies. For North American Negro neonates, the 1947-1956 mean is dependably higher than the 18961904 mean. A significant difference is obtained both for the means as tabled, and when the 18961904 mean is raised to 3.18 kg on the assumption this adjustment is necessary to make the two samples comparable in definition of “full-term.” Considering the two ethnic groups together, an over-all trend of secular increase in average size at birth can be demonstrated no more definitively for body weight than for stature (Section 11, A ) . Presented in Table XVII are means for body weight at the close of the first postnatal year. The means in column 3 are representative of North American white boys given reasonably adequate nutritional and health care. In the main, they are derived from samples drawn at well-baby clinics sponsored by city hospitals or health departments, child development research centers, health conferences on infant care, and in pediatric private practice. This selection is quantitatively attested by comparison of the tabled mean for 1913-1918 with the mean of 9.48 kg at age 1 year obtained by Woodbury (1921) from 3413 measures on a cross-section of North American white boys weighed 1918-1919. The means in column 6 are from grossly comparable samples, except that the sample for 1914-1920 is less homogeneous than the later samples in respect to competent nutritional guidance. As for stature at the same age (Table II), both series of means increase systematically with time. Statistical evaluation indicates that the population mean weight for white boys was less in 1895 than in 1955 by at least 0.9 kg, or 9.070. Generalization. It is not possible to make a decisive statement on whether mean birth weight of North American boys is higher today than it was in the last quarter of the nineteenth century. The affirmative position has support

91

Howard V . Meredith from findings on American Negro boys, but is not clearly supported by findings on American white boys. At age 1 year, secular increase in the mean body weight of North American white and Negro boys is documented beyond reservation. White boys under pediatric guidance were heavier in 1955 than in 1895 by an average amount between 0.9 kg (2.0 Ib) and 1.4 kg (3.1 lb).

TABLE XVII (KG) OF NORTH AMERICANBOYS AGE 1 Y E A R : MEANS AT SPACED TIMES DURING SECULAR PERIODS OF 59 YEARS (LEFT PANEL) AND 34 YEARS(RIGHT PANEL)

BODY WEIGHT

~

~~

American Negro boys

American White boys

Time ca. 1895" 1913-1918b 1929-1 940' 1947-1962d

N

Mean

ca. 200 343 750 407

9.29 9.77 10.33 10.39

Time

N

Mean

1914-1920' 1932-1940f 1940-1947' 1947-1956h

200 305 365 139

8.71 9.91 10.30 10.35

Halt, 1897. Gum, 1916; Rude, 1922. c Bakwin, e: ai.. 1934; Kelly and Reynolds, 1947; Peatman and Higgons, 1938; Rhoads 8f ul., 1945; Simmons and Todd, 1938; Vickers and Stuart, 1943. dKasius et al., 1957; Knott and Foman, 1963; Bueda-Williamson and Rose, 1962; Westerfdd er al., 1963. *Baldwin, 1921; Dodge, 1927; Woodbury, 1921. I Kelly and Reynolds, 1947; Michelson, 1943b; Rhoads et al., 1945. I Bakwin and Patrick, 1944; Pasmanick, 1946; Scott cr #I.. 1950a. 6 Kasius etal., 1957; Scott et al., 1962. a

b

B. MEAN BODYWEIGHT

IN

EARLYCHILDHOOD

Means for body weight from samples of North American white boys age 3 years are assembled in Table XVIII. Those in the right panel represent boys from homes above average in socioeconomic status, while those in the left panel characterize samples unselected or near the middle socioeconomically. The left panel registers a rise in mean body weight of 0.9 kg over a period approximathg 18 years, nutritional guidance having been accessible to a greater percentage of parents of the boys studied 1931-1942 than 1918-1919. The overall rise in the right panel is 1.1 kg for a period of roughly 5 5 years. Tables XVI through XVIII pertain to weight of the nude body. In compiling the tables that follow, nude body weight for some samples had to be approximated. The reason for this, and the procedures employed, are discussed in the next four paragraphs.

92

Change in Stature and Body Weight Prior to 1900 it was customary at the elementary and secondary school ages to obtain body weight with the subject wearing indoor clothing. Use of these early materials to derive estimates of secular change in body weight necessitates adjustments for weight of the clothing worn. The adjustment of a mean for body weight with clothes to a mean for body weight without clothes should not be regarded as a biologically precise correction (Clark, 1930; Gebhart, 1924; Krogman, 1950; Sumner and Whitacre, 1931). Often studies are not explicit on matters such as season of year or exclusion of shoes. There is the further complication that average weight of indoor clothing declined appreciably between the later part of the nineTABLE XVIII BODY WEIGHT(KG) O F NORTHAMERICANWHITEBOYS AGE 3 YEARS: MEANSAT SPACED TIMESDURINGSECULAR PERIODS OF 18 YEARS (LEFT PANEL) AND 5 5 YEARS(RIGHT PANEL) American White boys Time

N

Mean

1918-1919

2541a

13.9

1931-1942

2836

14.8

__

Above average economically Time ca. 1895c

Q

1913-1916d 1922-1929’ 1931-1937’ 1938-19620

N

Mean

76

14.1 14.6 14.9 15.1 15.2

103 286 209

Woodbury, 1921.

* Rhoads et uf., 1945; Tuddenham and Snyder, 1954; Vickers and Stuart, 1943. Holt, 1897. Gum, 1916. 0 Iowa Child Welfare Research Station, 1929; Wallis, 1931. I Bayley and Davis, 1935; Peatman and Higgons. 1938; Simmons and Todd, 1938. Knott and Foman, 1963; Meredith, 1948. c

teenth century and 1960. Bowditch (1877) supplemented his 1875-1876 study of Boston school boys with the following means from weighing indoor clothing for samples of 6 to 8 boys: 1.5 kg at age 7 years, 2.0 kg at age 9 years, 2.8 kg at age 11 years, 3.3 kg at age 1 3 years, and 3.7 kg at age 15 years. These values are about triple those for weight of indoor clothing today (Meredith and Knott, 1962). To avoid over-correcting the means for body weight with clothing reported prior to 1900, thereby exaggerating secular increase in body weight, the following deductions have been made: 0.7 kg at age 6 years, 0.8 kg at ages 7 years and 8 years, 0.9 kg at ages 9 years and 10 years, 1.0 kg at age 11 years, 1.3 kg at age 14 years, and 1.4 kg at ages 15 years to 17 years. Some of the studies of body weight made after 1900 are based on measures for weight with clothing. The corrections in these instances are indicated

93

Howard V. Meredith in footnotes to the tables for mean body weight at ages 6 years, 10 years, and 15 years. Tables XIX and XX depict mean body weight at age 6 years. I n columns 3 and 6 of Tables XIX are means at successive times for the general run of North American white and Negro boys. The corresponding columns of Table XX carry means for white boys from varying segments of the socioTABLE XIX BODY WEIGHT(KG) OP NORTHAMERICAN BOYSAGE 6 YEARS:MEANS AT SPACED TIMESDURING SECULAR PERIODS OP 70 YEARS (LEFTPANEL) AND 60 YEARS(RIGHTPANEL)^ American White boys Time

N

American Negro boys

Mean

1875-1880b 1892-1900° 1921-1927d 1932-1939" 1947-1949'

1498 958 3140 11,005 1133

N

Time ~

18.8 19.2 20.0 20.8 21.2

~~

~

1896-18980 1921-1925'" 1936-1938' 1957-1958i

Mean _

~~

73 120 173 25

_

_

~

19.0 19.8 20.5 22.7

Means from studies of body weight in indoor dothing have been reduced 0.7 kg prior to 1910, 0.6 kg during 1910-29. 0.5 kg during 1930-49. and 0.4 kg from 1950 on. Bowditch, 1877; Peckhnm. 1881. = MacDonald, 1899; Porter, 1894; Smedley, 1902. d Collins and Clark, 1929; Keybtt, 1942; Mustard and Waring, 1926; Packer and Moehlman, 1921; Schwartz et al., 1928. *Brown, 1936; Keyfitz, 1942; Lloyd-Jones. 1941; O'Brien CI al., 1941. f Hundley rt al.. 1955. 0 MacDonald. 1899. A Mustard and Waring. 1926; Packer and Moehlman, 1921. 1 Lloyd-Jones. 1941. f Krogman, 1960. 0

*

TABLE XX BODY WEIGHT (KG) OF NORTHAMERICAN WHITE BOYS AT 6 YEARS:MEANS AT SPACED TIMES DURING SECULAR PERIODS APPROXIMATING 75 YEARS Below average economically Time

N

Mean

Time

N

Mean

1875-1876" 1918-1927b 1937-1939' 1947-194gd

329

18.9 19.0 20.2 20.4

1875-1876" 1921-1927* 1937-1939' 1947-1962f

126 619 1572

19.0 20.4 21.0 21.7

4

599 1535 446

Bowditch, 1879.

* Hundley at al., 1955; Rude, 1922. O'Brien ct aX, 1941. Hundley eta).. 19s). e Brown, 1926; Hundley tt a)., 1955. Hundley d ul.. 1955; Knott and Foman, 1963.

d

94

Above average economically

739

~

~

Change in Statwe and Body Weight economic continuum. Both tables are compiled from samples so similar to those utilized for Tables IV and V that the reader may return to the descriptions in Section 11, C. Increase in body weight with time is shown by each column of means. The terminal means in Table XIX provide suitable material on which to base selected quantitative inferences. For North American white boys 6 years of age, mean body weight was less in 1880 than in 1950 by an amount probably between 2.1 kg (4.6 Ib) and 2.7 kg (5.9 Ib). For North American Negro boys 6 years of age, there is high probability that mean body weight was at least 1.9 kg (4.2 lb) lighter in 1900 than in 1960. Generalization. North American Negro and white boys of preschool and kindergarten ages are found to be heavier at the middle of the twentieth century than at its inception. The absolute and relative magnitudes of this secular change in body weight are greater at age 6 years than at age 3 years. During the 70-year period between 1880 and 1950, it is estimated that the relative rise in mean body weight for North American white boys age 6 years lies between 11% and 15%.

C. DISTRIBUTION OF BODYWEIGHT AT SELECTED AGESFROM MIDDLECHILDHOOD INTO ADOLESCENCE This section encompasses the period of ontogeny between ages 6 years and 15 years, giving consideration to secular change in the central tendency and variability of age-specific distributions for body weight. The bulk of its quantitative content is colligated in three variations of table construction, two for central tendency and one for variability. Table XXI pertains to secular change in the distribution of body weight. Intercomparison of the percentiles in the successive paired rows reveals: (1) at each age from 7 years to 15 years, the tenth percentile at or after 1950 exceeds the thirtieth percentile prior to 1900; (2) at ages between 10 years and 15 years, the thirtieth percentile at or after 1950 exceeds the seventieth percentile prior to 1900; (3) at ages between 12 years and 1 5 years the fiftieth percentile near 1960 exceeds the ninetieth percentile before 1900; (4) at ages between 13 years and 15 years, the tenth percentile near 1960 exceeds the fiftieth percentile before 1900; and (5) at ages 14 years and 14.5 years, the thirtieth percentile near 1960 exceeds the ninetieth percentile before 1900. These findings, supplemented by inspection of the eight rows of E values, lead to two conclusions: (1) age-specific distributions of body weight for North American boys shifted to the right in the period from 1890 to 1960, and (2) variability of body weight increased at childhood and early adolescent ages due to greater secular displacement of the upper part of the distributions than the lower part.

95

Howard V . Meredith Juxtaposed in the next three tables are secularly spaced means for body weight on North American boys subgrouped by region of residence, socioeconomic level, and racial lineage. These tables and those in Section 11, D, constitute similar sets for stature and weight. TABLE XXI BODY WEIGHT(KG) OP NORTH AMERICAN WHITEBOYS AGES7 YEARSTO 15 YEARS: FROM SAMPLES SEPARATED IN TIMEBY PAIREDRows OF PERCENTILES INTERVALS OF 58 YEARSTO 86 YEARS Time

N

1892" 1950b

1814 260

1892a 1950*

2064

1875-1876' 1961-1962d

1293 90

1892a 1961-1962d

1644

1892G 1961-1962d

1242 93

1891' 1961-1962d

192 97

1887-1895' 1961-1962d

150 72

1892" 1961-1962d

498 79

208

110

PIO E

P ~ oE

P ~ oE

Age 7 years: Missouri, Oregon 19.8 21 .o 20.3 2 . 1 22.1 2 . 3 23.5 2 . 5 Age 10 years: Missouri, Oregon 23.3 25.7 27.5 27.3 4 . 0 29.7 4 . 0 32.1 4 . 6 Age 11.5 years: Massachusetts, Iowa 28.8 30.6 25.4 29.4 4 . 0 33.2 4 . 4 3 6 . 2 5 . 6 Age 12 years: Missouri, Iowa 27.5 30.2 32.3 32.1 4 . 6 36.6 6 . 4 3 9 . 3 7 . 0 Age 13 years: Missouri, Iowa 32.4 36.0 29.3 36.4 7 . 1 41.5 9.1 4 5 . 4 9 . 4 Age 14 years: Massachusetts, Iowa 32.3 36.4 39.6 4 4 . 1 1 1 . 8 4 9 . 3 1 2 . 9 5 5 . 3 15.7 Age 14.5 years: Maryland, Iowa 31.8 35 . I 38.7 4 4 . 9 1 3 . 1 52.4 17.3 5 7 . 9 19.2 Age I S years: Missouri, Iowa 39.6 44.1 35.6 48.2 1 2 . 6 5 4 . 1 14.5 59.1 15.0

18.2

P70

E

P ~ oE

22.2 25.0 2 . 8

24.6 27.4 2 . 8

29.3 34.5 5 . 2

32.3 39.3 7 . 0

32.6 39.8 7 . 2

36.0 46.9 10.9

34.5 43.1 8 . 6

38.1 52.3 1 4 . 2

37.7 50.6 1 2 . 9

42.2 61.0 18.8

43.9 60.2 1 6 . 3

48.5 6 5 . 4 16.9

42.6 63.5 20.9

51.7 7 6 . 4 24.7

48.8 64.0 15.2

55.7 74.3 18.6

Porter, 1894. *Meredith and Meredith, 1953. e Bowditch, 1891. d Knotr and Meredith, 1962. Moon, 1895. Boas and Wissler, 1905. 0

Presented in Table XXII are means on North American white public school boys at ages 7 years, 1 1 years, and 14 years. The paired-row comparisons are arranged in geographic sequence, moving from east to west. As in Table VII for stature, each row of E values registers increase in magnitude with age. To illustrate: the last pair of studies, spanning a period of 46 years, yields increases of 2.2 kg at age 7 years, 4.9 kg at age 11 years, and 7.4 kg at age 14 years.

96

Change in Stature and Body Weight TABLE XXII BODY WEIGHT(KG) OF NORTH AMERICAN WHITESCHOOLBOYS: PAIRED Rows OF MEANSFROM SAMPLESSEPARATED IN TIME BY INTERVALS VARYING BETWEEN 41 YEARS AND 53 YEARSa 7 years Time

1875-1876* 1923-1931' 1891" 1937-1939" 1896-1898' 1937-1939e 1892d 1939' 1899-1900* 1948-1958'

ca. 1880i 1923-1924' 1886-1890' 1937-1939" 1916-1 9 19" 1961-1962" 1892O 1937-1939" 1892p 1937-1939'

N

Mean

11 years

E

N

Mean

I 4 years

E

5.2 years: Massachusetts 1338 2 0 . 6 1328 29.7 473 21.6 1 . 0 709 32.5 2 . 8 47 years: Massachusetts, Pennsylvania 155 20.8 215 3 0 . 1 271 22.6 1 . 8 340 3 3 . 6 3 . 5 41 years: District of Columbia and vicinity 533 20.8 862 2 9 . 1 466 2 3 . 1 2 . 3 593 33.7 4 . 6 47 years: Ontario 930 20.4 878 29.3 4080 22.7 2 . 3 4470 3 3 . 3 4 . 0 53 years: Illinois, Pennsylvania 228 2 0 . 8 241 30.2 90 23.5 2 . 7 175 38.9 8 . 7 43 years: Visconsin, North Central States 620 20.5 550 29.9 492 22.1 1 . 6 515 32.7 2 . 8 50 years: fiissozbri, Iowa 465 31.3 527 3 3 . 8 2 . 5 44 years: Missouri, Iowa 332 32.2 78 38.2 6 . 0 46 years: Missouri, Kansas 1814 20.9 1743 30.0 270 22.5 1 . 6 356 3 3 . 3 3 . 3 46 years: C~zlifornia 169 21.7 220 31.6 235 2 3 . 9 2 . 2 278 36.5 4 . 9

N

Mean

E

1034 3 9 . 4 711 45.6

6.2

208 40.7 445 46.4

5.7

784 38.8 1005 47.1

8.3

629 38.9 2905 4 4 . 7

5.8

240 41.4 73 5 3 . 1 1 1 . 7 284 39.7 468 44.7

5.0

404 41.0 198 4 5 . 9

4.9

265 4 3 . 6 97 55.4 11.8 946 39.1 455 45.9

6.8

172 4 2 . 7 50.1

7.4

280

The statistics in each row are independent of those in every other row. i Peckham, 1881. 1877. k Palmer and Collins, 1935. 0 Shuttleworth, 1939. 1 Greenwood, 1891. d Boas and Wissler, 1905. m Pyle, 1920. c O'Brien et al., 1941. n Knotr and Meredith, 1962. I MacDonald, 1899. 0 Porter. 1894. n Keyfitz, 1942. Smedley, 1902. p Boas, 1895. i Krogman, 1960. 0

* Bowditch,

97

Howard V . Meredith Table XXIII has two functions. Its upper part carries secular comparisons of mean body weight from samples of white public school boys drawn 65 years to 80 years apart. Again, geographic order begins at the east coast and proceeds westward. From the Wisconsin-Iowa investigations separated in time by 80 years, it is practically certain that the population means for body weight at age 14 years differed more than 13.2 kg, or 29 lb. The lower part of Table XXIII displays changes in mean body weight for North American white boys representing both spaced segments of the socioeconomic continuum and adjacent portions of the socioeconomic continuum. Two additional comparisons for social classes of North American white boys

TABLE XXIII

BODY WEIGHT(KG) OF NORTHAMERICANWHITE SCHOOLBOYS: PAIREDRows OF MEANSFROM SAMPLES SEPARATED IN TIMEBY INTERVALS VARYING BETWEEN 41 YEARS AND 80 YEARS 10 years

Time 1875-1879 1948-1958b

ca. 1880c 1961-1962d 1892' 1957-1958' 1875-18764 19509 1875-1876" 19500 1896-1898h 1937-1939' 1896-1898h 1937-1939'

N

b

9s

E

N

Mean

15 years

E

N

Mean

E

77 years: American White: Masacbufetts, Pennglvania 1400 27.2 1034 39.4 187 36.2 9.0 73 53.1 13.7 80 years: American White: Wisconsin, Iowa 284 39.7 163 45.1 97 55.4 15.7 79 61.1 16.0 65 years: American White:California, Oregon 223 28.8 137 49.5 86 33.9 5.1 51 59.2 9.7 74 years: Fathers in unskilled occupations 280 27.4 40 32.3 4.9 74 years: Fathers in profimonal occupations 27 29.0 43 34.3 5.3 41 years: Families below average economically 350 26.8 231 38.1 146 42.1 3177 29.9 3 . 1 2340 44.4 6.3 1862 50.7 8 . 6 41 years: Families above average economically 358 39.3 259 45.6 353 27.2 3116 31.3 4. 1 3047 46.9 7.6 2736 53.3 7 . 7

Bowditch, 1877. Krogman. 1960. * Peckham. 1881. Knott and Meredith. 1962. Boas, 1895, Degutis, 1960;Harrison, 1959. 0 Meredith, 1951. MacDonnld, 1899. i O'Brien uf ul., 1941.

4

Mean

14 years

Cbange in Statwe and Body Weight are relevant. At ages between 10 years and 15 years, boys attending private schools in Pennsylvania 1889-1893 (Hall, 1896) averaged 5.2 kg lighter than boys attending private schools in several states 1920-1930 (Gray and Ayres, 1931). In relation to boys at private schools in Massachusetts 1875-1876 (Bowditch, 1877), boys at a private school in Iowa 1930-1937 (Meredith, 1941a) were heavier at ages from 11 years to 1 5 years by an average of 5.2 kg. Secular weight changes for several North American racial groups are exhibited in Table XXIV. With one exception the statistics are readily found TABLE XXIV BODY WEIGHT(KG) OF NORTHAMERICAN SCHOOLBOYS: PAIREDRows OF MEANSFROM SAMPLES SEPARATED IN TIMEBY INTERVALS VARYING BETWEEN 22 YEARSAND 61 YEARS 10 years

Time

N

Mean

14&years

E

N

Mean

15 years

E

N

Mean

E

61 years: American Negro: District of Columbia, Massachusetts, Pennsylvania 1896-1898a 335 28.7 1957-1959b 77 32.1 3.4 48 years: American Negro: Missouri, Kansas 1 886189Oc 50 42.0 1936-1937d 120 44.5 2 . 5 25 years: American Japanese: California 1930-1932' 98 28.7 48 46.0 1956-1957' 33 30.3 1 . 6 34 50.1 4.1 32 years: American Italian: Massachusetts 19261927' I l l 28.1 1958-1959A 54 34.8 6.7 22 years: American Italian: New York, Massachusetts 1908-1910' 113 36.6 70 39.4 1930-1932r' 83 44.3 7.7 81 50.2 10.8 30 years: American Bohemian, Finn: New York, Minnesota 1908-1910' 80 39.7 41 41.9 1938-1939" 93 46.3 6 . 6 100 52.1 10.2 21 years: American Dutch: Michigan 1931-1933' 149 5 0 . 5 1957-1958' 96 61.2 10.7 MacDonald, law. Krogman, 1960;Piscopo, 1962. c Greenwood, 1891. d McLendon, 1937. Preston. 1936;Suski, 1933. Greulich, 1957. a Dearborn et at., 1938. h Piscopo, 1962. (Boas, 1911. i Matheny and Meredith, 1947. Steggerda and Densen. 1936. I Spurgeon el al.. 1959. ._. b

99

Howard V . Meredith in the sources indicated. For comparison with the 1958-1959 mean on boys of Italian descent drawn from the middle and lower classes, a 1926-1927 mean was obtained from Dearborn et ul. (1938) by using records on boys of Italian ancestry in occupational groups 111, IV, and V. To the weight increases shown for American Negro, Japanese, Italian, Bohemian-Finn, and Dutch boys, it is possible to append a short-term finding on Amerindian boys. Writing in respect to the segment of ontogeny between ages 6 years and 18 years, Steggerda and Shaffer (1942) report that mean body weight of Navajo boys measured in New Mexico and Arizona averaged 2.1 kg less in 1932-1934 than in 1941. Central tendency tables of the synthesizing type provide substance for the third part of this subsection. Table XXV presents composite means at TABLE XXV NORTHAMERICAN BOYSAGE 10 YEARS:MEANS TIMES DURING SECULAR PERIODS OF 76 YEARS

BODY WEIGHT(KG)

OF

AT SPACED (LEFT PANEL) AND 66

YEARS(RIGHT

PANEL)a

American Negro boys

American White boys

Time

N

Mean

Time

N

Mean

1875-1880b 1890-1900’ 1921-1931’ 1932-1340‘ 1948-1958’

1972 4027 8186 19,802 1001

27.4 27.6 28.9 30.7 33.4

1886-18989 1921-192Sh 1929-1938i 1957-1959’

374 276 360 77

28.9 29.6 30.2 32.1

Means from studies of body weight in indoor clothing have been reduced 0.9 kg prior to 1910, 0.8 kg during 1910-29, 0.7 kg during 1930-49, and 0.6 kg from 1950 on. 6 Bowditch, 1877; Peckham, 1881. c Boas, 1895; Boas and Wissler, 1905; Greenwood. 1891; MacDonald, 1899; Porter, 1894; Smedley, 1902. d Brown, 1926; Collins and Ctark; 1929; Keyfitz, 1942; Mustard and Waring, 1926; Packer and Moehlman, 1921; Palmer, 1933; Schwartz eta)., 1928; Whitaae, 1939. ‘Binning, 1958; Brown, 1936: Keyfitz. 1942; Lloyd-Jones; 1941; O’Brien el a!., 1941; Tuddenham and Snyder, 1954; Wolff, 1941. I Binning, 1958; Degutis, 1960; Eppright and Sidwell, 1954; Krogman, 1960; Meredith and Meredith. 1953. 0 Greenwood, 1891; MacDonald. 1899. h Herskovits, 1924; Mustard and Waring, 1926; Packer and Moehlman, 1921. i Lloyd-Jones, 1941; Whitacre, 1939. i Krogman, 1960; Piscopo, 1962.

Z .

successive times for North American white and Negro boys age 10 years. Both series of means increase with time. Statistically based inferences are: (1) mean body weight for North American white boys age 10 years was greater in 1950 than in 1880 by at least 5.6 kg, or 12.4 pounds, and ( 2 ) mean body weight for North American Negro boys age 10 years was less in 1890 than in 1955 by more than 1.8 kg, or 4 lb.

100

Change in Stattlre and Body Weight In Table XXVI are listed composite means at successive times for youths age 15 years. It may be inferred ( 1 ) mean body weight of North American Negro youths age 15 years increased from 1890 to 1930 by an amount between 5.3 kg and 8.5 kg, or 11.7-18.7 lb, and ( 2 ) mean body weight of North American white youths age 15 years increased from 1870 to 1955 by an amount between 15.0 kg and 17.8 kg, or 33.1-39.2 Ib. Generalizdtion. Over the last several decades, the distribution for body

weight of North American white boys has undergone upward displacement at TABLE XXVI BODY WEIGHT (KG) OF NORTHAMERICAN YOUTHS AGE 15 MEANSAT SPACEDTIMESDURING SECULAR PERIODSOF 86 (LEFT PANEL) AND

American White youths

Time

N

Mean

1852-1886* 1890-1 900" 1911-1919d 1922-1930e 1932-1940' 1948-19620

2358 1705 814 1649 14,083 268

43.4 45.8 46.8 47.5 52.5 59.8

YEARS: YEARS

40 YEARS (RIGHT PANELjY

American Negro youths

Time

N

Mean

1886-1898*

266

44.7

1921-1926i 1927-1938'

222 519

49.2 51.6

Means from studies of body weight in indoor clothing have been reduced 1.4 k s prior to 1910. 1.2 kg during 1910-29, 1.0 kg during 1930-49, and 0.8 kg from 1950 on. * Bowditch. 1877; Cordeiro. 1887; Gihon, 1880; Peckham, 1881. e Boas. 1895; Boas and Wissler, 1905; Greenwood, 1891; MacDonald, 1899; Porter, 1894; Smedley, 1902. Pyle, 1920; Woolley, 1926. a Bissett and Laslett. 1932; Collins and Clark, 1929; Keyfitn, 1942; Mustard and Waring, 1926; Schwartz ef al., 1928. I Brown, 1936; Keyfitz, 1942; Lloyd-Jones. 1941; O'Brien ef al., 1941; Wolff, 1941. u Eppright and Sidwell, 1954; Harrison, 1959; Knott and Meredith. 1962; Newcomer and Meredith, 1951. * Greenwood, 1891; MacDonald, 1899. 1 Herskovits. 1924; Mustard and Waring, 1926; Packer and Moehlman, 1921. i Beckham, 1938; Lloyd-Jones, 1911; McLendon. 1937; Whitacre, 1939.

all ages between 7 years and 15 years. Magnitude of displacement has varied systematically in two respects, having (1) increased with age from childhood into early adolescence, and ( 2 ) increased less toward the lighter end of each distribution than toward the heavier end. Secular change in mean body weight, with amount of change rising throughout childhood, has occurred for North American boys of different ancestries, economic classes, and geographic localities. At age 15 years, mean body weight for North American young men largely of northwest European ancestry has increased during the last 8 5 years more than 15.0 kg, or 35 %.

I01

Howard V . Meredith

D. MEANBODYWEIGHT IN LATEADOLESCENCE AND EARLYADULTHOOD Exhibited in Table XXVII are composite means at spaced times for North American youths age 17 years. Unfortunately, the means in the right panel for American Negro youths studied 1863-1864 and 1923-1931 are based TABLE XXVII BODY WEIGHT(KG) OF NORTH AMERICAN YOUTHSAGE 17 YEARS: SECULAR PERIODS OF 82 YEARS MEANSAT SPACED TIMESDUR~NG (LEFTPANEL)AND 94 YEARS(RIGHT PANEL) American White youths

American Negro youths

Time

N

Mean

Time

N

Mean

1852-1886' 1890-1900* 1911-1930' 193619446 1945-1958"

3350 453 1324 10,081 I168

53.6 55.3 59.0 62. O 62.9

1863-1864'

48

56.1

1923-19319 1936-1938h 1957-195EIi

45 133 208

56.3 61.8 62.9j

Bowditch, 1877; Cordeiro, 1887; Gihon, 1880; Gould, 1869; Peckham, 1881. *Boas and Wissler, 1905; Greenwood, 1891; MacDonald, 1899; Porter, 1894; Smedley, 1902. Bissert and Laslett, 1932; Pyle, 1920; Schwartz ez al.. 1928; WoolIey, 1926. d Lloyd-Jones, 1941; O'Brien CI al., 1941; Randall, 1949; Wolff, 1941. r Karpinos, 1961; Reed and Stuart, 1959; Tuddenham and Snyder. 1954. Baaer. 1875. I Herskovits; 1924; Whitacre, 1939. Lloyd-Jones. 1941. i Karpinos, 1961. 1 Means representing age 17.5 years have been reduced 1.3 kg as an approximate adiustmenf to age 17 years.

*

on small samples. The substantial materials in the left panel provide a basis for asserting that mean body weight of North American white youths age 17 years was higher in 1950 than in 1870 by an amount neither smaller than 8.6 kg nor greater than 10.0 kg. Magnitude of secular change in mean body weight for North American white youths is less at age 17 years than at age 15 years. Point estimates of the population differences in mean weight (16.4 kg for 85 years from Table XXVI and 9.3 kg for 82 years from Table XXVII) transpose to 4.2 pounds per decade at age 15 years and 2.5 Ib per decade at age 17 years. Means for body weight at age 20 years are assembled in Table XXVIII on samples of white men accepted for service in the United States defense

102

Change in Stature and Body Weight forces (column 3) and white men attending North American colleges and universities (column 6 ) . Both columns register increase in mean body weight from the last quarter of the nineteenth century to the middle of the twentieth century. Statistical evaluation of the means in column 3 indicates that the amount of increase during the period from 1865 to 1960 falls probably between 7.8 kg (17.2 Ib) and 8.8 kg (19.4 lb). For North American Negro men 20 years of age, Gould (1869) obtained a mean of 63.1 kg on 163 United States soldiers and sailors weighed 18611865, and Karpinos (1961) a mean of 68.6 on 1421 United States Selective TABLE XXVIII BODYWEIGHT (KG) OF NORTHAMERICAN MEN AGE20 YEARS: MEANS AT SPACED TIMESDURING SECULAR PERIODS OF 91 YEARS (LEFTPANEL)AND 73 YEARS(RIGHTPANEL) American White men

American White college men

Time

N

Mean

Time

N

Mean

1852-1880°

1949

62.3

1942-1947b 1957-1958'

2258 9833

68.7 70.6

1861-1891d 1908-191 7' 1928-193Of 1947-1952g

270 485 3613 11,899

62.3 63.2 65.3 70.4

Gibon, 1880; Gould. 1869. *Randall, 1949. c Karpinos, 1961. d Hitchcock, 1892. E M , 1954. Diehl. 1933. Hbd, 1954; Hathaway and Foard, 1960; Sturzebccker, 1930.

4

Service inductees weighed 1957-1 958. The secular difference is equivalent to an increase in mean weight of 0.6 kg, or 1.3 Ib, per decade. A similar increase, 0.7 kg per decade, is found from studies by Sternberg (1893, 1898) and Karpinos (1961) on North American Negro men between 20 and 25 years of age. The Sternberg data from 1479 United States army recruits examined 1892-1897 yield a mean of 66.1 kg, and the Karpinos data a mean of 70.7 kg for 10,389 United States Selective Service inductees examined 1957-1958.

Body weight means for North American white men 20-25 years of age are 65.0 kg on 20,636 army recruits 1892-1897 (Sternberg, 1892, 1898) and 72.1 kg on 89,012 military service inductees 1957-1958 (Karpinos, 1961). This secular difference transposes to 1.1 kg, or 2.4 Ib, per decade. Recently derived population estimates of mean body weight for Canadian and United States white men in the fifth quinquennium of postnatal life

103

Howard V . Meredith are available from a Canadian survey conducted 1953 (Pett and Ogilvie, 1957), an analysis of 1957-1958 data on United States Selective Service registrants (Karpinos, 1961), and a North American synthesis for circa 1955 (Stoudt et al., 1960). The highest mean of the three, that from data amassed 19571358 on 189,553 men, is 71.7 kg. Generalization. Research on North American human males shows that between age 1 5 years and early adulthood the magnitude of secular increase in body weight declines. Mean body weight in 1960 is estimated to exceed mean body weight in 1875 by (1) not less than 15.0 kg, or 3576, at age 1 5 years, and ( 2 ) not more than 8.8 kg, or 14 %, at age 2 0 years.

E. GRAPHOF MEANBODYW E I G H T CIRCA 1880 AND 1960 Figure 2 portrays schematically the principal findings of Section I11 in respect to secular change for North American white boys in mean body weight. As with the companion illustration for stature, it is left for the reader to study this graphic summary and cross-check its contents.

IV. Postscript This chapter was planned to concentrate on selected facets of the problem of phylogenetic variation in size of the human body. The blueprint called for a synthesis of presently accessible knowledge on the direction and magnitude of secular change during the last 80 years in the stature and body weight of North American male infants, children, youths, and young adults. In Sections I1 and I11 this projected synthesis is actualized. Before terminating the chapter, it is relevant to make brief reference to the diverse commentaries on determinants and implications of secular changes in somatic traits. Present knowledge of secular changes in somatic traits has been attained piecemeal and at a slow pace. A paucity of fact was sufficient to begin arousing conjecture regarding antecedents, concomitants, and consequences. An example of the fragmentary perspective of early research and interpretation is a study in which college women were found to show increase in stature with time, and the explanation was sought in their increasing participation in college sports with time (Newcomer, 1921). Succinctly, the gradual accumulation of fact has stimulated a varied and extensive array of suppositional by-products relating to causal variables and biological advantages or disadvantages of the generational changes discovered. The following have been viewed as plausible determinants of secular varia-

104

Change in Statare and Body Weight c

KG 65

-

60

-

55

-

50

-

45 40 -

35 30

-

25

-

20

-

15

-

10 -

5 -

O - L

B

2

4

6

8

10

12

14

16

18

20

AGE I N YEARS

Fig. 2. Schematic curves of mean body weight f o r 1880 and 1960. Inset shows differences between ihe curves at selected ages.

Howard V . Meredith tion in human body size: decline in the frequency of illnesses that retard growth (Boas, 1911; Hunt, 1958), changes in the North American population due to immigration (Davenport, 1920), effects of urbanization (Godin, 1920; Sargent, 1922), increase in athletic participation (Newcomer, 1921; Streit, 1951), reduction in child labor (Hrdlicka, 1922), improvement in housing and community hygiene (Hrdlicka, 1922; Blesh, 1956), changes to less restricting and lighter clothing (Mosher, 1923), increase in the nutritional content of North American diets (Gray, 1927; Jeans et al., 1946), effects of assortive and selective mating (Bowles, 1932; Stewart, 1947), improvement in medical care and personal health practices (Lloyd-Jones, 1940; Hooton, 1946), changes in world temperature and humidity (Mills, 1942), reversal of a biological adaptation to hard labor and crowded conditions (Sheldon, 1949), manifestation of an evolutionary tendency for organisms of a phylum to increase in size (Boyd, 1950), cumulative expression of heterosis (Hulse, 1957), and decrease in family size (Tanner, 1962). Present status of the determinant question is as follows: “Nobody knows for certain why the secular trend has occurred” (Tanner, 1962), “the actual cause is not certain” (Cone, 1961). This perspective needs emphasis. Plausible conjecture regarding portions of the secular phenomena too frequently is mistaken for complete identification of the source(s) of the phenomena. Particularly common are statements such as: “Better nutrition undoubtedly accounts for the fact that Americans have been getting taller on the average from one generation to another” (Martin and Stendler, 1953), and “The increase , . . must be regarded as due to better nutrition and greater freedom from disease” (Cole, 1959). While there are grounds for inferring that part of the secular increase in stature may result from advances in nutrition and health care (Meredith, 1943), cognizance must be taken of other observations. In respect to health care, Cone (1961) notes that “the accelative trend antedated the era of scientific medicine {and} dissemination of information concerning proper health habits.” In respect to diet, Garn (1952) observes: “First, it is doubtful that the diet actually improved (except in caloric intake) until the rather recent stress on practical nutrition, the increased consumption of fish, vegetables, and milk, and the introduction of enriched and fortified staples. Second, if an increase in caloric consumption is alone responsible for the change in stature, one would expect the rich to show little change as compared with the previously less favored classes.” The implications of secular increases in body size have been viewed as advantageous and subject to human control (Mosher, 1923), advantageous but not subject to human control (Mills, 1942), advantageous for a few decades but disadvantageous with longer continuation (Hrdlicka, 1922) , disadvantageous (Hooton, 1946), and possibly unrelated to the vitality of either

106

Change in Stature and Body Weight individuals or the species (Nyessen, 1928; Holt, 1942). Thought-provoking comment on the consequences of secular change is more rare than are assertions that somatic increase is an index of “racial betterment” (Chenoweth, 1937), a result of nurturing “contitutionally inferior” organisms (Hooton, 1939) , or an indicator of “progress” (Breckenridge and Vincent, 1943). Pronouncements such as these are not in the best interest of either the future advancement of child somatology, or dissemination in respect to knowledge attained and lacking on secular variation. ACKNOWLEDGMENT Gratitude for assistance is expressed to Patty Jo Christner, Virginia B. Knott, and E. Matilda Meredith. REFERENCES Anderson, N. A., Brown, E. W., & Lyon, R. A. Causes of prematurity: 111. Influence of race and sex on duration of gestation and weight at birth. Amer. J . D i s . Childh., 1943, 65, 523-534. Bakwin, H. The Negro infant. Hum. Biol., 1932, 4, 1-33. Bakwin, H., & Bakwin, R. M. Body build in infants: V. Anthropometry in the newborn. Hum. Biol., 1934, 6, 612-626. Bakwin, H., Bakwin, R. M., & Milgram, L. Body build in infants: IV. The influence of retarded growth. Amer. J . Dis. Childh., 1934, 48, 1030-1040. Bakwin, H., & Patrick, T. W. The wcight of Negro infants. J . Pediat., 1944, 24, 405457.

Baldwin, B. T. Physical growth and school progress, U. S . Bur. Educ., 1914, Bull. No. 10 (Whole No. 581). Baldwin, B. T. The physical growth of children from birth to maturity. Univer. Iowa Stud. Child W e l f . , 1921, 1, No. 1. Baltimore City Health Department. 143rd Annu. Rep. 1957. Baxter, J. H . Statistics, medical and anthropological. Bur. Prou. General, 1875, 1. Bayley, N., & Davis, F. C. Growth changes in bodily size and proportions during the first three years. Biometrika, 1935, 27, 26-87. Bean, R. B. Stature in Old Virginians. Amer. J . Phys. Anthrop., 1931, 15, 354-419. Beckham, A. S . A study of weight and stature of Negro city children of adolescent age. Hum. Biol., 1938, 10, 124-135. Binning, G . Earlier physical and mental maturity among Saskatoon public school children. Canad. J. Publ. Hlth., 1958, 49, 9-17. Bissett, L., & Laslett, H. R. A study of height, weight, and age among high school boys. J . juv. ReJ., 1932, 16, 291-297. Blesh, T. E. Seventy-one year survey of age-height-weight on entering freshmen at Yale University. Phys. Educator, 1956, 13, 13. Boas, F. The growth of first-born children. Science, 1895, 1, 402-404. Boas, F. The growth of Toronto children. Rep. U.S.Comm. Educ., 1898, 2, 1541-1599. Boas, F. Changes in bodily form of descendents of immigrants. U.S.Reps. immig. Comm., Senate Documents, 1911, 64, No. 208. Boas, F. Studies in growth 111. Hum. Biol., 1935, 7 , 303-318.

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Howard V . Meredith Boas, F. Age changes and secular changes in anthropometric measurements. Amer. J. Phys. Anthrop., 1940, 26, 63-68. Boas, F., & Wissler, C. Statistics of growth. Rep. US. Comm. Educ., 1905, 25-132. Bowditch, H. P. Comparative rate of growth in the two sexes. Boston Med. C Surg. J., 1872, 10, 434-435. Bowditch, H. P. The growth of children. 8th Ann. Rep., Mass. State Ed. Hlth., 1877, 273-324. Bowditch, H. P. The growth of children: A supplementary investigation. loth Ann. Rep., Mass. State Bd. Hlth., 1879, 35-62. Bowditch, H. P. The growth of children studied by Galton's method of percentile grades. 22nd Ann. Rep., Mass. Sjate Bd. Hlth., 1891, 477-522. Bowles, G . T. N e w types of old Americans at Harvard and at Eastern women's colleges. Cambridge; Harvard Univer. Press, 1932. Boyd, W . C. Genetics and the races of man. Boston: Little, Brown, 1950. Breckenridge, M. E., & Vincent, E. L. Child development. Philadelphia: Saunders, 1943. Brown, A. P. Comparative size of rural and urban Utah school children as determined by the weight-height-age relationship. Utah agr. exp. Station, 1936. Bull. 266. Brown, M. A. An investigation of the health of school children. Chicago: Elizabeth McCormick Memorial Fund, 1926. Cates, H. A., & Goodwin, J. C. The twelve-day-old baby. Hum. Biol., 1936, 8, 433-450. Chenoweth, L. B. Increase in height and weight and decrease in age of college freshmen over a period of twenty years. J . Amer. Med. Ass., 1937, 108, 354-356. Clark, G. Differences in measurements made in the nude and clothed for children between seven and nine years of age. Child Develpm., 1930, I, 343-345. Cole, L. Psychology of adolescence. (5th ed.) New York: Rinehart, 1959. Collins, S. D., & Clark, T. Physical measurements of boys and girls of native white race stock (third generation native born) in the United States. Publ. Hlth. Reps., 1929, 44, 1059-1083. Cone, T. E. Jr. Secular acceleration of height and biologic maturation in children during the past century. J . Pediat., 1961, 59, 736-740. Cordeiro, F. J. B. A contribution to anthropometry. N e w YorR Med. J., 1887, 45, 484-487. Crum, F. S. Anthropometric statistics of children-ages six to forty-eight months. Publ. Amer. Stat. Ass., 1916, 15, 332-336. Crump, E. P., Horton, C. P., Masuoka, J., & Ryan, D. Growth and development: I. Relation of birth weight in Negro infants to sex, maternal age, parity, prenatal care, and socioeconomic status. 1.Pediat., 1957, 51, 678-697. Davenport, C. B. The mean stature of American males. Quart. publ. Amer. Stat. Ass., 1920, 17, 484-487. Dearborn, W. F., Rothney, J. W. M., & Shuttleworth, F. K. Data on the growth of public school children. Monogr., SOC.Rer. Child Develpm., 1938, 3, No. 1. Deegan, W. A fifty-nine year survey at Yale reveals freshman are becoming younger, heavier and taller. Res. quart., 1941, 12, 707-711. Degutis, E. W. Relationships between selected physical and motor factors and the pubescent development of 10, 13, and 16-year-old boys. Doctoral dissertation, Univer. of Oregon (microcard), 1960. Diehl, H. S . Height and weight of American college men. H i m . Biol., 1933, 5, 445479. Dodge, C. T. J. Weight of colored infants: Growth during the first eighteen months. Amer. J. Phys. Anthrop., 1927, 10, 337-345.

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Chaizge in Stature uiZd Body Weight Elbel, E. R. Body measurements of male students entering the university of Kansas. Kansas Stud. Educ., 1954, 4, No. 2. Eppright, E. S., & Sidwell, V. D. Physical measurements of Iowa school children. J. Nutrition, 1954, 54, 543-556. Freeman, R. G., Jr., & Platt, V. Skeletentwicklung und wachstum der sauglinge von der geburt bis zu einem monat. Anthropologischer Anz., 1932 9, 68-78. Florida State Board of Health. Florida vital statistics. Annu. Rep,, 1961, Suppl. No. 1. Garn, S. M. Physical growth and development. Amer. J. Phys. Anthrop., 1952, 10 n.s., 169-1 92. Gebhart, J. C. The growth and development of Italian children in New York City. N e w York Ass. for Improving Condition of Poor, 1924, Publ. No. 132. Gihon, A. L. Adolescent growth in naval academy candidates and pupils. Rep., Secretary of Navy, 1880, 183-205. Godin, P. Growth during school age. Boston: Gorham Press, 1920. Gould, B. A . Investigations in the military and anthropological statistics of American soldiers. US.Sanitary Comm. Rep., 1869. Gray, H. Increase in stature of American boys in the last fifty years. J, Amer. Med. Ass., 1927, 88, 908. Gray, H., & Ayres, J. G. Growth in priuate school children. Chicago: Univer. Chicago Press, 1931. Greenwood, J. M. Heights and weights of children. 20th Annu. Rep., Kansas City ( M o . ) Bd. Educ., 1891, 48-56. Greulich, W. W. A comparison of the physical growth and development of American-born and native Japanese children. Amer. J. Phys. Anthrop., 1957, 15 n.s., 489-515. Griffith, J. P. C., & Gittings, J. C. The weight of breast-fed infants during the first two weeks of life. Arch. Pediat., 1907, 24, 321-345. Hall, W. S. The changes in the proportions of the human body during the period of growth. J. Anthrop. lmt. Gt. Brit. 6 Ireland, 1896, 25, 21-46. Harrington, T. F. Health and education. Amer. Phys. Educ. Rev., 1910, 15, 373-388. Harrison, J. C. E. The relationships between selected physical and motor factors and skeletal maturity of 9, 12, and 15-year-old boys. Doctoral dissertation, Univer. of Oregon (microcard), 1959. Hastings, W. W. A manual f o r physical measurements. Springfield, Mass: Young Men’s Christian Ass. Training School, 1901. Hathaway, M. L., & Foard, E. D . Heights and weights of adults in the United States. US.Dept. A g r . Home Econ. Res. Rep., 1960, No. 10. Herskovits, M. J. Some observations on the growth of colored boys. Amer. J. Phys. Anthuop., 1924, 7, 439-446. Herskovits, M. J. The anthropometry of the American Negro. Columbia Univer. Contr. Anthrop., 1930, 11. Hitchcock, E. T h e results of anthropometry as derived jrom the measurements of the students in Amherst College. Amherst, Mass: Carpenter & Morehouse, 1892. Holt, L. E. T h e diseases of infancy and childhood. New York: Appleton, 1897. Holt, L. E. Dietary factors in physical growth. J. Pediat., 1942, 20, 260-264. Hooton, E. A. Twilight of man. New York: G. P. Putman’s, 1939. Hooton, E. A. U p f r o m the ape. (Revised ed.) New York: Macmillan, 1946. Hopkins, J. W. Height and weight of Ottawa elementary school children of two socioeconomic strata. H u m . B i d , 1947, 19, 68-82. Hrdlicka, A. Anthropology of the old Americans: 11. Stature. Amer. J. Phys. Anfhrop., 1922, 5, 209-235.

Howard V . Meredith Hulse, P. S. Exogamie et heterosis. Arch. Suiss Anthrop. gen., 1957, 22, 103-125. Hundley, J. M., Mickelsen, O., Mantel, N., Weaver, R. N., & Taber, R. C. Height and weight of first-grade children as a potential index of nutritional status. Amer. J. Publ. Hlth., 1955,45, 1454-1461. Hunt, E. E., Jr. Human growth and body form in recent generations. Amer. Anthrop., 1958, 60, 118-131. Iowa Child Welfare Research Station. Physical traits of young chidren. Amer. J . Dis. Childh., 1929, 38, 541-546. Iowa Child Welfare Research Station. Physical traits of Iowa infants. Amer. J . Dis. Childh., 1931, 42, 1137-1143. Irving, R. N., Jr. Comparison of maturity, structural, and muscular strength measures for five somatotype categories of boys 9 through 15 years of age. Doctoral dissertation, Univer. of Oregon (microcard), 1959. Jeans, P. C., Rand, W., & Blake, F. G. Essentials of pediatrics. Philadelphia: Lippincott, 1946. Karlan, S. C. Increase in height and weight among the underprivileged. N e w York State J. Med., 1941,41, 2425-2426. Karpinos, B. D. Height and weight of Selective Service registrants processed for military service during World War 11. Hum. Biol., 1958,30, 292-321. Karpinos, B. D. Current height and weight of youths of military age. Hum. Biol., 1961, 33, 335-354. Kasius, R. V., Randall, A,, Tompkins, W. T., & Wiehl, D. G. Maternal and newborn nutrition studies at Philadelphia Lying-in Hospital: V. Size and growth of babies during the first year of life. Milbank Memorial Fund quart., 1957, 35, 323-372. Kelly, H. J. & Reynolds, L. Appearance and growth of ossification centers and increases in the body dimensions of white and Negro infants. Amer. J . Roent. & Rad. Ther., 1947, 57, 477-516. Kessler, A., & Scott, R. B. Growth and development of Negro infants. 11. Relation of birth weight, body length and epiphyseal maturation to economic status. Amer. J . Dis. Childh., 1950,80, 370-378. Keyfitz, N. A height and weight survey of Toronto elementary school cbijdren, 1939. Ottawa: Dep. of Trade and Commerce, Dominion Bur. Stat., 1942. Knott, V. B., & Foman, S. J. Stature and weight of healthy infants examined 1954-62 at a private pediatrics clinic. Unpublished study, Univer. of Iowa, 1963. Knott, V. B., & Meredith, H. V. Body size of Iowa City school-boys measured in 1962. Unpublished study, Univer. of Iowa, 1962. Krogman, W. M. A handbook of the measurement and interpretation of height and weight in the growing child. Monogr., SOC. Re$. Child Develpm., 1950, 8, No. 3. Krogman, W. M. Height, weight and bodily growth of American white and American Negro boys at Philadelphia, age 6-14 years. Philadelphia: Center for Research in Child Growth, (mimeographed), 1960. Lloyd-Jones, 0. California tall children. Amer. J. Dis. Childh., 1940, 60, 11-21. Lloyd-Jones, 0.Race and stature: A study of Los Angeles school children. ReJ. quart., 1941, 12, 83-97. MacDonald, A. Experimental study of children. Rep. US. Comm. Educ., 1899, 1, 9851204. MacKinnon, D. C., & Jackson, C. M. Changes in physical measurements of male students at the University of Minnesota during the last thirty years. Amer. J. Anat., 1931, 47, 405-423.

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Change in Stature and Body Weight McLendon, J. B., Jr. Standards of nutritional status for Negro high school boys. Unpublished masters thesis, Univer. of Iowa, 1937. Maresh, M. M. Linear growth of long bones of extremities from infancy through adolescence. Amer. J. Dis. Childh., 1955, 89, 725-742. Martin, W. E. & Stendler, C . B. Child development. New York: Harcourt, Brace, 1953. Matheny, W . D., & Meredith, H. V. Mean body size of Minnesota schoolboys of Finnish and Italian ancestry. Amer. J . Phys. Anthrop., 1947, 5 n.s., 343-355. Meredith, H. V. Stature and weight of private school children in two successive decades. Amer. J . Phys. Anthrop., 1941a, 28, 1-40. Meredith, H. V. The stature and weight of United States children. Amer. J . Dis. Childh., 1941b, 82, 909-932. Meredith, H. V. Physical growth from birth to two years: I. Stature. Univer. Iowa, Stud. Child V e l f . , 1943, 19. Meredith, H. V. Stature and weight on young boys of northwest European descent drawn 1938-45 from the professional and managerial classes. Unpublished study, Univer. Iowa, 1948. Meredith, H. V. Relation between socioeconomic status and body size in boys seven to ten years of age. Amer. J . Dis.Childh., 1951, 82, 702-709. Meredith, H. V. Methods of studying physical growth. In P. H. Mussen (Ed.), Handbook of research methods in child development. New York: Wiley, 1960. pp. 201251.

Meredith, H. V., & Brown, A. W. Stature at birth in relation to sex. Unpublished study, Univer. of Iowa, 1937. Meredith, H. V., & Brown, A. W. Growth in body weight during the first ten days of postnatal life. Hum. Biol., 1939, 11, 24-77. Meredith, H. V., & Knott, V. B. Descriptive and comparative study of body size on United States schoolgirls. Growth, 1962, 26, 283-295. Meredith, H. V., & Meredith, E. M. The stature of Toronto children half a century ago and today. Hum. Biol., 1942, 18, 126-131. Meredith, H. V., & Meredith, E. M. Hum. Biol., 1944. 16, 1 2 6 1 3 1 . Meredith, H. V., & Meredith, E. M. The body size and form of present-day white elementary school children residing in west-central Oregon. Child Develpm., 1953, 24, 83-102. Michelson, N. Investigations in the physical development of Negroes: I. Stature. Amer. J. Phys. Antbrop., 1943a, 1 n.s., 191-213. Michelson, N. Studies in the physical development of Negroes: 11. Weight. Amer. J Pbys. Anthrop., 1943b, 1 n.s., 289-300. Mills, C . A. Climate makes the man. New York: Harper, 1942. Montague, H., & Hollingsworth, L. S. The comparative variability of the sexes at birth. Amer. J. Sociol., 1914, 20, 335-370. Moon, S . B. The growth of boys. Rep. loth Annu. Meeting, Amer. Ass. Adv. Phys. Educ., 1895, 19-23 +tables. Mosher, C . D. Some of the causal factors in the increased height of college women. J . Amer. Med. Ass., 1923, 81, 535-538. Mustard, H. S . , & Waring, J. I. Heights and weights of colored school children. Amer. J . Publ. Hlth., 1926, 16, 1017-1022. Newcomer, M. Physical development of Vassar College students, 1884-1920. Quart. Publ. Amer. Stat. Ass., 1921, 17, 976-982. Newcomer, E. O., & Meredith, H. V. Eleven measures of body size on a 1950 sample of 15-year-old white schoolboys at Eugene, Oregon. Hum. Biol., 1951, 23, 24-40.

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Howard V . Meredith Norval, M., Kennedy, R. L. J., & Berkson, J. Biometric studies of the growth of children of Rochester, Minnesota. Hum. Biol., 1951, 23, 273-301. Nyessen, D. J. H. The Dutch physician as anthropologist. Amer. J . Phys. Anthrop., 1928, 12, 1-13. OBrien, R., Girshick, M. A,, & Hunt, E. P. Body measurements of American boys and girls for garment and pattern construction. U S . Dep. Agr., Bur. Home Econ., 1941, Misc. Publ. No. 366. Ohio Department of Health. Ann. Rep. Vital Stat., 1961. Packer, P. C., & Moehlman, A. B. A preliminary study of standards of growth in the Detroit public schools. Detroit Educ. Bull., 1921, NO. 5. Palmer, C. E. Growth and the economic depression: A study of the weight of elementary school children in 1921-27 and in 1933. U S . Publ. Hlth. Reps., 1933, 48, 12771292. Palmer, C. E., & Collins, S . D. Variations in physique and growth of children in different geographic regions of the United States. US. Pubi. Hlth. Reps., 1935, 50, 335-347. Pasamanick, B. A comparative study of the behavioral development of Negro infants. J. genet. Psychol., 1946, 69, 3-44. Paschal, F. C., & Sullivan, L. R. Racial differences in the mental and physical development of Mexican children. Comp. Psychol. Monogr., 1925, 3. Peatman, J. G., & Higgons, R. A. Growth norms from birth to the age of five years. Amer. J. Dis. Childh., 1938, 55, 1233-1247. Peckham, G . W. The growth of children. Gth Annu. Rep., Wisronsh State Bd. Hlth., 1881, 28-73. Peckham, G . M. Various observations on growth. 7th Annu. Rep. Wisconsin State Bd. Hlth., 1882, 185-188. Pett, L. B., & Ogilvie, G. F. The report of Canadian average weights, heights, and skinfolds. Cunud. Bull. Nutrition, 1957, 5, No. 1. (See also Hum. Biol., 1956, 28, 177-188). Piscopo, J. Skinfold and other anthropometrical measurements of pre-adolescent boys from three ethnic groups. Res. quart., 1962, 33, 255-264. Poole, M. W., Hamil, B. M., Cooky, T. B., & Macy, I. G. Addition of vegetable soup and strained vegetables to diet of artificially fed infants. Amer. J. Dis. Childh., 1938, 55, 1158-1175. Porter, W. T. The growth of St. Louis children. Trans., Acud. Sci. St. Louis, 1894, 6, 263-380. Preston, M. I. Growth of oriental children in San Francisco: A contrast. Amer., J. Dis. Childh., 1936, 51, 1324-1348. Pyle, W. H. A manual for the mental and physical examination of school children (revised). Uniu. Missouri Bull., Ext. Ser., 1920, 29, No. 12. Randall, F. E. Age changes in young adult army males. Ham. Biol., 1949, 21, 187-198. Reed, R. B., & Stuart, H. C. Patterns of growth in height and weight from birth to eighteen years of age. Pediut., 1959, 24, 904-921. Rhoads, T. F., Rapoport, M., Kennedy, R., & Stokes, J., Jr. Studies on the growth and development of male children receiving evaporated milk. I. The effect of various vitamine supplements on growth in length. J. Pediut., 1941, 19, 169-189. Rhoads, T. F., Rapoport, M., Kennedy, R., & Stokes, J., Jr. Studies on the growth and development of male children receiving evaporated milk. 11. Physical growth, dentition, and intelligence of White and Negro children. J. Pcdiut., 1945, 26, 415-454.

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Chdnge in Statwe and Body Weight Riggs, F . A comparative study of white and Negro pelves, with a consideration of the size of the child. Johns Hopkinr Hosp. Reps., 1904, 12, 421-454. Royster, L. T., & Hulvey, C. N. The relation of weight, height and age in Negro children. Amer. J . Dis. Childh., 1929, 38, 1222-1230. Rude, A. E. Physical status of preschool children, Gary, Ind. U.S. Dep, Labor, Childr. Bur., 1922, Publ. No. 111. Rueda-Williamson, R., & Rose, H. E. Growth and nutrition of infants: The influence of diet and other factors on growth. Pediat., 1962, 30, 639-653. Sargent, D. A. Taking account of stock. Amer. Phyr. Educ. Rev., 1922, 27, 47-50. Schwartz, L., Britten, R. H., & Thompson, L. R. Studies in physical development and posture. US.Publ. Hlth. Bull., 1928, No. 179. Scott, R. B., Cardozo, W. W., Smith, A. DeG., & DeLilly, M. R. Growth and development of Negro infants. 111. Growth during the first year of life as observed in private pediatric practice. J. Pediat., 1950a, 37, 885-893. Scott, R. B., Jenkins, M. E., & Crawford, R. P. Growth and development of Negro infants. 1. Analysis of birth weights of 11,818 newly born infants. Pediut., 1950b, 6, 425-431. Scott, R. B., Hiatt, H. H., Clark, B. G., Kessler, A. D., & Ferguson, A. D. Growth and development of Negro infants: IX. Studies on weight, height, pelvic breadth, head and chest circumferences. Pediat., 1962, 29, 65-81. Sheldon, W. H. Varieties of delinquenr youth. New York: Harper, 1949. Shuttleworth, F. K. The physical and mental growth of girls and boys age six to nineteen in relation to age at maximum growth. Monogr., SOC.Res. Child Develpm., 1939, 4 , No. 3. Simmons, K. The Brush Foundation Study of child growth and development. 11. Physical growth and development. Monogr. Sor. Ref. Child. Developrn., 1944, 9, No. 1. Simmons, K., & Todd, T. W. Growth of well children: Analysis of stature and weight. Groivth, 1938, 2, 93-134. Smedley, F. W. Child study in Chicago. Rep. US. Comm. Edur.. 1902, 1, 1095-1138. Spier, L. Growth of Japanese children born in America and in Japan. Univer. Wurh. Publ. Anthrop., 1929, 3, 1-29. Spurgeon, J. H., Young, N. D., & Meredith, H. V. Body size and form of Americanborn boys of Dutch ancestry residing in Michigan. Growth, 1959, 23, 55-71. Steggerda, M., & Densen, P. Height, weight, and age tables for homogeneous groups. Child Develpm., 1936, 7, 115-120. Steggerda, M., & Shaffer, C. Anthropology and human genetics. Carnegie Znst. Wash. Yearb., Annu. Rep. Dep. genet., 1942, No. 41, 211-216. Sternberg, G. M. Statistics of the measurements of recruits. Rep. Surg. Gen. Army, 1892 (also Reps. Surg. Gen. Army, 1894-96). Sternberg, G. M. Statistics of the measurements of recruits. Rep. Surg. Gen. Army, 1897. 55th Congr., 3rd Session, House Documents, 1898, 2. Stewart, T. D . Anthropology and the melting pot. Smithsonian Rep., 1947, 315-344. Stockton-Hough, J. Statistics relating to seven hundred births (white) occurring in the Philadelphia Hospital (Blockley) between 1865 and 1872. Phila. Med. Times, 1885, 16, 92-94. Stoudt, H. W., Damon, A., & McFarland, R. A. Heights and weights of white Americans, Hum. Biol., 1960, 32, 331-341. Streit, W. K. Exercise satisfies a primary need both of child and adult. Phys. Edur., 1951,

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Howard V . Meredith Sturzebecker, R. L. Sex differences in anthropometric measures and ratios of college students aged 18 to 21. Res. quart., 1950, 21, 366376. Sumner, E. E., & Whitacre, J. Some factors affecting accuracy in the collection of data on the growth in weight of school children. J . Nutrition, 1931, 4, 15-23. Suski, P. M. The body build of American-born Japanese children. Biometrika, 1933, 25, Parts 111 and IV, 323-352. Tanner, J. M. Education and physical growtb. London: Univer. London Press, 1961. Tanner, J. M. Growth at adolescence. Oxford: Blackwell Sci. Publ., 1962. Townsend, C. W. Some statistics on weight of infants, sex, and fetal heart-rate. Boston Med. E. Surg. J., 1896, 134,484-485. Trotter, M., & Gleser, G. C. Trends in stature of American whites and Negroes born between 1840 and 1924. Amer. J . Phys. Anthrop., 1951, 9 n.s., 427-440. Tuddenham, R. D., & Snyder, M. M. Physical growth of California boys and girls from birth to eighteen years. Univer. Calif. Publ. Child DeveIpm., 1954, 1, No. 2. Vickers, V. S., & Stuart, H. C. Anthropometry in the pediatrician’s office: Norms for selected body measurements based on studies of children of North European stock. J . Pediat., 1943, 22, 155-170. Wallis, R. S. How children grow: An anthropometric study of private school children from two to eight years of age. Univer. Iowa Stud. Child Velf., 1931, 5, No. 1. Weisman, S. A. Contour of the chest in children: 111. Environment. Amer. J . Dis. Childh., 1935, 49, 52-59.

Westerfeld, R., Flynn, M. A., & Jackson, R. L. Growth of children in the first year of life. Unpublished study. Univer. of Missouri Sch. Med., 1963. Whitacre, J. Some body measurements of Texas school children. Texas Agr. exp. Station, 1939, Bull. No. 567. White, R. M. Body build and body weight in 25-year-old Army men. Hum. Biol., 1956, 28, 141-145. Wilson, C. A., Sweeny, M. E., Stutsman, R., Chesire, L. E., & Hatt, E. The MerrillPalmer standards of physical and mental growth. Detroit: Merrill-Palmer School, 1930.

Wolff, G. Further results on the trend of weight in white school children. Child Develpm., 1941, 12, 183-205. Wolff, G. A study of height in white school children from 1937 to 1940 and a comparison of different height-weight indices. Child Develpm., 1942, 13, 65-77. Woodbury, R. M. Statures and weights of children under six years of age. US. Dep. Labor, Childr. Bur., 1921, Publ. No. 87. Woolley, H. T. An experimental study of children at work and in school between the ages of fourteen and eighteen years. New York: Macmillan, 1926.

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‘DISCRIMINATION LEARNING SET IN CHILDREN’

Hayne W , Reese STATE UNIVERSITY OF NEW YORK AT BUFFALO*

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I The writer has benefited from helpful suggestions and criticisms by several colleagues, especially Dr. Billey Levinson, and acknowledges a debt of gratitude. The preparation of this chapter was supported in part by a grant from the Graduate School of the State University of New York at Buffalo. ’Formerly “The University of Buffalo.”

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I. Introduction A “learning set” is acquired through practice on problems that have a common basis of solution. The learning set has been formed when the common solution has been learned, and in most experimental situations the development of a learning set results in the solution of a new problem with no more than one error. This chapter deals only with “discrimination learning set,” although there are several other kinds of learning set, for example “oddity learning set” (e.g., Martin & Blum, 1961) and “reversal learning set” (e.g., Harlow, 1949). Discrimination learning set (hereafter called “learning set”) has been more thoroughly investigated than the others; and in spite of the use of many different experimental procedures, a “standard” technique for establishing a learning set can be described. The subject is given practice on numerous two-stimulus simultaneous discrimination problems, using a different pair of stimuli in each problem. In each problem one stimulus is correct, the position of the correct stimulus is shifted to the right and left in a randomly determined order, and each response to the correct stimulus is rewarded. Some small, fixed number of trials is given on each problem; after the fixed number of trials has been given on one problem, a new pair of stimulus objects is introduced, initiating a new problem, and the fixed number of trials is given on the new problem. Improvement from problem to problem in the performance level on a given within-problem trial is used as a measure of interproblem transfer or of learning-set formation. As a resuIt of the formation of the learning set, problems that would have been difficult are solved in one trial; whether or not the subject responds to the correct stimulus on the first trial of a new problem, the response on the second trial is correct. In most of the studies of learning-set formation in monkeys some arbitrary number of problems has been given, but in many of the studies using children new problems have been presented until the subject reaches some criterion indicating the formation of a learning set. For example, Kaufman and Peterson (1958) continued training until the subject met a criterion of at least 90% correct responses on the second trials of 48 consecutive problems, and Levinson and Reese (1963) trained subjects to a criterion of 93% correct on trials 2 through 4 of 5 consecutive problems (only 1 error was permitted in 15 responses). The response on the first trial of a problem was excluded because the first trial is insoluble-it functions as an information trial. The occurrence of 1-trial learning may not always indicate that a learning set has been acquired. Jarvik (1953) obtained I-trial learning on the first

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Discrimination Learning Set in Children problem given to experimentally naive monkeys, by associating the negative stimulus with a strongly noxious taste on a pretraining trial. However, transfer was minimal. The problem of explaining learning-set formation is simplified by distinguishing between learning set and performance set, although the distinction has not always been made clear in the research literature. The term “learning set” can be used to refer to the immediate solution of new problems, or 1-trial learning, developed in a series of problems of the same kind. Performance sets may increase the rate of learning (Irion, 1948), but do not produce 1-trial learning. Some performance sets do not require practice on one kind of problem; for example, “warm-up” acquired in one kind of task may transfer to a different kind of task (Cantor, 1955; Norcross & Spiker, 1957; Thune, 1950). Other performance sets, however, seem to require practice on a single kind of problem, and have perhaps for this reason sometimes been confused with learning sets. These performance sets might be designated “learning-to-learn,” since the phrase seems to be descriptively accurate, but “learning-to-learn” has frequently been used as a synonym of “learning set.” An alternative label that has been used is “discrimination set,” but the similarity of the term to “discrimination learning set” might lead to confusion. Learning-to-learn or discrimination set develops when the subject is given practice on a series of similar problems, such as paired-associates tasks, which may have a common solution only in the trivial sense that in each problem there are several stimuli that are to be paired with different responses. This “common solution” is usually given in the instructions, however, and even after it has been learned, the subject does not solve a new problem in one trial. Meyer and Miles (1953), for example, gave 20 serial learning problems to college undergraduates, and although the subjects were not required to recall the items in a list in order, they made about 40% correct responses in 5 trials on the first list and only about 57.5% correct in 5 trials on the last, indicating that the subjects were still far from 1-trial learning. Discrimination set probably includes observing (orienting) responses (e.g., Lipsitt, Castaneda, & Kemble, 1959) or increased attention to relevant cues and ignoring of irrelevant cues (e.g., Zeaman, 1959).3 It may also involve suppression of specific transfer between problems (Riopelle, 1953), and in human subjects the use of such aids to learning as rehearsal and mnemonic devices (Spiker, 1960) . Kurtz (1955) found interference when pretraining stimuli differed on one dimension and transfer-task stimuli differed on another dimension (although they were highly similar to the pretraining stimuli). Similarly, Bensberg (1958) found that in mental defectives an inappropriate “attention set” established in pretraining produced interference, relative to a control condition, and an appropriate attention set produced facilitation. In human subjects, then, attention may be specific to a single dimension, probably as a result of verbal labeling.

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Hayne W.Reese The development of discrimination set results in rapid, but not immediate, solution of new problems. Furthermore, discrimination set is like other performance sets in that it is apparently nonspecific, in the sense that the stimuli used in the different problems may differ on different dimensions. In a paired-associates task, for example, training on problems in which the stimuli are nonsense figures may result in the development of a discrimination set, which may transfer to a paired-associates task with nonsense syllables as stimuli (Duncan, 1958). Learning set, on the other hand, seems to require training on problems with stimuli that differ on the same dimensions.

11. Review of the Literature A review of the studies of learning set in children is made difficult by the relatively small number of such studies using comparable experimental procedures; although a fairly large body of work exists, it consists of studies using a wide diversity of experimental techniques. Studies differ in the nature of the stimuli used, ranging from small toys to Greek letters, from complex stimuli that the child can not label to verbal lists. There are differences in instructions, number of problems per day, and the manner in which the position of the correct stimulus is varied from trial to trial; the number of problems has varied from as few as 5, each in turn learned to a criterion, to hundreds of problems with 3, 4, 6, or some other fixed number of trials. Because of these and other procedural variations, many of the comparisons across studies are of doubtful validity, and conclusions drawn from such comparisons must be tentative.

A. EXPERIMENTAL VARIABLES This section is organized around experimental variables that have been shown to influence learning-set formation in monkeys. 1. Number of Problems When some small, fixed number of trials is given on each problem, the learning set is acquired gradually. Procedural variations influence the speed of learning-set formation, but in general monkeys require well over 100 problems (Harlow, 1959), and children well under 100 problems. In one of the earliest studies of learning set in children, Kuenne (in Harlow, 1949) gave 84 6-trial problems to 17 preschool children. The median number of problems required to reach a level of almost 100% correct responses on trials 2 through 6 was apparently 43 to 56 (estimated from Fig. 5, p. 55, Harlow, 1949).

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Discrimination Learning Set in Children About 24% of the subjects had not acquired the learning set by the end of the experiment. Koch and Meyer (1959) also gave 6-trial problems to preschool children, but used pattern stimuli, whereas Kuenne used stereometric objects. Koch and Meyer’s subjects required a median of 84-108 problems to reach criterion. Levinson and Reese (1963), using 4-trial problems with stereometric objects, obtained a median of 20 problems to criterion in preschool subjects. 2. Number of Trials per Problem Learningset formation in monkeys is a function of the number of trials presented, regardless or how these trials are organized into problems, provided the number of trials per problem is between 3 and some number greater than 12 but less than 50. When more trials than the upper limit are given on each problem, the rate of learning-set formation is retarded (plotting performance against the number of trials, not the number of problems) (Harlow, 1959). Only one study has investigated this variable in children. Using preschool children with an average IQ greater than 130, Harter (1962) found that a group given 8 trials per problem reached criterion in about the same number of trials (but about half as many problems) as a group given 4 trials per problem, even though the learning-set criterion was stricter for the 8-trial group. Comparisons across studies using different numbers of trials per problem are of doubtful or unknown validity. For example, Levinson and Reese (1963) gave 4 trials on each problem, and obtained faster acquisition of the learning set than Kuenne (in Harlow, 1949), who used 6-trial problems. The details of Kuenne’s procedure were not published, however, and no conclusion can properly be drawn from the comparison. Similar objections can be raised to the other possible comparisons.

3. Kind of Stimuli Learning-set formation is faster in monkeys when stereometric objects are used than when planometric stimuli or patterns are used. Stereometric objects usually differ on many stimulus dimensions; planometric stimuli (flat blocks) and pattern stimuli (painted or pasted on cards) differ on a limited number of dimensions. The only study that used more than one kind of stimuli with human subjects found no significant effect of the stimulus variable, but the subjects were mental defectives (deHaan & Wischner, 1963). One group of mental defectives was trained with stereometric objects, and another group with photographs of the objects. Three trials were given on each of 120 problems. There were 35 subjects in each group, probably yielding a sufficiently powerful test of the null hypothesis, but the difference between the groups

Huyne W . Reese in rate of learning-set formation (favoring the group trained with stereometric objects) was small and not statistically reliable. The results of deHaan and Wischner’s study seem to be inconsistent with the hypotheses that (a) discriminations between stereometric objects are learned faster than discriminations between pattern stimuli, and (b) the amount of within-problem learning is related to the rate of learning-set formation (see Section C, 2 ) . Stevenson and McBee (1958) found that young children learned a 3-stimulus discrimination problem faster when stereometric objects (cubes) were used than when pattern stimuli (painted squares) were used; and House and Zeaman (1960) obtained the same result in mentally retarded children, using a 2-stimulus discrimination probIem. The first hypothesis, then, has experimental support, The second hypothesis is known to be true for monkeys (Harlow, 1959), and has been confirmed in one study with children (Harter, 1962). The one possible comparison across studies does not agree with deHaan and Wischner’s results, but is of unknown validity. Kuenne (in Harlow, 1949) and Koch and Meyer (1959) gave 6 trials on each problem; Kuenne used stereometric objects, and Koch and Meyer used pattern stimuli. Kuenne’s subjects met criterion in a median of 43-56 problems, and Koch and Meyer’s subjects required a median of from 84 to 108 problems. The criterion used by Kuenne was not reported, nor were other details of her procedure given, and the comparison is therefore not justified. The deHaan and Wischner results may be interpreted as indicating that photographs of stereometric objects differ on as many dimensions as the stereometric objects themselves. 4. Contigiddy of Stimulus and Loctis of Response The spatial contiguity of the stimulus and locus of response affects learningset formation in monkeys (e.g., Schuck et al., 1961). The effect of this variable on learning-set formation in children has not been investigated, but the data of Murphy and Miller (1959) lead to the prediction of an effect; a separation of 6 in. between the stimuli and response loci retarded discrimination learning in fourth-grade subjects. 5. Size of Stimuli Increasing the size of pattern stimuli, by covering increasing percentages of the centers of the background cards, increases the rate of acquisition of learning set in monkeys (e.g., RiopeIIe et al., 1958). According to Schuck et al. (1961) the effect results from variation of the separation of the stimuli from the response loci when the area covered is varied. Only one study (Koch & Meyer, .1959) using children as subjects has investigated this effect, and it was reported that “The effects of variation in the

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Discrimination Learning Set in Children size of the differential cues proved to be less striking with the children than it has been shown to be with monkeys” (p. 388). (No supporting data were given.) The correlation between mental age and performance increased as the area decreased.

