International Review of Research in Mental Retardation, Volume 10

International Review of RESEARCH IN MENTAL RETARDATION VOLUME 10

Consulting Editors for This Volume John M. Belmont UNIVERSITY OF KANSAS MEDICAL SCHOOL KANSAS CITY, KANSAS

Robert Hogan LONG BEACH, CALIFORNIA

Dennis Runcie UNIVERSITY OF ALABAMA UNIVERSITY, ALABAMA

Paul S. Siege1 UNIVERSITY OF ALABAMA UNIVERSITY, ALABAMA

International Review of RESEARCH IN MENTAL RETARDATION

EDITED BY

NORMAN R. ELLIS DEPARTMENT OF PSYCHOLOGY UNIVERSITY OF ALABAMA UNIVERSITY, ALABAMA

VOLUME 10

1981

ACADEMIC PRESS A Subsidiary of Harcourt Brace Jovanovich, Publishers

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COPYRIGHT @ 1981, BY ACADEMIC PRESS, INC. ALL RIGHTS RESERVED. N O PART O F THIS PUBLICATION MAY BE REPRODUCED OR TRANSMITTED IN ANY FORM OR BY ANY MEANS, ELECTRONIC OR MECHANICAL, INCLUDlNG PHOTOCOPY, RECORDING, OR ANY INFORMATION STORAGE AND RETRIEVAL SYSTEM, WITHOUT PERMISSION IN WRITING FROM THE PUBLISHER.

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LIBRARY OF CONGRESS CATALOG CARDNUMBER:65-28621 ISBN 0-12-366210-9 PRINTED I N THE UNITED STATES O F AMERICA 81828384

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Contents

List of Contriburors Preface

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

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Contents of Previous Volumes

. .. ... .. . . . ., . . . . . .. .. . . .. . . .. .. .. . .. .. ... . .. . ..

vii ix xi

The Visual Scanning and Fixation Behavior of the Retarded Leonard E. Ross and Susan M. Ross 1. Introduction . . . . . . . . . . . ... . . 11. Developmental Changes in Visu 111. Developmental Theory and Scanning . . IV. Fixation and Visual Scanning in V. Concluding Comments . . . . . . . References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

1

5

8 11

24 21

Visual Pattern Detection and Recognition Memory in Children with Profound Mental Retardation Patricia Ann Shepherd and Joseph F. Fagan 111 I

Introduction

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11, Assessment of Visual Pattern Detection and Recognition Memory in the Infant.. . . 111, Assessment of Visual Pattern Detection and Recognition Memory in the Profoundly

Retarded Child . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . IV. Summary and Discussion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . References ...........................................................

31 33

42 54 51

Studies of Mild Mental Retardation and Timed Performance T. Nettlebeck and N. Brewer I. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11. Simple Reaction Time (RT) . . , . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 111. Reaction Time in Memory Scanning . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . IV . Choice Reaction Time (CRT) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . V. An Index of Processing Speed ........................................... V

62 66 12 16 81

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Contents

VI. Cognitive Influences . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . VII. Conclusions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . VIII. Summa. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

88 93 97 98

Motor Function in Down’s Syndrome Feriha Anwar

............................................. 1. ....................... 11. Neuropathology . . . . . . 111. Motor Development , . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ....................... 1v. Perceptual-Motor Functions V. ................. VI. Feedback Systems in Motor Skills . . VII. VI11. Evaluation and Conclusions . . . . . . . .

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

107

108 108 111

115 120 129 131 133

Rumination Nirbhay N. Singh 1.

Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

11. Theories of Etiology ...................................... 111. Intervention Studies . . . . . . . . . . . . . . . . . . . . .

................ IV. Summary and Conclusions . . . . . . . . . . . . . . . References . . . . . . . . ....................................... Index . . . . . . . .

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139 144 148 174 177 183

List of Contributors Numbers in parentheses indicate the pages on which the authors’ contributions begin. Feriha Anwar, MRC Developmental Psychology Unit, Drayton House, Gordon Street, London WClH OAN, England ( 107) N. Brewer, Institute of Special Education, Burwood State College, Melbourne, Australia (61) Joseph F. Fagan 111, Department of Psychology, Case Western Reserve University, Cleveland, Ohio 44106 ( 31) T. Nettlebeck, Department of Psychology, University of Adelaide, Adelaide, South Australia (61) Leonard E . Ross, Department of Psychology, University of Wisconsin,Madison, Wisconsin 53706 (1) Susan M. Ross, Department of Psychology, University of Wisconsin, Madison, Wisconsin 53706 ( 1) Patricia Ann Shepherd, Department of Psychology, Case Western Reserve University, Cleveland, Ohio 44106 (31) Nirbhay N . Singh* , Department of Psychology, Mangere Hospital and Training School, Mungere, Auckland, New Zealand (139)

*Present address: Department of Psychology, Canterbury University, Private Bag, Christchurch I , New Zealand. vii

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Preface

Despite the many obstacles confronting the contemporary researcher in mental retardation/developmental disabilities (MWDD), a fairly steady stream of highquality research and theories continues; the aim of this publication is to publish these scientific and scholarly works. The researcher must keep abreast of developments in MWDD as well as one or several more basic areas such as memory or child development. These critical reviews should lessen the burden. Most topics of interest to the behavioral researcher are reviewed at one time or another. Some of these are exhaustive; others present the systematic work produced in one laboratory. New theories are published. The publication began in 1966 and 10 volumes have appeared in the 15-year period. The work of most behavioral scientists committed to this field has been represented in these volumes. The topics of the 76 chapters have varied widely. A rough sorting of them into categories yields the following: operant (4), classical conditioning (2), psychometric theory (3), personality development (2), neuropsychology ( l ) , cognitive theory (2 l ) , physiological (3), learning (3, motivation ( I ) , psychotherapy ( l ) , reaction time/motor skills (3), social (2), educational (4), speech and hearing (2), problem behaviors (3), psychopharmacology ( l ) , education (4), general (9), vocational rehabilitation ( l ) , and community/institutional issues (3). Only 7 of the chapters represent countries other than the United States. An even more tenuous division yields 26 applied and 50 basic science chapters. We have exercised no editorial bias in the selection of the subject matter, and consequently this policy reflects the productivity in the various problem areas and in the basdapplied categories. Most of the chapters have been solicited, but we have considered and will continue to consider unsolicited materials along with our invited chapters. The present volume includes both applied and basic science materials. The first chapter, by Ross and Ross, is representative of much of the contemporary research in the field. From a general information-processing perspective, the authors provide an interpretative review and analysis of visual scanning in the retarded. Various indices of eye movement are treated as independent variables in an attempt to “explain” retarded behavior in learning and other cognitive tasks. Such an approach is less central, more peripheral, and holds promise for remedial intervention, although the latter is not the primary concern of the authors at this time. ix

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Prefuce

Shepherd and Fagan’s chapter on visual pattern detection and recognition memory, while on a different topic, is similar in several ways to those of Ross and Ross. They too approach their problem from an information-processing perspective. Also, they employ visual behaviors as an index to higher cognitive processes. Shepherd and Fagan exploit “novelty looking” as an index to recognition memory. Children, particularly infants, and lower-functioning mentally retarded persons allowed to view a stimulus, then allowed to view a paired new (novel) stimulus, tend to spend more time viewing the new rather than the old stimulus. Using this approach, Shepherd and Fagan have demonstrated recognition memory processes even in the most profoundly retarded infants. This method and operant conditioning are the only two meaningful approaches to communicating with persons functioning at these extreme levels. Nettlebeck and Brewer, while reviewing the history of experimental psychology, provide fresh experimental data in this area. Their analyses of speed of simple reactions, choice, backward masking, and various attentional phenomena, provide original insights into cognitive functioning. No doubt their analyses will serve to renew interest in this area. Anwar selects research on persons with Down’s syndrome, a fairly homogeneous group, for an analysis of motor defects. His intensive analysis of deficiencies in proprioception shows hypotonia and central processes among the causes of poor motor skills in these subjects. Ultimately such work may suggest remediation in the form of some type of physiological intervention. But such action probably is in the distant future. Singh’s contribution deals with a clinical problem affecting many severely and profoundly retarded persons: rumination, i.e., the “deliberate” regurgitation of ingested food. This problem is prevalent among the institutionalized retarded and is extremely difficult to treat. Singh discusses its causes and its treatment in a scholarly manner. NORMAN R. ELLIS University of Alabama

Contents of Previous Volumes

Autonomic Nervous System Functions and Behavior: A Review of Experimental Studies with Mental Defectives RATHE KARRER

Volume 1 A Functional Analysis of Retarded Development SIDNEY W. BIJOU Classical Conditioning and Discrimination Learning Research with the Mentally Retarded LEONARD E. ROSS

Learning and Transfer of Mediating Responses in Discriminative Learning BRYAN E. SHEPP AND FRANK D. TURNS1

The Structure of Intellect in the Mental Retardate HARVEY F. DINGMAN AND C. EDWARD MEYERS

A Review of Research on Learning Sets and Transfer of Training in Mental Defectives MELVIN E. KAUFMAN AND HERBERT J. PREHM

Research on Personality Structure in the Retardate EDWARD ZIGLER

Programming Perception and Learning for Retarded Children MURRAY SIDMAN AND LAWRENCE T. STODDARD

Experience and the Development of Adaptive Behavior H. CARL HAYWOOD AND JACK T. TAPP

Programmed Instruction Techniques for the Mentally Retarded FRANCES M. GREENE

A Research Program on the Psychological Effects of Brain Lesions in Human Beings RALPH M. REITAN

Some Aspects of the Research on Mental Retardation in Norway WAR ARNLJOT BJORGEN

Long-Term Memory in Mental Retardation JOHN M. BELMONT

Research on Mental Deficiency During the Last Decade in France R . LAFON AND J. CHABANIER

The Behavior of Moderately and Severely Retarded Persons JOSEPH E. SPRADLIN AND FREDERlC L. GIRARDEAU

Psychotherapeutic Procedures with the Retarded MANNY STERNLICHT

Author Index-Subject Index

Author Index-Subject Index

Volume 2

Volume 3

A Theoretical Analysis and Its Application to Training the Mentally Retarded M. RAY DENNY

Incentive Motivation in the Mental Retardate PAUL S. SIEGEL Development of Lateral and Choice-Sequence Preferences IRMA R. GERJUOY AND JOHN J. WINTERS, JR.

The Role of Input Organization in the Learning and Memory of Mental Retardates HERMAN H. SPITZ

xi

xii Studies in the Experimental Development of Left-Right Concepts in Retarded Children Using Fading Techniques SIDNEY W. BIJOU

Contents of Previous Volumes Audiologic Aspects of Mental Retardation LYLE L. LLOYD Author Index-Subject Index

Verbal Learning and Memory Research with Retardates: An Attempt to Assess Developmental Trends L. R. GOULET

Medical-Behavioral Research in Retardation JOHN M. BELMONT

Research and Theory in Short-Term Memory KEITH G. SCOTT AND MARCIA STRONG SCOTT

Recognition Memory: A Research Strategy and a Summary of Initial Findings KEITH G. SCOTT

Reaction Time and Mental Retardation ALFRED A. BAUMEISTER AND GEORGE KELLAS

Operant Procedures with the Retardate: An Overview of Laboratory Research PAUL WEISBERG

Mental Retardation in India: A Review of Care, Training, Research, and Rehabilitation Programs J. P. DAS

Methodology of Psychopharmacological Studies with the Retarded ROBERT L. SPRAGUE AND JOHN S. WERRY

Educational Research in Mental Retardation SAMUEL L. GUSKIN AND HOWARD H. SPICKER

Process Variables in the Paired-Associate Learning of Retardates ALFRED A. BAUMEISTER AND GEORGE KELLAS

Author Index-Subject Index

Volume 4

Volume 5

Sequential Dot Presentation Measures of Stimulus Trace in Retardates and Normals EDWARD A. HOLDEN, JR.

Memory Processes in Retardates and Normals NORMAN R. ELLIS

Cultural-Familial Retardation FREDERIC L. GIRARDEAU

A Theory of Primary and Secondary Familial Mental Retardation ARTHUR R. JENSEN

German Theory and Research on Mental Retardation: Emphasis on Structure LOTHAR R. SCHMIDT AND PAUL B. BALTES

Inhibition Deficits in Retardate Learning and Attention LAIRD W. HEAL AND JOHN T. JOHNSON, JR.

Volume 6

Growth and Decline of Retardate Intelligence MARY ANN FISHER AND DAVID ZEAMAN

Cultural Deprivation and Cognitive Competence J. P. DAS

The Measurement of Intelligence A. B. SILVERSTEIN Social Psychology and Mental Retardation WARNER WILSON Mental Retardation in Animals GILBERT W. MEIER

Author Index-Subject Index

Stereotyped Acts ALFRED A. BAUMEISTER AND REX FOREHAND Research on the Vocational Habilitation of the Retarded: The Present, the Future MARC W. GOLD

xiii

Contents of Previous Volumes Consolidating Facts into the Schematized Learning and Memory System of Educable Retardates HERMAN H. SPITZ An Attention-Retention Theory of Retardate Discrimination Learning MARY ANN FISHER AND DAVID ZEAMAN Studying the Relationship of Task Performance to the Variables of Chronological Age, Mental Age. and IQ WILLIAM E. KAPPAUF Author Index-Subject Index

Volume 7 Mediational Processes in the Retarded JOHN G. BORKOWSKI AND PATRICIA B. WANSCHURA The Role of Strategic Behavior in Retardate Memory ANN L. BROWN

The Role of the Social Agent in Language Acquisition: Implications for Language Intervention GERALD 1. MAHONEY AND PAMELA B. SEELY Cognitive Theory and Mental Development EARL C. BU'ITERFIELD AND DONALD J . DICKERSON A Decade of Experimental Research in Mental Retardation in India ARUN K. SEN The Conditioning of Skeletal and Autonomic Responses: Normal-Retardate Stimulus Trace Differences SUSAN M. ROSS AND LEONARD E. ROSS Malnutrition and Cognitive Functioning J. P. DAS AND EMMA PIVATO Research on Efficacy of Special Education for the Mentally Retarded MELVIN E. KAUFMAN AND PAUL A. ALBERT0

Conservation Research with the Mentally Retarded K E N M. WILTON AND FREDERIC J. BOERSMA

Subject Index

Placement of the Retarded in the Community: Prognosis and Outcome RONALD B. McCARVER AND ELLIS M. CRAIG

Volumo 9

Physical and Motor Development of Retarded Persons ROBERT H. BRUININKS

The Processing of Information from Short-Term Visual Store: Developmental and Intellectual Level Differences LEONARD E. ROSS AND THOMAS B. WARD

Subject Index

Information Processing in Mentally Retarded Individuals KEITH E. STANOVICH

Volume 8

Mediational Processes in the Retarded: Implications for Teaching Reading CLESSEN J. MARTIN

Self-Injurious Behavior ALFRED A. BAUMEISTER AND JOHN PAUL ROLLINGS

1. CLAUSEN

Toward a Relative Psychology of Mental Retardation with Special Emphasis on Evolution HERMAN H. SPIT2

Theoretical and Empirical Strategies for the Study of the Labeling of Mentally Retarded Persons SAMUEL L. GUSKIN

Psychophysiology in Mental Retardation

xiv

Contents of Previous Volumes

The Biological Basis of an Ethic for Mental Retardation ROBERT L. ISAACSON AND CAROL VAN HARTESVELDT

Mainstreaming Mentally Retarded Children: A Review of Research LOUISE CORMAN AND JAY GOITLIEB

Public Residential Services for the Mentally Retarded R. C. SCHEERENBERGER

Special Skills A. LEWIS HILL

Research on Community Residential Alternatives for the Mentally Retarded LAIRD W. HEAL, CAROL K. SIGELMAN, AND HARVEY N. SWITZKY

Savants: Mentally Retarded Individuals with

Subject Index

International Review of RESEARCH I N MENTAL RETARDATION VOLUME 10

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The VisualSamrung andFixation Behavior of the Retarded1 LEONARD E. ROSS AND SUSAN M. ROSS DEPARTMENT OF PSYCHOLOGY UNIVERSITY OF WISCONSIN-MADISON MADISON, WISCONSIN

I. Introduction .......................................................... Developmental Changes in Visual Scanning ................................ 111. Developmental Theory and Scanning . . IV. Fixation and Visual Scanning in the Inte ................ A. Visual Fixation.. . . . . . . . . . . . . . . . . B . Visual Scanning i C. Visual Scanning i V. Concluding Comments ..................... References ............................................................ 11.

1.

1 5 11

24 27

INTRODUCTION

It is often observed that intellectually handicapped children demonstrate extreme deficits in performance on a variety of visual tasks. It is also apparent that visual skills have an important relationship to learning and the individual's effective functioning in the environment. Indeed, much of the information that must be acted upon to adapt effectively to the environment must be made available for processing and evaluation through the visual system. Not only is visual information necessary for cognitive activities, but normal intellectual development may be delayed or not occur if the usual cognitive experiences are denied to the child because of impaired visual functioning. Further, in many situations the evaluation of cognitive and linguistic skills depends upon responses to visual stimuli, 'Preparation of this article was supported by USPHS Grant HD 008240. 1 INTERNATIONAL REVIEW OF RESEARCH IN MENTAL RETARDATION, Vol. 10

Copyright @ 1981 by Academic Rcss. Inc. All rights of rcpmduction in any form rcscrvcd. ISBN 0-12-3662109

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Leonard E. Ross and Susan M . Ross

and an individual’s abilities may be seriously underestimated when visual processes are impaired. Despite the importance of the visual modality for intellectual development and performance, relatively little research has evaluated visual functioning as it relates to the behavior of the intellectually handicapped. In particular the study of eye movements, and their relationship to information intake and evaluation, has received only minimal attention. There are a number of reasons for this. First, the failure of the retarded to respond in a manner indicating cognitive competence is almost routinely attributed to attentional or cognitive deficits at a much later level or stage of processing activity. Evidence has accumulated that points to the organizational stages of cognitive functioning as a major source of difficulty for the intellectually handicapped, and the possibility that at least part of the problem for some individuals might relate to the initial intake of information at the level of the visual system has, as a consequence, been relatively neglected. Second, the original interest in receptor orientation as an important component of attention has not been continued. While Pavlov and later Soviet investigators considered receptor orientation to be an aspect of the orienting response, most recent investigators have not been concerned with such overt responses but have employed psychophysiological response measures, e.g., autonomic, cardiac, and to a lesser extent vasomotor activity, in their study of orienting and related attentional activity. Similarly, Zeaman and House’s influential attention theory, which identified the retarded child’s problem in discrimination learning tasks as reflecting attentional rather than learning factors, dealt with attention as a poststimulus-reception process. Third, the fact that early research failed to demonstrate strong relationships between patterns of eye movements and reading performance led to a general dismissal of eye movements as an important aspect of intellectual functioning, except in cases of clear cut oculomotor pathology. The claims and controversy concerning developmental vision training involving sensory-motor exercises further discouraged work in this area. More recently, however, interest in eye movements and their relationship to cognitive activity has developed as an active research area. Numerous studies have investigated the visual scanning of the nonretarded as it relates to topics such as picture perception and information intake strategies, and eye movement patterns are increasingly used as indices of attention and cognitive activity. With the great increase in research on reading, eye movement characteristics are again being investigated as an important aspect of the reading process (Rayner, 1978). More importantly for the topic of this article, studies have examined changes in visual search strategy as a developmental phenomenon, and experiments comparing the eye movements of the intellectually handicapped and nonhandicapped in various learning and perceptual situations have appeared with increasing frequency in the literature.

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In part this recent interest in the visual processes of the handicapped reflects the fact that while a deficit in visual scanning skills may affect the intellectual development and performance of any child, such deficits can severely impede retarded students’ acquisition of even rudimentary skills. Under such circumstances the improvement of visual performance might be expected to have a multiplier effect on the ability of the child to function effectively. In order to improve visual performance, however, it is necessary to determine the visual skills that are required for satisfactory cognitive functioning and the manner in which the handicapped individual’s visual abilities deviate from those that are desirable. It should be noted that while visual information intake and the subsequent utilization of that information are highly dependent upon visual scanning, visual scanning is itself a complex behavior that is related to a number of factors. Among these are the characteristics of the stimulus display and the viewer’s interests, motivation, and experience with the visual material. Optimal scanning may require the use of cognitively mediated strategies that are beyond the ability of the individual, so that deficient scanning may be both a cause and an effect of cognitive deficit. In any case, however, it is unwise to assume that when visual scanning difficulties are found they represent a basic and irremedial characteristic of the retarded child. While the identification of scanning differences may help explain behavioral differences, such information should be viewed as the necessary initial step toward the goal of developing programs to remedy visual scanning problems. At the very least, knowledge of the visual capabilities of the intellectually handicapped should result in the arrangement of their visual environment to optimize visual performance. Eye movements made in observing the elements of a stationary array consist of a series of very fast (10-20 msec duration) eye movements called saccades, which move the foveal fixation area from location to location. The interval during which the eye maintains a more or less steady fixation depends upon a number of factors; in normal reading saccades occur approximately every 250 msec while the interval may be extended in other viewing situations depending upon the visual material and task demands. While the function of eye movements in bringing retinal images to the fovea for the best visual acuity is obvious, there is some evidence that saccades may also aid in the processing of visual information even when the image is foveal and acuity is maximum (e.g., Kowler & Steinman, 1977). The mechanism that might account for this effect is not clear. Although Kowler and Sperling (1980) have recently demonstrated that the abrupt onsets and displacements of information that occur with saccades do not improve information acquisition, it is quite possible that some aspect of the occurrence of saccades could be related to efficient information intake. The saccade itself has characteristics that have led investigators to consider it

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Leonard E . Ross and Susan M . Ross

to be preprogrammed and executed in a ballistic fashion, although recent work

has demonstrated that the saccadic system continuously processes visual information, and can program saccades in parallel (Becker & Jiirgens, 1979). The programming of saccades, the determination of the fixation interval during which information is extracted, and the processes that overcome the discontinuity of visual input form a very complicated system in which a variety of information evaluation and oculomotor processes interact. Under these circumstances it is not surprising that problems may arise at various places in the system such that the visual scanning of the retarded is less than optimal. Note also that there are a number of acuity problems, as well as neurologic and oculomotor abnormalities such as the various forms of nystagmus, strabismus, and oculomotor apraxia, that may seriously affect the visual competence of the individual. These latter problems will not be considered in this article, nor will visual handicaps involving acuity and color vision (see Ellis, 1979, for the etiology and epidemiology of these handicapping conditions) or optometric vision training that involves eye exercises and developmental vision training programs (see Keough, 1974). The literature review that follows is divided into sections concerned with (1) developmental changes in visual scanning, (2) theoretical formulations concerning development that have implications for scanning behavior, and (3) the fixation and scanning characteristics of the retarded. It should be noted that in evaluating research on scanning a distinction should be made between those studies in which the scanning behavior is inferred from other behavior and those in which eye movements are actually observed or recorded by photographic or other means. In the case where eye movements are not directly recorded caution should be exercised in interpreting the measures employed, e.g., the latency of choice responses or the order of naming pictures in an array, as isomorphic with the child’s eye movement scanning pattern. Also, as has been pointed out by Day (1975), the use of terms such as “systematic” or “nonsystematic ” as they are applied to scanning must carefully be examined since their use may reflect a particular interpretation of what is adequate for the task situation. Similarly, a word such as “systematic” cannot be considered to be synonymous with “organized” or “planned,” since eye movement sequences that are apparently nonsystematic or inefficient may in reality be planned or rule governed, but in a manner different from those judged to be most effective. A final caveat with respect to the evaluation of research on scanning behavior concerns the effects of variables that may affect scanning although they are not a part of the scanning process per se. Reference here is to factors such as the individual’s understanding of the task, the general distractability of the individual, the task situation’s reward structure, and the appropriateness of the level of task difficulty. If such factors differ for the developmental or intellectual levels being compared, performance differences due to them may be incorrectly

SCANNING AND FIXATION BY THE RETARDED

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attributed to the oculomotor or cognitive processes or interest. Unfortunately, often it is not possible to evaluate the effects of such factors on the visual behavior being examined.

II. DEVELOPMENTAL CHANGES IN VISUAL SCANNING There are several reasons why examination of age changes in the visual scanning of the nonretarded is of importance in considering the scanning characteristics of the retarded. First, it is often the case that the performance of the retarded shows considerable similarity to that of younger nonretarded individuals. Thus a knowledge of developmental trends in visual performance may suggest the type of performance that may be expected and indicate the degree of deficit involved. Second, such knowledge may provide information concerning the normal course of improvement and the level of visual performance that would correspond to the desired task performance. Finally, knowledge of factors, such as stimulus configuration characteristics, that can change the visual functioning of younger children toward greater correspondence with that of older children may be valuable in suggesting variables that could be important in training the handicapped to use more effective scanning patterns. Even if a “remedial” rather than a “developmental” model is assumed in work with groups such as the severely handicapped, developmental information may still be of considerable value. Fortunately, a comprehensive review of developmental trends in visual scanning is provided by Day (1975). This review will not be duplicated, but the author’s conclusions will be presented and briefly discussed. The studies reviewed by Day (also see Vurpillot, 1976) indicate that children show an increase in systematic scanning between the ages of 3 and 11. Importantly, this increase interacts with stimulus configuration factors in that younger children can respond more systematically if there is a contextual aid, e.g., in terms of a patterning of the display. Studies that have examined characteristics of visual stimulus arrays and their relationship to children’s visual scanning show that younger children are in general more affected by contextual factors both in the case of those that aid visual scanning, as in the case of symmetric stimuli arranged in a pattern, and those that interfere with scanning, as in the case of complex patterns or the presence of visual distractors. A second important aspect of visual scanning discussed by Day is its exhaustiveness, defined as the proportion of the total stimulus array that is scanned. The exhaustiveness of scanning has been found to increase with age, although the generality of this statement must be qualified since exhaustiveness may decrease with increases in the efficiency of scanning. Unfortunately, the interrelationships among age, familiarity with the material, and its characteristics do not appear to