B. SUBJECTVARIABLES 1. Ontogenetic Trends The data of Hayes et al. (1953) suggest a relationship between speed of acquisition of learning set and chronological age. Two 2-year-old subjects and a 4-year-old subject with normal intelligence did not acquire a learning set in 6 problems, each learned to a criterion; but a bright 4-year-old and a 6- and a 7-year-old acquired the learning set in 1 or 2 problems. Roberts (1932) also found age differences within the preschool range. The subjects were trained to criterion on each of 3 problems, in which the common solution was to respond to a door of the same color as a stimulus (toy airplane). (The problems could be considered as “matching from sample” or as discrimination learning problems.) Two-year-olds did not improve in trials to criterion over the problems, but 3-, 4-, and 5-year-olds did. The latter 3 groups were not significantly different from each other. (In these 3 groups there was more improvement between the second and third problems than between the first and second, contrary to the conclusion of Section C, 2, but the problems were 3-stimulus discriminations.) Levinson and Reese (1963) included 53 subjects ranging from 3 to 5.5 years of age, and found no significant correlation between chronological age and learning rate on standard learning-set problems. The Pearson correlation between CA and days to criterion (at a rate of 10 problems per day) was .085. Age differences within the preschool range may affect learning-set formation only when some procedure other than the standard one is used. When a wide age range is considered, the data clearly show a relation between acquisition rate and chronological age. Levinson and Reese (1963) found college students significantly superior to fifth-grade children, and fifthgraders significantly superior to nursery school children. All 3 groups were significantly superior to aged subjects obtained from old-age homes and Golden Age clubs; but retired professional subjects performed at a significantly higher level than the other aged groups, and acquired the learning set almost as fast as the college sample. Harter (1962) used a factorial design with 3 levels of I Q (70, 100, 130) and 3 levels of mental age (5, 7, 9 years). The trends indicated that with MA constant, performance improved with decreasing CA (increasing IQ) ; and with IQ constant, performance improved with increasing CA (increasing MA). It is likely that the age differences obtained by Levinson and Reese are also attributable to intellectual variables.

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Hayne W . Reese 2. Effects of Intellectual Variables A. Mental Age. (1) Among normal preschool children, the speed of acqui-

sition of learning set is directly related to mental age. The data of Hayes et al. (1953) suggest such a relation; one of two 4-year-old subjects, with an IQ of 136, was clearly superior to the other $-year-old, who had an IQ of 106. Roberts (1932) found that normal preschool children with a mental age of two were inferior in interproblem transfer to preschool children with higher mental ages, but the tasks could be considered to be matching-fromsample rather than discrimination learning problems. Koch and Meyer (1959) obtained a Pearson correlation coefficient of -.59 ( p < .ol) between days to learning-set criterion and mental age. (It may be noted that with chronological age held constant, variation in mental age results in variation in IQ. Whether the correlation should be attributed to variation in mental age or IQ is debatable.) ( 2 ) With chronological age held constant, the speed of acquisition of learning set is an inverse function of the degree of mental retardation, and mental defectives are slower than normal subjects. Ellis (1958) gave 10 problems, each learned to a high criterion, to 100 mental defectives divided into a high and a low mental-age group. The high group was significantly superior to the low group, and the superiority was also found in 2 subgroups matched for mean chronological age. There was, however, no difference among mental-age groups with mental ages greater than 7 years. (It might be noted that in the high group the learning set was maximal after the first problem, in line with the conclusion of Section C, 2 ; and the greatest improvement in the low group was between the first and second problems, although there was further improvement after the second problem.) Wischner et al. (1962) confirmed this finding, using 3-trial problems. Kaufman and Peterson (1958) gave 3-trial problems to 8 mentally retarded children with IQs from 50 to 75 and 6 normal children with IQ’s from 90 to 109. The groups were closely matched for mean chronological age; the age range within groups was 9 to 1 2 years. The retarded subjects were significantly inferior to the normal; 5 of the 6 normal subjects and only 1 of the 8 retarded children reached criterion in the first 48 problems. In the second block of 48 problems, the other normal subject and 4 more retarded subjects reached criterion. Stevenson and Swartz (1958) studied the effects of mental age by comparing normal children with low- and high-grade mental defectives. The normal children and high-grade defectives had about equal mean chronological ages, and the low-grade defectives were older. The normal group was superior in speed of acquisition of the learning set to the high-grade defectives, and the high-grade superior to the low-grade. B. Effect of IQ. Levinson and Reese (1963) found no significant evidence

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Discrimination Learning Set in Children of a relation between speed of acquisition of learning set and I Q in normal fifth-grade children. The Pearson correlation coefficient between problems to criterion and IQ was -.16 (excluding 6 subjects who did not reach criterion; they did not differ significantly in IQ from the children who reached criterion). Comparisons of mental defectives with children of normal intelligence, matched for mental age, suggest a relation between IQ and learning-set formation. Girardeau ( 1959) compared mongoloids with normal preschool children, matching the groups in mean and range of mental age. The subjects were trained to a criterion on each of 5 problems. The mongoloids were significantly inferior to the normal group in learning-set formation; the mongoloid group had not reached by the fifth problem the level of the normal group on the second problem. Plenderleith (1956) found no significant difference in problems to criterion between groups of retarded and normal children. The groups had approximately equal mental ages (about 5.8 years), but the retarded group was about twice as old as the normal group (CA’s 10.7 and 5.2 years). The subjects were given 6-trial problems until they made no errors on 3 consecutive problems und were able to verbalize the solution. The mean number of problems required to reach this rather strict criterion was only about 12.4, considerably fewer than was required by Koch and Meyer’s or Kuenne’s somewhat younger subjects with normal IQ’s (see Section A, 1). Plenderleith used pictures as stimuli, and made the first response on the first problem incorrect for all subjects “in an attempt to minimize the effect of first trial success and position preferences” (p. 109). It would appear that the attempt was highly successful.

C. RESPONSEVARIABLES 1.

Shape of Learning-Set Acquisition Curves

The learning-set acquisition curves of studies in which children were trained to criterion on at least the first problem have been saltatory; the performance level increased from the first to the second problem, but increased very little thereafter (Section C, 2 ) . This effect is not obtained in monkeys (e.g., Riopelle, 1953). In studies using a fixed number of trials per problem the curves have usually been ogival or positively accelerated in monkeys (Harlow, 1959) and children. Levinson and Reese (1963) obtained an ogival acquisition curve, plotting the data of 53 preschool children in 5-problem blocks; but the curves of relatively homogeneous subgroups were positively accelerated. Subgroups were formed on the basis of the number of problems required to attain a learning-set criterion. The “criterion-reference” method of forming homogeneous subgroups has the disadvantage that the data points representing performance on the criterional problems are spuriously high, and the data point

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Hayne W . Reese for the problem immediately preceding the criterional problems is spuriously low (Hayes & Pereboom, 1959). In comparisons among subgroups formed by this method these disadvantages are not present, since the data points of each subgroup are affected equally by the selection. Subgroup differences are real, but the shapes of the curves may be spurious. Although a paraboIic equation gave a highly accurate fit to the data points of each subgroup in Levinson and Reese’s study, the curves could also be characterized as having two phases, with slow improvement in the first phase and rapid improvement in the second. (Selection affected the data points in only the second phase; the true second-phase curve is probably negatively accelerated.) The inflection points were at about 65% to 75% correct. The first phases of the subgroup curves overlapped, although they differed in duration, and the second phases were identical in slope. Similar curves were obtained for fifth-grade subjects, but with inflection points between 55% and 60% correct. Koch and Meyer (1959) also used the criterion-reference method to form subgroups, but presented curves only for the best and worst subgroups. Data points were given for blocks of 36 problems, with 1 data point for the best subgroup and 5 for the worst subgroup. The curve of the worst subgroup could be characterized as positively accelerated or as having two phases, with an inflection point at about 60% correct. The curve of an intermediate criterion-reference subgroup in Kuenne’s (in Harlow, 1949) study was of the same type, with an inflection point at about 75% correct. The second phase was steeper than the curve of the best subgroup, however; and the curves of the best and worst subgroups seemed to be parallel to each other, although they differed in absolute level. It might be argued that the true curve is ogival, and that the best subgroup was in the stage of negative acceleration, but its final level was no higher than the final level of the intermediate subgroup. Kuenne presented data for blocks of 14 problems, which may be so gross that inflection points were lost. Kaufman and Peterson’s (1958) curves for %trial problems were negatively accelerated, but data points were given for blocks of 16 problems. Using 3-trial problems and mentally retarded subjects, Wischner et al. ( 1962) obtained roughly ogival curves, plotted against 12-problem blocks. The curves of criterion-reference subgroups were similar in form, but displaced to the right, as in Levinson and Reese’s study. The curve most clearly showing two phases, for 5 subjects who met criterion in 120 problems, had an inflection point at about 60% correct. Harter (1962) plotted the data of individual subjects in 5-problem blocks, and found that for most subjects the curves had two phases. The first phase of some of the curves was flat, but the majority of the curves showed definite improvement in the first phase.

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Discrimination Learning Set in Children Levinson and Reese (1963) and Wischner et al. (1962) both found slow, gradual improvement in subgroups that did not meet the learning-set criterion. Levinson and Reese's no-criterion subgroup in a sample of fifth-grade children of normal intelligence had improved to about 60% correct responses on trials 2 through 4 by their thirtieth (and last) problem. The no-criterion subgroup of Wischner et ul., attained a final level of about 65% correct. 2. Amount of Within-Problem Learizing According to Harlow (1959), the rate of learning-set formation in monkeys is directly related to the amount of within-problem learning, provided the amount of learning is less than some upper limit (see Section A, 2 ) . For human subjects the relation is much more complex. A. Discrimination Problems. (1) Young children. Hatter's (1962) data suggest that the rate of learning-set formation increases as within-problem learning increases. A group given %trial problems had a smaller percentage of errors on trials 2 through 8 than a group given 4-trial problems had on trials 2 through 4, suggested that there was more within-problem learning in the former group (see Section A, 2). When young children are trained to criterion on their first problem, a learning set is apparently acquired, and further training on other problems produces little further improvement in performance. Using 6-choice discrimination problems, Roberts (1933) obtained immediate solution of all problems after the first one (except problem 4, when the basis of solution was modified for the first time) in preschool and young orphanage children. Girardeau (1959) trained his subjects to criterion on each of 5 problems. The curve of his normal preschool group rose significantly from the first to the second problem, but did not change reliably over the remaining 4 problems. The asymptote was about 85% to 97% of perfect performance. The data of 6 children trained by Hayes et al. (1953) suggest that this effect may have an age limit. Three of their subjects, with chronological ages of 4, 6, and 7 years, made only 2 errors, or fewer, after the first problem was learned to criterion (the 4-year-old had an IQ of 136); but the other three subjects, including two 2-year-olds and another 4-year-old (IQ 106), made relatively large numbers of errors on the first 6 problems, each learned to criterion. Ellis et al. (1962) trained preschool children to criterion on the first problem, then gave 100 additional 6-trial problems. The performance curve over the fixed-trial problems rose about 10 percentage points to a maximum of almost 90% correct responses. Bowes and Wischner (1959) obtained additional evidence that further improvement occurs with continued training, but they used mentally retarded subjects with an average IQ of 39. One group was

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Hayne W . Reese trained to criterion on each of 60 problems; a second group was trained to criterion on each of 12 problems; a third group, 3 problems; and a fourth group, none. The last 3 groups were given additional 3-trial problems to bring the total number of problems to 120. O n the first 60 problems the group trained to criterion on all 60 made significantly fewer errors than the groups trained to criterion on 12 or 3 problems. On the first 60 and last 60 problems, the latter 2 groups were not significantly different from each other, and were significantly superior to the group given only 3 trials on each problem. One other study (Wischner & O’Donnell, 1962) obtained a similar effect in the formation of a “concurrent” learning set by subjects with a mean CA of 6.8 years. The subjects were trained to criterion on each of 5 “lists.” Each list comprised several pairs of objects, always presented in the same sequence. One object of each pair was correct. The first list included 5 pairs of objects, and the other Iists each had 10 pairs. The most marked improvement in performance was between the first and second lists, but there was some further reduction of trials to criterion over the other lists, and an even greater reduction of errors to criterion. ( 2 ) Older children. Stevenson and Swartz (1958) gave problems with common objects as stimuli (e.g., balloon, comb, whistle) to children with a mean CA of 11.6 years, and trained the subjects to a criterion of 5 consecutive correct responses on each problem. No data were given for the first 4 problems separately, but the data presented indicate that the learning-set formation was extremely rapid. Performance averaged about 80% correct in the first block of 4 problems, and about 100% correct in the remaining blocks. The group required a mean of only 8.1 problems (including 5 criterional problems) to reach a learning-set criterion of 5 successive problems solved within a maximum of 6 trials per problem. It should be pointed out that no study of learning set in preschool children is comparable to Stevenson and Swartz’s study. Preschool children were trained to criterion on each problem, and continued training until a learning-set criterion had been attained in only one study (Ellis, et al., 1962), which used different procedures and different criteria from Stevenson and Swartz. It would therefore be inappropriate to conclude from a comparison of the studies reviewed above that the speed of learning-set formation is or is not the same in younger and older children. B. Paired-Associates Problems. ( 1 ) Young children. The evidence from the only available study suggests that with two paired associates on each problem, training preschool children to criterion on a single problem produces a maximal learning set. Shepard (1957) used the successive discrimination problem, which may also be analyzed as a motor paired-associates task with 2 stimulus-response pairs. She trained preschool children to criterion on the first problem, then gave 8 trials on each of 5 additional problems. The stimuli, upper

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Discrimination Learning Set in Children and lower case Greek letters paired at random, were presented one at a time on the middle box of three boxes. For one stimulus in each pair, the subject was rewarded for responding to the left box, and for the other stimulus, the right box. The group improved significantly from the first to the second problem, but showed no further reliable change after the second problem. The asymptotic level was between 5. 5 and 6.0 correct responses, out of a possible 7.0. (2) Older children and adultr. Studies of the performance of older children and adults on successive paired-associates tasks indicate that the effect of within-problem learning on the amount of interproblem transfer depends on the number of paired associates to be learned in each problem. (a) With four paired associates on each problem, training to mastery on a single problem produces more transfer than multiple-problem training in which the problems are learned to only a low level of proficiency. Adams (1954) compared single- and multiple-problem training in basic airmen trainees. Each problem was a motor paired-associates task; 4 stimuli, differing in the spatial arrangement of 2 figures, were presented one at a time in each problem, and each stimulus was to be associated with a different push-button. The single-problem group was given 192 trials on a single problem, then 24 trials on a test problem. The multiple-problem group was given a total of 192 trials, but on twenty-four 8-trial problems (2 presentations of each stimulus), followed by the 24-trial test problem. O n the test problem the single-problem group was superior to the multiple-problem group. O n the training trials the singleproblem group attained a high level of proficiency, but the multiple-problem group achieved only slightly better than 50% correct responses by the end of training. Morrisett and Hovland (1959) used the same tasks as Adams, but with twelfth-grade children. The results confirmed Adams’s; the single-problem group was superior to the 24-problem group during training and on the test problem. (b) Multiple-problem training produces more transfer than single-problem training when all problems are learned to mastery. Morrisett and Hovland (1959), two of whose groups are discussed above, included another group given three 64-trial problems (16 trials per stimulus). The single-problem group was slightly superior to the 3-problem group during most of the training phase, but about equal over the last 50 or 60 trials. O n the test problem, the 3-problem group was superior to the single-problem group. The 3-problem group reached a level of almost 90% correct responses by the last 8 stimulus presentations of the first problem, and its performance on the second problem was superior to the performance of the 24-problem group on the test problem, again confirming conclusion (a). The performance of the 3-problem group on its second problem was highly

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Hayne W . Reese similar to the performance of the single-problem group on its second problem (the test problem), especially on the first 8 trials of these problems. Since 16 presentations of each stimulus provided enough training for a solution of the first problem (in the 3-problem group), the 48 presentations of each stimulus in the single-problem group should produce overlearning. The comparison of the performance on the second problems of these groups therefore suggests that overlearning did not increase the amount of interproblem transfer. The performance of the 24-problem group improved over the course of training, indicating that interproblem transfer was developing, but performance had not attained the level of the other 2 groups by the end of training. The low level of within-problem learning in this group produced interproblem transfer, but the development of the transfer was slower than with high levels of withinproblem learning. Callantine and Warren (1955) obtained data that extend the conclusion to another kind of paired-associates task. They studied interproblem transfer in college students, using different numbers of concept formation problems in different groups, and concluded, “. . . when conditions permit relatively complete learning by all Ss, those Ss which have been trained on many problems show a more generalized problem solution than do those trained on only a very few problems” (p. 366). A group trained on only one concept-formation task was significantly superior to a control group given only the transfer task, but this difference could be attributed to the effects of warm-up. Greenberg and Underwood (1950) gave 4 paired-associates problems, each learned to criterion, and each having 10 pairs of adjectives. There was significant improvement in speed of original learning from the first to the second problem, but no further improvement with further training. Although the results do not confirm the conclusion stated above, they do not necessarily contradict it, since there was a floor effect. The mean number of trials to criterion (8 correct responses on a trial) decreased from almost 13.0 on the first problem to about 9.5 on the second and third, and about 9.0 on the fourth. (c) With 13 paired associates per problem, multiple-problem training produces more transfer than single-problem training, regardless of the amount of within-problem learning when the total number of trials is fixed. In the studies reviewed in the preceding two sections, the number of problems was varied between groups, but the total number of trials was held constant. Duncan (1958) varied both the number of problems and the total number of trials, using problems with 1 3 paired associates. The subjects were college undergraduates. Transfer increased significantly with increase in the number of problems and with increase in the total number of trials, but the interaction of these variables was not significant. For any given number of problems, then, an increase in the total number of trials, and therefore an increase in within-

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Discrimination Learning Set in Children problem learning, increased the amount of transfer; and for any given number of trials, an increase in the number of problems, and therefore a decreuse in the number of trials per problem, increased the amount of transfer. A study by Cook (1959) suggests that the difference between the results of the studies of the previous two sections and Duncan’s results is attributable to differences in the number of paired associates and not to differences in task difficulty as such. Cook studied transfer between problems involving the reproduction of complex patterns. Each pattern consisted of 5 subpatterns formed by arrangements of 5 pegs of each of 5 colors on a peg board. The subjects were trained to a criterion on each pattern. Cook found that transfer was generally greatest from the first pattern to the second. Titard and Loos (1954) obtained a similar finding in mental defectives whose average age was 20 years, and average IQ 34. The subjects were trained to criterion on each of 4 forms of the Minnesota Spatial Relations Test. The greatest improvement, in terms of time for solution, was between the first and second tasks. The findings of these studies are in agreement with the results of the preschool studies, which found maximal transfer after training to criterion on a single discrimination problem, and in disagreement with the results of the pairedassociates studies that found greater transfer from multiple-problem training than from single-problem training. Interproblem transfer in complex paired-associates tasks may involve not learning set but some kind of performance set (see also Section I). I n a separate report on the performance of a group given ten 2O-trial paired-associates problems, Duncan (1960) noted that most of the interproblem gain occurred in the second fifth of training on each problem (trials 5 through 8 ) , later than in studies of learning set using 2-stimulus discrimination problems. Duncan (1958), in fact, attributed his results to the development of a performance set: “Varied training seems to force S to pay close attention to every stimulus in every set . . . . If S does this, he should be able to discriminate easily among the stimuli within a list and between lists, thus minimizing both intralist and interlist interference” (pp. 71-72). 3. Retenton of Learned Associutions Several studies have shown remarkably high retention of responses to specific stimuli in monkeys (e.g., Mason et ul., 1956; Strong, 1959), but the extent to which specific stimulus-response associations are retained by children in a learning-set task has not been investigated. Wischner et al. (1962), however, found that the learning set itself was retained by mentally retarded subjects over a 6-month interval. (The problems used in the retention test may have also been used in the original training. If so, there was no retention of specific stimulus-

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Hayne W . Reese response associations over the interval, since trial-1 performance on the retention test was at the chance level.) A study of Zeaman and House (1962) suggests that mentally retarded subjects learn both approach and avoidance tendencies, and equally well. The subjects were trained on an “ambiguous cue” problem and a standard discrimination problem stimultaneously. O n half the trials of the ambiguous cue problem an “ambiguous” stimulus (C) was presented with the positive stimulus (A), and on the other half with the negative stimulus (B). Two other stimuli (D and E) were used in the standard problem. Performance on the BC discrimination was not significantly different from performance on the standard problem, and performance on both of these discriminations was superior to AC performance. Assuming that the partial reinforcement of the approach response to the ambiguous stimulus results in increments in the approach tendency and has no effect on the strength of the inhibitory tendency, the results can be explained on the basis of response competition. O n AC trials 2 approach tendencies complete, and performance is inferior to performance on BC trials, on which both response tendencies are correct (approach C, avoid B). The analysis requires that there be no difference between BC and DE performance, since each is noncompctitional, and as noted above, the difference was not statistically significant. The difference was also relatively small (mean errors: DE, 21.1; BC, 28.0; AC, 43.0). 4. First-Trial Outcomes There are more errors following an initial correct response than following an initial error in monkeys (Harlow, 1959) and children. House and Zeaman ( 1958b) found significantly more errors in imbeciles following the presentation of the positive stimulus alone than following the presentation of the negative stimulus alone, but as House and Zeaman suggested, this result may indicate that these subjects tend to approach novel stimuli (see also Zeaman and House, 1962). Ellis et al. (1962) obtained a similar result, not attributable to such an approach tendency. There were more errors on trial 2 of the problems in a group of mental defectives whose first-trial responses were always correct (both objects baited) than in a group whose first-trial responses were always incorrect (neither object baited). Levinson and Reese (1963) found twice as many errors on trials following a correct initial response as following an initial error in normal preschool children. In a 3-stimulus discrimination problem, Stevenson and Weir (1961) found a greater proportion of errors following a correct response than following an error in 5-, 7-, and 9-year-olds, but the opposite in 3-year-olds. The age range of the youngest group was 3.0-3.9 years, compared with a range of 3.0-5.5 in Levinson and Reese’s youngest group, whose median age was 4.3 years.

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Discrimination Learning Set in Children 5. Transfer of Learning Sets Learning sets transfer and may interfere with the acquisition of a different learning set in monkeys. Shifting the subjects from one kind of problem to another brings about a large number of errors, but as the shifts continue, progressively fewer errors occur (Harlow, 1959). Only one study provides data on the transfer of a learning set in children, and it allows no conclusion to be drawn about possible interference with the acquisition of a different learning set. Harlow (1949) reported reversal learning-set data for a group of nine preschool children who had previously acquired a discrimination learning set. The group required no more than 14 problems to acquire the reversal learning set; the performance level was almost perfect in the second block of 14 problems (estimated from Fig. 10, p. 59). 6 . Systematic Patterns of Responses Systematic patterns of responses have been observed in the behavior of subjects in discrimination problems, not only after a problem has been mastered, when all responses are correct, but also in the “presolution” period. The systematic response tendencies occurring in the presolution period have been called “hypotheses” (Krechevsky, 1932) and “error factors” (Harlow, 1949; 1950; 1959). The studies summarized below used Harlow’s error factor model. A. Position Preference. A position preference is indicated by repeated responses to the left or right position, when the position of the correct stimulus object changes at random. Harlow (1959) has concluded that position preference is an “essentially unimportant” error factor in rhesus monkeys. Among human subjects position preference is a more important source of error in severely mentally retarded subjects than in high-grade defectives or in normal subjects, and more important in younger than in older normal subjects. Stevenson and Swartz (1958) used a corrective procedure designed to reduce position preferences rapidly an average of 11.2 times per subject in a low-grade mentally defective group, and less than 1.0 time per subject in normal and high-grade defective groups. Ellis (1958) tested low- and highgrade defectives, and observed that of eight subjects dropped from the experiment for failure to learn the first problem, all were in the low-grade defective group, and four . . fixated on a position response and persisted in this behavior for at least 200 trials” (p. 81). Of the normal preschool subjects in a study by Ellis et al. (1962), 31% showed position preferences, compared with 83% of the mentally retarded subjects. Eighty per cent of the retarded subjects showed position preferences in their second hundred problems. House and Zeaman (1958b) obtained results which appear to contradict the trend, since only 4 of 14 imbeciles in their study showed position preferences. Before the beginning of training, however, the subjects were given a ‘I.

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Hayne W . Reese series of learning-set problems on each of which they were trained to criterion. The pretraining continued until the subjects met a learning-set criterion of 20 correct responses on a new problem in the first 25 trials. Even if the pretraining did not establish a strong learning set, it must have reduced position preferences. Schusterman ( 1963) found a strong position preference in 3-year-olds, in a probability learning task involving a spatial discrimination. The position preference was stronger in the 3-year-olds than in 5- or 10-year-olds. Similarly, the normal preschool group in Ellis et al. (1962) had a moderately strong position preference, but Stevenson and Swartz’s (1958) normal subjects, averaging 11.6 years of age, had no position preference. Levinson and Reese (1963) found little or no position preference in their nursery school group, and no position preference in their fifth-grade group. Steigman and Stevenson (1960) found that frustration increased perseverative behavior in normal preschool children, and that there were more perseverative responses to position than to stimuli. Two groups were given frustration or success experiences on 3 pretraining tasks, then were given a 3-stimulus discrimination problem, Two-thirds of the frustrated subjects showed perseverative behavior on the discrimination problem, and only about 22% of the success group showed such behavior. The subjects in the frustration group seemed to become highly anxious or to withdraw from the situation and ignore relevant cues, according to the investigators, and either reaction would increase the resistance to extinction of an incorrect response tendency. Using tasks like those of Steigman and Stevenson (1960), Kass and Stevenson (1961) found that the success experience produced less facilitation of performance in mental defectives than in normal subjects, and concluded that the success did not reduce the task anxiety of the mental defectives as much as that of normal subjects because of the long history of failure in learning tasks in the retarded subjects. In a review of the literature, Zigler (1962) has confirmed this assumption, and has also demonstrated a distracting effect of the experimenter on the behavior of institutionalized mental defectives. The distractibility of mentally retarded subjects has been noted by several investigators (Girardeau, 1959; House and Zeaman, 1961; Martin and Blum, 1961; Stevenson and Swartz, 1958; Zeaman, 1959), and it is generally believed that preschool children are more distractible than older children and adults, providing a possible explanation of the relation between position preference and mental and chronological age. B. Position Alternation. Spontaneous position alternation apparently does not occur in monkeys, or at most seldom occurs (see Behar, 1961a; Warren & Sinha, 1959). Position alternation in human subjects seems to appear later in ontogenetic development than position preference, but there is little evidence about the frequency of position alternation in young children. Using a 2-choice guessing problem in which the subject was to guess whether the next card in

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Discrimination Learning Set in Children a pack would be red or black, Kessen and Kessen (1961) found that older preschool children tended to change their response from trial to trial, whether correct or incorrect on the previous trial. Younger children tended to repeat following an incorrect response and to respond “black’ following a correct response. Whether these response preferences and alternations should be equated with positipn preferences and alternations is debatable. Schusterman (1963), however, reported that 5-year-old children tend to alternate positions in a 2-position probability learning situation, whereas 3-year-old children are more likely to show a position preference. The behavior of 10-year-old subjects was more consistent with successful performance. Levinson and Reese (1963) found little position alternation in preschool, fifth-grade, or college subjects. C. Stimulus Perseveration. Stimulus perseveration (stimulus preference) is related to the stage of learning-set formation in monkeys, decreasing as training progresses (Harlow, 1950). Stimulus perseveration may be more characteristic of mentally retarded children than of normal children. Kaufman and Peterson’s (1958) mentally retarded group had a higher percentage of stimulus perseveration errors than their normal group, but Ellis et al. (1962) found more stimulus perseveration in normal than in retarded subjects. The retarded subjects in the latter study had an average IQ of 16, whereas Kaufman and Peterson’s had IQ’s ranging between 50 and 75. Furthermore, Kaufman and Peterson used 3-trial problems, and Ellis et d.trained subjects to criterion on the first problem, then gave 6 trials on each of the remaining problems. Ellis et al. used “common use” objects; Kaufman and Peterson reported only that their stimuli differed in multiple characteristics. Steigman and Stevenson (1960), as noted above, found more perseverative responses to position than to stimuli in normal preschool children; and Levinson and Reese (1963) reported negligible stimulus perseveration in normal preschool children trained on 4-trial problems (they also found little stimulus perseveration in fifth-grade and college students). D. Stimulus Alternation. Stimulus alternation occurs more frequently than stimulus preference, and is more frequent in preschool children than in fifthgraders (Levinson & Reese, 1963). Stimulus alternation apparently has a low probability of occurrence in monkeys (but may be related to “response-shift” errors, discussed below). E. Differential Cue Error. The “differential cue error” is the frequency of errors on the first trial on which the correct stimulus object changes position (“differential cue trial”), relative to errors on trials on which the correct stimulus remains in the same position (“multiple cue trials”). The differential cue error persists longer than stimulus perseveration in monkeys, and is a function of the number of multiple cue trials preceding the first differential

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Hayne W.Reese cue trial (Harlow, 1959). Ellis et al. (1962) found little difference between normal preschool children and mentally retarded subjects with a mean IQ of 16, and the differential cue error was significantly greater than zero. Levinson and Reese (1963) also found fairly large differential cue errors, in normal preschool children. House and Zeaman (1958b) found no differential cue error in imbeciles who had previously been trained to a learning-set criterion of 20 correct responses on the first 25 trials of a new problem. F. Response-Shift. At least two kinds of “response-shift error” have been described (Harlow, 1959). According to one definition, response-shift is a greater frequency of errors following an initial correct response than following an initial error. This kind of response-shift is discussed in the section on firsttrial outcomes. A second definition describes response-shift as the number of errors following a series of correct responses when the initial response was correct, relative to the number of such errors when the initial response was incorrect. Still other definitions have been used, based on the assumption that the response-shift error results from “a strong tendency of the monkey to respond to both stimuli in the object-discrimination learning situation” (Harlow, 1959, p. 516). According to Harlow (1959) the response-shift error is the most persistent error factor in monkeys. Kaufman and Peterson (1958) found no significant difference between normal and mentally retarded subjects in “response-shift errors,” defined as trial-3 errors following a correct trial-2 response. Ellis et al. (1962) found only a negligible response-shift error in imbeciles, using Harlow’s second definition. House and Zeaman (1958b) found no response-shift error of this type in imbeciles who had already reached a learning-set criterion. Ellis (1958) reported that response-shift errors seemed to occur more frequently in a low-grade mentally retarded group than in a high-grade retarded group, but no quantitative observations were made. Furthermore, the responseshift error was defined as “a tendency for Ss to try out an alternative response even though the current one is being reinforced” (p. 8l), and it “did not appear to be contingent upon the nature of the initial response” (p. 81).

D. SUMMARYAND CONCLUSIONS It seems doubtfuI that the same kind of theory can account for learning-set formation in monkeys and children. A simple stimulus-response learning theory may account for the learningset data of infrahuman subjects, but not the data of human subjects. The effects of stimulus variables (kind of stimulus, size of stimulus) are less pronounced in children than in monkeys; children acquire the learning set much more rapidly than monkeys do; and the effect

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Discrimindtion Learning Set in Children of the amount of within-problem learning is much more complex in human subjects than in monkeys. The most striking difference between monkeys and children is in the effect of learning the first problem to criterion, which has little if any effect on the rate of learning-set formation in monkeys, but results in the immediate formation of a learning set in children. If children acquire the learning set in a single problem, some further improvement in performance across additional problems might occur as a result of further development of performance sets. On the other hand, the marked improvement from the first to the second problem might result from the development of performance sets on problem one, and the further improvement might reflect the development of the learning set. The former possibility seems more likely, as indicated in the conclusion of Section C, 2, because of the amount of facilitation that must be attributed to performance sets in the second alternative. In either case, however, the theory for infrahuman subjects would have to be modified to account for the data of human subjects. The shapes of the learning-set acquisition curves may be different in monkeys and children. The curve is either ogival or positively accelerated in monkeys, and it is either ogival or it exhibits two phases in children. There are differences in the hierarchies of error factors. One kind of response-shift error is frequent in both monkeys and children, but Harlow’s (1959) second kind is infrequent in children and is the most persistent error factor in monkeys. Position preference, position alternation, and stimulus alternation are more frequent in children than in monkeys, and stimulus perseveration is probably more frequent in monkeys than in children. The differential cue error is frequent in both. The ontogenetic trend over a wide age range is expected, although the deficiency of aged subjects relative to college undergraduates is not easily explained. The effects of intellectual variables may be due to attentional mechanisms (performance set), which might also account for the deficiency of the aged.

111. Recent Approaches The “error factor” analysis (Harlow, 1949; 1950; 1959) has recently been extended by Levine (1959), who developed a method of analyzing systematic patterns of responses, which he terms “hypotheses,” in all phases of learning, so that the system includes incorrect hypotheses occurring in the presolution period and the correct hypothesis, or problem solution. The “hypotheses” are paired, for example stimulus perseveration is paired with stimulus alternation, and the data analysis yields differential scores indicating which hypothesis in each pair is the stronger, and how much stronger it is than the other hypothesis.

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Hayne W . Reese (The terms are descriptive, not theoretical; the “stronger” hypothesis better describes the data.) Each hypothesis comprises two parts, which for convenience may be called “strategies.” One strategy consists of responses following a correct response on trial one (the “win” strategy), and the other of responses following an error on trial one (the “lose” strategy). Bowman (1961) has modified Levine’s method of analysis to permit the calculation of interval estimates of the strengths of the “win” and “lose” strategies separately. The hypotheses and strategies of Levine’s and Bowman’s systems are given in Table I, and the names of analogous ‘‘error factors” are also given. TABLE I

HYPOTHESES, STRATEGIES, HI: WSt, & LSh,

HI: WSh,

&

LSt,

Ha: WSt, & LSh,

Ha: WSh, & LSt, H,,: WSt, & LSt. He: WSh, & LSh, H?: WSt, & LSt, H8: WSh, & LSh,

AND

ERRORFACTORS (2-TRIAL MODEL)

Win-stay-object, Lose-Shift-Object. S chooses same object after win, shifts object after loss. Win-shift-object, Lose-stay-object. S shifts object after win, chooses same object after loss. Win-stay-position, Lose-shift-position. S stays on same position after win, shifts after Ioss. Win-shift-position, Lose-stay-position. S shifts position after win, stays on same position after loss. Stimulus Perseveration. S stays on same object on each trial. Stimulus Alternation. S shifts objects from trial to trial. Position Preference. S stays on same position on each trial. Position Alternation. S shifts position from trial to trial.

Note-Adapted from Levinson and Reese (1963).The first column gives Levine’s (1959) symbols; the second gives Bowman‘s (1961)symbols; and the third gives the names and descriptions. HI is the probIem solution; Hb through Ha describe response sequences that are independent of the trial-1 outcomes.

For heuristic purposes, the hypothesis and strategy models are used below to provide a p o ~ thoc explanation of the data of House et al. (1957). House et al. compared three learning conditions in mental defectives, using planometric stimuli. Each subject was given four problems of each kind. In Condition C one positive and one negative stimulus were used in each problem; in Condition V N one positive stimulus and five different negative stimuli were used in each problem; and in Condition VP one negative stimulus and five positive stimuli were used in each problem. On the first problem, VN performance was very similar to performance on Condition VP and inferior to performance on Condition C; and on the last problem, VN performance was as good as performance on Condition C, and superior to VP performance. Theoretically, the responses were initially controlled by simple approach and avoidance tendencies, but later came under control of a learning set. In early problems, the tendency to avoid the single negative stimulus in Condition C became stronger than the tendencies to avoid the several negative stimuli in

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Discrimination Learning Set in Children Condition V N (since each negative stimulus was presented only one-fifth as often as the single negative stimulus of Condition C). The net tendency to respond to the positive stimulus, then, was greater in Condition C than in Condition VN, even though the tendency to approach the positive stimulus was the same in each condition. Similarly, the tendency to approach the positive stimulus in Condition C (and V N ) was stronger than the tendencies to approach the several positive stimuli of Condition VP, although the tendencies to avoid the negative stimulus of Conditions C and VP were equal. Therefore, performance on the early problems was worse on Conditions VN and VP than on Condition C. The lack of a difference between Conditions VP and V N indicates that approach and avoidance tendencies were equally important. Forty trials were given on each of the twelve problems, using a correctional procedure, and a learning set may be assumed to have been acquired. O n the later problems in Conditions C and VN, then, subjects whose first response on a problem was correct repeated the response (win-stay-object), and made no errors (a few errors occurred, presumably because of distractions, strong stimulus preferences, etc.) . O n Condition VP, errors occurred because the variability in the positive stimulus made win-stay-object impossible on some trials. When the first response was an error, subjects shifted their response to the other stimulus (lose-shift-object) Because a correctional procedure was used, the error was followed by a response to the correct object and no further errors occurred on Conditions C and VN (because of the win-stay-object strategy). Further errors occurred on Condition VP, however, since on some trials the positive stimulus changed, making the win-stay-object strategy impossible. Levinson and Reese (1963) used both the Levine and the Bowman models to analyze the learning-set data of preschool and fifth-grade subjects. The Bowman analysis seemed to yield more easily interpreted results, and was also applied to the data of a sample of college students. The subjects at each age level were divided into “criterion-reference’’ subgroups (Hayes & Pereboom, 1959), which were homogeneous with respect to the number of problems required to attain a learning-set criterion. The subjects were given standard, 4-trial problems. The preschool subjects exhibited the lose-shift-object strategy (the lose strategy of the problem solution) earlier in training than win-stay-object (the correct win strategy). This trend reflects the occurrence of more correct responses following an initial error than following an initial correct response (see Section 11, C ) . The most frequent lose strategy in the fifth-grade sample was lose-shift-object, which was correct, but the most frequent win strategy in the presolution period was win-shift-object, which was incorrect. (In combination, these strategies constitute stimulus alternation,) There were, then, more errors following a correct response than following an error in the fifth-graders as well as in the preschool subjects.

.

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Hayne W . Reese The dominant win strategy in the presolution period was win-stay-position in most of the preschool criterion-reference subgroups. There were only weak position strategies in the fifth-grade criterion-reference subgroups, and only one subgroup of the college sample showed such behavior. In a subgroup of college students who did not meet a learning-set criterion in 30 problems, win-stayposition was the dominant win strategy by the end of training. The incorrect win strategies appeared to be eliminated in a fixed order at all 3 age levels. Levinson and Reese’s (1963) preschool subjects exhibited on some blocks of problems win and lose strategies that were inconsistent. For example, in one criterion-reference subgroup the dominant strategies over 20 problems were lose-shift-object and win-stay-position. The strategies of the older subjects usually constituted some hypothesis, such as stimulus alternation (win-shiftobject, lose-shift-object) . The younger subjects also exhibited more different strategies than the older subjects, and persisted longer in incorrect strategies.

IV. Theoretical Analysis and Conclusions Analyses of learning-set data in terms of “error factors” or the more recent “hypotheses” and “strategies” seem to be highly fruitful. However, these are response-defined terms, referring to systematic sequences of responses, as did Krechevsky’s (1932) term “hypothesis.” Naming the response sequences does not explain them, and no mechanism to account for the development and operation of strategies or hypotheses has been suggested, although several theorists have dealt with the problem (e.g., Harlow, 1950; 1959; Harlow & Hicks, 1957; Levine, 1959; Restle, 1958; 1960; 1962). Hypotheses and strategies in older children and adults are logically related, and can be analyzed as self-instructions or “sets” in Bugelski’s (1960) sense. That they are not always overtly verbalized, even when the subjects are questioned, does not raise a serious objection, since it has been demonstrated that even a simpler kind of verbal mediation may occur without “awareness” (Bugelski & Scharlock, 1952). In addition, Giddan and Eriksen (1959) found that a “positional response bias” (position preference) generalized to a transfer task without the subjects’ awareness of the occurrence of the bias on the transfer task, Hypotheses and strategies in older human subjects may be verbal mediators. Stevenson and Weir (1961) and Overall and Brown (1959), among others, have supported the conclusion that single stimulus-response units are not affected by reward and nonreward in older subjects; verbal hypotheses may be confirmed or disconfirmed, but only over a series of responses. It appears, then, that two learning-set theories are needed; to account for learning sets in infrahuman subjects, a theory might be based on traditional stimulus-response

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Discrimination Learning Set in Children learning theory; and to account for learning sets in older children and human adults, a theory of verbal learning and mediation is adequate. That the strategies of younger subjects may be unrelated suggests that they may be nonverbal. Levinson and Reese (1963) found that few of their preschool subjects verbalized the basis of solution when questioned after reaching criterion, and although this finding could indicate that the verbal mediation occurred without awareness, it may indicate a deficiency in mediation. Reese (1962) reviewed the literature related to verbal mediation in young children and found general support for the conclusion of several investigators (Kendler, Kendler, & Wells, 1960; Kuenne, 1946; Luria, 1957) that there is a deficiency in mediation in young children. The deficiency occurs at different age levels for different kinds of problem and possibly for different kinds of mediator (see Griffith, 1962; Reese, 1962), but if the differences between preschool children and older subjects in learning-set formation are interpreted as indicating a mediational deficiency in the younger subjects, the learning-set studies can be used in an analysis of the deficiency. Three alternative mechanisms are discussed below. (1) Younger subjects may be deficient in some attentional mechanism. Zeaman (1959) postulated that the difference between the performance of mentally retarded and normal children on a single discrimination problem results from a difference in “attention.” The difference between the performance curves is in the number of trials required for the curves to rise above the chance level. Once the mentally retarded subjects begin to perform at a level better than chance, their acquisition curve is parallel to the curve of normal subjects. The distractibility, or deficiency in attention, of mental retardates is well known; until their attention improves in an experiment, their performance remains at the chance level. House and Zeaman (1958a) found that normal preschool children and imbeciles, matched for mental age, were not significantly different on a pattern discrimination, but the subjects were given preliminary training that should have eliminated position preferences and helped to establish “attention.” Cantor (1962) briefly discussed a “set to discriminate,” used to account for the facilitating effects of learning an easy discrimination on the learning of a difficult discriminaton (see Barnett & Cantor, 1957; Spiker, 1959). House and Zeaman’s (1960) data might also be attributed to the development of a discrimination set; mental retardates who first learned an object discrimination learned a pattern discrimination faster than a control group that learned only the pattern discrimination, but the experimental group learned the pattern discrimination more slowly than the object discrimination. House and Zeaman (1962) confirmed this finding. The results can not be attributed to the development of a learning set, but may be produced by a discrimination set, which may involve orienting responses (see Spiker, 1959) .

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Hayne W . Reese Other investigators of discrimination learning, in normal as well as retarded subjects, have suggested similar mechanisms (e.g., Duncan, 1958; Girardeau, 1959; Kurtz, 1955). None of the mechanisms, however, can account for the two-phase curves that have been obtained. The mechanisms require that in homogeneous subgroups, the curves must remain at the chance level during the first phase, if the first phase reflects a deficiency in the operation of the mechanism. The first-phase curves of criterion-reference subgroups do not remain at the chance level, but increase significantly. In the first phase the subjects are not responding to irrelevant cues, which by definition are not systematically related to reward, because their performance improves. Furthermore, performance following an initial error improves before performance following an initial correct response. ( 2 ) Younger subjects may be more anxious than older subjects. Spiker (1959) found that training on an easy discrimination facilitated later performance on a difficult discrimination. He suggested two explanations, one in terms of the development of orienting responses in the experimental group, and the other in terms of the interfering effects of failure-produced frustration, which results in a lack of attention and the occurrence of competing responses, in the control group (trained only on the difficult task). Spiker (1956) had previously found evidence that the increased number of failures occurring when the stimuli are highly similar produces such effects; and the same effects have been observed by others. Stevenson and Pirojnikoff (1958) and Steigman and Stevenson (1960) described the behavior of children in a failure condition as “frustrated,” “restless,” “anxious,” “withdrawing,” and “demoralized.” If the early failures arouse frustration or anxiety, which may produce interfering responses (Brown & Farber, 1951; Sarason ct d.l960), the gradual improvement of performance in the first phase of the learning-set acquisition curve might reflect gradual adaptation of the emotional response, or extinction of the competing responses elicited by the emotion. The evidence shows that most of the first-phase improvement occurs on problems on which the initial response was an error, in line with the explanation; but from the beginning of training the frequency of correct responses after an initial error is greater than after an initial correct response, contrary to the trend that would be predicted. Since the emotion and presumably the responses it produced would be stronger after an error than after a correct response, there should be greater interference with performance after an error, at least early in training. ( 3 ) Younger subjects may use inappropriate mediators. There is some evidence that the deficiency in mediation results from the kinds of verbal labels used by young children. Two studies (Calvin & Clifford, 1956; Calvin et al., 1956) using first- and second-grade children as subjects found performance worse on a color discrimination problem than on problems requiring discriminations on other dimensions, such as form, brightness, and size. The children apparently labeled the stimuli differing in color as “colored cards,” rather than

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Discrintination Learning Set in Children as “blue” and “red” cards. The mediated generalization or acquired equivalence of cues resulting from using the same conceptual label for both stimuli would interfere with performance. In another study leading to a similar conclusion, normal preschool children and imbeciles were compared on discrimination and discrimination reversal problems (O’Connor & Hermelin, 1959). The imbeciles learned the reversal faster than the normal children except when the imbeciles were required to verbalize their choices on the initial discrimination. In the verbalization condition the imbeciles were inferior to the normal subjects. In Goss’s (1961) terms, a “one-stage” paradigm, involving responses to specific stimuli, accounts for the performance of the imbeciles; but a “twostage” paradigm is needed to explain the performance of the normal subjects, who respond by naming the dimensions, and then by naming the specific values along the dimensions. The imbeciles apparently do not spontaneously label the stimuli, and therefore after the extinction of the tendency to approach the previously positive stimulus, they need only learn to approach the previously negative stimulus. In the verbalization condition, however, the imbeciles must extinguish the response to the old positive stimulus aizd the response mediated by the label, then learn to approach the old negative stimulus. The tendency to approach the old positive stimulus is mediated by a verbal label in the normal child, and must be extinguished, but the new learning is facilitated by previous labeling of the relevant dimension. In the young child the labeling of the dimension may occur, but the labeling of the specific values on the dimension may occur only with prolonged training. This analysis can account for the slower learning-set formation in preschool children than in older children and adults, but it also predicts an age difference within the preschool age range. The younger preschool subjects are preverbal, at least for the kinds of mediators presumably required, and should therefore acquire the learning set more slowly than older preschool children. Only one investigation of age differences within the preschool range used the standard learning-set procedure (Levinson & Reese, 1963), and no reliable age difference was found (see Section 11, B) . I n conclusion, two broad generalizations seem justfied. First, the hypothesis and strategy models promise most fruitful results in the analysis of learningset data. Second, in addition to meeting the obvious need for further research on learning-set formation itself, studies using the learning-set paradigm may provide information about the phylogenetic and ontogenetic development of mediation and about the nature of mediational processes.

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Huyne W . Reese Barnett, C. D., & Cantor, G. N. Discrimination set in defectives. Amer. J. menf. Defic., 1957, 62, 334-337. Behar, I. Learned avoidance of nonreward. Psychol. Rep., 1961a,9, 43-52. Behar, I. Analysis of object-alternation learning in rhesus monkeys. J. comp. physio). Psychol., 196lb, 54, 539-542. Bensberg, G. J., Jr. Concept learning in mental defectives as a function of appropriate and inappropriate “attention sets.” J. edirc. Psychol., 1958,49, 137-143. Bowes, A. E., & Wischner, G. J. Mastery of early problems as a factor in learning set formation by retarded children. Paper read at Eastern Psychol. Ass., Atlantic City, New Jersey, April, 1959. Bowman, R. E. Discrimination learning set under intermittent and secondary reinforcement. Paper read at h e r . Psychol. Ass., New York, September, 1961. Brown, J. S., & Farber, I. E. Emotions conceptualized as intervening variables-with suggestions toward a theory of frustration. Psychol. Bull., 1951, 48, 465-495. Bugelski, B. R. A n introduction to the principles of psychology. New York: Holt, Rinehart, and Winston, 1960. Bugelski, B. R., & Scharlock, D. P. An experimental demonstration of unconscious mediated association. J. exp. Psychol., 1952,44, 334-338. Callantine, M. F., & Warren, J. M. Learning sets in human concept formation. Psychol. Rep., 1955, 1, 363-367. Calvin, A. D., Clancy, J. J., & Fuller, J. B. A further investigation of various stimulusobjects in discriminative learning by children. Amer. J. Psychol., 1956, 69, 647-649. Calvin, A. D., & Clifford, L. T. The relative efficacy of various types of stimulusobjects in discriminative learning by children. Amer. 1. Psychol., 1956, 69, 103-106. Cantor, G. N . The effects of three types of pretraining on discrimination learning in preschool children. J. exp. Psychol., 1951,49, 339-342. Cantor, G. N. Basic learning research and mental retardation. In E. P. Trapp & P. Himelstein (Eds.) Readings on the exceptional child. New York: Appleton-CenturyCrofts, 1962. Pp. 170-180. Cook, T. W. Cumulative transfer in the reproduction patterns on the Toronto Peg Board. Percept. mot. Skills, 1959,9, 375-385. deHaan, H. J., & Wischner, G. J. Three-dimensional objects vs. projected color photographs of objects as stimuli in learning-set formation by retarded children. J . comp. physiol. Psychol., 1963,56, 440-444. Duncan, C. P. Transfer after training with single versus multiple tasks. J. exp. Psychol., 1958, 55, 63-72. Duncan, C. P. Description of learning to learn in human subjects. Amer. J. Psychol., 1960, 73, 108-114. Ellis, N. R. Object-quality discrimination learning sets in mental defectives. J . comp. PhyJiol. Psychol., 1958,51, 79-81. Ellis, N. R., Girardeau, F. L., & Pryer, M. W. Analysis of learning sets in normal and severely defective humans. J. comp. physiol. PJychOl., 1962,55, 860-865. Giddan, N. S., & Eriksen, C. W. Generalization of response biases acquired with and without verbal awareness. J . Pers., 1959, 27, 104-115. Girardeau, F. L. The formation of discrimination learning sets in mongoloid and normal children. J. romp. physiol. Psychol., 1959,52, 566-570. Goss, A. E. Verbal mediating responses and concept formation. Psycho(. Rev., 1961, 68, 248-274. Greenberg, R., & Underwood, B. J. Retention as a function of stage of practice. J. exp. Psychol., 1950, 40, 452-457.

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Hayne W . Reese Lipsitt, L. P., Castaneda, A,, & Kemble, J. D. Effects of delayed reward pretraining on discrimination learning of children. Child Develprn., 1959, 30, 273-278. Luria, A. R. The role of language in the formation of temporary connections. In B. Simon (Ed.) Psychology in the Soviet Union. Stanford: Stanford Univer. Press. 1957. Pp. 115-129. Martin, W. E., & Blum, A. Intertest generalization and learning in mentally normal and subnormal children. J. comp. physiol. Psychol., 1961, 54, 28-32. Mason, W. A., Blazek, N. C., & Harlow, H. F. Learning capacities of the infant rhesus monkey. J. comp. physiol. Psychol., 1956, 49, 449-453. Meyer, D . R., & Miles, R. C. Intralist-interlist relations in verbal learning. J. exp. Psychol., 1953, 45, 109-115. Morrisett, L., Jr., & Hovland, C. I. A comparison of three varieties of training in human problem solving. J. exp. Psychol., 1959, 58, 52-55. Murphy, J. V., & Miller, R. E. Spatial contiguity of cue, reward, and response in discrimination learning by children. J. exp. Psychol., 1959, 58, 485-489. Norcross, K. J., & Spiker, C. C. The effects of type of stimulus pretraining on discrimination performance in preschool children. Child Develprn., 1957, 28, 79-84. OConnor, N., & Hermelin, B. Discrimination and reversal learning in imbeciles. J . abnorm. soc. Psychol., 1959, 59, 409-413. Overall, J. E., & Brown, W. L. A comparison of the decision-behavior of rats and of human subjects. Amer. J. Psychol., 1959, 72, 258-261. Plenderleith, M. Discrimination learning and discrimination reversal learning in normal and feebleminded children. J. genet. Psychol., 1956, 88, 107-112. Reese, H. W. Verbal mediation as a function of age level. Psychol. Bull., 1962, 59, 502-509.

Restle, F. Toward a quantitative description of learning set data. Psychol. Rev., 1958, 65, 77-9 1.

Restle, F. Note on the "hypothesis" theory of discrimination learning. Psychol. Rep., 1960, 7, 194. Restle, F. The selection of strategies in cue learning. Psychol. Rev., 1962, 69, 329-343. Riopelle, A. J. Transfer suppression and learning sets. J. comp. physiol. Psychol., 1953, 46, 108-114. Riopelle, A. J., Wunderlich, R. A., & Francisco, E. W. Discriniination of concentric-ring patterns by monkeys. J , romp. phyJiol. Psychol., 1958, 51, 622-626. Roberts, K. E. The ability of preschool children to solve problems in which a simple principle of relationship is kept constant. J. genet. Psychol., 1932, 40, 118-135. Roberts, K. E. Learning in preschool and orphanage children. Univer. la. Stud. Child Wejf.,1933, 7, No. 3. Sarason, S. B., Davidson, K. S., Lighthall, F. F., Waite, R. R., & Ruebush, B. K. Anxiety in elementary school children. New York: Wiley, 1960. Schuck, J. R., Polidora, V. J., McConnell, D. G . , & Meyer, D. R. Response location as a factor in primate discrimination. J. romp. physiol. Psychol., 1961, 54, 543545. Schusterman, R. J. The use of strategies in two-choice behavior of children and chimpanzees. J. comp. physiol. Psychol., 1963, 56, 96-100. Shepard, W. 0. Learning set in preschool children. J. romp. physiol. Psychol., 1957, 50, 15-17. Spiker, C. C. Effects of stimulus similarity on discrimination learning. J. exp. Psychol., 1956, 51, 393-395.

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Discrimination Learning Set in Children Spiker, C. C. Performance on a difficult discrimination following pretraining with distinctive stimul. Child Develpm., 1959, 30, 513-521. Spiker, C. C. Associative transfer in verbal paired-associate learning. Child. Develpm., 1960, 31, 73-87. Steigman, M. J., & Stevenson, H. W . The effect of pretraining reinforcement schedules on children’s learning. Child Develpm., 1960, 31, 53-58. Stevenson, H. W., & McBee, G. The learning of object and pattern discriminations by chilllren. J. romp. physiol. Psychol., 1958, 51, 752-754. Stevenson, H. W., & Pirojnikoff, L. A. Discrimination learning as a function of pretraining reinforcement schedules. J. exp. Psychol., 1958, 56, 41--44. Stevenson, H . W., & Swartz, J. D. Learning set in children as a function of intellectual level. J . romp. physiol. Pxychol., 1958, 51, 755-757. Stevenson, H. W., & Weir, M. W. Developmental changes in the effects of reinforcement and nonreinforcement of a single response. Child Develpm., 1961, 32, 1-5. Strong, P. N., Jr. Memory for object discriminations in the rhesus monkey. J. romp. phyxiol. Psychol., 1959, 52, 333-335. Thune, L. E. The effect of different types of preliminary activities on subsequent learning of paired-associate material. J. exp. Psychol., 1950, 40, 423-438. Tizard, J., & Loos, F. M. The learning of a spatial relations test by adult imbeciles. Amer. J. ment. Defir., 1954. 59, 85-90. Warren, J. M., & Sinha, M. M. Interactions between learning sets in monkeys. J. genet. Pxychol., 1959, 95, 19-25. Wischner, G. J., Braun, H . W., & Patton, R. A. Acquisition and long-term retention of an object-quality learning set by retarded children. J . romp, physiol. Psyrhol., 1962, 55, 518-523. Wischner, G. J., & O’Donnell, J. P. Concurrent learning-set formation in normal and retarded children. J. romp. physiol. Psychol., 1962, 55, 524-527. Zeaman, D. Discrimination learning in retardates. Train. Sch. Bull., 1959, 56, 62-67. Zeaman, D., & House, B. J. Approach and avoidance in the discrimination learning of retardates. Child. Develpm., 1962, 33, 355-372. Zigler, E. Rigidity in the feebleminded. In E. P. Trapp & P. Himelstein (Eds.) Readings on the exceptional child. New York: Appleton-Century-Crofts, 1962. Pp. 141-162.

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JEARNING

I N THE FIRST YEAR OF LIFE

Lewis P. Lipsittl BROWN UNIVERSITY

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FIRST THREE WEEKS AFTER BIRTH . . . . . CLASSICAL AVERSIVE CONDITIONING . . . CLASSICAL APPETITIONAL CONDITIONING . . OPERANT LEARNING . . . . . . . . . THE ADAPTATION-HABITUATION PHENOMENON FOURTH WEEK AND BEYOND . . . . . . CLASSICAL AVERSIVE CONDITIONING . . CLASSICAL APPETITIONAL CONDITIONING . . OPERANT LEARNING . . . . . . . . . AN ISSUE: OPERANT CONTROL VERSUS OPERANT

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USPHS grant for the study of learning and discrimination in human infants. I am greatly indebted to Harold Schlosberg, chairman of the Psychology Department, and Glidden L. Brooks, Director of the Institute for Health Sciences at Brown University, for their constant support and encouragement in this work over a five-yea period. Herbert Kaye, my graduate research assistant from 1960 to the present, has provided talent and enthusiasm for which I am most grateful. Portions of this paper were presented at the meetings of the American Psychological Association, Chicago, 1960, and the Society for Research in Child Development, Pennsylvania State University, 1961.

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I. Introduction The learning ability of the newborn and infant human has been of psychological interest and speculation for many years. In the first decade of this century, psychoanalytic theory began to emphasize the importance for later behavior of early parent-child relationships. Supplemented by Rank’s insistence that supreme psychological trauma is incurred at birth and immediately thereafter, Freud no doubt sparked some of the initial empirical concern. Around the same time, procedures were under development in Pavlov’s laboratory for the extensive study of infrahuman learning processes, and these procedures were soon to be adapted to the study of children. Shortly thereafter, Watson’s extreme position concerning the early conditioning process as a major determinant of human behavior became well known. Widely used infant scales, such as those of Gesell and Cattell, contain an item at the three-month age level which implies that learning is by this age an easily assessed phenomenon. The test item is that of “anticipating the bottle,” and acceptable performance involves the observation that the infant sucks or engages in other kinds of excitement responses in the presence of the visual stimulus alone. Such frequently observed infant responses are classically conditioned anticipatory responses to the previously neutral bottle stimulus, now associated with the ingestion of food in the presence of nourishment and/or sucking. Considering the extensive use to which these developmental tests have been put over the past several decades and thus the large number of child psychologists who have “tested for” this conditioning in babies, and considering the frequency of reference in the child development literature to “early experience” as an important contributor to later behavior, it is quite surprising that more interest has not been taken in determining the antecedent conditions for the occurrence of infant learning. A review of the available data concerning the learning process of the very young child reveals that comparatively few such studies are available, and few of these have systematically explored the various parameters known to affect learning in lower animals or the older person. Speculating on the basis for this scientific lacuna, one may observe that historically the major interest of the child developmentalist has been in charting “developmental milestones,” and in constructing the necessary psychometric procedures for documenting these. It may be observed that this descripthe concern, while undoubtedly necessary in any young science, tended to attenuate concern for the Processes by which these milestones are reached. Indeed, when the developmentalists explored beyond the descriptive level, it was usually to predict

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Learning in the First Year of Life one age-level performance from another, earlier performance. The prediction of later I.Q. from earlier developmental quotients is an example of such a time-bound search for laws. In the presence of such an orientation, the mechanisms by which changes in behavior occur over time tend to become (and were) neglected. Any complete theory of human behavior, and most particularly any theory of human development, should contain information about the learning processes of the young child. Indeed any developmental or personality theory which asserts that early experiences may have a lasting influence on the behavior of the organism must make assumptions about the nature of the infantile learning process. Developmental observation and testing has demonstrated well that the human child is an exceedingly complex creature from the standpoint of the changes in behavior occurring in the very first year of life. To assert without data, however, that the most important determinants of developmental change are hereditary, or maturational, or inevitable, seems gratuitous. Many of these changes could not possibly occur without a learning process, the precise mechanisms of which are still obscure. To assert that the processes are known through the study of adult and infrahuman learning misses the point. It is not the intent of this writer to argue against the proposition that the same principles of learning governing the behavior of other organisms are applicable also to the young child-indeed, his bias favors such a proposition-but the credibility of such adult and infrahuman analogies cannot carry the case indefinitely. Moreover, it is quite likely that while many of the facts and principles gleaned from the study of infrahuman organisms will be necessary principles, they may end up being not quite sufficient for a complete accounting of the behavioral phenomena of children. It would seem reasonable, therefore, for child researchers to get to the “basics” as quickly as possible in the organism of their primary interest. The intent of this paper is to review the various approaches to the study of learning processes within the first year of the child’s life and to ascertain the extent of our current knowledge concerning such processes. Methods developed in and preliminary data derived from the writer’s infant research program will be introduced where pertinent. Fair treatment of these objectives will necessitate an examination of some (more or less) critical issues with respect to infant learning. The logic and design of experimental controls necessitate clear definition of the phenomena under study. Moreover, the question of the learning capacity of the very young child can be resolved only by addressing the specific conditions under which the attempts are made. It will be necessary, therefore, to specify the criteria for learning, and to speculate on how learning might be distinguished from certain other processes which may also change behavior over time or under repetitive stimulation.

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11. Definition of Learning Learning phenomena are quite generally, among psychologists, defined by the acquisition of associative behavior through paired presentation of stimuli, or what McGeoch and Irion (1952) call practice. Thorndike (1898) made the “associative process” requirement explicit in the title of his important monograph which launched the study of learning in this country. A conditioned response is generally held to have been acquired when, after paired presentation of stimuli, it can be demonstrated that (1) a response is now elicited or intensified by a stimulus which did not previously elicit it, or did not elicit it as strongly or ( 2 ) a response in the repertory of the organism’s reactions may now be emitted upon the command of circumstances which did not previously control it. The former will be recognized as classical, and the latter as operant conditioning. In both of these instances, a new associative connection is either demonstrably established through the response-changes of the organism or is assumed to have occurred. I n the case of classical conditioning, such learning is demonstrated when a previously neutral or conditioning stimulus (the CS) , after temporal pairings with an already effective or unconditioned stimulus (the UCS), will now elicit the response (or some part of it) formerly typical of the reaction to the UCS. Thus when cIassicaI conditioning has occurred, it is assumed that an associative connection between the CS and UCS, or between the CS and the UCR (unconditioned response) has been established. The CS now acts upon the organism like the UCS and calls forth the response in anticipation to, or in the absence of, the UCS. In instrumental or operant conditioning, the associative connection may be between the response and its aftereffect, that aftereffect usually being referred to as the response-consequent or reinforcement. Thus, in operant conditioning, the proprioceptive and kinesthetic stimulation resulting from the execution of the response becomes associated with the reinforcement stimuli, and the response-frequency is either increased or decreased depending upon the nature (i.e., whether rewarding or punishing) of that reinforcement. While exception might be taken to any interpretation of which stimuli become associated with which other stimuli in the above processes, it seems that multiple stimuli, occurring contiguously, are required and changes in response must occur which r e d t from those paired presentations. Definitions, of course, are always arbitrary. In a discussion of infant learning especially, however, it would seem wise to keep the nomenclature clear even if controversial, for the definition of learning dictates the nature of the experimental controls necessary for the documentation of early learning. If one were to assume, for instance, that an acceptable definition of learning is “an increase

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Learning in the First Year of Life in reaction to a neutral stimulus following single presentations of an aversive stimulus” then it would have to be concluded that a control group involving UCS presentations only in the Wickens and Wickens (1940) study became “conditioned” as much as their experimental group which received paired CS and USC presentations. This was clearly not their intent in instituting that control.

111. The Prenatal Period Ray (1932) first reported a procedure for and an attempt at fetal conditioning in utero, utilizing tambours attached to the mother’s abdomen for recording of movement. Sontag and Wallace (1934) were apparently unable to obtain such conditioning. Spelt ( 1948), utilizing this procedure, studied the responses of 16 fetuses between seven and nine months gestational age. A loud clapper served as the UCS, and vibrotactile stimulation as the CS. Spelt reported that in some cases, as few as 15 paired stimulations resulted in movements to the tactile stimulus now presented alone. From 5 to 11 successive conditioned responses (CRs) were obtained, and one fetus apparently exhibited retention over a period of 18 days. Control subjects (5s) demonstrated that response to the vibrotactile stimulation does not develop as a function of time within the age limits of this study. Furthermore, the conditioning procedure was applied to nonpregnant Ss and produced nothing simulating the results obtained with pregnant Ss. As will be seen later with neonatal Ss, a control which may be essential would be that for pseudoconditioning or sensitization, the process whereby the UCS alone induces a predisposition to respond to other previously neutral stimuli, The absence of such controls makes difficult the interpretation of the apparent fetal conditioning results, and the difficulty is further compounded in the Spelt study by the fact that the mothers themselves may have become sensitized to the UCS. The nonpregnant controls may not provide the appropriate interpretive caution, inasmuch as the expanded uterine muscle in the pregnant Ss may produce greater abdominal reactivity in the presence of startle stimuli. The questions raised by this study notwithstanding, Spelt’s apparent success in establishing fetal conditioning, when considered in light of difficulties and persistent ambiguities encountered by researchers with full-term neonates, indicates that fetal conditioning should be explored more fully. Methods might be used in such further work to eliminate the mother’s perception of the loud-sound UCS. This could be accomplished by subjecting her to a loud continuous masking noise through earphones while the infant is subjected to the UCS. Also, control Ss who receive the CS and UCS in the same number and intensity as experimental Ss, but at nonconditioning intervals from one another, might be utilized profitably.

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IV. Infrahuman Infant Learning A number of infrahuman studies are available suggesting that conditioning can be obtained within the earliest days, even hours, of life. Only a representative few of these studies are presented here. It is thought desirable for the child psychologist to remain cognizant of these studies for two reasons: (1) their success engenders a certain optimism with respect to the eventual success with which conditioning attempts in the newborn human will meet, and (2) the animal studies tend to reflect a methodological sophistication not always present in studies of human infants. The success with which these animal studies have met may well reflect this greater technical sophistication more than it does true differential conditionability among species. In an interesting pair of conditioning studies with puppies, Fuller and his colleagues first reported that the capacity to develop classical conditioned responses to a noxious UCS was absent until approximately three weeks of age (Fuller et al., 1950), after which learning developed rapidly, suggesting a “critical period” in conditionability. However, a later study (Cornwell and Fuller, 1961) clearly indicated earlier conditionability when a tactile CS (air puff) was used in place of the previously employed visual and olfactory stimuli. In this study, the CS was presented for 10 sec overlapping in the last second with a shock to a forelimb. Ten trials per day were administered, beginning in the fourth day of life, and a pseudoconditioning control received the same stimulation as the experimental group in non-paired fashion. While the control group showed no acquisition whatever of response to the CS, the experimental group separated clearly from the control group between the eighth and tenth day, 50% of the experimental Ss attained criterion level (9 CRs in 10 trials) as early as 15 days of age, and 90% attained this level by 19 days of age after 150 paired stimulations. Recently Stanley et a]. (1963) have been able to demonstrate both appetitional and aversive conditioning in puppies less than 2 weeks old. Three groups of dogs received 7 days of training beginning about the third day of life. The CS was insertion of a manometer nipple into the S’s mouth. For the appetitional group the CS was paired with milk-feeding, while for the aversive group the CS was paired with quinine stimulation in the mouth. The control group was presented with CS accompanied only by a re-presentation of the manometer nipple. A significant increase in sucking behavior for the appetitional group, relative to the control, was found to occur over the sevenday training period. Relative to the same control group, a significant increase also took place in struggling behavior for the quinine-trained group. Sucking records were obtained during the CS presentation and were analyzed both in

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Learning in the First Year of Life terms of mean number of sucks per CS presentation and of percentage of trials during which measurable sucking occurred. The vigor of struggling by the S on each CS presentation was rated by the experimenter using a 0-to-3 point scale. Commenting on previous failures to condition the newborn puppy, the authors concluded that “. . . both appetitive and aversive conditioning can occur in the neonatal puppy and that previous failures to obtain conditioning were due to inadequate conditions for learning rather than to any general unconditionability of the neonatal puppy” (p. 21 1 ) . Mason and Harlow (1958) and Harlow (1959) have presented evidence for the early conditionability of the rhesus monkey. They conducted a classical conditioning experiment in which a five-subject experimental group received training involving a 3-sec 1000 cps tone as the CS and a 1-sec shock through a floor grid as the UCS. Tone preceded the shock by 2 sec. The infants were run in a stabilimeter cage which produced a record of conditioned movement on test trials involving presentation of the CS alone. In addition to the experimental group which received paired presentations of the CS and UCS, two control groups were run, one receiving presentations of the UCS alone, and one receiving the tone only and never the UCS. In all 3 groups 2 CS test trials were administered each day, and the procedure was carried out for a period of 30 days. The ages of the infants in each group were mixed: 10 of the total 13 Ss were 3 days old at the start of the experiment, one was 1 5 days old, and one was 7 days old, and these Ss were randomly distributed among the 3 groups. Mason and Harlow present a graph plotting percentage of CRs for successive blocks of 10 test trials (i.e., in 5-day blocks). Over the entire 30-day conditioning period, the tone-shock group gave 68% CRs as opposed to the shock group’s 31% and the tone group’s 41%. The differences over this entire 30-day period between the experimental group and each of the control groups independently are reported to be reliable. While there is an apparent difference between the experimental and the two control groups within the first block of 5 days (by which time the minimum average age of each group is 8 days), no statistical tests of the block-by-block differences are reported, and it is impossible to assess how early within the 30-day testing period the experimental Ss may have learned. Nonetheless Harlow (1959, p. 462) reports that the . . observational data indicate that these tone-shock conditioned responses were learned by three subjects on the second test day and that unequivocal conditioning took place in four of the five subjects.” A study of Golubeva (1939) abstracted by Anokhin indicates that it is possible to establish classical conditioned motor reactions in the hours-old guinea-pig, utilizing acoustic conditioning stimuli. Caldwell and Werboff (1962) have recently shown that newborn albino rats may be classically conditioned. They used a vibrotactile stimulus as CS ‘I.

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Lewis P. Lipsitt paired with electric shock to the forelimb 80 times. An adaptation phase was utilized to assure no response to the CS at the beginning of conditioning. This was accomplished by requiring 10 no-response trials to the CS. Four experimental groups were run, distinguished as to CS-UCS interval employed: 300, 600, 1200, and 2400 msec. These groups produced more conditioning behavior than did pseudoconditioning controls. The 300 msec group gave no reliable evidence of conditioning, while the other 3 groups did not differ statistically from each other. The 2400 msec group, however, seemed to perform at the highest level, suggesting that the optimal interstimulus interval for the young organism may be somewhat longer than is ordinarily found for the older organism. Interestingly, the highest level of performance of any group at asymptote was only about 32%, and rate of CR seemed to go down in the later trials, suggesting that in establishing classical conditioning in the young organism a somewhat greater experimental ingenuity, and certainly a parametric orientation, is required. This study might serve as a model to which attempts at conditioning the human newborn may aspire.