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Leonard E . Ross and Susan M .Ross

have been investigated to any great degree. In the case of match-to-sample tasks, exhaustiveness increases with age, although with the adoption of a more efficient selective scanning strategy older children may show less exhaustive but more efficient scanning patterns. The progression from exhaustive to efficient selection scanning may well be related to cognitive processes, such as formation of internal models or schemas (e.g., Jeffrey, 1968), which permit extraction of the essential information with a reduced number of fixations. The ability to focus on the most important elements of a visual display is another aspect of visual scanning identified by Day as increasing with age, and is one in which the execution of scanning eye movements and the operation of cognitive-perceptualprocesses are both involved. Clearly, the scan pattern must be sufficient to bring the relevant stimuli into view. In addition, the individual’s ability to maintain the fixation to permit the evaluation of the information, and to control subsequent eye movements appropriately in order to focus on the most informative parts of the display, is essential. On the other hand the evaluation of the fixation by fixation information, the identification of the most informative aspect of the display, and the modification of the scan pattern to concentrate fixations in the appropriate area depend upon the cognitive activity of the viewer. In some cases less cognitive activity would appear to be involved. For example, focusing on the informative aspects of a particular stimulus may require as simple a strategy as scanning the contours of the stimulus rather than its interior. Efficient scanning in such situations might change with age and become more automatic due to perceptual experience with shapes, the better understanding of the task demands, or both. Although many of the studies reviewed by Day have limitations in that scanning behavior was inferred rather than measured directly, and the literature is often incomplete with respect to the examination of the interaction of stimulus and task variables with scanning behavior, a rather clear cut and predictable pattern emerges. As might be expected, increasing age brings increasing efficiency of scanning in terms of its systematic quality, its appropriate exhaustiveness, and its focus upon the most informative aspects of the visual scene. In particular the finding that context can affect the scanning behavior of younger children suggests that contextual manipulation could be effective in improving the scanning behavior of the intellectually handicapped. In addition to the work with scanning, there has been considerable interest concerning developmental changes in the related topic of the child’s useful visual field of view, which as defined by Mackworth and Bruner (1970, p. 158) is, “the area around the fixation point from which information is being temporarily stored and then processed during a visual task. ” There are at least two major issues involved in a consideration of the developmental differences in the useful field of view. The first is the question of changes in peripheral sensitivity as measured by conventional acuity procedures, while the second concerns developmental dif-

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ferences in the processing and use of available information at different retinal locations, including the use of parafoveal and peripheral information in the programming of eye movements. The clearest apparent evidence for age differences in peripheral vision acuity in children was provided by Lakowski and Aspinall (1969) who used a perimeter to obtain luminance thresholds for spots of light. Whiteside (1976), however, failed to obtain a similar age relationship when peripheral sensitivity was examined using eye movements to flashes of light as the response measure. Whiteside suggested that three aspects of the Lakowski and Aspinall procedures were open to question, i.e., the extent to which the children maintained center-screen fixation, understood instructions, and were able to perform a tedious task. Such factors would, of course, also be relevant in considering the results of studies which have compared the extraction and utilization of information from the fovea and periphery in investigating developmental differences in the useful field of view. Generally, as reviewed by Day the evidence suggests that children have a smaller useful field of view, possibly due to their greater susceptibility to a processing overload condition which presumably restricts the useful visual field. If this is the case then children would be limited, relative to adults, in the use of peripheral information in the planning of eye movements in visual search. Since Day’s (1975) review a number of studies have appeared that have implications for the question of developmental changes in sensitivity to peripheral or background cues in visual search. The peripheral visual processing of 5- and 8-year-old children and adults was compared with and without foveal load by Holmes, Cohen, Haith, and Momson (1977). These authors found an interaction between age and target distance with the children’s performance falling off more rapidly than that of adults, although even the 5-year-olds performed with better than 50% accuracy, after corrections for guessing, at the farthest distance. Interestingly, for 8-year-olds and adults the presence of a foveal form stimulus, even with instructions to ignore it, produced a decrement in peripheral performance as great as that found when subjects were required to report the form. The performance of the 5-year-old children was not affected by either the number of stimulus items present or the number to be reported, however. Cohen and Haith (1977) also examined information processing in the periphery, in terms of children’s and adults’ ability to judge the similarity of geometric forms. In neither of this study’s two experiments was age involved in any interactions in a manner that suggested a developmental trend. The main effect of age was significant in one study, where 8-year-olds were superior to both 5-year-olds and adults, but not in the other. The results were interpreted as failing to support notions of developmental differences in peripheral processing skills, at least in tasks such as those employed. Spragins, Lefton, and Fisher (1976) examined the eye movements of third- and fifth-grade children and adults during reading and the search of spatially perturbed text and found an increasing

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M .Ross

dependence upon peripheral cues with age and reading experience. Fisher and Lefton (1976) gave third-, fourth-, and sixth-grade children, and adults, paragraphs to read and search for targets and concluded from reading and search speed that the functional field of view depends upon age, experience, and several situational factors as well. Other results from a tachistoscopic reaction time task were also interpreted as showing information extraction in the periphery to be poorer in children than in adults. Bisanz and Resnick (1978) found localization, defined by them as the preliminary analysis of information located in the periphery used to determine the direction of eye movements in locating an object, to increase from ages 8 to 12 in a visual search task. Finally, Day (1978) reported decreasing visual search times with age (7-, 9-, and 12-year-old children), but different developmental trends were found as a function of background variation. This led Day to suggest caution in accepting general statements regarding the relationship between selective attention and age. It might be noted that these later studies reference their finding to Hochberg’s (1970) distinction between peripheral and cognitive search guidance processing, which is briefly discussed below. While the developmental data on the use of peripheral information are not entirely consistent there is sufficient suggestion of important developmental differences to warrant further studies, particularly those that examine task characteristics and the child’s ability to utilize peripheral information in situations where use of this information is likely to be important in the programming of efficient eye movements. It is also evident that the use of peripheral visual information might represent a problem for handicapped children regardless of the extent of which developmental differences are found.

111.

DEVELOPMENTAL THEORY AND SCANNING

A number of theorists have postulated that a relationship must exist between various kinds of perceptual activity and experience in order for the general development of both perceptual and representational structures to occur (e.g., see Vurpillot, 1976). In these accounts the visual modality predominates, and thus visual scanning must be considered to be an important factor. There also have been several theoretical approaches that have related perceptual development to motor correlates of receptor activity such as eye movements (see Whiteside, 1976, for a brief discussion of these theories). In addition there are developmental hypotheses or theories that have particular relevance for children’s scanning behavior. In 1968 Jeffrey proposed a serialhabituation attentional hypothesis to account for the development of schemata. In his account an infant exposed to a stimulus attends to the most salient stimuli, but with continued exposure the orienting response to those stimuli habituates and

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less salient cues elicit attending responses. With experience this sequence of habituation and attending responses becomes a continuous, integrated, response sequence that, at some point, is discontinuous with other response sequences that preceded and follow it. This twofold process of integration and discontinuity results in an object percept or schema, with developmental differences in problem solving reflecting children’s experience with relevant schemata and their ability to develop the necessary schemata or utilize them as required. The dependence of the development and use of schemata on eye movements was addressed by Jeffrey, who suggested that the scanning involved in the initial formation of a schema would be reduced as the schema became well developed, with the final stage requiring attending responses only to one or two of the more salient cues. An exception would exist when a discrepancy in input occurred, which could elicit the original, longer, sequence. Starting from Jeffrey’s assumptions, Furby ( 1974) extended attentional habituation concepts to an examination of differences in the problem solving behavior of retarded and nonretarded children. She proposed that lower IQ children respond more to salient cues due to their slower orienting response habituation and generally greater difficulty in inhibiting responses to these cues. Thus these children would not have as great an ability to use less salient or more abstract cues to form new schemata within a given period of time. While one cannot necessarily equate the attentional responses in these formulations with eye movements, i.e., it is necessary to keep the distinction between overt and covert attentional responses in mind in considering relationships of orienting to cognitive development, it is clear that the capability to execute patterns of eye movements could play an important role in serial habituation processes such as those discussed by Jeffrey and Furby. A developmental distinction concerned with selective attention that has relevance for an analysis of the visual scanning behavior of the handicapped has been made by Wright and Vlietstra (1975). These authors posit a major developmental shift in the mode of organizing sequences of observing behavior from exploration, which is relatively spontaneous and nonsystematic, to search, which is more systematic, planned, and may occur at either the perceptual or cognitive level. This shift is paralleled by a change in the control of attention from the salient features of stimuli to the logical features of the task. During the transition to search behavior salient stimulus features provide limited help, but can be a serious source of interference when irrelevant and thus distracting. Exploratory behavior is seen by these authors as a necessary precursor to systematic search behavior. The transition is suggested to be related to the occurrence of concrete operational thought, the use of verbally mediated concepts, and the use of logically based strategies, which would normally appear during the 5-7 age range. This cognitive change can be related to Piaget’s concept of decentration (see the later discussion of work by Wilton & Boersma,

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1974a. concerned with conservation acceleration in nonretarded and retarded children), White’s hierarchical model of the shift from associative to cognitive levels of responding, and the impulsive-reflective cognitive style distinction. Applied to visual behavior, the exploration-search distinction would emphasize the necessity of visual exploration in the development of schemas. With visual-perceptual experience and the related emergence of cognitive capacities the shift from exploratory-type scanning to systematic search, guided in many cases by cognitive strategies, would occur. Again the emphasis would appear to be on the symbiotic relationship between efficient visual scanning and normal cognitive development, although presumably there are perceptual modes of visual search that are somewhat less dependent upon cognitive factors. In the case of the intellectually handicapped the mechanisms of visual exploration or search andlor the necessary underlying cognitive abilities might be the source of difficulty. The suggestion is that work to improve both may be necessary for advances in intellectual functioning. While there is currently considerable interest in, and disagreement about, visual search factors during reading, Hochberg (1970, 1976) has proposed a two-stage processing model that has proved useful in developmental visual search studies, e.g., such as those by Spragins et al. (1976), Fisher and Lefton (19761, and Bisanz and Resnick (1978). Although this model is directed to the reading process, its distinction between peripheral and cognitive search guidance has relevance to all visual search situations. The first stage, which has been referred to as localization, involves an analysis of the information located in the visual periphery where acuity is low. This analysis directs eye movements that result in foveal fixation of the information, where information is extracted from the visual material through higher order processes. The peripheral search guidance or screening phase that guides subsequent eye movements is postulated to be increasingly efficient, and increasingly depended on, with age or experience. The studies mentioned above support this position. The implication from this area of research, as well as from similar ideas proposed by Neisser (1967) and Lefton and Haber (1974), is that the slower or more inefficient visual search shown by some handicapped individuals could reflect either poorer peripheral processing of potential targets or problems in the use of such information in programming saccades. This brief summary of the developmental visual search literature, and the theoretical positions selected as particularly relevant to this topic, m&e it quite clear that there are important developmental differences in visual search. Accordingly there are many reasons to believe that delayed or deficient eye movement processes on the part of the retarded child have serious effects both on their cognitive and perceptual development and their ability to function efficiently in situations requiring visual search. It is also evident that efficient eye movements represent complicated interactions among cognitive processes relating to the

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intake and analysis of visual information, the cognitive activity involved in the utilization of that information in the programming of saccades, and the mechanisms and processes associated with the actual execution of eye movements. The analysis of this complex system, with its close interrelationships between eye movements as reflecting cognitive activity and the cognitive activity made possible by oculomotor activity, will not be simple. In fact it will be particularly difficult since the retarded may exhibit problems in any or all of these aspects of the eye movement system.

IV. FIXATION AND VISUAL SCANNING IN THE INTELLECTUALLY HANDICAPPED While the number of studies of the eye movements of nonhandicapped children is not great, there are even fewer experiments that have examined the fixation and scanning behavior of the retarded. To some extent this may reflect the greater difficulty of obtaining eye movement data from the retarded since the more exact recording procedures, e .g., those employing photocells and reflected infrared light, the Mackworth corneal reflectance method, or electrodes to obtain EOG data, depend upon at least the tolerance of the child if not his or her active cooperation. The apparatus may appear strange and at times be uncomfortable, and it is necessary to limit head movements to an absolute minimum during recording. In addition, the recording of eye movements by these methods requires fairly sophisticated equipment and the technical knowledge to obtain good, artifact-free, records. The direct observation, photography, or videotaping of eye movements in the naturalistic or laboratory task situation may offer fewer apparatus and head positioning difficulties, but these methods can require more pilot work and experimenter time to develop reliable data acquisition and scoring procedures and are generally less precise. Other factors leading to the lack of eye movement studies with the retarded include the difficulty of transporting eye movement recording equipment, which makes it necessary to bring children to the laboratory for testing, and the increasing number of obstacles encountered in obtaining access to handicapped children. The following survey of eye movement research with the retarded is divided into three sections that are concerned with (1) visual fixation, (2) eye movements in match-to-sample situations, and (3) eye movements obtained under other experimental conditions.

A.