V. The First Three Weeks After Birth A. CLASSICAL AVERSIVE CONDITIONING Morgan and Morgan (1944) report data contrary to the proposition that aversive conditioning occurs within the first 3 weeks of life. They studied infants from 5 to 75 days, using as the CS the movement of the experimenter’s hand that held a syringe. The syringe was used to administer the UCS, a puff of air to the infant’s eye. It was held before the child‘s eyes, and after a 2-sec period, if the infant did not blink, the syringe was squeezed, producing the puff UCS. Under these conditions, the experimenters claimed inability to produce conditioning until about 45 days of age. Such a procedure, with its attendant lack of control of such conditions as CS-UCS interval, distraction possibilities, inconstancy of the air stream both as to pressure and locale of stimulation, variability in effectiveness of the CS, and so on, must be considered an attempt at conditioning under adverse experimental conditions. The 45-day lower limit should probably not be accepted seriously as a true lower age limit. Rendle-Short (1961) also tried eyeblink conditioning in infants, using an air puff as UCS and the sight of the apparatus as the CS. The data indicated that infants under 6-months of age would not condition, but the maximum number of trials administered was 20. Especially in view of the fact that after 6 months of age, conditioning occurred in progressively fewer trials, the most reasonable conclusion seems to be that under the experimental

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Learning in the First Year of Life conditions utilized, more than 20 trials are necessary to produce the effect in infants below 6 months of age. In 1936, Wenger reported success in obtaining classical aversive conditioning in newborns, although each of several experiments contained rather few Ss. His data indicate that aversive reactions may be generated to neutral stimuli in connection with the eyelid reflex, limb withdrawal, and respiration. In his eyelid-closure experiment, three experimental Ss, beginning at one day of age, were subjected to pairings of a tactile stimulus to the foot and a bright lamp which produced lid closure. The vibration CS preceded the light UCS by 3 sec. From observational and polygraphic recordings, Wenger concluded that aversive conditioning could take place by the fifth day, after 124 such pairings. No such increases in response to the CS took place in 6 Ss serving as controls for maturation or sensitization. In one of the attempts involving 5 experimental Ss, a 1084 cps tone served as CS, and an electrotactual stimulus applied to the toe as UCS, Wenger claimed that conditioning took place in 3 of these 5 Ss. Although their experiment lacked automatic control of stimulation and graphical recording of responses, Wickens and Wickens (1940) conducted one of the most interesting experiments with neonates. The CS was a buzzer sound and the UCS a strong shock to the foot, the latter eliciting an abrupt withdrawal of both legs. Any Ss which made such a response to the CS initially were eliminated from the experiment. The interstimulus interval was, as nearly as could be administered manually, .25 sec, and the CS continued with the UCS for .25 sec. Of 1 2 Ss administered the CS and UCS in paired fashion, nine showed a “conditioning” effect during an extinction period given after three days of 1 2 pairings each. In a control group which had received only an initial test with the CS and no further stimulations until the “extinction test,” only one of 1 2 Ss showed such reaction to the buzzer. Thus it could not be argued that the experimental group’s increased reaction to the CS in the extinction phase was due to a maturational change over the 3-day period. However, a second control group which had received only the shock for a comparable 36 trials produced reactions during the test period to the buzzer alone. Eleven of those 12 Ss responded to the CS without previous pairings of the CS and UCS. The investigators suggested that their findings necessitated an equivocal interpretation. Apparently mere administration of the UCS is sometimes sufhcient to produce a conditioned-like reaction, in the sense of predisposing the S to make responses to the previously neutral CS. Munn (1 954, 1955) has suggested that the pseudoconditioning phenomenon obtained by Wickens and Wickens may in fact be a true conditioning phenomenon, although it does not fit the usual classical conditioning paradigm. Munn’s reasoning is that (a) the shock-stimulated controls “learned” to respond to sudden stimulation, (b) the buzzer during test trials constituted

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Lewis P. Lipsitt sudden stimulation, and (c) reaction to the buzzer was a generalized response from the “training” situation. Munn’s implication is that a fear or startle state is produced by the shock and mediates an increased intensity of response to previously neutral stimuli. The fact that the CS-only control group, never administered the shock, did not produce such a threshold reduction to the buzzer offers support for such an hypothesis. It would appear, however, that Munn is suggesting a definition of conditioning which would merely involve reduction in response threshold to any stimulus when such reduction results from the presentation of an arousal or effective stimulus. This view would seem to hold that classical conditioning does not depend upon paired presentation of stimuli, a rather radical departure from the classical interpretation of classical conditioning. It is not disputed that there is such a phenomenon as Munn describes; indeed the data agree that there is. The question is whether this is classical conditioning (an associative process), on the one hand, or the result of a change in perceptual or motivational state of the organism, on the other. Traditionally, experimenters have used the UCS-only type of control for the very purpose of ruling out a change in reaction due to such nonconditioning circumstances induced by the experimental treatments. Moreover, there can be no argument with a definition of learning that would encompass this threshold reduction phenomenon in the absence of paired presentation. It is nonetheless necessary to keep distinct the operations which produce that effect (from no pairings) and those which produce classical conditioning effects (from CS-UCS pairings). Moving to other studies of early aversive conditioning, Polikanina (1961) has claimed to obtain conditioned autonomic and motor responses in the second week of life of infants born as much as 4 weeks prematurely. If such is the case, this may suggest that except for certain experiential requirements, the neonate is physiologically “ready” to be conditioned at birth. Polikanina used a 500 cps tone as a CS and ammonia vapor as the UCS. Six or seven trials per day were administered under a CS-UCS interval condition which was lengthened as conditioning proceeded, from 3 to 5 sec in early trials to 10 to 15 sec. The responses recorded were respiration and pulse rate in these infants who were at birth under 2300 gm, i.e., below that weight usually accepted as indicative of normal-term birth. Prematurely-born infants provide a unique opportunity in the modern obstetrical service to follow infants beyond the usual lying-in age limits of four days. Our information about early learning processes could be enhanced considerably by the exploitation of this population. I n connection with the Polikanina study, Lipsitt and Kaye have attempted without success to condition normal-term newborns in the third and fourth days of life, using a 10-sec 500 cps tone as CS and acetic acid vapor as UCS. An experimental group of 10 Ss received the CS and UCS in 20 paired presentations, with a 7.5-sec CS-UCS interval. A 10-Scontrol group received the same stimulations separated by a temporal interval of 20 sec or more. Under no conditions

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Learning in the First Year of Life of response observation during the 7.5-sec anticipatory interval did a conditioning phenomenon become apparent. However, Polikanina does not claim that such conditioning is possible until the second week of life even in the normal-term baby. It should be mentioned that in 1952 Kasatkin asserted that he was able to achieve conditioning in normal-term infants from 9 to 14 days of age where

Fig. 1 , Neonate laboratory, showing stabilimeter bed, polygraph, timers, loadspeaker, pbysiological stimulator, and controls.

the unconditioned reaction was a palpebral response and the CS an auditory stimulus. In the author’s laboratory, there has arisen an interest in the development of techniques for the demonstration and study of neonatal learning. The attempts thus far to classically condition aversive reactions in the newborn have produced results in this laboratory which are at best tentative. Modelled after an apparatus by Crowell et. al. (1960), equipment was devised (Lipsitt and DeLucia, 1960) for the controlled presentation of stimuli and polygraphic recording of various responses. Figures 1 and 2 show the

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Lewis P. Lipsitt basic apparatus in the neonate laboratory. The baby lies in a stabilimeter unit from which continuous recordings of body movement are made. This stabilimeter bed is effectively a suspended lever arrangement, one end of which contains a light-sensitive resistor near a small lamp in a light-proof box. AS

Pig. 2. Neonate in stabilimeter, electrodes attached, boot attached for recording legwithdrawal movements. Monitor light signals when UCS is applied.

the infant moves, the stabilimeter bounces lengthwise, and the resistor moves accordingly away from and toward the light source. Changes in resistance thus produced are transmitted to a polygraph pen (a Brush Recorder shown in the picture, now replaced by a Grass Model 5 four-channel polygraph) which reflects presence or absence (and roughly amount) of movement. A similar unit to which the baby’s foot is attached by means of an infant boot, records specific leg-withdrawal activity. The boot is attached to a rod containing a universal joint which permits movement of the leg in all planes. The opposite end of this rod contains a light-sensitive resistor in the same arrangement as for the stabilimeter. An audio-oscillator and loudspeaker are used to produce tonal stimuli, and a Grass Physiological Stimulator (Model S-4, with stimulus

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Learning in the First Year of Life isolation unit) enables stimulation of the toe with mild electric shock (10 cps current with monophasic pulse duration of 2 msec) of sufficient voltage to produce a withdrawal response. The intensity of the shock stimulation serving as the UCS is determined for each S using a standard psychophysical procedure (Lipsitt and Levy, 1959), such that the effective intensity can be made nearly constant from one infant to another and can be adjusted for the same infant from time to time to compensate for adaptation effects. The administration of the CS and UCS is controlled by a series of 3 Hunter timers which activate the CS tone, control the interstimulus interval, activate the UCS, and terminate the trial. Pen markers on the polygraph indicate on the recording paper the beginning and duration of both CS and UCS presentations. In a master’s study utilizing this experimental arrangement, Marum (1963) administered paired CS-UCS stimulation to one group of 10 infants, under a 500 msec interstimulus interval. The CS was of 2500 msec duration, and the UCS, 2000 msec. Training was begun on the first day of life. The Ss were administered 25 trials per day for 4 consecutive days, always at the same time of day. Every fifth trial of these 25 was a test in which the CS alone was presented, presence or absence of response (stabilimeter and leg-withdrawal) being noted. Two observers achieved 92% agreement in reading the records as to whether the response had occurred or not on test trials. In order to qualify as a response on a test trial, the S had to make more movement during the 3-sec interval following onset of the CS than during the 3-sec interval immediately preceding. A control group of 10 infants was run in exactly the same manner as the experimental group, except that the CS and UCS were presented under a 7500 msec temporal lag between offset of the CS and onset of the UCS. Presumably this latter condition should not result in conditioning but should serve as a control both for maturational effects over the 4-day period and for possible pseudoconditioning effects. The comparison of the experimental and control groups on test trials over the 4-day period is seen in Fig. 3. The experimental group tended to make more responses throughout the 4-day period than did the control group and responded with increasing frequency on successive days. The controls responded with increasing frequency at first and then declined, with the differences between the two groups seeming to increase. Statistically the difference between groups over the entire 4-day period was reliable at the .05 level. However, the interaction between groups and days, an effect which would demonstrate increasing divergence of the two groups with increased differential training and would thus provide the most convincing evidence for learning, was not significant. A second study by Marum was carried out involving similar stimulating

Lewis P. Lipsit! conditions but several procedural changes. An adaptation phase was instituted consisting of 10 trials with the CS alone prior to the paired-presentation trials, to allow decrement of any initial response to the CS to occur and to permit selection of Ss. Those Ss responding 6 or more times were eliminated

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from the study. Only 3- and 4-day-old babies were utilized. A total of 50 trials were administered, half in the morning and half in the afternoon. Rather than utilizing interspersed test trials, a 4-sec CS-UCS interstimulus interval was used, permitting assessment of response on each trial during the CS-UCS interval. In addition to an experimental and a control group like those in the previous experiment, a third group of 10 infants received the same procedure as the experimental group, with all stimulation terminating if at any time during the CS-UCS interval, the infant produced an anticipatory response. Unfortunately, no discernible changes in behavior suggestive of conditioning effects occurred in either experimental group. Another classical conditioning study of similar design was conducted by the writer and Kaye. Statistically reliable results were not obtained. Two 10-S groups were first subjected to a 10-trial presentation of CS alone. Following this, the experimental group received 50 trials (all in one session) of paired CS and UCS presentations. The CS lasted 10 sec, and UCS over-

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Learning in the First Year of Life lapped the CS in the last 2 sec. The control group received the same stimulus presentations, but with a 20-30 sec interval between the end of CS and the onset of UCS. The CS was a 500 cps tone, and the UCS a shock to the toe. All 5s received 10 trials of CS alone following the conditioning phase. A record of the type obtained is seen in Fig. 4, specially selected to demonstrate the classical conditioning phenomenon. The top pen records leg-withdrawal responses, the next pen is a CS marker, the next a stabilimeter recording, the fourth a breathing record obtained by attaching a pneumograph (Phipps and Bird) around the infant’s abdomen, and the next, a UCS marking.

Fig. 4 . Portion of polygraph record f r o m a conditioning subject. Top line represents leg-withdrawal, long dark marking represents CS, third line represents stabilimeter activity, fourth line is respiration, short dark line is UCS. Bottom line records skin resistance. Trial at left shows response occurring after UCS presentation. Trial at right shows response occurring to CS prior to UCS presentation.

The bottom pen records skin resistance which changes grossly with the state of the neonate but does not respond to specific stimulation as in the adult or older infant. Reading from left to right, the response at the left has occurred to the UCS but not to the CS. In the next trial, however, the response occurred to the CS prior to the onset of the UCS. The data obtained in this study are seen in Fig. 5. For the first 30 trials after the adaptation phase, the two groups responded with about equal frequency during the anticipation interval, 8 sec following onset of the CS. After this, the experimental group continued to rise, while the control group

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Lewis P. Lipsitt diminished in response to the CS. The effect, however, was not a reliable one, and the experimental group at its maximum point was responding on less than 30% of its opportunities. While it cannot be argued that all possible techniques for the establishment of classical aversive conditioning in the neonate human have been

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attempted, it must certainly be concluded that such conditioning is at best difficult to obtain.

B. CLASSICAL APPETITIONAL CONDITIONING Irwin (1930), in a meticulous study of the amount and nature of human neonatal activity, reported that infants adjust over a period of just a few days to the feeding schedule on which they are placed. As the usual feeding time approaches, the infants' motor activity increases sharply. The movement cycle becomes increasingly pronounced within the first 10 days. While Irwin's study was not of the learning process per se, he states with some reserve. ", . W e are not at all sure that infants of ten days cannot be conditioned . . . It has been observed both in the nursery and occasionally in the

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Learning in the First Year of Life experimental cabinet that hunger activities and crying which occur at what would be the scheduled feeding period at night drop out.” Although the cyclical nature of the infant’s movement could be accounted for on a physiological basis (i.e., as discomfort induced by hunger), it would be difficult on such a basis to handle the absence of one of its phases that Irwin reports to occur. Dorothy Marquis (1941), in a study of this adjustive process to the feeding schedule, reports that adaptation to a feeding schedule occurs during the first few days of life, and that this is a learning phenomenon. A group of infants shifted from a 3- to a 4-hour feeding schedule (i.e., a regular 3-hour feeding was omitted) on the ninth day showed significant increase in bodily activity during that last hour before feeding time, relative to a group maintained on a 4-hour schedule throughout. Unfortunately for the learning argument, such an effect might occur due to increased hunger during that fourth hour following the omitted feeding, assuming that infants on a 3-hr schedule do not consume as much at each feeding as those on a 4-hr interval. However, the increase in activity in this feeding-omitted 3-hr group was so striking that the hypothesis that the infant has been frustrated by the absence of the “expected” food is nonetheless an interesting one. I n a 1931 study, Marquis administered conditioning procedures to 10 bottle-fed infants beginning in the first day of life and extending to the tenth. A 5-sec buzzer preceded insertion of the bottle in the baby’s mouth and continued for 5 sec. This stimulus was administered whenever the bottle was reintroduced into the child’s mouth throughout the feeding period. Within 5 days, 8 of 10 infants exhibited sucking and mouth-opening responses to the buzzer, as well as diminution of crying and body-movement. Four control Ss, administered the buzzer uncorrelated with feeding, failed to show such conditioned-like reactions. Although no statistics are reported, Marquis concluded that significant changes of reaction to the buzzer occurred in 7 of the experimental Ss. Graphically this appears to have been about 125 pairings of CS and the bottle. Although Wenger (1936) has criticized this study as lacking adequate controls and utilizing a subjective response-assessment procedure, the study seems to be among the more successful of neonatal conditioning attempts. Wenger himself was unable to obtain such appetitional conditioning in two newborns. Russian investigators have been concerned with appetitional conditioning phenomena within the first weeks of life for some time (Razran, 1933). Most of this work has not been generally available in English translation and much that is available is often incomplete with respect to experimental procedures, the use of controls, and the extent of parametric investigation. The Russian investigations of infant conditioning seem inspired by the Pavlovian interest in the “nature of the nervous system.” Thus, in 1913, before data were avail-

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Lewis P. Lipsitt able to make one more optimistic about the learning capacity of the young infant, Krasnogorsky (Elkonin, 1957) said:

“In the normal newborn infant, the cortical innervations are developed to such an insignificant extent that conditioned connections cannot yet be found. In the second half of the first year, the formation of conditioned reflexes . . . is possible, but takes place more slowly than at a later age.” These investigators have tended to revise their estimation of the potentiality of the young human brain with their increasing success in applying the conditioning technique, but there is often present an inference concerning the immature structure of the brain based upon the behavioral failure of the conditioning phenomenon. To assume that the brain is incapable of conditioning on the basis of negative instances, however, is probably unwarranted, for the alternative hypothesis that techniques have simply not been refined sufficiently is equally tenable and indeed is supported by the history of infant conditioning attempts. It may be noted that Elkonin (1957) writes that Kasatkin has now obtained conditioned reactions in premature infants before the expected date of birth. While he assumes that this is evidence that premature infants undergo more rapid and earlier cortical development than normal-term babies, other hypotheses are possible, including some concerning the efficacy of stimulus differentiation pretraining. The premature infant is likely to have had more auditory, visual, and other stimulation prior to his expected birth date than his normal-term control. Denisova and Figurin (1929) studied infants as young as 10 days old. They reported failure to obtain conditioned reactions in nonexperimental or naturalistic situations before the third week of life, when infants would display anticipatory sucking responses when placed in accustomed feeding places or positions. A cautionary note should be added concerning such conditions of observation. I n the early days of life, a wide variety of stimuli have the capacity, apparently on a nonconditioned basis, to elicit the sucking response. Movement of a hungry infant from one position to another, particularly if such movement happens to entail tactile stimulation to the cheeks and lips (Prechtl, 1958; Blauvelt, 1962) or pressure on the arms (Babkin, 1958) could possibly lead to spurious observation of a conditioned-like phenomenon. I n his comprehensive review of Russian infant-conditioning studies, Kasatkin (1957) reports that Krachkayovska has been able to obtain a conditioned leucocytosis phenomenon in the eighth or ninth day of life, evidenced by an increased leucocyte count at nornial time of feeding when the feeding schedule is violated so as to permit an unreinforced test period. This scheduleinterrupting procedure is similar to that used by Marquis (1941) and may result in a temporal conditioning phenomenon. Kasatkin also reports that

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Lerlrning in the First Year of Life Bekterev and Schelovanov have obtained conditioned searching and sucking movements when placed in the usual feeding position, and that Nemanova produced a vestibular conditioned reaction in infants 12-16 days of age, based on both food and protective reinforcement. It is also reported that Golubeva obtained conditioned sucking reactions in premature infants in the third to tenth day of life, using a touch to the cheek as the CS. Brackbill (1962) has reported an experimental finding by N. S. Mirzoiants of classically conditioned responses associated with the ingestion of food within the first 3 weeks of life. Mirzoiants used a color as CS in association with the presentation of a milk bottle. The infants were administered 12-14 trials each day, with the CS preceding the UCS by 3 sec, beginning at 10-15 days of age. Brackbill says that the conditioned response appears in about 10 days from the start of the training. In the writer’s laboratory, a procedure has been adapted from one reported by Grunzke (1961) for eliciting and recording sucking responses. Ultimately the device or one similar to it may be used for direct feeding as well as response-recording but it has not been used that way in this laboratory as yet.* A mouthpiece shaped like a nipple and containing a small lever attached to a microswitch is covered with an ordinary bottle-nipple. As the baby sucks, the lever is depressed and released, producing on-and-off blips on the polygraph record, from which can then be read the frequency of sucks within given time units, the duration of each suck, and the inter-response interval. A study by Levin and Kaye (1963) demonstrated the usefulness of the device in following infants’ sucking activity to a non-nutritive oral stimulus (the nipple) placed in the infant’s mouth for 3-min periods. The data indicated that the newborn’s sucking rate remains quite constant over periods as long as one hour, even in the absence of nutritive reinforcement, and that a fair indication of an infant’s long-term sucking rate is reflected in his first minute of sucking. Some infants sucked with low and some with high frequency, but they remained similarly ordered over an hour-long period. Furthermore, amount of sucking to the non-nutritive stimulus was related to hunger, with sucking activity going up with increased time since last feeding. Utilizing this device for the administration of UCS, Lipsitt and Kaye (1963) paired a low-frequency loud tone (23 cps, 90 db) with the insertion of the nipple in the baby’s mouth. An experimental and a control group, each of 10 Ss in the third or fourth day of life, were utilized. All Ss were tested on one occasion only, this occasion being between 8 and 9:15 a.m., prior to the morning feeding. Thus all Ss had gone at least three hours since last feeding. For all Ss, the CS was of 15 sec duration. For the experimental group, the nipple was inserted into the infant’s mouth approximately We are indebted to Paul Weisberg for suggesting this device.

Lewis P . Lipsitt 1 sec after the onset of the tone CS and continued to the end of the CS. For the control group, the CS and nipple were not administered contiguously; the nipple was inserted in the baby's mouth for a 15-sec period approximately 30 sec following offset of the CS. This procedure should control for possible increases in responsiveness to the tone due to sensitization. All Ss first received five basal trials of CS alone, during which the presence and frequency of sucks to each of the 15-sec tones was counted and recorded independently by two observers. Both groups then received 25 trials of training. Every fifth trial was a CS-alone presentation, during which presence and number of sucking responses was again recorded. CS and UCS

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were paired on the 20 conditioning trials for the experimental group, and were administered under the extended time-interval for the control group. Following this training period, all Ss received a series of at least 10 extinction trials to a maximum of 30 trials. Extinction was discontinued for any S after 10 trials when no responses occurred for 3 successive trials. Observer agreement was high, for both the presence-of-sucking measure and frequency of sucking movements, The results of the experiment are essentially synonymous when each observer's recordings are considered independently. The data to be reported, however, are based upon the combined observations and are presented in Fig. 6. The per cent measure reflects the proportion of trials on which sucking was observed to occur during the CS-alone trials for the separate groups. It may be observed that percentage of responses increases monotonically for

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Learning in the First Year of Life the experimental group from beginning to end of the session, while responsiveness increases initially for the control group and levels off. For the measure involving actual numbers of sucks observed on each CS-alone presentation, the experimental group rises steadily from beginning to end, while the control group first increases (sensitizes?), then falls off. Statistical analyses of both of these measures indicate a highly reliable ( p < . O o l ) interaction between groups and trials, and further simple tests corroborate that the differences between the two groups are significant during the extinction phase following the differential training period. A significance test involving differential numbers of trials to extinction for the two groups was reliable at less than the .05 level, with the experimental group maintaining response during this period longer than the control. It is interesting to note that differential effects of training were not evidenced during the training test trials, but did become manifest during the extinction period. This fact, as well as the increase in sucking responses during that period for the control group, suggests that a sensitization phenomenon occurred similar to that found by Wickens and Wickens (1940) and others, but that such sensitization effects extinguishes more rapidly than do the effects of classical conditioning training. In any event, the data indicate strongly that a classical appetitional conditioning phenomenon can be observed within the first few days of human life. It should be noted also that while 20 paired presentations of CS and UCS constitute a relatively small number of trials, the frequency of sucking during presentation of the UCS is such as to produce many “pairings” within each trial of the CS and UCS. The sucking response is a remarkably efficient one from the standpoint of administering large numbers of paired presentations in a relatively short period of time.

C. OPERANTLEARNING The writer knows of no systematic operant studies during the early infancy period of the human. With Dr. Frances Clayton, he conducted such an experiment, more worthy of notice for its singularity than for its success. The newborns were run in tandem, each lying on a mattress with a plastic kick-panel at his feet. Each panel, when kicked, triggered its own microswitch, enabling recording of numbers of kicks for each infant separately on cumulative counters. A pair of electrodes attached to each infant’s leg enabled simultaneous delivery of a mild shock to both infants. After a basal period during which the operant kicking level of each infant had been ascertained, kicking of the panel by Baby A delivered a 2-sec shock (or less, if Baby A withdrew his leg) to both Baby A and Baby B. Thus, Baby A received shock specifically for kicking his panel, while Baby B received the

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Lewis P. Lipsitt same shock on a noncontingent basis. The intent was to determine whether Baby A would learn to refrain from kicking the panel and thereby diminish amount of aversive stimulation received, relative to Baby B who might not be expected to learn this response. The procedure proved fruitless under the conditions employed, perhaps because ( I ) the aversive stimulation tended to increase activity, working in an opposite direction to the change in behavior sought, and (2) Baby A was reinforced adventitiously for pressing the panel, since the shock lasted 2 sec at most for each press. Apparently researchers with newborns have not yet capitalized upon recent technological advances in the operant control of behavior. The programming of stimulation and the delivery of reinforcers on predetermined and appropriate schedules is no longer a methodological problem. The “harnessing” of specific responses for study is not an easy technological problem. The newborn performs many repetitive acts the frequency of which might be cumulatively recorded and influenced by appropriate reinforcers. I n the writer’s laboratory, for instance, one such response that seemed worthy to explore was a hand-waving response that often accompanies general body movement as well as stimulation about the face. A bottle was inserted into the baby’s mouth each time the response occurred and seemed to result in an increase in the behavior, followed by a decrease when reinforcement no longer followed the response. However, reliability of observation of the appropriate response was in this case not high without automatic response-recording equipment. Such responses as handwaving are ambiguous (how high does the arm have to be lifted, for how long, etc.) . Further developments in instrumentation, however, should enable a considerable advance in this area of operant control. Gunther ( 1961) has recently made some interesting observations concerning the operant behavior of newborns at the breast. I n addition to noting that the size and shape of the nipple and breast are of great importance in determining the ease with which the sucking response is elicited from the newborn, Gunthet commented on the extreme effect that a “smothering” stimulus may have at the time of feeding, and particularly during the earliest feeding experiences. Gunther stated that one such smothering experience may be sufficient to create an aversion. to the breast, or a marked decline in the frequency of searching and sucking. Gunther used the term “neurosis” in connection with the conflict that is set up between approaching the breast (an appetitional operant) and avoiding it because of its smothering effect (an aversive operant). Stimulation of the face areas, particularly the region of the mouth and nose, seems to hold much promise with further methodological developments, for in that region occur two of the most reliably assessed responses of the neonate: (1) rooting and sucking to stimulation on the lips and within the mouth (Piaget 1952), and ( 2 ) avoidance reactions to stimulation which obstructs or threatens to obstruct the breathing passages (Graham et al., 1956).

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Learning in the First Year of Life D. THEADAPTATION-HABITUATION PHENOMENON One of the most striking and easily demonstrated behavioral characteristics of human neonates is that they adapt to (cease responding to) stimuli which initially are effective elicitors of response. This diminution of behavioral response with successive administrations of constant stimuli is sometimes called habituation, and is considered by some to be a learning phenomenon. Diminution of response to repetitive presentations of unconditioned stimuli has been studied extensively in lower animals (Peckham and Peckham, 1887; Prosser and Hunter, 1936; Lehner, 1941; Hinde, 1954a), was reported to be observable in the human fetus in response to sound stimuli (Peiper, 1925; Forbes and Forbes, 1927), and was found by Jones (1930a) to be present in the galvanic skin responses of infants three months of age. Disher (1934) says of Kussmaul’s 1896 experiment, involving reactions of 20 newborn infants to olfactory stimuli, that infants became adapted to strong odorous substances quickly and then behaved as though there were no stimulus. Wertheimer (1961) reported that eye movements were reliably observed to occur in a neonate in response to a click stimulus but after 52 successive trials “. . the series was discontinued because the subject ‘lost interest,’ adapted, or satiated, in the sense that no further movements occurred in the response to the click. When the experiment was over, the subject was only 10 minutes old.” The adaptation phenomenon is clearly seen in responses to sufficiently intense sounds as to cause disturbance on a first trial, but gradually less on succeeding trials. Figure 7 is a polygraph record of a 1-day-old’s leg movement, body movement, and breathing on three successive 10-sec. administrations of a loud 1000 cps tone. The gradual diminution of the startle response is clearly visible in all measures. An experiment by Bronshtein ef al. (1958) reported adaptation in connection with the sucking response to auditory and olfactory stimuli. I n this case the adaptation phenomenon was a diminution of sucking interruption by these stimuli. A pacifier was placed in the neonate’s mouth and, as the infant sucked, an odor or tone was presented. The infant typically stopped sucking in response to the stimulus. This suppression of sucking decreased over 10 trials, and eventually the stimulus failed to produce interruption of sucking. These investigators have used the technique to assess the neonate’s capacity for discriminating among different frequencies and sources of tonal stimuli, by adapting responses first to one tone, then testing with another. When the tone is changed, it is concluded that discrimination has taken place if the suppressed or adapted response “recovers.” Brackbill ( 1962) reports use of the technique by Zonova for determination of color discrimination in the newborn.

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Lewis P. Lipsitt Other studies which have investigated adaptation and used the technique for the assessment of discrimination in the newborn are those of Bridget (1961), Bartoshuk (1962a, 1962b,), Engen et at. (1963), and Leventhal (1963). Bridget assessed startle-response intensity and cardiac acceleration to repetitive administrations of air-stream and tonal stimuli under varying stimulus durations and intervals. He found that lengthening the duration of the stimulus and shortening the interval between stimuli tended to decrease the number of repetitions necessary for habituation. Bridget also reported that 15 neonates of some 50 demonstrated discrimination when tone frequency was changed following habituation. Bartoshuk studied habituation and recovery of cardiac acceleration to sound stimuli, also under varying interstimulus intervals. In

Fig. 7. Record of neonatal adaptation to tone stimulus.

one experiment, it was demonstrated that neonates habituated to a stimulus pattern consisting of tone increasing monotonically from 100 to 1000 pulses per second over an 8-sec period, following which recovery of the habituated response occurred when the pattern was reversed (i.e., the tone began at 1000 and went to 100 pulses/sec over the 8-sec period). Bartoshuk favors interpreting such a selective habituation phenomenon as a kind of discrimination learning. The experiment by Engen et al. (1963) demonstrated that body movement and breathing responses adapt to the olfactory stimuli asafoetida and anise oil, and that following adaptation to one of these stimuli, recovery occurs with presentation of the alternate stimulus. Leventhal’s thesis substantiates the Bronshtein experiments with respect to localization but not Bronshtein’s or Bridget’s finding with respect to tonal discrimination. The adaptation or habituation phenomenon is not learning as defined in Section I1 of this paper. While this change in behavior as a function of

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Learning in the First Year of Life experience is an interesting, well-documented phenomenon and enables evaluation of the perceptual discriminative capacities of the young organism, there is no clear sense in which an associative process is involved. There is disagreement as to which kind of process is involved in habituation, and there seems to be a problem in differentiating habituation from other kinds of responsedecrement phenomena. Thorpe (1950) defines habituation as the waning of a response as a result of repeated stimulation which is not followed by any kind of reinforcement. He said that it is of a relatively enduring nature and is thus a different process from fatigue or sensory adaptation. Hinde (1954b) cites studies of Prechtl who, working with the gaping response of young Passerines, found that with repeated evocation the response waned specifically to that evoking stimulus. The response could still be evoked by other stimuli, and the effect seemed temporary, Hinde seems to favor calling this selective process adaptation and keeping it distinct from habituation and from Hull’s conditioned inhibition. H e nonetheless assumes that habituation is or can be some sort of learning not to respond, and he draws a parallel between the habituation phenomenon and the extinction of a conditioned reflex. Hinde admits, however, that there may be as many as four different mechanisms which underlie response decrement to repetitive stimulation. In view of the various definitional and methodological issues that presently exist with respect to response-decrement phenomena in the absence of reinforcement, and their relationship to more conventional learning processes, it is probably well to heed Rheingold and Stanley’s (1963) advice that “. . . any suggestion that neonatal habituation is similar to extinction, Pavlov’s internal inhibition, or Hull’s inhibition would be premature indeed.”

VI. The Fourth Week and Beyond Recent publications of Elkonin (1957) and Brackbill (1960; 1962) provide summaries of current investigations of infant learning in the Soviet Union, as well as indications of the nature of instrumentation and experimental design employed there. Therefore, no attempt will be made here to include all of this work. In general, it seems characterized by the use of ingenious experimental apparatus, particularly with respect to the documentation of sucking and head-turning responses, and the administration of complex stimuli.

A. CLASSICAL AVERSIVE CONDITIONING It has already been pointed out that Morgan and Morgan (1944) and Rendle-Short (1961) investigated classical eyelid conditioning in infants

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Lewis P. Lipsitt under 1 year of age. Using the puff-producing apparatus as the CS and an air-puff as the UCS, Morgan and Morgan report no such conditioning under 54 days of age, at least within 100 trials. Their opinion is that maturational factors rule out such conditioning prior to 54 days. By 65 days of age almost all infants studied became conditioned. Using a 20-trial limit and similar procedures, Rendle-Short obtained no conditioning prior to 6 months of age, after which conditioning required progressively fewer trials with increasing age. Aldrich (1928) used an aversive conditioning technique to assess whether a child in its fourth month of life, thought to be deaf, was actually deaf. H e sounded a small bell in association with the scratching of the infant’s sole with a pin, and found after 12-15 combinations that the bell was sufficient to elicit the response, Bregman (1934) was unable to modify the emotional responsiveness of 15 infants between the ages of 8 and 16 months. Sounds that were assumed to be either agreeable or disagreeable were paired with various objects, but appropriately negative and positive reactions to the objects did not appear. Wenger (1936) has pointed out that such an experiment would demand prior checks, which were not made, on the presumed disagreeableness of the sounds. Jones (1930b) reported the formation of a conditioned galvanic skin response in three 9-month-old children with 4-14 combinations of auditory, visual, or tactile stimuli with a shock, the various conditioning stimuli having been made previously indifferent by adaptation procedures. The CS preceded the shock by 10 sec and continued with it for another 10 sec. Controls for maturational changes in response to the CS were utilized. Watson and Rayner (1920) conducted a well-known study of aversive conditioning in an infant. The child, at 9 months of age, was shown a rat, a rabbit, and other furry animals which he had never seen before. It was noted that the only responses these stimuli elicited were positive, such as reaching out for the stimuli. A loud noise, which elicited a fear reaction, was used as the UCS and was sounded in association with presentation of the rat. On subsequent test trials, it was demonstrated that the rat had become a conditioned fear stimulus, now eliciting withdrawal and crying responses. The fear response generalized to other stimuli such as the rabbit, and subsequently the fear was successfully extinguished. Marinesco and Kreindler (1933) studied 25 infants ranging in age from 25 days to 3 years, using shock as the UCS applied to the leg, and a beating metronome as the CS. To record movements, a thread was attached to the S’s foot and to a marker on a smoked drum. Time-markers on the drum recorded the stimulus presentations. The metronome was sounded for a fairly long time (such as 50 sec) prior to the onset of the shock, which lasted 20 sec. Since tabular and graphical data are not presented for the infants below 2 6 months of age, it is difficult to determine what degree of success was

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Learning in the First Year of Life had with infants in the first year, but a statement was made to the effect that at least one infant of 7 months formed a conditioned reflex within only 7 trials. It is possible that this long-stimulus technique, particularly if the stimuli were presented in truly paired fashion rather than successively as was the case, might prove quite successful with the very young infant.

B. CLASSICAL APPETITIONAL CONDITIONING Mateer (1918) adapted a technique devised by Krasnogorski for classical conditioning of anticipatory mouthing and swallowing motions to food. The training consisted of pulling a bandage (CS) over the child’s eyes just prior to inserting food in his mouth (UCS). After training, anticipatory mouthing occurred to bandage placement. Although Mateer reported a decrease in number of trials required for conditioning with increasing age, the youngest children studied were 12 months of age. The common observation of anticipatory mouth-opening movements to the spoon in feeding babies under one year apparently has not been capitalized upon for extensive studies of conditioning. A much cited experiment of Kantrow (1937) utilized ingenious instrumentation and controls, and produced interesting results. She studied 16 infants aged 44-117 days. A control period, during which sucking responses were assessed, preceded each trial of paired CS and UCS presentations. At the end of the variable control period, a buzzer was sounded for 20 sec. Five seconds after the onset of the buzzer, a bottle of milk was administered. Sucking activity was recorded pneumatically by use of a chin harness linked with a polygraphic recording device. Kantrow reported that from 16 to 72 paired presentations were required for stable anticipatory sucking to occur, conditioned responses being defined in terms of a difference score based on rate of sucking responses during the control phase and rate during the 5-sec buzzer-alone phase. Training was carried out for as many as 9 experimental feedings, following which extinction was observed to occur to the buzzer presented alone. Kasatkin and Levikova (1935a) studied the development of conditioned responses to a tone paired with ingestion of milk. Three infants were studied, one beginning on the eleventh day of life, another at 25 days, and the third at 31 days. They were subjected to pairings of the tone and food for a period of 10 to 15 min per day. The number of paired presentations on each day was between 6 and 12. In the beginning, a 2-3 sec interstimulus interval was used, being extended to 10-16 sec as the training progressed. Response assessment involved the use of pneumatic devices for the recording of sucking and breathing responses. From 70 to 120 experimental sessions

Lewis P. Lipsitt were held with each infant over a 4-5 month period. All 3 infants were reported to have developed conditioned reactions between the ages of 35 and 44 days. This required 18 sessions and 131 pairings for the 11-day-old, 12 sessions and 74 pairings for the 25-day-old, and 6 sessions with 29 pairings for the 31-day-old. The authors concluded that the formation of conditioned reflexes in infants depends primarily on degree of maturity and less on number of paired presentations, implying that conditioned responses cannot be obtained prior to the age at which they developed in this experiment. While it does seem that under the conditions utilized here, the infants were remarkably homogeneously aged at the time of first conditioning, the relatively small amount of training that the infants received (10-15 min per day, and not every day) suggests that a more intensive regimen of training might have produced a more striking and earlier effect. These experimenters also studied stimulus differentiation following the establishment of conditioning, and reported that part of their subject-sample generalized from the CS to other auditory stimuli, while other Ss did not (i.e., differentiated the CS from other stimuli upon first presentation of the new stimulus). Extensive conditioned differentiation of tones seems to have occurred in all Ss by 2 to 3 months of age. Kasatkin and Levikova (1935b) reported appetitional conditioning and stimulus differentiation in another study of G infants aged 14-48 days at the start of training. Colored bulbs behind the head of the infant, lying in a crib, were used as CS, and the bottle of milk was used as UCS. The trials were conducted at regular feeding times. The CS-UCS interstimulus interval was approximately 7 sec followed by a period of paired stimulus presentations lasting from 10 to 40 sec. Kasatkin and Levikova say that the light stimuli alone produced a kind of orienting reaction at the outset but that this diminished after a while, permitting use of the light as a CS. For 5 of the infants, the CS was the color yellow, and for one the color red. Concerning the optimal state of the baby for conditioning, the experimenters make the interesting comment that, . a slight elementary excitement proved to be best for the formation of conditioned reflexes,” while the too quiet or too active Ss provided response-measurement problems. Kasatkin and Levikova report that all G Ss produced visual conditioned responses rather stably by 58-62 days of age, after varying numbers of paired presentations, depending upon the age at which the attempts were first made. The implication was made, as previously, that conditioning depended upon reaching a certain maturational age prior to which the phenomenon cannot be obtained. It is interesting to note that when the authors refer to age of development of the conditioned reflex they are speaking of pronounced intensification of sucking to the CS. Some qualifying statements suggest that conditioning may actually have occurred earlier than their reported dates, if one adopts a less stringent criterion for conditioning:

“. .

I74

Learning in the First Year of Life ". . . After that (indifferent) period we could note the formation of some new reactions as a response to the conditioned stimulus. The most interesting among them was the appearance of an inhibition of movement at the moment of lighting, that lasted until the lips touched the milk bottle. The gradual development of this inhibition is expressed in an almost complete cessation of whimpering and crying, in immobility of the body and the limbs . Besides that, a slight twitching of the lips and movement of the head toward the light were noted . . . This stage in the formation of the conditioned reflexes was evidently present in five out of the six children under experiment and represented the inhibition period . . . The development of inhibition is very gradual. Then inhibition became more pronounced in quality as well as in quantity and the child in response to every stimulus answered with a very expressive cessation of all movements . . . Soon after the inhibition period comes the last stage-when the conditioned reflex is being formed . ." (pp. 419-420).

..

.

Thus it is quite possible that other responses, such as breathing rate or body movement, might have been conditioned in their experiment at an earlier time than Kasatkin and Levikova report the conditioned sucking to have occurred. In this same study Kasatkin and Levikova produced differential conditioning. Following the stable establishment of the conditioned response, a new green color was introduced without pairing with the bottle. At first, a generalized response from the training color was obtained, but after a number of interspersed trials of the CS and the green color, gradual differentiation took place such that no response was elicited by green but the CR continued to be elicited by the CS. This conditioned discrimination phenomenon occurred between the ages of 88 and 116 days for all Ss. Recently more interest has been shown in the conditioning of so-called orienting reflexes in infants. Kasatkin et al. (1953) state that the newborn baby has a number of unconditioned protective orienting reflexes. Turning the eyes and head toward a source of light is one example. The child's turning his head when called by name at the age of 7-10 months is said to be a conditioned reaction based upon such an orientation reflex. These experimenters investigated conditioned orientation in 10 babies from 40 to 222 days, using a head harness that permits kymographic recording of left and right head-turning responses. The UCS was a flickering light, the CS a tone. Kasatkin et al. concluded that a conditioned orienting reflex to sound may be formed for the first time at about the age of 2.5 months, that by the fifth month the conditioning is very stable, and at ages 5-7 months such conditioning is very rapid.

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Lewis P. Lipsitt Further studies of the above-mentioned phenomenon have been carried out by Papousek (1959; 1960a; 1960b; 1961). An apparatus has been described for the measurement of general bodily movements and head turning responses. Papousek found sucking too complex a response to measure, because (1) it takes different forms in different Ss, the reaction consisting of both head and lip movements which jaw-movement and sucking devices do not record well, and (2) the nature of the unconditioned reaction tends to change considerably over the first 4 or 5 months of life. Papousek’s technique is an unusual one, combining aspects of both classical and operant methodology. A bell is sounded as CS for a period of 10 sec. If the child turns his head to the left, he receives the nipple immediately and the bell is turned off. If he does not turn to the left, the infant is stimulated at the end of the 10 sec period by a touch of the nipple at the left corner of the mouth. If this does not produce a left-turning response, the infant’s head is turned by the experimenter and milk is given in that position. A second stimulus, a buzzer, is introduced to study differentiation following conditioning, and the infant is fed at the right side in the presence of this stimulus. Papousek has used these procedures with babies from 1 to 20 weeks of age, and has reported obtaining stable conditioning at about 4 to 6 weeks of age. Differentiation of the two stimuli occurred at about 3 months, and reversal of this discriminative responding was produced at 4 months. Unlike the usual classical conditioning techniques, and more like operant procedures, the appropriate head-turning response is not elicited by a UCS at the outset of the training. After training, the bell and buzzer signal the locus of feeding on different occasions, as in some operant discrimination techniques.

C. OPERANT LEARNING A complete review of operant methodology will not be given here, but a few statements concerning the procedure seem worthwhile. Operant learning studies are of those processes by which the organism comes, over time and with successive reinforcements, to respond in some respect with increasing frequency. A certain response, called operant because it sets the occasion for reinforcement and occurs in the absence of specific identifiable eliciting stimuli is first observed to occur with a given frequency during a basal period prior to its deliberate manipulation. Subsequent manipulation of that response requires following its occurrence with reinforcement, either something appetitional (like food or certain kinds of visual stimulation) or something aversive (like shock or certain other kinds of visual stimulation). A responseconsequent of any type which influences strength or rate of response is called a reinforcer, whether it is an event which raises (as does food, typically)

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Learning in the First Year of Life or diminishes (as does shock) the likelihood of response. Operant learning is therefore an associative process in the sense that the rate of response is influenced by its association with the reinforcing circumstance. Specific discriminative stimuli may be introduced to the operant situation. For instance, the operant response might be followed by reinforcement in the presence of a red light, but that response will not result in reinforcement in the presence of a green light. A discriminated operant is said to be present when the probability of response in the presence of red is reliably greater than that during green, and when this preference was not present at the outset of training. So-called free-operant procedures generally involve unlimited times during which the S may emit any number of responses and receive any number of reinforcements dictated by the schedule of reinforcement under study. The controlled-operant procedure (Spiker, 1960), on the other hand, involves presentation of the discriminative stimuli for limited periods of time during which the response is followed by reinforcement. The traditional simultaneous and successive discrimination learning situations may be regarded as highly controlled operant situations in which discriminative stimuli are presented for a period limited by the time it takes the S to make one response. An example of a controlled-operant procedure of the simultaneous discriminative type is the study by Ling (1941), who presented two differentshaped objects on each trial to infants aged 6-15 months. One of the two objects contained a sweet substance and could be lifted to the mouth, while the other adhered to the tray and could not be raised. Children as young as 6 months were able to establish the discrimination and to respond solely to the reinforced shape. Valentine (1914) used a similar procedure in an earlier study involving infant discrimination of color, observing in addition that anticipatory mouth movements occurred when honey or jam was associated with certain of several colors presented successively. Brackbill (1958) utilized an operant procedure in a study of the smiling response of 4-month-old children. The reinforcement was a returning smile from the experimenter, who in addition spoke softly to the S, picked him up. and patted and jostled him for 30 sec. During the operant or basal period, the experimenter merely stood motionless over the baby for eight 5-min periods. Reinforcement was given during the conditioning period on an intermittent schedule for one group of four infants and regularly upon each response for another group. Finally, smiling responses during the extinction period were merely observed in the absence of reinforcement. Brackbill’s major finding was that the intermittent schedule of reinforcement produced greater responsiveness (slower extinction) during the final period, and that the infant’s smiling responses to the impassive face of the experimenter during that period diminished practically to zero.

177

Lewis P . Lipsitt A similar study with infants about three months of age was that of Rheingold et ul. (1959), who reinforced vocalizing responses with clicking noises and touches to the infant’s abdomen, and a returning smile. Each infant was studied over a 6-day period, the first 2 days being a period during which basal level of vocal behavior was observed, The next 2 days constituted a period of conditioning, and the final 2 days a period of extinction. Comparisons of rate of responding among the three periods of study indicated that vocalizations rose from the basal period to the conditioning period, and declined when the extinction condition was introduced. It would appear that an associative process was experimentally established, although the authors carefully point to the possibility that the increase in vocalizations during the conditioning period could have been due to response-eliciting properties of the reinforcing circumstance. In order to control for the reinforcing event serving as a possible eliciting stimulus for the vocal response to be operantly conditioned, Weisberg (1963) conducted an experiment involving thirty-three 3-month-old infants divided into 6 groups. In this experiment, noncontingent reinforcement controls were introduced. One group received contingent social reinforcement as in the Rheingold et ul. study, while its control received the same number of reinforcements during the conditioning phase but not in association with the vocalizing response. Another group received contingent nonsocial reinforcement for vocalizations, while a control group received noncontingent nonsocial reinforcement. The social reinforcement was a smile and a return vocalization from the experimenter, along with a bit of chin-rubbing. The nonsocial reinforcer was merely the sound of door chimes, Another control group simply involved no experimental manipulations and no experimenter in sight of the infant during the observation periods, and still another served as a control for the possible eliciting properties of the experimenter’s presence which was required in some of the groups. Although the nonsocial reinforcement produced no change in behavior during the conditioning phase, whether contingent or noncontingent, the contingent social reinforcement produced a reliable increase in vocalizing. The same reinforcer administered on a noncontingent basis produced no such increase. Furthermore, upon withdrawal of the social reinforcer during the extinction phase, rate of vocalizing tended to decrease. The excellent controls utilized clearly demonstrate that an associative effect was established and that the effect cannot be attributed to eliciting properties of the reinforcer. An operant discrimination apparatus was developed by Simmons and Lipsitt ( ~ 6 1 which ) ~ utilizes two 6-ia2 wooden panels as manipulanda, permitting

* The following portion of the author’s research program was supported successively by grants from the National Institute of Neurological Diseases and Blindness to the

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Learning in the First Year of Life the presentation of different colored lights as discriminative stimuli at windows in the middle of these panels. These panels are set in a box in front of which the baby is secured in a sitting position. Each panel is effectively a lever with a microswitch attachment so that pushing-responses activates a separate responsecounter for each. These counters are read every 30 sec. When the infant moves a panel, either the sound of chimes or no sound occurs, depending on the setting made by the experimenter (from an adjoining room) at the control console. The stimulus lights are also controlled from the console. Each experimental session lasted 8 min, divided into four 2-min phases. In Phase 1, the S+ or positive stimulus (e.g., red light and chimes) occurred in the left panel, while the S- or negative stimulus (e.g., blue light and no sound) occurred in the right. In Phase 2, S+ was switched to the right panel and S- to the left. I n Phase 3, both panels were S- (i.e-, both were blue, and responses produced no sound). In the final phase, the S+ was again associated with one panel and S- with the other. Data were presented indicating that infants 10-12 months of age could be put under stimulus control. They tended (1 ) to respond more to the reinforced (chimes-associated) color than to the nonreinforced color, regardless of the panel in which that color appeared, ( 2 ) to diminish responding when neither panel was reinforced, and ( 3 ) to resume differential responding when the stimuli were again different. The procedure had technical problems, one being that in extinction some Ss reacted with intensification of response and an increase in response-frequency (as if frustrated) rather than with diminution of response. More importantly, no traditional test for learning occurred in the procedure. The possibility existed that, even though differential responding occurred to the two panels according to the locus of reinforcement, the differential color-stimuli in the windows may have played little or no role in the process. Simmons’ dissertation study (1962) altered the procedure to include a basal period, during which initial differential responsiveness to the two colors could be assessed. An extinction period was utilized with both discriminative stimuli present to determine whether the proportions of response to the positive color increased as a result of training conditions. The basal period lasted 1 min, the conditioning period 4 min and extinction 2 min. Forty 12-month-old Ss were utilized, 20 of whom received red as S+ and 20 blue in a red-blue simultaneous discrimination task. The mean cumulative response data for the

Institute for Health Sciences at Brown (BP-2336, CS; NB-02356-06) and to the author from the National Institute of Mental Health (NB-04268). The Ss were members of the Collaborative Child Development Study. I wish to thank Gerald Solomons and Fouad Yazbak, Pediatric Directors of that study, and Raymond Holden of the Developmental Testing Unit for their cooperation in providing facilities. Sally Ann Serunian served as an assistant in much of this work.

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Lewis P . Lipsitt two groups are represented in Fig. 8. Utilizing these cumulative frequency data, as well as discrimination ratio transformations, it was demonstrated that (1) differential responding to the positive and negative panels increased from the beginning to the end of the conditioning period, ( 2 ) response to both the positive and negative color-stimuli decreased from conditioning to the end of the extinction period, and ( 3 ) preference for the reinforced color increased from the basal period to the extinction period as a result of the discrimination training.

/-

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Pig. 8. ReJults from Simmons experiment, Jhoiuing cumulntive respome to S+ and for i w o groups.

The above procedure has been modified recently to circumvent problems created by the tendency of some infants to strike the two panels simultaneously. Such behavior in the previous study may have interfered with the development of discriminative behavior, for under such conditions the infant receives reinforcement nondifferentially for response to the two colors. The procedure developed was a 3-panel apparatus, seen in Fig. 9. It has the additional

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Learning in the First Year of Life

Pig. 9. Three-panel apparatus for study of operand discrimination in young children. Colors appear in windows of panels. Depression of “correct)’ panel produces buzzer sound.

advantage of enabling the study of complex and pattern discrimination learning as well as simpler color discriminations. The possibility of the infant hitting more than 2 panels at the same time is minimized, thus enabling (through appropriate position-counterbalancing) forced choices. The apparatus is equipped with a mechanism which prohibits reinforcement on those occasions when multiple panel-pressing occurs. The stimulus apertures are identical with one

181

Lewis P. Lipsitt another, containing a light system in each with 4 Wratten filters. It is possible to show any one of four different colors in each. Utilizing this apparatus and a door-buzzer as the reinforcement, 3 groups of ten 8-month-old Ss were subjected to different experimental conditions. Preliminary data showed that infants of 8 months tend to hit the 2 outer panels more than the middle panel regardless of the stimulating or reinforcing conditions, at least within the time limit of the 3s’ availablility. A procedure was therefore instituted in which the middle panel was available for response but was never reinforced. Each infant was subjected to six I-min periods, the aperture stimuli and the reinforcer being switched at the end of each minute. One group of Ss received a red-green discrimination problem, half of the Ss being subjected to a red-positive condition and the other half to greenpositive. For the red-positive Ss, for instance, the panel containing the red stimulus was always correct and appeared with 2 green panels. The middle panel was always green and hence negative, while the red stimulus was switched from the left to the right panel according to a prearranged random (Left, Right, Right, Left, Right, Left) sequence. The green positive Ss received identical conditions except that green was always presented with two reds, with response to the green panel resulting in reinforcement. The experimental interest was in whether the infants would respond more to the single reinforced color than to the other two panels and whether the tendency to respond to that color would increase with training. For a second group the correct stimulus was not the same color throughout, but was the “odd” stimulus. For this group, either red or green might be positive in any given minute, depending upon the color of the other 2 apertures at the moment. Half of the time red was presented with 2 greens, and the other half green with 2 reds. The stimulus order and reinforcement locus was identical for this group as the first group. The question asked was whether the infants would respond more to the reinforced panel, and whether the tendency to respond to the odd stimulus would increase over time. Finally, for a third group the reinforcement was switched from one panel to the other according to the same program as for the first 2 groups. For this group, however, no differential color stimulation was present in any 1-rnin phase. All stimulus apertures were the same color throughout each minute, with the color being changed from red to green from one minute to the next (Red, Green, Green, Red, Green, Red). Thus no differential discriminative color stimuli were present for this group as in the case of the first 2 groups. This control was introduced to assure that any increases in differential response to the positive and negative stimuli for the first 2 groups were not due to the 5s merely tracking the reinforced panel without attention to or direction from the discriminative colors.

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Learning in the First Year of Life The data for the three groups are presented in Fig. 10. For all three groups, response to the middle panel was lower than response to the S+ and Spanels. This is of no further consequence; low rate of response to that panel may be considered a joint effect of low response to middle and to lack of reinforcement at that panel. Of major concern was the differential responding to s+ and s- (left and right) in any given minute. The data were evaluated with respect both to total number of responses made by each of the groups to S+ and S - , and relative increases in response to S+ and S between the first minute and the end of the 6-min session. Both measures yielded similar results. The relative increase to S+ and Sover time was determined by computing a discrimination ratio for (a) the first OOOlTl

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Fig. 10. Data for 3 groups of 8-month-old children in 3 panel apparatus.

minute of responding, and (b) the final 5 min of responding. The discrimination ratio: S+ S++sresults in a proportion of .50 if the S responds equally to the left and right panels. If the S responds entirely to the reinforced panel, the resultant ratio is 1.00, if entirely to the negative panel the ratio is zero. All Ss having a discrimination ratio higher than 0.80 in the first minute, indicating high initial preference for the reinforced color or panel, were eliminated. The resulting analysis involved 9 Ss in the color-positive group, seven in the oddity-positive and eight in the nondiscriminative group. From the first minute to the end of training, this ratio increased from .27 to .60 for the color group, from .49 to .52 for the oddity group, and from .38 to .49 for the nondiscriminative group. The only reliable rise in choice of S+ relative to S - over this time period was that for the color-positive group ( t = 2.48, df = 8, p < .05). The performance of a few Ss in the oddity group suggested that oddity learning of the kind investigated here may be possible in some Ss of 8 months.

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Lewis P. Lipsitt Cumulative curves for individual Ss, one from the green-positive and one from the oddity condition are presented in Fig. 11. These Ss are specially selected as “learners.” Further research along these lines should introduce basal and extinction periods and, to overcome satiation effects, should involve more varied (perhaps constantly changing) reinforcing conditions. Some interesting techniques for the study of infant operant behavior were introduced by Friedlander (1961). The response studied was the baby’s downward pull on a single cotton cord suspended from the leaf of a microswitch mounted above the crib. The baby’s fist was loosely tied to the cord 100

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Fig. 11. Data for IWO subjects in 3-panel apparatus, one receiving buzzer reinforcement f o r response to the green panel, the other receiving reinforcement for response to either red or green depending on its being rhe odd color present.

for some sessions, while for others the S made the response by reaching and pulling a plastic ring attached to the cord. The number and duration of pulls were recorded in set time periods under different response-feedback conditions. Different reinforcers were studied, such as a white lamp flashing at the foot of the crib, a small light going on near the child’s fist, or two red lights being activated alternately with the beginning and end of a response. Friedlander also utilized the mother as a reinforcing stimulus, with the reinforcement light illuminating her as the child responded. The Ss were 2 males between the ages of 3 t and 7 months. One experiment involved 2 alternating conditions, 100% reinforcement or feedback, and no feedback. In a second experiment, the 2 conditions were 100% versus 25% fixed-ratio feedback. I n a

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Learning in the First Year of Life third experiment, reinforcement condition was varied (100% versus 25%) combined with 2-sec feedback for each response versus unlimited feedback with each response. In the first experiment, the infant showed greater mean durations of response during reinforcement phases, although there was no difference in number of responses per minute under the 2 conditions. Acquisition data reported did not suggest increasing differentiation of response during the 2 conditions. Over a 4-session period, differentiation in fact seemed to decrease. This might be attributed either to a failure of development of an associative process or to satiation with the reinforcer over time. In the second experiment, the infant produced longer responses under the 100% than the 25% reinforcement condition. In the third, the imposition of a 2-sec time-limit on the reinforcer with each response increased the number of responses made under both the 100% and the 2 5 % feedback conditions. Friedlander concluded that significant changes in performance by both infants were associated with experimentally controlled changes in properties of the feedback stimuli elicited by the instrumental behavior, but he made no claims as to the establishment of a learning effect. The writer adapted Friedlander’s technique for 8-month-old Ss. The infants were placed in a toddler’s chair situated conveniently near 2 plastic manipulanda approximately one foot apart (Fig. 1 2 ) . The manipulanda were capsules each containing a flashlight bulb, lighted on appropriate occasions, and both could be grasped and pulled by the child. An encased wire led from each capsule to an overhead box containing microswitches, for recording pulling responses and enabling electrical activation of any reinforcer used. In Fig. 12 may be seen two reinforcement lamps placed in the front of S on the floor within sight. These lights were attractively colored. All controls for the apparatus, as well as response-counters, were operated from an adjoining room with a connecting one-way mirror. The infant’s mother stayed with the child, just outside of the direct line of vision. The two-manipulandum procedure was devised to enable study of the infant’s discriminative behavior within each phase rather than between alternating phases involving reinforcement and nonreinforcement. In some preliminary work, it was found difficult to maintain the Ss’ attention to a single manipulandum which was on some occasions S+ and on others S-. The flashlight could be made to shift from one capsule to the other, counterbalancing for position, with the lighted capsule of the two always serving as S+. A 9min procedure was utilized with fourteen 8-month-old children. The first minute consisted of two basal phases, with S+ on the left for the first 30 sec and on the right for the next. Four minutes of conditioning followed, with S+ being alternated from left to right at the end of each minute, and the reinforcer working for the lighted side throughout. This was followed by 1

185

Lewis P. Lipsitt

Fig. 12. Two-manipulandum apparatus. Flashlight can be lit in either capsule. When lighted capsule is pulled, reinforcement lamps in front of child are activated.

186

Learning in the First Year of Life min identical with the basal period (an extinction phase), then by 2 min of reconditioning, then 1 min of re-extinction. Data over the entire group of 14 Ss did not indicate reliable acquisition of discriminative behavior appropriate to the conditioning and extinction circumstances. One problem was that 11 of the 14 Ss responded more to S+ than S- during the basal period, indicating an already high operant level or preference for the lighted capsule. However, one exemplary S (exemplary in the sense of excellent rather than typical) started with a low rate of S+ and developed the discrimination strikingly over the first 4-min conditioning 50

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Fig. 13. Data for one 8-month-old subject in 2-manipulandum apparatus, showing increase in response during conditioning period, diminution of reIponse during extinction period, reconditioning, and re-extinction.

period, virtually stopped responding during the first extinction phase, responded differentially again during the second conditioning phase, and again stopped responding during the final extinction phase. The data obtained from this S are presented graphically in Fig. 13. The same task and a similar procedure involving a basal, conditioning, and extinction phase were used in a study by Lipsitt and Simmons (1963) of twenty-four 12-month-old children. During a nonreinforced basal period, there was a tendency for the group as a whole to respond more to S+ than to S-, but this difference was not a reliable one. When the reinforcement condition was instituted, highly reliable differentiation of response ensued with more responses being made to S+ than to S-. As with the 8-month-old children, some Ssf behavior changed in the direction of increasing preference for the lighted capsule, while for others no conditioning effect occurred.

187

Lewis P. Lipsitt Discrimination ratios based upon relative numbers of responses to S+ and Swere computed for the 1-min basal condition, the 4-min conditioning period, and the 2-min extinction period. All Ss with the discrimination ratios of .80 or higher during the basal period were eliminated from statistical analysis. For the remaining 20 Ss, the mean discrimination ratios increased significantly from .46 to .59 from the baseline to the extinction period ( t = 2.44, df = 19, p < .05). A nonsignificant rise occurred from baseline through conditioning ( t = 1.63, df = 19). While the effect obtained for the group as a whole is not an overwelming one, the performance of some individual Ss, even within the time limits of this study, suggests that pursuit of techniques such as these would be profitable over longer training periods. Advances might be made by the deliberate selection of an operant response which has a relatively low base rate, and by the introduction of more effective reinforcing circumstances than those employed here. A technique for the study of exploratory behavior has been reported recently by Rheingold et al. (1962). The apparatus allows measurement of a specific response and provides for automatic sensory feedback from such responses. The infant, supported in a canvas seat inside a special cubicle, faces a movie screen 30 in. away. A 4-in.-diameter sphere mounted on an adjustable rod serves as the manipulandum just within reach of the infant’s hands. Control equipment in an adjacent room activates the stimulus-producing equipment and enables cumulative recording of responses. A movie projector and taped sound may transmit reinforcement from behind the screen. The infant‘s behavior is monitored visually and by means of a microphone over the 3’s head. The reinforcing effects of visual stimuli on exploratory behavior can be studied by comparing the infant’s behavior, displacement of the sphere a minimum distance, under a noncontingent condition with conditions in which a response activates a filmstrip showing brightly colored and moving geometric figures. Sample data presented by the authors indicated that for some Ss discrimination between the two reinforcement conditions occurred, such that more responses were emitted during contingent reinforcement phases. Procedures rather similar to the Rheingold et al. technique were developed by Smith and Smith (1962) who carried out exploratory investigations involving control of visual stimulation by the infant’s own behavior. In one study, infants from 4 months of age upward were placed in a playpen which could be made to revolve once every 26 sec, either independently of the child’s behavior, or contingent upon a vocal response which activated a relay. Each S spent 20 min in the playpen, half of the time on continuous rotation and half under a condition in which the playpen rotated once for every vocal response. These conditions were temporarily counterbalanced. Older Ss gave significantly more vocalizations during the contingent phase than during the continuousrotation phase, but children under 12 months showed no vocalization differences

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Learning in the First Year of Life in the 2 periods. Although the technique appears promising, it is possible that the infant response to movement-stoppage is a vocal one (for instance, crying) which would reactivate the revolving motion. Smith and Smith believe that this sometimes occurred but that on other occasions the increased vocalizations were due to direct response leading to control of the movement of the pen. In another similar study, Smith and Smith put infants from 10 months upward into the revolving pen with a TV screen just outside and in view of the S if he positioned himself properly. The child had to make accomodative responses to the movement of the playpen in order to maximize visual stimulation from the screen on which pictures of the mother and strangers could be projected. The pertinent measure was the amount of time that the S watched the screen when the mother, a stranger, or no image was present. Sufficient information was not provided on infants within the first year for the results to be pertinent here, but the general procedures reflect a technological advance that might be pursued profitably by researchers with very young children.

D. AN ISSUE: OPERANT CONTROLVERSUS OPERANTLEARNING In the previous section, operant learning was defined as a process by which an organism comes to respond with increasing frequency over time and as 3 result of certain associative manipulations. It seems necessary to specify those circumstances which produce learned changes in operant behavior, to distinguish such learning from behavior change of a nonassociative variety. This is essentially the problem to which Rheingold et al. (1959) addressed themselves, stating that the increase in responsiveness during the reinforcement phase of their experiment may have been due to response-eliciting or arousal properties of the reinforcement which could increase rate of response without learning taking place. The necessity of this distinction is dictated by the obvious fact that it is possible to induce changes in rate of behavior by circumstances other than learning. One non-learning condition which can produce change in response is increasing age or maturational development. For instance, with increasing age an infant’s physiological threshold of reaction to a given tone may become lower and hence his rate of response to it higher. For this reason, in classical conditioning experiments with infants, a control group is often run which receives CS-alone stimulations for a number of trials equivalent to the paired CS-UCS stimulations of the conditioning group. Another effect is that of pseudoconditioning, in which the threshold of response to a given stimulus is altered by presentations of some other stimulus. In classical conditioning, a group may receive presentations of UCS alone for a number of trials com-

Lewis P. Lipsitt parable to those received by the paired-presentation group, in order to assure that a conditioning effect (change in behavior as a result of paired presentations) has really taken place in the paired presentation group. The Rheingold et al. reservations with respect to their own data relate to this second process by which behavior changes occur in the absence of an associative process. To construct a ridiculous example of behavioral control or a rate-of-response measure in the absence of an associative process, consider that the number of vocalizing responses of infants may be reduced merely by placing a hand over the child’s mouth. If one is merely interested in behavioral control, then this procedure works, and it can be demonstrated that rate of vocalizing is greater without the hand than with. But under these conditions, no associative process is involved, at least on the part of the child, In order to establish that an associative process has been produced in the S, it would be necessary to provide an additional test such as, for example, presentation of the hand (without putting it over the child’s mouth) and noting whether its presence following training depresses response below the level found in the absence of the hand. As in classical conditioning, the definition of operant learning dictates the nature of the experimental controls that must be introduced. Animal researchers are often not concerned with the distinction and perhaps need not be for certain uses of the operant technique. They are sensitive mostly to conditions which influence rate of response apart from the process that is involved in the actual rise and fall of that rate. For instance, response output under one schedule of reinforcement is often compared with output under another schedule, after the animal has been already trained to respond to the responsebar or -key. At this stage of child research, it seems necessary for child psychologists to be more interested in the circumstances shaping up the operant response and the process leading to the stable operant level with which most animal experiments begin.

VII. Summary Techniques used to study learning processes in infants from birth to one year of age have been reviewed. Most of these procedures have been developed over the past 50 years, but few have been exhaustively explored with respect to the various parameters affecting the learning process or their applicable age range. Studies of learning within the first year of life are scarce and tend to be products of single attempts, some successful and some not, to demonstrate classical and operant conditioning phenomena. Few of these studies have involved systematic manipulation of variables known to affect the acquisition rate of learned behavior. Evidence seems ample that learning occurs within

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Learning in the First Year of Life the first three weeks of human life, quite probably within the first few days, but experimental procedures for its stable establishment have not yet been explored fully or refined sufficiently. Recent advances in the design and construction of stimulating and recording equipment, as well as a current resurgence of interest in early learning behavior, will probably impel more intensive studies of infant learning by increasing numbers of researchers. At present, our total information about such processes in surprisingly scant. Infant learning techniques utilized by others and in the author’s laboratory, along with suggestive but as yet relatively inconclusive data, have been presented. Refinements in some of these techniques are required and could result in the acquisition of important knowledge about infant learning. Additionally, such research is likely to make interesting contributions to general psychology, for no personality or developmental theory is without assumptions concerning the early learning process and the role of early learning in the determination of later behavior. Some observations were made concerning definitional and methodological issues within the field of learning which are or should be of as much concern to the experimental child psychologist as to researchers with animals.

REFERENCES Aldrich, C. A. A new test for hearing in the newborn: the conditioned reflex. Amer. J. Dis. Child., 1928, 35, 36-37. Babkin, P. S. The establishment of reflex activity in early postnatal life. Fiziologi Zhurnaf USSR., 1958, 44, No. 10, 922-927. (Translation in The Central Nervous System and Behavior, Russian Medical Literature, prepared by Russian Scientific Translation Program, N.I.H., Dec. 1, 1959. Pp. 24-33). Bartoshuk, A. K. Response decrement with repeated elicitation of human neonatal cardiac acceleration to sound. J. romp. physiol. Psychol., 1962a, 55, 9-13. Bartoshuk, A. K. Human neonatal cardiac acceleration to sound: habituation and dishabituation. Percept. mot. Skills, 1962b, 15, 15-27. Blauvelt, H. H. Capacity of a human neonate reflex to signal future response by present action. Child Develpm., 1962, 33, 21-28. Brackbill, Y. Extinction of the smiling response in infants as a function of reinforcement schedule. Child Develpm., 1958, 29, 115-124. Brackbill, Y.Experimental research with children in the Soviet Union: report of a visit. Amer. Psychol., 1960, 15, 226-233. Brackbill, Y . Research and clinical work with children. M. Bauer, R. A. (Ed.) Some views on Soviet Psychology, Washington: Amer. Psychol. Assn., 1962. Pp. 99-164. Bregman, E. An attempt to modify the emotional attitudes of infants in the conditioned response technique. J . genet. Psychol., 1934, 45, 169-198. Bridger, W. H. Sensory habituation and discrimination in the human neonate. Amer. J . Psyrhiatr., 1961, 117, 991-996.

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Lewis P. Lipsitt Bronshtein, A. I., Antonova, T. G., Kamenetskaya, N. H., Luppova, V. A., & Sytova, V. A. On the development of the functions of analyzers in infants and some animals at the early stage of ontogenesis. In Problems of evolution of physiological functions. Acad. Sci., U.S.R.R. 1958 (Dept. of Health, Educ. and Welf. U.S.A., Translation Service) Caldwell, D. F., & Werboff, J. Classical conditioning in newborn rats. Science, 1962, 136, 1118-1119. Cornwell, A. C., & Fuller, J. L. Conditioned responses in young puppies. J. romp. physiol. Psychol., 1961,54, 13-15. Crowell, D. H., Peterson, J., & Safely, M. A. An apparatus for infant conditioning research. Child Developm., 1960,31, 47-52. Denisova, M. P., & Figurin, N. L. The problem of the first associated food reflexes in infants. Vopr. Genet. Re$. Pedol. Mladen, 1929, 1-88. (See Razran, 1933). Disher, D. R. The reactions of newborn infants to chemical stimuli administered nasally. Ohio State Univer. Stud. Inf. Behav., Columbus: Ohio State Press, 1934, No. 12, 52. Elkonin, D. B. The physiology of higher nervous activity and child psychology. In B. Simon (Ed.), Psychology in the Soviet Union. London: Routledge and Kegan Paul, Ltd. 1957.Pp. 47-68. Engen, T., Lipsitt, L. P. & Kaye, H. Olfactory responses and adaptation in the human neonate. J. romp. physio. Psychol., 1963,56, 73-77. Forbes, H.S., & Forbes, H. B. Fetal sense reaction: hearing. J. comp. Psychof., 1927, 7, 353-355. Friedlander, B. Z.Automated measurement of differential operant performance. Unpublished manuscript. (Abstract, Amer. Psychol., 1961, 16, p. 350.) Fuller, J. L., Easler, C. A., & Banks, E. M. Formation of conditioned avoidance responses in young puppies. Amer. J. Physiol., 1950, 160, 462-466. Golubeva, E. L. Conditioned reflexes of the newborn guinea pig. Psychol. Abstr., 1939, 13, No. 6113. Graham, F. K., Matarazzo, R. G., & Caldwell, B. M. Behavioral differences between normal and traumatized newborns. Psychol. Monogr., 1956, 70, Nos. 20 and 21. Gruntke, M. E. A liquid dispenser for primates. J . exp. anal. Behav., 1961, 4, 326. Gunther, M.Instinct and the nursing couple. Lancet, 1955,1, 575. Gunther, M. Infant behavior at the breast. In B. Foss, (Ed.), Determinants of Infant Behavior. London: Methuen and Co., Ltd. 1961. Pp. 37-44. Harlow, H. F. The development of learning in the rhesus monkey. Amer. Scient., 1959, 47, 459-479. Hinde, R. A. Changes in responsiveness to a constant stimulus. Brit. J. Anim. Behav., 1954a,2, 41-55. Hinde, R. A. Factors governing the changes in strength of a partially inborn response. PYOC.YO^. SOC., 195413,142-B,306-358. Irwin, 0. C. Amount and nature of activities of newborn infants under constant external stimulating conditions during the first ten days of life. Genet, Psychol. Monogr., 1930, 8, 1-92. Jones, H. E. The galvanic skin reflex in infancy. Child Develpm., 1930a, 1, 106-110. Jones, H. E. The retention of conditioned emotional reactions in infancy. Pedagog. Sem. c5 J . genet. Psychol., 1930b,37, 485-498. Kantrow, R. W. An investigation of conditioned feeding responses and concomitant adaptive behavior in young infants. Univer. la. Stud. Child Welf., 1937, 13, No. 3, 64.

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Learning in the First Year of Life Kasatkin, N. I., & Levikova, A. M. On the development of early conditioned reflexes and differentiations of auditory stimuli in infants. J. exp. Psychol., 1935a, 18, 1-19. Kasatkin, N. I., & Levikova, A. M. The formation of visual conditioned reflexes and their differentiation in infants. J. gen. Psychol., 1935b, 12, 416-435. Kasatkin, N. 1. Early conditioned reflexes in the child. J. Higher Nerv. Activ., 1952, 2, 572-581. Kasatkin, N. I., Mirzoyants, N. S., and Khokhitva, Oriented conditioned reflexes in infants during the first year of life. J. Higher Nerv. Activ., 1953, 3, 192-202. Kasatkin, N. I. Early ontogenesis of reflex activity in the child. Zhurnal vysshey nerunoy deyatel'nosti, 1957, 7, 6: 805-818. (Translated by National Institutes of Health, USPHS Feb. 31, 1960.) Lehner, G. F. J. A study of the extinction of unconditioned reflexes. J. exp. Psychol., 1941, 29, 435-456. Leventhal, A. S. Adaptation, pitch discrimination and sound localization in the neonate. Unpublished master's thesis. Brown University, 1963. Levin, G. R., & Kaye, H. Non-nutritive sucking by human neonates. In press, Child Deuelpm. Ling, B. C. Form discrimination as a learning cue in infants. Comb. Psychol. Monogr., 1941, 17, No. 2, 66. Lipsitt, L. P., & DeLucia, C. An apparatus for the measurement of specific response and general activity of the human neonote. Amer. J. Psychol., 1960, 73, 630-632. Lipsitt, L. P., & Kaye, H. Conditioned sucking in the human newborn. Unpublished manuscript, Brown University, 1963. Lipsitt, L. P., & Levy, N. Electrotactual threshold in the neonate. Child Deuelpm., 1959, 30, 547-554. Lipsitt, L. P., & Simmons, M. W. Operant discrimination learning in twelve-month-old children. In preparation, Brown University, 1963. Marinesco, G., & Kreindler, A. Des reflexes conditionnels: L'organization des reflexes conditionnels chez I'enfant, J. d e Psychol., 1933, 30, 855-886. Marquis, D. P. Can conditioned responses be established in the newborn infant? J. genet. Psychol., 1931, 39, 479-492. Marquis, D. P. Learning in the neonate: The modification of behavior under three feeding schedules. J. exp. Psychol., 1941, 29, 263-282. Marum, K. D. A study of classical conditioning in the human infant. Unpublished master's thesis, Brown University, 1963. Mason, W. A., & Harlow, H. F. Formation of conditioned responses in infant monkeys. J . romp. physiol. Psychol., 1958, 51, 65-70, Mateer, F. Child behavior: a critical and experimental study of young children by the method of condirioned reflexes. Boston: Gorharn Press, 1918. McGeoch, J. A., & Irion, A. L. The psychology of human learning. New York: Longmans, Green and Co., 1952. Morgan, J. J. B., & Morgan, S. S. Infant learning as a developmental index. J. genet. Psychol., 1944, 65, 281-289. Munn, N. L. Learning in children. In L. Carmichael (Ed.), Manual of Child Psychology. New York: Wiley, 1954. Pp. 374-458. Munn, N . L. T h e evolution and growth of human behavior. Boston: Houghton Mifflin Co., 1955. Papousek, H. A method of studying conditioned food reflexes in young children up to the age of six months. Pavlov J. Higher Nerv. Activ., 1959, 9, 136-140.

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Lewis P. Lipsitt Papousek, H. Conditioned motor alimentary reflexes in infants. I. Experimental conditioned sucking reflexes. CesR. Pediatr., 1960a, 15, 861-872. Papousek, H. Conditioned motor alimentary reflexes in infants. 11. A new experimental method of investigation. Cesk. Pediatr., 1960b, 15, 981-988. Papousek, H. Conditioned head rotation reflexes in infants in the first months of life. Arta Pediatr., 1961, 50, 565-576. Peckham, G. W., & Peckham, E. G. Some observations on the mental powers of spiders. J. Morph., 1887, 1, 3 8 3 4 1 9 . Peiper, A Sinnesempfindungen des Kindes vor seiner Geburt. Monatssche. f . Kinderhk., 1925, 29, 236-241. Piaget, J. The use of reflexes. Origins of Intelligence. New York: International Universities Press, 1952. Pp. 23-42. Polikanina, R. I. The relation between autonomic and somatic components in the development of the conditioned reflex in premature infants. Pavlov. J . Higher Nerv. Activ., 1961, 11, 51-58. Prechtl, H. The directed headturning response and allied movements of the human baby. Behaviour, 1958, 8, 212-242. Prosser, C. J., & Hunter, W. S. The extinction of startle responses and spinal reflexes in the white rat. Amer. J. Phys., 1936, 117, 609-618 Ray, W. S. A preliminary report on a study of fetal conditioning. Child Develpm., 1932, 3, 175-177. Razan, G. H. S. Conditioned responses in children: a behavioral and quantitative review of experimental studies. Arch. Psychol., 1933, 23, No. 148, 120. Rendle-Short, f. The puff test. Arch. Dis. Childh., 1961, 36, 50-57. Rheingold, H. L., Gewirtz, J. L., & Ross, H. W. Social conditioning of vocalizations in the infant. J. romp. physiol. Psychol., 1959, 52, 68-73. Rheingold, H. L., & Stanley, W. Developmental psychology. Ann. Rev. Psychol., 1963, 14, 1-28. Rheingold, H. L., Stanley, W. C., & Cooiey, J. A. Method for studying exploratory behavior in infants. Science, 1962, 138, 1054-1055. Simmons, M. W. Operant discrimination in infants. Unpublished doctoral dissertation, Brown University, 1962. (In press, Child Develpm.) Simmons, M. W., & Lipsitt, L. P. An operant-discrimination apparatus for infants. J. exp. anal. Behav., 1961, 4, 233-235. Smith, K. U., & Smith, W. M. Infant control of the behavioral environment. Perception and Motion, Philadelphia: W. B. Saunders Co., 1962. Pp. 277-290. Sontag, W. W., & Wallace, R. F. A study of fetal activity: a preliminary report of the Fels Fund. Amer. J. Dis. Child., 1934, 48, 1050-1057. Spelt, D. K. The conditioning of the human fetus in utero, J. exp. PIychof., 1948, 38, 375-376. Spiker, C. C. Research Methods in Children’s Learning. In P. H. Mussen (Ed.), Handbook of Research Merhods in Child Development. New York: John Wiley and Sons, 1960. Pp. 374-420. Stanley, W. C., Cornwell, A. C., Poggiani, C., & Trattner, A. Conditioning in the neonatal puppy. J. romp. physiol. Psychol., 1963, 56, 211-214. Thorndike, E. L. Animal intelligence: an experiniental study of associative processes in animals. Psyrhol. Monogr., 1898, 2, No. 8. Thorpe, W. H. Sympos. SOC. exp. Biol., 1950, 4, 387. Valentine, C. W. The colour perception and colour preferences of an infant during its fourth and eighth months. Brit. J. Psychol., 1914, 6, 363-386.

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Learning in the First Year of Life Watson, J. B., & Rayner, R. Conditioned emotional reactions. J . exp. Psyrhol., 1920, 3, 1-14. Weisberg, P. Social and nonsocial conditioning of infant vocalizations. Child Develpm., 1963, 34, 377-388. Wenger, M. A. An investigation of conditioned responses in human infants. In M. A. Wenger, J. M. Smith, C. Hazard, and 0. C. Irwin, (Eds.), Studies in infant behavior III. Univer. l a . Stud. Child Welf., 1936, 12, No. 1, 7-90. Wertheimer, M. Psychomotor coordination of auditory and visual space at birth. Science, 1961, 134, 1692. Wickens, D. D., & Wickens, C. A study of conditioning in the neonate. J . exp. Psythol., 1940, 26, 94-102.

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J'OME METHODOLOGICAL CONTRIBUTIONS FROM A FUNCTIONAL ANALYSIS OF CHILD DEVELOPMENT'

Sidney W . Bijou and Donald M. Baer UNIVERSITY OF WASHINGTON

I. THE LABORATORY-EXPERIMENTAL METHOD APPLIED TO PAST INTERACTIONS: AN EXAMPLE OF ABSTRACTION LEARNING

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111. SOME METHODOLOGICAL PROBLEMS IN THE ANALYSIS OF SOCIAL REINFORCEMENT

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'Many of the studies by the authors cited in this chapter, and the preparation of the chapter per se were supported in large measure from two grants (M-2208 and M-2232) from the National Institute of Mental Health, Public Health Service.

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Sidney W . Bijotl and Donald M. Baer We shall discuss two methodological problems of child behavior and development from what we choose to call a functional point of view. For US this phrase implies an approach in which only objectively defined concepts are used and the behavior of the child is related directly to observable elements of his present circumstances and past interactional history. On the surface this description may seem to be merely a reiteration of nearly universal current research practices with children, On closer scrutiny this will be found not to be the case. Therefore, prior to our discussions of research we shall make explicit what we mean by psychological development and point out some of its implications. We take a specific view of the nature of “development.” A psychological organism as such is in interaction with its stimulus environment. These interactions usually change in the course of experience. The change constitutes a development of the organism, and will be understood only when the conditions necessary to produce the change have been demonstrated. Thus, an infant at one age may produce vocal sounds in which a great variety of simple phonemes occur; a few months later his vocal behavior may consist of a smaller set of sounds which are beginning to resemble syllabic English. So far, only a description of change over time has been made. A developmental analysis would proceed by investigating the stimuli controlling this pattern of change. Perhaps it would be found that a caretaker emits syllabic speech on occasions of reinforcement and that syllabic sounds thereby become secondarily reinforcing; hence behaviors by the infant with his own vocal apparatus that produce those sounds, or sounds like them, grow stronger. A demonstration of this would provide a developmental analysis, in that it would specify the events that produce the change. The essence of development in this sense is the ongoing sequence of interactions between behavior and environment, each part of the sequence contributing to the effect of the next interaction in the sequence. Naturally, any sequence of interactions requires time, and so development is invariably confounded with the passage of time. However, we expect that little of the changing behavior of a child is produced by the passage of time alone. Therefore, a deveiopmen$al analysis is not a relationship of behavior to age, but is a relationship of behavior to events which, requiring time in order to occur, will necessarily have some correlation with age. The correlation, of course, will be important to anyone planning, let us say, a program of study for the average ten-year-old; but it will not be important to an understanding of the processes of development as such. The sequence of interactions between behavior and environment may be analyzed in different ways: (1) as increases in the number of responses to the same object (e.g., from only putting a cube into the mouth to doing that plus throwing it on the floor, putting it in a box, placing it on top of another cube, etc.), (2) as increases in the length of the sequence of behavior to an

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Contributions f r o m a Functional Analysis object which defines the ultimate response (e.g., from turning the head toward a rattle, to doing that plus reaching for it, grasping it, and bringing it to the mouth), ( 3 ) as increases in the number of responses to objects at the same time (e.g., from walking to walking, talking, and bouncing a ball simultaneously), and ( 4 ) as increases in the form of a response or in skill in any of the above behaviors (e.g., the awkward walking of a 2-year-old as compared to the smooth locomotion of a 6-year-old). Sequential changes are also made in the things responded to in the environment. They are displayed by increases in the range and complexity of the events which become a part of the child’s environment. Included are reactions to new stimuli (due to changes in sensory thresholds, like pain, for example), to gross differences between apparently similar stimuli, to subtle similarities and differences between stimuli (those in which only one or two dimensions of the stimuli are critical in determining choice, as in concept formation and abstraction), and to more and more complex stimulus patterns arranged temporally (like notes in music) or simultaneously (like the interactions of a group of children at a birthday party). Psychological development, conceived of as changes in interaction between stimuli and responses, will not be a significant and workable concept unless we specify what we mean by a stimulus and a response. First, let us consider the concept of a stimulus. A stimulus event may be described by its physical properties: its size, color, shape, weight, movement, etc. However, a stimulus may also be described by its functional properties. For example, a tone may be characterized by the physical changes in electrical impulses on an oscilloscope and by the behavioral changes it produces in a specific organism. The onset of the tone may be correlated with an orienting response (a child may stop playing with his blocks at the sound of the tone and look around), or it may serve as a signal for a learned response (it may “mean” to the child someone is at the door), or it may strengthen the response which preceded it (if sounded after the child opens a little box, he may open it more often). Thus the tone may be described by one or more of its physical dimensions (wave length, amplitude, and composition), and by one or more of its functional characteristics (eliciting, discriminative, and reinforcing). It follows from the above that events which constitute the environments of development are those that are reacted to by the child. The child’s world is composed of the stimuli that have effects on his behavior. The people around him do not make up this social environment, but people in specific interactions with him do. The furniture, house, and countryside do not make up his physical environment, but the specific interactions between them do. Stimulus events inside the organism are part of the environment and are analyzed in the same way as external stimuli. No additional assumptions are required. This conception of internal stimuli may seem overly simplified. How-

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Sidney W . Bijou and Donald M. Baer ever, full recognition is given to the fact that stimulus events within the bodywall are often tantalizingly inaccessible and pose many difficulties for a natural-science approach. Both physical and functional descriptions of stimuli are essential in analyzing interactions-that is, we need to know the properties of stimuli independent of the actions of the subject as well as in relation to the subject and his setting. Let us now turn briefly to the concept of a response event. This arbitrary segment of the total functioning organism, like a stimulus event, may also be analyzed in terms of its physical and functional properties. Physical analyses of responses are usually in terms of space-time dimensions, such as frequency, latency, and amplitude. The nature of the data will of course depend upon the particular dimension selected (Gilbert, 1958). Functional analyses of responses are made in terms of these actions in relation to stimuli. To say that a response has a response function is to say that it interacts with a class of stimuli in a discernible way. Thus a response function may be conceived of as the reciprocal of a stimulus function. For example, some movements in space over time close doors and thereby keep out annoying drafts, or place glasses on one’s nose and bring visual stimulus patterns into clearer focus. In many studies in child behavior the functional properties of stimuli and responses are not determined by observing the interaction of the subject’s reactions to stimuli, but rather are asserted by the experimenter. For example, frequently a stimulus is presented following a response in a learning task and is said to be a reward, an incentive, or a reinforcer, apparently because the experimenter thought it ought to be, on the basis of his impressions of the behavior of similar organisms in and out of experimental situations. The same is often done in defining “disapproval” as mild punishment. In group studies it may be that many of the subjects will respond in a way that is in agreement with the experimenter’s decision, but it is also likely that some will react in an opposite or neutral fashion. The experimenter’s predetermining the functional property of a stimulus or response for a given individual has been one of the practices that has produced contradictory findings on more than one basic behavioral process. This point will be developed further in a later discussion of social reinforcement. In the research discussed in this chapter two methodological problems will exemplify and expand this view of development. In both cases the behavior of concern is operant, i.e., behaviors controlled by their stimulus consequences. The first section will deal with the problem of applying the laboratory-experimental methods to the child’s past history of interactions, as exemplified by an analysis of stimuli antecedent to this class of behavior. I n the area of antecedent stimulation we shall focus our discussion on examples from discrimination learning, concept formation, and abstraction.

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Contributions from a Functional Analysis The second section will deal with stimulation consequent to behavior. The specific problem area will be a methodological problem of central importance in child development: social reinforcement. The important stimuli involved in a great deal of a child’s development are social stimuli. Almost any analysis of human social development from the point of view of modern behavior theory postulates an essential role for social reinforcers.

I. The Laboratory-Experimental Method Applied to Past Interactions : An Example of Abstraction Learning Few psychologists will disagree with this basic assumption: changes in behavior can be a function of genetic endowment, the current situation, and past interactions. Our concern here is not with the possibility of further subdivisions or with arguments relative to the importance of each class in effecting behavioral changes, but rather with the application of the laboratoryexperimental method with particular reference to interactions that have taken place in the past. With respect to the application of the laboratory-experimental method to the genetic constitution of human organisms, one is forced to conclude that this is not now a possibility, simply because the independent variables in the field of human genetics are not available for experimental manipulation, by the psychologist or even by the experimental geneticist. Under these circumstances the developmental psychologist must take the product of genetic interaction as given at the time he begins his study. This point of view has been elaborated by Beach (1955) and Verplanck (1955), among others. It is clear that in recent years more investigators have been attacking old and new problems by laboratory procedures and have, at the same time, been developing new experimental techniques for studying humans ranging from the neonate (e.g., Lipsitt and DeLucia, 1960; Crowell et al., 1960) to the young adolescent (Cohen, 1962). Continued efforts along these lines promise a laboratory technology that should accelerate advances in the cumulation of empirical developmental laws. It is also clear that the laboratory-experimental method has undoubtedly had its greatest application in the analysis of current situations (Bijou and Baer, 1960; Spiker, 1960). One may wonder why there have been relatively few attempts to utilize the laboratory-experimental method for studying past interactions. Clearly the investigator interested in information on past interactions may proceed along one or more of the following paths: (1) He may obtain retrospective accounts of historical events by structured interviews, questionnaires, surveys and the like. (2) H e may administer achievement tests, intelligence tests,

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Sidney W . Bijou and Donald M . Baer and social maturity scales and the like to obtain some information on the current consequences of past experiences. ( 3 ) He may manipulate current conditions and observe changes in behavior in certain specific situations at some future time-that is, he may create a history which will be the child’s “past.” Although convenient to use, both the retrospective accounts and the psychometric procedures rest heavily on the quality of the supporting information on the reliability and validity of the instruments involved. On the other hand, the experimental approach is often difficult to arrange and manage. Perhaps this explains its infrequent use. However, despite the practical difficulties of laboratory procedures for exploring the effects of early experience on later behavior, several well-known studies have been carried out. For example, during the period in the history of child psychology when interest ran high on the relative importance of such global terms as maturation and learning, Dennis (1941) studied the development of fraternal twins who were exposed to restricted social stimulation and limited motor movements during a 14-month period. At 9 months of age their motor coordination as demonstrated by sitting and walking behavior and social behavior was compared with children who were not so limited. At about the same time, Gesell and Thompson (1929) studied the effect of extra stimulation on stair-climbing and cube-building in twins. One twin was given experiences in these activities for 10 min a day for 6 weeks. At the end of this period the other twin was given experience in the same activities for 2 weeks. They were then compared. In a similar fashion, McGraw (1935) carried out an extensive study on the effects of a special program on fraternal twins. One child was given experiences in a series of motor activities. This sequence extended from 2 1 days to 2 2 months of age. The other twin was only given motor tests at regular intervals. Still another example of the effects of extra stimulation is a study by Josephine Hilgard (1932) on preschool children in which one group was given extra experience in cutting with scissors, climbing a ladder, buttoning, etc., for a period of 12 weeks. Their performances were compared with those of a control group which received no special experience. Two other studies, one conducted earlier than those mentioned above and one relatively recent, dealt with past influences in a more circumscribed fashion and used the individual child as his own control. The first is the well-known study by Watson and Rayner (1920) on the development of fear reactions in a young child. They showed that the child was not afraid of a white rat. Then the sight of the animal was paired with a loud noise which elicited “fear” reactions. At specific times after the pairings the child’s behavior was observed in the presence of the rat and in the presence of other stimuli which varied in their degree of resemblance to the animal. The other study, by Blau and

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Contributions from a Functional Analysis Blau (1955), was concerned with a relatively specific interaction over a short time span-the effect of the ease or difficulty of extracting milk from a nursing bottle on non-nutritive sucking between feedings. Feedings by means of a nursing bottle with a relatively small opening in the nipple were followed by observations of behavior between feedings. The procedure was then repeated with a nipple with a relatively large opening and observations were repeated. Viewing the studies described above from a historical perspective, it seems that those that have been concerned with specific relationships among functionally defined terms, like the Watson and Rayner study, have made more impact, i.e., have been cited more often as examples of developmental phenomena.

11. Another Approach to an Experimental Study

of Past Experiences Another variation on the application of the laboratory-experimental method to the study of past interactions has emerged from works like that of Jeffrey on the effect of prior experience on discrimination learning and those of many investigators concerned with programmed instruction. The strategy of this approach is as follows. ( 1 ) Select a form or class of behavior that seems essential to the performance of some everyday task, or one that is simply interesting to the development of behavior. ( 2 ) Describe the behavior in detail and in objective terms, i.e., establish a reliable set of clearly specified criteria. ( 3 ) O n the basis of available information, prepare a sequence of materials and establish a procedure aimed at enabling the individual to perform such a task. (4) Find children who cannot perform as required (even though they possess the obvious biological equipment) or who perform it poorly and give them training on the sequence. (5) If the training does not enable them to perform according to specifications, modify the sequence in a systematic manner until it does. Such an experimental history would not be expected to coincide with the way children of comparable age learn the same task in their everyday experiences in the home, school, and play groups, since (1) the same criterion performance could, in all probability, be learned by other sequences, and ( 2 ) interactions in everyday living which interfere, decelerate, and negate such learning are experimentally eliminated. It would, however, provide one account of the variables of which such behavior is a function. Jeffrey (1958a,b) used this strategy in discriminations of right- and leftoriented drawings and differences in tones separated by three octaves and a fifth. I n his study on right-left orientation, Jeffrey was interested in testing the

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Sidney W . Bijou and Donald M. Baer effect of previously learned and relatively simple motor responses to the stimuli on learning the more difficult response of labeling them. The subjects were 28 children divided into 2 groups. They were matched to give a mean chronological age of 4 years and 4 months. Stick-figures were drawn on cards with either the left or the right arm raised. For the motor responses there were 2 push buttons, 1 2 in. apart, on the top of a box. Taperecorded music through earphones served to reinforce correct responses. In the initial period the music was stopped and the stimuli were placed side by side on the box, The child was asked if he could tell how the two figures differed. None of them gave evidence of seeing any difference or knowing what “difference” meant. The differences were then pointed out and the children were told to call one figure Jack and the other Jill, and that the music would come on only after the correct response. The stimuli were then presented in random order. Training continued, with the instructions repeated at intervals. After this initial training, the experimental group was instructed to push the button toward which the figure was pointing. Training continued until a criterion of ten successive correct responses was met and then the child was returned to perform the labeling task. The experimental treatment of learning to press buttons was readily learned by all children in the experimental group, and this training was found to have a significant facilitating effect on subsequent learning to apply labels. Jeffrey remarked on the basis of the results that some discriminations might be simplified, so that having learned the simpler task, the child is facilitated in mastering the more difficult. He also suggested that it might be possible to simplify the stimuli as well as the response, for example by lengthening the arms of the figures. In a sense, Jeffrey was suggesting that one could go beyond the question of the role of mediating processes in discrimination and explore the sequence of modifications necessary for effective learning of this sort. Such an objective accurately describes the goal of investigators concerned with programmed instruction. For example, Holland and Long made exploratory studies on “inductive reasoning” in young children (Holland, 1963). Audrey Holland and Mathews (1963) analyzed some of the steps in the development of the ( S ) phoneme in children with defective articulation, and Moore and Goldiamond (1963) examined the “fading in” process in establishing discrimination of geometric forms in preschool children. In the same spirit, Bijou has conducted a study of training in the discrimination of mirror-images.* A brief description of it will serve as an example of the application of this approach. ‘This study was conducted during 1961-1962, while the senior author was on a NIMH Senior Fellowship at Harvard University working with B. P. Skinner and J. G . Holland.

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ABSTRACTION AND MIRROR-IMAGE DISCRIMINATIONS The general problem was the process by which a child learns to respond to one dimension of a stimulus and ignore all others. In other words, this is the problem of abstriction as analyzed by Skinner (1953). The specific task was the discrimination of mirror-images of a geometric form despite full rotations Original

Nonsense

Alphabet

I J U V

0 0 Z

s 9 P

Fig. I . Forms used in mirror-image training and pre- and post-testing.

of the form in the vertical plane. The ten forms used are shown in column 1 of Fig. 1. The material was presented in a match-to-sample apparatus, which is a variation on a device used extensively in infrahuman research. It was originally conceived by Skinner and further developed by Holland and Long (Holland, 1960, 1963). The device consists of a box with a panel of windows to display the stimuli and also to register selections, a 2 x 2 slide projector, and an

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Sidney W .Bijou and Donald M . Baer event recorder. The child was seated so as to face the two horizontal, translucent plastic windows. The upper window was a single unit, the lower one was divided into 5 equal parts. The geometric forms shown in Fig. 1 were projected on the windows from behind. One form appeared in the center of the large upper window and one in each of the 5 lower windows. The form in the upper window was the sample; those in the lower windows, the matches. The sample was presented first. The matches appeared only after the child pressed on the sample window. Temporal relationships between the presentations of the sample and choices, the order of slide presentations, and a reinforcing feedback (light and chime) were controlled by automatic programming circuits. The child indicated which of the 5 forms matched the sample by pressing on the window in which it appeared. If he made a correct selection a red light glowed momentarily, a chime sounded, the sample and the 5 choices disappeared, and another sample appeared. The child could then produce the choices by pressing on the sample window and proceed to make the next match. If he made an incorrect choice, the light and chime did not operate but the matches disappeared. (There was also a clearly distinctive thud produced by the mechanism which blacked-out the matches.) Pressing on the sample window restored the choices (removed the blackout device) and provided a second opportunity for matching. If the second response was also incorrect, the choices blacked-out once more. Pressing again on the upper window restored the matches again. This sequence (press on sample window to display matches; selection of a mismatch; disappearance of matches; press on sample window to display matches, etc.) would be continued until the correct response was made. Making the correct response removed both the sample and the matches and presented another sample. Under this arrangement of contingencies the last response to a problem was always the correct response. However, when a correct response was preceded by one or more incorrect responses, the next slide presented was the previous slide. That is to say, the next slide was a repeat of the slide previously “passed” rather than an advancement to the next slide in the sequence, Thus, a child would not move forward in the program after an error without first reacting a second time to both the preceding slide and the slide just “missed.” It was therefore possible for a child to make “new” errors on slides previously passed without error, and to go backwards in the program. Slides were composed with the objective of constructing a sequence of discriminations in which the probability of a correct response to each task would be high; at the same time each would include an increment, as large as possible, of stimulus complexity in the direction of final mirror-image discriminations. In lieu of well-established empirical principles many “first approximation” assumptions were made regarding (1) the selection of the order

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Contributions from a Functional Analysis of samples, its rotational position, and its color, ( 2 ) the window location of the correct match, its rotational position, and its color, and ( 3 ) the relationships among the samples, correct matches, and incorrect matches with respect to similarities in form, color, degrees of vertical plane rotations, and window locations. After 2 pilot studies on 12 normal children between 3 and 6 years of age, the sequence of discrimination problems was organized into 3 sets: the first, called the Elementary Set, was designed to enable subjects as young as 3 to

1-10

1-1

I

‘L

I

1-24

1-20

1-40

Pig. 2 . Schematic drawings of fample shdeJ from the Elementary (above the horizontal line) and Intermediate Sets.

start and perform the procedures and move through the easy part of the program with ease; the second, the Intermediate Set, was aimed at giving the children experiences in matching forms despite their appearance in any of 1 2 rotated positions; and the third, the Advanced Set, was planned to provide the subjects with training in discriminating nonmirror-images from mirrorimages in increasing numbers and increasing discrepencies in vertical plane rotations. Sample problems from the Elementary and Intermediate Sets are shown in Fig. 2. Each is a schematic representation of a 2 )( 2 slide. The sample is the single form at the top; the choices are presented below. The 5 rectangles above the horizontal lines are samples from the Elementary Set.

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Sidney It”.Bijou and Donald M. Baer The ofie in the upper left-hand corner labeled 1-1 (signifying Unit 1, slide 1) is the starting problem. The box designated 1-24 is the last one of the set. The two boxes below the line are from the Intermediate Set; 1-20 is the problem in the middle of the set, and 1-40 the one at the end. In Fig. 3, 11 samples are shown in the Advanced Set, which has 5 units (designated by the first digit of each numerical designation). The 6 samples from Unit 1 show the gradual “fading-in” stages of constructing mirror-images. Slide 1-35 is the first complete mirror-image presented. The two samples from Unit 2 show the correct stimulus and its mirror-image r

1

I

Fig. 3. Schematic drawitigs of sample slides from the Advanced Set.

separated by 1 form ( 2 - 2 ) and by 2 forms (2-8). The example from Unit 4 (4-7) has 2 mirror-images and the first one from Unit 5 (5-3) has 3. The problem shown in 5-38 is the last in the entire sequence. Problems like it but with the forms shown as samples in 4-7 and 5-3 were established as criterion tasks. A total of 270 slides were arranged and developed on the basis of about 100 children between 3 and 6 years of age. The same sequence was explored on a group of educable retarded children in residence at the Fernald School, Waverly, Massachusetts. In addition to the training sequence, 3 sets of slides, 20 in each, were prepared to evaluate training. One set, designated as the “Original,” was made up of duplicates taken directly from the program, 4 from the Intermediate and 16 from the Advanced Set. A second set, called the “Nonsense” (see

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Contributions from a Functional Analysis column 2, Fig. 1). was like those in the Original test in area and color but differed in shape. Performances with these forms were to provide data on stimulus control of material similar to that in the program. The third test, the “Alphabet,” was composed of ten letters drawn at random (see column 3, Fig. 1 ) . The area and color of the letters were also the same as those in the Original. Performance on this series was to provide information on stimulus control of letters similar in area to the forms in the program. 5’‘ L-E (M,5-ll)

‘ “

‘Y INTER IU5 UNIT I

r _.I

UNIT 3 403

SESS3

+

A sample of the learning data obtained on the sequence is shown in Fig. 4. The subject was a normal boy, almost 6 years of age. He was started on the Intermediate Set. As shown in the upper left-hand chart, his rate was slow and fairly constant in Unit 1, but it increased in Unit 2. Only one error was made in Unit 2 (shown by a vertical pip on slide 2-21 and a “regression” to the preceding slide). In the same session, he was given Units 1 and 2 of the Advanced Set (problems designed to provide mirror-image training). As shown in the third and fourth left-hand graphs, his rate steadily decreased, and he made 4 errors in Unit 1 and 1 in Unit 2. In session 2, upper righthand graph, he was given only Unit 3 of the Advanced Set. He continued to take more time on each discrimination but made only 1 error (on slide 3-18).

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Sidney W . Bijozl and Donald M . Baer In session 3, middle and lower right-hand graphs, he was given Units 4 and 5 in the same series. His matching continued at a low rate, but he made only one error on Unit 5 (slide 5-7). Construction of a stimulus sequence that enabled normal and retarded children to discriminate between mirror-images and nonmirror-images led to many suggestions about the possible ways in which this type of stimulus control may be developed, e.g., discriminating objects which differed with respect to right-left or east-west orientation. As new findings were revealed by the empirical procedures employed, they were incorporated into the SUCcessive revisions. It was found, for example, that 3-year-olds could begin and progress quite a way through the program if they were started on a circle, square, and triangle. It was also found that the choices could be increased from 3 to 5 and that the circle, square, and triangle could be eliminated without interfering with further advancement in the sequence. Another example was that of all the ways attempted, the fading-in of a mirror-image in very gradual stages was the most promising way to get the subject to attend to the controlling dimension of the stimuli, i.e., the east-west relationship among the parts of a form. Finally, it was clear that additional mirror-images had to be introduced in very gradual stages and rotated in small steps, or else a good deal of the prior mirror-image learning would be weakened or extinguished. Further research on the problem would be expected to lead to other revisions, looking to the possibility that the task could be learned in a shorter sequence, or that the succession of training experiences could be modified. The construction of an experimental history for children who could not discriminate mirror-images produced other types of interesting data on abstracting behavior involving geometric forms. For example, training on the stimulus sequence generalized to forms not involved in the training and to letters of the alphabet. There was greater generalization to the alphabet than to novel forms for both the normal and the retarded children. Another example is that for the retarded children there was a rough relationship between mental-age test scores and progress through the program. Finally, this approach produced several parametric relationships and suggested others. One will be mentioned. It was clearly shown that the location of the sample had an influence on the selection of the match. When the discrimination was difficult there was a tendency to respond to the stimulus in the window under the sample. Further research showed that this was true whether the sample was in the middle or at the left or right sides. The constructed-history approach might be used to see how a child develops other perceptual skills, such as seeing embedded figures, synthesizing parts into wholes, or analyzing wholes into parts. It might serve as an alternate approach to an analysis of spatial orientation, depth perception, movement, and other problems as discussed by Wohlwill (1960). It might also extend

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Contributions from a Functional Analysis to Piaget’s suggestions about thought processes in the young child (Kessen and Kuhlman, 1962). By the same token, it can be employed to discover the detailed ways in which complex motor responses are shaped, such as handwriting.

111. Some Methodological Problems in the Analysis of Social Reinforcement W e turn now to an investigation of child development and behavior focusing mainly upon the stimulus consequences of that behavior, rather than its antecedents . Social reinforcement may be viewed simply as one such problem in the analysis of child behavior through control of its stimulus consequences. In this sense it is one more case of operant analysis through the discovery of important reinforcement contingencies. However, it would be a mistake to overlook a broader role that social reinforcement plays in modern child psychology. It is becoming increasingly common to find much of socialization and personality development equated with social reinforcement processes (cf. Bijou and Baer, 1961; Bandura and Walters, 1963), and it is not impossible to find inquiries into the role of social reinforcement in intellectual development (e.g., Zigler and de Labry, 1962). In either case the topic takes on considerable importance. However, a functional analysis of social reinforcement may take on somewhat more urgency in the second case, that is, when social reinforcers are looked upon as critically important stimuli in much of the development of children. Part of this urgency stems from the already inconsistent and contradictory literature in this area. Another part stems from an apparent insistence on discovering the few “laws” of social reinforcement which presumably exist parallel to the laws of primary reinforcement. The common textbook approach to learning, as studied in any convenient laboratory organism with such universal reinforcers as food, water, or shock, typically is organized in terms of “laws of learning”: principles describing the effects of different numbers of reinforced responses, time between responses, time between response and reinforcement, hours of deprivation, schedules of reinforcement, etc. Such an approach may be appropriate where similar results accrue from almost any organism, since a universally effective reinforcer is used on an organism sensitive to it. In the analysis of social reinforcement, however, similar conditions do not hold. Social reinforcers tend to be different stimuli for different children-approval is a positive reinforcer for one child, a negative reinforcer for a second, indistinguishable from any form of attention for a third, and a neutral stimulus for a fourth. The second child may respond to disapproval as a positive reinforcer; the third child may respond to attention, approval, disapproval, affection, anger, or

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Sidney W . Bijozr and Donald M . Baer reflection of feelings as equally effective positive reinforcers; the fourth child may respond to no social stimuli as functional. Hence, whereas almost any pigeon will shape up for food, by no means will almost any child shape up for “Good,” “Fine,” or “Uh huh.” Similarly, food may be dispensed to a rat in solid or mash form from any convenient mechanical device, with very similar results in most cases. But the dispenser of social reinforcers to the child may completely determine the function of the stimulus. For a given child, approval may usually be a positive reinforcer when given by males, but a neutral stimulus when given by females. Indeed, we may discover a child for whom approval is a positive reinforcer when dispensed by the child’s father, 14 other males (4 adults, 10 boys), and his mother; from all other persons except his grandmother it is a neutral stimulus, and from his grandmother it is a negative reinforcer. And again, food may be referred to as a reinforcer for deprived animals, with little loss of accuracy in the failure to specify the precise nature of the foods (Ralston vs. Carnation, wet vs. dry, chow vs. milk powder). But to attempt to speak of approval as a social reinforcer in the same way often will involve grave inaccuracy. For example, we may readily find one child for whom “Good” is a much more effective reinforcer than “Right,” and another for whom the reverse is true (Zigler, 1963). Some children highly sensitive to verbal tokens of approval as positive reinforcers nevertheless may respond to smiles or nods as neutral stimuli. And no doubt children can be found for whom “Very good” is a positive reinforcer, unless delivered in a sarcastic tone of voice, whereupon it functions as a negative reinforcer. Hence a meaningful analysis of social reinforcers will often require a precise physical description of many of the stimuli involved and a separate investigation into the reinforcing function of each. In general, terms like attention, approval, and affection have little function other than as vague labels for possible classes of stimuli, each stimulus requiring its own validation as a social reinforcer. These possibilities do not imply a hopeless chaos of detail before a meaningful principle of social reinforcement can be stated; rather, they reffect the basically simple principle of secondary reinforcement. Social reinforcers are assumed to be a special class of secondary reinforcers, which gain their reinforcing function through their status as stimuli discriminative for other reinforcers. The child represents a case in which many of the nonsocial reinforcers effective for him have long been supplied to him by his caretakers. In his earliest days of life he was largely helpless to secure his own food, water, temperature adjustments, rescue from pain, etc., and it was the caretaker who performed the bulk of these reinforcement operations. With increasing development the child becomes capable of manipulating many more of his reinforcers, yet the caretaker still maintains a considerable role in performing these operations, partly because of precedent perhaps, and partly because of cultural practices. Hence, many of the consistent collateral behaviors engaged in by the

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Contributions from a Function61 AnalysiJ caretaker on these reinforcement occasions constitute stimuli to the child which are discriminative for the reinforcers the caretaker manipulates. As these stimuli gain discriminative function, they gain reinforcing function. Thus there comes into existence a class of social reinforcers whose physical makeup may be as variable as the stimuli which caretakers can provide on reinforcement occasions. Some caretakers may speak to their children on these occasions, others may smile, others may do both, and still others neither. Some may provide hugs and kisses; some may not. Some may use specific words of endearment; some may prattle; some may use standard adult vocabulary. Whatever stimuli the caretaker may consistently provide as discriminative for reinforcement, these are the stimuli that later should prove effective as social reinforcers. The effectiveness of these stimuli as reinforcers may well prove a function of the kinds of environment within which they had discriminative function in the child’s prior experience: in environments similar to those earlier ones, the stimuli may function powerfully as reinforcers; in dissimilar environments their reinforcing function may be much less. Thus, the principle of secondary reinforcement involved in social reinforcement implies a wealth of possible detail, reflecting the wealth of detail implicit in the behavior of caretakers. Yet there may well prove to be some useful organizing dimensions of stimuli within this detail. These may arise from certain inevitable or highly likely patterns of caretaker behavior on reinforcement occasions. Some attempt at analysis of these possibilities has been made before (Baer, 1961) and has relevance here: Examining the normal histories of caretaking suggests several basic classes of social stimuli which will subsequently serve as social reinforcers: (1) Nearness of the caretaker. Many of the reinforcers the caretaker mediates for the infant cannot be manipulated at a distance from the child. It requires a 12eur caretaker to supply food and water, adjust temperature through blankets, sweaters, etc., rescue the baby from sharp, hard, or heavy objects, hand him a toy, etc. Hence nearness of a person often is discriminative for the production of positive reinforcers and/or the removal of negative reinforcers. ( 2 ) Attention of the caretaker. Even when the caretaker is near, she must be attentive to the baby in order to provide or remove many reinforcers. The physical makeup of attention would include the angle of the face, the position of the eyes, a frequent stillness or fixity of the caretaker while attending, and possibly certain verbal behaviors (“What’s wrong ?” and “Hi Baby”). These and other stimuli may be categorized as attention, and often they are even more clearly discriminative for reinforcement from the caretaker than simply her nearness. However, as children grow older, attention may undergo a new history as discriminative for rein-

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’

forcement. In the early months of life it would seem inevitable that a baby who survives would have been attended to often enough on reinforcement occasions for attention to be established as a positive social reinforcer. But in the later years a child growing up under stern discipline may find that attention from adults is more often discriminative for punishment than for positive reinforcement. Hence there exists the possibility for a conflictual history concerning attention for some children, one outcome of which may be that attention is more strongly established as discriminative for punishment (and hence is a negative social reinforcer) than as a positive social reinforcer. Some children very likely will live in an environment in which not all attention is discriminative for punishment, but rather a specific form of attention: disapproval. Disapproval would often consist of characteristic facial expressions such as frowns, angry tones of voice, and specific words such as “Bad,” “Shame,” etc. Hence it is disapproval which should function as a negative social reinforcer, while other forms of attention may remain positive in their reinforcer function. ( 3 ) Warmth of the caretaker (Affection), Many caretakers are especially “noisy” on caretaking occasions. They smile especially often on these occasions, speak, coo, sing, and gurgle especially often, and pet the baby. Hence a complex of facial, vocal, and tactual stimulation often is very consistently discriminative for reinforcement. On the other hand, no doubt there could be found caretakers who show little or none of this extra stimulation on caretaking occasions (the “cool,” “rejecting,” or “casual” mother). Hence, for some children the warmth or affection of the caretaker may subsequently be found to be a powerful social reinforcer, while for others such stimuli may have little or no reinforcing value. As the child grows older, affection often is gradually reduced and refined into stimulus displays which are milder and culturally more appropriate: approval.

Thus far two lines of argument have been advanced: one emphasizing the possible variation between children in their responsiveness to a wide variety of social stimuli, the other suggesting that within this range of variation there may exist useful descriptive stimulus dimensions (such as nearness, attention, affection, and approval) which may organize preliminary research efforts. If both arguments are attended to at once, two alternative lines of research suggest themselves. One of these would involve constructing standard experimental situations within which children could be presented with a given social reinforcer in an experimental manner. Groups of children could be studied in these standard situations, noting the effect of the social reinforcer on the mean behavior of

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Contributions f r o m a Functional Analysis the group. The variable effectiveness of the social reinforcer on individual children within the group would be ignored for the purpose of making a general statement about the effects of that reinforcer in the average case. Recognition of the variable effectiveness of social reinforcers might be reflected in a variety of ways. One way, for example, would be to alter systematically the particular reinforcer used for separate groups, or the setting conditions within which each group operated, or to identify subgroups of children for whom different reinforcers have similar or different effectiveness, as in the illuminating work of Zigler and his associates (1958; 1962), Parton (1962; 1963), or Levin and Simmons (1962). The result of such studies can be the highly useful picture of typical cultural patterns of effectiveness of some standard social reinforcers used in the culture. Working from this base, the researcher may pursue further questions, such as the effect of social reinforcers from a person on the probability that children will imitate that person (e.g., Bandura and Huston, 1961; Rosenblith, 1961); or the effect of isolation of children from all social stimuli on the effectiveness of a social reinforcer like approval (Gewirtz and Baer, 1958). The answers produced are again average answers, and are very much a function of the sampling procedures used. The other approach would concentrate upon an individual child, and by successive experimental analyses arrive at a knowledge of the precise stimuli which are effective social reinforcers for him. In this case there would be no attempt to construct a single, unvarying stimulus condition to which the child would be exposed, behave or not. Instead, stimuli would be tried in successive modifications, until control of the child’s behavior resulted. Further modifications which both enhanced and decreased this control would then be pursued, until a catalog of precisely described social stimuli, each with its corresponding effectiveness as a positive or negative social reinforcer for the child under study, was produced. For example: With a given child, approval might be most effective in the form of “Right!,” less effective as “Good!,” still less effective as a nod, and of zero value in the form of a smile. For another child it might be found that the most potent form of attention was a steady visual regard of the child. Still another child might be most responsive to a steady stream of conversation directed at him; another might be better reinforced by a silent audience while he talked. And some children would respond to attention as a negative reinforcer-but some of these might well respond only to silent attention or an attentive series of prompting questions as negative, while receiving an ongoing stream of conversation, or a story, as a positive reinforcer. What emerges from such analyses is not an average picture of cultural patterns of social reinforcement, but rather an individual picture of each child’s sensitivity to any such practices operating on him. When this picture is comprehensive, it gives a good description of the child’s personality “dynamics,” and

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Sidney W .Bijou and Donald M. Baer strong suggestions about the reinforcement history responsible for his present characteristics. Significantly, it thereby describes those stimuli which often are the most practical to use in an effort to change any of those personality dynamics, through the production of a new social-reinforcement history.

IV. Laboratory-Experimental Studies of Social Reinforcement The research to be described here was undertaken in this spirit. It attempts to create situations within which some degree of flexibility is implicit, such that each child may be investigated in that setting in whatever detail his behavior makes necessary. Thus the primary emphasis in this approach is to maintain tight but readily changeable control of the stimuli to be used as social reinforcers. This criterion is a difficult one to maintain when working with social stimuli. If the definition of a social stimulus is that it results from the behavior of people, then clearly a person would seem to be the appropriate dispenser of social reinforcers. But a person is a difficult dispenser to bring under tight experimental control: he is himself sensitive to the behavior of the child with whom he interacts, and may respond to various acts of the child in ways which provide (or remove) extraneous or incorrect social reinforcers. A nod, a smile (even a smile suppressed at the expense of quivering lips), lifted eyebrows, sudden glances-any or all of these (and other) reactions of the experimenter may serve to reinforce the child, and ruin a critical experimental contingency. There are at least two ways to handle this difficulty. One is to train the experimenter to respond to the child only according to experimental specifications. (This in itself constitutes an experimental study of social reinforcement, in which someone must determine the effective positive and negative social reinforcers to apply to the experimenter, and shape him to criterion performance.) A second method is to create a more readily controllable source of social reinforcers. Examples of both approaches will be described, the latter first. In 1956 Robert Burns devised an animated pair of dolls, one of which could be made to hit the other with a stick when an electrical circuit was completed. Burns created a simple lever-pressing contingency: a response to the lever produced immediate action from the dolls. He presented this to a number of samples of young children and found several things: that the sight of one doll striking the other was a positive reinforcer for many of the children; that to see one doll strike the other was more reinforcing for most children than to see one doll wave his stick in the same way but completely miss the

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Contributions frow a Functional Analysis other doll (which had been moved to the other side of the dolls’ enclosure) ; and that children with siblings generally found this more of a reinforcer than did singletons (Burns, 1956). This study, of course, is not an example of the individual analysis of a child’s sensitivity to the sight of aggression as a reinforcer-but the device represented a method of showing children a realistic facsimile of a social stimulus event. Furthermore, the device, being mechanical, performed in virtually the same way every time and could be depended upon to function in almost any experimental contingency exactly as the experiment required. It has presaged a number of experimental attempts to create symbolic representations of social stimuli for experimental work with children. These attempts have in common the sacrifice of reality of stimuli to the ability to control somewhat different stimuli precisely. Parton (1962; 1963), for example, greatly elaborated Burns’s aggressive dolls so that they could not only strike each other but one could be knocked down by the other. Only one doll was directly controlled by the child; the other was considered his “opponent.” Parton gives this description of his apparatus : The boxing dolls are nine inches tall and incorporate components from the Matte1 Toy Corporation’s “Ken” doll. The handle protruding from below the Plexiglass case served to move the S’s doll sideways through an arc of 45 degrees, and toward and away from the opponent doll over an excursion of 5 in. The stationary opponent doll pivots so that it is always facing the S’s doll. The top of the handle is 34 inches from the floor, and the tops of the dolls’ heads are 44 inches from the floor. A squeeze of the trigger located within the handle closed a 6 volt DC circuit to a relay, which in turn actuated a Hunter timer. The timer, wired for instantaneous contact, delivered a .35 sec impulse to a 6 volt D C solenoid within the S’s doll, causing the right arm of the dolls to swing up and hit the opponent doll in the chest. Gravity returned the arm immediately to its original position. Hits can be delivered to the S’s doll by the opponent doll on a variable interval schedule via a Gerbrands tape programer and a separate Hunter timer. Each doll can be knocked down, the doll moving backward from the vertical position to a position approximately 40 degrees from the horizontal. This action is controlled manually by the E via flexible cables (1962). Lovaas (1963) has animated dolls, each of In one setup, an adult a bar-pressing response

exemplified the same idea in devising a number of which portrays symbolically a different social reinforcer. doll turns to look at a child doll, as a consequence of by the child. This action attempts to simulate attention.

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Sidney W . Bijotc and Donald M . Baer Another set up contains an adult doll which can turn to and kiss a child doll, thereby exemplifying attention and affection. The number of social stimulus events which dolls can readily be made to portray are very numerous. In a laboratory containing a number of such devices, a child’s rate of bar-pressing on each could be collected over long and repeated sessions, and thereby a catalog of the relative strength of a number of such social reinforcers could be constructed, Baer (1962) has followed a very similar methodological line by constructing an animated puppet capable of portraying a number of social stimuli within one situation. The puppet is described as follows: The apparatus is a cowboy puppet seated in a chair on a puppet stage. [This is pictured in Fig. 5 . ) The puppet (manufactured by the Hazelle Company, Kansas City) has articulated arm, leg, and neck joints and a movable jaw which allows a reasonably realistic portrayal of speech when the experimenter’s voice is piped through the puppet, The string operating the jaw is connected to a concealed electric motor which is operated by the experimenter ( E ) . The puppet’s right hand rests upon a miniature barpressing apparatus placed on a small table beside the puppet’s chair. This bar-pressing apparatus is a close replica of the child’s bar which is located near the child’s right hand. A solenoid concealed within the puppet stage is connected to the puppet’s bar by a string, such that the bar may be depressed remotely by E at any time. Since the puppet’s right hand rests freely upon the bar, he appears to be pressing it. The puppet’s head, unless held up by its strings, rests with chin on chest, such that he seems to be looking into his lap. A second concealed motor is connected to the head strings, and at E’s option can lift the head into a position in which the puppet is looking directly at the child seated before him. Neither the left arm nor the [right) leg is connected to any motor or solenoid; these limbs simply rest in place. (The left leg can stamp up and down when operated by a solenoid below the floor.) On the ceiling of the stage is a small 7t-watt white light bulb. This may be used as a cue for various events of the experimental design. Otherwise it can be on to serve as a soft light source for the puppet stage. High on the puppet’s right is a microphone which connects to E‘s earphones and to a tape recorder. This microphone picks up both the puppet’s and the child’s speech. Also on the puppet’s right, but inside the stage, is a chute and tray for delivering trinkets and other small reinforcers to the child. The tray can be seen in Fig. (51 projecting out from the stage. The dispenser which produces these material reinforcers is concealed in the upper part of the puppet stage.

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Contributions from a Functional Analysis A 4-in. loudspeaker is mounted on the back of the puppet’s chair, completely out of the child’s sight. The puppet’s voice (i.e., E’s voice) comes to the child from this speaker while the jaw is worked in synchronization by E. The puppet is designed to achieve two basic goals: (1) relatively great control and standardization of the social stimuli it is to exemplify, and ( 2 ) some flexibility in displaying a number of such stimuli, within a single

Fig. 5 . A child interacting with an animated, talking puppet.

situation. Obviously part of the first goal is achieved simply by the use of a mechanical device with its accompanying reliability and standardization of performance. Probably the greatest deviation from this is the use of the experimenter’s voice, spoken through the puppet via a loudspeaker. However, if standardization of verbal stimuli from the puppet is desired, the verbalizations may be taped and played back through the puppet on each experimental occasion (e.g., Larder, 1962). Accomplishment of the second goal, the flexible portrayal of a number of social stimuli within a single experimental situation, has at least been approached. The puppet is capable of actions which

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Sidney W .Bijou and Donald M . Baer suggest the label of attention: he can lift his head (thus ”looking” at the child seated before him) and speak or “listen,” and can cease these actions at any moment. By speaking he can dispense verbal forms of approval, disapproval, affection, commands, requests, etc. A basic preliminary question involved in the use of all such techniques is the nature of the stimulus used. Granted that some doll or puppet action exemplifies a social stimulus to the experimenter-but does the child subject respond to it as a social stimulus? Any moving device is likely to have some reinforcing value for a child who can operate it; clearly these devices include such effects. To determine whether they affect the child in any more specific and eminently social manner, it is necessary to examine the relationship between the child’s behavior controlled by these stimuli and other variables. There have been a number of approaches to answering this question. Burns used a control condition in which the aggressive dolls performed the same action with their backs to one another. Hence the action of the dolls was similar in both conditions, but the eminently aggressive element of the stimulus was lacking. There was less behavior to produce such a display, in the average case, than to produce an aggressive display. Furthermore, for the average child, behavior to produce the aggressive display related to sibling status, which Burns considered a sensible relationship if the stimulus was indeed aggressive. ( W e may not agree with him. Nevertheless, a beginning was made in relating the dolls’ stimulus to other variables; a sufficiently complete analysis of this sort should indicate the value of studying such stimuli.) Larder used a somewhat similar technique in collecting rates from children on two animated devices, one portraying this same aggressive action, the other portraying an innocuous motion of a toy dog in and out of a dog house. She pointed out that the ratio of “aggressive” to total responses related to the content of a story the children heard from the puppet, the story being either aggressive or nonaggressive in content. Again, this study represents a beginning at relating such behaviors to other supposedly relevant variables. Parton (1962) and Baer (1962) have correlated children’s behavior to produce such stimuli from dolls or puppets with ratings of supposedly similar behaviors in everyday settings. Parton reported a negative correlation between a child’s behavior in operating the boxing dolls and teachers’ ratings of the child’s “social aggression” in a grade-school setting. Baer, on the other hand, found a positive relationship between children’s behaviors to maintain the puppet’s attention and teachers’ ratings of their attention-seeking in a nurseryschool setting. Such discrepencies may arise from a number of causes. It may be, for example, that social aggression in school is maintained not by its aggressive concomitants (pain or damage to others) but by other stimulus consequences: the frequent removal of the person struck from the local environment, or the

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Contributions from a Functional Analysis attention typically secured by aggressive acts, or, in some circumstances, the approval, or sometimes, disapproval produced. All of these may act as positive reinforcers for some children in some conditions. After all, a response with an “aggressive” topography can be readily shaped with almost any reinforcer otherwise unrelated to aggression (e.g., Bandura and Walters, 1963). Clearly, this argument may be generalized to a discussion of other responses as well as aggressive ones. O n the other hand, it may be that symbolic representations of social stimuli, whatever advantages they may secure in terms of experimental control, nevertheless have too little functional resemblance to the real-life social stimuli they are intended to portray. This possibility obviously should not be forgotten in future research along these lines. Baer (1962) has collected some data which indicate that the animated puppet can indeed produce behavior from children in laboratory settings which reflects rather well their behavior in normal settings. By using his attention, defined simply as the raising of his head and either talking to the child (if the child was silent) or listening to the child (if the child was talking) as a consequence of bar-pressing, a picture of each child’s sensitivity to the puppet’s attention as a reinforcer was secured. This is shown in Fig. 6. In this figure, responses to produce the puppet’s attention, or to avoid its future withdrawal, are recorded cumulatively as a rising curve against time. Withdrawals of attention are shown as short downward displacements of the response line. Each response produced 3 sec of attention, or, if the puppet was already attentive, added 3 sec more against the time when the attention would be withdrawn. The 5 subjects shown in Fig. 6 were selected “as displaying a wide range of attention-seeking behavior in the nursery-school setting. The first subject (51, a boy) was described as constantly seeking attention, whether approving or disapproving, becoming very excited when getting it. $2 (a girl) was described as seeking approving or disapproving attention almost as constantly, but showing less excitement about it. S3 (a boy) was described as ‘just average.’ 34 (a boy) was said to seek attention rarely, and only when it was combined with approval. 55 (a girl) was labeled as very shy, typically avoiding attention whether it was mixed with approval or not” (1962, p. 851). With such subjects, deliberately chosen to represent well-spaced points on a continuum of attention-seeking in everyday environments, a very clear correlation between real-life and symbolic attention-seeking is apparent. (In a larger sample of children, not so selected, a similar correlation was about +.7, depending somewhat on how the child’s performance in the laboratory setting was quantified.) A further analysis of the stimuli involved in “attention” was accomplished with a few children known as attention-seekers in the nursery school. Some of these children were said to be very bold and forthright in behaviors considered to be supported mainly by attention: persistent talking, interrupting,

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Sidney W. Bijou and DoPzald M. Baer

Pig. 6 . The behavior of 5 subjects t o produce and maintain attenlion from a puppet.

shouting, fighting, etc. Others were thought to be quite positively receptive to attention, but too shy to seek it in other than a few ways. One child of each type was studied as follows: After a number of preliminary sessions in which the child had developed a fairly stable rate of bar-pressing to maintain the puppet’s attention, an alternating series of conditions was instituted. In one condition, the puppet was attentive simply by listening, head up and looking at the child. If the child did not speak, the puppet “prompted” him with insistent questions. In the other condition, the puppet was attentive by talking (head up, etc.); in fact, the puppet talked steadily, interrupting and overriding the child if he

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Contributions from a Functional Analysis attempted to speak. Each condition lasted about 3 min, with as many conditions being alternated within a session as the child was willing to remain for. The bold child showed a strong rate of bar-pressing to maintain the puppet’s attention during the puppet’s “listening” periods, but a much decreased rate of bar-pressing during the puppet’s “talking” periods. The shy child showed a reverse pattern: a steady rate of bar-pressing to maintain the puppet’s attention only during his “talking” periods, and an abrupt decrease in rate during his “listening” (and prompting) periods. Typical excerpts from their records are shown in Fig. 7. Note that the shy child often fails to respond and thus restore the puppet’s attention during his “listening” periods. (This is shown by the continuing downward displacement of the response line.) I

I

4 “SHY” CHILD

listens

talks

PUPPET

listens

talks

Fig. 7. The behavior of 2 children to produce and maintain 2 different forms attention from a puppet.

of

Thus it would seem that attention is a very broad term when used as a label for a social reinforcer. Depending upon whether the child must respond to it in its discriminative function, or may remain silent and listen, it may serve as either a negative or a positive reinforcer, for the same child. In another child the reverse pattern may be true. Surely this represents only a beginning at analyzing the ways in which the various forms of attention may affect the behavior of different children. Another example was afforded by S5 of Fig. 6. The child was known in the nursery school as extremely shy and more likely to avoid attention than to seek it. Her performance in the experimental situation showed that rather than producing and maintaining the attention of the puppet, she was more likely not to respond, thus removing his attention. However, when the puppet, through conversation, made it clear that he could give her trinkets (from the material-reinforcer dispenser built into the puppet stage), but could do this only while they were talking (Le., while he was attentive to the girl by talking

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Sidney W . Bijotl and Donald M. Baer to her), then a very regular rate of bar-pressing by the girl developed. That is to say, as long as the puppet’s attention was discriminative for other, more powerful reinforcers, it was itself reinforcing enough to maintain her barpressing behavior. When the puppet announced that the girl had received enough trinkets, she then ceased responding to maintain his attention. (Trinkets were never given as consequences of bar-pressing, but only at moments when the girl was not responding and the puppet was attentive.) In still another example, the relative reinforcing values of two social stimuli, attention and approval, were established, and one of them altered relative to the other. Attention consisted of the puppet’s raising his head and talking to

SUBSEQUENT R A T E FOR APPROVAL

Fig. 8. The behavior of a child t o produce approval f r o m a puppet, before and a f f e r an approval-strengfhening procedure.

the child. This attention was produced for 5 sec following every bar-press, but unlike the previously described situations, responding while the puppet was attentive did not further contribute to the time remaining before the attention would be withdrawn. Approval consisted merely of the spoken word “Good,” delivered in an enthusiastic tone. Alternating 5-min conditions of the contingent use of attention and approval were presented to the child. During “attention” conditions every bar-press produced 5 sec of attention (unless the puppet was already attentive). During the “approval” conditions every barpress produced the word “Good” from the puppet, who remained constantly attentive during the condition. These procedures were repeated for several sessions until stable behavior developed. A typical portion of the record from a late session is seen in Fig. 8. It is clear that when attention is delivered contingent upon responding, a relatively high rate develops. Approval, by contrast, had minimal reinforcing effectiveness, supporting only a sporadic rate of responding. (It will be noted that during “approval” conditions the child had the puppet’s undivided and steady attention. Hence the approval

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Contributions from a Functional Analysis dispensed-“Good”does not represent a contingent use of both approval and attention.) There then followed several sessions during which the puppet attempted to increase the reinforcing value of attention. He did this by holding a conversation with the child (no bar-pressing was required to maintain his attention). During the conversation he would at random moments say “Good” and immediately deliver a trinket to the child. Trinkets were known to be powerful reinforcers for this child from previous work; now the word “Good” from the puppet was becoming discriminative for their presentation. Some forty trinkets were delivered to the child, at first one trinket for every “Good,” then one trinket for every other “Good,” then one for every third “Good,” and finally one for every fifth “Good.” Following these sessions, part of the procedure of earlier sessions was repeated: the puppet again attempted to strengthen a bar-pressing response in the child by reinforcing it with “Good” during the course of the conversation. Figure 8 shows the rate of bar-pressing established by approval subsequent to this reinforcer-strengthening procedure. It is clear that for a little time, approval greatly increased in its reinforcing effectiveness for this child. It is also clear that this effectiveness diminished over the session, as approval was used repeatedly but was not discriminative for further trinkets. This demonstration shows the relative ease of temporarily altering the value of a social stimulus simply by altering its current discriminative function. In this sense it is similar to the preceding example. It may also be considered as a model of the process whereby social reinforcers are established. [A more thorough and elaborate investigation of much the same process has been performed by Steinman (1963), using both social and material reinforcers.) Baer and Sherman (1963) have made use of the puppet to provide both reinforcing and discriminative stimuli of a social kind. In this study the puppet performed 4 different responses-nodding, mouthing, saying verbal nonsense statements, and bar-pressing-and repeatedly reinforced the child with approval for imitating him in the first 3 of them. Meanwhile the puppet maintained his own bar-pressing rate, sometimes at slow and sometimes at fast rates. As the reinforced imitations grew in strength, imitative bar-pressing also grew, although it was never reinforced. When reinforcement of the other imitative responses was no longer reinforced, imitative barpressing was the first response to weaken, but recovered in strength when the other 3 imitative responses were again reinforced. When the puppet ceased performing the first 3 acts for the child to imitate but kept up bar-pressing, the child’s imitative bar-pressing weakened. When the puppet resumed the first 3 imitative responses (and hence reinforcement of them) the child’s imitative bar-pressing again increased in strength. This imitative bar-pressing, since it was never reinforced, represents a generalization of the child’s behavior. Since the 4 responses involved-

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Sidney W.Bijou and Donald M. Baer nodding, mouthing, verbal nonsense statements, and bar-pressing-have little topography in common, but are alike in that all are imitative of corresponding actions by the puppet, it would seem that the generalization takes place along a stimulus dimension of similarity of behavior between child and puppet. This would seem to be a model of an eminently social relationship between child and puppet.

V. Field-Experimental Studies of Social Reinforcement W e consider now a new program of research and analysis of social reinforcement processes, this time in the real-life situation of the nursery school. Despite the lack of tight control available within the child’s actual playrooms and yards, illuminating relationships often enough can be established there, using the most realistic version of social reinforcers: the behavior of people. This research stems from the most basic postulate of reinforcement theory: that to control the consequences of behavior is to control the behavior. If this postulate is applied to the free behavior of children in the nurseryschool playrooms and yards, it requires an analysis of the stimulus consequences of behavior in that setting. Straightforward observation suggests immediately that two classes of stimulus consequences are very prominent in that environment: social stimulation (1) from the teachers and (2) from the other children. Given a staff who are aware of the implications of reinforcement theory and open to an experimental approach to their work, it is possible to attempt an experimental analysis of this postulate by controlling the stimulus consequences the teachers provide.3 Clearly, the child’s peers also provide very important social reinforcers, but these are difficult to control. It can be valuable to show how much of the child’s behavior can be controlled by the teachers’ reinforcers alone. The program consists of two basic processes: observation of the current reinforcement contingencies under which each child exists at the school, and experimental manipulation of those contingencies involving stimuli supplied by the teachers. The processes are applied to specific children in the following manner: First, a child is chosen for study who has some prominent behavior “problem” of concern to his parents and the staff, such as excessive crawling, crying, whining, or aggression, or too little social play with other children. ‘This research i s being carried out at the Institute of Child Development’s Nursery School, University of Washington, in collaboration with, and often under the initiative of, Florence Harris, Director; Eileen Allen, Margaret Johnston, Joan Buell, Elizabeth Hart, Susan Kelley, and James A. Sherman. Montrose M. Wolf has served as a continuing consultant to this project, suggesting many of the designs and procedures.

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Contributions from a Functional Analysis This behavior is observed in its natural contingencies. An observer is assigned to the child for his entire morning at school, day after day. The observer notes all instances of the behavior under study, recording its rate of occurrence, duration, intensity, or any combination of these judged suitable. Furthermore, as each instance occurs, the observer notes the stimulus situation in which it occurred and the stimulus consequences of the behavior. Special note is taken of those consequences produced by the teachers, such as attention, approval, disapproval, affection, support, encouragement, consolation, reflection of feeling, etc. This observation is pursued until a stable picture of the strength of the response and a consistent picture of its usual contingencies is produced. Very often it is found that the undesirable behavior consistently produces consequences from the teachers. Most commonly, the behavior produces attention, quite often in the form of support, encouragement of other (desirable) behaviors, reflection of the supposed feelings of the child (anger, inadequacy, etc.) , or simple affection; infrequently, it produces disapproval. At this point experimental manipulation of these contingencies is attempted. The question is posed: Are the consistent stimulus consequences of this response, supplied by the teachers, acting as social reinforcers and actually strengthening and maintaining the response ? To produce an experimental answer, the contingencies are changed. The teachers agree that no longer shall the behavior have its usual consequences from them. They may also agree, when appropriate, that another behavior shall receive these consequences instead. This program is put into effect, and the child’s behavior observed under the new contingencies. These new contingencies consist of extinction of the undesirable behavior, possibly coupled with reinforcement of a different (desirable) behavior. Given a stable change in the child’s behavior of the desired type (i.e., weakening of the undesirable behavior), a new manipulation is used. This consists of reinstating the former, “natural” contingencies, to see if the behavior will return to and stabilize at its previous strength. If this occurs, it demonstrates beyond reasonable possibility of coincidence that the undesirable behavior is indeed under the control of the social reinforcers supplied by the teachers. At this point the new contingencies are reinstated, and the undesirable behavior again weakened as much as possible. The intense program of reinforcement for the new, desirable behavior is then gradually diminished over a period of weeks, until it produces a normal amount of reinforcement in the nursery-school setting. (The undesirable behavior is never again reinforced, to the best of the teachers’ ability.) This program has been applied to a case in which the child crawled rather than walked almost all of every morning. It was observed that the teachers responded to crawling with a great deal of attention and support, with a view toward improving the child’s “security.” When this was stopped, and the reinforcement shifted to the child’s “upright” behavior, the crawling

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Sidney W .Bijotl and Donald M. Baer weakened greatly within a few days and was largely replaced by upright behaviors of standing, walking, running, etc. Reversal of the contingencies to the old pattern reversed this outcome; reinstatement of the new contingencies again produced the new, desirable pattern. The result generalized well to the child’s home environment, where the parents used similar contingencies (demonstrated for them in the nursery school) to maintain the upright behavior. Similar applications have been made to cases of excessive crying, whining, isolation, inattentiveness, dependence on adults, and aggression, usually with quite similar results. It appears true that the simple social stimuli that nursery-school teachers typically use often function as powerful social reinforcers for the behaviors of the children in their school, and serve to strengthen and maintain whatever behaviors produce them with consistency. The fact that these stimuli have often been given to the children in the hope of weakening those very behaviors (by building “security,” for example) thus becomes strikingly significant. The technical problems of such a program are in many ways more difficult than those of laboratory research in social reinforcement processes. It is precisely the lack of control over much of their own behavior that makes it difficult for nursery-school teachers to follow a simple contingency of social reinforcement without deviation. To improve this self-control is itself an impressive program in social reinforcement. The teachers meet daily after school, discussing the day’s procedures, and criticising one another and themselves for failures in following plans. The observers who have noted all of these contingencies, the correct and the faulty, add their own factual disapproval. Days on which no (or very few) errors are made become occasions for extravagant approval for each teacher from the other teachers, observers, and staff. Day-by-day records of the progress of each child (or the lack of it) also serve to reinforce behavior appropriately. The use of a technical vocabulary by all involved is exceedingly helpful in establishing and maintaining the procedure. The stimulus analysis of each child’s case, however, is much the same as in the laboratory examples previously cited. There can be n o reliance upon a few stock stimulus operations. Instead, each child’s case is experimentally analyzed until the specific social stimuli powerful for him are discovered and proven. To extinguish one child’s excessive dependence upon adults, in the form of constant requests for help at any project of the moment, it was necessary to control the attention of the teachers in a very specific way. Rather than completely ignoring the child’s requests (which did not have helpful effects), the teachers dispensed a cheerful “You do it,” *‘I can’t help you,” “You try it,” etc. When the child did attempt something on his own, the teacher assigned to him then approached with

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Contributions from a FnnctionaL AnaLysis attention and approval (not help) as consistently as possible. With success in shaping the independent behavior, the schedule of social reinforcement was thinned out. The behavior maintained its strength. With another child it seemed likely that the most minimal forms of attention could serve to strengthen his undesirable behaviors. Merely mentioning his name to a child hurt by him (“Johnny didn’t mean it”), if heard by him, seemed to reinforce the response. Extinction in this case would mean a complete absence of social stimuli from teachers as consequences of his undesirable behaviors. Such attempts are bound to fail in some cases. The significant social reinforcers may not be the stimuli which the teachers can control; instead, they may be the behavior of the child’s peers. This too can be controlled, in principle, but in practice it is much more difficult. Each peer of the child under study must be shaped in a set of social reinforcement practices for that child, which implies embarking on an extended program. Failing this, there remains the possibility that the teachers sometimes can marshal the other children either to or away from the child under study (“Come see what Johnny is doing” or “All right; everybody but Johnny come over here”). This technique can be effective many times. The frequency with which these simple techniques work, and work powerfully, reinforces the belief that in fact a great deal of the complexity of reallife situations can be analyzed in simple terms. Often only a few basic principles of stimulus and response interaction are involved. It is the discovery of the precise nature of the stimuli and responses which are the details of these simple principles that is the key problem for analysis. The analysis requires extended empirical testing as described above; it can rarely be done merely by inspection or deduction.

VI. Concluding Comments In these two methodological problems-applying experimental methods to an analysis of conceptual development and some processes of social reinforcement-we have attempted to exemplify the principles of functional analysis from what we consider to be a natural science point of view. In essence, these examples of research have focused upon empirical rather than a priori analyses of response and stimulus classes. Those stimulus procedures which in fact have been demonstrated to work in controlling a child’s behavior are considered the significant ones; those responses which in fact covary under such operations have been considered as the classes of behavior under study. These are the procedures and responses that require further study and parametric investigation, and they are defined by the behavior of the subject, not the experimenter. To

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Sidney V.Bijou and Donald M. Baer distinguish one child from another we must be prepared to make changes in these procedures, and to discover that new classes of responses result; there is no guarantee that what is functional for one child must be similarly functional for another. To us, this fact is the most prominent aspect of a scientific study of child development. REFERENCES Baer, D. M. Modes of presenting social reinforcers. Paper read at Amer. Psychol. Ass., New York, Sept. 1961, in symposium on the Conditions and Effects of Social Reinforcement in Children. Baer, D. M. A technique of social reinforcement for the study of child behavior: Behavior avoiding reinforcement withdrawal, Child Develpm., 1962, 33, 847-858. Baer, D. M., & Sherman, J, A. Reinforcement control of generalized imitation in young children. Paper read at Society for Research in Child Development, Berkeley, Calif., April, 1963. (In press, J. exp. Child Psychol., 1964.) Bandura, A,, & Huston, A. C. Identification as a process of incidental learning. J . abnorm. SOL. Psychol., 1961, 63, 311-318. Bandura, A., & Walters, R. H. Social learning and personality development, New York: Holt, Rinehart, & Winston, 1963. Beach, F. A. The descent of instinct. Psychol. Rev., 1955,62,401-410. Bijou, S. W., & Baer, D. M. The laboratory-experimental study of child behavior. In P. H. Mussen (Ed.), Handbook of research methods in child development. New York: Wiley, 1960. Bijou, S. W., & Baer, D. M. Child development: a systematic and empirical theory. New York, Appleton-Century-Crofts, 1961. Blau, T. H., & Blau, L. R. The sucking reflex: the effects of long feeding vs. short feeding on the behavior of a human infant. J. abnorm. roc. Psychol., 1955, 51, 123-125. Burns, R. Unpublished research, Univer. of Washington, 1956. Cohen, D. J. Justin and his peers: An experimental analysis of the child’s social world. Child Develpm., 1962,33, 697-717. Crowell, D. H., Peterson, J., & Safely, M. A. An apparatus for infant conditioning research. Child. Develpm., 1960,31, 47-51. Dennis, W. Infant development under conditions of restricted practice and of minimum social stimulation. Genet. Psychol. Monogr., 1941,23, 143-189. Gesell, A,, & Thompson, H. Learning and growth in identical infant twins. Genet. Psychol. Monogr., 1929, 6, 1-124. Gewirtz, J. L., & Baer, D. M. The effect of brief social deprivation on behaviors for a social reinforcer. J. abnorm. sot. Psychol., 1958,56, 49-56. Gilbert, T. F. Fundamental dimensional properties of the operant. Psychol. Rev., 195S, 65, 272-282. Hilgard, J. R. Learning and maturation in preschool children. J. genet. Psychol., 1932, 41, 36-56. Holland, A., & Mathews, J. The use of a teaching machine in training speech sound discrimination for articulation therapy (in prep.). Holland, J. G . Teaching machines: An application of principles from the laboratory. J. exp. Anal. Behav., 1960,3, 215-281.

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Contributions f r o N a Functional Analysis Holland, J. G. New directions in teaching-machine research. In J. Coulson (Ed.), Proceedings of ihe conference on applications of digital computers to automated instruction. New York: Wiley, 1963. Jeffrey, W. E. Variables in early discrimination learning: I. Motor responses in the training of a left-right discrimination. Child Develpm., 1958a, 29, 269-275. Jeffrey, W. E. Variables in early discrimination learning: 11. Mode of response and stimulus difference in the discrimination of tonal frequencies. Chi/d Develpm., 1958b, 29, 531-538. Kessen, W., & Kuhlman, C. (Eds.) Thought in the young child. Monogr. Soc. Rer. Child Develpm., 1962, 27, No. 2. Larder, D. Effect of aggressive story content on nonverbal play behavior. Psychol. Rep., 1962, 11, 14. Levin, G. R., & Simmons, J. J. Response to food and praise by emotionally disturbed boys. Psychol. Rep., 1962, 11, 539-546. Lipsitt, L. P., & DeLucia, C. A. An apparatus for the measurement of specific response and general activity of the human neonate. Amer. J . Psychol., 1960, 73, 630-632. Lovaas, 0. I. Procedures for studying social stimuli. Paper read at Society for Research in Child Development, Berkeley, Calif., April, 1963. McGraw, M. B. Growth: A Study of Johnny and Jimmy. New York: Appleton-Century, 1935. Moore, R., & Goldiamond, I. A fading-in procedure for establishing discriminations in young children. J . exp. Anal. Behav. (In press). Parton, D. An operant device for the measurement of aggression in children. Paper read at Southeastern Psychol. Ass., Louisville, Ky., March, 1962. Parton, D. An experimental approach to the conflict model of aggressive response strength in boys. Paper at Society for Research in Child Development, Berkeley, Calif., April, 1963. Rosenblith, J. F. Imitative color choices in kindergarten children. Child Develpm., 1961, 32, 211-223. Skinner, B. F. Science and human behavior. New York: Macmillan, 1953. Spiker, C. C. Research methods in children’s learning. In P. H. Mussen (Ed.), Handbook of research methods in child development. New York: Wiley, 1960. Steinman, W. Strengthening of verbal approval by discrimination training. Paper read at Western Psychol. Ass., Santa Monica, Calif., April, 1963. Verplanck, W . S. Since learned behavior is innate, and vice versa, what now? Psychol. Rev., 1955, 62, 139-144. Watson, J. B., & Rayner, R. A. Conditioned emotional reactions. J . exp. Psychol., 1920,

3, 1-4. Wohlwill, J. F. Developmental studies of perception. Psychol. Ball., 1960, 57, 249288.

Zigler, E. Social reinforcement, environmental conditions, and the child. Amer. J. Orthopsychiat., 1963 (in press). Zigler, E., & de Labry, J. Concept-switching in middle class, lower class, and retarded children. J . abnorm. SOC. Psychol., 1962, 65, 267-273. Zigler, E., Hodgden, L., & Stevenson, H. The effect of support on the performance of normal and feeble-minded children. J . Pers., 1958, 26, 106-112.

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THE HYPOTHESIS OF STIMULUS INTERACTION AND AN EXPLANATION OF STIMULUS COMPOUNDING

Charles C. Spiker' INSTITUTE OF CHILD BEHAVIOR A N D DEVELOPMENT STATE UNIVERSITY OF IOWA

I. INTRODUCTION

. . . . . . . . . . . . . . . . .

234

. . . . . .

236

11. THE HYPOTHESIS OF STIMULUS INTERACTION.

A. APPLICATION OF STIMULUS INTERACTION TO THE SIMULTANEOUS AND SUCCESSIVE DISCRIMINATION PROBLEMS . 239 B. CONVENIENT EQUATIONS FOR SPECIAL CASES

. . . .

245

111. DEDUCTIONS WITH THE HYPOTHESIS OF STIMULUS INTERACTION . . . . . . . . . . . . . . . . . . . 249 A. STIMULUS SIMILARITY IN THE SIMULTANEOUS AND SUCCESSIVE DISCRIMINATION PROBLEMS . . . . . . . 249 B. CUE-POSITION COMPOUNDING AND DISCRIMINATION PROBLEMS . . . . . . . . . . . . . . .

253

C. THE CONDITIONAL DISCRIMINATION

. . . . . . . .

261

. . . . . . . . . . . . . . . . . .

263

. . . . . . . . . . . . . . . . . .

264

IV. SUMMARY

REFERENCES

'The author is indebted to the many graduate students in his classes who have contributed over several years to a better organization and understanding of the materials contained in this paper. He is particularly indebted to Joan H. Cantor who gave the manuscript a thorough and helpful critical reading.

233

I. Introduction This paper is concerned with the explication of an hypothesis concerning the manner in which generalized and conditioned habits and inhibitory tendencies, established to components, combine to yield the total effective habit of the compound. For convenience, this hypothesis will be called the principle of stimuIus interaction. The principle will be applied to explain certain empirical phenomena that have been referred to as stimulus patterning or stimulus compounding. The stimulus interaction hypothesis is best considered as an extension of the Hull-Spence theory, which is based primarily on the behavior of infrahuman subjects. However, one of the major concerns of the present paper is with applications of the theory to the behavior of children in discrimination problems. Since the hypothesis does not refer to verbal processes, it is unrealistic to expect it to apply without modification to the behavior of children. Nevertheless, the repeated application of such a theory to the discrimination learning of children should provide us with a better indication of just when such verbal processes begin to play a crucial role and when concepts and laws referring to them must be invoked. The hypothesis may be understood more readily after a review of Hull’s use of the principles of afferent neural interaction and primary stimulus generalization in his analysis of stimulus patterning (Hull, 1943, Chapter 19). Hull distinguished between the physical stimulus (S) and the stimulus trace (s), which he referred to as an afferent impulse. The relation between S and s is not always one-to-one. Although the presentation of S, produces s, and the presentation of S, produces f2, the afferent impulses resulting from the simultaneous presentation of S, and S, are said to be 7, and Y,, each of which is different to some degree from its corresponding single presentation impulse. Both s, and J’, are assumed to have values on the same dimension(s) and the magnitude of the difference between them is assumed to be an increasing function of the intensity of S,. If the CS in a conditioning experiment were S,, and if J, had acquired a given habit loading, the habit loading of resulting from the joint presentation of S, and S, would be less than that of J ~ .The reduction in the habit loading was explained by Hull in terms of stimulus generalization. The amount of the reduction in habit is an increasing function of the dissimilarity of 5, and j,, which in turn is an increasing function of the intensity of S,; i.e., the greater the intensity of S2, the greater the difference between J, and ?, the smaller the amount of stimulus generalization, and, therefore, the greater the reduction in habit loading from s, to ?., AnaIogous reasoning applies to the

;,

234

The Hypothesis of Stimulus Interaction converse case in which S, and S, are jointly the CS and either S, or S, is presented alone. Any theory which maintains that the habit of a stimulus compound is determined by the habits of its components must also contain some principle such as neural interaction. Without such a principle, the theory cannot explain how infrahuman subjects can respond differentially to stimulus compounds consisting of exactly the same components. Thus, Hull (1943) used the concept of stimulus trace and the principles of afferent neural interaction and stimulus generalization to explain Pavlov’s demonstration that subjects can learn to discriminate between different temporal patterns (e.g., between a light followed by a bell and a bell followed by a light). The term “compounding” has been used in several different but related ways. It has been used to refer to the empirical fact that organisms do respond differentially to compounds consisting of the same components arranged in different spatial or temporal patterns. The term has also been used to refer to a particular theoretical explanation of the empirical phenomena-viz., that habits are built up to compounds rather than to components. A third usage is a composite of these two : compounding refers to discrimination performance which cannot be explained in terms of a theory that assumes that habits are built up to components und summate in a simple algebraic way. It is in the latter sense that the term is used in this paper. According to this usage, the so-called successive discrimination learning problem involves compounding, since the subject learns to make differential responses to the different cueposition compounds despite the fact that there is no differential reinforcement of either cue or positional components. Spence (1952) accepted the occurrence of compounding as a primary phenomenon in his own theoretical framework, but he noted that Hull would probably have attempted an explanation in terms of afferent neural interaction. Clearly, it would be more parsimonious if stimulus compounding were explained satisfactorily by laws found useful in non-compounding situations. Unfortunately, the afferent neural interaction principle is not given in sufficient detail to encourage systematic application of it. For example, Hull did not specify criteria to determine when a component in a new compound is “different” from one in the conditioned stimulus compound. If the CS is a black circle and the test stimulus is a black oval, how much may the oval deviate from circularity before it becomes a “different” component? The afferent neural interaction principle does not appear to have stimulated much research, and it has not been systematically applied in explaining relevant phenomena. This has probably been partly the result of the inherent complexity of the phenomena to which the principle pertains, but it is equally likely that the form in which Hull proposed it does not lend itself directly and easily

235

Charles C. Spiker to empirical applications. The physiological terminology in which the principle is couched has undoubtedly led many psychologists to avoid its serious consideration as an explanation of empirical results. It is quite likely that Hull recognized the principle as a skeleton which would require further elaboration to be more than a promissory note. The present thesis is that a more satisfactory formulation can be obtained by specifying a rule for combining the conditioned and generalized habits and inhibitory tendencies of components in inultidimensional stimuli. To avoid confusion of this principle with afferent neural interaction, it is here designated as the hypothesis of stimulus interaction.