Visual Fixation

The effective intake of visual information requires not only the necessary eye movements to bring the material into foveal regard, but also the maintenance of

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fixation a sufficient length of time to permit processing of the stimuli. Failure to maintain visual fixation produces new visual input that may interfere with the necessary cognitive activity consequent to the previous fixation, which in turn could have deleterious effects upon the efficient programming of subsequent eye movements. Given the complicated nature of the interrelationship between eye movements and the integration of information across saccades (e.g., see Rayner, 1978), inappropriate fixation-saccade relationships could have serious effects upon the cognitive functioning of the individual. It should be noted, however, that while failure to fixate for the necessary duration during sequences of eye movements may be disadvantageous, it is also the case that fixating certain stimulus aspects for an inappropriately long period may also interfere with cognitive functioning. Certainly fixation in lieu of the appropriate scanning is maladaptive, and it has been proposed that the proper sequence and pacing of attending responses, from the more salient to the less salient features of the stimulus object, may be necessary for the formation of object percepts or schemas. While the duration of fixations is thus an integral part of visual scanning, the degree to which visual fixation is maintained on task relevant stimuli is also an important component of visual performance. The overt visual attention, i.e., general task-relevant fixation, of the retarded has been examined in a number of experimental learning and performance situations. There has long been an interest in the presumed distractability of the retarded, although the common stereotype of the retarded as distractable has been called into serious question by a number of investigators (e.g., Baumeister & Ellis, 1963; Belmont & Ellis, 1968; Sen & Clarke, 1968; and Turnure, 1970). In general it appears that distraction conditions, as defined by the experimenter, do not always result in poorer performance on the part of the retarded, and the effects of distraction may interact with many subject and environmental factors. It is a fact, however, that in some situations the retarded do fail to maintain visual fixation and that this behavior is accompanied by substantial task performance decrements. Regardless of whether such off-task eye movements are primarily related to internal CNS factors, are elicited by distracting environmental stimuli, or represent attempts to seek information from the environment, they clearly can interfere with performance. When off-task glancing behavior (overt head movements) of retarded and nonretarded children performing object-assembly tasks were examined by Turnure and Zigler (1964, Study 11) they found that significantly more glances were made by the retarded children (mean CA = 13.5 years, mean MA = 7.4 years) than their 6.0- and 6.4-year-old MA matched (mean MA = 7.4 years) controls, both under conditions where the glances could be informative in terms of the actions of the experimenter and where they were not. Under all task conditions, except those arranged so that the information obtained by glancing would at-

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tenuate performance, the retarded children’s object assembly performance was superior to that of the nonretarded children, however. The off-task glancing behavior of the retarded children was interpreted by the authors as a manifestation of the greater outer-directed style of the retarded, which was believed to reflect the level of cognitive ability attained and the success that had resulted from this kind of behavior in the past. Obviously, as the authors point out, this outer directednesscould either aid the child or be detrimental depending upon the particular task circumstances. In a subsequent study Turnure (1970, Study I) compared the off-task glancing behavior of retarded (mean IQ of groups ranging from 45.4 to 51.3) and nonretarded children while they were performing an oddity problem task under mirror distraction and no-mirror distraction conditions. In terms of frequency of glancing the retarded subjects glanced off task less frequently than did MA comparison groups, but not differently than a CA comparison group. With respect to total time glancing, the retarded subjects glanced more than their MA comparison subjects without the mirror present but less with the mirror present, and again did not differ from their CA comparison group. An analysis of the mean time glancing prior to the subject reaching criterion on the oddity problem revealed, however, that the retarded subjects did glance away approximately three times longer than their CA comparison subjects under both mirror and no mirror conditions. The precriterion glancing time was significantly negatively related to learning scores on the oddity task (r = - .41), but a number of glances was not ( r = - .33). Turnure interpreted his data as indicating that the retarded are not attentionally deficient unless they are given a task of inappropriate difficulty, and therefore show more off-target glancing behavior only when compared to CA-matched nonretarded subjects. This position is similar to that of Sen and Clarke (1968) who suggested that low intelligence may be related to low task performance due to initial task difficulty leading to susceptibility to distraction. Visual attention also has been examined in reaction time situations where a warning signal precedes a signal to respond. A number of studies (e.g., Sroufe, 1971; Sroufe, Sonies, West, & Wright, 1973; Krupski, 1975) have examined childrens ’ attentional processes occurring during the preparatory interval between the warning and reaction signals in terms of heart rate indices of the orienting response. The fact that the retarded show generally slower and, especially, more variable reaction times has been attributed to their lack of sustained attention, and indeed Krupski (1975) found that retarded (mean CA = 21 years, mean IQ = 70) subjects had lower magnitude heart rate decelerations, i.e., less accurate covert training of the length of the preparatory interval and hence slower reaction times, than did matched CA nonretarded subjects. It would also be expected from this analysis that nonretarded and retarded children would differ in their overt visual attending behavior during the preparatory interval of a reaction time task. This prediction was confirmed by Krupski (1977) who found slower

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reaction times and more off-task glancing by retarded adolescents (mean CA = 15.6 years, mean IQ = 64.8) than by nonretarded adolescent comparison group subjects (mean CA = 15.4 years). Kmpski and Boyle (1978) also demonstrated that young nonretarded children 7-8 years of age who were slow responders in a reaction time task glanced off task significantly more than fast responders. Other investigators have studied the duration of attending to particular stimuli without the subject being given a particular task. Terdal (1967) presented two checkerboard patterns simultaneously, one constant and one varied across trials, to retarded young adults (mean CA = 20.4 years, mean IQ = 57), a younger preadolescent retarded group (mean CA = 11.3 years, mean IQ = 44), and nonretarded MA and CA comparison groups. The time spent looking at each or neither of the designs was recorded and analysis revealed that the duration of not looking at either design was greater for both of the retarded groups than for their CA controls, and was also greater than that of their MA comparison subjects, although the difference was significant only in the case of the older retarded subjects on later trial blocks. All groups of subjects attended to the varied design more than the constant design by a wide margin. It might also be noted that Mackworth, Grandstaff, and Pribram (1973) found that severe aphasic children fixated an element of a stimulus array that changed color from white to red much longer than nonaphasic children, but that mild aphasic children were slow to orient to the color change and spent more time looking off target than the nonaphasic comparison children. These results suggest that the kind of inappropriate fixation behavior may vary greatly among children from the same diagnostic category. Since many of the behaviors of hyperactive and retarded children have been shown to be amenable to behavior modification techniques, it would appear that fixation behavior might also be changed to benefit the individual. Quay, Sprague, Weny, and McQueen ( 1 967) reported that hyperactive aggressive children could be conditioned as a group to increase their visual orientation toward a teacher through the use of candy and/or social reinforcement. Many behavior modification programs also shape the general attending behavior of retarded children so that they attend more to the teacher. In addition Maier and Hogg (1974) demonstrated that operant conditioning procedures could be used to increase the visual fixation of hyperactive severely retarded children (mean CA = 8.9 years, median MA range of less than 18 months to 3.3 years) to various toys, educational materials, and cartoons, through the use of social and edible reinforcers. The increased visual fixation of these children was also found (Hogg & Maier, 1974) to transfer to different situations and stimuli, as indicated by an increase in visual fixation from pre- to postoperant conditioning tests separated by a 5- to 6-month interval. However, methodological problems suggest caution in interpreting these transfer results, as the authors point out. Finally, Jackson ( 1979) reported that a differential reinforcement procedure involving a visual

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feedback stimulus increased both attending behavior to a chain-cutting task and performance on that task by a moderately retarded adult male. Given these data it appears quite feasible to use operant conditioning procedures to improve visual fixation behavior.

B. Visual Scanning in Match-to-Sample Situations It is obvious that eye movements are of importance in many tasks involving the selection of one or two or more visually presented alternatives. There are a variety of situations in which a number of stimulus items must be compared visually before the response takes place in order to attain better than chance levels of performance. Thus, for example, visual discrimination learning tasks, receptive-language color-learning problems, and match-to-sample tasks may require eye movements in order to make the necessary comparisons; and such eye movements may be of greater than normal importance when the individual’s encoding or memory processes are deficient. In some situations only one or two fixations may be sufficient to receive the necessary visual information, while with other tasks rather complex scanning strategies may be required for efficient selective responding. It should be noted that in the former case the problems faced by the handicapped in visually fixating the stimulus display in the required manner may be overlooked since visual orienting to the elements of a task is an automatic, rarely noticed, process for nonhandicapped individuals. Also, the required eye movements, as well as the cognitive comparison and decision processes involved, require some interval of time between stimulus presentation and the response. In some situations this interval may be quite short while in others a relatively long delay may be required in order to permit the selection of the correct alternative. This relationship between latency of responding and the occurrence of the necessary visual comparison and other processes makes one paradigm of particular interest in considering the role of eye movements in selective response situations. This is the match-to-sample task in which a standard and alternatives are presented with a requirement that the alternative be selected that exactly matches the standard. The match-to-sample paradigm is to be distinguished for this discussion from visual search situations in which, typically, many objects are present and the one object to be found is described or illustrated. While the distinction is a minor one in some cases, match-to-sample tasks generally employ fewer alternatives and involve comparison eye movements to a greater extent than is the case in visual search tasks such as those described in the next section. Match-to-sample tasks are widely used in training programs with the handicapped and one instrument, the Matching Familiar Forms Test or MFF (Kagan, Rosman, Day, Albert, & Phillips, 1964), has been used extensively to investigate the cognitive-style dimension of reflection-impulsivity (e.g., see Messer,

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1976). The relevance of the reflective-impulsive distinction for special education has been discussed by Epstein, Hallahan, and Kauffman (1975), and the modification of impulsivity and its implications for the learning of exceptional children have been examined by Digate, Epstein, Culliman, and Switzky (1978). Match-to-sample tasks can range widely in difficulty from the relatively easy, where the alternatives are few in number and quite dissimilar, to the very difficult, where very detailed standards and alternatives are used that differ only slightly. Correspondingly, visual requirements can differ greatly depending upon the characteristics of the matching task. In the simple case a single fixation may, depending upon the visual angles involved, provide the necessary information. In contrast, the more difficult problem may require a quite long period of comparison scanning with scanning strategy and memory playing an important role. This is not to say that the importance of eye movements always differs in the two situations. The severely or profoundly retarded child may have a quite difficult time making even a few fixations in the area of the stimuli in the simpler situation, while the problem for a nonretarded child in the difficult task could be primarily related to memory processes or the willingness to persist in scanning the standard and alternatives rather than to eye movements per se. Lefton, Lahey, and Stagg (1978; also see Lefton, 1978, for a further discussion of these data) provide an interesting study that demonstrates that search patterns rather than fixation of the material per se may be important in some situations. These authors examined the eye movement behavior of fifth-grade reading-disabled students who had IQs ranging from 85 to 115 but who were reading at a third-grade level or lower, normal third- and fifth-grade children, and adults, in an untimed match-to-sample task involving a sample and four alternative sets of five different unusually confusable consonants. Somewhat surprisingly, frequency of fixations decreased with increasing developmental level, and although reading-disabled children looked more often than any other group, they made significantly more errors. The important factor was found to be search strategy, with the reading-disabled group showing eye movement patterns that were nonsystematic and relatively ineffectual. The problem appeared to be partly one of sustaining attention in the task since the breakdown in systematic eye movements occurred after the first five or so eye movements, or approximately 5 seconds after search began. The reflective-impulsive distinction is important for the present discussion because some intellectually handicapped individuals are characterized as impulsive (i.e.. fast and inaccurate) responders and because it is believed that this may create a greater problem for the handicapped child than for the correspondingly impulsive nonhandicapped child. There have been a number of attempts to modify the impulsive like behavior of the retarded and thus improve their performance. A variety of these techniques have been found to be effective with the retarded including response-cost procedures (Errickson, Wyne, & Routh, 1973),

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visual discrimination training (Duckworth, Ragland, Sommerfeld, & Wyne, 1974), the delay of the opportunity to respond (Lowry & Ross, 1975), and modeling-self-instruction procedures (Guralnick, 1976). These studies were carried out with children with IQ scores in the EMR range except for the Lowry and Ross experiment where the subjects were severely or profoundly retarded. Similar success has been obtained by investigators in work with disadvantaged children (Strang, 1974; Egeland, 1974). In the absence of data relating the eye movements of the retarded to performance in match-to-sample situations or in studies where their training was intended to modify impulsive responding, it is necessary to consider research carried out on this topic with nonhandicapped children. Presumably differences in the eye movements of reflective and impulsive children in these situations would be mirrored to some degree by the eye movements of handicapped children in similar situations. Studies that have examined the eye movements of normal children on MFF and similar tasks have found scanning differences between impulsive and reflective children as they are defined on the basis of latency and error scores. In these studies it has generally been found that frequency and duration of looking behavior is greater for those classified as reflective, as might be expected since reflectives respond more slowly. In addition, however, a number of other interesting differences between reflective and impulsive children have been reported. Siegelman (1969) required fourth-grade children to press a button to bring the standard or an alternative into focus in the match-to-sample situation, and interpreted the resulting operant attending data as indicating a broad difference in search strategy. Reflectives were found to differentiate the properties of the array through the process of comparing alternatives and then the standard, while impulsive children were likely to compare the standard globally, in little detail, to one alternative at a time. Thus reflective children spent proportionally less of their total time and looks attending to the standard, and covered the array of alternatives more extensively. In a study that compared reflective and impulsive adults and children, Drake (1970) recorded eye movements in match-tosample tasks and found adults to be more reflective than third-grade children, and reflective subjects to look at a larger portion of the stimulus figures in greater detail and with more thoroughness. In a study of third-grade children by Zelniker, Jeffrey, Ault, and Parsons (1972) eye fixation data were obtained prior to, during, and after an experimental manipulation (identifying the one alternative that was unlike the standard) that was designed to change the subject’s scanning strategy. This manipulation did indeed decrease the percentage of fixations on the standard and increase the systematic comparisons of the alternatives, and this effect was found to transfer to the subsequent MFF task in the case of impulsive children. Finally, Ault, Crawford, and Jeffrey (1972) found that the eye movements of reflective and fast-accurate 9-year-old children were more sys-

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tematic and that they made more comparisons as compared to the impulsive and slow-inaccurate children. As is the case with the retarded, a number of procedures have been employed to attempt to improve nonretarded childrens’ performance on match-to-sample problems. These have included instructed or forced delay of responding, modeling, differentiation training, and the teaching of scanning strategies. While success has been mixed, Messer (1976) concluded that the most consistently positive results were obtained by either training the impulsives to use the scanning strategy employed by reflectives or by exposing the impulsive child to training material that forced a strategy change. The motivation of the child to avoid failure was also suggested to be an important factor in performance on these tasks. In sum, the data concerning the impulsive-reflective distinction and its relationship to performance on match-to-sample tasks suggest that teaching visual scanning strategies or employing other intervention tactics with respect to changing the eye movement behaviors of the intellectually handicapped could have important benefits in improving their performance in selective response situations. Such a change in scanning may not in itself be sufficient to result in large performance gains, but the utilization of the appropriate scanning strategy results in the reception of the relevant information and also delays the response in a manner that could be beneficial in permftting other cognitive activities to occur. In some instances delaying the response might be an effective procedure, while in others it would not. Clearly delay per se would not be expected to improve performance unless other processes, such as the requisite fixation or scanning behaviors, were available and occurred during the delay period. Thus in a situation where only minimal visual comparison of the stimuli is necessary a retarded child forced to delay a response might make a single fixation which could provide the necessary comparison, and then respond correctly, while such a delay might have little or no effect in a more difficult situation where the scanning strategy necessary for good performance was not in the child’s behavioral repertoire. It is clear that the training necessary for improving performance varies depending on the individual’s available visual skills and the demands of the task situation.

C. Visual Scanning in Visual Search and Other Task Situations Experimental study of the visual scanning of the retarded is of relatively recent origin. In the decade from 1961 to 1971 there were three studies, O’Connor and Berkson (1963), Berkson (1966), and Winters, Gerjouy, Crown, and Gorrell (1967), in which the eye movements of retarded subjects were recorded and analyzed. Four other experiments, Rosenberg (1961), Spitz (1969), Spitz and

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Borland ( 1971) , and Das ( 197I), examined the visual search behavior of retarded subjects in situations requiring the selection of the sample or standard from among a relatively large number of similar stimuli. In these studies eye movements were not measured; rather search time and error scores were used to determine the visual search characteristics of retarded and nonretarded subjects. The O’Connor and Berkson (1963) study compared nonretarded adults, Downs syndrome severely retarded adults (mean CA = 23.7, mean IQ = 32.7), and non-Downs syndrome severely retarded adults (mean CA = 24.0, mean IQ = 32.3) under experimental conditions that included darkness, one centered light, five lights arranged in a semicircle in front of the subject, and the one- or the five-light arrangement with the lights flashing. Eye position was not analyzed, but the groups were compared in terms of their total summed amount of eye movement. It was found that the Downs syndrome group made significantly more total eye movements than the other two groups, which did not differ, and that there was no groups by stimulus conditions interaction. The authors could offer no explanation for their results. Berkson (1966) found that some of a sample of profoundly retarded children (median CA = 3.4 years, developmental levels of less than 1 year) would respond to visual stimuli that were presented stationary or moving. The eye fixation response to the onset of movement was greater than to the offset of movement in terms of a decrease in operant eye fixations across time of presentation. The visual stimuli were 2.5-in.-diameter disks, on which were drawn multicolored random shapes, that could be rotated by means of a motor that made a “loud grinding noise.” It is unknown just what effects the presence, absence, onset, or offset of such noise might have had on the observed fixation behavior. In the Winters et al. (1967) study pairs of widely separated alphabetic and nonalphabetic stimuli were presented tachistiscopically to retarded (mean CA = 15.8 years, mean IQ = 59.8) and matched MA and CA comparison subjects. The instructions were to report both stimuli as soon as possible. Eye movements were recorded by two hidden observers. The relationship between spatial order of the stimulus reported and eye movements was significantly higher for nonretarded than retarded subjects, and the retarded subjects who were more consistent in their organization (directional sequence) of eye movements and verbal reports gave more correct responses and scored higher on a reading test. The results were interpreted as indicating that accuracy of recognition of the stimuli depended upon the degree of directional eye movement-verbal report consistency, in which the nonretarded were superior. Turning to the visual search studies, Rosenberg (1961) compared the search time and error scores of retarded subjects from two IQ levels (IQ ranges of 37-53 and 56-89 in the two groups) on a task that required locating each item of a series of nonsense shapes in a matrix of 36 such shapes. Two exposure conditions were used, continuous in which the item to be found was continuously displayed, and

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4-second presentations in which the item was displayed for 4 seconds and then removed during the subject’s search of the matrix. Under the continuous condition the higher IQ subjects required a shorter time to locate the nonsense shapes and made fewer errors in doing so. Considerably more errors were made by the 4-second condition groups, with the high IQ subjects again performing better than the low IQ subjects with respect to both time and error measures. Since nonsignificant interactions of IQ and task conditions were found for both measures the major finding of the study was that lower-IQ retarded subjects took longer to search a matrix for a matching shape and made fewer errors in doing so. In another visual search study, Spitz (1969) predicted that the performance of the retarded on a visual search task should show faster deterioration as target information decreased than would be the case for the nonretarded since the retarded would not be expected to organize incoming information or develop visual search strategies as well as the nonretarded. The task required the subject to identify the piece from a completed child’s jigsaw puzzle that matched a target piece, under various degrees of target-piece pictorial and shape information. Consistent with the prediction, the mean search time per target piece increased faster as a function of decreasing target information for retarded subjects (mean CA = 15.1 years, mean IQ = 63.6) and fourth-grade nonretarded children of approximately the same MA than for seventh-grade nonretarded children. In a related study, Spitz and Borland (1971) tested institutionalized (mean CA = 15.6 years, mean IQ = 61.4) and noninstitutionalized (mean CA = 15.8 years, mean IQ =68.8) retarded subjects and equal MA and CA comparison subjects on a task that required the subject to identify a centrally located standard figure from among 28 figures placed in concentric circles around the standard. The complexity of the target figures was varied, with targets of low to medium complexity leading to the longest search times in terms of mean search time per figure. Of the subject characteristics only MA was found to affect the level of visual search performance. Finally, Das (197 1) examined the visual search task performance of retarded subjects having a mean MA of 82.8 months, CAs ranging from 104 to 196 months, and IQs from 46 to 76. A comparison group of first-grade children with a mean MA of 78 months was also tested. The task involved the subject initiated presentation of a target word on a CRT, followed by the display of 4, 8, or 16 common three-letter words including the target word. The subject identified the target by touching the target with a light pen, which initiated another trial. While search time increased with field density, as defined in terms of number of words to be searched, there were no differences in search time between the retarded and nonretarded children of approximately equal MA. It is not clear to what degree these visual search studies are relevant to the question of possible deficits in the visual scanning behavior of the retarded. A variety of factors, e.g., response and encoding processes, other than those as-

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21

sociated with eye movement scanning per se could be involved in visual search situations such as these, especially in the instances where the standard does not remain available to the subject for comparison. In any case the absence of actual eye movement data makes assumptions about the scanning characteristic correlates of the search time and error measures tenuous at best. It is noteworthy, however, that there is no evidence in these studies of visual search differences related to retardation other than those associated with differences in MA levels. This conclusion must, of course, be qualified in terms of the IQ range and task parameters, e.g., difficulty, investigated in these studies. The visual search performance of retarded and nonretarded children was also the topic of interest in two more recent studies, reported by Boersma and Muir (1975), in which eye movements were recorded. In the first experiment the eye movements of 20 EMR children (mean CA = 10.4 years, IQ range 50-80) and 20 matched CA nonretarded children (mean CA = 10.6 years, IQ range 100135) were compared, through use of the corneal reflection technique, during two visual search tasks. In Task I Picture Absurdity items from the Stanford-Binet were presented and the subject instructed to determine what was wrong with the picture, while Task I1 also used Stanford-Binet items but with the absurdity removed and the subject instructed to respond to the question, “What is happening in the picture?” Task I was designed to investigate the eye movements of the two groups under specific directed search conditions, while Task I1 was also a directed search situation but without the constraint of searching for a specific element. The results for Task I showed that the nonretarded children had significant higher information search scores, defined as the summation of corneal reflections over the first 30 film frames (3 seconds) weighted according to the relative information content of the stimulus area where the reflection occurred, and also greater mean fixation durations. The groups did not differ in track length, computed as the summation of the angular displacement in degrees of arc of the subjects’ corneal reflections across the first 30 frames. In addition the nonretarded and retarded children differed in their initial areas of search in that the former were characterized as having the tendency first to search the center, while the latter first searched the periphery of the pictures. In the second, nonspecific, search task the nonretarded children again had higher information search scores, but the groups did not differ in the other two search measures. In general the results were interpreted as showing that the visual search behavior of the nonretarded children was more controlled than that of the retarded children. Given the necessity to observe the stimuli in a discrimination learning situation, it might be expected that eye movements would be related to discrimination learning performance and that retarded and nonretarded children would differ in their scanning behavior. The second study reported by Boersma and Muir (1975) investigated the eye movements of the same sample of children in a discrimination learning situation in which the child was required to indicate by pressing one

22

Leonard E . Ross and Susan M . Ross

of two buttons which of two rectangular stimulus configurations was correct. The rectangles contained an irrelevant square or diamond in the center, and different numbers of dots in the comers. The relevant dimension was number of dots, with the positive cue and odd number (1 or 3). Although the procedure was arranged so that additional information concerning the correct cue was given after 10 trials and even more information after 20 trials, the task was too difficult for the retarded children with only 4 of the 20 reaching a learning criterion as compared to 20 of 23 nonretarded children. This low performance level makes interpretation of the eye movement data difficult since eye movements might well be expected to vary with task difficulty differences of this magnitude. In any case the eye movement data were interpreted as showing that the retarded children were deficient in control of their eye movements as compared to nonretarded children, especially with respect to focusing upon the stimulus elements relevant to the solution of the task. In this regard the nonretarded children viewed relevant cues more, showed a greater increase in viewing relevant cues after information was given about these cues, and had more photo frames that were unscorable, but did not differ from the retarded in number of fixations. The final experiment to be reported in which the eye movements of the retarded were investigated was by Wilton and Boersma (1974b). This work, also reported with the exception of the third test series in Boersma and Wilton (1974, 1976) and Wilton and Boersma (1974a), was based on research findings indicating that the acquisition of conservation by nonretarded children could be accelerated, and was concerned with the possibility that eye movements could reflect such changes and provide a supplemental index of cognitive structural changes. Previously Gelman ( 1969) had demonstrated increases in the conservation behaviors of nonretarded children through training procedures that involved the maximization of attention to task-relevant cues. Such shaping of attentional behavior was considered by Wilton and Boersma also to offer promise for intervention with retarded children since studies had indicated that the retarded progress through Piagetian stages in the same sequence but at a slower rate than nonretarded children and it was considered possible that achieving attentional decentration, i.e., distributing attention across stimulus elements, could be a particularly important source of difficulty for the retarded. To some extent this idea was presaged by Gardner and Long (1962) who found that extensive visual scanners were more accurate in estimating the apparent size of a standard stimulus in a size estimation task and identified this effect with the overcoming of centration effects. Although the subjects in this study were adults it was noted that attention deployment strategies (decentration) evolve during the course of development. In the Wilton and Boersma (1974b) series of studies the Mackworth corneal reflection method was used with eye movements scored in terms of a number of measures. These included number and length of fixations, with a fixation defined

SCANNING AND FIXATION BY THE RETARDED

23

as one or more successive corneal reflections within a circular area subtending by 15 minutes of arc for a minimum of one-tenth of a second; number and length of runs, with runs defined as two or more consecutive fixations exclusively on either the transformed or nontransformed stimulus elements; examination time, computed as the total number of one-tenth second frames on either the transformed or nontransformed elements; and couplings, defined as the shift of the fixation point from one stimulus element to the other. O’Bryan and Boersma (1971) had earlier demonstrated eye movement differences between nonretarded children (CA range 75- 122 months) who were conservers and those who were nonconservers, with conservers being visually decentered in terms of displaying many shifts of fixation, while nonconservers appeared to be distracted in the presence of the transformed stimulus by dominant perceptual cues that were usually irrelevant to a conservation judgment. This study was followed by the Wilton and Boersma (1974b) investigation in which the eye movements of mildly retarded and nonretarded children who were conservers and nonconservers were investigated. In addition to the testing of the subjects on number and length conservation and solid and liquid continuous quantity conservation, a third test series was given in which a number of situations were displayed that presented violations of number or length conservation. The first part of this study (also see Wilton & Boersma, 1974a) which compared the eye movements of nonretarded conservers and nonconservers (mean CA =86.2 and 82.3 months, respectively) replicated the O’Bryan and Boersma (1971) findings of greater perceptual activity on the part of conservers, and also found that this group showed an increase in centrative perceptual activity on the transformed element in response to the conservation violations. The second comparison (also see Boersma & Wilton, 1974) demonstrated that the nonconserving nonretarded children (mean CA = 79.9 months) who were given a training program based on Gelman’s ( 1969)procedures showed different patterns of eye movements as compared to the no-training control subjects (mean CA = 82.32 months), being more active in visual explorations in a manner similar to those of natural conservers. Their eye movements to conservation violations were not as similar to those of natural conservers, however. The final two comparisons involved mildly retarded children tested in the same experimental situation. The first (also see Wilton & Boersma, 1974a) examined eye movement differences between conserving and nonconserving retarded children (mean CA = 123.3 and 116.8 months, mean IQ = 73.9 and 69.1, respectively) while the second (also see Boersma & Wilton, 1976)examined the effects of conservation training on nonconserving retarded children. Conserving and nonconserving retarded children again differed in their eye movements, but the differences were not found on as many measures as was the case with nonretarded children. Also, training effects were found in the training-no-training comparison with the retarded, with the eye movements of trained retarded non-

24

Leonard E . Ross and Susan M . Ross

conservers (mean CA = 119.5 months, mean IQ = 73.53)different than those of nontrained, nonconserving, retarded children (mean CA = 116.8 months, mean IQ = 69.1). Again the effects were not as large as those found in the comparison with the nonretarded, and group differences were not found between the trained and nontrained retarded in eye movements to the conservation violations. In these data the comparisons of eye movement behavior were among the various conserving, nonconserving, and trained nonconserving, groups within the retarded and nonretarded populations rather than directly between these groups. For this reason, and the CA differences (some 37 months on the average) and MA differences that existed between the retarded and nonretarded subjects, the authors concluded that interpretation of the general developmental differences between these groups would be extremely difficult. However, considering these data and previous studies, it was suggested that the eye movement behavior of the retarded and nonretarded is indeed different. It also should be noted that the evaluation of eye movements was generally in terms of a comparison of the number of measures showing a significant difference under one set of conditions as compared to the number found significant under another. Knowledge of the functional meaning or importance of the various aspects of scanning eye movements in such situations obviously has not progressed to the stage where the measures can be weighted appropriately in analyzing such data, which further limits interpretation of these data. The results of the studies do, however, suggest that eye movements could be valuable in helping to analyze the cognitive processes involved in such situations and in assessing how they may be affected by various training procedures.