11. The Hypothesis of Stimulus Interaction A preliminary statement of the hypothesis can be formulated in the following way: if a stimulus component has acquired a specific habit (or inhibitory) loading, as the result of having been presented as a member of a reinforced (or nonreinforced) stimulus compound, its contribution to the loading of a new compound will be less if the new compound contains components different from those in the original compound. The amount of the reduction in the contribution of the component will be an increasing function of the average dissimilarity between corresponding components in the two compounds. The hypothesis may also be given a tentative mathematical statement. The reader will recall that Hull (1943) postulated the principle of primary stimulus generalization in the following way:

R= HX

lo-&

(1)

where R is the amount of generalized habit, H is the amount of habit directly conditioned to the CS, u is an empirically-determined parameter, and d is the difference in j.n.d. (just noticeable difference) units between the conditioned stimulus and the test stimulus with respect to a single dimension. The generalization between two stimuli is somewhat more complex in the case of multidimensional stimuli. Let S, be a CS consisting of two or more components, S,, S,, S, . . S,. Let Si represent a second compound consisting of the same number of components, S,’, Sg’, . . . Sit,. . . Sn’,where S, and S,’have different values on one dimension, S, and S2’ have different values on a second dimension, etc. Our concern is with the generalization from S,; to Si. Let dilk represent the magnitude by which S, and S,’ differ; dizk, the magnitude by which S, and S,‘ differ; d i j k , the magnitude by which S, and Sj’ differ, etc. The habit loading of S, may be represented by Hklk, that of S, as Hknk,etc. The (generalized) habit loading of S,’ is represented as HJlk,the (generalized)

...

236

.

The Hypothesis of Stimulus Interaction habit loading of S,' is HiZk,etc. I n this notational system, the first subscript designates the compound, the habit of which is under consideration; the second, the dimension under consideration; and the third, the compound which is the source of the habit or inhibition. When the first and third subscripts are identical, the habit or inhibition is that which is directly conditioned. Using this notation, the principle of primary stimulus generalization may be stated as follows: Hijrc

= Hkjk

x

10-adLik

(2)

The principle of stimulus interaction as stated above indicates that the generalized habit should be reduced by an amount which is some function of the average dissimilarity between corresponding components in the two compounds. As a first approximation, this reduction will be assumed to be given by the following expression2:

where n is the total number of dimensions in each compound and M is the maximal range of generalization, defined as the distance in j.n.d. units along a single dimension that a response will generalize when maximally motivated subjects have been conditioned to asymptotic performance on the C S 3 If diik is always taken as equal to or less than M, this expression will always be a Proportion. Thus, a combination of the principles of primary stimulus generalization and stimulus interaction may be stated in the following way:

where diik is always taken as equal to or less than M . Following Spence (1956), it will be assumed that inhibition of nonreinforcement ( I ) is an increasing function of the number of nonreinforced trials. Moreover, it is here assumed that it generalizes according to the same laws a

Sheldon H. White first suggested this expression as an approximation. is recognized that the maximum range of generalization may differ for different

' It

dimensions. Should this be found to be the case,

nM in the above expression.

2

MI should be substituted for

j=l

' I t should be pointed out that the hypothesis of stimulus interaction is independent of the particular form of the generalization gradient assumed. The deductions contained in this paper could also have been made with an assumption of a linear or ogival gradient.

237

Charles C. Spiker governing habit. An equation analogous to the preceding one may thus be written: n

(4)

We now wish to determine the total amount of habit which generalizes from to Si, considering all dimensions. Let Hi.k represent the total amount of habit that generalizes from Sk to Si on all n dimensions. We may then write the equation sk

It will be noted that this equation represents the simple summation6 of generalized habits overall dimensions. An analogous expression can be written for the generalization of inhibitory tendencies over all dimensions from Compound R to Compound i: n

An application of the stimulus interaction principle may be illustrated in a simple situation. Consider a generalization study in which the CS is a compound (Sk) consisting of two components, S, and S,. Suppose that 4 ~ units , of habit (Spence, 1956, p. 104) have been conditioned to each component. That is, Hklk = Hkzk = 4. Furthermore, following conditioning, a test compound (Si) is presented which consists of S, and S2’. Let it be assumed that S, and S,‘ differ from each other by 200 j.n.d. units. Since S, is common to both compounds, the two compounds do not differ on this dimension; that is, there are no j.n.d. units between the corresponding components on this dimension. Throughout this paper, we shall assume that the values of a and M in Eq. ( 3 ) are 0.01 and 200, respectively.

Simple summation was used rather than the Hullian “physiological summation’’ in order to simplify the computations.

238

The Hypothesis of Stimulus Interaction Thus, the amount of habit that would generalize from s k to Si by virtue of the common component, S,, would be 2ur0 units, half that conditioned to 5, in Sk (i.e., one-half Elklk). The total amount of habit that would generalize from s&to Si would be the sum of Hilk and Hizk, or 2.020,~units. These values should be compared with those obtained under the same assumptions except that S,’ differs from S2 by 40 j.n.d. units. In this case,

= 3.60

= 1.43

Here it can be seen that the contribution of Hilk to the habit loading of Si is 4 X .9 or 3.60. Thus, the value of Hilk is only .4mIO units less than the 4cr1~units of H7
A. APPLICATION OF STIMULUS INTERACTION TO THE SIMULTANEOUS AND SUCCESSIVE DISCRIMINATION PROBLEMS The relative simplicity of the application of stimulus interaction to the generalization study is unfortunately not replicated when it is applied to discrimination learning situations. The reader who has studied the Spence theory of discrimination behavior (Spence, 1936) will already be aware of the complex bookkeeping required to keep account of habits built up to components, to sum these to determine habits for compounds, and to compare habits of simultaneously presented compounds to determine the direction of choice. Except for the method of summating habits of components, the approach in this paper is the same. The reader should be assured, however, that the complexity is merely one of mechanics and not one of abstraction. An electronic computer can readily be, and has been, programmed to carry out the computations necessary for the derivations to be presented below. Application of the stimulus interaction hypothesis, in the present paper, will be restricted to two-choice discrimination learning problems in which one of the components in each compound is spatial. The simultaneous discrimination problem, in which the positions of the nonspatial cues are counterbalanced from trial to trial, will be analyzed in a manner proposed by Spence (1936).

239

Charles C . Spiker According to this analysis, the problem may be represented by the following schema :

in which W is white, G is gray, L is left, and R is right. The two settings represent two types of trials in each of which a pair of stimuli is presented simultaneously. In the problem schematized above, the subject is reinforced for approaching white and is not reinforced for approaching gray, regardless of the positions of these nonspatial cues. The numbers in parentheses designate the four compounds formed by combinations of the spatial and nonspatial elements. Examination of the above schema reveals that a given compound may receive generalized habit or inhibition as a result of the reinforcement or nonreinforcement of responses to several different compounds. Thus, Compound 1 in the schema could receive generalized inhibition from both Compounds 2 and 3. Similarly, Compound 2 could receive generalized habit from both Compounds 1 and 4. Using the symbol Hi..to designate the total habit of Compound i, resulting from habit directly conditioned to Compound i as well as that generalizing to it from the other ( m - 1) compounds, we may write the equation,

It will be noted that Eq. ( 7 ) specifies that habit directly conditioned to the components of Compound i will also be included in Hi.. , since the summation is over m rather than ( m - 1) compounds. An analogous equation can be written for the inhibitory tendency: n

In a discrimination problem, a compound that is consistently reinforced may nevertheless develop inhibition during the course of learning as a con-

240

The Hypothesis of Stimuhs Interaction sequence of generalization from compounds which are not reinforced. Conversely, a compound which is never reinforced may develop habit during the course of learning as a result of generalization from reinforced compounds. The difference between the habit and inhibition established to a compound will be referred to as efective hdbit and symbolized as Ai... Thus, the effective habit of Compound i may be represented as

Ri.. = Hi.. - I;... (9) It is assumed with Hull (1943) that when two stimuli are presented simultaneously, the probability of responding to the stimulus with the stronger habit is an increasing function of the difference in effective habit strengths, provided drive ( D ) is held constant. That is, Rp(

- flk..),

= f(Ri.

(10)

where Rpi represents the probability of responding to Compound i when the two Compounds i and K are simultaneously presented. The f in Eq. (10) is presumed to be a modification of the normal integral function (Hull, 1943). Let us apply the stimulus interaction principle to the simple simultaneous discrimination problem schematized above. For purpose of calculations, we shall assume a difference of 100 j.n.d. units between gray and white, and a difference of 200 j.n.d. units between left and right. We shall also assume that lq,unit of habit is built up to each component in the reinforced compounds, and that .2ar, unit of inhibition is built up to each component in the nonreinforced compounds by the end of training. A summary of the necessary calculations is shown in Table I, The entries in Column 1 of Table I designate the compounds, the habits of which are to be computed. Thus, the numbers of the compounds in Column 1 correspond to the i subscript of the H i j k and l i j k . The headings of the pairs of columns from 3 to 10 designate the compounds which are the sources of the habits and inhibitions, and correspond to the k subscript of H i j k and I i j k . The W, L, G, and R column headings correspond to the j subscript of the H i j k and Zijk. Thus, the entry under Column 3 in the row designated Hlik (1.000) is the value of H,,,, the amount of habit that is directly conditioned to the nonspatial dimension (W) of Compound 1 through the reinforcement of Compound 1. Similarly, the entry under Column 4 in the row designated H , j k (1.000) is the value of H,,,, the amount of habit that is directly conditioned to the spatial component (L) of Compound 1 through the direct reinforcement of Compound 1. The entries in the row designated Iljk under Columns 3 and 4 are zeros because no inhibition is conditioned to Compound 1 since it is always reinforced. The values of directly conditioned habit and inhibition are italicized. Under Column 3 in the row designated H z j k , is the value of H,,,( . 0 2 5 ) ,

241

Charles C. Spiher the amount of habit that generalizes to Compound 2 on the nonspatial dimension as a result of the reinforcement of Compound 1. This value is obtained through the application of Eq. (3), with the substitution of the appropriate values of diJk. Similarly, the value, .002, under Column 4 of the same row is the value of HZz1, the amount of habit that generalizes to Compound 2 on the spatial dimension as a result of the reinforcement of Compound 1. The entries in Columns 3 and 4 of Rows HsfICand H 4 j k are similarly obtained. The entries under Columns 3 and 4 for Z z j k , 13jk, and Z4jk are all zero because there is no generalization of inhibition to these compounds from Compound 1, since the latter is always reinforced. In the row designated Zzjk under Columns 5 and 6 are given the amounts of inhibition ( 2 0 0 ) directly conditioned to the nonspatial (G) and spatial (R) dimensions of Compound 2. Since Compound 2 is never reinforced the entries in these columns for Row HzjIEare zeros, In the row designated z l j k under Column 5 is the value of I,,, (.005); that is, the amount of inhibition that generalizes to Compound 1 on the nonspatial dimension as a result of the nonreinforcement given to Compound 2. This value is obtained through the appropriate substitution of values for diik in Eq. (4). Similarly, the number (.0002) given under Column 6 for the row designated I l j k , is the value of I,,,, the amount of inhibition that generalizes to Compound 1 on the spatial dimension through the nonreinforcement of Compound 2. The entries under these cohunns for Rows 13jk and I d j k are computed in a similar fashion. It will be noted that the values under Columns 5 and 6 for Hljk, H3jk, and H4jk are zeros because there will be no generalization of habit to these compounds from Compound 2, since the latter is never reinforced. The entries in Columns 7 and 8, and 9 and 10 are obtained in a manner similar to those for Columns 3 and 4, and 5 and 6. The first entry in the last column is the sum of the values in the row designated Hlin and is, therefore, the value of HI. ,. The second entry in the last column is the sum of the values in the row designated Zljkand is the value of I, The third entry is the difference between H , , . and Z,.,, and, as indicated, is the value of Rl,., the effective habit strength for Compound 1. Corresponding interpretations should be made for the remaining values in the last column of Table I. The computation of the values in Table I constitutes the prediction that, at the end of training, when Compounds 1 and 2 are presented simultaneously, the subject will have a preference for Compound 1, since the value of R l . . ( 2 . 3 3 5 ) is greater than (.351). Also, when Compounds 3 and 4 are presented simultaneously, the subject should have a preference for Compound 4. Briefly, Table I constitutes the derivation that the simultaneous problem can be solved by the subject.

...

n,.,

242

The Hypothesis of Stimulus Interaction The derivation that the simultaneous problem is soluble, while necessary, is hardly a crucial test of the utility of the stimulus interaction principle. Spence (1936) demonstrated long ago that a theory which assumes that habit and inhibition are built up to the components of a compound can predict the solution of the simultaneous problem, even without a principle TABLE I

DERIVATION OF THE

SOLUBILJTY OF THB SIMULTANEOUS

DISCRIMINATION PROBLEM

Source of habit and inhibition

(1)

(2) Hijk

Compound 1

Iijk

Compound

Compound

I(+)

2(-)

Compound 3(-)

Compound 4(+)

W

L

G

R

G

L

(3)

(4)

(5)

(6)

(7)

(8)

(9)

,000 .OOo .005 .0002

,000 .OOO

.500

,015 .150

.OOO .OOO

.I70 2.335

.002 .OOO

.OOO ,000 .200 .200

.OOO .OOO .lo0 .001

.075 .750 .OOO .OOO

.852

,075 .750 ,000 .OOO

.OOO .OOO

.OOO .OOO

,025

,002

,852

.I00 .OOl

,200 .200

.OOO

,000

.501 .351

.500

,000

1.000 1.000 .OOO .OOO

W

R (10) .005

R,.. Compound 2

HZjk

.025

Izjk

.OOO

RZ.. Hair

Compound 3

Isjk

Ra.. Hijk

Compound4

I4jk

R,..

.005

.ooo

.OOO .OOO .015 .150

.OOO .oOo .005 .0002

Totals (11) 2.505

.501 .351

1.000 1.000 2 . 5 0 5

.OOO

,000

.170 2.335

corresponding to stimulus interaction. A more critical test of the utility of the stimulus interaction hypothesis can be obtained by examining the so-called successive discrimination problem. A schematic representation of this type of problem is given below:

Setting 1

Setting 2

243

Charles C. SpiRer in which W is white, G is gray, L is left, and R is right. The two stimulus settings represent two types of trials. In the problem schematized above, the subject is reinforced for approaching white on the left and is not reinforced for approaching white on the right in Setting 1. I n Setting 2 the subject is reinforced for approaching gray on the right but is not reinforced for approaching gray on the left. The numbers in parentheses are again used to designate the four compounds formed by combinations of the spatial and nonspatial components. Examination of the above schema reveals that the subject is not reinforced consistently for selecting any one component, either spatial or nonspatial. W e may now apply the stimulus interaction hypothesis to the successive discrimination problem assuming exactly the same values as were assumed for the simultaneous discrimination problem. The relevant computations are shown in Table 11, which is organized in the same manner as that of Table I. A comDERIVATION OF

THE

TABLE I1 SOLUBILITY OF THE SUCCESSIVE DISCRIMINATION PROBLEM

Source of habit and inhibition

Hijk

Compound 1

ZIjk

1.000 1 . 0 0 0

.OOO

,000 ,000

,000

.ooo

,015 .I50

.OOO

.500 ,005 .OOO .OOO

.ooO .oOO

.075 .750 1.330 .OOO .OOO .405 .925

Q'.. H2jk

Compound 2

.OOO

.ooO

Hajk

.075

13jk

.OOO

.750 .OOO ,000 ,000 ,000 .OOO .005 .0002 ,200 .200

12jk

.ZOO .200

.005 .0002

G.. Compound 3

,025 .002 2.027 .OOO .266 1,761

.OOO .lo0 ,001

,500 ,005 1.330 .OOO ,000 .405

,925

€72,.

H4jk

Compound 4

z4jk

a,.

,025 .002 .OOO .OOO

.ooo ,000 .015 .I50

,000 .ooo .I00 .001

1 . 0 0 0 1.000 2.027 .OOO ,000 .266

1,761

n1,.

parison of the effective habits for Compounds 1 and 2 (that is, and 8,..) indicates that R, ., is greater than H2.. . Thus, at the end of training, the subject should demonstrate a preference for Compound 1 when these two compounds are presented simultaneously, and a preference for Compound 4 when it is

244

The Hypothesis of Stimzllzrs Interaction simultaneously presented with Compound 3. This constitutes a deduction that the successive discrimination problem is soluble, a fact that has been repeatedly demonstrated for both human and infrahuman subjects. A comparison of values in Tables I and I1 reveals another interesting deduction. In Table I, the value of Bl.. is 2.335 and the value for is ,351, with a difference between the two of 1.984. In Table 11, the value of I?,.. is 1.761, the value of Hz., is .925, and the difference is .836. According to Eq. (lo), the probability of choosing the stimulus with the higher effective habit strength is an increasing function of the difference between the effective habit strengths of the two simultaneously presented compounds. Thus, the prediction is that the subjects given a specified amount of training on the simultaneous problem would perform better at the end of training than a corresponding group of subjects given the same amount of training on the successive problem. Empirical research indicates that, at least under certain conditions, the successive problem is indeed more difficult than the simultaneous (Bitterman & McConnell, 1954; Lawrence, 1949; Loess & Duncan, 1952; MacCaslin, 1954; Spence, 1952; Price, 1959; and Lipsitt, 1961) .6

nz..

B.

CONVENIENT

EQUATIONSFOR

SPECIAL CASES

The computations necessary to construct Tables I and I1 are quite tedious to carry out by hand. Although electronic computers have been programmed to carry out these computations, it is often convenient to have short-cut equations that provide quick solutions with a desk calculator. I n this section, some of the simpler equations for special cases are derived. W e shall begin with Eq. (3), n

Let P i j k represent the proportion of habit or inhibition which generalizes to Compound i from Compound k on Dimension j . That is, n

'It should be noted that the successive discrimination problem has been found to be easier for children than is the simultaneous problem when the response locus is removed from the stimulus source (Lipsitt, 1961). The present formulation, following Spence (1936; 1 9 5 2 ) , assumes that the subject responds by approaching or otherwise directly manipulating the discriminanda. 245

Charles C. Spiker Note that rewritten,

Pijk

can range from zero to unity. Equation (3) may now be Hijk

= Hkjgijk.

(12)

The total habit generalizing to Compound i on all dimensions as a result of the reinforcement of Compound k ( H i . k ) is given by the foIIowing equation: n

W e shall now make the first of our simplifying assumptions. Assume that each component in a reinforced compound develops the same amount of habit; that is, H k j k is a constant. Under this assumption we may write, n

j

Let,

then, and, Let Compound 1 be reinforced and Compound 2 be nonreinforced in presentations of Setting 1 in the simultaneous discrimination problem. The difference in effective habit strengths between these two compounds at the end of training would be given by the formula,

where m is the total number of compounds involved in the discrimination problem. Using Pi . k values, we may rewrite Eq. (18),

(19)

which simplifies to,

246

The Hypothesis

of Stimulus Interaction

The corresponding equation for the difference in effective habit strengths between Compounds 4 and 3 is given below : m

R4..

- R3.. =

1

[(Hkik

- Z k j d ( P 4 . k - PPk)].

k-1

Although Eqs. (20) and ( 2 1 ) may be used for the typical simultaneous or successive discrimination problems, still more convenient equations can be derived by taking account of the usual conditions under which these problems are presented. It will be noted that Hziz and H s j s may be assumed to be zero since Compounds 2 and 3 are never reinforced. Similarly Zlil and Z4j4 may also be assumed to be zero since Compounds 1 and 4 are always reinforced. Recognizing these conditions, we may expand and substitute in Eq. (20) as follows:

RI..- R2.. = [HVl(P1.1 - P2.1) - I~j~(p1.2 - Pz.z)] [H4j4(P1.4- P2.4) - 13j3(P1.3 - pZ.3)]*

+

(22)

Assume further that each component in Compounds 1 and 2 has the same amount of habit directly conditioned to it, that each component in Compounds 2 and 3 has the same amount of inhibition directly conditioned to it, and that the ratio of H to Z is Y. Under these assumptions the difference in effective habits for Compounds 1 and 2 may be written as follows:

Rl.. - R2.. = Hljl ([(Pl.,- Pz.1) - r(P1.2 - P2.2)] L(Pl.4 - p 2 . 4 ) - @ i , 3 - p 2 . 3 ) ] ] . (23) Note that PX.,= Pz.2= P k j k = n, since P k j k is unity. Also note

z;=l

+

the following sets of equalities, Pl.2 = p2.1,

p1.4 = p4.1,

p2.3 = p 3 . 2 ,

since the generalization between any two compounds is symmetrical. Whenever the appropriate d,jlc values are equal-that is, when d,,, = dZl3, d,,, = d,,, = dZl4,etc.-the following sets of equalities will also hold: Pl.4

=

p2.3,

p1.3 = p 2 . 4 ,

p1.2

=

p3.4.

Examination of Table IV reveals that these equalities hold in the typical simultaneous or successive discrimination problem and we may write, R1..

- Rz.. = Hljlf[(Ptl - PI.2) - r(P1.2 - Pz.z)] PI.^ - pi.3) - r(Pi.3 - pi.4)1}, (24)

which simplifies to,

RI..- Rz..= Hljl(r

+

+ l>(P1.1+

p1.4

- P1.2 - P1.3).

(25)

24 7

Charles C. Spike? Under the conditions listed above, Eq. (25) also gives a solution for the difference in effective habits for Compounds 4 and 3 . It is often the case that one wishes to evaluate the relative difficulty of two or more discrimination problems, where difficulty is understood to be the amount of training required to develop a given degree of mastery, rather than level of performance following a specified amount of training. If the difference between the effective habits of the positive and negative compounds determines the final level of performance, then the solution of Eq. (25) for the value of HI?, should provide an index of problem difficulty, since it indicates the amount of habit that must be directly conditioned to each component of Compound 1 to achieve the specified performance level. The solution is given in Eq. (26),

in which the smaller the value of HIjl, the easier the problem. It is also apparent that the difficulty of the problem, as far as generalization among compounds is concerned, is inversely related to the expression

Let D, represent the difficulty of a problem due to generalization among the compounds. W e may then write Eq. (27) as follows: D,

=

1

p1.1

+ p1.4 - pl.2

-

P1.3’

in which D, is directly related to problem difficulty. From Eq. (27), it may be seen that the relative difficulties of discrimination problems resulting from generalization among the compounds, at least under the conditions specified in the foregoing discussion, can be determined without computing the amount of habit and inhibition build up to the positive and negative compounds, respectively. One of the chief advantages of Eq. (27) is that tabled values of Pi. can be computed and used conveniently in the derivation of the relative difficulty of problems. Table I11 gives Pi.kvalues for several levels of similarity among the components of two-dimensional compounds. It is probably well to summarize the conditions under which Eq. (27) can be utilized. 1. The amount of habit directly conditioned to each component of the positive compounds must be the same.

248

The Hypothesis of Stimulus Interaction 2. The amount of inhibition directly conditioned to each component of the negative compounds must be the same. 3 . The two stimulus settings must be comparable in that the proportion of generalization from Compound 1 to Compound 2 is equal to that from Compound 4 to Compound 3; that from Compound 1 to Compound 3 is the ‘.TABLE

111

VALUESOF Pt.kFOR THE GENERALIZATION OF HABITOR INHIBITION FROM ONE TWO-COMPONENT COMPOUND (Sk) TO ANOTHER(Si) AS A FUNCTION OF THE SIMILARITY OF THE CORRESPONDING COMPONENTS IN THE Two COMPOUNDS, ASSUMINGBOTH COMPONENTS OF s k TO BE EQUALLYCONDITIONED

Differences (j.n.d.) between corresponding spatial components 0 25 50 100 150 200

Differences (j.n.d.1 between corresponding nonspatial components ~~

0

25

50

100

2.000 1.464 1.152 .824 1.464 . 7 1 3 ,456 .984 .713 ,474 ,260 1.152 .456 ,260 .I00 .824 .333 ,174 ,050 .644 ,252 ,121 .028 ,505

150

200

.644

.505

.333

,252 ,121 .028 ,006 ,000

.I74 ,050 ,016 ,006

same as that from Compound 4 to Compound 2 ; and that from Compound 1 to Compound 4 is the same as that from Compound 2 to Compound 3 .

111. Deductions With the Hypothesis of Stimulus Interaction A. STIMULUSSIMILARITY IN THE SIMULTANEOUS AND SUCCESSIVE DISCRIMINATION PROBLEMS An experiment by MacCaslin (1954) has shown that the difficulty of the successive problem, relative to that of the simultaneous, increases with increasing similarity of the nonspatial cues. While the difficulty of both problems increases with increased similarity of the stimuli, the successive problem becomes relatively more difficult. The use of the hypothesis of stimulus interaction permits the derivation of such a result. Table IV shows a schema of the simultaneous and successive discrimination problems in which A and B are the nonspatial cues (e.g., black and white), and where L and R represent the spatial positions left and right, respectively. The four compounds in each of the two problems are indicated by the arabic numbers in parentheses. Consider first the case in which there are 200 j.n.d.’s

249

Charles C. Spiker TABLE IV SCHEMAOF SIMULTANEOUS AND SUCCESSIVE DISCRIMINATION PROBLEMS Simultaneous task

Successive task

between A and B and 200 j.n.d.'s between L and R. Application of Eq. (27) to the simuItaneous problem, using values obtained from TabIe 111, gives the following result:

D, = =

1

2.000

+ .505 - .OOO - .505

.500.

Application of the same equation to the successive problem yields the result shown below: 1

D' = 2.000

+ .OOO - .505 - .505

= 1.010.

Now assume that there are 25 j.n.d's between SA and S,. For the simukaneous problem, Eq. (27) yields a D, value of 1.267. Under the same conditions the difficulty of the succesive problem is 3.534. A comparison of the simultaneous and successive discrimination problems, for four degrees of similarity of the nonspatial cues, is shown in Table V. The TABLE V

THEORETICAL VALUES

OF THE RELATIVE DIFFICULTY DUETO GENERALIZATION (Do) OF SIMULTANEOUS A N D SUCCESSIVE PROBLEMS, AS A FUNCTIONOF CUES INCREASING SIMILARITY OF THE NONSPATIAL

Difference between nonspatial cues (j.n.d.)

250

Simultaneous

Successive

Difference

200

.500

1.010

100

.605

1.431

.826

50 25

.812

2.155

1.267

3.534

1.343

,510

2.267

The Hypothesis of Stimulus Interaction values of D,, for 200, 100, 50, and 25 j.n.d.’s, are shown separately for the simultaneous and successive problems. In the final column are the differences between the corresponding values for the simultaneous and successive problems. As can be seen, there is a predicted increase in the difference in difficulties of the simultaneous and successive problems with an increase in the similarity of the nonspatial cue. Another comparison of the simultaneous and successive problems is illustrated in Table VI. In this table, SA and SA’ represent different values on one TABLE VI COMPARISON OF SIMULTANEOUS AND SUCCESSIVE PROBLEMS WITH

NONSPATIAL CUE Simultaneous

A

SECOND

CONFOUNDED WITH THE SPATiAL C U E

Successive

dimension, S, and SBt represent different values on a second dimension, and SL and S, represent the values of left and right on the spatial dimension. Examination of the two problems represented there indicates that the B-dimension is completely confounded with the spatial dimension; that is, SB and SL always appear together, as do S,’ and SR.W e have already seen that the stimulus interaction hypothesis predicts that an increase in the similarity of the relevant nonspatial cue will result in a relatively greater increase in difficulty for the successive than for the simultaneous problem. The question now arises as to the prediction of the hypothesis with respect to the similarity of the nonspatial cue that is confounded with the spatial positions. Suppose that one group of subjects receives the simultaneous problem shown in Table VI with 200 j.n.d. units between SA and SA’, 200 j n d . units between SL and SR, and 200 j.n.d. units between SB and Ss’. A second group receives the successive problem with the similarity of the stimuli the same as that for Group 1. A third group receives the same simultaneous problem as that for Group 1 except that there are 25 j.n.d. units between SB and SD’. A fourth group receives the successive problem with the same values for the stimuli as that for Group 3. The problem is to predict the relative difficulty of these four groups.

2s 1

Charles C. Spiker The use of Eq. (27) requires the Pi.k values for three-dimensional stimuli. Space does not permit the inclusion of such a lengthy table, but they may readily be computed from Eq. (28), given below: n

The necessary values are given in Table VII. The application of Eq. (27) for Group 1 gives the values of D, shown in the last line of Table VII.

SUMMARY OF

THE

TABLE VII DERIVATION OF THE RESULTSOF

THE

PRICEEXPERIMENT

Simultaneous

Successive

Simultaneous

Successive

Group 1 200

Group 2

B and B‘

Group 3 25

Group 4 25

PI.1

3.000

3.000

,336

.000

3.000 ,170 ,982

j.n.d.’s between

PI., p1.2

P1.a

Do

2 00

,000

,336

3.000 ,982 ,170

1.341

1.341

1.341

1.341

,405

1.181

.501

,756

Remembering that the D, values are directly related to difficulty, the reader will note the rather remarkable prediction that an increase in the similarity of the nonspatial cue confounded with the spatial cue results in an easier simultaneous problem but a more difficult successive problem. An experiment by Price (1959) provides an opportunity to test the applicability of the stimulus interaction hypothesis to the behavior of children. Price studied 16 preschool children assigned to each of the 4 groups discussed above. The apparatus consisted of 2 boxes which were presented approximately 18 in. apart. Square or triangular apertures were cut in frames and correspond to S, and SA’. In the rear of each box was a projection buIb covered by either a red or blue glass filter to correspond to SB and SBt. The subject had to reach through the square or the triangle in the box to obtain a marble. He was informed that if he earned enough marbles, these could be exchanged for a toy. Each subject received a minimum of 30 trials, and if he did not reach a criterion of 5 correct choices on each of two successive blocks of 6 trials within the first 30 trials, he was continued until he did reach this criterion or until a maximum of 54 trials had been administered. The similar nonspatial cue con-

252

The Hypothesis of Stimulus Interaction founded with position consisted of either 2 similar red lights or 2 similar blue lights. The results of this experiment are shown in Fig. 1. It will be observed that the groups ranked in the order of increasing difficulty: Group 3, Group 1, Group 2, and Group 4 , the order predicted in the preceding computations. An analysis of variance of the number of correct responses in the first 30 trials yielded an interaction significant at the .01 level between the similarity of the

-*--

& I

9-

-

.+------/

Group I

---e Group 2 ----a

Group 3 Group 4

Blocks of six trials

Fig. I. Mean number of correct responses per trial block.

nonspatial cue confounded with positions and the simultaneous-successive variable.

B. CUE-POSITION COMPOUNDING AND DISCRIMINATION PROBLEMS Birch & Vandenberg (1955) specifically designed an experiment to determine whether or not evidence for stimulus compounding can be obtained in transfer situations following training in which the subjects are differentially reinforced on one of the elements in the compounds. The design of part of their experiment is shown in Table VIII. Twenty-eight rats were first trained on a simultaneous problem to approach black when it was presented on the left with gray presented on the right, and to approach white on the right when presented with gray on the left. Four groups of 7 subjects each were differentiated according to the nature of the second task, as shown in Table VIII. The second task was the same for Groups A and B, except for the compound in each setting that was reinforced. Groups C and D also differed only in terms of the compound in each setting that was correct. Compounding would be evidenced if Group A performed above the 50% level, if Group B performed below the 50% level, if Group C performed at less than the 100% level, and if

253

Charles C. Spiker Group D performed at better than the 0% level at the beginning of the second task. The percentages of correct choices obtained in 20 reinforced test trials on Task 2 were 69% for Group A, 36% for Group B, 86% for Group C, and 34% for Group D. EXPERIMENTAL DESIGN OF

TABLE VIII" EXPERIMENT BY BIRCH& VANDENBERG

THE

Original task (All Ss)

Second task Group C

Group A

Group D

Z .

G

= gray.

and (-)

B =

= black, W = white, L = left, R nonreinforced.

=

right. (+) = reinforced,

The major trends in these data may be predicted quite well with the stimulus interaction hypothesis. Examination of the first-task learning curve indicates that, on the average, 85% correct choices were made. Since there were approximately 5 correct choices to one incorrect choice, it wiI1 be estimated that the ratio of H to I is 5 to 1 ( r = 0.2). It will be assumed that there are 200 j.n.d. units between the white and the black stimuli and that the gray

254

The Hypothesis of Stirnuhs Interaction stimulus is 100 j.n.d. units from either white or black. Since the apparatus used was a Y-maze, it will be assumed that some generalization occurred between the spatial cues, specifically that 100 j.n.d. units lie between them. (The assumption that there was some generalization between the spatial cues is necessary to predict the exact rank order of the four groups in the transfer task. It is not necessary, however, in order to predict the superiority of Group A over Group B and of Group C over Group D.) For simplicity, it is also assumed that l~,, unit of habit is built up to each component of the positive compounds and that .2Ul0 unit of inhibition is built up to each component in the two negative compounds by the end of training on the original task. (The amount of I directly conditioned to S, will be .&I, unit, since SG appears in both negative compounds.) These assumptions result in a symmetry of the values obtained for the two settings, thereby necessitating the derivation of only one of the two settings in each problem. The computations were carried out in the manner illustrated in Tables I and 11 and are not reproduced in detail. The values given in Table I X are those TABLE IX DERIVATION OF RESULTS OF BIRCH-VANDENBERG EXPERIMENT

-

fi, .

H-..

1.84 1.14 1.14 .36

1.14

R+..- IT.. 96 Correct ~~

Group Group Group Group

A B

C D

1.84 .36 1.14

.70 -.70 .78 - .78

69 36 86

34

which would obtain for the positive and negative compounds in the first setting of Task 2 following the original training, but prior to the beginning of training in Task 2. The last two columns provide a comparison between the predicted difference in effective habit to the positive compound and that to the negative compound, on the one hand, and the obtained per cent correct responses for the four groups on the other hand. It will be observed that there is a perfect correlation between group ranks in the two columns. An experiment by White & Spiker (1960) was designed as an explicit test of one of the implications of the stimulus interaction hypothesis, as it may apply to the learning of children. The basic design of the experiment is given in Table X. The reader will note that the original training for Groups I and I1 consists of one lateral arrangement from each of two simultaneous discrimination problems. The transfer test consists of the lateral reversals of the two settings in the original training task, and is administered without reinforcement. The difference among the three groups concerns the similarity of the nonspatial cues involved in the two discrimination problems. Group I was

255

Charles C. Spiker required to discriminate between red and yellow and between black and white; Group 11, between red and orange and between gray and white; and Group 111 received a successive problem with the nonspatial cue being red in Setting 1 and white in Setting 2. It will be noted that the within-pair similarity of the nonspatial cue increases from Group I through Group I1 to Group 111. There were 14 preschool children in each of the three groups. The two stimuli to be discriminated were fitted into the front faces of wooden boxes BASICDESIGN OF Group

Setting

EXPERIMENT

Training task

~

Y

TABLE Xa THE WHITE-SPIKER

Transfer task

~

= yellow, W = white, B = black. 0 = orange, G = gray. L

-

~~

left, and R = right.

mounted 6 in. apart. During the original training, the subjects received a marble for each correct choice. The subjects were trained on Task 1 to a criterion of 11 correct in 2 successive blocks of 6 trials. All subjects were then given 10 test trials on the appropriate transfer task. During the transfer task, the subject was informed that the experimenter would look to determine whether or not there was a marble in the box of the subject’s choice. In this way, it was possible to administer the transfer task without providing the subject information as to the correctness of his choice. The response measure was the number of

25 G

The Hypothesis of Stimulus Interaction “patterned responses”-that is, the number of times the subject chose the stimulus that was in the same position as the reinforced stimulus for that setting in the original task. In terms of the notation of Table X, the selection of Compounds 5 and 8 in the transfer test for Group I and 11, and the continued selection of Compounds 1 and 4 for Group 111, were considered patterned responses. For Groups I, 11, and 111, the mean numbers of patterned responses were 2.36, 6.50, and 9.36, respectively. The stimulus interaction principle permits a clear-cut prediction of the outcome of this experiment. For simplicity, it is assumed that in the original task the two positive stimuli were equally often reinforced, the two negative stimuli were equally often not reinforced, the elements within a compound were equally conditioned, and the ratio of H to I is 5 to 1. It is also assumed that bI,, unit of habit is conditioned to each component of the positive compounds and unit of inhibition is conditioned to each component in the negative compounds. Within settings, it is assumed that there are 200 j.n.d.’s between the nonspatial stimulus components for Group I, 50 j.n.d. units between the nonspatial components for Group 11, and that there are 0 j.n.d. units between the two reds and between the two whites for Group 111. It is also assumed that there is no generalization between settings on the nonspatial dimension and none between the two positional cues. These assumptions result in symmetrical values for the effective habits of the two stimulus settings in each group, and computations need be carried out only for the first setting in the transfer task. The computations were carried out in the manner of Tables I and I1 and are not reproduced in detail. A summary of the results of these computations is given in Table XI. TABLE xr DERIVATION OF RESULTSOF WHITESPIKER EXPERIMENT

Group

a,.

I I1

.30

111

1 .80

.95

R8..

.91 .78 .61

Rh.. - Re..

Mean number of patterned responses

- .61 .17 1.19

2.36 6.50 9.36

-

The first column of Table X I gives the value of the effective habit strengths for Compound 5 (Compound 1 for Group 111) in the transfer task. The second column gives the effective habit for Compound 6 (Compound 4 for Group HI) and the third column gives the difference between the effective habits of these 2 compounds. The last column gives the mean number of patterned responses made by each of the 3 groups. A comparison of the last two

25 7

Charles C. Spiker columns reveals that the results and the theory are in quite good agreement, both indicating that the amount of “cue-position patterning” is an increasing function of the within-setting similarity of the nonspatial cues. An experiment by Johnson (1962) was designed as a further test of the utility of the stimulus interaction hypothesis in predicting the learning of children. The basic design of this experiment is shown in Table XII. The TABLE XI1

BASICDESIGN

OF JOHNSON EXPERIMENT

Training task

Transfer task Group A

Group B

reader will note the similarity of this design and the procedures for Groups A and B in the Birch-Vandenberg experiment. Johnson was interested in replicating the findings of White and Spiker (1960) that “cue-position patterning” occurs in the learning of discrimination tasks by preschool children, and in discovering whether such patterning is affected by the amount of training in the original task. Sixty-four kindergarten children were used as subjects. Half of these subjects were trained to a criterion of 5 correct responses on each of 2 consecutive blocks of 6 trials in the original problem. The other half of the subjects were trained to the same criterion and were then given an additional 18 trials. All subjects received 24 trials on the transfer task. Half the subjects in each training group were reinforced for the selection of Compounds 1 and 4 and not reinforced for the selection of Compounds 5 and 6 (Transfer Task A ) . The other half of the subjects in each of these 2 groups were reinforced

258

The Hypothesis of Stimulus Interaction for selecting Compounds 5 and 6 and not reinforced for selecting Compounds 1 and 4 (Transfer Task B). The basic design is therefore a 2 x 2 factorial, in which Group A-Lo received a low amount of training in the original task and was given Transfer Task A; Group B-Lo received a low amount of training in the original task and was given Transfer Task B; Group A-Hi received a high amount of training on the original task and was given Transfer Task A; and Group B-Hi received a high amount of training on the original task and was given Transfer Task B. The major results of this experiment can also be derived with the aid of the stimulus interaction hypothesis. It was assumed that there were at least 200 j.n.d. steps between any pair of components, spatial or nonspatial. For the groups given a low amount of training in Task 1, it was assumed that b,,unit of habit was directly conditioned to each component in the positive compounds, and that .2a1, unit of inhibition was directly conditioned to each component in the negative compounds. For the groups given the high amount of training in Task 1, it was assumed that 20, units of habit were directly conditioned to each component in the positive compounds and that .40,, unit of inhibition was directly conditioned to each Component of the negative compounds. These assumptions, once again, result in symmetrical values of effective habit for the two stimulus settings and, therefore, the values need be calculated only for Setting 1 of the transfer task. The method of derivation is the same as that used in the preceding problem and details of the computations are not given here. A summary of these computations, together with the results of the Johnson experiment, is given in Table XIII. The first column of figures TABLE XI11 DERIVATION OF RESULTSOF JOHNSON EXPERIMENT

-

Group

R+..

H-. .

B-Hi B-LO A-LO A-Hi

1.82

3.80 1.90

.91 1.90 3.80

R+..- R-.. Correct responses -1.98

- .99

.91

.99

1.82

1.98

13.5 14.2 16.8 17.8

represents the effective habit for the positive compound for each of the four groups, the second column gives the values of the effective habit to the negative compound, the third column gives the difference between the effective habits for the positive and negative compounds, and the last column gives the mean number of correct responses for the 24 trials of the transfer task. The Jonckheere (1954) test against ordered alternatives was applied to the data of the last column of Table XIII. The resulting statistic was significant at the .003

259

Charles C. Spike? level by a one-tailed test, indicating that the interaction between type of problem and amount of training is statistically reliable. The reader will note that the theory ranks the groups in the same order as do the empirical results. An unpublished experiment by SpikerT was designed to test an interesting deduction from the stimulus interaction hypothesis concerning the relative difficulty of two discrimination tasks. As can be seen in Table XIV, which TABLE XIVn DESIGN OF SPIKEREXPERIMENT ~

~

“Easy” task

“Hard” task

~

0

~

L = large, W = white, S = small, and B

=

black.

shows the design of this experiment, the positive compounds in the 2 tasks are the same. The difference in the 2 problems lies only in the negative compounds, and with respect to these, only in the positional placement of the nonspatial cues. The reader will note that if the size cues are made increasingly simiIar, to the point of identity, the “easy” task would become in effect a successive problem. The “hard” task, however, would become insoluble. The stimuIi were large (4” x 4”) and small (3” x 3”) blocks, painted black or white. Each stimulus block could be opened along the frontal plane to expose a recess into which a marble could be placed. The two stimuli to be discriminated were placed approximately 12 in. apart on an 18 x 22 in. rectangular turntable. A vertical 12 x 22 in. screen, located in the center of the turntable, prevented the subject from observing the experimenter preparing the apparatus for the next trial. The entire apparatus was painted a light green. The subjects were 32 children from the Iowa Child Welfare Research Station preschool laboratories. One-half of the subjects were randomly assigned to the easy task and the other half to the hard task. The two nonspatial stimulus dimensions were counterbalanced so that half the subjects in each group received the task as shown in Table XIV, with the size dimension as the withinpair cue; the other half of the subjects in each group received an analogous task in which black-white was the within-pair dimension. The subjects were informed that they were going to play a game in which they could win marbles ‘The writer is indebted to Wanda Spiker for collecting the data of this experiment.

260

Tbe Hypothesis of Stimulus Interdction and that when they had won enough marbles they could use them for money to buy a toy which they had previously chosen. The experimenter demonstrated for the subject the manner in which the blocks could be opened. The subject was then informed that the experimenter would hide a marble in 1 of the 2 blocks and that each time the subject was to try to find the marble. Each subject received 1 5 presentations of each of the 2 stimulus settings, presented in a prearranged order so that the positive stimulus appeared equally often on the left and right in each block of 10 trials, for a total of 30 trials. The response measure was the number of correct responses in 30 trials. In predicting the outcome of the experiment, it was assumed, as usual, that the positive compounds were equally often reinforced, that the negative compounds were equally often nonreinforced, and that the increment of habit or inhibition on each trial was the same for each component in a compound. It was also assumed that there are 200 j.n.d.’s between the large and small components, between the black and white components, and between the left and right spatial positions. The values of a and M were assumed to be the same as in previous derivations. A summary of the derivation and of the experimental results is presented in Table XV. It will be seen in the next to the last column TABLE XV DERIVATION OF RESULTS O F SPIKER EXPERIMENT

-

Group

R+..

H-. .

Fi+. - Fi-..

Correct responses

E H

3.20 3.07

.Ol

.6?

3.19 2.40

27.1 23.8

that the difference in effective habit for the positive and negative compounds is greater for Group E than for Group H. The last column indicates that the mean number of correct responses obtained for Group E was greater than that obtained for Group H. An analysis of variance indicated that the difference in means for Groups E and H was significant at the 5 % level, that the difference in the stimulus counterbalancing groups was not significant, and that there was no significant interaction between groups and counterbalancing conditions. The experimental results, therefore, are consistent with the outcome predicted by the stimulus interaction hypothesis.

C. THE CONDITIONAL DISCRIMINATION A schematic representation of the conditional discrimination or conditional reaction problem, as studied by Lashley (1938), is shown in Table XVI. In

261

Charles C. Spiker the original problem, the subject is reinforced for choosing the circle, regardless of its spatial location, when the circle and a triangle are presented on a black background. I n the reversal problem, the subject is required to choose the triangle when the forms are presented on a white background. The original and reversal problems are alternated several times. Research indicates that rats, chimpanzees, and monkeys can learn to respond without error after several alternations. Examination of the schema indicates that the conditional discrimination can be readily conceptualized as a type of successive discrimination problem. Imagine the two stimulus settings of the reversal problem interpolated among presentations of the 2 settings from the original problem. The resulting 4-setting TABLE xv15 SCHEMAFOR CONDITIONAL DISCRIMINATION

a

0 = cirde, A = triangle, L and W = white.

=

left, R = right, B = black.

problem, like the typical successive problem, would have no component that is consistently reinforced; that is, each component is equally often reinforced and not reinforced. The conditional discrimination, therefore, can be viewed as a 4-setting successive discrimination problem in which the settings are not presented in a random order, but rather that a block of presentations of one pair of settings is alternated with a block of presentations of the other pair. When the cues signaling reversal are viewed as successive cues, it is apparent that the rate of development of the conditional reaction should be inversely related to the degree of similarity of these conditional cues. Two experiments were conducted with preschool children by Hoyt (1960; 1962) to test this hypothesis. In her first experiment, 2 groups of 24 preschool children each were given 7 problems, all employing the same 2 stimuli in a series of reversals, presented on a tray which was changed in brightness in order to signal reversaI. For one group the 2 trays were white and black; for the other group, they were dark gray and light gray. The stimuli for both experimental groups were a pair of red blocks, a circle 4 in. in diameter and a diamond with axes of 4 in.

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The Hypothesis of Stimulus Interaction and 6 in. The top and bottom halves of each block were identical except for a hoIe in the bottom half deep enough to contain a marble. A correct choice was rewarded by the subject’s findings a marble in the bottom half of the block. A black curtain was suspended between the subject and the experimenter to hide the apparatus while preparation was made for each trial. The subjects used the marbles to purchase a toy which had previously been selected. The experimenter continued training on the first problem until the subject had selected the correct stimulus on 8 trials out of 10. Immediately following the last criterion trial, the alternate tray was presented and the first reversal problem begun. Six trials were given on the first reversal and on each succeeding problem. A record was kept of the subject’s choice on each trial of each problem, An analysis of the number of trials required to reach criterion on the first problem revealed no significant differences between the two experimental groups. An analysis of variance of the number of correct responses in the 6 reversal problems, however, revealed that the group receiving the dissimilar trays performed significantly better than the group which had received the similar trays. In a second experiment using essentially the same methodology as in the first study, Hoyt compared the acquisition of the conditional reaction by three groups with 18 kindergarten children each: for Group D, changes in the reward values of the stimuli were signaIed by black and white trays; for Group S, changes in the reward values of the stimuli were signaled by light and dark gray trays; and for Group I, the trays were identical throughout all problems. Analysis of the number of correct responses for each problem revealed significant differences among the 3 groups. Group D performed better than did Group S, which in turn performed better than Group I. The analysis also indicated that the differences among the three groups increased as a function of the number of prior problems they had received. There was no statistical evidence for an improvement in Group I as a function of the number of prior problems. Hoyt (1962) showed that the main results of her experiment could be deduced by means of the stimulus interaction hypothesis.

IV. Summary The hypothesis of stimulus interaction, a modification of Hull’s principle of afferent neural interaction, has been explicated. Briefly, stimulus interaction refers to the notion that the habit or inhibitory loading of a component acquired in one compound will be reduced when that component occurs in another compound which consists of components other than those contained in the conditioning compound. The amount of reduction in the loading is said to be

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Charles C. Spiker an increasing function of the average dissimilarity of the corresponding components in the two compounds. Certain implications of the hypothesis were made explicit and compared with the outcome of several experiments. Particular attention was given to research with children in an attempt to determine the feasibility of extending the theory beyond data collected from infrahuman subjects. REFERENCES Birch, D., & Vandenberg, V. The necessary conditions for cue-position patterning, J. exp. Psythol., 1955, 50, 391-396. Bitterman, M. E., & McConnell, J. V. The role of set in successive discrimination. Amer. J . Psychol., 1954, 67, 129-132. Hoyt, J. M. Effect of similarity of reversal cues on learning of successive stimulus reversals in children. Unpublished master's thesis, State Univer. of Iowa, 1960. Hoyt, J. M. Serial reversal and conditional discrimination learning in children. Unpublished doctoral dissertation, State Univer. of Iowa, 1962. Hull, C. L. Principles of Behavior. New York: Appleton-Century-Crofts, 1943. Johnson, B. The effect of training on cue-position patterning in discrimination problems. Unpublished doctoral dissertation, State Univer. of Iowa, 1962. Jonckheere, A. R. A distribution-free k-sample test against ordered alternatives. Biomeirika, 1954, 41, 135-145. Lashley, K. S. Conditional reactions in the rat. J. PIychol., 1938, 6, 311-324. Lawrence, D. H. Acquired distinctiveness of cues: I. Transfer between discriminations on the basis of familiarity with the stimulus. I. exp. Psychol., 1949, 39, 770-784. Lipsitt, L. P. Simultaneous and successive discrimination learning in children. Child Deuelpm., 1961, 32, 337-347. Loess, H. B., & Duncan, C. P. Human discrimination learning with simultaneous and successive presentation of stimuli. J. exp. Psycbol., 1952, 44, 215-221. MacCaslin, E. F. Successive and simultaneous discrimination as a function of stimulussimilarity. Arner. J. Psyrhol., 1954, 67, 308-314. Price, L. E. The effect of the similarity of irrelevant stimuli on performance in discrimination learning problems. Unpublished master's thesis, State Univer. of Iowa, 1959. Spence, K. W. The nature of discrimination learning in animals. Psychol. Rev., 1936, 43, 427-449. Spence, K. W. The nature of the response in discrimination learning. Psychol. Rev., 1952, 59, 89-93. Spence, K. W. Behavior Tbeopy azd Conditioning. New Haven: Yale Univer. Press, 1956. White, B. N., & Spiker, C. C. The effect of stimulus similarity on amount of cueposition patterning in discrimination problems. J. exp. Psychol., 1960, 59, 131136.

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THE DEVELOPMENT OF “OVERCONSTANCY” IN SPACE PERCEPTION

Joachim F. Vohlwill DEPARTMENT OF PSYCHOLOGY, CLARK UNIVERSITY

I. THE PROBLEM OF “OVERCONSTANCY” IN SPACE PERCEPTION . . A. THE OVERCONSTANCY PHENOMENON . . . . B. THE EVIDENCE FOR OVERCONSTANCY IN ADULTS . . . C. DETERMINANTS OF OVERCONSTANCY . . . . . D. THEORETICAL SIGNIFICANCE OF OVERCONSTANCY . . . E. OVERCONSTANCY AS A PROBLEM FOR A DEVELOPMENTAL PSYCHOLOGY OF PERCEPTION . . . . . . . . .

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11. CONSTANCY AND BEYOND: A SURVEY OF THE DEVELOPMENTAL LITERATURE . . . . . . . . . . . . . . . . . . A. AGE CHANGES IN SIZE CONSTANCY . . . . . . . . B. AGE CHANGES IN THE PERCEPTION OF DISTANCE RELATIONSHIPS . . . . . . . . . . . . . . . . . C. DISCUSSION . . . . . . . . . . . . . . .

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AN INVESTIGATION OF THE DEVELOPMENT OF OVERCONSTANCY IN DISTANCE PERCEPTION . . . . . . . . . . . . . A. BACKGROUND AND PURPOSE . . . . . . . . . . B. METHOD . . . . . . . . . . . . . . . . C. RESULTS AND DISCUSSION . . . . . . . . . .

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V. A NOTE ON RESEARCH STRATEGY IN THE STUDY OF THE DEVELOPMENT OF PERCEPTION . . . . . . . . . . . . . . 307 REFERENCES

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I. The Problem of “Overconstancy” in Space Perception’ A. THEOVERCONSTANCY PHENOMENON The problem which is at the core of this paper concerns a phenomenon observed in the perceptual functioning of the adult. If it is nevertheless appropriately discussed in a volume devoted to research in the field of child development, this reflects the writer’s belief, as well as that of other research workers, that a developmental approach to the analysis of this phenomenon may contribute significantly to its clarification. At the same time tracing the developmental history of its formation should be of relevance for the study of perceptual development generally, and for certain theoretical issues arising in this area of behavioral development in particular. What is meant by the term, “overconstancy ?” Constancy, in visual perception, refers to the tendency for the perceived sizes, shapes, colors, etc. of objects to remain relatively invariant, regardless of changes in the sizes, shapes or colors of their retinal images-a tendency which Thouless (1931) has described as a “regression to the real object.” On occasion, however, this “regression” may overshoot the mark, going beyond the real object, i.e., the observer may show a bias to perceive an object as distorted in a direction opposite to that which would conform to the retinal image. Such a bias is referred to as overconstancy. It can best be illustrated with reference to the perception of size-at-a-distance, where this phenomenon has been observed most consistently; here it manifests itself through errors of a overestimation of the sizes of objects located far from the observer, relative to the sizes of near objects.

B. THEEVIDENCEFOR

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Evidence for the reality of this phenomenon has been steadily accumulating over the last 20 years at least, although it is only in more recent years that it has been taken seriously. Thus, in one of the earliest studies reporting data in conformance with such a bias (Holway and Boring, 1941), the authors were inclined to explain it away, by attributing it to an assumed space error, representing an artifact of the particular experimental situation. At present, however, the phenomenon seems to be established beyond any reasonable doubt, at least for the perception of size and distance relationships, which are the subject of our present concern. It has appeared under the most varied experimental conditions: at distances as short as 3 f t (Wohlwill, ‘The writer is indebted to Morton Wiener for a criticaI reading of the manuscript and his helpful comments and suggestions concerning it.

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“Ouerconstancy” in Space Perception 1763), as well as at distances of up to 4000 f t (Gilinsky, 1755); in photographic stimulus fields (Gibson, 1747; Sonoda, 1761), as well as under threedimensional field conditions; in stimulus fields devoid of structure (Whitehouse and Gruber, 1757), as well as in highly structured fields. Thus, while much work remains to be done on the conditions affecting the phenomenon (and the mechanisms underlying it are as yet fairly obscure), it is evident that there is a problem worth investigation here, and one which, as we shall see presently, is of no little theoretical significance. But before turning to this question, it may be helpful to examine more closely some of the determinants of the phenomenon, in so far as they can be specified at present.2

C. DETERMINANTS OF OVERCONSTANCY 1. Instructions Perhaps the most important variable affecting the manifestation of overconstancy in judgments of size and distance is the type of judgment which Ss are asked to make. This conclusion is indicated by the work of Carlson (1760; 1762) , who has demonstrated an interesting, though almost paradoxical fact: When observers are asked to make “objective” judgments, i.e., directed towards what they believe to be the true, physical size of the object, overconstancy becomes the rule; if, on the other hand, they are asked to adopt a “phenomenal” attitude, i.e., to judge the size of the object as it appears to them, the judgments are actually much closer to veridicality, conforming very nearly to perfect constancy. In the second of Carlson’s studies cited, furthermore, instructions designed to enhance the role of intellectual processes, by suggesting to S that he bear the perspective relationship in mind in making his judgments (i.e., making a match that would conform to the apparent convergence of lines connecting the standard and variable stimuli in the distance) resulted in an exaggeration of the overconstancy found under normal “objective” conditions. These findings suggest that overconstancy is the result of a judgmental, cognitive-order mechanism, by which S in some sense compensates for the distortion of the size and distance relationships as projected on the retina, or at least imposes a correction on the phenomenal sizes and distances.

2. Distance If overconstancy does in fact represent such a compensation for the “shrinking” of sizes and linear extents with increasing distance at the retina, one might ‘ A more comprehensive coverage of the role of these and other determinants in research on size and distance perception is contained in the papers by Denis-Prinzhorn (1961) and Lambercier (1946a,b). See also the papers by Epstein et al. (1961) and by Vurpillot (1956), for a discussion of the relationship between size and distance perception, a problem which we will not attempt to deal with here.

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Joachim F. Wohlwill expect that this would become progressively more difficult to achieve as distance increases, so that at very large distances overconstancy would no longer be found. Some support for such an effect of distance may be found in the study by Chalmers (1952), who for one of his experimental conditions found overconstancy up to 50 ft, changing to underconstancy at 80 and 120 ft. This study was, however, carried out under conditions of strongly reduced stimulation. For very similar conditions Tada (1956) has shown overconstancy in distance perception to decrease with increasing distance. Utilizing photographic stimulus materials, Gibson (1947) likewise found a change from overconstancy to underconstancy in size judgments, as distance increased from 112 to 448 yd. On the other hand, under the openfield conditions which had provided the photographic stimulus fields just referred

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Pig. 1 . ‘Objective’ and ‘retinaP marches as a function of distance, expressed as ratios of size of variable to size of standard to which it was eqgated. (From Gilinsky, 1955. Reproduced by permission of American Journal of P.rychology.)

to, Gibson found that the amount of overconstancy remained essentially invariant over the same range of distances. I n at least two studies, furthermore, perceived size has been found to increase with distance under optimal viewing conditions. Smith (1953) observed a change from underconstancy to overconstancy as distance varied between 16 and 320 ft; a similar but more striking trend emerged from Gilinsky’s (1955) study, in which the role of distance was investigated over an even longer span, Gilinsky‘s results are shown graphically in Fig. 1, which also includes the results obtained under instructions to match for projective, i.e., retinal size; the two contrasting empirical curves attest to the observers’ ability (High-school students, in this case) to differentiate between the two kinds of tasks demanded by the instructions. 3. The Role of the StinZulus Field, and of Cues t o Depth Overconstancy typically arises in situations affording adequate cues to distance. In relatively “impoverished” stimulus situations, on the other hand, where a

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rrOverconstancyJ’in Space Perception deliberate effort is made to eliminate such cues, judgments of size tend to conform to the “law of the retinal angle,” i.e., constancy disappears (Holway and Boring, 1941). It seems plausible, in fact, to attribute the general failure to find overconstancy (or even any close approach to constancy) in the judgment of shape-at-a slant, or of brightness under varying illumination, to the generally rather impoverished conditions under which most of the classical work on shape and brightness constancy has been carried out. At the same time there is some evidence that, as long as the cues to depth are adequate to allow the observer to structure the situation three-dimensionally, overconstancy will result. In particular, with respect to the judgment of distance, Whitehouse and Gruber ( 1957) have found maximal overconstancy (settings of the apparent midpoint displaced toward the rear of the distance being judged) under conditions where the ground separating the two objects defining the distance was not even observable; when this ground, consisting of a checkerboard pattern, was in the field of view, overconstancy still prevailed, but to a reduced extent. The writer, in research on the perception of distance (Wohlwill, 1963) has similarly found considerable amounts of overconstancy in stimulus fields devoid of any texture or patterning. (Further information on this point is contained in the report of the developmental study in Section 111 of this paper.) As far as the specific role of binocular cues is concerned, they do not seem to affect overconstancy noticeably in either direction, provided other cues to distance are available. In Holway and Boring’s (1941) study, there was some tendency for monocular observation to result in a closer approach to constancy, as compared with the overconstancy found under binocular conditions. I n the studies on distance perception by Whitehouse and Gruber (1957) as well as by the writer (Wohlwill, 1963) no significant difference between monocular and binocular viewing conditions could be detected. It is only under reduction conditions that monocular viewing results in a marked drop in constancy (Chalmers, 1952; Hastorf and Way, 1952; Tada, 1956). Significantly, all three of these studies give evidence of overconstancy in varying degrees for binocular viewing, even in the absence of other distance cues. If one may be entitled to generalize from these findings, it could be argued that they provide further support for the cognitive, judgmental basis for this perceptual bias; otherwise one might expect binocular cues and the structure of the stimulus field to play a more important role in its manifestation. 4. Methodological Factors

One factor which has been shown to play a very important part in determining whether, and to what extent overconstancy will be in evidence in judgments of size-at-a-distance is the relative positions of the standard and variable stimuli (assuming a standard and a series of variables are employed to measure

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Joachim F . Wohlwill perceived size, as they almost invariably are). It appears that there is a consistent bias towards overestimation of the standard stimulus, as shown by comparing judgments made with the standard close to S and the variable far with those made with the positions of standard and variable reversed. The result is invariably an apparent heightening of constancy, or overconstancy, under the latter condition (Akishige, 1937; Chalmers, 1952; Piaget and Lambercier, 1943b; 1956; Smith, 1953). On the other hand, when the standard is located near the subject and the variable at a distance, this bias will result in an apparent reduction of constancy, and may on occasion be potent enough to bring the judgment below the level of perfect constancy. It is essential, in other words, to obtain size matches under both near and far positions of the standard, and to average the data obtained from rhe two conditions (or else to forego the use of a fixed standard altogether). A further methodological consideration relates to the method of presenting the variables. The most typical method used is to present a single variable, adjustable in height, or to present a series of variables one at a time, by the methods of limits or constant stimuli. In some studies with children, however, as well as occasionally with adults (Gibson, 1947) a method of serial presentation of the variables has been employed, 5’s task being to select the variable stimulus from the series which is most nearly equivalent to the standard. This method appears, in general, to reduce deviations from constancy, in whatever direction. However, since our knowledge concerning the role of this factor is derived mainly from the developmental literature, further discussion of it is best left for the review of that literature in Section II of this paper.

D. THEORETICAL SIGNIFICANCE OF OVERCONSTANCY A brief discussion of the implications of the overconstancy phenomenon for theories of space perception should help not only to appreciate its significance, but also to bring into sharper focus the relevance of the study of of the developmental aspects of this problem which will be the subject of the sections to follow. The significance of this bias in perceptual judgments resides, first of all, in its implications for the issue of the veridical or nonveridical nature of our perceptual processes. The belief in veridicality occupies a central place in the theoretical conception of perceptual learning advanced by Gibson (Gibson, 1959; Gibson and Gibson, 1955), and in particular in his psychophysical theory of space perception (Gibson, 1950; 1959). Gibson maintains that the individual typically has available to him a complex array of stimulation transmitted through the retina, which can provide a fully adequate and effective

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“Overconstancy” in Space Perception basis for constancy, for instance, without requiring the intervention of assumptions, hypotheses or inferences introduced by the observer. While not denying the existence of cases of illusory perception, these are regarded as exceptions to the general rule, which is the psychophysical correspondence between the physical environment and the percept. I n the area of space perception in particular, this psychophysical correspondence manifests itself in the constancies of size and distance. Deviations from this veridical norm are granted, but only in terms of variable errors, i.e., the observer may be limited in the fineness of his differentiation of relevant stimulus variables. In fact, it is on this dimension of differentiation that perceptual learning is primarily thought to take place: perception becomes more highly differentiated, and therefore more specific. Constant errors, such as reflected in overconstancy, are not readily handled in this formulation, and it is significant that Gibson has thus far failed to deal with this problem, or even to give it explicit recognition. AS Gilinsky (1955, pp. 115 ff.) has argued quite persuasively, however, the consistent findings of overconstancy not only belies the postulate of veridicality as a characteristic of sizes and distances in perceptual space, but, in view of its patent judgmental basis, throws in doubt the usefulness of the concept of a “visual world” such as Gibson envisages, which is directly given to the observer, by virtue of the richness of the stimulus input present in our everyday environment. Yet if overconstancy creates a difficult problem for Gibson, he is not alone in this regard. Consider, for instance, the approach which the transactionalists have taken in this area, as represented by the work of Ittelson (1951; 1960). The functionalist position of Ittelson and his associates, with its stress on the essential indeterminancy of the stimulus correlates for a given percept, and on the role of “bets,” “weighing of cues” and assumptions made by the perceiver in arriving at a particular percept, is clearly in sharp disagreement with that of Gibson in its interpretation of the basis for the perception of spatial relationships (cf. Gibson and Gibson, 1955). Yet, except for a casual mention of the finding of instances of overconstancy, Ittelson (1960) likewise ignores this phenomenon as a problem requiring explanation. It is true that Ittelson is much more ready to admit of nonveridical perception; indeed he repeatedly points to its prevalence under many conditions, and even suggests that constancy as such should be regarded not as a force making necessarily for veridical perception, but rather as directed towards maintaining the individual’s perceptual world as nearly in accord with his past experience as possible (Ittelson, 1951). Nevertheless he fails in any sense to handle the kind of consistent judgmental bias, arising under ordinary, everyday conditions of stimulation, which overconstancy represents, nor is such a bias easily reconcilable with the transactionalist emphasis on the general adaptiveness of our perceptual processes (cf. Gilinsky, 1955).

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Joachim F. Wohlwill The direction of this bias further goes counter to the views of Brunswik (1933) and Thouless (1931), which interpret judgments made in a constancy situation as a compromise between two “poles,” the retinal stimulus, and the real or physical object: overconstancy clearly falls outside of the range encompassed between these two poles. In fact, Carlson (1962) feels on the basis of his data that “size constancy represents the natural midpoint, rather than one extreme of the range G f experimentally-obtained relationships between perceived-size and object-size’’ (p. 72). It appears, then, that no current theory of space perception is able to do full justice to the overconstancy phenomenon. One theorist, however, who has at least given explicit recognition to overconstancy and has tried to come to grips with its significance is Piaget (1961); in fact, his laboratories are the sourh for a good share of our knowledge concerning this phenomenon, and especially its developmental aspects. Piaget’s attempts to develop a consistent theory of space perception and to account for averconstancy in adults have remained somewhat sketchy and unconvincing; nevertheless his analysis of the judgmental situation involved in a perceptual constancy task and his model of psychophysical judgment in general may be of promise in directing us towards a more satisfactory view of overconstancy. Relevant in particular are the probabilistic character of his model of perceptual comparison, with its stress on the pervasive constant errors arising in any comparative judgment; his concept of “compensations” resulting from successive fixations on different portions of the stimulus field (e.g., the standard and the variable) and his general formulation of “perceptual activity” as an outgrowth of the cognitive maturation of the individual (cf. also Wohlwill, 1962a). Piaget has, furthermore, realized the significance of this phenomenon for the study of perceptual development; thus we will have occasion to delve further into his work on this problem and his formulation of it in subsequent portions of this paper.

E. OVERCONSTANCY AS A PROBLEM FOR A DEVELOPMENTAL PSYCHOLOGY OF PERCEPTION There are a variety of questions arising with respect to the overconstancy phenomenon which appear most readily answerable through developmental investigations, or concerning which developmental studies can provide directly relevant information. To begin with the most obvious one: is there a developmental history to this phenomenon, or does it emerge full-blown at the earliest point at which constancy can be meaningfully measured? If the latter were to be found the case, a somewhat different interpretation would persumably be placed on the phenomenon than if it were to be shown to be the endproduct of a developmental process.

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“Ovewonstancy” in Space Perception On the assumption that such developmental changes do take place, a further question arises : does overconstancy represent a bias gradually developing from an original neutral point (i.e., constancy), or is there a transition from under- to over-constancy? If the latter, is there any particular significance attached to the point at which the transition takes place, and does the transition proceed gradually or in spurts ? Answers to such developmental questions should clarify the role of vetidicality in perceptual development and the meaning of the departures from veridicality which may be found at different age levels. It is also worth while to look for interactions between developmental level and variables relating to the experimental situation, with respect to constancy judgments. For instance, if age differences were found to be maximized under the same conditions which are required to produce overconstancy in adults, and minimized under conditions in which this bias is attenuated, this might be taken to support an interpretation of overconstancy in cognitive terms. Similarly, determination of the correlates of age changes in this area could provide information of value. Thus one might ask whether these changes are intimately associated with changes taking place in the area of the child’s conceptualization of space, or in similar cognitive functions, or whether there is perhaps a closer relationship to changes in general judgmental processes, manifested in diverse perceptual tasks, or alternatively, with changes in functions from the general-intelligence area. The answers to such correlationaldevelopmental questions would clearly be of direct relevance to an understanding of the possible basis for overconstancy, as found in adults. The foregoing discussion, it is hoped, will indicate something of the contribution which the developmental literature in this field, to be reviewed presently, can make to this problem. The reader should be forewarned, however, that he will not find all, or even any large portion of these questions answered on the basis of the developmental evidence thus far available. Rather, the consideration of the ways in which developmental studies can be of value in this area may provide guidelines for the examination of the developmental studies which have been undertaken on this problem.

XI. Constancy and Beyond: A Survey of the Developmental Literature Since our primary concern in this paper is with the developmental processes that culminate in overconstancy, we will limit this survey of the literature to studies in which the degree of constancy or deviation from it was measured, typically through some type of psychophysical method. This restriction necessarily leaves out of account the work on constancy, and on space perception

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Joachim F. Wohlwill generally, at very early age levels. For an account of such studies, the reader is referred to the author’s review of the perceptual-development literature (Wohlwill, 1960).

A. AGE CHANGESIN SIZE CONSTANCY 1. Main Age Trends in Constancy A. Beyrt’s Experiment. Systematic research on size constancy in children seems to have been launched with the investigation by Beyrl (1926) , which in many respects still stands as a landmark in this field. It is unique in at least three respects: the use of the method of constant stimuli, whose laborious and time-consuming character has caused it generally to be shunned by developmental investigators; the systematic variation of distance between standard and variable, and the extension of the age scale downwards to the age of 2 (!). 5 s were 75 children between the ages of 2 and 10 years, as well as 5 adults. The experiment took place indoors under normal illumination; the standard was shown at 1 meter from S, and the variable at any one of seven distances, between 2 and 11 meters. The instructions asked S to indicate which of the two stimuli shown at any time was the largest. Since the use of the constant-stimulus method involved a large number of judgments for the determination of a PSE, and since 14 separate PSE’s were obtained from each child (for each of 7 distances, and 2 types of stimuli, cubes and discs), the experiment had to be spread over a number of sessions (apparently 21 for each child, each between 7 and 10 min long). Yet, according to the author, the children’s interest and motivation was maintained at a high level. He does report that the results of 19 of the younger Ss for the discs and 1 2 for the cubes had to be discarded, since they were too inconsistent to permit the calculation of a PSE, so that there was undoubtedly a certain amount of selection at the early age levels. Nevertheless, in the light of the remarkable internal consistency of the results obtained, this study stands as a demonstration of the considerable degree of precision in psychophysical judgment obtainable from even very young children, suggesting that the method of constant stimuli may be both more feasible and more profitable in developmental research than commonly realized. Since the pattern of the results was very similar for the two types of stimulus objects used-discs and cubes-only the former will be considered. Figure 2 shows the mean size of the variable perceived equal to the standard, at each age level, for each distance of the variable from the observer. It indicates a fairly regular trend towards increasing constancy with age, with the 10-year olds and the adults reaching near-perfect constancy for all distances. The results point further to the important role of distance, in interaction with age.