V.

CONCLUDING COMMENTS

It is clear that the research effort currently directed toward the study of the eye movements of the intellectually handicapped is far from commensurate with the importance of eye movements in both cognitive development and the efficient functioning of the individual in the visual environment. The amelioration of the difficulties of the handicapped that originate in the broad area of scanning and fixation behavior depends not only upon a comparison of their scanning characteristics to those of nonhandicapped individuals, but also upon the explication of fixation behaviors. While training programs to improve fixation or scanning in particular situations may prove helpful, the greatest gains may be delayed until programs can be developed that are based on a thorough understanding of the scanning process and its relationships to cognitive and contextual factors. The recent increase in research activity studying developmental differences in scanning is an encouraging and useful beginning, but even this work has not progressed to any great extent beyond contrasting the scanning characteristics of

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25

children of different ages. Only a few studies have investigated the processes underlying observed scanning differences in terms of the relationships of the scanning behaviors to stimulus characteristics, experiential factors, or the cognitive capabilities of the children. Neither has comprehensive research been directed to the mechanisms and processes involved in the programming and execution of individual eye movements, or sequences of eye movements, in children. For example, there is considerable research concerned with the characteristics of the eye movements of adults in terms of the utilization of stimulus information in the programming of saccades and the modification of such programming upon the receipt of new target information, but this type of research has not been carried out with children. Even if the processes involved in the programming and execution of saccades do not differ qualitatively in children and adults, handicapped children may differ from the nonhandicapped in qualitative ways that have important implications for scanning behavior. Examination of the available literature investigating the eye movements of the handicapped reveals surprisingly little in the way of systematic research concerned with these subjects’ scanning characteristics and the processes that underly them. In only a few studies have eye movements actually been recorded, and the only conclusions that can be supported by the present data are that the intellectually handicapped can show less than optimal fixation behavior under some conditions, and that their scanning behavior is less functionally useful and efficient than that of nonhandicapped comparison subjects. While this certainly agrees with the intuitive assessment of those who have worked with the retarded, as witnessed by the inclusion of scanning modification procedures in training programs for the handicapped, it does not provide a satisfactory empirical or theoretical base to guide effective intervention. Two points need to be stressed in considering the potential of such eye movement research with the handicapped. One is the necessity to have an excellent base of research information from adults and nonhandicapped children. Given the difficulties in carrying out studies with the handicapped it is unlikely that the necessary basic research for a comprehensive understanding of eye movement behavior can be expected to come from work with handicapped individuals. Thus work with the retarded must necessarily start from basic knowledge of developmental changes in eye movement processes and related phenomena. Second, it is obvious that the eye movement characteristics of the handicapped and their effects on performance must be viewed as heterogeneous in nature. Individuals classified as handicapped may or may not have difficulties in a variety of eye movement behaviors, such as the ability to fixate material, maintain that fixation, engage in scanning behavior, or use effective scan patterns in dealing with visual stimuli. Similarly, the mechanisms involved in the programming and execution of saccades or pursuit eye movements may or may not be related to the efficient visual functioning of the handicapped in particular situations. The difficulty of

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Leonard E . Ross and Susan M .Ross

the severely retarded in fixating the important components of a visual task poses a problem quite different from that of the mildly retarded child whose scanning behavior is not quite sufficient for a difficult task at hand. Even with information concerning the eye movement characteristics of the handicapped it may not be possible to modify eye movements effectively in a manner such that the changes are maintained over time and result in transfer to new situations if the cognitive elements that are involved in the programming and execution of eye movements are not sufficient to the task. Thus, knowledge of the relationships between cognitive processes and eye movement behavior must be long-term research goal. There is also the possibility, however, that the manipulation of eye movements through stimulus factors, e.g., by eliciting eye movements in the desired pattern through changes in stimulus attributes or their temporal sequencing, might result in the modification of perceptual or cognitive activities such that there would be a higher probability that long lasting performance changes could occur. While the long held view that improvement in perceptual and cognitive abilities can result from the training of eye movement patterns has been generally discredited, training activities in specific situations such as in the attempts to accelerate conservation behaviors through the use of training that involves eye movements could be effective in modifying the performance level of the child, at least with respect to particular cognitive activities or behaviors. Several areas appear to hold more immediate promise for improving the visual functioning of the handicapped through an examination of eye movements and the factors that effect them. For example, the investigation of the fixation and eye movement behavior of the severely handicapped in typically used learning situations is needed to identify those cases where the use of alternative stimulus arrangements could be most effective in obtaining fixation on the critical task elements. Research has demonstrated that operant procedures can be quite effective in improving fixation behavior, and the development of these techniques, in conjunction with the optimal use of attention eliciting stimuli and the utilization of eye movement information relevant to identifying the problem and assessing the effectiveness of the modification procedures, could lead to a considerable advance in the ability to improve the attending behaviors of the intellectually handicapped. In a smaller manner the scanning behaviors of the retarded might be significantly changed through the manipulation of stimulus configuration factors. Research with nonhandicapped children shows the importance of the stimulus configuration in helping younger children to scan more systematically and suggests that research on the role of contextual factors in the scanning of the retarded could be quite valuable. Further, the success that has been demonstrated in improving the performance of nonretarded children in match-to-sample problems through the use of scanning-strategy training suggests that research along similar

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lines with the retarded could lead to the improvement of the performance of these children in a variety of similar situations. Finally, there are suggestions in the literature that the handicapped may not be able to utilize peripheral information as effectively as can those not handicapped. Certainly there appears to be an important developmental change in this ability, and the identification of such problems might suggest environmental changes to reduce their effects. Research is also needed on the effects of task load difficulty on the ability of the handicapped to function effectively visually. The importance of both basic and applied research on eye movements and the programming and execution processes underlying them is clear. Not only can such research describe the characteristics and functional limits of the eye movement mechanisms of the handicapped, but the information provided can identify the nature of the problem and suggest new approaches to improving eye movement behavior. Research of all types is needed if the full potential of the handicapped individual is not to be unnecessarily limited by visual scanning and fixation problems.

REFERENCES Auk, R. L., Crawford, D. E., & Jeffrey, W. E. Visual scanning strategies of reflective, impulsive, fast-accurate, and slow-inaccurate children on the matching familiar figures test. Child Development. 1972, 43, 1412-1417. Baumeister, A. A., & Ellis, N. R. Delayed response performance of retardates. American Journal of Mental Deficiency, 1963, 67,714-722. Becker, W., & Jiirgens, R. An analysis of the saccadic system by means of double step stimuli. Vision Research, 1979, 19, 967-983. Belmont, J. M.,& Ellis, N. R. Effects of extraneous stimulation upon discrimination learning in normals and retardates. American Journal of Mental Deficiency, 1968, 72, 525-532. Berkson, G. Eye fixation responses of profoundly defective children. American Journal of Mental Deficiency, 1966, 71, 492-500. Bisanz, J., & Resnick, L. B. Changes with age in two components of visual search speed. Journal of Experimental Child Psychology, 1978, 25, 129-142. Boersma, F. J., & Muir. W. Eye movements and information processing in mentally retarded children. Rotterdam: Rotterdam University Press, 1975. Boersma, F. J., & Wilton, K. M.Eye movements and conservation acceleration. Journal ofExperimental Child Psychology, 1914, 17, 49-60, Boersma, F. J., & Wilton, K. M. Eye movements and conservation acceleration in mildly retarded children. American Journal of Mental Deficiency, 1976, 80, 636-643. Cohen, K. M., & Haith, M. M. Peripheral vision: The effects of developmental, perceptual and cognitive factors. Journal of Experimental Child Psychology, 1977, 24, 313-394. Das, J. P. Visual search, stimulus density, and subnormal intelligence. American Journal of Mental Deficiency. 197 I , 76, 357-361. Day, M. C. Developmental trends in visual scanning. In H.Reese (Ed.), Advances in child development and behavior (Vol. 10). New York: Academic Press, 1975. F’p. 153-193. Day, M. C. Visual search by children: The effect of background variation and the use of visual cues. Journal of Experimental Child Psychology, 1978, 25, 1-16.

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Digate, G.. Epstein, M. H.. Cullinan. D., & Switzky. H. N. Modification of impulsivity: Implications for improved efficiency in learning for exceptional children. The Journal of Special Education, 1978, 12, 459-468. Drake, D. M. Perceptual correlates of impulsive and reflective behavior. Developmental Psychology,

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Duckworth, S . V.,Ragland, 0 . G., Sommerfeld. R. E., & Wyne. M. D. Modification of conceptual impulsivity in retarded children. American Journal of Mental Deficiency, 1974,79, 59-63. Egeland. B. Training impulsive children in the use of more efficient scanning techniques. Child Development, 1974.45, 165-171. Ellis, D. Visual handicaps of mentally handicapped people. American Journal of Mental Deficiency, 1979. 83, 497-511. Epstein, M. H.. Hallahan, D. P., & Kauffman. J. M. Implications of the reflectivity-impulsivity dimension for special education. The Journal of Special Education, 1975.9, 11-25. Errickson, E. A., Wyne, M. D.. & Routh, D. K. A response-cost procedure for reduction of impulsive behavior of academically handicapped children. Journal ofAbnorma1 Child Psychology, 1973,1, 350-357. Fisher, D. F.. & Lefton. L. A. Peripheral information extraction: A developmental examination of reading processes. Journal of Experimental Child Psychology. 1976,21, 77-93. Furby, L. Attentional habituation and mental retardation. Human Development. 1974.17, 118-138. Gardner, R. W., & Long, R. 1. Control, defence and centration effect: A study of scanning behavior. British Journal of Psychology, 1%2, 53, 129-140. Gelman, R. Conservation acquisition: A problem of learning to attend to relevant attributes. Journal of Experimental Child Psychology, 1%9, 7, 167-187. Guralnick. M. J. Solving complex discrimination problems: Techniques for the development of problem-solving strategies. American Journal of Mental Deficiency, 1976,81, 18-25. Hochberg. J. Components of literacy: Speculations and exploratory research. In H. Levin & J. P. Williams (Eds.), Basic studies in reading. New York: Basic Books, 1970. Hochberg, J. Toward a speech-plan eye-movement model of reading. In R. A. Monty & J. W. Senders (Eds.), Eye movements and psychological processes. Hillsdale, N.J.:Erlbaum, 1976. Hogg, J.. & Maier, 1. Transfer of operantly conditioned visual fixation in hyperactive severely retarded children. American Journal of Mental Deficiency. 1974,79, 305-310. Holmes, D. L.,Cohen, K. M.,Haith, M. M., & Momson. F. 1. Peripheral visual processing. Perception and Psychophysics. l971,22, 571-577. Jackson, G.M. The use of visual orientation feedback to facilitate attention and task performance. Mental Retardation. 1979. 17, 281-284. Jeffrey, W. E. The orienting reflex and attention in cognitive development. Psychological Review, 1968, 75, 323-334. Kagan, J.. Rosman. B. L., Day, D., Albert, J.. & Phillips, W. Information processing in the child: Significance of analytic and reflective attitudes. Psychological Monographs: General and Applied, 1964,78, Whole No. 578. Keogh, 8 . K. Optometric vision training programs for children with leaming disabilities: Review of issues and research. Journal of Learning Disabilities, 1974.7, 219-233. Kowler, E., & Sperling, G. Transient stimulation does not aid visual search: Implications for the role of saccades. Perception and Psychophysics, 1980,27, 1-10, Kowler, E., & Steinman, R. M. The role of small saccades in counting. Vision Research, 1977,17, 141-146. Krupski, A. Heart rate changes during a fixed reaction time task in normal and retarded adults. Psychophysiology. 1975. 12, 262-267. Krupski, A. Role of attention in the reaction-time performance of mentally retarded adolescents. American Journal of Mental Deficiency, 1977,82, 79-83.