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rrOverconstancy”in Space Perception The younger the child, the greater the extent to which perceived size decreased with increasing distance, i.e., the greater the loss in constancy. While these data show no trace of overconstancy at the adult level, it should be borne in mind that only 5 Ss comprised the adult group, and that the conditions (standard near, variable far) worked against overconstancy, as pointed out previously. B. The Geneva Studies. As part of their extensive series of investigations of perceptual processes at different age levels, Piaget and his associates in 18 -

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Geneva have undertaken a number of studies on size constancy. I n this section we will consider only those portions of these studies which represent a standard set of conditions, thus ensuring a fair degree of comparability among them. In subsequent sections these and other related studies will be discussed individually, focusing on the variables manipulated in each. The basic stimulus situation utilized in all of these studies (cf. Lambercier, 1946a, pp. 69 ff) consists of a flat surface, 4 meters in length, viewed from a 20 cm height. The standard stimulus, a rod 10 cm high, is mounted at a distance of 1 meter from S, and a similar variable rod is shown at a distance of 4

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Joachim F. Vohlwill meters. The latter is varied according to the “clinical-concentric” method (cf. Gibson and Olum, 1960, p. 316), in which variables larger and smaller than the standard are presented in irregular sequence, in order to establish a region of uncertainty, the midpoint of which is the PSE. As each variable is shown, S is asked whether it is larger, smaller or equal to the standard. The only variation in this standardized situation which we will be concerned with in this section consists in a reversal of the relative positions of standard and variable; this condition will be referred to as V-S, while the normal

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Fig. 3 . Size constancy at different age levels, according to studies from the Geneva laboratorie~. ( B a ~ e d on data in Denis-Prinzhorn, 1961; Lumberrier, 1946a,b; Piaget and Lumbercier, 19436; 1946; 1951; 19SG.)

condition will be designated as S-V. Figure 3 shows the results obtained from 6 separate experiments under the S-V condition and two under the V-S condition. In every case only the initial set of measures obtained for either condition is represented. Two points emerge clearly from an examination of these curves. First, there is an unmistakable developmental trend in the direction of increasing overestimation of the far object; second, the values for the two sets of data obtained from the V-S condition show almost invariably higher levels of overestimation than those obtained from the S-V condition. Although in none of these studies is information given concerning the statistical significance of

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“Overconstuncy” in Space Perception these differences between groups and conditions, their consistency across the various studies inspires some confidence in the reality of these effects. The differences between the data from the V-S and S-V conditions point to the presence of the error of the standard referred to in Section I. The results obtained for either condition separately cannot, therefore, be used to assess the absolute amount of constancy, or the presence or absence of overconstancy. In order to extract such information from these data, the results from the two conditions, as studied in Piaget and Lambercier (1943b; 1951, 1956) have been averaged. (The first study tested both conditions with the same Ss, while the latter two, though based on different Ss, are very closely comparable in every other respect.) The two sets of means at the different age levels thus obtained are presented in Table I, which also indicates the average extent of the error of the standard, found by reversing the sign of the V-S errors and averaging them with the S-V errors. In order to facilitate comparison between the two sets of means, the results for the 6-7 and 7-8 year-old groups in Piaget and Lambercier (1943b), have been combined. As Table I shows, there is near-perfect constancy, on the average, at about the age of seven, while the means for the older age levels move progressively TABLE I MEANERRORSOF OVERCONSTANCY AND OF OVERESTIMATION OF STANDARD AT DIFFERENT AGES (IN % OF STANDARD)“ Ages (years) Experiment

5-6

6 8

8-10

11-14

Adult

11.8

7.2 17.0

4.2

4.7 7.0

Overconstancy

P & L, 1943b P & L, 1951;1956

-4.1

.2 .8

10.5

Error of Standard

P & L, 1943b P & L, 1951;1956 a

4.7

3.9 3.0

7.5

Based on data of Piaget and Lambercier (1943b; 1951; 1956).

more into the overconstancy range. With respect to the error of the standard (i.e., the amount of overestimation of the standard over the variable, when near and far positions are combined), the trend is not as clear; the data here do not support Piaget and Lambercier’s (1956) contention that this error decreases with age, based largely on results obtained under rather different conditions in an earlier experiment (Piaget and Lambercier, 1943a), in which

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Joachim F. Wohlwill standard and variable were actually equidistant from S. Why the authors in their discussion of this question (Piaget and Lambercier, 1943b; 1956) were unwilling to derive a measure of this error directly from the data, as we have done here, is difficult to fathom. Conceivably they felt that there might be an interaction between the two constant errors involved here, i.e., that due to distance and that of the standard. Such an interaction would of course vitiate the additive procedure adopted in arriving at the values in Table I. I n the aggregate, then, these results not only indicate the consistent changes in constancy with age to be found under these conditions, but suggest the possibility that overconstancy may start developing already in the childhood period, rather than being a product of maturity. 2. Methodological Factors

All of the studies discussed thus far have involved some form of comparison between a standard and a series of variables shown one at a time. Burzlaff (1931), in his study of color constancy, had shown that both the approach to constancy and the presence or absence of age differences were to a large extent dependent on the use of such a method, as opposed to a supposedly more “natural” method in which the series of variables is shown simultaneously, arranged in order of magnitude. Burzlaff demonstrated a similar effect with respect to size constancy, though in his study age differences (between 4 and 7 years) were small even under single-variable presentation. Akishige (1937), on the other hand, found that in a situation which is the reverse of Burzlaff’s (standard shown in an ordered series, variable presented singly) marked age differences and a general loss in constancy are produced. On the basis of this and similar work on color and shape constancy, complementing that of Burzlaff, Akishige concluded that it is not constancy as such that undergoes a developmental change, but rather the ability to interrelate objects in perceptual space in a relatively unstructured stimulus field. A rather different interpretation of these results is suggested by Lambercier (1946a), who has explored the effects on constancy and age differences in constancy of a variety of conditions of presentation of the variable stimulus. He notes that in Burzlaff’s work with the method of serial presentation of the variable, the size of the standard nearly coincided with the middle of the variable series, and such errors as did appear were in the direction of this midpoint. Accordingly, the results obtained may not reflect greater size constancy under these conditions, but rather a central-tendency effect, tending to bias judgments towards the middle of the series. His own results confirm this hypothesis in fairly dramatic fashion. He employed seven different comparison series, whose midpoints varied from 7 cm to 16 cm, the standard remaining constant at 10 cm. There was a resulting

2 78

“Overconstancy” in Space Perception systematic shift in the PSE’s, which over the same series varied between 8.6 and 12.7 cm for the adults, and over even wider ranges in the children. Again, the series whose midpoint was 10 cm produced near-perfect constancy at all age levels. There is unfortunately a serious bias in these data, due to the fact that for the more eccentric comparison series the POE was very close to, and in one case actually beyond the most extreme value in the series. This resulted in a certain number of cases of Ss’ refusing to select any element of the variable series as equivalent to the standard. Since these cases were simply excluded from the calculation of the means, these are systematically biased, the effect being to exaggerate the apparent central tendency effect. The “refusal rate” itself increased with age, furthermore, so that the age differences observed here (i.e., apparent greater central tendency effects in the younger children) are difficult to interpret. Nevertheless the effect as such is probably a real one, since evidence for it was found also with a much larger comparison series, which did not give rise to any such refusals. These results thus indicate the danger of artifactual errors introduced when the variables are presented simultaneously in an ordered series. Lambercier also utilized a procedure analogous to the method of limits, but with several variables being presented simultaneously in a gradually changing series; the task was to compare the standard to the middle of the series of variables at every turn. This method yielded results closely similar to those obtained with presentation of the variables one at a time, whether by a standard method of limits, or by the clinical-concentric method (whose results are given in Fig. 3 ) ; with all these methods constancy steadily increased with age, although never moving into overconstancy. The S-V situation common to each of these conditions would of course have militated against overconstancy. The percentage of Ss showing overconstancy, furthermore, averaged over several different measures, ranged from 0% at age 5 to 24% in the adult group. 3. The Role of the Structure of the Field According to Akishige’s (1937) hypothesis referred to above, i.e., that it is not constancy as such, but rather the perceptual structuring of the field that changes with age, the degree of structure present in the field in which the size judgments are made might be expected to exert a differential role at different age levels. But investigators in this area have rarely subjected this variable to systematic manipulation, so that little information relating to the nature of such an interaction, if any, exists. There are, however, two studies of some relevance to this question. Lambercier (1946b) investigated the effect on size matches of presenting a series or reference objects in 5’s field of view, in 5- to 8-year-old children

2 79

Joachim F. Wohlwill and adults. Four conditions of structure were employed: control (the standard unstructured condition used in the previous studies); weak ( 4 rulers were placed at equal intervals horizonally, and off-side with respect to the standard and variable); medium ( 4 vertical rods, varying in height, were substituted for the rulers); strong ( 4 rods were similarly deployed, but all equalled the standard in height, S being alerted to this fact). The main finding was that none of these experimental conditions affected the size matches very markedly, except that under the strong-structure condition the adults were generally able to make an errorless match. (Since for the adults the mean algebraic error was small under all conditions, the main effect here was a marked reduction of the mean absolute error.) For the other age groups no particular effects due to the conditions of field structure were apparent. The role of the structure of the field in a somewhat different sense was studied in 8- to 16-year old children by Edgren (1953), utilizing two versions of photographs of an open field, somewhat similar to those employed by Gibson (1947), which were referred to in Section I. In both versions a stake (the standard) appeared at distances between 25 and 200 ft from the camera, and a series of stakes (the variables) appeared in an ordered row in the foreground; the full-cue slides showed the field in which the stimuli were photographed intact, while in the reduced-cue slides the field was covered up by masking tape, leaving only the stakes to be seen. Age changes for the full-cue slides were very irregular, with no marked constant errors in either direction in any group. As would be expected, the reduced-cue slides resulted in a general loss of constancy. But, suprisingly enough this loss significantly increased with age; indeed, for the youngest group there was virtually no difference between the two sets of slides. The significance of this finding is, however, obscured by the possible role of central-tendency effects, operating to bias the judgments towards the middle of the series of variables. In the present case, for the particular standards utilized, the net effect would have been to attenuate constant errors due to other factors. Thus the lack of increase in errors on the reduced-cue slides for the youngest children may merely reflect their greater susceptibility to these central tendency effects. Thus at the present the Gestaltist hypothesis that age changes in constancy arising in relatively unstructured stimulus fields will tend to disappear in more highly structured fields (cf. Burzlaff, 1931, p. 218f; Akishige, 1937) remains still to be verified. 4. The Role of Distance

If we consider that the concept of size constancy refers to the tendency of perceived size to remain invariant mder changes in distance, it becomes apparent that, strictly speaking, it should be measured by obtaining size

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“Overconstancy” in Space Perception matches over a range of distances. The importance of doing so is illustrated in the results of Gilinsky’s (1955) experiment discussed earlier (cf. Fig. I ) , showing the extent to which over-constancy may vary at different distances. More to the point yet is Beyrl‘s (1926) finding of a marked interaction between distance and age level (cf. Fig. 2), which provides the most incisive evidence for an increase in constancy with age, in the sense just mentioned. In comparison, the significance of the series of studies by Piaget and Lambercier for the problem of constancy is rather more uncertain, since they have all been carried out with a single, fixed distance between standard and variable. One other study in which distance has been varied, and over a considerable range, at different age levels, is that by Zeigler and Leibowitz (1957). It was modeled closely after the classic study by Holway and Boring (1941); standards were shown at distances of 10, 30, 60, 80, and 100 f t from the observer, the size of the standard increasing in proportion to the distance; the variable was at a fixed distance, 5 f t from S. The study was limited to eight children, aged 7 to 9 years, and 5 college-age adults. It was found that, on the average, constancy fell off sharply with increasing distance for the children: as the distance of the standard changed from 10 to 100 ft, the matched size of the variable rose only from 2.0 to 7.6. (Constancy would of course have required a tenfold increase in size, i.e., from 2 to 20.) While the matches of the adults indicated a closer approach to size constancy, even their means started falling behind beyond the 30-ft distance. Thus as a group they failed to show overconstancy, even though with the standard at the far position the error of the standard, if any, should have favored it. The data for the individual Ss disclose, however, that one of the five Ss did show overconstancy at all distances, and a second did so at all but the 30-ft distance. In a very similar study comparing normal with mentally retarded adults, moreover, Leibowitz (1961) found slight overconstancy over this same range of distances in both groups. In two other experiments the distance between standard and variable has been varied, while keeping the total viewing distance from the observer to the far stimulus constant. Cohen et al. (1958) found that with the standard at 2 meters and the variable at 8 meters there was a definite increase in constancy with age between ages 7 and 17, but when the standard was moved back to 6 meters the means for all age groups were indistinguishable, and very close to the means of the oldest group. (No overconstancy was found under either condition; the error of the standard would have counteracted it here.) A study by Jenkin and Feallock (1960) yielded very similar results: with the standard held fixed at 320 in. and the variable shown at either 20 or 160 in., the latter condition resulted in a closer approach to constancy than the former. In this case, however, similar age shifts, from underconstancy at age 8 to overconstancy in adults (favored here by the position of the standard), were

28 I

Joachim F. Wohlwill found under both conditions. Bringing standard and variable closer together, as was done in these two studies, would of course be expected to result in a reduction of any constant errors related to the distance factor, and consequently of age differences in such errors. 5. Conceptual Factors and the Role of Intelligence Findings of differences in constancy associated with age, however interesting in and of themselves, will remain of somewhat equivocal significance unless and until they are bolstered by efforts to relate these differences to particular processes undergoing development. For instance, if it is hypothesized (e.g., Piaget and Lambercier, 1951) that the developmental changes observed in this area reflect the maturation of cognitive and intellectual functions, information should be sought relating age changes in these functions to the observed changes in perceptual judgments. The most fruitful approach here would seem to be to employ cognitive measures specifically related to the conceptualization of space, such as the tasks studied by Piaget and Inhelder (1956), or at least to particular intellectual processes postulated to be of relevance to performance in a constancy situation. To this writer’s knowledge, however, correlational data of this kind are not presently available. In fact even the information on the relationship between general intelligence and constancy in children is quite scant. One study that is relevant in this connection is the one by Jenkin and Feallock (1960), previously cited in connection with the role of distance. This study included, in addition to the children, adolescents and adults of average intelligence, a mentally retarded group, whose median MA (8:2) matched that of the children, and whose median CA (15 : lo) slightly exceeded that of the normal adolescent group. The results for the retarded group, for four different stimulus conditions, were in every case very closely comparable to those of the normal adolescent group, and significantly different from the normal children’s. This fact is interpreted by the authors as indicating that the age changes in constancy found in this study are not a function of intellectual processes. Leibowitz (1961) arrived at the same conclusion on the basis of his data, which similarly showed no difference between a normal adult group and an adult retarded group with a mean MA of 8.7 years. Yet, without wishing to minimize the significance of the finding that constancy is not affected by a considerably subnormal level of intellectual functioning, the possibility still remains that cognitive processes of a more specific type may be more closely related to size-at-a-distance judgments. It might be noted that there is at present little evidence to bear out the view that size constancy is negatively related to intelligence, as postulated by Locke (1938), on the basis of a survey of comparative data which suggested that

282

“Ovewonstancy” in Space Perception constancy might be higher at lower phylogenetic levels. In a somewhat similar vein we may refer to the view of Brunswik (cf. Klimpfinger, 1933, pp. 624 ff.) that increasing intellectual development supplants the need for a high degree of perceptual constancy, so as to account for a lowering of constancy after early adolescence found in brightness and shape constancy (for evidence of such a drop, cf. Wohlwill, 1960; Brault, 1962).3 It is interesting to note in this connection that in the area of shape constancy Leibowitz et al. (1959) have indeed found a much higher degree of constancy on the part of feebleminded Ss, as compared to normals. These authors directed their Ss towards analytic matches, however, which appear to prove difficult for Ss of low intelligence. In any event there is considerable evidence indicating that the various constancies obey rather different laws and are based on different processes (Leibowitz et al., 1956a; b). Thus the contrasting results with respect to the role of intelligence between Jenkin and Feallock (1960) for size and Leibowitz et al. (1959) for shape should not surprise. By the same token Thouless’s (1932) use of a composite index derived from judgments of size, brightness and shape, for which he found a slightly negative correlation with intelligence-test scores, appears questionable. 7 . T h e Relationship of Constancy to the Perception of Projective Size and

Perspective Of potential reIevance to the question of the basis for the developmental changes in size constancy is the relationship between the perception of objecive size on the one hand, and the perception of projective or retinal size, as well as that of perspective relationships on the other hand. It will be recalled (see Section I) that Carlson (1962) was able to order matches produced by instructions for projective size, apparent (phenomenal) size, objective size and perspective size on a continuum from extreme underconstancy to extreme overconstancy. Since these clearly represent alternative ways of perceiving space, the question arises as to the interrelationship between their respective developmental patterns. Evidence relevant to this question is provided by a pair of studies by Piaget and Lambercier (1951; 1956), in which objective- and projective-size judgments were compared in the same Ss. The results for the objective matches were already included in the account of the studies from Geneva (cf. Fig. 3). Brunswik and others would accordingly predict that, where size judgments can be based on knowledge or inference, rather than on immediate perception, older children will be able to make increasingly effective use of such information, and, not surprisingly, this has been verified in fact (Piaget and Lambercier, 1946; cf. also Wohlwill, 1962a). But this is a different question from the role of cognitive mechanisms in a purely perceptual task. It is this latter question with which we are concerned here.

283

Joachim I;. Wohlwill For the projective-size matches fairly elaborate procedures had to be adopted to ensure that Ss understood the instructions (see Gibson and O h m , 1960, for details). In the process, moreover, a considerable number of children in the two youngest age groups in the second study had to be eliminated. For those Ss who were retained, the first set of judgments obtained after the pretraining period disclosed an identical pattern in both studies: the 7year-olds show the nearest approach to correct projective size, though they still fall short by a factor of two; the judgments are deflected even further in the direction of objective size up to the age of about 12 years, while the adults occupy an intermediate position. In the case of the first study this age pattern held up following two sessions of practice with correction and demonstration of projective relationships, although these sessions did result in over-all improvement, i.e., a closer approach to size settings based on visual-angle matches. Similar practice periods in the second study also yielded improvement, but in this instance to an extent increasing with age; as a result the age trends themselves changed from the first to the third set of judgments, so that at the end the youngest Ss were making the largest errors. The over-all results from these two studies are interpreted by Piaget (1961, pp. 271ff.) as reflecting a more immediate perception in early childhood of projective size, unencumbered by the intrusion of the physical size of an object, as given by awareness of its distance. According to Piaget, as the chiId’s conception of space becomes more firmly established during later childhood the perception of objective size comes to dominate over and interfere with such a direct perception of projective-size relationships; finally, in adolescence and adulthood the latter “recovers” to some extent by dint of mediation through intellectual processes, based on an understanding of perspective relationships. However post-hoc, this interpretation has at least some surface plausibility, although the selective factor introduced by the elimination of a substantial number of the younger Ss indicates the need for caution in interpreting these age differences. Information regarding the within-groups correlation between the two judgments would also have been welcome in this connection. The puzzling fact remains, furthermore, that the youngest children were also very adept at making objective-size judgments (cf. Fig. 3 ) , so that it cannot easily be argued that they failed to perceive objective size effectively, or failed to differentiate between objective and projective size. Piaget’s argument that the upturn found in the oldest Ss results from their ability to respond to the laws of perspective likewise requires close scrutiny. Undoubtedly an understunding of the principles of perspective represents a late ontogenetic development; nevertheless it is to be noted that perceptual effects of depth attributable to perspective are actually more strongly in evidence in young children than in adults (Wohlwill, 1962b). Thus the

284

rrOverconstancyJ’in Space Perception difference between the older children and the adults seems to lie not so much in the eventual establishment of perspective relationships as an aspect of perceptual space, as in the more effective intellectual constructions based on the principles of perspective which the adults were able to employ in this situation. The demonstrations and corrected practice provided following the initial judgments would of course have strengthened these constructions.

8. Changes in Variable Error aizd in the Ifiterval of Uncertainty Thus far we have given exclusive attention to the changes with age in the coizrtant errors made in judgments of size. While this is clearly the question of prime relevance to the problem of overconstancy, there is another aspect to these judgments deserving of consideration, i.e., the degree of differentiation of the perception of size-at-a-distance at different age levels. This is of particular relevance to the formulation of perceptual learning, and by implication of perceptual development, advanced by the Gibsons (e.g., Gibson and Gibson, 1955), according to which the main kind of change occurring in perception as a function of experience is an increase in precision, specificity or differentiation. To answer this question, measures of the size of the DL, or the interval of uncertainty (IU), are needed. Not all of the studies previously cited include data of this type. This omission is especially regrettable in the case of Beyrl’s (1926) study, since his use of the method of constant stimuli would have provided a particularly sensitive measure of the size of the DL, for comparison at the different age levels. Our information on this point, then, comes largely from the studies by Piaget and Lambercier, whose clinicalconcentric method affords a rough estimate of the width of the interval of uncertainty (i.e., the interval in which judgments of equal, or inconsistent judgments of smaller and larger, are made). These show, almost without exception, very marked reductions in the width of this interval with increasing age. Thus, Lambercier (1946a) found values for this interval (in % of the size of the standard) decreasing from 35% at age 5 to 23% at age 7 and to 7% in the adult group. These values were obtained with the clinicalconcentric method at first testing; subsequent measures showed even larger age differences. These results were closely confirmed in two further experiments (Lambercier, 1946b; Piaget and Lambercier, 1946). Other experiments in this series (Piaget and Lambercier, 1943b; 1951; 1956) likewise show a general pattern of a decrease with age in this interval of uncertainty, although the differences are not quite as pronounced, and the age trend in some cases is more irregular. Still further evidence pointing in the same direction comes from the study by Cohen et al. (1958), who obtained measures of the IU based on

285

foachim F. Vohlwill the use of a method of limits; these decreased from 24% at age 5 to 12% at age 17 for one condition (standard at 2 meters), and from 19% at age 5 to 4% at age 17 for the other condition (standard at 6 meters). These data thus provide support for the increasing specificity or precision of perception emphasized by the Gibsons. In some cases (e.g., Lambercier, 1946a), the extent of the IU’s in the younger children is in fact so large, relative to the size of the constant errors, as to throw the very meaning of the latter in doubt. Thus, once it is realized that the lower boundary of the IU’s for the children is actually in the overconstancy range, while that of the adults closely approximates the POE (cf. Lambercier, 1946a, p. 117; also Gibson and Olum, 1960, p. 346), statements concerning an increase in constancy with age, based on averages of the upper and lower limits of the IU,may appear in a somewhat different light.

B. AGE CHANGES IN THE PERCEPTION OF DISTANCE RELATIONSHIPS The evidence concerning judgments of distance perception and their change with age can be surveyed much more quickly, since it is limited to only a very few studies. The relative neglect of this topic in the developmental literature seems to reflect a belief that the perception of distance is not easily investigated in children (e.g., Leibowitz and Hartman, 1959), which is belied, however, by the considerable degree of success which those who have made the attempt have encountered. To begin with, it may be helpful to clarify the distinction between size and distance. Both refer of course to linear extents in visual spaceindeed, as Gibson (1950, pp. 180 f.) has noted, it is scale rather than either size or distance by itself that remains invariant in perceptual constancy. The two dimensions differ in three separable ways, however. First, distance typically refers to “interspaces,” i.e., empty space between a specified set of points, while size refers to space filled by some object. Second, distance generally has reference to extents along a horizontal plane surface, while size is most frequently measured vertically with respect to such surfaces. Third, distances represent extents along a line of sight from the observer, while sizes are extents in a plane frontal to the observer. Of these various distinctions, the crucial one is clearly the last, since it corresponds to an important difference in the projective transformations of the two dimensions of the retina: whereas projected size varies as a simple inverse function of distance, projected extents along a longitudinal dimension are foreshortened, i.e., vary as the inverse square of distance. The other two aspects

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“Overconstancy” in Space Perception may, however, likewise be of some importance, as indicated in studies by Massucco Costa (1949) and Denis-Prinzhorn (1960). The former is concerned with the perception of filled and unfilled intervals in space. A standard horizontal interval (either delimited by rulers or cubes or filled by a solid stick), was shown at 1 meter, and a similar variable interval at 4 meters was to be adjusted to it. This corresponds, in other words, to the classical size constancy situation, except for the use of horizontal extents, and of unfilled intervals. For the empty intervals there was a considerable lack of constancy in a 5-year old group and near-perfect constancy in adults; in between these two extremes, however, the progression with age was rather irregular. For the filled intervals, on the other hand, all age groups were fairly close to constancy, except for a 7-year old group. The last condition represents actually a case of size perception in the horizontal plane. Denis-Prinzhorn compared this same condition with the more usual vertical direction used in size-at-a-distance judgments, for which the results were depicted in Fig. 3 . For the adults, the considerable overconstancy found under the vertical condition virtually disappeared under the horizontal condition; for 5-to-7-year old children, on the contrary, there was a greater amount of error (underconstancy) under the horizontal as compared with the vertical condition. This difference Denis-Prinzhorn attributes to the greater role of intellectual constructions (i.e., imaginary perspective lines) to which the adult Ss could resort under the horizontal condition. Denis-Prinzhorn’s main interest, however, centered on the perception of distance along the line of sight, which she studied by asking her Ss for bisection judgments of a 240-cm distance, the near end of this segment being 133 cm from S. This distance was divided up into two segments by means of a movable horizontal rod; 3’s task was to judge whether the near segment was larger, equal or smaller than the far segment, or vice-versa. The two kinds of judgments yielded somewhat different results : when the question was how the near segment appeared relative to the far segment, the midpoint was, for all age groups, placed considerably nearer to S than when the judgment was directed to the far segment. While this difference was indicated as significant only for the youngest group, it undoubtedly was so far all Ss combined also. This effect appears analogous to the error of the standard in size constancy judgments, associated with the position, near or far, of the standard. Our main interest is of course in the age trend exhibited in these bisection judgments, and in this respect the two conditions are quite consistent: both showed underconstancy (midpoint placed too near S) decreasing from the 5-7 year group to the 7-9 year group, and moving into overconstancy for the adults. It will be noted that this trend parallels very closely that found for the size judgments in this study (Fig. 3 ) , as in all of those from the Geneva

28 7

Ioachim F. Wohlwill laboratories. Thus the correlation between the two judgments becomes of interest, particularly in relation to the question of the interdependence between perceived size and perceived distance (cf. Epstein et dl., 1961). These correlations differed in a rather puzzling fashion for the two types of distance judgments: with the near segment as the basis of reference, their correlation with the vertical size judgments dropped from .49 in the youngest group to .10 at the two other age levels; very similar results were obtained with the horizontal size matches. For the distance judgments made with the far segment as referent, however, the correlations fluctuated quite irregularly in the various age groups, and remained nonsignificant throughout. Although Denis-Prinzhorn L

2Or

0 c

r"

I

2

4

6 Trials

8

10

12

Fig. 4. Changes in distance bisections aJ a function of practice, at different age levels ( a f t e r Denir-Prinzhorn, 1960. Reproduced by permission of Archives de Psychologie.)

is forced to rely on post-hoc arguments to explain this discrepancy, it should be noted that the age trend in the correlations found under the first condition was also shown in a similar pilot study in which the instructions did not direct S's judgment to either the near or the far segment as a referent. On the whole these data thus suggest that size and distance are more closely interdependent aspects of perception in young children, while at later age levels this interdependence decreases. Conceivably this change reflects the development in adults of preferential attention to certain types of cues for size judgments which may overlap only partially with those on which distance judgments are based. A final aspect of interest in Denis-Prinzhorn's study concerns the effects of practice on distance judgments. For a limited number of Ss these judgments were continued for a total of 10 or 12 settings. Figure 4 shows the results for these extended series.

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“Overconstancy” in Space Perception The interesting aspect of these findings is of course the general trend of the bisection judgments towards increasing overconstancy as practice progresses. This trend is, furthermore, most pronounced in the adult group; it also differs somewhat between the two conditions of judgment. The fact that it is greater with the far segment as a referent, which appears to represent a more difficult type of judgment (according to Denis-Prinzhorn’s observations), may be of some significance; as we shall bring out in Part IV of this paper, there are a variety of indications that difficulty favors overconstancy in adults. Lastly we come to a very recent study by Harway (1963), also dealing with distance judgments at different age levels. It is based on a method very different from Denis-Prinzhorn’s, and probably as a result the findings obtained are at variance with the latter’s. The procedure used in this study, carried out outdoors on a grassy field, involved a series of successive reproductions of the distance of a 1-ft standard along a line of sight receding from S, so as to yield a function relating errors in perceived distance to actual distance from the observer. This procedure has the major drawback that each judgment which S makes determines the starting point for the following judgment. Thus any errors made by a given S tend to cumulate; at least successive judgments cannot be regarded as independent of one another. Furthermore, the actual distances corresponding to each judgment vary from one S to the next, so that for a group of Ss the distance variable can only be represented in an ordinal sense, i.e., in terms of the ordinal position of each judgment in the series of successive judgments. The results, based on 5 age groups with median ages of 54, 7, 10, 12, and 23 years, are given in Fig. 5 . It will be noticed that errors of underestimation of the far distance progressively increase over the successive judgments, and that this is true to a more marked degree in the three youngest age groups. Although the limitations of the method just discussed should be borne in mind, the results do show a suggestive similarity to those found by Beyrl (1926) and more particularly by Zeigler and Leibowitz (1957) for size, indicating a progressive loss of constancy with increasing distance, which itself decreased with age. Harway also provides evidence to discount a hypothesis with Gilinsky (1960) had advanced previously, on the basis of similar results which she obtained in a pilot study, i.e., that increase in height with age provides the older Ss with increasingly effective perspective cues on which to base judgments of distance. Harway included two conditions of judgment in his study: in one S made his judgment at his normal standing height, while in the other his position was adjusted so as to provide a constant viewing height of 5 f t 6$ in. for all Ss. There were no significant differences at any age level associated with this viewing-height variable. The order of the conditions did, however, yield a significant effect: in all groups except the adults there was a

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Joachim F. Wohlwill

-

2

10 Years

4

6

8 10 12 14 Successive judgements

16

18

20

Fig. 5 . Errors in successive reproductions of a I - f t distance at different age levels. (After Harway, 1963. Reproduced b y permission of American Psychological Association.

reduction in error in the second series of judgments (irrespective of the particular viewing condition). While the basis for this improvement on the part of the children is difficult to specify, the failure to find overconstancy at any age level and the lack of change in the adult group suggest that this practice effect is probably not comparable to that found by Denis-Printhorn.

C. DISCUSSION The one conclusion which is abundantly supported by the developmental evidence surveyed in the preceding pages is that constancy with respect to the perception of size and distance undergoes a steady change with age away from the “law of the retinal angle.” The evidence is somewhat more contradictory, however, as regards two closely related questions: the extent of the lack of constancy in childhood, and the development of overconstancy in adolescence or adulthood. Here the studies seem to fall into two main categories. Those which have dealt with only a single distance, typically no greater than 4-6 meters, find a fairly close approach to constancy by the age of 6 or 7, and a change to overconstancy in later childhood or adolescence. Included here would be the entire series of studies from the Geneva laboratories, as well as that by Jerkin and Feallock (1960). The studies, on the other hand, in which

“Overconstancy” in Space Perception distance has been varied (Beyrl, 1926; Zeigler and Leibowitz, 1957; Harway, 1963) have disclosed much more considerable departures from constancy in the younger Ss, and to an extent increasing with distance. In the aggregate, the evidence might seem to suggest the following conclusion : perceived space steadily shrinks with increasing distance, but the shrinkage decreases with age, and in such a way as to result in an apparent expansion at distances close to the observer in the older 5s. The situation may be represented graphically as follows (Fig. 6) : The major difficulty with this hypothetical picture is that it cannot account for the evidence reviewed in Part I of overconstancy in adults at greater distances, comparable to those included in the developmental studies by Zeigler

Adults

s

Underconstoncy Older children

Young children DiSlQnCe from subject

Fig. 6. Hypotheticul function relating constancy t o distance at different age levels.

and Leibowitz and Harway which failed to show it. A particularly discrepant case is the study by Gilinsky (1955) (cf. Fig. I ) , who for a group of adolescent Ss found a definite expansion of perceptual space over very considerable distances. No obvious resolution of this dissonance in the state of the evidence suggests itself; further developmental data encompassing longer distances are needed here, especially in view of the quite perfunctory sampling at the older age levels in the studies by Beyrl (1926) and Zeigler and Leibowitz (1957) and the methodological difficulties noted in connection with Harway’s (1963) findings. The picture with respect to fairly short distances, on the other hand, is quite consistent, indicating a change from underconstancy in early childhood to overconstancy in adolescence and adulthood. A final note concerning the nature of the stimuli employed in all of these perceptual studies may be in order. They have generally been devoid of meaning, such as rods, triangles, circles, etc., whose nature clearly provided no clue to their true size. Their relative unfamiliarity, and the attendant artificiality of

loachim F. Wohlwill the task do not seem to have proved much of an obstacle to their use with even very young children (e.g., Beyrl, 1926) ; in fact, these Ss appear generally to enter into the spirit of the thing at least as readily as their more sophisticated, intellectualizing elders. Yet the effect has undeniably been to limit the scope of such research, particularly as it bears on the kinds of formulation of the nature of perceptual learning advanced by psychologists of the transactionalist and functionalist schools. It is probably no accident that the only empirical study on size-at-a-distance judgments in childhood utilizing familiar objects was inspired by Brunswiks functionalist approach, and by his advocacy of ecological representativeness in perceptual experimentation. This is a study by Dukes (1951), undertaken with a single 6-year-old child, who was asked for comparison judgments of the sizes of 14 pairs of objects, varying widely in size and distance from S. Constancy in this child was found to be very highly developed, as indicated by a correlation of .99 between judged and true size.

111. An Investigation of the Development of Overconstancy in Distance Perception4 A. BACKGROUND AND PURPOSE The study to be reported represents an extension of research on determinants of overconstancy in the space perception of adults. This research dealt primarily with bisection judgments over fairly short distances, with fields varying in texture; it was designed to establish more clearly the role of this variable in the perception of relationships in three-dimensional space, in the light of the emphasis placed on it in Gibson's (1950) theory of space perception, and to determine the stimulus conditions under which overconstancy seems to be favored. The choice of distance rather than size as the dimension of judgment in this research was dictated not only by the disproportionate attention given to the latter in previous deveIopmentaI work on space perception, but more particularly by the interest in the role of the stimulus field, which might be expected to reveal itself most directly in the perception of distance, and only more indirectly, if at all, in the perception of size. This focus on the role of the texture of the stimuIus field also led to the use of very short distances, so as "This investigation was supported by research grant G-16031 from the National Science Foundation. The assistance of Mrs. Doris Salzer in the conduct of the experimental work, and of Mr. Albert Kavanagh in the statistical analysis of the data is gratefully acknowledged. The author 'is also indebted to Mr. Henry Brown and Mr. Theodore Dumas, Principals respectively of the Adams Street and South High Schools of Worcester, Massachusetts and to the teachers and counselors of these schools for their cooperation in supplying facilities and subjects for the study reported here.

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r‘Overconstmcy” in Space Perception to permit the utilization of readily interchangeable stimulus fields, displayable within a constant, self-contained experimental setting. The chief outcome of the research carried out with adults (Wohlwill, 1963) was that over the distances employed (45 and 90 cm) consistent overconstancy prevailed, i.e., the bisection settings were displaced backwards of the true midpoint. This bias, furthermore, increased sharply during the course of S’s exposure to the stimulus situation. The texture of the stimulus field, on the other hand, influenced the judgments to only a fairly minor extent: a stimulus field devoid of any elements of texture yielded virtually as much overconstancy as fields with varying densities of texture elements. The only stimulus field for which there appeared to be a consistent effect was one in which the texture elements were arranged according to a highly regular pattern; this resulted in a significant reduction of the errors in the bisection judgments. It should be mentioned that these findings are based on monocular viewing conditions; however, it has been shown that binocular viewing does not change the judgments to any significant extent in this experimental situation. Turning now to the investigation of developmental changes in these distance judgments, it was designed with three major aims in mind: (a) To corroborate and extend the developmental findings of Denis-Prinzhorn (1960a) for a similar task, by studying the course of age changes in bisection judgments between the ages of about 6 and 16 years. (b) To investigate the possible interaction of age with the texture of the field. O n the assumption that young children may require more redundant stimulus information for perceptual judgments than adults (cf. Wohlwill, 1960; 1962a), it was hypothesized that age changes from underconstancy in early childhood to overconstancy in late adolescence would be maximal for unpatterned stimulus fields (i.e., in which the texture elements are arranged in a purely random fashion) ; as a corrolary, age differences should be decreased under redundant texture conditions, and the judgments should approach more nearly to veridicality. (c) To determine the interrelationship between the age changes taking place in judgments of distance relationships in this experimental situation with those to be found for other perceptual tasks, involving discrimination of depth and size-at-a-distance, and spatial relationships generally. The intent here was to try to secure information bearing on the basis for any observed changes in the distance judgments, and for the formation of overconstancy in particular.

B. METHOD 1. Apparatus

The apparatus used for the display of the stimulus fields is sketched diagrammatically in Fig. 7. A more detailed description of it is given elsewhere

293

Joachim F. Wohlwill (Wohlwill, 1963). Briefly, it consisted of a large viewing box, into which S looked monocularly through an eyepiece lined up with the center of the visual field. The field of view consisted of a brightly lit horizontal panel, set off against a neutral grey vertical background at the back of the box. Ceiling and sides of the box were blocked from S’s view by means of a screen. S further saw two red markers which appeared to be standing on the panel, and which defined the distance he was asked to bisect. These markers appeared at distances of 63 and 153 cm from the edge of the eyepiece; the front one was located near the front edge of the panel, which was just out of range of view for S,

L

103.5 cm

52.5crn

4

Fig. 7. Schematic picture of the experimental apparatus.

while the back marker was located directly in front of the rear edge of the panel, coinciding with the rear wall of the apparatus. The judgments were to be made by stopping a moving black pointer traveling along the length of the panel, very slightly off-center with respect to the markers. Movement of the pointer was by means of an electric motor. 2 . Stimulus Fields Two sets of stimulus panels (30 x 40411. sections of heavy white cardboard, which could be inserted into the apparatus through a slit in the side of the box) were utilized. Each set consisted of 6 panels, varying in the density and regularity of arrangement of the elements of texture (black stars) which were stamped on them. The 6 panels of each set comprised a “control” panel, which was left blank;

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“Overconstancy” in Space Perception three randomly textured panels, with low, medium and high densities of stars; a high-density semiregular panel, in which the stars were restricted to a limited set of columns, enhancing linear perspective; a high-density, regular panel, in which the stars appeared in a perfectly regular, evenly spaced matrix. These panels will be designated, respectively as C; L-Ran.; M-Ran.; H-Rau.; H-Sen., and H-Reg. (Further details of their mode of construction will be found in Wohlwill, 1963.) The second set of panels constituted essentially a replication of the first, except that the orientation of the stars varied randomly in the second set, while all stars in the first set pointed in a uniform direction, towards the back of the panel. Each S made judgments for all 6 stimulus panels, their order being varied according to a Latin-square design; for half of the Ss at each age level the first set of panels was used, for the other half the second set. Two judgments were obtained with each panel, one a~cendkg(pointer moving away from S), the other descending (pointer moving towards S) .

3. Imtructions and Pretraining Ss were instructed to say “stop” when they thought the moving pointer had arrived at the middle of the distance between the two markers. (This is thus a set for objective judgments.) If S was not satisfied with the position of the pointer when it was stopped, he was given an opportunity to revise his setting; in fact, E asked him routinely after each setting: “Is that it?” I n order to ensure that the children properly understood the instructions, the distance bisections in the apparatus were preceded by several pretraining tasks, consisting of bisections of lines drawn on a sheet of paper, as well as of a metal rod mounted on top of the viewing box. The latter task was carried out under conditions closely approximating the bisections required in the experiment proper: the distance to be judged was along a line receding from S, and the bisection was also made by stopping a moving pointer. This pretraining experience was designed not only to familiarize S with the task, but to reduce to some extent anticipation effects, tending to create large discrepancies between the ascending and the descending settings, which were expected to be particularly pronounced at the younger age levels. Accordingly, whenever S’s ascending and descending settings made on this pretraining task differed by more than 10 cm, this discrepancy was pointed out to him; he was asked whether the middle could be in both places (this was invariably denied) and thereupon the judgments were repeated, under instructions to stop the pointer more nearly at the same place both times. This generally had the effect of bringing the discrepancy between the two judgments below the 10-cm limit.

295

Joachim F. Wohlwill 4. Supplementary tasks In addition to the bisection judgments, Ss were also given several other perceptual tasks. Two of these involved judgments to be made from photographs reproduced in Gibson’s (1950) T h e Perception of t h e Vhual World. One required S to discriminate which of two photographs was taken from a height, rather than standing on the ground (there were two pairs of such photos, one of a highway, the other of a field; see p. 140 of Gibson’s book). The other involved judgments of size-at-a-distance, utilizing the photograph on p. 184 of the book, which shows a large expanse of terrain, featuring a white stake at a distance of 224 yd, to be compared to a row of comparison stakes arranged in order of size in the foreground. S was given two further tasks. One was designed to show whether he would represent linear perspective in a drawing (he was shown a drawing of a road, represented by an oblique line disappearing in the distance, with two trucks drawn in alongside the road, one towards the bottom drawn larger than the other near the top; S’s task was to draw a line to represent the missing side of the road). The other task was a measure of his susceptibility to the distorting effects of perspective in a two-dimensional drawing; it involved bisecting a segment of a line superimposed on a perspective transformation of a rectangular grid (cf. Wohlwill, 1962b, Fig. 2). 5. Subjects The main sample consisted of 5 groups of 24 Ss each, taken from Grades I, 111, V, and VIII, and XI. (The last was a volunteer group.) Twenty children from a Kindergarten class were also tested. Three of the latter were used as replacements for 3 Ss from Grade I who were discarded, on account of their very large average discrepancies between ascending and descending judgments (cf. below).

C. RESULTSAND DISCUSSION 1. Distance Bisectiom Table I1 presents the mean errors for the bisection judgments for each of the 5 main age groups, broken down by stimulus panels. Positive errors mean that Ss judged the midpoint to be back of its objective position (i.e., overconstancy) ; negative errors mean bisections to the front of the objective midpoint (i.e., underconstancy). The overall change with age in the judgments is shown graphically in Fig. 8, which also includes the data from the Kindergarten Ss and the adults of the original study, for purposes of comparison. (These last two groups are not entirely comparable to the rest, since order of presentation of the stimuIus panels was not completely counterbalanced in

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“Ouerconstancy” in Space Perception the former, and since the adults made bisections of other distances, in addition to the one on which the present data are based.) The results of the analysis of variance of these data are shown in abbreviated form in Table 111, including only terms significant beyond the .05 level. With respect to the uge variable, these results show a very considerable shift, significant beyond the .01 level, from slight underconstancy in the youngest TABLE I1 MEANERRORSIN BISECTIONJUDGMENTS AT

Mean CA (years : Age groups months)

6:lO First grade Third grade 8: 10 Fifth grade 11 :O Eighthgrade 13:11 Elevenchgrade l6:lO Combined

OF 90-CM

DISTANCE

FIVE AGE LEVELS(IN CM)

Panels C -1.32 .01

.74 2.84 6.54 1.76

L-Ran. M-Ran. H-Ran. H-Sem.

H-Reg.

-1.54 -.51 1.24 1.94 0.10 .65 3.72 2.18 6.70 5.80 2.10 2.01

-.90 1.18 .30

-.92 1.30 .75 2.96 6.71 2.16

-.06 1.21 .27 3.02 6.44 2.20

.43 4.25 1.05

Combined mean -.81 1.15 .47 2.52 6.07 1.88

TABLE I11 ANALYSISOF VARIANCE(ABBREVIATED) OF BISECTION JUDGMENTS

Source Age Linear Quadratic Ss within age group Panels Order Panels X age Panels X set Error (within Ss)

df

4 1 1 115

5 5 20 5 500

Mean square 997.88 3516.48 203.06 50.76 22.75 119.31 11.90 20.19 6.54

F

P

19.66 69.27 4.00

< .01 < .01 < .05

3.48 18.23 1.82 3.08

< .01 < .01 < .05 < .01

groups (Kindergarten and Grade I) to a very marked degree of overconstancy in the late-adolescent group (Grade X I ) . In fact, veridicality in this situation appears rather to decrease than to increase with age. Thus, although the generalizability of these results cannot be vouchsafed, we do find strong confirmation for the view that overconstancy as encountered in adults represents the end-point of a prolonged developmental process, in agreement with previous developmental work in this area.

29 7

Joachim F. Wohlwill The remarkable degree of overconstancy found in the late adolescent group requires comment. It should be borne in mind that Ss in this group volunteered to serve in this experiment, after their regular school hours. It thus seems likely that their level of motivation, and possibly their level of intelligence as well, was somewhat higher than the average; conceivably, these factors may have contributed to the somewhat anomalous results for this group. The texture variable likewise yielded effects significant beyond the .01 level, but these were concentrated largely on the H-Reg. panel, which over all age groups produced a substantial reduction in overconstancy relative to the other panels, in conformance with the results obtained in the earlier study

: IiY(\(&

$ 0

x-.

Adult

Grade

Fig. 8. Age changes in errors for bisedons of a 9 0 - m distance.

with adults. In the present case the drop of the values for this panel was confined for the most part to the two oldest groups. The interaction of the panels variable with that of age was significant at the .05 level, but any resemblance to the pattern originally hypothesized for this interaction, based on young children’s greater need for redundancy in the stimulus-input, is more apparent than real. The most pIausible interpretation of the findings with respect to the H-Reg. panel is that the even horizontal spacing of the rows of stars in that panel could be utilized as a cue by the older Ss, in a quasi-cognitive fashion (though it should be noted that all Ss were warned against trying to count the stars on this panel). Thus their high overall level of overconstancy was reduced, and brought down to a level more nearly resembling that of the younger Ss. At the same time the fact that the latter performed at a level dose to constancy even on the Control panel, the results for which differed little from the randomly textured

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“Ouerconstancy” in Space Perception ones, indicates that the texture variable is of fairly negligible importance in this situation. Two further aspects of the data are of interest. First, there was a highly significant practice effect, as shown in Fig. 9 ; it consisted in the main of a rise in the bisection settings from the first-presented panel to the following panel; subsequent changes were less regular. A similar pattern has been found in several studies with adult 5s; it suggests the establishment of a frame of reference which becomes stabilized as S becomes adapted to the experimental situation. It may be noted that this rise is particularly marked in Grade XI;

U

.-

I

I

1

1st

2nd

3rd

4th

Ordinal position of ponel

5th

6th

1st ponel repeated ot end

Fig. 9. Errors in bisection judgment as a function of the ordinal position in which each panel was presented, f o r Grades I, VII, V , VIII, and X I .

it is only from their second judgments on, in fact, that the exaggerated degree of overconstancy found for this group manifests itself. Marked developmental changes were also found with respect to the difference between the ascending and descending judgments. This “D-A factor” steadily decreased with age, from a mean of 7.10 cm for the Kindergarten Ss to a mean of 1.95 cm for the adults in the earlier study. The corresponding means for the intervening grades were 5.66 ( I ) ; 3.69 (111); 5.11 ( V ) ; 3.22 (VIII), and 3.01 ( X I ) . (These values do not include 5 Ss, 3 from Grade, I and 2 from Kindergarten, who were discarded due to their exceptionally large D-A values, i.e., >17 cm, averaged over the 6 panels.) These D-A scores are most likely a product of two separate factors, one, a perceptual one, representing 5’s lack of differentiation of the midpoint within a range of the distance continuum; the other, a response bias, involving anticipation tendencies which

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Joachim F. Wohlwill cause S to stop the moving pointer too soon. In any event the findings are in close accord with those reported in other studies, with respect to the width of the interval of uncertainty in young children. At the same time the finding that there was a substantial decrease in these D-A values from the first to the sixth judgment (the effect of order of panel being significant beyond the .001 level) suggests that more extensive pretraining might have served to narrow this interval, even at the younger ages. Brief mention might be made of the sex differences found for these judgments. While there was no over-all difference between boys and girls, TABLE IV RESULTSPOR SUPPLEMENTARY TASKS Judgments from photographs

Age group

N

Kindergarten Grade I Grade 111 Grade V Grade VIII Grade IX

20

24 24 24 24 24

Frequency of Mean size of correct dis- Mean perspecnear variable crimination of tive illusion Number of Ss equated to viewing height in bisection of representing 71-in. far std. 41-cm length perspective in (inches) Road Field (cm) drawing 53.8 48.2 52.6 61.4 59.8 72.6

7 11

20 22 22 24

10 13

14 15

20 24

2.7 3.5 4.4 3.7 3.9 2.2

5 8

14 10 19 14

there was a definite suggestion of an interaction between age and sex, with the girls showing higher scores than the boys up to the third grade, and a reversal of this pattern at the older age levels. This interaction did not, however, attain statistical significance. 2. Supplementary Results The results for the various supplementary tasks are summarized in Table IV. It may be seen that for most of the tasks there are substantial age changes, paralleling those found for the distance bisections. The means for the size-at-adistance judgments are in particularly close correspondence with those for the bisection data, although here the pattern is one of increasing veridicality with age. (Central-tendency effects may have been operative here, since S had to equate the standard to one of a series of simultaneously presented variables, but the frequency distribution of choices at the different age levels do not give

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“Overconstancy” in Space Perception evidence of any tendency for the choices of any group to pile up around the mean of the series.) In regard to the discrimination of viewing height from photographs, it is interesting to note that the two youngest groups operated at the level of chance, while by late adolescence (Grade XI) errors had virtually disappeared. There is also a suggestion that the linear perspective cues provided by the highway are responded to earlier than the texture cues provided by the field. As for the two tasks involving perspective, it is not surprising to find the representation of perspective steadily increasing with age; that is, there was an increasing tendency to draw the line indicating the side of the road at an angle to the other side, so as to show convergence. On the other hand, the perceptual effects of perspective on the judgment of distance in a two-dimensional plane appear to reach their peak at a fairly early age, and actually to decrease in late adolescence. The results here are in close agreement with those found in the author’s prior developmental study of the perceptual effects of perspective (Wohlwill, 1962b). In spite of the fairly consistent patterns of age changes among these different judgments, however, intercorrelations among the various measures, and in particular between the distance judgments and any of the other tasks, were invariably quite low and insignificant. Thus, even without partialling out the effects of age, the correlation between the bisection judgments and the photographic size matches was only .05. There was a somewhat higher association between the distance judgments and the representation of perspective on the drawing (rPbi = .28), but this too could be accounted for largely on the basis of the common relationship of these two variables to age. For our Ss in Grade XI only, one additional perceptual measure is available. These Ss were asked for a set of judgments of verticality in the dark, under conditions of bodily tilt (cf. Wapner and Werner, 1957). The interest of these judgments resides in the fact that in this situation there is a developmental change in the adjustment of the vertical, from an error in the direction of S’s own tilt in children to a bias in the opposite direction in adults, which appears to bear at least some surface similarity to the change from under- to overconstancy found in space perception. Thus it does not appear coincidental that our Ss also exhibited, on the average, a higher degree of compensatory error (verticality setting deflected in a direction opposite to that of the tilt of the body) than was found at a comparable age, as well as in adults, in Wapner and Werner’s study. Here again, however, there was but a zeroorder correlation between these verticality judgments and the distance bisections made by these same Ss. Finally, a measure of intelligence is available for all Ss in Grades 111, V, VIII and XI, in the form of scores on the group-administered Otis Mental Abilities test. The correlation of these test scores with the bisection judgments in the 4 groups was, respectively, -.42, -.23, -.38, and +.19. (Only the

301

Joachim F . Wohlwill first of these is significant, at the .05 level.) In order to determine the correlation for the 4 groups combined, the bisection values in each group were transformed into deviation scores from their respective means, so as to make them comparable to the intelligence scores which were likewise relative to each group. The resulting correlation was -.13, i.e., nonsignificant. The data thus again fail to provide any positive evidence of a relationship between general intelligence and perceptual constancy.

IV. Constancy and Overconstancy : A Reassessment I n this section we will attempt to pull together some of the main conclusions which the results obtained in developmental investigations of size and distance perception seem to warrant, and to bring out briefly their major implications for current conceptions of space perception, as well as of the nature of perceptual development. Perhaps the most important conclusion to emerge from the survey of the evidence is that the developmental changes occurring in this area of perception are not themselves based in processes in the individual’s immediate perception of the stimulus field, but reside rather in the mechanisms governing the judgmental process by which such perception is translated into responses in a psychophysical task. The distinction between perception and judgment remains, to be sure, as elusive as ever; yet it seems possible, for analytic purposes, to differentiate between the reception of stimulus information (as it is transmitted through the sense organs and encoded in the higher centers of the brain), and the decision processes by which, on the basis of a given stimulus input, the perceiver arrives at a psychophysical judgment, e.g., a comparison of the height of two stimuli. What is there in the available evidence to render such a distinction fruitful, and to support the above statement regarding the basis for the overconstancy phenomenon? It seems to be of two kinds: a negative and a positive one. On the negative side, there is one class of variables which appears to affect size and distance to only a very limited extent and to be relatively unimportant as a determiner of developmental change, viz., the class of variables relating to the structure of the stimulus field in which constancy judgments take place. The problem has, admittedly, received only scant attention in the past, but the results of our investigation, in which children were influenced even less than adults by the density on regularity of the texture of the field, as well as the similar findings for size judgments in Lambercier’s (194613) study of the articulation of the field, do point strongly towards such a conclusion. Although one might have expected these variables to play a particularly important role at the younger levels, the only effect attributable to them in either of these

302

rrOuerconstmcy”in Space Perception two studies was found rather in the adolescents and adults. In both cases,

furthermore, such effects as were in evidence involved conditions in which a set of elements of constant size was displayed at regular intervals over the field. Under these conditions older Ss are probably able to bring purely cognitive, inferential processes to bear on their judgments. The possibility remains, of course, that texture of the field and other similar variables might play a more important part over larger distances. As was noted in Part I, Whitehouse and Gruber (1957), studying distance judgments over stretches of up to 30 f t in adults, have found a significant reduction in overconstancy attributable to the presence of texture in the visual surface, but the only texture condition used appears to have involved a highly regular checkerboard pattern, which may again have allowed for the intervention of mechanisms of an inferential type. In addition it is conceivable that the role of texture might come out more clearly under conditions in which a thoroughgoing attempt is made to eliminate variables other than the structure of the field; this was not the case in our investigation, where cues of accommodation, as well as clues derived from the relative apparent sizes of the markers and the height of the pointer relative to the latter, may have played a role. Probably the clearest, most uncontaminated picture of the role of texture would be obtained via the use of two-dimensional, photographic stimulus fields; experimentation with such stimuli, at different age levels, is currently under way in our laboratories. In this connection we might also point to the considerable effects exerted by the structure of the stimulus field in a situation in which depth is merely suggested pictorially, by means of perspective drawings, and in which the task requires S to disregard this apparent depth (Wohlwill, 196213). Here we find, furthermore, a suggestion of greater effects attributable to the field for children, in comparison with adults. Turning to the positive side, the judgmental basis for the overconstancy encountered in adults and for the nature of the age changes to which this phenomenon is subject is brought out in the role played by a variety of variables relating to the subject and his orientation to the task. Thus overconstancy has been shown to be heightened by objective as compared to phenomenal instructions (Carlson, 1960; 1962); it is also affected by motivational variables (Singer, 1952; cf. also the performance of the volunteer Grade-XI Ss in our study). Furthermore, conditions which increase the difficulty of the judgment appear in general to enhance overconstancy, provided that there is no drastic loss of depth cues involved. The large amounts of overconstancy found at very large distances in Gilinsky’s (1955) study, as well as in the absence of any visible ground in Whitehouse and Gruber’s (1957) seem to be cases in point. All of these factors point to the operation of some compensatory process by which the adult S overadjusts for the phenomenal appearance of the stimulus relationships in the field. Given this

303

Joachim F. Wohlwill kind of judgmental basis, it is not surprising to find this phenomenon increasing with age, as cognitive mechanisms mature and come to intervene in such psychophysical judgments. This general picture is further strengthened by the role of practice effects in these situations. It was seen in both our study and in that of DenisPrinzhorn (1960) that during the course of unreinforced practice the judgments shifted increasingly in the overconstancy direction. Presumably frames of reference become estabIished in such laboratory situations as a function of practice, determining the extent of the overcompensatory adjustments effected by the subject; again, if we suppose that these adjustments reflect the intervention of cognitive mechanisms, such practice effects would be expected to be maximal at the older age levels, as they were in Denis-Prinzhorn’s adults and in our Grade XI group. But even accepting this general interpretation of overconstancy, several major questions remain to be answered. One of these was already touched on at the end of the review of the literature; it concerns the uncertain role of distance as a factor in the developmental course of this phenomenon. Since our own investigation dealt only with very short distances, corresponding to the extreme left portion of Fig. 6 (with which our results are in good accord), it still leaves unresolved the problem with respect to the possible deterioration of constancy, particularly in children, over longer distances. Secondly, there is the question of the course of the evolution of constancy from infancy through childhood. Apart from the experiment by BeyrI (1926), which indicated that at the ages of 2 and 3 years constancy is still far from perfect, and that it gradually increases without any marked breaks up to the age of 10, little information is available up to the age of 5 and 6. Some of the studies by Piaget and Lambercier on size perception in 5-year old children (cf. Table I), as well as our results for distance perception at the Kindergarten level suggest, however, that constancy is nearly fully established at that early age level, and that it may not be so much constancy that develops, but rather overconstancy-at least for fairly short distances. This possibility is enhanced by the very high values found at the young age levels with respect to the Interval of Uncertainty and the D-A factor; these indicate that in the early years the perception of spatial relationships is above all undifferentiated, so that the extent of approach to constancy may not be a very meaningful question at these age levels. More and better data from preschool children are clearly required to settle this issue, even though this represents undoubtedly a difficult methodological problem. It is possible, however, that extensive pretraining may permit the determination of more meaningful PSE values at this early age. Lastly, there remains perhaps the most important question of all, that of the specific processes and mechanisms underlying the observed shift towards

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“Ouerconstancy’i in Space Perception increasing overconstancy with age. To assert that this phenomenon has a judgmental basis clearly does not provide a complete answer to this question. The problem is compounded by the persistent failure of workers in this area to find perceptual judgments of size and distance related to even gross differences in tested intelligence, as in Jenkin and Feallock‘s (1760) and Leibowitz’s (1961) comparisons of size constancy in normal and mental defective groups; similarly, our study showed an absence of any consistent relationship between distance judgments and intelligence-test scores. Both Leibowitz and Jenkin and Feallock argue on the strength of their findings for a purely experiential rather than intellectual basis for observed changes in constancy. Yet this amounts to no more than a negative answer, since it is not readily apparent how experience as such could account for the development of overconstancy. A satisfactory resolution of this problem would seem to require more precise information regarding the correlates of overconstancy, in terms of certain other judgmental or cognitive tasks for which the underlying processes can be specified with some confidence. Such information is as yet largely lacking. With the foregoing conclusions and questions in mind, we may essay a brief reexamination of the theoretical views of space perception and perceptual learning considered in Part I of this paper. The theory of space perception for which these conclusions have the most direct bearing is probably that of Gibson. The findings indicating that, even under reasonably structured stimulus conditions judgments of size and distance evince progressively greater overconstancy with increases both in age and in practice raise serious questions as to the appropriateness of Gibson’s insistence on the veridicality-directed nature of perceptual learning. His views of perceptual learning as consisting exclusively of progressive differentiation likewise face difficulty in accounting for the shift in constant errors found as a function of practice, as well as age. Finally, it could be argued, as Gilinsky (1955) has in fact done, that Gibson’s basic concept of a “visual world” directly given to the observer through his senses requires revision, since even when he is explicitly directed to attend to this world (as is the case in all of the constancy studies calling for objective-size or -distance judgments), judgmental processes of compensation and inference, established through a prolonged developmental process, still intervene in his perception. Yet, if Gibson’s theory seems wanting as regards the formation of overconstancy, it is still of relevance to another aspect of judgments made in a constancy situation, and to the developmental changes which they undergo. Both the survey of the literature and our own study indicated that space perception at the younger age levels was in fact characterized by very considerable lack of specificity or differentiation, and that major developmental changes take place on this dimension, in accordance with Gibson’s hypothesis.

loachim F. Wohlwill Indeed, the evidence provoked the suggestion that in the early years this may be the main, if not the exclusive dimension of perceptual development in this domain. We are led, then, to a view of the developmental course of constancy as consisting in progressive differentiation, on which judgmental mechanisms effecting progressive shifts in the PSE in the direction of overconstancy are superimposed. A theoretical formulation which leaves more room for the action of such judgmental mechanisms in the perception of spatial relationships is that of Piaget (1961). The details of Piaget’s somewhat involved interpretation of the interrelationships between apparent (retinal) size, perceived size and perceived distance are too complex to warrant extensive discussion here, especially since many of the links in his argument are based on ad-hoc and in places unconvincing reasoning. Suffice it to note that Piaget espouses a modified version of the size-distance invariance hypothesis, in which perceived distance is regarded as primary and perceived size as a resultant of the former, in combination with apparent or projective size. According to Piaget, constancy for both size and distance develops in infancy to a high level for near space, by the intermediary of kinesthetic cues. These allow the infant to correct for the changing apparent sizes of objects as their distances are changed, first through his own manipulations of them and later through his movements away and towards them, For farther space, however, distances are themselves underestimated in infancy and childhood, due apparently to lack of support from kinesthetic cues, but during the course of development the intervention of compensatory “regulations” modifying the differential effects of centrations along the line of regard result (for reasons which are not made entirely clear) in over-estimation of distance, and consequently in overconstancy for size as well. It might be noted that such a differentiation between the development of space perception for near vs. further distances has been suggested by other workers (e.g., Leibowitz and Pishkin, 1961), though it is important to bear in mind that overconstancy is found at close distances (as in our study) as well as over longer ones. The aspect of Piaget’s theory which is of most interest for our purposes, however, is the conceptual framework which he has developed for the analysis of perceptual judgment generally. At the core of this framework is the concept of biasing centration effects arising in immediate perception, which are counteracted by compensatory forces developing during childhood and adolescence, attenuating and under particuIar conditions overcorrecting for these biases. Undeniably this formulation is in need of greater clarity and specificity, particularly as regards the conditions affecting the regulatory processes postulated by Piaget. The nature of their relationship to and interaction with the development of concepts of space, and of intelligence generally, is likewise in need of a more explicit statement,

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‘rOverconstancy” in Space Perception supported by empirical evidence.5 Yet the framework as such appears promising; at the very least it may be expected to provide us with a variety of hunches as regards the relevant dimensions of the problem. Moreover, it allows more readily than most of its competitors for an integration of the area of space perception within a more general, unified theory of perceptual development. If we have thus far omitted any reference to the third theoretical approach to the area of space perception cited in Part I, i.e., that of the transactionalists, this reflects the belief, already expressed earlier, that this theory is fundamentally silent with respect to the phenomenon with which we have dealt. For all their discussion of the role of learning in perception, and of idiosyncratic forces originating in the individual perceiver, the terms in which Ittleson and his associates treat the problems of space perception do not readily permit an analysis of the development from under- to overconstancy. Conceivably, the concept of “bets” or “assumptions” which these theorists have invoked might be extended to cover, if not actually to account for systematic biases such as shown in overconstancy, but the specifics of the formation of such a bias are not readily derivable from their treatment. Consideration of the transactionalist position may nevertheless be of value in alerting us to the potential role of meaning in space perception, which has been largely ignored in our discussion (cf. Ittelson, 1960, pp. 25 ff.). It appears plausible to suppose that the problems which we have dealt with here may reveal themselves in rather different form, once one leaves the world of rods, stakes and markers, observed in a state of essential immobility, and turns to a world of meaningful objects, entering into the actions of the perceiver. It is such a world, of course, to which the transactionalist’s conception is intended to apply.

V. A Note on Research Strategy in the Study of the Development of Perception At the end of Part I of this paper we pointed to a variety of ways in which a developmental approach might contribute to an understanding of the overconstancy problem. At the same time it was noted that many of the questions

’Conceivably Piaget’s views on this question have undergone some change in recent years; whereas earlier (e.g., Piaget and Lambercier, 1951) he has interpreted changes in size constancy during later childhood as directly related to the emergence of the child‘s ability to represent spatial relationships, at a conceptual level, in his recent book on perception (Piaget, 1961) he contents himself with a purely formal comparison between the nature of perceptual and conceptual development in this and other areas, without implying any necessary interaction between them. 307

Joachim F. Wohlwill potentially answerable through developmental research had not in fact been investigated as yet. Thus at the present juncture the potential contribution which such research can make in this field is still far from realized. It seems appropriate to focus briefly on this point, to examine the possible weaknesses of developmental research to date and to explore alternative ways of strengthening the approaches to research in this area. The major shortcoming of much, if not most of the research which we have considered appears to be the tendency of the research workers in this area to content themselves with a cross-sectional comparison of different age groups, with age as the chief, and frequently the only independent variable. The conclusions to be drawn from such comparisons are clearly quite limited in scope. Differences among age groups provide little conclusive evidence even with respect to such a general question as that of the innate vs. acquired character of constancy (or any other aspect of behavior), since these differences, if found, would be consistent with either an experiential or maturational interpretation. When it comes to drawing inferences to the processes underlying observed age changes, it is apparent that data of this kind are even less revealing. One way in which the meaningfulness of developmental data may be enhanced is by obtaining measures of processes which are presumed to underlie, or be closely related to the function being investigated. The correlation between them at different age levels can then be utilized, in order to determine the degree of covariation between the developmental changes taking place in the function which is at the center of interest and the related processes. Further, changes in the pattern of such correlations with age may provide information pointing to the emergence of new mechanisms mediating a given judgment or response, or to shifts in the nature of these mechanisms. Few investigations in the area of the development of perception have incorporated this kind of correlational approach, a notable exception being that by Witkin ef a/. (1954). In this study comparisons among age groups on a variety of measures of “field-dependence“ were supplemented by withingroup correlations among these measures, showing the increase in the consistency of this postulated characteristic of perception with age, as well as lending support to the authors’ differentiation between two types of tasks (“part-ofa-field” vs. “field-as-a-whole”) as regards the manifestation of this perceptual “trait.” In our own study on distance judgments a similar attempt met with rather less success; even though the developmental course of several of our supplementary spatial-perception variables closely paralleled that found for the bisection data, we noted that the correlation or association between them was consistently negligible. Yet, when one considers the marked extent of individual differences in the bisection judgments, even within a given age group, it is apparent that a large amount of variance in these responses remains

308

“Ovei*constancy”in Space Perception to be accounted for. This situation thus creates a clear challenge to uncover other variables which may bear a closer relationship to these judgments, and thereby help increase our understanding of the possible basis for the perceptual phenomenon investigated. The answer may lie in the choice of measures of a more strictly cognitive type ( e g , relating to the child’s concepts of space), or alternatively of variables relating more generally to aspects of the judgmental process itself, as they manifest themselves in a psychophysical task. Admittedly, correlational strategies as advocated here have often been regarded as suspect in experimentalist quarters, due to the lack of control over the variables being studied (cf. Cronbach, 1957). But the addition of a developmental dimension to the situation may alter the nature of such research in an important sense: It now becomes possible to determine the association, not merely between the variables which we wish to interrelate themselves, but between the changes in these variables as a function of age. Through the information thus obtained concerning the temporal patterning of the development of different classes of responses, we may hope to tap the underlying developmental processes in fairly direct fashion. In order to exploit the potential of this kind of correlational research to the fullest, however, and to bring the dimensions and determinants of age changes in this and other areas of behavior into the open, longitudinal data are sorely needed, even if only over limited time periods. Indeed, it does not seem too far-fetched to suggest that in areas of perception research such as the constancies or optical illusions in which consistent age changes are to be found, the future developmental investigator will turn to the analysis of longitudinal growth curves, much as students of physical development have been doing, for a fuller understanding of the nature of the developmental processes at work. At the same time much remains to be accomplished at a more strictly experimental level, to increase the significance of research in the field of perceptual development. Specifically, more intensive study of infevactionr of the age variable with variables under the control of the experimenter may be expected to provide a better understanding of the basis for observed age differences. Again, the attempt to apply such an approach in our own study, by exploring the differential role of the structure of the stimulus field at different age levels, yielded results that were rather less enlightening than had been hoped or expected. Yet the approach as such is nonetheless a promising one for developmental research, and has in fact already contributed much valuable information in the study of a variety of developmental problems. Perhaps the most fruitful line of attack will turn out to be a two-pronged one, combining the interactional one just considered with the correlational one discussed above, which may promise to lead to a true integration between experimental and differential research.

309

Joachina I;. Wohlwill In conclusion, and at the risk of belaboring the obvious, it is worth emphasizing that no research strategy can in and of itself be expected to lead to significant advances in science, in the absence of a viable theoretical formulation inspiring the research. For it is clearly the investigator’s theory, whether explicit or implicit, which will dictate the particular variables to be included in his research, and frequently the methodology adopted. Thus progress on the empirical, methodological and theoretical fronts must go hand in hand, if the researcher’s investment of time and effort is to yield a reasonable return. REFERENCES Akishige, Y.Experimentelle Untersuchungen iiber die Struktur des Wahrnehmungsraumes. Part 11. Mitt. jw.-liter. Fak. Kyusha-Univer., 1937,no. 4, 23-118. Beyrl, P. Ober die Grassenadassung bei Kindern. Z. Psychol., 1926, 100, 344-371. Brault, H.Etude ghktique de la constance des formes. Psyrhol. frunf., 1962, 7, 270-282. Brunswik, E. Die ZugHnglichkeit von Gengenstanden fiir die Wahrnehmung. Arch. ges. Psychol., 1933, 88, 377-418. Burzlaff, W. Methodologische Beitrage zum Problem der Farbenkonstanz. Z. Psychol., 1931, 119, 177-235. Carlson, V . R. Overestimation in size-constancy judgments. Amer. J. Psychol., 1960, 73, 199-213. Carlson, V. R. Size-constancy judgments and perceptual compromise. J. exp. Psychol., 1962, 63, 68-73. Chalmers, E. L. Monocular and binocular cues in the perception of size and distance. Amer. J . Psycho!., 1952,65, 415-423. Cohen, W., Hershkowitz, A., & Chodack, M. Size judgment at different distances a5 a function of age level. Child Develpm., 1958,29,473-479. Cronbach, L. J. The two disciplines of scientific psychology. Amer. Psychologist, 1957, 12, 671-684. Denis-Prinzhorn, M. Perception des distances et constance des grandeurs (Ctude gCn6tique). Arch. Psychol., GenPve, 1961,37, 181-309. Dukes, W. F. Ecological representativeness in studying perceptual size-constancy in childhood. Amer. J. Psychol., 1951,64,07-93. Edgren, R. D. A developmental study of motion perception, size constancy, recognition speed and judgment of verticality. Unpublished doctoral dissertation, Stanford Univer., 1953. Epstein, W., Park, J., PC Casey, A. The current status of the size-distance hypotheses. Psychol. Bull., 1961,58, 491-514. Gibson, E., & O h m , V. Experimental methods of studying perception in children. In P. H. Mussen (Ed.), Handbook of research methods i n chdd development. New York: John WiIey, 1960. Pp. 311-373. Gibson, J. J. (Ed.) Motion picture testing and research. AAP A v i d . Psychol. res. Rep., 1947, No. 7. Gibson,J. J. The perception of the Yisual world. Boston: Houghton MiWin, 1950. Gibson, J. J. Perception as a function of stimulation. In S. Koch (Ed.), Vol. 1. Psychology: T b e study of a science. New York: McGraw-Hill, 1959. Pp. 456-501.

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“Overconstancy” in Space Perception Gibson, J. J., & Gibson, E. J. Perceptual learning: Differentiation or enrichment? Psychol. Rev., 1955, 62, 32-41. Gilinsky, A. S. The effect of attitude upon the perception of size. Amer. J. Psychol., 1955, 68, 173-192. Gilinsky, A. S. The effect of growth on the perception of visual space. Paper read at Eastern Psychological Ass., New York City, April, 1960. Harway, N. I. The judgement of distance in children and adults. J . exp. Psychol., 1963, 65, 385-390. Hastorf, A. H., & Way, K. S. Apparent size with and without distance cues. J. gen. Psychol., 1952, 47, 181-188. Holway, A. H., & Boring, E. G. Determinants of apparent visual size with distance variant. Amer. J. Psychol., 1941, 54, 21-37. Ittelson, W. H. The constancies in perceptual theory. Psychol. Rev., 1951, 58, 285-294. Ittelson, W. H. Visual space perception. New York: Springer, 1960. Jenkin, N., & Feallock, S. M. Developmental and intellectual processes in size-distance judgment. Amer. J. Psyrhol., 1960, 73, 268-273. Klimpfinger, S. Die Entwicklung der Gestaltkonstanz vom Kind zum Erwachsenen. Arch. ges. PsychoZ., 1933, 88, 599-628. Lambercier, M. Recherches sur le dheloppement des perceptions: VI. La constance des grandeurs en comparaisons siriales. Arch. Psychol., Gendue., 1946a, 31, 1-204. Lambercier, M. Recherches sur le dheloppement des perceptions: VII. La configuration en profondeur dam la constance des grandeurs, Arch. Psychol., Gendue, 1946b, 31, 287-323. Leibowik, H. Apparent visual size as a function of distance for mentally deficient subjects. Amer. J. Psychol., 1961, 74, 98-100. Leibowitz, H., & Hartman, T. Reply to Howland. Science, 1959, 130, 1365-1366. Leibowitz, H., & Pishkin, V. Perceptual size constancy in chronic schizophrenia. J. consult. Psychol., 1961, 25, 196-199. Leibowitz, H., Bussey, T., & McGuire, P. Shape and size constancy in photographic reproductions. J. opt. SOC.Amer., 1956a, 47, 658-661. Leibowitz, H., Chinetti, P., & Sidowski, J. Exposure duration as a variable in perceptual constancy. Science, 1956b, 123, 668-669. Leibowitz, H., Waskow, I., Lode r, N., & Glaser, F. Intelligence level as a variable in the perception of shape. Quart. J. exp. Psychol., 1959, 11, 108-112. Locke, N. M. Perception and intelligence: Their phylogenetic relation. Psychol. Rev., 1938, 45, 335-345. Massucco Costa, A. Constanza percettiva di intervalli vuoti. Arch. Psicol. Neurol. Psichiat., 1949, 10, 377-388. Piaget, J. Ler mtcunismes perceptifs. Paris: Presses Univer., 1961. Piaget, J., & Inhelder, B. The child’s conception of space. London: Routledge & Paul, 1956. Piaget, J., & Lambercier, M. Recherches sur le dheloppement des perceptions: 11. La comparaison visuelle des hauteurs h distances variables dans le plan frontoparallele. Arch. Psyrhol., Gendue, 1943a, 29, 173-253. Piaget, J., & Lambercier, M. Recherches sur le developpement des perceptions: 111. Le probl he de la comparaison visuelle en profondeur (constance de la grandeur) et ‘I’erreursystkmatique de I’ktalon. Arch. Psycho!., GenBue, 1943b, 29, 253-308. Piaget, J., & Lambercier, M. Recherches sur le developpement des perceptions: VIII. Transpositions perceptives et transitivitk operatoire dans les comparaisons en profondeur. Arch. Psychol., GenPue, 1946, 31, 325-368.

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Joachim F. Wohlwill Piaget, J., & Lambercier, M. Recherches sur le diveloppement des perceptions: XII. La comparaison des grandeurs projectives chet I’enfant et chez I’adulte. Arch. Psychol., GenPve, 1951, 33, 81-130. Piaget, J., & Lambercier, M. Recherches sur le dkveloppement des perceptions: XXIX. Grandeurs projectives et grandeurs rCeIles avec italon kloigni. Arch. Psycbol., GenPve, 1956, 35, 257-280. Singer, J. L. Personal and environmental determinants of perception in a size constancy experiment. J . exp. Psychol., 1952, 43, 42C-427. Smith, W . M. A methodological study of size-distance perception. J . Psychol., 1953, 35, 143-1 5 3 . Sonoda, G. Perceptual constancies observed in plane pictures. In Y. Akishige (Ed.), Vol. 4. Experimental researches on the structure of the perceptual space. Fukuoka, Japan: Fac. Lit., Kyushu Univer., 1961. Pp. 199-228. Tada, H. Overestimation of farther distance in depth perception. Jdp. J. Psychol., L956,

27, 204-208. Thouless, R. H. Phenomenal regression to the real object. Brit. J . Psychol., 1931, 21, 3 39-3 59.

Thouless, R. H. Individual differences in phenomenal regression. Brit. J. Psychol., 1932,

22, 216-241. Vurpillot, E. Perception de la distance et de la grandeur des objets. Ann. Psychol., 1956,

56, 437-452. Wapner, S., & Werner, H. Perceptual development: An investigation within the framework of sensory-tonic field theory. Worcester, Mass.: Clark Univer. Press, 1957. Whitehouse, J. M., & Gruber, H. E. The effects of surface-texture and binocular disparity on distance-ratio perception. Paper read at Colorado Psychological Ass., Fort Collins, Colo., 1957. Witkin, H. A., Lewis, H. B., Hertzman, M., Machover, K., Meissner, P. B., and Wapner, S. Personality through perception: A n experimental and clinical study. New York: Harper, 1954. Wohlwill, J. F. Developmental studies of perception. Psychol. Bull., 1960, 57, 249288.

Wohlwill, J. F. From perception to inference: a dimension of cognitive development. Monogr. Sor. Res. Child Develpm., 1962a, 27, No. 2, 87-107. Wohlwill, J. F. The perspective illusion: perceived size and distance in fields varying in suggested depth, in children and adults. J . exp. Psychol., 1962b, 64, 300-310. Wohlwill, J. F. Overconstancy in distance perception as a function of the texture of the stimulus field and other variables. Percept. mot. Skills, 1963, 17, in press. Zeigler, H. P., & Leibowitz, H. Apparent visual size as a function of distance for children and adults. Amer. J . Psychol., 1957, 70, 106-109.

312

AINIATURE EXPERIMENTS IN THE D I S C R I M I N A T I O N L E A R N I N G OF RETARDATES'

Betty

1. House and Ddvid Zeaman UNIVERSITY OF CONNECTICUT

I. METHODOLOGY . . . . . . . . . . . . . . . . . 314 A. COMPLEXITY OF DISCRIMINATION LEARNING . . . . . 314 B. COMPLEXITY, A PARTIAL OUTGROWTH OF DESIGN . . . 315 C. ALTERNATIVE DESIGNS . . . . . . . . . . . . 317 11. DATAANDTHEORY . . . . . . . . . . . . . . . 321 A. EXPERIMENT ONE: COMPOUNDING . . . . . . . 321 B. EXPERIMENT TWO: 1-DIMENSIONAL COMPONENT LEARNI N G . . . . . . . . . . . . . . . . . . . 332 C. EXPERIMENT THREE: COMPONENTS-PLUS-1-COMPOUND-CUE 335 D. EXPERIMENT FOUR: I-DIMENSIONAL PROBLEMS WITH A VARIABLE IRRELEVANT DIMENSION . . . . . . . . 339 E. EXPERIMENT FIVE: CONFLICT AND COMBINATIONS OF CUES 344 111. MATHEMATICAL TREATMENTS . . . . . . . . . . . 355 A. OUTLINE OF ATTENTION THEORY . . . . . . . . . 355 B. GENERAL STRATEGY , . . . . . . . . . . . 356 C. EXPERIMENTS ONE AND TWO . . . . . . . . . . 358 D. FURTHER APPLICATIONS OF THE MODELS . . . . . 363 IV. GENERAL SUMMARY . . . . . . . . . . . . . . . 370 A. METHODOLOGY . . . . . . . . . . . . . . . 370 B. FINDINGS . . . . . . . . . . . . . . . . . 370 C. THEORETICAL IMPLICATIONS: QUALITATIVE . . . . . 371 D. THEORETICAL IMF'LICATIONS: QUANTITATIVE . . . . . 372 REFERENCES . . . . . . . . . . . . . . . . . . 373

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'Research reported here has been supported by Grant M-1099 of the National Institute of Mental Health of the US. Public Health Service. This report is an integration of five separate experiments by a team of investigators: Dr. Peter Eimas originated Experiment Three; Cynthia Klinman contributed Experiment Two; Karl Thaller collaborated in the conduct of Experiment Four; and the data of the normal children in Experiment Five form part of a doctoral dissertation by Dorothy Hoffman. We also wish to acknowledge the research collaboration of Dr. Bryan Shepp and Keith Scott. Without the cooperation of the administration of the Longley School of the Mansfield State Training School, Dr. John Cassell and Louis Boly, the research presented here would not have been possible.