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Krupski, A , , & Boyle, P. R. An observational analysis of children’s behavior during a simplereaction-time task: The role of attention. Child Development, 1978, 49, 340-349. Lakowski, R . , & Aspinall, P. Static perimetry in young children. Vision Research, 1969, 9, 305312. Lefton, L. A. Eye movements in reading disabled children. In J. W. Senders, D. F. Fisher, R. A. Monty (Eds.), Eye movements and the higher psychological processes. Hillsdale, N.J.: Erlbaum, 1978. Lefton, L. A , , & Haber, R. N. Information extraction from different retinal locations. Journal of Experimentol Psychology, 1974, 102, 975-980. Lefton, L. A,, Lahey, B. B., & Stagg, D. 1. Eye movements in reading disabled and normal children: A study of systems and strategies. Journal of Learning D Lowry, P. W., & Ross, L. E. Severely retarded children as impulsive responders: Improved performance with response delay. American Journal of Mental Deficiency, 1975, 80, 133-138. Mackworth, N. H., & Bruner, J. S. How adults and children search and recognize pictures. Human Development, 1970, 13, 149-177. Mackworth, N. H., Grandstaff, N. W., & Ribram, K . H. Orientation to pictorial novelty by speech-disordered children. Neuropsychologia, 1973, 11, 443-450. Maier, I . , & Hogg, J. Operant conditioning of sustained visual fixation in hyperactive severely retarded children. American Journal of Mental Deficiency, 1974, 79, 297-304. Messer, S. B. Reflection-impulsivity: A review. Psychological Bullerin, 1976, 83, 1026-1052. Neisser, V. Cognitive psychology. New York Appleton, 1967. O’Bryan, K. G . , & Boersma. F. 1. Eye movements, perceptual activity, and conservation develop ment. Journal of Experimental Child Psychology, 1971, 12, 157-169. O’Connor, N . , & Berkson, G. Eye movement in normals and defectives. American Journal of Mental Deficiency, 1963,68, 85-90. Quay, H. C., Sprague, R. L., Werry, J . S., & McQueen, M. M. Conditioning visual orientation of conduct problem children in the classroom. Journal of Experimental Child Psychology, 1967,5, 5 12-5 17. Rayner, K. Eye movements in reading and information processing. Psychological Bulletin, 1978, 85, 618-660. Rosenberg, S. Searching behavior in the retarded as a function of stimulus exposure conditions and IQ. American Journal of Mental Deficiency, 1961,65, 749-752. Sen, A,, & Clarke, A. M. Some factors affecting distractibility in the mental retardate. American Journal of Mental Deficiency, 1968, 73, 50-60. Siegelman, E. Reflective and impulsive observing behavior. Child Development, 1969, 40, 12131222. Spitz, H. H. Effects of stimulus information reduction on search time of retarded adolescents and normal children. Journal of Experimental Psychology, 1969, 82, 482-487. Spitz, H. H., & Borland, M. D. Effects of stimulus complexity on visual search performance of normals and educable retardates. American Journal of Mental Deficipnry. 1971, 75, 724-728. Spragins, A. B., Lefton, L. A., & Fisher, D. F. Eye movements while reading and searching spatially transformed text: A developmental examination. Memory and Cognition, 1976, 4, 36-42. Sroufe, L. A. Age changes in cardiac deceleration within a fixed foreperiod reaction-time task An index of attention. Developmental Psychology, 1971.5, 338-343. Sroufe, L. A., Sonies, B. C . , West, W. D., & Wright, F. S. Anticipatory heart rate deceleration and reaction time in children with and without referral for learning disability. Child Development, 1973, 44, 267-272. Strang, H. R. Changing disadvantaged children’s learning tempos through automated techniques. Journal of Genetic Psychology, 1974, 124, 91-98.

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Terdal. L. G. Stimulus satiation and mental retardation. American Journal of Mental Deficiency, 1967, 71, 881-885. Tumure, J. E. Reactions to physical and social distracters by moderatley retarded institutionalized children. The Journal of Special Education, 1970, 4, 283-294. Tumure, J., & Zigler, E. Outer-directedness in the problem solving of normal and retarded children. Journal of Abnormal and Social Psychology, 1964.69, 427-436. Vurpillot, E. The visual world of the child. New York: International Universities Press, 1976. White, S. H.Evidence for a hierarchical arrangement of learning processes. In L. P. Lipsitt & C. C. Spiker (Eds.), Advances in childdevelopment and behavior. New York: Academic Press, 1965. Whiteside, J. A. Peripheral vision in children and adults. Child Development, 1976, 47, 290-293. Wilton, K. M., & Boersma, F. J. Eye movements and conservation development in mildly retarded and nonretarded children. American Journal of Mental Deficiency, 1974, 79, 285-291. (a) Wilton, K . M., & Boersma, F. J. Eye movements, surprise reactions and cognitive development. Rotterdam: Rotterdam University Press, 1974. (b) Winters, J. J., Gerjuoy, I. R., Crown, P., & Gorrell, R. Eye movements and verbal reports in tachistoscopic recognition by normals and retardates. Child Development, 1967, 38, 11931199.

Wright, J. C., & Vlietstra, A. G. The development of selective attention: From perceptual exploration to logical search. In H. W. Reese (Ed.), Advances in childdevelopment and behavior (Vol. 10). New York: Academic Press, 1975. Zelniker, T.,Jeffrey, W. E., Auk, R., & Parsons, J. Analysis and modification of search strategies of impulsive and reflective children on the matching familiar figures test. Child Development, 1972, 43, 321-335.

Visual Pattern Detection and Recognition Memory in Children with Profound Mentall Retardation1 PATRICIA ANN SHEPHERD AND JOSEPH F. FAGAN 111 DEPARTMENT OF PSYCHOLOGY CASE WESTERN RESERVE UNIVERSITY CLEVELAND, OHIO

Introduction . . . . . . . . . . . . A. Objectives . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . B. Population Characteristics ................................... 11. Assessment of Visual Pattern Detection and Recogniti A. Operational Definitions ..................... B. Pattern Detection ........................ C. Pattern Recognition ........................ 111. Assessment of VisuaI P Retarded Child . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . A. Pattern Detection . . . . .. B . Recognition Memory . .. IV. Summary and Discussion.. ....................... ................. References .................................... .................

I.

31

35

42 42 48 54 57

I. INTRODUCTION

A.

Objectives

The purpose of the present article is to show how methods developed to test the visual-perceptual and visual recognition functioning of the normal infant may be employed to explore the visual-perceptual and memory abilities of the pro'Preparation of this article was supported by a Biomedical Award funded through Western Reserve College and Graduate Student Alumni Fund Grants from Case Western Reserve University. 31 INTERNATIONAL REVIEW OF RESEARCH IN MENTAL RETARDATION, Vol. 10

Copyright @ 1981 by Academic Press. IN. All rights of reproduclion in any form reserved. ISBN o - i z - 3 ~ ~ 1 ~ 9

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Patricia Ann Shepherd and Joseph F . Fagan III

foundly retarded child. The first aim is to define what is meant by profound retardation. The next aim is to present the basic measures or operational definitions employed to test the visual perception of normal infants. One such basic measure is the tendency of the infant to devote more fixation to some stimuli than to others. Such naturally occurring visual preferences have been used to study a number of aspects of infant visual perception. Two naturally occurring preferences that have proved particularly useful in the study of infant perception and memory are greater attention to patterned than to plain targets and a tendency to devote more attention to a novel than to a previously seen target. Illustrations are given of how a general preference for patterning has been used to study the development of the infant’s visual acuity. Novelty preferences are considered for the information they have yielded on more subtle types of infant perception and recognition memory. Following a discussion of methods and findings on visual perception and memory in the normal infant, particular illustrations, drawn from our recent work, are given of how methods developed with normal infants may be used to assess visual perception and memory in the profoundly retarded child. The summary begins with estimates of the retarded child’s ability to detect patterns. The focus then shifts to a demonstration of more subtle types of pattern perception and recognition memory on the part of retarded children. The final section of the article includes a general discussion of practical implications. 8. Population Characteristics

The American Association on Mental Deficiency classification of profound mental retardation includes those persons with Intelligence Quotient scores that are more than five standard deviations below the mean intelligence scores of the general population. Additionally, the profoundly mentally retarded often have other handicaps and require total care for life. Many of the profoundly retarded do not acquire useful speech. As adults, they typically have mental ages of approximately 2-2% years. For the most part, the profoundly retarded require constant care just to survive. They are typically not ambulatory, although they may eventually acquire some self-directed ambulation, and their self-help skills are poor. The etiologies of their various physical and intellectual handicaps may result from physical trauma, infection, chromosome or metabolic disorder, or from a variety of unknown prenatal disorders. The reality is that people with a diagnosis of profound mental retardation frequently cannot be tested on standard intelligence tests due to physical limitations or to behavior not conducive to valid testing (e.g., high rates of motor activity or inattentionj. Investigators in the area of mental retardation, confronted with the problem of subject description for research purposes, have met the difficulty of testability in various ways. Some have used the American Association on Mental Deficiency definition of profound mental retardation adding behavioral information to classify the indi-

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viduals studied (e.g.. Decker & Wilson, 1977), while others have used a combination of chronological age with mental ages measured by available infant tests of sensory-motor development such as the Bayley Scales (e.g., Butcher, 1977). In the present chapter, the profoundly mentally retarded children studied had chronological ages of 12 years or less and mental ages of less than 1 year (as estimated on scales of infant sensory-motor development).

II. ASSESSMENT OF VISUAL PAllERN DETECTION AND RECOGNITION MEMORY IN THE INFANT The first aim of the present section is to present basic operational definitions of infant visual perception. The measure we emphasize is the tendency of the infant to devote more fixation to some stimuli than to others. Following a discussion of measures of infant visual perception, particular illustrations of the early development of pattern detection and discrimination are presented. Our summary includes estimates of the infant’s ability to detect patterns. The focus of the review then shifts to a consideration of visual recognition memory in the infant. Our major point is that the observation of the infant’s visual behavior, especially the infant’s attentional preferences, has made it possible to observe what information the infant is capable of detecting and of encoding at various ages and under various presentation conditions. Much of the material in the present section is based on recent and extensive reviews of infant visual perception and infant recognition memory by Fagan and Shepherd (1979) and Fagan (in press), respectively.

A.

Operational Definitions

The major techniques currently used to assess the visual capabilities of infants include the elicitation of optokinetic nystagmus, the measurement of visualevoked potentials, and the study of the infant’s visual interest. Optokinetic nystagmus refers to a series of reflexive and involuntary eye movements which begin with a fixation phase while the eye follows an object moving laterally across the visual field and ends with a faster phase in which the eye moves in the opposite direction after following the object as far as possible. The elicitation of the optokinetic response is simple to effect in infancy and has been used to study the infant’s binocular fixation, convergence, conjugate eye movements, and level of visual acuity. The chief advantage of the procedure is that it is relatively simple to use and inexpensive. A major disadvantage, however, is that the elicitation of optokinetic nystagmus limits the investigator to the study of pattern detection, since the response does not readily lend itself to the study of discrimination among patterns.

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Patricia Ann Shepherd and Joseph F. Fagan 111

A change in the pattern of electrical activity in the infant’s brain in response to a visual stimulus may be recorded by attaching electrodes to the infant’s scalp over the area of the visual cortex and then allowing the infant to observe various visual patterns. The electrical signals from the brain of the attentive infant are recorded, amplified, summed, and averaged to form an encephalogram. The study of such visual-evoked potentials has been used to estimate infant visual acuity. The advantage of this technique is that it is a direct measure of neural activity which requires no overt behavioral response. The disadvantage is the reliance on complicated, expensive equipment for recording brain activity and the necessity for skilled technicians and sophisticated statistical techniques in order to reduce and interpret data. The most often employed technique for the study of infant visual perception is the infant visual interest test developed by Fantz (1956). The assumption underlying the test is that if an infant looks more at one stimulus than another the infant must be able to differentiate between the two targets. The procedure for determining an infant’s visual fixation is simple. Typically, the infant is placed in front of a stage on which a pair of targets are secured. An observer, looking through a peephole centered between the targets, observes the corneal reflection of a target over the pupils of the infants eyes and records the length of fixation time paid to each stimulus. Differential visual fixation is operationally defined when one of a pair of targets elicits significantly more than 50% of the infant’s total fixation time. The visual interest test is inexpensive and simple to use either in a lab setting or in the infant’s home and has been the most commonly used method of studying the infant’s visual perception. By finding which targets infants prefer to look at, basic questions concerning infant visual abilities can be answered. Fantz, Ordy, and Udelf (1962), for example, relied on the strong and consistent preference demonstrated by infants for patterned over plain targets to gain estimates of infant visual acuity. Fantz et al. paired patterns of black and white stripes of various widths with plain grey targets of equal brightness. Since infants prefer patterned to plain stimuli, the assumption was that stripes would be preferred to solid gray targets as long as the stripes were resolvable. The finest width of stripes preferred to gray was taken to indicate the infant’s level of acuity. While issues of infant acuity will be explored more fully below, we simply wish to note that the reliance on the infant’s basic visual preference for patterned targets allows the study of acuity. Investigators have also taken advantage of naturally occurring visual preferences to solve problems posed by the fact that infants sometimes prefer to look at one stimulus as much as another. Lack of differential fixation when a choice between two stimuli is available may imply either an inability of discrimination or the equal attention value of stimuli which are actually discriminable. The solution of the problem of equal fixation among a set of stimuli is to rely on a known visual preference to increase the salience of one of the members of a target pair. For

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example, one means employed by researchers to test the infant’s ability to discriminate between two targets which elicit equal attention is to pair the targets following exposure to one of them. It is a well-documented finding that, after exposure to a target, infants will attend predominantly to a novel stimulus. Preference for a novel over a previously exposed target demonstrates that the two targets are discriminable and, further, indicates that the infant can recognize or identify one of the targets as familiar. As we shall see, the infant’s preference for visual novelty has provided a valuable tool for the study of infant visual recognition memory.