313

I. Methodology A. COMPLEXITY OF DISCRIMINATION LEARNING The area of discrimination learning can be a surprisingly complex one, even with the simplest classes of discrimination problems solved by relatively unsophisticated subjects. Two-choice visual discriminations by children of low developmental level reveal complexities not suggested by traditional S-R theories (Spence, 1960, pp. 269-365). Such theories describe the solution of discrimination problems by the formation of single-link associations-the subject learns to approach the positive cue and avoid the negative. But our experimental and theoretical analyses of the discrimination learning of trainable retardates have led us to the conclusion that more than one associative link is formed. W e infer a chain of at least two responses, the first a response of attending to relevant stimulus dimensions, and the second an instrumental response of approach-avoidance to the cues of the relevant dimension (Zeaman & House, 1963). Some measure of the complexity of this idealized conception of the discriminative process can be had by counting the number of different, theoretically possible outcomes of a simple 2-choice experiment. A tree representing 6 possible sequences of responses and reward on one trial using an Attention Model of discrimination appears in Fig. 1. The stimulus dimensions within S* compete for attention. If attention is limited to a single look, at the moment of choice, then the subject will either look at the relevant dimension 0, or at one of the irrelevant dimensions (which may be many, 0,, 0,, . . . 0,). After focusing on one of the competing dimensions, the subject must approach one of the two values of cues of the dimension attended to. If he approaches the positive cue of the relevant dimension, reward (G) ensues. If the negative cue is approached, nonreward (G’) occurs. Approach to any of the cues of an irrelevant dimension (e.g., R,) leads to either G or G’ with a random probability set experimentally at +. With the minimum of 2 stimulus dimensions operating, the number of possible outcomes of a simple 2-choice discrimination trial for a single subject is theoretically 6. On Trial 2, there are 6 more possible sequences for each outcome of Trial 1, for a total of 36 different paths. By Trial 5, the tree in Fig. 1 would have 7776 branches! Add another irrelevant dimension (0,) and the number of branches jumps to 100,000 by Trial 5. In general, the number of branches by the end of Trial T is (4N-2)T, where N is the number of dimensions operating.

314

Discrimination Learning of Retardates

R

R Stimulus dimensions

Attending -responses

Instrumental responses

Reward conditions

Fig. 1 . A n Attention Model Trial. T h e trial begins with the presentation of S*, the set of all stimulus dimensions, both relevant and irrelevant. One or more observing or attending responses, 01, 02, . O,, are made to these dimensions, making effective the cues of the observed dimensions. A n instrumental approach response, R,, to the positive cue of a relevant dimension (after 01) bringr reinforcement, G. An approach response, R;, to the negative cue of the relevant dimension leads to nonreinforcement, G'. Approach responses, R?, R?', to cues of an irrelevant dimension lead randomly to G and G' with equal probabilities.

. .

B. COMPLEXITY, A PARTIAL OUTGROWTH OF DESIGN This explosive relationship between number of possible theoretical outcomes and number of trials can lead to astronomical figures given the fact that conventional discrimination learning methodology employs a large number of trials. The typical Trials-by-Subjects design is schematized in Table I. The values of the response measure R j j are usually 1 or 0 for a passfail score, or continuous measures if latencies are taken. The number of trials T often runs as high as 100. Deficiencies of this design are painfully apparent to researchers in discrimination learning. When T is large, heroic experimental effort is required. The instability of the individual measures Ri necessitates large numbers of subjects to be run to give stability to the group trial means R j . And if individual differences in learning are appreciable, an averaging error may bias the form of the trial-mean learning function (Estes, 1956). Finally, for the kind of model we think is needed, the large number of trials of this design leads to theoretical complexities of the kind outlined above. Some of these difficulties, it must be granted, can be countered to an extent by a willingness to spend time in the laboratory, by adopting special averaging techniques (e.g., grouping homogeneous subjects, use of backward learning curves), and by accepting semiquantitative theorizing. W e have,

Betty J. House and David Zeaman for example, used the Trials-by-Subjects Design to demonstrate experimentally a variety of discriminative effects with our imbecile subjects: the influences of stimulus factors, subject variables, reinforcement schedules, and transfer effects (Zeaman & House, 1963). Moreover, we have not found it impossible to bring gross aspects of these data within reach of a quantitative theory-a small collection of stochastic models organized by some postulates on the role of attention in discrimination (see Fig. 1) . Theoretical troubles emerged, however, when we sought more precise relationships of our probability models to data from the Trials-by-Subject TABLE I CONVENTIONAL EXPERIMENTAL DESIGNOF DISCRIMINATION LEARNINGEXPERIMENTS Trials

Subjects

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Rsr

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Ria

Group mean

Design. Explicit solutions of our theoretical equations were not mathematically available, so we had recourse to approximate solutions. Monte Carlo methods were used with digital computers to create statistical entities that behaved according to the rules of the model-Statchildren. The result is a computer simulation of the discriminative behavior of retardates. Matching the behavior of Statchildren with that of retardates provides an index of the predictive power of the theory and an approximate evaluation of the theoretical parameters used to bring about the match. Certain gross aspects of our retardate data are readily simulated by the Statchildren. To cite instances: (a) the forms of forward and backward learning curves can be matched; (b) the increase in number of relevant stimulus dimensions facilitates the discrimination learning of both retardates

316

Discpimination Learning of Retardates and Statchildren alike; (c) the theory predicts correctly that extradimensional shift is a negative transfer condition compared to intradimensional shift; (d) with some parameter-combinations discrimination reversal theoretically gives rise to functions of unusual shape-plateaus in the middle of the function-and these are observed in our reversal data. Despite these and other semiquantitative accomplishments, the stage of precise parameter estimation was not achieved, nor were the more stringent tests of quantitative theory, the “dragging” or transfer of fixed parameters from experiment to experiment. In principle and in time these may be achieved, but continued use of the standard Trials-by-Subjects Design is not likely to do the job with experimental efficiency or theoretical clarity.

C. ALTERNATIVE DESIGNS 1. The Miniature Experiment W e need to look at some alternative designs. For simplicity, the design of Estes’ Miniature Experiments (1960) cannot be improved upon. As Estes has pointed out, the minimum number of observations necessary for any learning experiment is two, a training trial followed by a test trial. The design is shown in Table 11. This is again a Trials-by-Subjects Design, but

DESIGN OF

A

TABLE I1 MINIATURE EXPERIMENT Trials

Subjects

1

2 Riz

1

Rii

2

Rzi

RZZ

3

Ral

R32

Rsi

Rsz

R,

R,

. S

G ~ O Umean ~

with the important difference that the number of trials is minimized at two. It could be used for discrimination learning experiments. It would have the advantage of reducing the number of theoretical possibilities (to 36, for instance, for the conditions of Fig. 1). It is relatively easy to write exact

317

Betty J. Home and David Zeaman expressions for just a few trials without recourse to the approximations necessary when many trials are given. Estes (1961) has demonstrated the power of this method for testing basic axioms of learning theory applied to paired-associate verbal learning. Only a short experimental time would be needed for each subject. And if linear functions were used to connect the two points of each function, there would be no averaging error. The big disadvantage (aside from the need for a large number of subjects) is the possibility that only a small amount of discrimination learning may occur on the first trial. 2. Learning Set Design

Another possible design comes from experiments on learning set (Harlow, 1959). A subject is tested for a small number of trials on each of a large number of problems selected randomly from a fairly homogeneous population of problems. The design is shown in Table 111.

TABLE 111 DESIGN OF LEARNINGSET EXPERIMENTS Trials 1

2

3

&I

RPZ

Rps

81

&

Rs

1

2

3

Problems

.

P Individual mean

This is clearly not a Trials-by-Subjects but rather a Trials-by-Problems Design with few trials (e.g., three). The principal advantages of this design &, &) can be obtained for each are: (a) stable learning functions (El, individual by increasing the number of problems, P; this may make a large subject population unnecessary; (b) averaging error can be minimized by finding more homogeneous problems; (c) theoretical complexities are manageable with only 3 trials. The disadvantages are the requirements of fast-learning subjects with stable learning rates and a sizable collection of homogeneous problems.

318

Discrimination Learning of Retardates If the disadvantages of this design can be overcome, it has much to recommend it. The requirement of fast-learning subjects does not preclude use of retardates. Our research has shown that if the attention of these subjects can be focused on relevant stimulus dimensions, learning is then only a matter of a few trials. And attention has been shown to be under the control of stimuli and transfer operations. Problems and pretraining may therefore be arranged to provide the requisite fast learning. The requirement of stable learning rates would not seem, at first, to be met using a technique specifically designed to study changes in learning rates, i.e., the formation of learning sets. But learning sets have not been found with trainable retardates (House & Zeaman, 1958) after they have been brought to criterion on a few pretraining problems. The important consequence of this fact for analysis of discrimination learning can be described in terms of Table 111: increasing degrees of stability of the individual trial means &, E2, R3 can be obtained by simply increasing P, since problems do not introduce a systematic source of variance. The third requirement of a sizable collection of homogeneous problems provides no obstacle. All that is needed is to try out a lot of problems on one group of retardates and pick out those of equal difficulty for use with the next subject sample. Our labor has been reduced by the finding that the same stimuli can be re-used with the same subject without transfer, providing that one or more different problems intervene (House 8: Zeaman, 1963). In principle, this implies that a series of problems of any length could be made with just four different stimuli. In practice, we have used many more than this. 3. Composite Design The best features of the Learning Set and Miniature Experiment Designs may be combined in the design shown in Table IV. The individual response measures, Ri,, Ria, Ri3, are the mean values from Table 111. Each subject is run on enough problems in the Learning Set Design to stabilize his mean trial function, then these individual means are entered into a Trials-bySubjects Design to yield group means Ma,, M,g,, M k a , The virtues of this composite design include the following: (a) neither very large numbers of subjects nor problems is required; a compromise between the two is effected; (b) having fairly stable individual functions permits the grouping of homogeneous subjects and minimizing of averaging error; (c) theoretical complexities can be handled with only 3 trials, and if appreciable amounts of learning appear on the second trial, analysis can be restricted to Trials 1 and 2. This achieves the maximal theoretical simplicity of the Miniature Experiment; (d) experimental efficiency is increased. Using each subject as

319

Betty J . House and David Zeaman his own control under a variety of conditions permits relatively fast exploration of the parameters of discrimination learning. This basic design (usually with more than 3 trials) is one that Harlow and his students (1959) have used for many years to study the discriminative processes of monkeys. Warren (1953) has used 6-trial problems to study cue combination in monkeys. Eimas & Shepp (1963) have used this methodology to partial out the separate roles of classical and instrumental conditioning in retardate discrimination learning. Especially pertinent is the work of Levine (1959) who has recently developed for the 3-trial case an ingenious TABLE IV A COMPOSITEDESIGN Trials 1

2

3

RSl

Rsz

Rss

MR,

M.q,

M2,

1 2

3

Subjects

S

Group mean

quantitative method for inferring relative strengths of various kinds of response sequences (“strategies” or “hypotheses”) . Despite these new developments and past usage, the primary emphasis in research employing the composite design has been largely on learning set phenomena. Many powerful features of this design for experimental and theoretical analyses of other aspects of discrimination learning have not been widely recognized or fully exploited. W e have begun a systematic series of experiments using the %trial method with our trainable retardates, the results of which follow immediately in sections dealing with empirical effects (data on stimulus and subject variables, as well as retention effects), theoretical analyses, and implications for further research with the 3-trial design. In each of the 5 experiments reported, the relevant dimensions are color, form, or both. We attempt to answer such questions as whether retardates

320

Discrimination Leurning of Retardates learn to approach the color and form cues as independent components or as compounds, whether two or three relevant dimensions produce faster learning than one, whether introducing variability into an irrelevant dimension retards learning, and other related questions. The nature of the children used in these 5 experiments is important. All are of low MA (ranging from 3 to 8 years), but all have been carefully pretrained so that they respond primarily to the color and form cues. Tendencies to respond to positional cues or other extraneous factors have been largely extinguished. With subjects pretrained in this way, there is a large performance increment following a single training trial. Percentage correct on Trial 2 is over 80% for some conditions. It is the possibility of obtaining big effects after single trials that makes the ?-trial method a feasible one.

11. Data and Theory A. EXPERIMENTONE: COMPOUNDING 1. Introduction

Definition Of Conipo~ndsAnd Components. Consider a simple discrimination problem in which the subject must choose between a black triangle and a black circle presented simultaneously, with a candy reward consistently hidden beneath the black triangle (the positive stimulus object). If the left-right position of the positive stimulus is randomized over trials, the problem requires for solution the discrimination of form or one of its correlates. A simple solution might be to approach the triangle. This has been called a componeizt solution, indicating that a single, differential aspect (or class of aspects) of the stimulus objects has been used as a basis for response. But other more complicated solutions exist and may actually be used. The subject may choose to approach not simply the triangle, but the black triangle-that is, the combination of two aspects as a unitary pattern, different from either of the constituent components. This may be called a compound solution. The fact that one part of the compound is a nondifferential or irrelevant aspect of the stimulus objects-the black color-does not mean that it cannot be a part of a relevant compound. Other, even more complicated compounds can be described. For example, “black triangle on the right or left” would be as position-color-form compound, and a correct one if approached in the problem above. Little reflection is needed to see that the number of possible compounds may be very large with problems having only a single relevant component. Furthermore, the number of possible solutions is doubled if the subject A.

321

Betty 1.House and David Zeaman chooses to solve the 2 choice problems by avoiding the negative component or compounds as an alternative to approach responses. B. Measurement And Significame Of Compounds. Whether compounds or components or both are used by subjects in a discrimination experiment can be determined by arranging appropriate transfer conditions which preserve or destroy particular compounds and test for loss of discriminative accuracy. Some clever designs have been used for this purpose (e.g., North & Jeeves, 1956; Wodinsky et al., 1954) but the results have not been clear enough to resolve several conflicting views on the relative strengths of components versus compounds in the discrimination learning of subjects of low developmental level. Werner (1948) regards responses to components as abstract, and characteristic of higher levels of development, responses to compounds as coircrete and hence more immature. The results of Kendler, et al. (1962), on the other hand, suggest that compounding increases with mental age, as inferred from children’s verbalized solutions of discrimination problems. The opposite view is held by Teas and Bitterman (1952), who regard compound solutions as more primitive than component, and present some evidence in support of this position. A closer look at this controversy can be postponed for later discussion. An additional source of interest in compounds stems from problems of selection of appropriate quantitative theories. Restle (1959), for instance, has an attractive theory of discrimination assuming independent stimulus components which when combined do not form compounds. The applicability of Restle’s theory to the discrimination learning of color and form in retardates is therefore dependent upon the outcome of experiments testing for the presence or absence of compounds. 2. General Strategy W e have adapted the 3-trial methodology to arrange some novel tests for compounds and components. Each subject is given several hundred problems, each of 3 trials only. Attention will be focussed largely on the results of the first 2 trials, since these bear most heavily on the issue of compounding. The basic design of the first two trials is illustrated in Fig. 2 and represents, to the best of our knowledge, a new way of testing for compounds. On Trial 1, a single component is made relevant-form, in the e x a m p k with color made constant. The compounds of form, such as the color-form compound C,F,, are also relevant. On Trial 2 of the Positive Compound Condition, the original form dimension is collapsed (i.e., made constant) at the value of the previously positive stimulus. In the Negative Compound Condition, the form dimension is also collapsed, but at the value of the previous negative stimulus. Note that for either problem, the subject responding solely

322

Discrimination Learning of Retardates to components must be at chance on Trial 2, since form is relevant on Trial 1, while color is relevant on Trial 2. The subject using compounds, however, bas a basis for response on Trial 2 . He may continue to approach the positive compound C,F, under the one condition, or avoid the negative compound C,F2, under the other. Although the subject may use compounds to form his response on Trial 2 , he receives no differential reinforcement for doing so. Reward is half the time placed under one of the stimuli, and half the time under the other. If in Fig. 2 we arbitrarily designate the stimulus on the left as “correct,” then percentages of correct choices significantly greater than 50 on Trial Negative compound conditions

Positive compound conditions Trial 1 (Form variable, color constant)

(Color variable,

A

o h

A

A I

ClFl

C,F,

ClF,

0 0 CIF,

Pig. 2. Sample stimulus arrangements on Trials 1 and 2 for two experimental conditions. A descriptive notation is introduced beneath each stimulus: C and F represent color and form; the numerical Jubsrripts 1 and 2 denote different component values of color and form. Subjects responding on131 i o components on Trial 1 have no basis for responses on Trial 2.

2 provide an estimate of the use of positive and negative compounds in the two conditions, respectively. Before presenting the results of Trial 2 choices,

which will show that both positive and negative compounds are indeed used by retardates, it is necessary to describe more completely the experimental design, including Trial 3 and control conditions. 3. Experimental Design The two conditions pictured in Fig. 2 become four when the reward values of the two stimuli are reversed on Trial 2. A parallel set of four conditions is obtained if form is made constant on the first trial, with color variable, and if form is variable, color constant, on the second trial. These 4 conditions can be represented in the symbolic notation of Fig, 2 by

323

Betty I. House and Dnuid Zeaman transposing the subscripts. For example, on the first trial subjects are presented with CIFl vs. C,F,. If the Trial 2 subscripts are transposed in a similar manner, a total of 8 different types of problems are generated. On Trial 3, two more treatment conditions are added. The relevant cornponent cues from Trials 1 and 2 are combined so as to summate or conflict. Table V describes the stimulus arrangements for eight of the conditions. The Table is to be read from left to right as a tree with eight branches. Conditions C-111, for instance, has CIFl vs. C2Fl on Trial 1, C,F, vs. C,Fl

STIMULUS

Trial 1

TABLE V ARRANGEMENTS AND REWARDVALUES TRIALS AND EIGHT CONDITIONS" Trial 2

Trial 3

ON

THREE Condition: C

Stimuli without the positive (reward) and negative (nonreward) signs are rewarded on half their presentations. Different colors and forms ace used for the different conditions.

a

on Trial 2, and CIF, vs. C,F, on Trial 3. Eight more conditions, F-I-F-VIII, are generated by interchanging the subscripts in Table V. This completes the description of 16 experimental problems. Two control conditions were also included, a Standard Color Problem with a constant irrelevant form dimension in which all three trials were C,F,(+) vs. C2Fl(-), and a Standard Form Problem in which all 3 trials were C,F,(+)vs. C,F, (-)

.

4. Method A. Subjects. The 16 subjects were selected randomly from boys and girls attending classes at the Longley School of the Mansfield State Training School within the MA range of 4-8 years. Mean MA was 74 months (range: 51-90), mean IQ was 46 (range: 30-68), and mean CA was 169 months (range: 105-218). Four subjects met failure criterion during the experiment. B. Procedure. Two stages of procedure can be identified: (a) pretraining, and (b) experiment proper. (a) Before beginning the experiment, each subject was required to pass a series of pretraining stages. During the

324

Discrimination Learning of Retardates first stage, 25 trials per day were given on a pair of stimulus objects differing multidimensionally, until the criterion of 20/2 5 correct during a daily session was met. During the second stage the children were given a problem with two 3-dimensional objects differing in color and form, again for 25 trials a day to a 20/25 criterion. Subjects then learned a pattern problem (with stimuli of the type to be used in the experiment) with both color and form relevant. These pattern problems were presented 25 trials per day to the 20/25 criterion with new problems being presented until the subjects learned a new problem in one day, and then two additional problems. Subjects were dropped from the experiment if more than 5 days were required to learn a single problem during any stage of pretraining. Before each daily experimental session the child was given a warmup problem with both color and form relevant. Trials were continued until 7 successive correct responses or for a maximum of 25 trials. Those failing to reach the 7-in-a-row criterion were not run on the daily experimental session but continued on the same warmup problem before the next session. If the subject failed to reach criterion within 3 days he was dropped from the experiment. (b) During each block of 24 problems (12 per day) of the experiment proper, every subject had 4 Standard Color Problems, 4 Standard Form Problems, and 1 each of the 16 experimental problems described above. The left-right position sequences were balanced over problems, with 8 different position sequences occurring 3 times each over 2 successive daily sessions. There were 49 different color-form stimuli made from seven geometric forms (circle, square, diamond, triangle, T, cross, and star) and seven colors (red, yellow, green, orange, black, brown, and blue). For any given problem, the 2 forms (or colors) to be designated I;, and F, (or C, and C , ) were selected randomly with the restriction that these did not appear on the previous problem. It is important to observe that colors and forms are changed from problem to problem. If the stimulus C,F,, for example, appears in 2 different problems, using the notation of Table V, this does not mean that the same colors and forms appear in both problems. A noncorrection procedure was used, with candy reward for correct responses. Intertrial intervals averaged 10 sec, and interproblem intervals averaged approximately 30 sec within a daily session. The experiment lasted for 32 days, with a total of 384 problems per subject. c. Appuratus. A modified version of the Wisconsin General Test Apparatus, described elsewhere (Bijou & Baer, 1960), was employed. The discriminanda were 2-in. forms cut from colored construction paper and pasted on 3-in., white cardboard backgrounds. These were used to cover the baited and unbaited food-wells of the WGTA and were moved aside by the subject in making his choice.

325

Betty J. Hozlse und Duvid Zeulnan 5 . Trid 2: Results and Discussion A. Compounds VS. Components. It will be recalled that on Trial 2 a subject responding solely to components must perform at chance. Reinspection of the left column of Fig. 2 shows the conditions under which an approach to the previously correct positive compound will cause a deviation from 50% on Trial 2. In the notation of Table V, there are eight estimates of the probability of approaching the positive compound: the percentages of correct response on Trial 2 for conditions C-I, C-11, F-I, and F-11, and the percentages of incorrect responses for C-111, C-IV, F-111, and F-IV. A mean of these eight measures for each subject defines a Positive Compounding Index. A corresponding estimate of the probability of avoiding the negative compound (see the right column of Fig. 2 ) can be derived from mean percentages incorrect on Trial 2 of conditions C-V, C-VI, F-V, and F-VI, and percentages correct on C-VII, C-VIII, F-VII, and F-VIII. The mean of these eight measures defines the Negative Compounding Index. Individual values of these indices for each of the 12 subjects are given in Table VI, together with the mean percentages of correct responses on Trial 2 for the Standard Color and Standard Form Problems.

TABLE VI VALUESOF

THE COMPOUNDING INDICESAND PERCENTAGES CORRECT ON TRIAL2 OF THE STANDARDPROBLEMS

Su bjecc A B C

D E F

G H I

J

K L

Positive compound index

Negative compound index

Trial 2 standard problem

____ 62.2 73.8 55.5 70.5 68.8 64.2 60.5 50.8 61 .O 55.5 72.5 70.2

56.3 52.3 60.0 59.5 45.5 56.3 50.8 56.0 45.9 65.5 38.7 25.2

69.5 87.5 75 .a 87.5 81.2 82.0 79.7 65.6 68.0 86.0 90.6 71.9

The data of Table VI are presented in the form of gradients in Fig. 3 along with some profiles that would be expected if subjects adopted pure strategies. These are quite simply derived. Consider first the strategy: Approach Positive Compound. If on the Standard ProbIems the subject is responding solely to the positive compound (and not at all to components or negative

Discrimination Learning of Retardates compounds), then on Trial 2 of the transfer conditions classified as Positive Compound Conditions (see Fig. 2 ) such a subject would suffer no decrement since the positive compound is preserved. The expected value of his Positive Compound Index would be the percentage correct observed on Trial 2 of the Standard Problems. The value assigned in the left side of Fig. 3 for

’

PURE STRATEGIES APPROACH Po:

AVOID

DATA

PO

GQM

COk 11

.1a

8C

.70

g 7c

-

’IVE )UND

NEGATIVE COMPOUND

a

I-

z

-m

I.A

: a

a w a

a .5a m 0

a a

a‘.

M w (3

40 W

> a 30

20

Pig. 3. Gradients of approach and avoidance with respect to compounds. The left frame shows the profiles corresponding t o pure strategies; the right frame carries the profiles for 12 subjects. Each point is bared on 128 observationr.

this pure strategy is the group mean percentage correct on Trial 2 of the Standard Problems. During the Negative Compound Transfer Conditions, the subject with the pure strategy of approaching the positive compound must be at chance (50%) on Trial 2 since the positive compound does not appear. This yields the negatively sloped profile labelled “Approach Positive” in Fig. 3. The other pure strategy gradients are derived following the same line of reasoning. The “Avoid Negative” pure strategy has a slope complementary

327

Betty J. H o m e and David Zeaman to that of Approach Positive. The subject who uses both positive and negative compounds equally in solving the Standard Problems will do as well on all Trial 2 transfer tests as on the Standard Problems-thus the flat gradient labeled "Both Positive and Negative." As has been pointed out, the Component Strategy gives chance on all transfer tests. Many other strategies are possible, but only one other seems plausible given our data. Some of our previous research (Zeaman et al., 1958; House & Zeaman, 1958) has shown these subjects to be responsive to novelty and familiarity as independent dimensions of stimuli. All the Trial 2 transfer operations performed in this study introduce a choice between cues that are novel or familiar with respect to appearance on Trial 1. The gradients expected for the pure strategies of approaching familiar and novel cues are complementary and unique. B. Individual Differences. We can attempt to classify our subjects by comparing their obtained gradients with those corresponding to pure strategies. Inspection of Fig. 3 and Table VI shows that although none of the retardates had a pure strategy (a few achieved approximations), all subjects showed some evidence of using compounds. If we define as the Component Region in Fig. 3 the area between plus and minus one standard error of a percentage (S.E., = 4.4), the subjects can be classified as follows: Approach Positive Compound: Subjects B, E, G, I Avoid Negative Compound: Subject H Both Approach and Avoid: Subjects A, C, D, F, J Approach Familiar Compound or Components: Subjects K , L The downward slopes of most gradients lead us to the inference that positive compound cues are used appreciably more than negative compound cues, an interpretation consistent with earlier findings (Zeaman & House, 1962) that approach tendencies exceed avoidance in these subjects. W e can not rule out the possibility, however, that approach and avoidance tendencies are equal here, and that the Negative Compound Indices are being pulled downward toward the 50% level by partial tendencies to approach familiar stimuli. But since only two subjects (K and L) showed reliable evidence of approaching familiar stimuli, we are inclined away from this alternative explanation. There is no strong evidence of the use of components in the Trial 2 data. The fact that no subject did as well in the Positive Compound Conditions as on Trial 2 of the Standard Condition cannot be attributed to the loss of components alone, because the negative compounds are also missing under these conditions. The best evidence for the use of components comes from B, E, G, and I , who show no reliable sign of using the negative compound, and yet insufficient strength of positive compounding to account for their Trial

328

Discrimination Learning of Retardates 2 levels on the Standard Problems. The only remaining sources of cues that could help in the Standard Problems are the color and form components.

6. Trial 3: Results and Discussion A. Compounding. O n Trial 3 the relevant component cues from the two earlier trials are combined either to summate or conflict. The 16 conditions of Trial 3 are shown in Table VII. Because the table is elaborate, the meaning of the left half of the top row is redescribed verbally as follows: Condition C-I displays Stimulus C,F, (designated as positive) and Stimulus C,F, (negative) on Trial 3; the components C, and F , were both positive on previous trials, hence their effects should summate; the compound C,F, was positive on both Trial 1 and Trial 2, while the compound C,F, did not appear previously in this condition; the percentage correct responses was 79. The top half of the table represents all those conditions in which the components summate. It may be observed that for all 4 conditions, each component is diff ereiztiully reinforced just once before the third trial. If compounds played no role, the 4 conditions, C-I, C-111, C-V, and C-VII, should yield the same percentage correct, as should those of F-I, F-111, F-V, and F-VII. A Conditions-by-Subjects-by-Dimension analysis of variance of the data of these 8 cells revealed one significant effect-for Conditions, indicating that the previous reinforcement history of compounds affected performance. Reward of a positive compound appeared to have more effect than nonreward of the negative compound, and the sequence of rewardnonreward makes a difference which will be discussed in the next section. The bottom half of the table represents all those conditions in which the components conflict. Choice here depends upon the subject’s preference for color or form, for particular compounds, or, perhaps, for the most recently rewarded component. An analysis of variance of the data of these 8 cells revealed no reliable main effects, but one significant interactionConditions-by-Dimensioh. W e have as yet no reasonable interpretation of this result. B. Retention Effects. Some indication of a recency phenomenon is shown in the comparisons of performance on C-I11 (and F-111) with those of C-V (and F-V). A compound reinforced on Trial 2 is more attractive, other factors constant, than one reinforced on Trial 1. The effect is not large, averaging about 5.50/0, but it is the first indication we have had of short term retention effects in the discrimination learning of these subjects. It is not the last. c. Color-Form Differences. That color is a more difficult dimension than form in the discrimination learning of retardates has been found using Trials-by-Subjects designs (House & Zeaman, 1962). The present methodology

329

b

TABLE VII PERCENTAGE OF “CORRECT” R E ~ N SON E TRIAL. 3 FOR 16 EXPERIMENTAL CONDITIONS DIFFERING IN STIMULUS AND PREVIOUS REINFORCEMENT HlSTORY OF THE COMPOUNDS” ARRANGEMENT

bJ

0

Condition

C-I

GI11 Summation

c-VII GV

C-IV GI1 Conflictb

c-VI GVIII

Trial 3 stimulus arrangement

CiFi CzFz CiFz CZFl

Previous history of Trial 3 compounds

Trial 1

Trial2

+

+ +

X X

-

CiFt

X

C81

-

CiFi CVFZ

CiFi Cn F2

+

%

“Correct” on Trial 3 79 69

X

X

-

+

-

X

X

75 62

36

X

-

-

X

CiFz CzFi

X

+

31

-

X

32

X

F-I11

X

X

+

F-I

X

ClF2 CaFi

CiFi Cz Fz‘

Condition

X

34

F-VII F-V F- N

F-I1

F-VI

Trial 3 stimulus arrangement

FiCi FOCZ

F-VIII

TriaI 1

TriaI2

+

+ +

X

FiCz F2C1

-

FiCz FzCi

-

FI Cl FzCz FiCi FsCz Fi6 FzCi

FiG FsCi

-t

Previous history of Trial 3 compounds

FIG FzCa

X

X

+

The previously rewarded component of each compound is in boldface type.

Average (%)

77

78

68

68.5

X

64

69.5

X

X

X

-

64

63

X

+

-

24

30

X

X

X

-

47

40.5

-

X X

44

37.5

X

35

33.5

X

-

+ X

The stimulus designated “correct” is placed on top in each condition. The notation x means that the compound did not appear;

Each percentage is based on 160 obsmtionr, 16 per subject. Subjects K and L wert omitted

%

“Correct” on Trial 3

+

+

+ refers to reward; - refers to n o n r m d .

Discrimination Learning

of

Retardates

recovers this fact, as shown in Fig. 4, although a reliable difference does not appear until Trial 3 of the Standard Color and Standard Form Problems. All but one of the 12 subjects were better on Form than Color on Trial 3. The persistence of the color-form difference in spite of extensive experience is somewhat surprising. 7. E f ects of Intelligence The range of MAS (51-90 months) was great enough to warrant a look at the relation of this variable to amount of compounding. The rank-order correlation of MA with the Positive Compounding Index was +.50 ( p < .lo)

°

I0

I0O L

0 K 90 W

a

0 0

80

I

I

I-

z w

0

K

W

n

z

60

U

W I 5 0 I......

I

2

3

TRIALS

Fig. 4. Performance on the Standard Color and Standard Form Problems.

with the higher MAS having higher indices. The difference in compounding for the two MA levels was significant by a t-test comparing 5 subjects in the MA range 4-6 years with 5 in the M A range 6-8 years, excluding the 2 subjects, L and K , because their use of compounds was not conclusive. Average Positive Compound Index was 58% for the lower and 66% for the higher ( t = 2.16, p < .05). A Mann-Whitney U Test was also significant at the .05 level.

a. Brief Szmrnary The major points to be made are: (a) Compounds, even though not differentially reinforced, are used by retarded children. (b) Evidence of use of both the positive and negative compound cue was clear, with positive

33 I

Betty J . Home and David Zearnan greater than negative. (c) Brighter subjects tend to compound more than those of lower MA. (d) Some indications of short-term retention loss of compound associations were observed.

B. EXPERIMENTTwo : 1-DIMENSIONAL COMPONENT LEARNING 1. Purpose Having discovered in Exepriment One that compounds are used by retardates, we turn now to a study by Cynthia Klinman (1963) demonstrating that components alone-without compounds-can also form the basis of discriminative learning in these subjects. To show this, the color-form compounds are eliminated on Trials 2 and 3, after a standard first trial with both color and form (and their compounds) relevant. This leaves only components as a possible basis for problem solution.

2 . Experimental Design

The stimulus arrangements are simple enough. O n Trial 1 both color and form are varied; thus the child may learn which color, which form, and/or which color-form compound are correct. To determine whether the color components alone have acquired approach-avoidance tendencies independently of form, the positive and negative color cues are presented on Trial 2 in combination with a new form. For example, if red circle and blue triangle are the correct and incorrect stimulus patterns on Trial 1, then on Trial 2 a red square and a blue square might be presented. Since the form cues and compound cues of Trial 1 are absent on Trial 2, the subject can perform above chance only by approaching the previously correct color-a component solution. In a similar way, to test for habit strength to the form cues alone, Trial 2 might instead present a green circle versus a green triangle. Again, only component information is of use here. To complete the design, Trial 3 consists of a test of the component dimension not tested on Trial 2. For purposes of comparison, other problems, Standard Color, and Form, were also run. An outline of the experimental conditions may be seen in Table VIII.

3. Method A. Procedure. Problems were presented in daily sessions of 1 2 each, 2 Standard Color, 2 Standard Form, and 4 each of Experimental Problems I and I1 as shown in Table VIII. Position sequences were balanced over days and Conditions. The pretraining, warmup, random assignment of colors and forms to

332

Discrimination Learning

of

Retardates

the problems, and other procedural aspects were the same as in Experiment One. The experiment ran for 8 days, providing a total of 96 problems for each of 8 children. B. Subjects. Retardates were selected from within the M A range 6-8 years. The 8 subjects had mean M A of 87 months (range: 77-96), mean IQ o f 5 5 (range: 48-69), and mean C A of 1 6 1 months (range: 1 3 3 - 2 0 3 ) .

Problem

Component-only problems

+ -

ClPl C*& Color, form Both 48

+ -

C3R CaFz O D Form None 65

+ clF3 c2F3

A

A

+ -

ClPl C2P2 0 . Color, form Both 55

+ -

~ I P SCZFS

A

A

Color None 63

+ -

CSK CJFZ

Q

D

Color None

Form None

52

56

Standard form

+ -

ClPl ClR 0 0 Form Both 53

+ -

CIK CiFz O R Form Both 79

+ -

CIFI ClF2 0 0 Form Both 87

Standard color

+ -

ClPl ClFl 0 . Color Both 55

+ -

CiFi CzR 0 . Color Both 77

+ -

CIS CIS

0 . Color Both 85

A. Components And Compounds. Performance levels on Trial 2 of the Experimental Problems are significantly higher than chance, proving that some component learning has gone on in Trial 1. The much higher performance on Trial 2 of the Standard Problems might be taken as evidence that compounds are also contributing to performance, since compounds as well as com-

333

Betty 1.House and David Zeaman ponents are available in Standard Problems. An alternative view is that retardates are more likely, in the Standard Problem, to learn the correct color when form cues are the same for both stimuli, and more likely to learn form when color is constant. Consequently, the comparison of Standard and Experimental Problem performances does not provide conclusive evidence of compounding in this experiment. W e rely instead on the evidence from Experiment One that compounds are indeed used. A comparison can then be made of the extent to which compounds and components contribute to performance. Considering only subjects of the MA 6-8 in Experiment One, the mean percentage of preference for the positive compound was 68%. This figure may be compared with the 63% and 65% preference for the positive color and form components, respectively, in the present experiment, to arrive at the conclusion that compounds contribute at least as much as components. B. Color And Form. When either the correct coIor or correct form reappears on Trial 2 in a novel compound, these children show about the same suprachance tendency to approach the color and form components. Nor is there much difference between their performances on the Standard Color and Form Problems. What differences there are agree in direction-form over colorwith those observed in Experiment One, but they are no longer of reliable magnitude. This change we cannot attribute to the higher MA range of the subjects in Experiment 2, because color-form differences reappear in later studies at MAS up to 8. We will avoid Type I1 Error by not denying colorform differences in these data. C. Retention Efectr. Although these subjects can use either color or form information on Trial 2, the information is gone by Trial 3. Performance is at chance. This striking loss must be classified as a retention loss, rather than a learning or attention deficit, for the simple reason that the behavior is present and reinforced on Trial 2, but not observed on Trial 3 . The effect bears some resemblance to the recency effect demonstrated for Trial 3 of Experiment One, in the sense that a response tendency developed on one trial is weakened by events on the next for no clearly associative reason. The retention effect is analogous to results from some short-term memory experiments. Lawrence and LaBerge (1956), for example, asked college students to report the form, color, and number of figures after tachistoscopic presentation. The order of reporting the three dimensions of the stimuli was specified after stimulus presentation and was varied randomly from trial to trial so that the subjects could not anticipate. Under these circumstances, accuracy of recall decreased from the first to the third dimension reported. A similar study by Herman & House (1960) reproduced the effect with retarded subjects. After tachistoscopic presentation of figures differing in color and form, subjects were asked to report the color and form. Again, the dimension reported first was more accurately recalled than the dimension reported

334

Discrimination Learning of Retardates second. Broadbent’s theory of immediate memory (1958) purports to account for phenomena of this kind. 5. Brief Summary In solving 2-choice visual discriminations, retardates use components as well as compounds, and both in about equal degree. The retention of component learning on Trial 1 is lost to some extent during Trial 2, an effect observed also with compounds.

C. EXPERIMENTTHREE: COMPONENTS-PLUS-~-COMPOUND-CUE 1. Purpose The main features of Experiments One and Two are combined in Experiment Three, by P. Eimas (1963), and the main effects of both are recovered. Discriminative performance is measured under the joint influence of a component and one compound cue (i.e., either the positive or negative cue of the compound). The results may then be compared with performance supported by compounds alone (Experiment One), by components alone (Experiment Two), and by compounds-plus-components (Standard Problems). Differences yield further estimates of strengths of components and positive and negative compounds. 2. Experimental Design

The stimulus arrangements are the same as those of Experiment Two in that two variable component dimensions (color and form) are present on Trial 1; one of these component dimensions is collapsed (made constant) on Trial 2, then restored on Trial 3 when the other dimension is collapsed. The arrangements are different from those of Experiment Two in that new cues are not used for the collapsed dimensions. Instead, the constant dimension has the value of either the positive or negative stimulus on Trial I . This makes one compound cue-either positive or negative-available for problem solution along with the components. Standard problems accompany four experimental problems for purposes of comparison. Table IX outlines the conditions of the experiment with specific examples. 3. Method A. Subjects. The subjects were eight boys and girls selected from the MA range 6-8 years to match those of Experiment Two, Their mean MA was 87 months (range: 72-95), mean IQ 49 (range: 38-67) and mean CA 191 months (range: 140-235).

335

Betty 1.House and David Zeaman B. Procedure. During each daily session, 12 problems were presented, 2 each of the 6 shown in Table IX. Subjects ran for 16 days providing 32 measures for each problem type. Other procedural details were the same as for Experiment Two.

4. Results and Discussion A. Compounds And Comporzents. Performance levels on the various stimulus combinations are shown in Table IX. Comparisons of the Standard Problem

TABLE IX DESCRIPTIONS OF STIMULUS-REWARD CONDITIONS,CUESAVAILABLE FOR SOLUTION, AND PERCENTAGES OF CORRECT CHOICES FOR SIX PROBLEMS One-component-plus-one-compound-cue problems

Problem

Standard color

+ -

f -

+ - + - + - + -

A

A

A

CiPi GK C14 C Z ~ Z CIS Cz&

-

Standard form

0

0

0

CIS CzFz CiS CiFz CiFi CzK A 0 A 0 A A

Color, form Both

Color, form Both

Color, form Both

Color, form Both

Form

Color

Both

Both

45

48

48

46

52

45

IA

A

Trial)Example Available components Form Compounds Negative (96 Correct 70

I+ -

0

Form Positive 73

0

0

Color Negative 66

A

A

Color Positive 73

A

0

Form Both 79

A

A

Color Both 80

+ - + - + - + - + -

ClFl CZFL ClFl CZR CiK CiR CiPi CiFz CIS CiFz C i 4 CzK

A

A

Color Trial 1 positive

A

A

Color Positive

YS.

Trial 2 positive 31

77

A

0

Form Trial 1 positive vs. Trial 2 positive 44

A

0

A

0

A

A

Form Positive

Form Both

Color Both

77

92

83

Trial 2 percentages with those of the four Component-Plus-One-CompoundCue Problems yield estimates (possibly biased) of the use of compounds. Com-

336

Discrimination Learning of Retardates pare, for example, the 70% on Problem I (form components plus negative compound) with 79% on Problem V (form components and both positive and negative compounds) ; the difference, 9%, would be weighted by the influence of the positive compound. Following logic of this kind, we can use Table IX to construct Table X. Appropriate statistical analyses show that the average percentage differences in Table X are reliably greater than zero for the Positive Compound Conditions and for the Negative Compound Conditions, and that the differences reflecting the positive compound are significantly stronger than those of the negative. These results are in agreement with the findings of Experiments One and Two. Some caution should be observed in interpreting Table X. Such comparisons ESTIMATES OF

Compound

Positive

TABLE X USE OF COMPOUNDS FROM PERCENTAGE DIFFERENCES ON TRIAL 2

THE

Problems compared Problem V minus Problem I 79-7096 Problem VI minus Problem 111

Percentage differences 9 14

80-6696

Negative

Problem V minus Problem I1 79-7396 Problem VI minus Problem IV 80-73%

6

7

may give inflated estimates of the influence of compounds for reasons explained in Experiment Two: the presence of only one variable component on Trial 1 of the Standard Problems may make the components stronger in the Standard Problem. Conveniently, this possible source of bias is eliminated by other comparisons with the data of Experiment Two. Performance on Trial 2 of Problem I1 of the previous experiment (65%) is supported by form components alone. Performance on Trial 2 of Problem I1 of the present experiment (73%) reflects form components and the positive compound. The difference ( 8 % ) is a measure of the influence of the positive compound. Three other comparisons can be made, the results of which appear in Table XI. The combined difference in percentage correct attributable to positive compounds in Experiment Three is significant (t = 1.96, p < . 0 5 ) , but the effect of negative compound is not (t < 1 ) . The effects shown in Table XI, although not as large as those of Table X, are in the same direction and support the same conclusions that compounds are used, with positive greater than negative.

337

Betty J . House and David Zeamm The Trial 3 results yield unmistakable evidence of the action of compounds. Consider the 31% correct choice on Trial 3 of Problem I. What is pushing performance so far below chance level? Subjects must choose between a positive stimulus containing a component plus a positive compound, both rewarded on Trial 1, and a negative stimulus containing a positive compound reinforced on Trial 2. They strongly prefer the latter-a result that compels two inferences: compounds determine choice, and retention of Trial 1 effects is not perfect. The same reasoning and conclusions apply to the 44% choice in Trial 3 of Problem 111. Two further comparisons of Trial 3 data allow inferences about strength of compounds. Problems I1 and IV of the present experiment had performance levels of 77% on Trial 3 . This strength derives from a component once rewarded (and partially forgotten) and a positive compound twice rewarded. TABLE XI

ESTIMATESOF

THE USE OF COMPOUNDS USINGTRIAL2 FROM EXPERIMENTS TWO AND THREE

Problems compared

Compound ~~

Positive

Negative

DATA Percentage differences

~

Experiment 3, Problem I1 minus Experiment 2 , Problem I1 73-65% Experiment 3, Problem IV minus Experiment 2, Problem I 73-63% Experiment 3, Problem I minus Experiment 2, Problem I1 70-65% Experiment 3, Problem 111 minus Experiment 2, Problem I 6663%

8 10

5

3

To subtract out the component contribution, we go back to the third trials of Problems I and I1 of Experiment Two for estimates of the strength of a form component (56%) and a color component ( 5 2 % ) after a single reinforcement and the retention loss suffered during an intervening trial. The differences between 77% and each of the latter percentages are 21% and 2 5 % . These are our measures of the strength of positive compounds. They are considerably higher than the estimates of compounding in Table XI, an understandable outcome, since these compounds have been twice, not once, rewarded. B. Color-Form Efects. The greater ease of form over color as a component dimension turns up again in the third trial of the Standard Problems. The difference between 92% (Form) and 83% (Color) is not statistically reliable, but coupled with earlier findings probably represents a real difference. A significant color-form difference does appear in comparing the third trial of

338

Discrimination Learning of Retardates Problem I (31%) and Problem I11 (44%). Here the form component of Problem I resists the competition of the compound to a greater exent than the color component of Problem I1 resists the conflicting compound. However, the expected color-form difference does not appear between Problems I1 and IV. C. Retention. The below chance performances on Trial 3 of Problems I and I11 could not have occurred unless the children had forgotten what they learned on Trial 1. The retention loss applies clearly to compounds, for if they remembered the Trial 1 compound, performance would be at a minimum of 50%, and higher if they remembered anything about the component. This retention loss of compound information is nicely analogous to the forgetting of components in Experiment Two, under the same conditions of delayed testing, W e speculate that some events during Trial 2 are likely responsible (rather than mere passage of time) for the loss, but what these are we do not yet know. 5. Brief Summary Problems were arranged so performance would reflect the influences of components plus one compound cue. Comparisons of the results with earlier findings led again to the conclusion that compounds are partially learned on Trial 1 and to some extent forgotten during Trial 2. Twice rewarded compounds are stronger than once rewarded, and positive compounds are stronger than negative. Form as a component tends to be stronger than color.

D. EXPERIMENT FOUR: D DIMENSIONAL PROBLEMS WITH VARIABLE IRRELEVANT DIMENSION

A

1. Introduction

Our previous tests for strength of pure component learning after a single reinforcement have been carried out in the presence of constant irrelevant dimensions of form and color. The present experiment uses variable irrelevant dimensions of form and color and assesses the strength of components after 1 and 2 reinforcements. The question of variability in irrelevant dimensions is a crucial one for theory construction. It has been argued by some theorists (Restle, 1955; Bourne & Restle, 1959; Restle, 1962) that only dimensions which vary (i.e., have 2 different cue values associated with the 2 stimuli of a 2-choice problem) contribute cues to the set available for learning. They define an irrelevant dimension as one for which the 2 varying stimuli provide a basis for differential response, but are not correlated with reward. This notion has intuitive appeal, and would add greatly to theoretical simplicity by allowing the number of irrelevant dimensions

339

Betty /. House and David Zeaman to be experimentally manipulated and counted. Support for the definition is found in results of Bourne and Restle. They showed that learning speed increases with number of relevant dimensions, and that learning speed decreases as number of varying irrelevant dimensions is increased. The present experiment compares performances under constant and varying irrelevant conditions as a test of the Bourne and Restle assumption. A single component dimension (color or form, without compounds), was made relevant. 2. Design Relevant cues in a discrimination are those correlated with reward; the cues of irrelevant dimensions are totally uncorrelated with reward. Several methods can be used to destroy the correlation of a dimension and reward thereby rendering it irrelevant. One is to make the dimension constant; nothing correlates with a constant. Another is to allow the dimension to have two values but randomly associate these with reward. A third is to change continuously the values of the dimension, a new pair appearing on every trial. It is this last method that we have chosen for the present experiment. It has the virtue of simplicity of interpretation. Only components can be used for solution, while compounds of color and form cannot provide conflict or facilitation. The formal design of the experiment is factorial: 2 x 2 x 3 x 17, or Conditions (color or form relevant) -by-Conditions (constant or variable irrelevant cues) -by-Trials (three) -by-Subjects (seventeen). Table XI1 outlines 12 subconditions of the experiment. The 17 subjects contributed individual percentages to each of the 12 cells of Table XI1 (a total of 204 scores), completing the design.

3. Method A. Procedure. During each daily session, 2 each of the 4 types of problems outlined in Table XI1 were given. Each of the 8 position sequences appeared once per daily session. Subjects were run for 16 days providing 32 problems under each of the 4 conditions. Other procedural details were the same as in the preceding experiments. 8. Subjects. The 17 subjects had mean MA of 74 months (range: 51-96), mean I Q 49 (range: 30-68), and mean CA 169 months (range: 117-228).

4. Results and Discussion A. Component Learning With Variable Irrelevant Dimensions. The decremental effects of variability in an irrelevant dimension are consistent and large in the data of Table XII. Problems I and 11, with variable irrelevant color and

340

Problem

Cue value Stimuli Example Trial 1 Available components Compounds % Correct Cue value Stimuli Example Trial 2 Available components Compounds $6 Correct Cue value Stimuli Example Trial 3

b 3

k

Available components Compounds 96 Correct

Form relevant, color variable and irrelevant

+

-

ClFl CZFZ Red Blue Square Triangle Color, form Both 51

+

C A C4F2 Black Yellow Square Triangle Form None 63

+

-

CSFl CSFZ Green Brown Square Triangle Form None 61

Color relevant, form variable and irrelevant

+

-

+

CZF4 Blue Cross

CiFi CzFz Red Blue Square Triangle Color, form Both 57

CiFa Red Circle

Standard form

+

+ ClFl Red Square

Color None 61

+

CiFj Red Star

CzFe Blue Diamond Color None 62

-

ClFI CiF2 Red Red Square Triangle Form Both 53

+ CiFi Red Square

ClFZ Red Triangle Form Both 85

CiFz Red Triangle Form Both 86

Standard color

+

CiK CZFl Red Blue Square Square Color Both 44

+ CiFi Red Square

CzFi Blue Square Color Both 66

+ CiFi Red Square

CzFi Blue Square Color Both 86

Betty J. House and David Zeaman form, respectively, yield performance levels well below those of their Standard Problem control conditions (Problems 111 and IV), especially on Trial 3. A factorial analysis of variance on the data of Trials 2 and 3 showed reliable main effects for Variable-versus-Constant ( V ) , and Trials ( T ) , but not for Color-Form (C). Reliable interactions of the V factor are V X C and V T. These are interpreted to mean (a) that form is a stronger relevant dimension than color when coupled with a constant irrelevant dimension but not a variable irrelevant dimension, and (b) that variability in irrelevant dimensions weakens the improvement that ordinarily comes with practice. Performance levels on Trials 2 of Problems I and I1 are sufficiently low, 63% and 61%, to raise a statistical question: has a reliable amount of component learning taken place after a single reinforcement? To answer this, a separate variance analysis was done on the data of Trials 1 and 2 of just the 2 Variable Irrelevant Conditions (Problems I and 11). The results showed a significant main effect of Trials ( p < .Ol), but no reliable Color-Form effects nor C x T interaction. Pure component learning in significant amount is generated under conditions of variable irrelevant dimensions, but two reinforcements are clearly not better than one. This contrasts with the findings for compounds; Experiment Three demonstrated that twice rewarded compounds were superior to once rewarded. To what should we attribute, theoretically, the differences between performances under constant and variable irrelevant conditions? One way of handling the problem is to assume, as does Restle, that constant dimensions exert no control of discriminative behavior, and further postulate that discrimination learning is inversely related to the number of variable irrelevant dimensions. These two assumptions predict our results (and others) well enough. Another theoretical tactic derives the superiority of the Constant Condition from the presence of an additional pair of cues-positive and negative compounds-consistently associated with reward. Add to this the assumption that discrimination learning is a direct function of the number of relevant dimensions, and the results of the present experiment are again predicted. These alternatives are not mutally exclusive; there is no obvious reason why both theoretical views may not be true: the Constant Condition is superior to the Variable because the Constant Condition has more relevant dimensions, and the Variable Condition has more irrelevant dimensions. If the observed Variable-Constant difference is to be interpreted as due to differences in number of relevant and irrelevant dimensions, the further question then suggests itself: is it the difference in number of relevant and irrelevant dimensions operating during training, or testing, or both? The answer comes from a comparison of the results of Trial 2 of the Variable Conditions with those of Trial 2 of Problems I and I1 in Experiment Two. In that experiment, it will be recalled, the first trials of the experimental problems were the same as

x

342

Discrimination Learning of Retardates in the present experiment-2 variable dimensions. The second trials of these problems were also alike in both experiments in that only components were available for problem solution. The difference between the second trial conditions lies in the constancy of the irrelevant dimensions in Experiment Two. But this difference made no difference; performances were about 63% regardless of the constancy or variability of the irrelevant dimension while testing (on Trial 2 ) for the learning that occurred on Trial 1. This is a surprising result, and one that bears on theory. Suppose, for instance, that irrelevent variability tended to attract attention away from the relevant dimensions. I n this case, learning on Trial 1 of the to-be-relevant dimension would suffer, and performance would suffer again on Trial 2 if the testing conditions included distracting (variable) irrelevant dimensions. I n short, if irrelevant variability causes increased competition for limited attention, the result would be decremental during both training and testing. As a consequence, we should expect poorer performance in this experiment than in Experiment Two. Not having obtained a difference we are led to question whether variability is a particularly strong determinant of attention under the conditions of these experiments. Perhaps constant dimensions also claim their share of attention. An anecdote may make this point clearer. One of our unusually talkative retardates spontaneously volunteered this explanation of his successful solution of the candy-finding problems : “It’s under the round one.” And indeed it was. The stimuli were a red circle versus a green circle. B. Color And Form. Form Problems were reliably easier than Color Problems, but only when the irrelevant dimension was constant (Standard Condition), not when the irrelevant dimension was variable (Problems I and 11). This difference is reflected in the significant interaction variance (Color-Form times ConstantVariable) in the data of Trials 2 and 3. The dominance of form components over color components appears to be larger for the subjects of this experiment than for those of the previous two experiments. C . Retention. No direct measures of retention loss come from the data of Table XII, but the poor performances on Trial 3 of the Variable Irrelevant Problems are suggestive. If the component information of Trial 1 tends to disappear during Trial 2 (as we concluded happened in Experiments Two and Three) then the reinforcing effects of Trial 2 might be largely offset by retention loss. Such an explanation would account for the lack of improvement on Trial 3. If true, these subjects would never solve this type of variable irrelevant problem at criteria1 efficiency no matter how many additional trials were given. The speculation is worth checking. The experiment remains to be done. D. Brief Summary. Variable irrelevant component dimensions are associated with lower levels of discriminative performance than constant irrelevant dimensions. This may be attributed either to the greater number of relevant dimensions

343

Betty

I. House and David Zeaman

(including compounds) in the Constant Condition, or to the greater number of irrelevant component dimensions in the Variable Conditions, or to both. Irrelevant variability during training (Trial 1) was found to be responsible for performance decrement more than irrelevant variability during testing (Trial 2 ) , an outcome not readily handled by assuming that variable irrelevant dimensions are simply more distracting than constant dimensions. Other effects included the reappearance of Color-Form differences, and the suggestion of component forgetting.

E. EXPERIMENT FIVE: CONFLICTAND COMBINATION OF CUES 1. Introduction This experiment, like Experiment Four, studies the effect of variability in an irrelevant dimension. It differs from the preceding experiment in using just 2 values of the irrelevant dimension for each problem, a more usual procedure in standard learning experiments (e.g., Bourne & Haygood, 1959; Bourne & Restle, 1959) than that of introducing 2 new values of the irrelevant dimension on each trial. With 2 cues for each dimension, pairing may be done in 2 ways, e.g., red square vs. green circle and red circle vs. green square. Over a large number of trials many random orders or sequences of the 2 kinds of pairs may occur. In the studies of Bourne and others, performance is averaged over a variety of random sequences, thereby providing a measure of variability per se but ignoring effects of particular sequences of pairs. With 3-trial problems, the set of possible random sequences of pairings can be exhausted and each analyzed in detail. The resulting analyses provide information on conflict and combination of cues. The “miniature” nature of the present experiment emerges sharply when it is pointed out that three trials are the minimum necessary to discover if a subject has learned that a 2-valued, variable irrelevent dimension is, in fact, irrelevant. Assume that the experimenter feeds information as quickly as possible: on the first trial 2 cues accompany reward; on the second only 1 retains its association with reward (the subject guesses which); and only on the third trial can the subject show what he knows by ignoring the irrelevant variable dimension. Another way of saying this: it takes at least two trials to establish a correlation of cue and reward, and a third to test for the information. 2. Design Over 3 trials, the possible sequences of random pairings of color and form are limited to just 4, if we take the original pairing as a reference and classify

344

Discrimination Learning of Retardates the remaining 2 trials as either the same or different. These 4 sequences, comprising our Experimental Conditions, are symbolically identified in the following way. W e refer to the pairing presented on Trial 1 as A and the opposite pairing as A’; the 4 sequences may then be specified as AAA, AAA’, AA’A. and AA‘A’, as outlined in Table XIII. In Condition A A A all 3 trials are TABLE XI11 STIMULUSARRANGEMENTS AND REWARD VALUESPOR STANDARD AND EXPERIMENTAL CONDITIONS Experimental problems Standard problems

AAA

AAA’

AA’A

AA‘A’

+ -

+ -

+ -

+ -

+ -

CIFI C2F2 C I R C2R CiFz CzFi

CIS CzK CiFz C z R C I R C2F2

CIK CzFz

+ -

+ -

+ -

Color Trials

NO. 1 NO.2 NO. 3

CIR CzS CIK CzFz CIK C2F1 CiFi C2Fz C I S G ~ I CiFt C2F2

C1K C1F2

C2K CzR

Form Trials

+ -

+ -

identical, and the Color and Form Problems are identical. From the subject’s point of view this condition is simply a problem with both color and form relevant, and is so regarded in our analysis. In the other 3 conditions, the previously rewarded color and form cues are in conflict either on Trial 3 (AAA’) or on Trial 2 (AA’A and AA’A’) . Performance on the first conflict trial must be at chance, averaging over Color and Form problems, since the child has no way of knowing which dimension is relevant. Following a conflict trial on Trial 2, the original pairing may be repeated on Trial 3 (AA’A) or a repetition of the Trial 2 pairing may occur (AA’A’). Perfect performance can occur on these third trials provided the child makes use of all the available information on Trial 2 to discover which dimension is relevant and which cue of that dimension is correct. The presence of a 2-valued, variable irrelevant dimension may depress performance in either of two ways.

34s

Betty I. House and David Zeaman ( A ) The presence of an irrelevant distinguishing feature of the stimuli may decrease the effectiveness of the relevant dimension in some way. Translating this theoretically, Restle might argue that learning is lowered by the reduction in either proportion of relevant cues in the total set (Restle, 1955; Bourne & Restle, 1959) or proportion of correct strategies (Restle, 1962); in attention-theory terms, it might be argued that the presence of a competing irrelevant dimension may, for a subject of limited intelligence, decrease the probability of paying attention to the relevant dimension. (B) A second possible decremental process occurs when the same 2 irrelevant cues reappear on subsequent trials. If the subject forms approach tendencies to one of the irrelevant cues, an error will be made when that cue is paired with the incorrect relevant cue. It is this second factor which leads us to expect that the 4 types of random sequences outlined in Table XI11 will produce quite different performance curves. An additional purpose of the present experiment is the comparison of two groups of children matched for MA but differing in IQ. Two separate but procedurally identical experiments were run-a study of performance of normal nursery school children by Hoffman, and a study of retardates’ performance by House.

3. Method A. Procedure. Daily sessions included 8 problems, 2 each of the Standard Color and Form Problems, and 2 each of the Experimental Color and Form Problems. Subjects were run for 16 days, providing 32 problems under Standard Color and Form Conditions and 8 problems under each of the Experimental Color and Form Conditions. Other procedural details matched those of preceding experiments. B. Subjects. The retardates run by House totaled 21, with mean MA 68 months (range: 44-96), mean IQ 46 (range: 26-73), and mean CA 166 months (range: 117-230). The 1 2 normal children, run by Hoffman, had mean MA of 68 months (range: 48-107), mean IQ 120 (range: 98-141, except for 2 extreme scores of 68 and 170), and mean CA 56 months (range: 47-67). 4. Results and Discussion Performance curves for the various conditions are shown in Fig. 5. The type of random sequence clearly affects performance. Details are discussed in the following section. A. Color, Form, And 3-Dimensional Problems. Figure 5 (a) presents learning curves for the Standard Color and Form Problems and for Experimental Condition AAA, with color, form, and compounds all relevant. Color appears to

346

Discrimination Learning of Retardates be the most difficult problem and the 3-dimensional problem the easiest, at least for the normal group. Figure 6(a) presents the data in another form by plotting percentage correct on Trial 2 as a function of type of problem for the normal and retarded groups. The corresponding analysis of variance (Analysis 1) of Table XIV shows that the groups differ significantly and that problem type has a significant effect. The superiority of form over color performance is confirmed here for the combined data of the 2 groups ( t = 6.5, p < .Ol), but performance on the 3-dimensional problem is not superior to that for form alone for the groups combined ( t < 1) . The data suggest that an additional relevant dimension improves performance of the normal group but not the retarded group. But failure to obtain a significant Groups x Conditions interaction leaves this issue in doubt. A failure to find the 3-dimensional problem easier than a Standard Form problem is not crucial to the theory that learning increases with number of relevant dimensions. For these well-practiced subjects, form alone is a strong dimension. Therefore, any predicted improvement for an additional relevant dimension would necessarily be small and easily obscured by chance variability. The data will be shown later not to be quantitatively inconsistent with a mathematical model that assumes facilitative effect of redundant, relevant dimensions. A more adequate test requires weaker dimensions. Warren (1953), for example, failed to find facilitation by addition of form or size cues to color cues in monkey performance (color is a strong dimension for monkeys) whereas the combination of two weaker dimensions, size and form, produced faster learning than either alone. Our previous research (Zeaman & House, 1963) with naive retardates and the traditional Trials-by-Subjects Design has shown a much larger facilitative effect of redundant relevant dimensions. The 3-trial procedure dampens this relationship somewhat, possibly because it narrows attention to just a few dimensions (color, form, and compound) which have a high probability of being relevant. B. Color-Form Preference On Conflict Trials. The effect of pairing an irrelevant cue with the incorrect relevant cue after one or two previous pairings with the correct cue may be seen in Fig. 5 (b) (Trial 3) and in Figs. 5 (c) and 5 (d) (Trial 2 ) . In each case, performance is above chance when form is the relevant dimension and below chance when color is relevant, demonstrating that a form cue is preferred over a color cue on conflict trials even though the two have received equal numbers of rewards. Degree of preference is the same on Trial 2 as on Trial 3. The data from all 3 conflict trials (from Figs. 5(b), 5(c), and 5 ( d ) ) are combined and replotted in Fig. 6(b). Form preference is confirmed by Analysis 2 of Table XIV for the combined data of normal and retarded subjects. No group differences were found. If approach tendencies to the color and form cues were equal in strength, we would expect performance to be at chance on these conflict trials since the

347

Betty

1. House and David Zeaman

100

90 I0

W

a 80 a 0 0

I-

t

7o

W 0

60 P

z

2 z

50

40

I

2 TRIALS

3

TRIALS

Fig. S ( a ) T h e functions coded “Color” and “Form” are for the Standard Color and Standard Form Problems. These are 2-dimensional with 1 component, color or form, relevant plus the compound. The functions labeled “Color and Form” represent the Experimental Condition AAA. TheJe are 3-dimensional problems. Data for Normals and Retardates are plotted separately. ( b ) The effects of confiict of color and form cues on the third trial are shown in the results of Condition AAA’.

348

Discrimination Learning of Retardates 100

90 I-

: 80 a a 0

0 k

70

z w

u

6 60 n 2

a w 50 I 40

I

2 T R I A L S

3

I

loo 90

I

2 T R I A L S

Fig. 5 . (cont’d). (c) Conjlicj of color and form cues on Trial 2, followed by a return to the conditions of Trial I, is shown in the data from Experimental Condition AA’A. ( d ) Second trial conjlict followed by a third trial identical to the second yields the functions for Condition AA’A’.

349

Betty 1. House and David Zeaman subject has no way of knowing which dimension is relevant. Also, performance would be at chance if approach tendencies were formed to compounds alone; the previously correct and incorrect compounds are destroyed by the recombination of cues. From the obtained, nonchance performance, we may conclude that approach tendencies are formed to the component dimensions and that approach tendencies to form are stronger than those to color. c. Trial 3 Performance After A Conflict Trial. Following a conflict trial, Trial 3 performance is better if the Trial 2 stimuli are repeated (AA’A’) DATA

FOR ANALYSIS I 1

I

TRIAL 2

FIRST CONFLICT TRIAL

I A A‘&

COLOR

FORM FORM

A A’A’

Pig. 6. ( a ) Histogram of the Trial 2 data of Pig. > ( a ) used in Statistical Analysis 1 . Performances on two and three dimensional problems are compared for Normals and Retardates. ( b ) Preferences of form over color on initial conflict trials are shown for Normals and Retardates. ( c ) Triat 3 performances for Normat and Retardates under Conditions AA’A and AA’A’. Differences between the conditions support inferences on retention of compound information.

than if the Trial 1 stimuli reappear (AA’A). This effect may be seen by comparing the Figs. 5(c) and 5(d); it is displayed more clearly in Figure b ( ~ ) for the combined color and form data. Analysis 3 of Table XIV shows the difference to be significant. This difference allows us to make certain inferences about the strategy being used by the subject. For instance, if the subject uses the information supplied by his Trial 2 outcome to determine which dimension is relevant, then chooses the correct cue of that dimension on Trial 3, no difference would be predicted between Conditions AA’A and AA’A’. W e reason, therefore, that other factors must be operating. One factor that would produce such a difference is instrumental habit reversal. Suppose the subject chooses the component F, on Trial 2 of a color-relevant

350

Discrimination Learning of Retardates TABLE XIV ANALYSES OF VARIANCE FOR DATAOF FIGS. 5

Analysis 1 Data: Errors on Trial 2-[Figs.-5(a), 6(a)] Groups: Normal :vs. Retarded Conditions: Standard Color vs. Standard Form vs. AAA-Color Source

df

Groups Error (a) (ms 1.29.6)

31

1

AND

6

and Form

P

P

4.74

< .05

31.32 2.83

< .01

P

Conditions Groups X Conditions Error (b) (ms = 5.45)

2 62

Source

df

F

Groups Error (a) (ms = 5.74)

1 31

<1

1

19.56 <1

< .01

P

P

3.12

<.lo

Conditions Groups X Conditions Error (b) (ms = 12.30)

2

1

<.lo

31

AnalyJis 3 Data: Errors on Trial 3 [Figs. 5(c) and 5(d); Fig. 6(c)] Groups: Normal vs. Retarded Conditions: ExperimentalConditions AA’A vs. AA‘A‘ Source Groups Error (a) (ms = 4.90)

1

Conditions Groups X Conditions Error (b) (ms = 2.66)

1

66.0

1


< .01

31

35 1

Betty J . House and David Zeaman problem, discovers that it is incorrect, and so chooses the component F , on Trial 3. An error then occurs under Condition AA’A, but a correct response under Condition AA’A‘. Another factor leading to better performance on Trial 3 of Condition AA’A’ is the tendency to learn to approach compounds, given that more recently rewarded compounds retain stronger approach tendencies than less recently rewarded compounds. Note that on Trial 3 of Condition AA’A’, the correct compound has appeared on the immediately preceding trial while Trial 3 of Condition AA’A requires the subject to recall the correct compound from Trial 1. The demonstrated superiority of Condition AA’A‘ supports the view that one or both of these factors is affecting performance. D. Effect Of ZQ Differences. The direction of the results is very similar for both normal and retarded groups. One difference between the groups is that the normals learn significantly faster than retarded children on the Standard Problems. (See Analysis 1, Table XIV.) This result is of especial interest since both groups have been throughly pretrained and are at or near asymptote with respect to learning set. There is a suggestion, also, in Analysis 1 of an interaction between groups and problem type but the effect fails to reach the .05 significance level. E. Some Effects of M A Differences. (A) Use of position cues. The procedures used in the present experiments tend to reduce the use of position cues since these are never relevant. However, subjects still make a few errors which can be attributed to position cues, even after a pretraining procedure in which subjects learn to rely mostly on cues of other dimensions. The response patterns of the subjects of the present experiment were analyzed to determine to what extent position cues or position hypotheses were being used. In making the analysis, Levine’s (1959) hypothesis model was applied to each child individually. Levine’s model provides an estimate of the proportion of problems on which each of a set of hypotheses is used. The model uses a partitioning procedure plus the assumption that one and only one hypothesis is present during each 3-trial problem. Figure 7 presents rolling averages for three types of position hypotheses : position preference, position alternation, and win-stay lose-shift (with respect to position). The most frequent position hypothesis, win-stay lose-shift, shows a slight downward trend as MA increases. Position preference, almost as high as win-stay loseshift at the lowest MA level, shows a much sharper drop for higher MAS. Position alternation is fairly constant and possibly not significantly different from zero except for one child whose score was not included in the averages on the grounds that it was quite atypical. This one child had a position alternation score of .30. (B) Learning rate and color-form preference. Figure 8 shows rolling averages of numbers of errors on the Color and Form Standard Problems

Discrimination Learning of Retardates and also the percentage of times the previously correct form was chosen on conflict trials (Trial 3 of Condition AAA', and Trial 2 of Conditions AA'A and AA'A'). Errors decrease as MA increases for both Color and Form Problems in a fairly parallel fashion. Preference for the form comPOSITION HYPOTHESES

WIN-STAY, LOSE-SHIF T I

.+ a % ' '

A LTE R N A T I ON CE

MA

( I N YEARS)

Fig. 7. Strengths of three position hypotheses are shown in relation to mental age. Strategy indices were calculated using Levine's (1959) methods with retardate data.

-+"

ro

1.4

FORM PREFERENCE

LL

,,,,,,,,,,

#

; m

11111111111111

1.2

a

0

a

1.0

0

so n

=

I

2

0

4

I

.8

=

F

40

," n

m

.6

I

I

3-5 4-6 5-7 6-8 MA ( I N YEARS)

3

30 m

2 c)

m

Fig. 8. Errors on Standard Color ( C ) and Standard Form ( F ) Problems as a function of mental age of retarded children. Preference for form over color on conflict trials (using ordinate at the right) inrreases with mental age.

ponent on the conflict trials increases from near 50% at the lower MA level to over 60% at the higher level. Both effects, the increase in learning rate and increase in preference, are significant at less than the .05 level. One child from the MA 7-8 group has been excluded from this analysis since he showed a sizable, atypical preference for the previously correct color component of 68%. Thus, while comparable to the rest of the group as

353

Betty I. House and David Zeaman measured by degree of component preference, he differs in preferring color over form. In a previous discussion it was pointed out that a component preference indicates that compounds are not used exclusively. For example, if a child has learned that red square is correct and green circle is incorrect, but not that square is correct and circle incorrect, he will be at chance when presented with red circle and green square. Since the subject does, in general, prefer the green square under these circumstances, we infer some component learning. From the MA function of Fig. 8, we may also conclude that component learning increases with MA. The lowest-MA group is, indeed, at chance when presented with red-circle-green-square choice. Given this evidence alone it might be argued, as Werner (1948) and others have, that as developmental level increases so too does “abstract” ability. That is, higher M A subjects can respond to “parts” of the stimulus configuration whereas lower MA subjects require the “whole” stimulus for choice. However, the results from Experiment One lead us to the opposite conclusion. In the discussion of individual differences it was pointed out that use of compounds increases with MA. This finding is more in agreement with the findings of Kendler et al. (1962) with respect to verbalization. It was found that children of a higher developmental level, when asked to explain how they had solved problems with stimuli differing in brightness and size, were more likely to mention both dimensions than were children from lower developmental levels. A comparison of data from Experiment One and Five suggests that it is improper to conclude that if subjects use compounds more, they necessarily use components less. A conclusion more in keeping with the data is that children of higher M A learn more about both aspects of the stimuli. 5. Brief Summary The experiment paired cues of a 2-valued irrelevant dimension with the positive and negative cues of the relevant dimension in such a way as to yield information on conflict and combination of cues. Results showed that 3 relevant dimensions (color, form, and compounds) were slightly, but not significantly, more effective than form-plus-compounds. The Standard Form Problem was significantly better than the Color Problem; subjects preferred a previously rewarded form cue over a previously rewarded color cue when the two were in conflict. Results from a group of normal children matched in MA with the retardates showed qualitatively similar results; however, the higher IQ children learned faster. It was shown that as MA increases from 44 to 96 months, there is a decrease in effect of positional cues, an increase in rate of learning, and an increase in form preference on conflict trials.

354

Discrimination Learning of Retardates

111. Mathematical Treatments A. OUTLINEOF ATTENTIONTHEORY The probability tree of Fig. 1 outlines our Attention Theory of retardate discrimination learning. It is an elaboration of Wyckoff’s (1952; 1954) Observing Response Theory, and we have described it in detail elsewhere (Zeaman & House, 1963). The mathematical portions of the model necessary for the treatments given in this section can be stated briefly. These consist of a family of linear difference equations applied to the probabilities of instrumental responses Pr(i), and observing or attending responses Po({). On each trial the subject is assumed to look at one of i dimensions with probabilities Po(i,, following which an approach response to the correct cue of the observed dimension is made with probability PY(~). If a trial n ends in reinforcement, the probabilities acting on that trial are increased by the difference equations

+

Pr(i.,+l) = Pr(i,,) pO(;,~i) = pQ(i,,)

041

- Pr(i,n))

+ @o(l - PO($-,))

(1) (2)

If nonreinforcement ends a trial, extinction reduces the acting probabilities by the equations P V ( ~= . ~P ~ Y ()~ , , ) erPr(i.n)

PO(i,*l) =

PO(i,n)

- BOPO(i,*)

(3) (4)

Two other equations complete the rules governing probability changes. If the jth dimension is observed and a trial ends in nonreinforcement, the ith dimension undergoes some indirect or parasitic acquisition according to the equation

where Pocj-,,) is the probability of observing the jth dimension on the nth trial. The equation is derived from the notion that probabilities of nonelicited responses are changed indirectly in such a way as to preserve their ratios. The final equation describes the decrease in probability of observing the ith dimension when the jth dimension is observed and the trial ends in reinforcement. This indirect extinction equation turns out to be identical to Eq. (4) when the preservation of ratios assumption is made. The instrumental probabilities are conditional. If the ith dimension is not observed, the conditional probability P r ( i , has no effect on behavior and

3s5

Betty I. House and David Zeaman its value is not changed by the outcome of the trial. Suppose the discriminanda are red and green in color; if the subject does not observe color on a given trial, his choice will not be affected by his tendency to choose red so his tendency to choose red on a subsequent trial, when he does observe color, is not changed. With only 2 values of each dimension present, equations for indirect acquisition and extinction of the instrumental response probability can be stated as follows. Equation (1) shows the increment to Pr({) when Rip (see Fig. 1) is not rewarded; Eq. ( 3 ) shows the decrement to Pr(i, when Ri’ is rewarded. Both the observing response and the instrumental response are unobservable. The experimenter sees only the overt choice; he cannot determine, when a red square is chosen, whether the subject has responded to “red,” to “square,” or to neither of these. An equation is required to relate the probabilities of these unobservable responses to the probability, P, of a correct overt response. For the situation with a single relevant dimension with probability Po(,, of being observed the basic equation is

+

p = Po(l)Pr(l) +(I - PO(1)) (6) where the unity subscript refers to the relevant stimulus dimensions. This equation sums the probabilities of two different ways of responding correctly: (a) observing the relevant dimension and choosing the correct cue (with probability Po (l)Pr(l))or (b) observing an irrelevant dimension and choosing the correct stimulus by chance (3 (1 - Po(l))). For multiple relevant dimensions, the basic equation is N.

N.

where N, equals the number of relevant dimensions. For example, for two relevant dimensions

P = PolPrl+ PozPrz

+ (+)(I - Pol - Poz)

B. GENERAL STRATEGY 1. Parameter Estimation and N Ideally we should find values of the parameters e,, e,, (the total number of dimensions) which when used in the theoretical equations would predict all the outcomes of the 5 experiments. W e will not find these. The model can not handle certain features of the data such as the retention loss exhibited in Experiments Two, Three, and Four without additional (retention) postulates. It would be pointless, therefore, to search for a set of precise parameter estimates with the model as it is.

Discrimination Learning of Retardates A different tack has been taken. W e plan to look at the consequences of several radically simple assumptions about parameter values : fixing some a priori (e, and so), fixing others ( P o i ) with the data of the simpler experiments, and transferring all of these to apply to the data of the more complex experiments. Not all of the data will be theoretically described in this way, but most of it will. Agreement of observed and predicted performances establish the boundaries of what a simple theory will predict. Deviations suggest the extent and direction of needed theory modification. 2. All-or-Nothing Learning

A popular assumption of model builders is that of all-or-nothing learning (Estes, 1959; 1961; Bower, 1961a; 1961b; Restle, 1962). At least three good reasons justify this: first, it does no violence to the data of several kinds of associative learning including discrimination; secondly, it represents the view of at least one traditional learning theorist (Guthrie); and lastly, this assumption leads to mathematically tractable models. In our model, all-or-nothing learning is assumed by setting learning parameters equal to unity. W e start out theoretical analyses with the assumption that 0, = 1, which produces 1-trial learning of the correct instrumental response providing that the child is attending to the relevant dimension. The subject will be doing SO with a fixed probability over the 3 trials of each problem if so = 0, our second assumption. No restrictions on the number of possible irrelevant dimensions are made. A final assumption limits attention to a single dimension on each trial; at the moment of choice the child takes only one look. The consequences of this all-or-nothing-learning-with-fixed-attention submodel will be compared with those of another all-or-nothing model not featuring the chaining postulates of Attention Theory. W e call the former the One-Look Model, the latter the Single-Link Model. 3. Constant Attention Probabilities Rational grounds can be offered for assuming constant probabilities of attending to each of the various dimensions (0, = 0). With the %rial minature experiment technique, the experimenter randomly changes the relevant stimulus dimensions every three trials, e.g., from color to form to compounds, and combinations of the three. Other dimensions, such as position, are not consistently reinforced. If we take as our unit of training the experimental session or entire experiment, rather than the problem, what the experimenter has done is to put a more-or-less constant random schedule of reinforcement on the responses of attending to each of the stimulus dimensions. Attention Theory predicts, along with other simple linear models,

3s7

Betty 1. House and David Zeaman that random schedules of reinforcement of any response will tend in the limit to produce matching frequencies of that response. The end result, for our 3-trial procedures, would be constant and fairly high probabilities of looking at color, form, and compounds.

C. EXPERIMENTS ONE AND Two 1. Simpler Problems A good place to begin comparing theory and data is with the results of Experiments One and Two. Each of these included problems having a single relevant dimension. In the first 2 trials of Experiment One, the color-form compound dimension was the sole relevant dimension in the experimental problems. In Experiment Two, the color component dimension or the form component dimension was the necessary basis of discrimination. It is not difficult to derive theoretical equations for the percentages of correct choices on Trials 2 and 3 starting from the assumptions of either One-Look or Single-Link Models.

2. One-Look Model A. One-Dimemional Problemr. Since do = 0, the probabilities Poi of observing any dimension remain constant within a problem. The probability of observing color remains at Poc, form at Po,, and color-form “kompounds” at Pok. On Trial 1 of all problems the probability P of a correct choice is always 4 since the experimenter chooses the positive stimulus randomly. Putting Prl = 3 into the basic equation Eq. (7) will predict this regardless of the other parameter values. On Trial 2, there are 2 ways of making a correct choice, either by looking at the relevant dimension and selecting the positive cue, or by looking at an irrelevant dimension and luckily selecting the correct stimulus object. In Experiment One, the probability of the first way would be PO,)^, the probability of the second, (4)(1 - Pok2). The squared value of Pok is the result of the requirement that the subject look at the compound on the first trial (Pok) and also on the second PO^). The ( 1 - Pok2) expression is the probability of any other combination of two successive observing responses, and (3) is the probability of a correct choice given this incorrect attention. Thus the probability Pz of a correct choice on Trial 2 is given by Eq. (8).

+

Pz = POk2 (+)(1 - P d ) This equation may also be derived by substitution into the basic Eq. ( 6 ) as follows, For Po(l, substitute the value Po,, which is constant. For Prcl) substitute the expected value of Prk on Trial 2, which equals Pok j ( 1 - Pok). Simplified, the expression becomes Eq. (8).

+

358

Discrimination Learning of Retardates In the interest of compactness, we wish at this point to change our notation and replace Pok, Poc, and Po, with just their subscripts, k, t, and f . Equation (8) then becomes

Pz = k2

+ .5(1 - a*)

Pz

+ .5(1 -

(8) expressions can be written for the 1-dimensional color and form p b l e m s (a single relevant dimension) of Experiment Two,

&@dent

= t2

and

(9)

6')

+

pz = f" .5(1 - f") (10) Two-Dimensional Problems. For Trial 2 of the Standard Problems, which have 2 relevant dimensions, one component and a compound, there are 3 ways of making a correct choice on Trial 2. The subject can look at (A) the correct component dimension on 2 successive trials (with probability f" for form), or (B) the correct compound dimension twice, with probability R2, or (C) some other combination of dimensions (1 - f" - R2) with a lucky choice ($). With 8 , = 1, looking at a relevant dimension is the sufficient condition for changing the instrumental Pr of that dimension to unity. Putting these probabilities together according to the rules of the theory [cf. Eq. ( 7 ) ] yields the probability of a correct choice on Trial 2 of a Standard Form Problem, B.

=f"+

pz rk2 and of a Standard Color Problem,

Pa = C'

+ .5(1 -f" - rk2)

+ k2 + .5(1 -

C'

- h2)

(12)

These equations hold regardless of the number of irrelevant dimensions that might be present. C . Parameter Estimation And Transfer. Empirical values of k, c, and f can be found by using the data of Experiments One and Two. In Experiment Two, Problem 1, with form components alone, the observed P , was .65. Using Eq. (lo), f is estimated as follows:

Pz = .65

f=

=f

+ .5(1 - f)

.55

In Experiment Two, Problem 2, with color components alone, Pz was .63. Using Eq. ( 9 ) , we compute t = .51. The value of R can be estimated from the data of Experiment One. If for each subject we take as the measure of compounding the larger Compounding Index, either Positive or Negative, the mean of the group is .66. This value of .66 can be set equal to P, in Eq. (8) and the equation solved for k = .57.

3s9

Betty I. Home and David Zeaman With estimates of A, c, and f , predictions can be made of performances in the Standard Color and Form Problems of both experiments. For the Standard Color Problem, Eq. (12) predicts pz = (.51)’

+ (.57)’ + .5(1 - .512 - .57’)

=

.79

The observed values of P, for the Standard Color Problems of Experiments One and Two are .76 and .77. Predicting P, of the Standard Form Problems with Eq. (11), we arrive at P, = .81. Observed values are .78 and .79 from Experiments One and Two. These tolerable correspondences of data and theory would have encouraged us more if it were not already apparent that certain aspects of the data violate theoretical expectatigns. The model assumes “one-look;” that is, the subject is at the moment of choice attending to precisely one of the competing dimensions. This implies that f c k 1. But our empirical values of f, c, and k already sum to 1.63-embarrassingly high for a probability ! To remedy this defect, we will relax the “One-Look” restriction and develop a Multiple-Look Submodel of Attention Theory, but first we wish to provide some competition for it from a nonchaining, nonattention model.

+ +

3. Single-Link Model A. One-Dimensional Problems. This model is patterned after those constructed by Estes (1959) and Bower (1961a; 1961b). For a one-component problem, say color, two all-or-nothing states of conditioning are identified : C and N, indicating that the subject is conditioned to approach the correct color, and not-conditioned to approach the correct color. The conditioning rules of the model are given by a transition matrix showing the conditional probabilities of a transition from a row state, C or N, on Trial n to a column state, C or N, on Trial n 1.

+

Trial n

I C Trial n

N The nth power of this matrix is

I

cll-

360

1

N 0

C

I C N

+1 1-c N

(1

- C).

0 (1 - C).

Discrimination Learning of Retardates Inspection shows that after one or two trials ( n = 1, 2 ) the probabilities of being in conditioned state C are 1 - (1 - C) and (1 - C) 2, respectively, if all Ss are in State N initially. All that is needed to bring this type of model to our data is a pair of rules relating the states of conditioning to performance. The probability of a correct choice is one, given that the subject is in state C; the probability of a correct choice is f given that the subject is in state N. From this collection of assumptions, equations can be derived directly for the probability of a correct response on a 1-dimensional problem for Trials 2 and 3, i.e., P, and P,.

Identical equations can be written for a 1-dimensional form problem replacing C with F, and for a 1-dimensional compound problem by replacing C with K. B. Two-Dimensional Problems. For problems with 2 relevant dimensions, say, form and compound, 4 states of conditioning can be identified, F, K, FK, and N, representing Form conditioned, Compound conditioned, both Form and Compound conditioned, and neither Form nor Compound conditioned, respectively. The transition matrix is

FK F K N

FK

F

K

N

1 K F

0

0 0

0 0 0

1-K O F

0

1-F K

1-F-K

which implies that the conditioning states are independent of each other, and that there is at most one change of state (one element conditioned) per trial. The rule relating the states to performance holds that no error will be made on a trial of a 2-dimensional problem if at least one of the states is conditioned, otherwise the probability of an error is 4. From these postulates it follows that Pz= F + K + .5(1- F - K ) (15) and Ps = F K - FK .5 (1 - F - P) (16)

+

+

Equations identical in form can be written for problems with both color and compounds relevant (Standard Color Problems). c. Parameter Estimation And Transfer. W e pause at this point in theory to look at the data of Experiments One and Two. The 63% correct on Trial 2 of the 1-dimensional color problem of Experiment Two (Problem 2) is set equal to P, in Eq. (13) and the equation solved for C = -26.

361

Betty 1.House and David Zeaman The value of F, obtained by setting Eq. (15) (expressed in terms of F ) equal to .65 (Problem I, Experiment Two), is .30, and the value of K, using the same equation form and the data of experiment One, is .32. Because we have assumed independent dimensions, it should be possible to use these three conditioning probabilities, C = .26, F = .30, and K = .32, in the 2 dimensional problems, the Standard Color and Standard Form Problems. Equation 15 predicts Trial 2 of the Standard Form Problem,

Pz = .30

+ .32 + .5(1 - .30 - .32) = .81

The observed values of this P , from Experiments One and Two were .78 and .79. The prediction for Trial 2 of the Standard Color Problem using the same equation form is .79, while the observed values from Experiments One and Two were .76 and .77. There are no differences between the 2 models in accuracy of predicting 2-dimensional learning from a knowledge of one-dimensional learning up to Trial 2. The 2 models do make different predictions about other aspects of the data, so they are by no means mathematically equivalent. It is clear now, however, that the Single-Link Model has the advantage in not having the three independent probabilities C, F, and K sum to greater than 1. 4. Multiple-Look Model A. New Assumptions. If an Attention or Chaining Model is going to handle the data in a rational way, it appears worthwhile to try to relax the "One-Look" restriction so that the probabilities of looking at the various stimulus dimensions, being no longer theoretically independent, need no longer sum to unity or less. W e have previously (Zeaman & House, 1963) sketched out a Multiple-Look Submodel of Attention Theory, details of which we now present prior to empirical test. Instead of limiting attention to a single dimension per trial, the MultipleLook Model allows for the possibility that one or more stimulus dimensions will be attended to at the moment of choice. The child may look at the color dimension, form dimension, or compound dimension each by itself, or in conjunction one with the other, or only at irrelevant dimensions, or at combinations of relevant and irrelevant dimensions. It is a lax model in its restrictions on attention. Otherwise, the Multiple-Look Model follows all the postulates of the parent Attention Theory, and does not abandon the assumptions of all-or-nothing instrumental learning (8, = 1) and fixed observing probabilities (e, = 0) of the One-Look Model. B. One-Dimensional Problems. The equations predicting performance (P2, P,) on Trials 2 and 3 can be deduced according to the same logic used for the One-Look Model. A slight redefinition of the observing response

Discrimination Learning of Retardates probability is required. In the One-Look Model, c, f, and k are probabilities of attending to exactly one relevant dimension, while in the Multiple-Look Model, c, for example, is the probability of attending to at least the color dimension. It is also assumed that observing response probabilities are independent so that the joint probability of observing two dimensions, color and compound, for example, equals the product, cR. To predict performance on Trial 2 for a problem with two relevant dimensions, color and compound, note that a correct response will be made if the subject looks at color on both trials (cz), looks at the compound on both trials ( P ) , looks at both color and compound on both trials (c2k2), or does not do any of the above but guesses correctly. When c2 and kz are added, the overlap, cW, common to both is added in twice and must be subtracted, so that if we sum all the ways in which a correct response can be made the following expression is obtained. Pz = 8 R2 - C2k2 .5(1 - C' - k2 8 R 2 ) (17)

+

+

+

Comparing this equation with its counterpart [Eq. (12)] in the One-Look Model reveals it to be the same with the exception of the subtraction of the overlap term ( c 2 P ) . c. Higher-Dimensional Problems A n d Comparison Of Models. Comparisons of equations from the three models considered are provided by Table XV. The first comparisons of interest are those of the One-Look and Multiple-Look for one relevant dimension. These turn out to be identical in form, but not, it must be cautioned, identical in meaning. As pointed out in the preceding section, c, f , and R refer to probabilities of attending to only one dimension in the One-Look Model, but in the Multiple-Look Model, these refer to probabilities of observing at least the dimension designated. If for both models, we use the empirical value of P2 for problems of one relevant dimension to fix c, f, and R, these will match in numerical value for the two models, given the identity in form of Eqs. (10) and (19). Thus c = .51, f = .55, and k = .57 for both attention models. These values can be used to predict Trial 2 performances for the 2-dimensional problems using Eq. (17). The Multiple-Look Model predicts .75 for the 2-dimensional Standard Color Problems (observed .76 and .77) and .76 for the Standard Form Problems (observed .78 and .79), predictions well within the bounds of experimental error. We look now to remaining aspects of the data.

D. FURTHERAPPLICATIONS OF

THE

MODELS

1. Standard Problems Six replications of the Standard Color and Standard Form Problems have been carried out, one in each of the first 4 experiments and 2 in the last experiment (1 for normals, 1 for retardates). As a review of these results,

363

TABLE XV EQUATIONSFOR PERFORMANCE ON PROBLEMS WITH ONE,Two, AND THREE RELEVANTDIMENSIONS PREDICTEDBY THREE SUBMODELS Dimensions

Trials

One-look

Multiple-look

Single-link

Discrimination Learning of Retardates the Trial 2 percentages for Color were 76, 77, 80, 66, 66, and 75 with a mean of 73 +- 7. Trial 3 percentages were 78, 85, 83, 86, 80, and 87 with a mean of 83 5. For Form, the corresponding percentages for Trial 2 were 78, 79, 79, 85, 80, and 81 with a mean of 80 t 5 ; for Trial 3, 88, 87, 92, 86, 82, and 88, with a mean of 87 f 5. Table XVI summarizes the relations between these data and the models. TABLE XVI MEAN OBSERVED VALUESOF Pz AND P3 FOR THE STANDARD COLORAND STANDARD FORM PROBLEMS, AND CORRESPONDING VALUESPREDICTED BY Two MODELS Predicted Problem Color Form

Trial

Observed

Multiple-look

rt rt

.a4

2

.73

3

.a3

2

.80 c!

3

.a7

rt

.07 .05 .05

.05

Single-link

.75

.79 .91

.76 .a5

.a1 .93

Predictions by the Multiple-Look Model correspond more closely to the data than those of the Single-Link Model, which tends to overestimate the third-trial performances. It should be pointed out that neither model is permitted any degrees of freedom in making these predictions; that is, the parameters were all fixed by performance on the 1-dimensional problem. 2 . Experiments One and Two: Trial 3

Application of the models to the Trial 3 data of Experiment One is possible but more complicated than we intend to get in the present paper. The Trial 3 data of Experiment 2 are obviously unpredictable by either model. The delayed testing of components introduces a large retention loss unpostulated by the models. If this effect proves general, theory construction can be directed toward its prediction. Adding a retention loss factor would help the Single-Link Model predict third-trial performances more accurately, and hurt the Multiple-Look Model whose predictions are fairly accurate as they stand. More research is needed to find out if there is any retention loss under the conditions of the Standard Problem. If it should turn out that there is, then the Single-Link Model, equipped with a retention postulate, may be the better model. 3. Experiment Three Performances on Trial 2 of this experiment are supported by component cues and one compound cue. W e can use the data of Experiment One to

365

Betty J. House and David Zeaman estimate effects of positive and negative compounds separately. For 10 subjects in Experiment One comparable to those in Experiment Three, the mean Positive Compounding Index was .62, the mean Negative Compounding Index .56. Using these values to compute k in Eq. (19) we get .49 and .35, respectively. These values, in turn can be used in Eq. (17) together with c and f values from Experiment Two to predict P , performances for these Component-plus-one-compound-cue conditions of Experiment Three. Parallel logic leads to corresponding deductions for the Single-Link Model. Table XVII

TABLE XVII THEORETICAL AND OBSERVED PERCENTAGES OF CORRECT CHOICES ON TRIAL2 OF THE COMPONENT-AND-ONE-COMPOUND-CUE PROBLEMS Predicted

Form

Color

Positive Compound Negative Compound Positive Compound Nelrative Compound

Observed

Multiple-look

Single-link

.73

,74

77

.70

.69

71

73

72

75

.66

.68

.69

I

shows that the predicted values of both models are comfortably close to the data, with the multiple-look values slightly more accurate. The Trial 3 percentages of this experiment, however, like those of Experiment Two, are afflicted by retention loss and are theoretically awkward for both systems. 4 . Experiment Four The first 2 trials of this experiment are theoretical replicates of those of Experiment Two, since the models do not distinguish between constant and variable irrelevant dimensions, when the number of relevant dimensions is controlled. The Trial 2 percentages of the two experiments should therefore be the same. They are reasonably close. P,’s for Color and Form in Experiment Two were .63 and .65; in Experiment Four, these were, respectively, .61 and .63. The differences are easily attributable to slight group differences. Using this group’s own Pz values to predict P8 with Eq. (20) leads to the contents of Table XVIII. These predictions are seriously off and in a direction suggestive of retention loss. Apparently the use of a variable irrelevant dimen-

366

Discrimination Learning of Retardates TABLE XVIII OBSERVED AND PREDICTED VALUESOF THIRDTRIALPERFORMANCES WITH A SINGLE RELEVANTCOMPONENT AND VARIABLE IRRELEVANT DIMENSION Predicted

Color Form

Observed

Multiple-look

Single-link

.62

.6? .69

.7Q .73

.61

sion produces forgetting not observed with constant irrelevant dimensions. For theory construction, this implies that a retention postulate may be needed only for certain classes of experimental operations. Variability in irrelevant dimensions may be one of the classmarks. 5 . Experiment Five Three aspects of this experiment are within easy reach of the models: the 3-dimensional problems (Problem A A A ) , the 2-dimensional problems (Standard Color and Form), and the problems with conflict of cues on the second trial (Problems AA’A and AA’A’) . A. T w o And Three Dimensional Problemr. The 2-dimensional problems have already been described theoretically, but we shall have occasion to return to their data in the present experiment. Performances on the 3-dimensional problems are to be described by Eqs. (25), (26), and (27), (28) for the Multiple-Look and Single-Link Models, respectively. The 3 relevant dimensions in Problems AAA are, of course, Color, Form, and Compound. Parameters for the individual dimensions are transferred from Experiments One and Two and used in the above equations to effect the predictions shown in Table XIX. The multiple-look predictions agree more closely with the TABLE XIX OBSERVED AND PREDICTED VALUES OF Pa AND Pa FOR THE THREE-DIMENSIONAL FIVE PROBLEMS OF EXPERIMENT

Predicted

Trial 2 Trial 3

Observed (Retardates)

Observed (Normals)

.80 .84

.90

.86

Multiple-look

Single-link

‘83 .92

.94 .99

data than the single-link forecasts which rather badly overestimate performance levels for both groups. The Multiple-Look Model also overesti-

367

Betty 1. Hotlse and David Zeaman mates the third trial performance of the retardates, but it will be shown presently that this particular group of retardates is weak in color and shouId have a lower c parameter value. B. Colaflict Trials. On the Half-reversal (second) Trials of Problems AA’A and AA’A’, cues of 2 dimensions relevant on the first trial are thrown into conflict on the second. To treat this experimental operation theoretically, we assume for the Multiple-Look Model that if the child sees only the 2 conflicting dimensions on Trial 2, he must guess at which is correct. It can be shown then that second-trial conflict performance should be given by

Pz =

,562

- .sf” -l-.5

(29)

when the color component is rewarded (Problem AA’A and AA’A’ with color), and by Pz = .5f“ - .5c2 .5 (30)

+

when the form component is rewarded on the conflict trial. The Compounds present on Trial 1 are no longer available on Trial 2 and so play no theoretical role. In the Single-Link Model, the assumption is made that a conflict trial leads to chance performance if both of the conflicting sets of cues have been previously conditioned. Given the other assumptions of this model, we write Pz= c + .5(1 - c - F ) (31) when the color component is rewarded, and Pz=F+.5(1-

C-F)

(32)

when the form component is rewarded. Borrowing the parameters from earlier experiments as usual leads to the theoretical entries of Table XX.

TABLE XX OBSERVED AND PRKDICTED PERFORMANCES ON TRIAL2 FIVE TRIALSOF EXPERIMENT

OF

CONFLICT

Predicted

Color rewarded Form rewarded

Observed (Retardates)

Observed (Normals)

Multiple-look

.42

.47 .61

.48

.48

.52

.52

.63

Single-link

The 2 models make the same predictions, both of which underestimate the color-form differences, particularly for the retardates.

368

Discrimination Learning of Retardates C . A Slight Adjustment. W e suspect that the reason for the underestimation in Table XX lies simply in a sampling error, that this particular group tends to be weaker in color than the population of which it is a sample. This inference comes not only from the present data, but from the performance on the Standard Color Problem as well: P, for this group in the Standard Color Problem was .66; the mean of the remaining population was .75. If we reduce the c parameter to .23 and C to .lo to accommodate the conflict data of Table XX, leaving the other parameters undisturbed, then agreement between models and data for the 2-dimensional problem is also improved, and as a bonus, the 3-dimensional predictions now become respectable for the Multiple-Look Model. These accomplishments are shown in Table XXI.

TABLE XXI PREDICTED AND OBSERVED VALUESOF PERFORMANCES ON CONFLICT TRIALS,STANDARD COLORPROBLEMS, AND THREE-DIMENSIONAL PROBLEMS FOR RETARDED CHILDREN. (An adjusted value of the color parameter has been used.) Observed

Multiple-look

Single-link

Conflict trials Color rewarded Form rewarded

.42

.40 .60

.40 .60

Standard Color Problem Trial 2 Trial 3

.66 .80

.68 .77

.71 .83

.80 .84

.78 .86

.86

3-Dimensional Problem Trial 2 Trial 3

.63

.96

Since the form and compound parameters have not been changed, the agreement of theory and data previously shown for the Standard Form Problem is left intact by this adjustment. The Multiple-Look Model now gives a fair description of this array of data, but the Single-Link Model still tends to overshoot performances on the 2- and 3-dimensional problems. The third trials of the conflict problems contain strong evidence of retention loss, and so will not be treated theoretically at the present time. D. Other Possible Adjustments. In fairness to the Single-Link Model, it must be admitted that its predictions could be brought into closer agreement with some parameter juggling. Most of its estimates tend to be on the high side. If the 3 parameters of this model were reduced, these

369

Betty 1.House and David Zeaman overestimations would be reduced at the cost of underestimating the data of the 1-dimensional problems originally used to fix the parameters. Sharing the error in this way would minimize the total error by a Least Squares Criterion. W e cannot conclude from the tests we have run that one model fits the data better than another until many parameter combinations have been examined. This is a tedious procedure, and one not followed here. W e have instead tried the simple and perhaps overly stringent technique of borrowing the parameters of the simpler problems to be applied to the more complex, The results favored the Multiple-Look Model, but no undue importance should be assigned this. If Attention Theory is going to prove useful, it is not only because it can quantitatively describe much of the data of these Miniature Experiments but because it also predicts such qualitative phenomena as Intra- and Extra-Dimensional Shift Effects (Shepp & Eimas, 1963; House & Zeaman, 1962), and Reversal Midplateaus (Zeaman & House, 1963), not as yet deducible from Single-Link Theory.

IV. General Summary A. METHODOLOGY The %trial methodology of these studies borrows from techniques developed by Harlow (Learning-Set Experiments) and Estes (Miniature Experiments). Small numbers of subjects are run for just 3 trials on each of a large number of homogeneous discrimination problems. Relatively fast learning and absence of learning set make feasible this highly efficient and flexible experimental design. The resulting data reflect influences of a number of theoretically important empirical variables, and lend themselves readily to mathematical treatment by probabilistic models.

B. FINDINGS I n the 2-choice object discrimination learning of well-practiced retarded children, studied with ?-trial methodology, it was found that: (1) Color and form componeizts are used in the solution of problems having these dimensions available, form slightly but consistently more than color. ( 2 ) Compounds of color and form are also used, and about as much as components. The positive compound cue acquires stronger associative connections with discriminative responses than the negative compound cue.

370

Discrimination Learning of Retardates (3) Speed of learning +trial problems increases as MA increases from 3 to 8 years. (4) Children with normal or superior IQ learn faster than retarded children matched for MA. ( 5 ) Children with higher MAS use compounds more, and also show a stronger reliance on the form component than the color component when the two conflict. Brighter chiIdren learn more about compounds and about components than those of lower MA. ( 6 ) Tendencies to adopt strategies based on the left-right position of the stimuli decrease with growth in MA. ( 7 ) Short-term retention loss of both component and compound information appears under some conditions of delayed testing, variability in irrelevant dimensions, and cue conflict. (8) Variability in an irrelevant color or form dimension does not appreciably retard discrimination learning. ( 9 ) Increasing the number of redundant relevant dimensions enhances the speed of discrimination learning, reliably so for an increase from 1 to 2 dimensions, not reliably for an increase from 2 to 3.

C. THEORETICAL IMPLICATIONS:QUALITATIVE 1. Compounding and Additivity of Cues The fact that color and form dimensions, when combined, give rise to a third, or compound, dimension implies that color and form are not additive cues in the sense that Restle (1959) and Trabasso (1960) use that term. This being the case, theories which postulate additivity are inapplicable to the visual discrimination Iearning of retarded children under the conditions of these experiments. No implication is intended here that cues will never be found for retardates which fit the additivity assumption.

Variability in Irrelevant Dimensions Restle’s theory assumes that only variable stimulus dimensions play a role in discrimination learning, and that variable irrelevant dimensions impede problem solution. Two aspects of the present data make these assumptions doubtful for retardate discrimination learning: (a) constant, and therefore, irrelevant, dimensions can form compounds with variable dimensions and gain associative strength in the way, and (b) learning is not slower with a variable irrelevant dimension than a constant irrelevant dimension, when allowance is made for the greater number of relevant dimensions (including compounds) under the constant condition. 2.

371

Betty [. House and David Zearnan 3. Developmental Theory Theorists (e.g., Werner, 1948) who have regarded differential use of compound and component solutions as an index or correlate of developmental level will find no comfort in our data.

4. Subject Variables Theories of intelligence have related learning ability to either MA or IQ. The present results favor the interpretation, previously offered (House & Zeaman, IgGO), that both MA and IQ independently control discriminative learning. W e assume the mechanism of this control to lie in the area of attention, rather than instrumental learning. Our quantitative theoretical analyses allow for individual differences in probabilities of attending to relevant dimensions but not speed of instrumental learning, which is assumed to be all-or-nothing.

D. THEORETICAL IMPLICATIONS : QUANTITATIVE Data of Miniature Experiments have provided tests of 3 mathematical models, a Single-Link Model and 2 submodels of an attention theory: the One-Look and Multiple-Look Models. All 3 systems share the common assumption of all-or-nothing instrumental learning, but Attention Theory differs from Single-Link Theory in postulating not one, but a chain of 2 discriminative responses-attending to the relevant stimulus dimension, and then selecting the positive cue of that dimension. Probabilities of paying attention to the various stimulus dimensions are assumed to be fixed over the three trials of each problem, presumably because of the partial, random schedule of reinforcement of these responses over the course of each experiment. The One-Look Model restricted the child’s attention to a single stimulus dimension at the moment of choice. Brought to the data of these Miniature Experiments, the One-Look Model met an early death, and was replaced with a Multiple-Look Model, which put no restrictions on the number of dimensions seen on a trial, but was otherwise identical in its assumptions to the One-Look Model. The Single-Link Model postulated fixed probabilities that the cues of a dimension would be conditioned on any trial. Once conditioned they were assumed to stay conditioned. The experimental fact of compounding is represented theoretically in all the models by treating the compound dimension simply as another dimension, coordinate with the component dimensions. Theoretical evaluation of the importance of compounds in determining discriminative behavior is given by the weights, empirically determined, of the compound parameters, K and R .

3 72

Discrimination Learning of Retardates Performances on Trial 2 of 1-dimensional problems were used to estimate the three parameters of the Multiple-Look and Single-Link Models. With parameters fixed, the models generated predictions for the Standard Color and Standard Form Problems (2-dimensional problems), 1-component-dimension-plus-1-compound-cueproblems, 3-dimensional problems, conflict trials, and Trial 3 of the 1-dimensional problems. Data of the second trials of all these problems were described with reasonable accuracy by the Multiple-Look Model, as well as the third trial of the 2- and 3-dimensional problems; but an unpredicted retention loss appeared on Trial 3 of several experiments with delayed testing of components or compounds, variable irrelevant dimensions, and conflict arrangements. The Single-Link Model tended more to overestimate the observed proportions, using our method of fixing parameters, but these errors could probably have been reduced by more flexible methods of parameter estimation. REFERENCES Bijou, S. W. & Baer, D. M. The laboratory-experimental study of child behavior. In P. H. Mussen (Ed.), Handbook of research methods in child development. New York: Wiley, 1960. Pp. 140-200. Bourne, L. E., Jr. & Haygood, R. C. The roles of stimulus redundancy in concept formation. J . exp. Psychol., 1959, 58, 232-238. Bourne, L. E., Jr. & Restle, F. Mathematical theory of concept identification. Psychol. Rev., 1959., 66, 278-296. Bower, G. H . Application of a model to paired-associate learning. Psychometrika, 1961a, 26, 255-280. Bower, G. H. Application of the all-or-none conditioning model to the learning of compound responses. Tech. report No. 37, 1961b. Institute for Mathematical Studies in the Social Sciences, Applied Mathematics and Statistics Lab., Stanford Univer. Stanford, California. Broadbent, D. E. Perception and communication. New York: Pergamon, 1958. Eimas, P. D. Stimulus patterning in simultaneous discrimination learning of retardates. 1963 (in preparation). Eimas, P. D. & Shepp, B. E. Retardate discrimination learning following differential conditioning of the choice-point stimuli. Paper read at Eastern Psychol. Ass., New York, April, 1963. Estes, W. K. The problem of inference from curves based on group data. Psychol. Bull., 1956, 53, 134-140. Estes, W. K. Components and pattern models with Markovian interpretations. In R. R. Bush & W. K. Estes (Eds.), Studies in mathematical learning theory. Stanford, California: Stanford Univer. Press, 1959. Pp. 9-52. Estes, W. K. Learning theory and the new ”mental chemistry.” Psychol. Rev., 1960, 67, 207-223. Estes, W. K. New developinents in statistical behavior theory: differential tests of axioms for associative learning. Psychornetrika, 1961, 26, 73-84. Harlow, H. F. Learning set and error factor theory. In S. Koch (Ed), Psychology: A study of a science. Vol. 2. New York: McGraw-Hill, 1959. Pp. 492-537. Herman, P. & House, B. J. Accuracy of reporting tachistoscopic stimuli as a function

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Betty J. House and David Zeaman of dimension and order of recall. In Learning and transfer in mental defectives. Prog. Rep. No. 2, NIMH, USPHS, Res. Grant M-1099 to Univer. of Connecticut, 1960, Pp. 99-104. House, B. J. & Zeaman, D. Reward and nonreward in the discrimination learning of imbeciles. J. comp. physiol. Psycho/., 1958, 51, 614-618. House, B. J. & Zeaman, D. Visual discrimination learning and intelligence in defectives of low mental age. Amer. J . menf. Defic., 1960, 65, 51-58. House, B. J. & Zeaman, D. Reversal and nonreversal shifts in discrimination learning of retardates. J. exp. Psychol., 1962, 63, 444-451. House, B. J. & Zeaman, D. Learning sets from minimum stimuli in retardates. J. comp. physiol. Psychol., 1963, 56, 735-739. Kendler, T. S., Kendler, H. H., & Learned, B. Mediated responses to size and brightness as a function of age. Amer. J. Psychol., 1962, 75, 571-586. Klinman, C. Color and form component learning in retardates. 1963 (in preparation). Lawrence, D. H. & LaBerge, D. L. Relationship between recognition accuracy and order of reporting stimulus dimensions. J. exp. Psychol., 1956, 51, 12-18. Levine, M. A model of hypothesis behavior in discrimination learning set. Psychol. Rev., 1959, 66, 353-366. North, A. J. & Jeeves, M. Interrelationships of successive and simultaneous discrimination. J. exp. Psychol., 1956, 51, 54-58. Restle, F. A theory of discrimination learning. Psychol. Rev., 1955, 62, 11-20, Restle, F. Additivity of cues and transfer in discrimination of consonant clusters. J . exp. Prychol., 1959, 57, 9-14. Restle, F. The selection of strategies in cue learning. Psychol. Rev., 1962, 69,329-343. Shepp, B. E. & Eimas, P. D. Intra- and extra-dimensional shifts in the rat. J. comp. physiol. Psychol., 1963 (in press). Spence, K. Behavior theory and learning. Englewood Cliffs, New Jersey: Prentice-Hall, 1960. Teas, D. C. & Bitterman, M. E. Perceptual organization in the rat. Psychol. Rev., 1952, 59, 130-140. Trabasso, T. R. Additivity of cues indiscrimination learning of letter patterns. J. exp. Psychol., 1960, 60, 83-88. Warren, J. M. Additivity of cues in visual pattern discriminations by monkeys. J. comp. physiol. Psychol., 1953, 46, 484-486. Werner, H. Comparative psychology of mental development. (rev. ed.) New York: International Universities Press, 1948. Wodinsky, J., Varley, M. A. & Bitterman, M. E. Situational determinants of the relative difficulty of simultaneous and successive discrimination. J. comp. pbysiol. Psychol., 1954, 47, 337-340. Wyckoff, L. B., Jr. The role of observing responses in discrimination learning, Part I. Psychol. Rev., 1952, 59, 431-442. Wyckoff, L. B., Jr. A mathematical model and an electronic model for learning. Psychol. Rev., 1954, 61, 89-97. Zeaman, D. & House, B. J. Approach and avoidance in the discrimination learning of retardates. Child Develpm., 1962, 33, 355-372. Zearnan, D. & House, B. J. An attention theory of retardate discrimination learning. In N. R. Ellis (Ed.), Handbook of mental deficiency. New York: McGraw-Hill, 1963. Zeaman, D., House, B. J. & Orlando, R. Use of special training conditions in visual discrimination learning with imbeciles. Amer. J. ment. Defic., 1958, 63, 453-459.

3 74

Author Index Numbers in italics show the page on which the complete reference is listed.

A Acker, M.,28, 30 Adams, J. A., 127, 141 Aldrich, C. A., 172, 191 Akishige, Y., 270, 278, 279, 280, 310 Anderson, N. A., 89, 107 Antonova, T. G., 169, 192 Attneave, F., 9, 10, 16, 29 Ayres, J. G., 80, 99, 109

B Babkin, P. S., 164, 191 Baer, D. M., 201, 211, 213, 215, 218, 220, 221, 225, 230, 325, 373 Bakwin, H., 71, 72, 89, 92, 107 Bakwin, R. M., 71, 72, 89, 92, 107 Baldwin, B. T., 79, 89, 92, 107 Bandura, A., 211, 215, 221, 230 Banks, E. M.,152, 192 Barnhart, C. L., 55, 65 Barnett, C. D., 139, 142 Bartoshuk, A. K., 170, 191 Bastian, J., 37, 65 Baxter, J. H., 87, 88, 102, 107 Bayley, N., 73, 93, 107 Beach, F. A., 201, 230 Bean, R. B., 88, 107 Beckham, A. S., 84, 101, 107 Behar, I., 132, 142 Bensberg, G. J. Jr., 117, 142 Berko, J., 38, 56, 65 Berkowitz, H., 37, 65 Berkson, J., 71, 89, 111 Berlyne, D. E., 4, 5, 14, 16, 19, 28, 29 Beyrl, F., 274, 275, 281, 285, 289, 291, 292, 304, 310 Bialer, I., 39, 65 Bijou, S. W., 201, 211, 230, 325, 373

Binning, G., 70, 84, 100, 107 Birch, D., 253, 264 Birkhoff, G. D., 10, 29 Bissett, L., 101, 102, 107 Bitterman, M. E., 245, 264, 322, 374 Blake, F. G., 106, 110 Blau, L. R., 203, 230 BIau, T. H., 203, 230 Blauvelt, H. H., 164, 191 Blazek, N. C., 129, 144 Blesh, T. E., 70, 106, 107 Blum, A,, 116, 132,144 Boas, F., 70, 76, 78, 79, 80, 82, 83, 84, 96, 97, 98, 99, 100, 101, 102, 106, 107, 108 Boring, E. G., 266, 269, 311 Bourne, L. E., Jr., 339, 344, 346, 373 Bousfield, W. A., 37, 61, 65 Bowditch, H. P., 73, 75, 76, 78, 79, 80, 82, 83, 84, 86, 93, 94, 96, 97, 98, 99, 100, 101, 102,108 Bower, G. H., 357, 360, 373 Bowes, A. E., 125, 142 Bowles, G. T., 70, 106, 108 Bowman, R. E., 136, 142 Boyd, W. C., 106, I08 Brackbill, Y., 165, 169, 171, 177, 191 Brault, H., 283, 310 Braun, H. W., 122, 124, 125, 129, 145 Breckenridge, M. E., 107, 108 Bregman, E., 172, 191 Bridger, W. H., 170, 191 Britten, R. H., 75, 84, 94, 100, 101, 102, 113 Broadbent, D. E., 335, 373 Bronshtein, A. I., 169, 192 Brown, A. P., 75, 84, 94, 100, 101, 108 Brown, A. W., 71, 89, 111 Brown, E. W., 89, 107 Brown, J. S.,2, 29, 140, 142

3 75

Author Index Brown, M. A,, 75, 84, 94, 100, 108 Brown, R., 38, 56, 65 Brown, W. L., 138, 144 Brunswik, E., 272, 310 Budin, W. A., 52, 65 Bugelski, B. R., 138, 142 Burns, R., 216, 217, 230 Burzlaff, W., 278, 280, 310 Bussey, T., 283, 311 C

Caldwell, B. M., 168, 192 Caldwell, D. F., 153, 192 Callantine, M. F., 128, 142 Calvin, A. D., 140, 142 Cantor, G. N., 19, 21, 29, 117, 139, 142 Cantor, J. H., 19, 21, 29 Cardozo, W. W., 92, 113 Carey, J. E., 39, 65 Carkon, V. R., 267, 272, 283, 303, 310 Carroll, J. B., 54, 55, 65 Carter, H. D., 36, 65 Carton, A. S., 54, 55, 65 Casey, A., 267, 288, 310 Castaneda, A., 40, 58, 65, 117, 144 Cates, H. A., 89, 108 Chalmers, E. L., 268, 269, 270, 310 Chenoweth, L. B., 70, 107, 108 Chesire, L. E., 73, 114 Chinetti, P., 283, 311 Chodack, M., 281, 285, 310 Clancy, J. J., 140, 142 Clark, B. G., 71, 72, 89, 92, 113 Clark, G., 93, 108 Clark, T., 75, 84, 94, 100, 101, 108 Clifford, L. T., 140, 142 Cofer, C. N., 37, 65 Cohen, D. J., 201, 230 Cohen, W., 281, 285, 310 Cole, L., 106, 108 Collins, S. D., 75, 78, 84, 94, 97, 100, 101, 108, 112 Cone, T.E., Jr., 70, 106, 108 Cook, T. W., 129, 142 Cooley, J. A., 13, 30, 188, 194 Cooley, T. B., 72, 112 Cordeiro, F. J. B., 84, 86, 101, 102, 108 Cornwell, A. C., 152, 192, 194 Cramer, P., 37, 61

3 76

Crawford, R. P., 89, 113 Cronbach, L. J., 309, 310 Crowell, D. H., 157, 192, 201, 230 Crum, F. S., 72, 73, 92, 93, 108 Crump, E. P., 89, 108

D Damon, A,, 88, 104, 113 Davenport, C. B., 106, 108 Davidson, K. S., 140, 144 Davis, F. C., 73, 93, 107 Dearborn, W. F., SO, 81, 99, 100, 108 Deegan, W., 70, 87, 108 Deese, J., 37, 65 Degutis, E. W., 79, 84, 98, 100, 108 deHaan, H. J., 119, 142 de Labry, J., 211, 215, 231 DeLilly, M. R., 92, 113 DeLucia, C. A., 157, 193, 201, 231 Dember, W. N., 12, 18, 29, 29 Denisova, M. P., 164, 192 Denis-Prinzhorn, M., 267, 276, 287, 288, 293, 304, 310 Dennis, W., 202, 230 Densen, P., 80, 99, 113 Diehl, H. S., 87, 103, 108 Dietze, D., 39, 65 Disher, D. R., 169, 192 Ditrichs, R., 19, 29 Dodge, C. T. J., 92, 108 Draguns, J., 52, 65 Dukes, W. F., 292, 310 Duncan, C. P., 118, 128, 129, 140, 142, 245, 264

E Earl, R. W., 12, 18, 29, 29 Easler, C.A., 152, 192 Eastman, F. C., 33, 53, 65 Edgren, R. D., 280, 310 Eimas, P. D., 320, 335, 370, 373, 374 Eisman, Bernice S., 39, 61 Elbel, E. R., 70, 87, 103, 109 Elkonin, D. B., 164, 171, 192 Ellis, N. R,, 28, 30, 122, 125, 126, 130, 131. 132, 133, 134, 142

Atlibor Index Elonen, A. S., 35, 65 Engen, T., 170, 192 Eppright, E. S., 84, 100, 101, 109 Epstein, W., 267, 288, 310 Eriksen, C. W., 138, 142 Ervin, S. M., 38, 65 Esterson, J., 61, 65 Estes, W. K., 315, 317, 318, 357, 360, 3 73

F Fabel, L. S., 40, 58, 65 Fantz, R. L., 7, 8, 13, 30 Farber, 1. E., 140, 142 Feallock, S. M., 281, 282, 283, 290, 305, 311 Feinburg, L. K., 52, 65 Ferguson, A. D., 71, 72, 89, 113 Figurin, N. L., 164, 192 Fiske, D. W., 24, 28, 30 Flavell, J. H., 52, 65 Flynn, M. A., 71, 92, 114 Foard, E. D., 70, 87, 88, 103, 109 Foman, S. J., 72, 92, 93, 94, 110 Forbes, H. B., 169, 192 Forbes, H. S., 169, I92 Francisco, E. W., 120, 144 Freeman, R. G., Jr., 71, 89, 109 Friedlander, B. Z., 184, 192 Furst, E., 32, 66 Fuller, J. B., 140, 142 Fuller, J. L., 152, 192

G Garn, S. M., 106, 109 Gebhart, J. C., 93, 109 Gesell, A., 202, 230 Gewirtz, J. L., 178, 189, 194, 215, Gibson, E. J., 270, 271, 276, 284, 286, 310, 311 Gibson, J. J., 267, 268, 270, 271, 285, 286, 292, 296, 310, 311 Giddan, N. S., 138, 142 Gihon, A. L., 84, 86, 87, 101, 102, 109 Gilbert, T. F., 200, 230 Gilinsky, A. S., 267, 268, 271, 281, 291, 303, 305, 311

230 285, 280,

103,

289,

Girardeau, F. L., 28, 30, 123, 125, 126, 130, 131, 132, 133, 134, 140, 142 Girshick M. A,, 75, 76, 78, 79, 82, 83, 84, 86, 94, 97, 98, 100, 102, 112 Gittings, J. C., 89, 109 Glaser, F., 283, 311 Gleser, G. C., 70, 114 Godin, P., 106, 109 Goett, T., 33, 66 Goldiamond, I., 204, 231 Golubeva, E. L., 153, 192 Goodenough, F. L., 36, 41, 66 Goodwin, J. C., 89, 108 Goss, A. E., 39, 65, 141, 142 Gould, B. A., 87, 88, 102, 103, 109 Graham, F. K., 168, 192 Gray, H., 70, 80, 99, 106, 109 Greenberg, R., 128, 142 Greenwood, J. M., 78, 80, 84, 86, 97, 99, 100, 101, 102, 109 Greulich, W. W., 80, 99, I09 Griffith, B. C., 139, 143 Griffith, J. P. C., 89, 109 Gruber, H. E. ,267, 269, 303, 312 Grunzke, M. E., 165, 192 Gunther, M., 168, 192

H Hall, W. S., 80, 99, 109 Hamil, B. M., 72, 112 Harlow, H. F., 116, 118, 119, 120, 123, 124, 125, 129, 130, 131, 133, 134, 135, 138, 143, 144, 153, 192, 193, 318, 320, 373 Harrington, T. F., 70, 109 Harrison, J. C. E., 79, 84, 98, 101, 109 Harter, Susan, 119, 120, 121, 124, 125, 143 Hartman, T., 286, 311 Harway, N. I., 289, 290, 291, 311 Hastings, W. W., 75, 78, 84, 87, 109 Hastorf, A. H., 269, 311 Hathaway, M. L., 70, 87, 88, 103, 109 Hatt, E., 73, 114 Hayes, C., 121, 122, 125, 143 Hayes, K. J., 121, 122, 124, 125, 137, 143 Haygood, R. C., 344, 373 Herman, P., 334, 373

377

Author lndex Hermelin, B., 141, 144 Hershkowitz, A., 281, 285, 310 Herskovits, M. J., 75, 84, 86, 100, 101, 102, 209 Hiatt, H. H., 71, 72, 89, 92, 113 Hicks, L. H., 138, 143 Higgons, R. A., 72, 73, 92, 93, 112 Hilgard, J. R., 202, 230 Hinde, R. A., 169, 171, 192 Hitchcock, E., 87, 103, 109 Hoats, D. L., 13, 15, 25, 28, 29, 30 Hodgden, L., 215, 231 Holland, A., 204, 230 Holland, J. G., 204, 205, 230, 231 Hollingsworth, L. S., 71, 111 Holt, B. G., 15, 26, 28, 30 Holt, L. E., 71, 72, 74, 89, 92, 93, 107, 109 Holway, A. H., 266, 269, 311 Hooton, E. A., 106, 107, 109 Hopkins, J. W., 79, 109 Horan, E. M., 35, 53, 66 Horn, E. A., 36, 66 Horon, C. P., 89, 108 House, B. J., 28, 30, 120, 130, 131, 132, 134, 136, 139, 143, 145, 314, 316, 319, 328, 329, 334, 347, 355, 362, 370, 372, 373, 374 Hovland, C. I., 127, 144 Hoyt, J. M., 262, 263, 264 Hrdlicka, A., 106, 109 Hull, C. L., 234, 235, 236, 241, 264 Hulse, F. S., 106, 110 Hulvey, C. N., 75, 84, 113 Hundley, J. M., 75, 94, 110 Hunt, E. E., Jr., 70, 106, 110 Hunt, E. P., 75, 76, 78, 79, 82, 83, 84, 86, 94, 97, 98, 100, 101, 102, 112 Hunt, J. McV., 2, 30 Hunter, W. S., 169, 194 Huston, A. C., 215, 230

I Inhelder, B., 282, 311 Irion, A. L., 117, 143, 150, 193 Irving, R. N., Jr., 79, 110 Irwin, 0. C., 162, 192 Ittelson, W. H., 271, 307, 311

3 78

J Jackson, C. M., 70, 110 Jackson, R. L., 71, 92, 114 Jarrett, R. F., 37, 66 Jarvik, M. E., 116, 143 Jeans, P. C.,106, 110 Jeeves, M., 322, 374 Jeffrey, W. E., 203, 231 Jenkin, N., 281, 282, 283, 290, 305,311 Jenkin, J. J., 37, 40, 41, 50, 51, 52, 63, 66, 67 Jenkins, M. E., 89, 113 Johnson, B., 258, 264 Jonckheere, A. R., 259,264 Jones, H. E., 169, 172, 192

R Kamenetskaya, N. H., 169, 192 Kantrow, R. W., 173, 192 Karlan, S. C., 70, 88, 110 Karpinos, B. D., 85, 86, 87, 88, 102, 103, 104, 110 Kasatkin, N. I., 157, 164, 173, 174, 175, 193 Kasius, R. V., 71, 72, 89, 92, 110 Kass, N., 132, 143 Kaufman, M. E., 116, 122, 124, 133, 134, 143 Kaye, H., 165, 170, 192, 193 Kelly, H. J., 92, 110 Kemble, J. D., 117, 144 Kendler, H. H., 39, 6G, 139, 143, 322, 354, 374 Kendler, T. S., 39, 66, 139, 143, 322, 354, 374 Kennedy, R., 72, 73, 89, 92, 93, 112 Kennedy,R. L. J., 71, 89, 111 Kent, G. H., 33, 66 Kessen, M. L., 133, 143 Kessen, W., 133, 143, 211, 231 Kessler, A. D., 71, 72, 89, 92, 110, 113 Keyfitz, N., 75, 76, 78, 82, 83, 84, 94, 97, 100, 101, 110 Khokhitva, 175, 193 Kimble, J. P., Jr., 37, 67 Kjeldergaard, P. M., 54, 55, 65 Klimpfinger, S., 283, 311 Klinrnan, C., 332, 374

Author Index Knott, V. B., 72, 78, 79, 83, 84, 92, 93, 94, 96, 97, 98, 101, 110 111 Koch, M. B., 119, 120, 122, 124, 143 Krechevsky, I., 131, 138, 143 Kreindler, A., 172, I93 Krogman, W. M., 75, 78, 79, 80, 84, 93> 94, 97, 98, 99, 100, 110 Kuenne, M. K., 139, 143 Kuhlman, C., 211, 231 Kurtz, K. H., 117, 140, 143 L

LaBerge, D. L., 334, 374 Lambercier, M., 267, 270, 275, 276, 277, 278, 279, 282, 283, 285, 286, 302, 307, 311, 312 Larder, D., 219, 231 Lashley, K. S., 261, 264 Laslett, H. R., 101, 102, 107 Lawrence, D. H., 245, 264, 334, 374 Learned, B., 322, 354, 374 Lehner, G. F. J., 169, 193 Leibowitz, H., 281, 282, 283, 286, 289, 291, 305, 306,311,312 Leventhal, A. S., 170, 193 Levikova, A. M., 173, 174, 193 Levin, G. R., 165, 193, 215, 231 Levine, M., 135, 136, 138, 143, 320, 352, 353, 374 Levinson, B., 116, 119, 121, 122, 123, 125, 130, 132, 133, 134, 136, 137, 138, 139, 141, 143 Levy, N., 159, 193 Lighthall, F. F., 140, 144 Lindquist, E. F., 17, 30 Ling, B. C., 177, 193 Lipsitt, L. P., 117, 144, 157, 159, 165, 170, 178, 187, 192, 193, 194, 201, 231, 245, 264 Lloyd-Jones, O., 70, 75, 76, 78, 81, 82, 83, 84, 86, 94, 100, 101, 102, 106, 110

Locke, N. M., 282, 311 Loeffler, N., 283, 311 Loess, H. B., 245, 264 Loos, F. M., 129, 145 Lorge, I., 40, 68 Lovaas, 0.I., 217, 231 Lowell, F., 32, 34, 48, 68

Luppova, V. A,, 169, 192 Luria, A. R., 139, 144 Lyon, R. A., 89, 107

M McBee, G., 120, 14s McCarthy, D., 43, 66 MacCaslin, E. F., 245, 249, 264 McConnell, D. G., 120, 144 McConnell, J. V., 245, 264 McCullers, J. C., 40, 58, 66 MacDonald, A., 75, 78, 79, 80, 84, 86, 94, 97, 98, 99, 100, 101, 102, 110 McElivee, E. W., 35, 66 McFadden, J. H., 35, 66 McFarland, R. A., 88, 104, 113 McGehee, N. E., 37, 66 McGehee, W., 36, 43, 66 McGeoch, J. A., 150, 193 McGraw, M. B., 202, 231 McGuire, P., 283, 311 MacKinnon, D. C., 70, 110 McLendon, J. B., Jr., 80, 84, 99, 101, 111 McReynolds, P., 28, 30 Maq, I. G., 72, 112 Maddi, S. R., 24, 28, 30 Mantel, N., 75, 94, 110 Maresh, M. M., 86, 111 Marinesco, G., 172, 193 Marquis, D. P., 163, 164, 193 Martin, J. G., 37, 66 Martin, W. E., 106, 111, 116, 132, 144 Marum, K. D., 159, 193 Mason, W. A., 129, 144, 153, 193 Massucco-Costa,A., 287, 311 Masuoka, J., 89, 108 Mataratzo, R. G., 168, 192 Mateer, F., 173, 193 Matheny, W. D., 80, 99, 111 Mathews, J., 204, 230 Maw, E. W., 28, 30 Maw, W. H., 28, 30 May, R. B., 18, 29, 30 Mefferd, R. B., Jr., 37, 67 Mendel, G., 23, 30 Meredith, E. M., 70, 82, 84, 96, 100, 111 Meredith, H. V., 70, 71, 72, 73, 78, 79, 80, 82, 83, 84, 89, 93, 96, 97, 98, 99, 100, 101, 106, 110, 111, 113

A d o r Index Meumann, E., 32, 66 Meyer, D. R., 117, 119, 120, 122, 124, 143, 144 Michelson, N., 70, 72, 86, 87, 89, 92, 111 Mickelsen, O., 75, 94, 110 Miles, C. C., 36, 67 Miles, R. C., 117, 144 Milgram, L., 72, 92, 107 Milgram, N. A., 37, 66 Miller, R. E., 120, 144 Mills, C. A., 106, 111 Mink, W. D., 37, 63, 66 Mirzoyants, N. S., 175, 193 Mitchell, I., 34, 66 Moehlman, A. B., 94, 100, 101, 112 Montague, H., 71, 111 Moon, S. B., 83, 96, 1 1 1 Moore, R., 204, 231 Moran, L. J., 37, 67 Morgan, C. T., 2, 30 Morgan, J. J. B., 154, 171, 193 Morgan, S. S., 154, 171, 193 Morrisett, L., Jr., 127, 144 Mosher, C. D., 106, I l l Mowrer, 0. H., 2, 30 Munn, N. L., 155, 193 Murphy, J. V., 120, 144 Mustard, H. S., 75, 84, 94, 100, 101, 111

N

Osborn, W. J., 61, 67 Otis, M. A., 33, 67 Overall, J. E., 138, 144

P Packer, P. C., 94, 100, 101, 112 Palermo, D. S.,39, 40, 50, 51, 67 Palmer, C. E., 78, 97, 100, 112 Papousek, H., 176, 193, 194 Park, J., 267, 288, 310 Parton, D., 215, 217, 220, 231 Pasamanick, B., 71, 72, 92, 112 Paschal, F. C., 81, 112 Patrick, T. W., 92, 107 Patton, R. A., 122, 124, 125, 129, 145 Peatman, J. G., 72, 73, 92, 93, 112 Peckham, E. G., 169, 194 Peckham, G. W., 73, 75, 78, 79, 84, 86, 94, 97, 98, 100, 101, 102, 112, 169,

194 Peiper, A., 169, 194 Pereboom, A. C., 124, 137, 143 Peterson, J., 157, 192, 201, 230 Peterson, W. M., 116, 122, 124, 133, 134, 143

Pett, L. B., 88, 104, 112 Piaget, J., 168, 194, 270, 272, 276, 277, 278, 282, 283, 284, 285, 306, 307, 311, 312

Newcomer, E. O., 84, 101, I l l Newcomer, M., 104, 106, 111 Norcross, K. J., 39, 67, 117, 144 North, A. J., 322, 374 Norwal, M., 71, 89, 111 Nyessen, D. J. H., 107, 112 0

OBrien, R., 75, 76, 78, 79, 82, 83, 84, 86, 94, 97, 98, 100, 101, 102, 112 OConnor, N., 141, 144 Odom, R., 40, 58, 65 ODonnell, J. P., 126, 141 Ogilvie, G. F., 88, 104, 112 Ohm, V., 276, 284, 286, 310 O'Neil, W. M., 38, 67 Orlando, R., 28, 30, 136, 143, 328, 374

380

Pietila, C., 28, 30 Pirojnikoff, L. A., 140, 145 Piscopo, J., 80, 84, 99, 100, 122 Pishkin, V., 306, 311 Platt, V., 71, 89, 109 Plenderleith, M., 123, 144 Poggiani, C., 152, 194 Polidora, V. J., 120, 144 Polikanina, R. I., 156, 194 Poole, M. W., 72, 112 Porter, W. T., 76, 78, 82, 83, 84, 86, 94, 96, 97, 100, 101, 102, 112 Prechtl, H., 164, 194 Preston, M. I., 80, 99, I12 Price, L. E., 245, 252, 264 Prosser, C. J., 169, 194 Pryer, M . W., 28, 30, 125, 126, 130, 131, 132, 133, 134, 142

Author Index Pyk, W. H., 78, 84, 86, 97, 101, 102, 112

R Rand, W., 106, I 1 0 Randall, A., 71, 72, 89, 92, 110 Randall, F. E., 86, 87, 88, 102, 103, 112 Rapoport M., 72, 73, 89, 92, 93, 112 Ray, W. S., 151, 194 Rayner, R. A,, 172, 191, 202, 231 Razran, G. H. S., 163, 194 Reed, R. B., 86, 102, I12 Reese, H. W., 116, 119, 121, 122, 123, 125, 130, 132, 133, 134, 136, 137, 138, 139, 141, 143, 144 Reinhold, F., 33, 67 Rendle-Short, J., 154, 171, 194 Restle, F., 138, 144, 322, 339, 344. 346, 357, 371, 373, 374 Reynolds, L., 92, 110 Rheingold, H. L., 13, 30, 171, 178, 188, 189, 194 Rhoads, T.F., 72, 73, 89, 92, 93, 112 Riggs, F., 71, 89, I12 Riopelle, A. J., 117, 120, 123, 144 Roberts, K. E., 121, 122, 125, 144 Rosanoff, A. J., 33, 34, 37, 43, 53, 61, 66, 67 Rosanoff, I. R., 33, 34, 37, 43, 66, 67 Rose, H. E., 92, 113 Rosenblith, J. F., 215, 231 Ross, H. W., 178, 189, 194 Rothney, J. W. M., 80, 81, 99, 100, I08 Rouse, R. O., 38, 67 Royster, L. T., 75, 84, 113 Rude, A. E., 72, 75, 92, 94, 113 Ruebush, 8. K . , 140, 144 Rueda-Williamson, R., 92, I13 Rusk, R. R., 32, 33, 67 Russell, W. A., 37, 41, 50, 52, 63, 66, 67 Ryan, D., 89, 108 Ryan, J. J., 37, 67 S Safely, M. A., 157, 192, 201, 230 Saling, G., 33, 67 Sarason, S. B., 140, 144

Sargent, D. A., 106, 113 Scharlock, D. P., 138, 142 Scheibe, K. E., 37, 66 Schuck, J. R., 120, I44 SchuIz, R. W., 37, 58, 66, 68 Schusterman, R. J., 132, 133, 144 Schwartz, L., 75, 84, 94, 100, 101, 102, 113 Scott, R. B., 71, 72, 89, 92, 110, I13 Shaffer, C., 81, 100, 113 Shambaugh, C . G., 36, 67 Shambaugh, 0. L., 36, 67 Sheldon, W. H., 106, 113 Shepard, W. O., 39, 67, 126, 144 Shepp, B. E., 320, 370, 373, 374 Sherman, J. A., 225, 230 Shuttleworth, F. K., 78, 80, 81, 97, 99, 100, 108, 113 Sidwell, V. D., 84, 100, 101, 109 Sidowski, J., 283, 311 Simmons, J. J., 215, 231 Simmons, K., 72, 73, 79, 92, 93, I 1 3 Simmons, M. W., 178, 179, 187, 193, 194 Singer, J. L., 303, 312 Sinha, M. M., 132, 141 Skinner, B. F., 205, 231 Smedley, F. W., 75, 78, 84, 86, 94, 97, 100, 101, 102, 113 Smith, A. DeG., 92, 113 Smith, K . U., 188, 194 Smith, W. M., 188, 194, 268, 270, 312 Smock, C. D., 15, 26, 28, 30 Snyder, M. M., 73, 86, 93, 100, 102, 114 Sonoda, G., 267, 312 Sontag, w. w . , 151, 194 Spears, W. C . , 4, 9, 12, 29, 30 Spelt, D. K., 151, I94 Spence, K. W., 235, 237, 238, 239, 243, 245, 264, 314, 374 Spier, L., 80, 113 Spiker, C. C., 39, 67, 117, 139, 140, 144, 141, 177, 194, 201, 231, 255, 258, 264 Spitz, H. H., 13, 15, 25, 28, 29, 30 Spurgeon, J. H., 80, 99, 113 Stanley, w. C., 13, 30, 152, 171, 188, 194 Steggerda, M., 80, 81, 99, 100, 113 Steigman, M. J., 132, 133, 140, 145 Steinman, W., 225, 231

38 1

Author Index Stendler, C. B., 106, 111 Sternberg, G. M., 88, 103, 113 Stevenson, H. W., 120, 122, 126, 130, 131, 132, 133, 138, 140, 143, 145, 215,

112, 114

Sturzebecker, R. L., 87, 103, 113 Stutsman, R., 73, 114 Sullivan, L. R., 81, 112 Sumner, E. E., 93, 114 Suski, P. M., 80, 99, 114 Swartz, J. D., 122, 126, 131, 132, 145 Sweeny, M. E., 73, 114 Sytova, V. A., 169, 192

T Taber, R. C., 75, 94, 210 Tada, H., 268, 269, 312 Tanner, J. M., 70, 106, 114 Teas, D. C., 322, 374 Terman, L. M., 36, 67 Thompson, H., 202, 230 Thompson, L. R., 75, 84, 94, 100, 102, 113 Thompson, R., 121, 122, 125, 143 Thorndike, E. L., 36, 40, 68, 150, Thorpe, W. H., 171, 194 Thouless, R. H., 266, 272, 283, 312 Thune, L. E., 117, 145 Tizard, J., 129, 145 Todd, T. W., 72, 73, 92, 93, 113 Tompkins, W. T., 71, 72, 89, 92, Townsend, C. W., 89, 114 Trabasso, T. R., 371, 374 Trattner, A., 152, 194 Traxler, A. E., 36, 68 Trotter, M., 70, 114 Tuddenham, R. D.,73, 86, 93, 100,

382

Underwood, B. J., 58, G8, 128, 142

V

231

Stewart, T. D., 106, 113 Stockton-Hough, J., 71, 89, 113 Stokes, J., Jr., 72, 73, 89, 92, 93, 112 Storms, L. H., 37, 67 Stoudt, H. W., 88, 104, 113 Streit, W. K., 106, 113 Strong, P. N., Jr., 129, 145 Stuart, H. C., 72, 73, 86, 92, 93, 102,

114

U

101,

194

110

102,

Valentine, C. W., 177, 194 Vandenberg, V., 253, 264 VarIey, M. A,, 322, 314 Verinis, J. S., 38, 67 Verplanck, W. S.,201, 231 Vickers, V. S., 72, 73, 92, 93, 114 Vincent, E. L., 107, 108 Vurpillot, E., 267, 312

w Waite, R. R., 140, 144 Wallace, R. F., 151, 194 Wallis, R. S., 73, 93, 114 Walters, R. H., 211, 221, 230 Wapner, S., 301, 312 Waring, J. I., 75, 84, 94, 100, 101, 111 Warren, J. M., 128, 132, 142, 145, 320, 347, 374 Waskow, I., 283, 311 Watson, J. B., 172, 195, 202, 231 Way, K. S., 269, 311 Weaver, R. N., 75, 94, 110 Weir, M. W., 130, 138, 145 Weisberg, P., 178, 195 Weisman, S. A., 79, 114 Welsh, G. S., 21, 30 Wells, D., 39, 66, 139, 143 Wenger, M. A., 155, 163, 172, 195 Werboff, J., 153, 192 Werner, H., 301, 312, 322, 354, 372, 374 Wertheimer, M., 169, 195 Westerfeld, R., 71, 92, 114 Wheat, L. B., 36, 43, 68 Whitacre, J., 84, 93, 100, 101, 102, 114 White, B. N., 255, 258, 264 White, R. M., 88, 114 White, R. W., 2, 30 White, S. H., 28, 30 Whitehouse, J. M., 267, 269, 303, 312 Whitmarsh, G. A., 37, 61, 65 Wickens, C., 151, 155, 167, 195 Wickens, D. D., 151, 155, 167, 195

Author Index Wicklund, D. A., 58, 68 Wiehl, D. G., 71, 72, 89, 92, 110 WiIson, C. A,, 73, 114 Wimrner, A., 33, 68 Wintler, J., 32, 68 Wischner, G. J., 119, 122, 124, 125, 126, 129, 142, 145 Wissler, c., 78, 82, 83, 84, 96, 97, 100, 108 Witkin, H. A., 308,312 Wodinsky, J., 322, 374 Wohlwill, J. F., 210, 231, 266, 269, 272 274, 283, 284, 293, 294, 295, 296, 301, 303, 312 Wolff, G., 84, 86, 100, 101, 102, 114 Woodbury, R. M., 72, 73, 91, 92, 93, 114 Woodrow H., 32, 34, 35, 48, 65, 68 Woodworth, R. S., 2, 30 Woolley, H. T., 84, 86, 101, 102, 114

Wreschner, A., 33, 68 Wunderlich, R. A., 120, 144 Wyckoff, L. B., Jr., 355, 374 Wyrnan, Jennie, B., 36, 68

Y Yarczower, M., 37, 65 Young, N. D., 80, 99, 113 2

Zearnan, D., 28, 30, 117, 120, 130, 132, 134, 136, 139, 143, 145, 316, 319, 328, 329, 347, 355, 370, 372, 374 Zeigler, H. P., 281, 289, 291, 312 Ziehen, T., 32, 68 Zigler, E., 132, 145, 211, 212, 215,

131, 314, 362,

231

383

Subject Index A Abstract vs. concrete perception, 322-354 Abstraction, 205-211 Acquired equivalence of cues, 141 Adaptation, 160, 169-171 Adult body size, lee Size of young adult Afferent neural interaction, principle of 234, 235 American Negro, 71-72, 75, 80, 84, 8689, 92, 94, 99-103 Amerindian, see Navajo Amount of secular change, see Secular change Anxiety, 132, 140 Approach and avoidance tendencies, 130, 136-137 Associative vs. motivational concepts, 28 Attention, 117, 117n, 132, 135, 139 Attention theory, discrimination learning, 316315, 355-357, 362-363, 370-372

B Behavior primacy theory, 2 Body weight, children, 92-101 infants, 89, 91-92 young adults, 102-104

C Caucasoid lineage, 71-105 Causes of secular change, 104, 106 Central-motive state, 2 Central-tendency effect, 278f, 280, 300 Childhood stature and weight, 73-85, 92101

Clinical-concentric method, 276 Clothing weight, 93 Collative variables, 3-4, 29 Color preference, 9

384

Color vs. form, discrimination learning, 329-331, 334, 338-339, 343, 363, 365, 366371 Competence motivation, 2 Complexity of the organism, 18 Component Learning, stimulus, 321, 326329, 332-354, 358-363, 365-368, 370, 372 Compound Learning, stimulus, 321-324, 326-339, 350-352, 358-359, 361-362, 366, 370-372 Concept formation, 128 Conditioning, animal, 152-154 classical, 154-167, 171-176 infant, 171-189 neonatal, 154-168 operant, 167-168, 176-190 prenatal, 151 Conflict, 3 conceptual, 1 6 1 7 perceptual, 1 6 1 7 Correlational approach in developmental research, 308 Cortical development, infant, 163-164 Constant stimuli, method, 274 Cues additivity of and/or combination of and/or redundancy of, 346-348, 351, 354, 367, 369, 311 conflict of, 344-345, 347-354, 368-369 Curiosity, 17, 28 as an acquired drive, 28 motivation, 2, 16, 28 perceptual, 14-1 5

D Development, definition of, 198-201 Differential cue error, 133-134, 135

Subject Index Discrimination, conditional, 261ff as successive problem, 262 Discrimination Behavior, 205-21 1 Discrimination problem simultaneous, 239 successive, 243 relative difficulty, 248, 251 Discrimination set, 117, 118, 139 Distance perception in children, age changes in, 286-290 and height, 289 and intelligence, 301f, 305 investigation of, 292-302 practice effects, 288f, 299, 304 relationship to perceived size, 288, 306 sex differences, 300 Drive reduction, 2 Dutch ancestry, 80, 99

E

I Incongruity-dissonance principle, 2 Individual differences, 15, 17, 28 chronological age, 15, 24 in curiosity, 28 intelligence, 1 5 mental age, 1 5 sex, 15, 17, 24 Infancy, 5-13, 20-21, 27-29 perceptual constancy in, 304 Infant activity, 162-163 Infant conditioning, 147-195 Infant stature and weight, 70-72, 89, 9192 Information theory, 10 Inhibition of nonreinforcement, 237, 240 Intelligence, effect of on discrimination learning, 348-352, 367-369, 371-372 Interval of uncertainty, 285f, 300 Italian descent, 80, 99

“Error factor”, 131, 135, 138 Error of the standard, 270, 277f Exploratory behavior, 2, 13

F Feeding adjustments, infants, 163, 165 Field dependence, 308 Form, shape preference, 9, 11-12 Frequency of tall stature, see Tall stature Frustration, 132, 140

G Generational change, see Secular change Geographic region, 70, 76, 78-79, 82-83, 96-98 Grammar, 38-39, 55-57

H

J Japanese ancestry, 80, 99

L Learning, see also Conditioning definition, 150-151 Learning Set, design, 318 Learning set, discrimination, age differences, 121, 131, 132-133, 135, 137, 138-141 effect of amount of training, 118-119, 125-129 effect of contiguity of stimulus and response locus, 120-121 effect of intellectual variables, 122-123 effect of stimulus variables, 119-120, 120-121

Habit, effective, 241 Habituation, 169-17 1 Head-turning response, 176 Height, see Stature “Hypothesis”, 131, 135-138, 141 Hypothesis and/or Strategy, Position, 352353, 371

in children, 115-145 in mental retardates, 120, 122, 123, 125, 129, 130, 131, 132, 133, 136, 139, 140, 141 in monkeys, 116, 118, 119, 120, 123, 125, 129, 130, 131, 132, 134, 135

124, 134, 121, 133,

385

Subject Index shape of acquisition curves, 123-125, 135 theory, 138-141 two-phase acquisition curves, 123-124, 135, 140 Learningto-learn, 117 Longitudinal approach in study of perceptual development, 309 Lower classes, 79, 98

M Magnitude of secular change, 90 Manipulative behavior, 2 Matchingfrom-sample, 121, 205-210 Mathematical models, discrimination learning, 314-315, 355-370, 372 Mediation, 138-141 Mental age, effect of on discrimination learning, 331, 346-354, 371-372 Mexican descent, 81 Miniature Design Experiment, 317-319 Mirror Image Discrimination, 205-211 Mongoloid lineage, Jee Japanese ancestry Motivation theory, 2-3, 28

N Navajo, 81, 100 Negroid lineage, see American Negro 0

Observing behavior, see also Orienting responses, 7-9, 20 Olfactory stimuli, 156157, 170 One-trial learning, 11 6-1 17 Orienting behavior, 2, 5, 13 Orienting responses, 117, 139, 140, 174175 Overconstancy, and binocular cues, 269 and distance, 267, 306 and instructions, 267, 303 and stimulus field, 268, 302f and theories of perception, 270, 305-307 defined, 266

P Paired associates, 40, 58-61, 117 118, 1 2 6 129

386

Pattern vision, 7 Perceptual learning, 271, 305 Performance set, 117, 118, 129, 135 Perspective, perception of, in children, 283-285, 296, 301 Physical vs. psychological measurement, 12, 18, 29 Polygraph, 155, 157-159, 161 Position alternation, 132-133, 135, 136 Position preference, 131-132, 133, 135, 136 Premature infants, 156 Pseudoconditioning, 155 Puppets, Imitation of, 216-226

R Racial groups, 8 6 8 1 , 99-100 Region, see Geographic region Rehearsal, 117 Research strategy in study of perceptual development, 307-310 Response-shift error, 130, 133, 134, 135 Retention, Short Term, 329, 334, 339, 343, 352, 365-367, 369, 371 Rigidity (perceptual), 17 R-R laws, 28

S Secular change, mean stature, 71-75, 78-80, 84-88, 90 mean weight, 89,92-94, 97-103, 105 stature and weight variability, 76, 8283, 96 Serial learning, 117 Set, 138 Size constancy in children, age changes in, 274-278 and distance, 280-282, 290-292 and intelligence, 282f, 305, 306 and perception of perspective, 283-285 and space concepts, 282, 283f, 301, 306 and structure of field, 279f methodological factors, 278 Size of young adult, 64-66, 85-89, 102104 Skin resistance, I61 Social class, see Socioeconomic status Social Reinforcement, 2 1 1-228

Subject Index experimental Studies of, 216, 226-229 methodological problems in, 21 1-216 Socioeconomic status, 56, 60-61, 73, 75, 79-80, 94, 98-99 Special-purpose motives, 2, 28 Stature, children, 73-85 infants, 70-72 young adults, 85-89 Stimulus alternation, 133, 135, 136 Stimulus compounding, 235 cue-position, 253 Stimulus generalization, 234, 235, 237 Stimulus interaction, 236 Stimulus interaction, principle of, 234-264 Stimulus perseveration, 133, 135, 136 Stimulus properties, ambiguity, 16-17 amount of material, number of elements, 4, 13-14, 18, 20 complexity, 3-5, 7, 9-10, 12-21, 2527, 29 contour, 4, 6, 9, 12-13, 16, 20 familiarity, 5 , 16, 21-22, 26-27 heterogeneity, 13-14 incongruity, 3-5, 13-14, 16-17, 25 irregularity, 13-14, 16, 25 novelty, 3-5, 13, 15-17, 21-29 novelty, absolute, 4 novelty, long-term, 4, 27 novelty, relative, 4, 27 novelty, short-term, 4, 27 redundancy, 10, 12 symmetry, 4, 9-13, 15, 25-26 surprisingness, 3-4 turns, number of, 9, 12, 20 uncertainty, 3-5, 27 unknown, 26-27 Stimulus selection behaviors, 2-5, 12, 2021, 28-29 “Strategy”, 136138, 139, 141 Sucking responses, 165-167, 168, 169, 173-174, 203

T Tall statures, 87-88 Texture of stimulus field, 292, 293, 298, 302f Transactiaalist theory of space perception, 271, 307 Transfer, 116, 117, 117n, 118, 127-129, 131, 138 effect of overlearning, 128 Twins, 202

U upper classes, 60-61, 73, 75, 79-80, 94, 98-99

V Verbal Mediation, 40 Veridicality of perception, 270f, 305 Verticality, perception of, in adolescence, 301

W Warm-up, 117 Weight, see Body weight, Clothing weight Welsh figure preference test, 2 1 Word Association, 31-68 Word Association, adult, 37-38 experimental manipulation of, 39, 5761 mentaI retardates, 33-3 5 opposite, 53-55 oral vs. written, 34 pathological, 35 popular, 34, 36, 42-44, 49 sex differences, 43 speed of, 33-36 superordinate, 50-53

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