B. Pattern Detection Infants, from birth, exhibit pattern detection by selecting patterned stimuli for visual inspection more often than unpatterned stimuli. Neonates also evidence pattern discrimination by making consistent attentional choices among patterned stimuli. In the present section, we note factors which influence the measurement of the infant’s threshold for visual pattern detection. We then list basic visual dimensions to which infants are known to attend in discriminating among patterns. Visual acuity refers to the threshold value for detection of pattern detail. Recent reviews by Harter, Deaton, and Odom (1977), Dobson and Teller (1978), and Salapatek and Banks (1978) contain a detailed exposition of studies of infant visual acuity. These reviews list a number of variables affecting acuity estimates. But despite the presence of mitigating variables, it is possible to identify trends in the early development of pattern detection and to give ranges for estimates of infant acuity at various ages. Investigators agree that acuity develops rapidly from birth to 6 months with a slower rate of improvement to 1 year. Estimates (in Snellen equivalents) range from 20/800 to 20/200 at birth, from 20/160 to 20/20 (adult acuity) at 6 months, and 20/66 to 20/20 by 1 year. In more operational terms, one can assume that the average infant, at birth, is able to detect the pattern contained in a set of 1/8”black and white stripes held about 9 in. from his eyes and, by 6 months, can see at a distance of 12 in. the detail produced by 1/64” stripes. We have chosen to express our estimates of infant visual acuity in terms of ranges and to give operational definitions of what patterns are resolvable because it is not possible to give absolute threshold values for infant pattern detection. The fact is that estimates of infant visual acuity vary according to the kind of acuity measured, the response observed, and the type of pattern detected. Tests in which the detection of the finest single line on a blank field is estimated, for example, yield lower thresholds for both infants and adults than estimates based on the finest width of black and white stripes preferred to a plain gray field (Fantz, Fagan, & Miranda, 1975). In addition, estimates of acuity based on the recording of visual evoked potentials typically yield somewhat lower thresholds

36

Patricia Ann Shepherd and Joseph F . Fagan I l l

than those based on optokinetic nystagmus or preferential fixation (Harter et al., 1977). Finally, infants are better able to detect a curved line than a straight line (Fantz et a f . , 1975) and, like adults, there is some evidence that infants are better able to resolve horizontal or vertical stripes than oblique stripes (Leehey, Moskowitz-Cook, Brill, & Held, 1975). Hence, there is a practical need for some methodological or conceptual advance which would allow a more accurate measure of pattern detection, a measure which would remain invariant across various stimulus and response conditions. But in addition to the practical concern of assessing acuity per se, more accurate knowledge of the detectability of visual patterns may also be necessary to provide a more complete explanation of infants’ preferences among patterns during the early months of life. Infants, from the first few days of life, are not only able to detect the presence of pattern but are also able to discriminate among patterns (Fantz, 1963; Hershenson, 1964; Stechler, 1964). The fact that some patterns attract more of the newborn’s attention than others has led investigators to ask what specific differences between patterns may mediate these preferences. Miranda and Fantz (1971), for example, discovered that variations in the size or number of elements from one pattern to another could determine pattern preferences. In the Miranda and Fantz study the total times that newborns spent looking at each of the nine patterns which varied in size and number of details in the pattern showed that, where number of elements were the same, newborns preferred larger to smaller elements. When patterns contained equal sized elements, attention was given to patterns with more elements. A further study by the same investigators (Fantz & Miranda, 1975) demonstrated that newborns are also sensitive to differences in form. Fantz and Miranda employed four pairs of forms where the members of each pair were equated for total contour length, brightness, and number of elements. The targets differed in form with one member of each pair being curved and the other being straight. The curved member of three of the four pairings elicited significantly more fixation than the target with the straight contour. In addition to these initial perceptual distinctions, on the basis of size, number, and form, investigators frequently note what appear to be attentional shifts in preferred dimensions over age. Fantz and Fagan (1973, for example, noted that relatively greater attention is paid to number than to size of elements after 10 weeks of age. In fact, much of the theoretical activity in the area of infant visual perception has focused on attempts to explain early visual preferences and shifts in preferences over age on the basis of some single underlying dimension such as “complexity” (e.g., Brennan, Ames, & Moore, 1966) or “amount of contour” (Karmel, 1969). Unfortunately, the task of explaining shifts in visual preferences over age as due to attentional shifts along some basic dimension is complicated by the fact that what appear to be shifts in perceptual preferences may actually reflect maturational changes in sensory-motor functioning. Changing preferences

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for patterns which vary in size, number, or contour density may, in part, be a function of how resolvable a pattern is from age to age. In other words, what appear to be age-related shifts in attention to dimensions may actually be due to growth in acuity. Hence, to aid understanding of early pattern perception and to give a more accurate estimate of absolute thresholds which hold across variations in methods and in stimuli there is a need for more sophisticated assessments of visual acuity in the infant. One promising solution to the problem of obtaining more accurate threshold values for infant acuity appears to lie in the measurement of infant acuity via contrast sensitivity functions. An exposition of the merits of plotting contrast sensitivity functions for infants is contained in articles by Salapatek and Banks (1978) and Banks and Salapatek (in press). Briefly, an infant’s contrast sensitivity is found, in the usual manner, by presenting the infant with test patterns composed of light and dark stripes paired with plain targets of equal brightness. The pattern targets, however, vary not only in width of stripes but in the brightness contrast between the stripes. In other words, various shades of gray are employed to create a striped pattern at each stripe width and the question becomes, what is the smallest discernible difference in brightness given a particular stripe width? Contrast sensitivity functions are plotted as a function of threshold contrast sensitivity at various stripe widths and acuity is estimated by extrapolation. For our present purposes it is important to note that thresholds of pattern detection derived from contrast sensitivity functions are somewhat lower for both infants and adults than are those derived solely from visual discriminations of high contrast (black-white) patterns. These lower thresholds are to be expected since the differences in stripe separation are more easily detected in patterns containing intermediate light-dark contrast than in those with very high or very low contrast. Hence, one may obtain accurate and lower threshold estimates of acuity as well as some measure of sensitivity to contrast by showing targets which vary in brightness contrast as well as in stripe width. But the value of plotting contrast sensitivity functions for obtaining more accurate estimates of acuity gains its real power in interaction with the fact that it is also possible, by the application of Fourier’s theorem and linear systems analysis, to describe patterns in terms of their internal spatial frequencies and brightness contrasts. In effect, then, if we know the infant’s contrast sensitivity function and one can obtain sophisticated descriptions of the pattern one can, in theory, predict the visibility or detectability of that pattern for the infant. In other words, it may be possible to predict which patterns may be above or below threshold for detection for infants at various ages. It is also possible, in theory, to equate different patterns for detectability and to note the extent to which the targets then elicit differential fixation. In short, the combination of accurate acuity estimates and sophisticated pattern description promises to reconcile diversities among studies of infant acuity which vary in the kind of acuity estimated

38

Patricia Ann Shepherd and Joseph F . Fagan 111

and the type of stimulus shown. Such an approach may also aid our understanding of the neonate’s preferences among visual patterns. Successful attempts at such reconciliation are given detailed exposition in a recent study by Banks and Salapatek (in press).

C. Pattern Recognition Infants are not only able to detect patterns but can also recognize previously seen patterns. The present section on infant pattern recognition has four aims. The first is to provide a brief summary of methods employed to test infant visual recognition. The second is to point out the main findings from studies of infant recognition memory. More detailed reviews of infant memory are readily available (Olson, 1976; Werner & Perlmutter, 1979; Fagan, in press). The thiid aim is to provide specific illustrations of how tests of visual recognition may be arranged in order to infer what information the infant has encoded from study of a target. The final goal is to present a brief discussion of recent evidence indicating a link between infant recognition memory and later intelligence. The major techniques currently used to assess the visual recognition capabilities of infants are based on the assumption that recognition memory is indicated by differential responsiveness to a novel and a previously exposed stimulus. Two paradigms directly measure the infant’s visual interest. The third is an indirect estimate of visual interest, measuring instead, the infant’s rate of sucking where visual stimulation is dependent upon a high sucking rate. In one procedure which measures visual interest (e.g., Caron & Caron, 1968) the same stimulus is repeatedly presented and then a new stimulus is introduced. Typically the infant’s response to the repeatedly exposed target declines over trials but returns to its initial level when a novel target is shown. A second procedure (e.g., Fantz, 1964; Fagan, 1970) based on visual interest is to expose the infant to a target for a certain period of study and then to present him with the recently exposed and a novel target simultaneously. Infants typically devote the greater part of their fixation to the novel target when faced with such a pairedcomparison. Delayed recognition memory is tested by varying the time that elapses between the end of study and the test pairing. In the third paradigm (Siqueland & Delucia, 1969), a visual stimulus is brought into focus as a reinforcement for high amplitude sucking. As the infant’s sucking rate declines with repetition of the target and reaches some criterion of habituation, a new target is introduced. If the sucking response increases upon presentation of the novel target, recognition is inferred. One main finding to emerge from the study of infant recognition memory is that recognition may be demonstrated at any age during infancy depending upon the discriminability of the previously exposed and novel targets with which the infant is faced. Generally, targets differing along many dimensions are dif-

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MEMORY, AND PROFOUND RETARDATION

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ferentiated on a recognition test at an earlier age than are pairs of stimuli with fewer between-target differences. Thus, memory for easily scannable targets varying along a variety of dimensions is demonstrable during the first month of life (Friedman, 1972; Friedman, Bruno, & Vietze, 1974; Milewski & Siqueland, 1975; Milewski, 1978; Werner & Siqueland, 1978). Stimuli differing only in orientation, form, or patterning, however, may not be differentiated on a recognition test until about the third or fourth month (e.g., Fantz et al., 1975). Even more difficult are subtle pattern distinctions such as between achromatic photos of two unfamiliar faces, distinctions made at 5 to 7 months (Fagan, 1979). A second point is that recognition does not require lengthy study time. An experiment by Fagan (1974), for example, asked whether brief amounts of exposure would be effective in allowing recognition on the part of 5-month-olds. A related question was whether longer study was necessary for more difficult discriminations. Among the tasks included in the Fagan (1974) study were discriminations among abstract stimuli varying along a number of dimensions, among abstract targets varying only in pattern arrangement, and among photos of faces. The amount of study time necessary to elicit a novelty preference on recognition testing varied from task to task. As little as 3 to 4 seconds of study time were needed to differentiate a novel from a previously seen target when the targets varied widely. A similar level of novelty preference was not reached for pairs of targets differing solely in patterning until 17 seconds of study time had passed. Distinctions among faces required 20 to 30 seconds of prior study. Similar findings for infants with regard to the efficacy of brief study times and the interaction of study time with target discriminability have been reported by Bornstein (1976), Fagan (1977a), Olson (1979), and Lasky (1980). The third and final main finding is that infant recognition memory, at least by 5 months, is robust, i.e., it is long-lasting and not easily disrupted. Some indirect support for the existence of retention of information gained from exposure to abstract patterns on the part of 5-month-old infants over a period of 24 to 48 hours was provided in a study by Fagan (1970, Experiment I). A direct test of long-term memory for abstract patterns was made in a study by Fagan (1973) in which infants 5 to 6 months of age recognized, after as long as 2 days, which member of a pair of targets had been seen, even when the stimuli differed only in patterning. A second experiment in the Fagan (1973) study tested the 5month-old infants’ delayed recognition for photos of faces at intervals of 3 hours, 1, 2, 7, or 14 days. Long-term retention of the information conveyed by a face photo was demonstrated at each interval. Confirmation of the main findings from the Fagan studies (1970, 1973) has been provided by other investigators. Martin (1975) and Strauss and Cohen (1980) demonstrated 24-hour retention of the information conveyed in abstract forms on the part of 5-month-olds. Infants at 5 to 6 months, in a study by Cornell (1979), showed 48-hour memory for abstract patterns and face photos. Finally, 1 to 2 week retention for abstract patterns at 7

40

Patricia Ann Shepherd and Joseph F . Fagan III

months has been reported by Topinka and Steinberg (1978). Moreover, such long-term memory is not easily disrupted. A series of experiments by Fagan (1977b) sought to induce forgetting by providing the 5-month-old infant with interference from other targets following initial study of a to-be-remembered stimulus. The general results of the Fagan (1977b) experiments were that highly similar intervening targets could, if presented soon after study, lead to loss of recognition. The deleterious effects of such intervention were quite limited, however. Recovery of recognition occurred after a 1 minute rest and memory loss was easily prevented by further, brief exposure to the previously studied target. In short, the Fagan (1977b) results indicate that any amnesic effect in infant memory could either be prevented or shown to be short-lived. Similar findings with regard to the infant’s resistance to interference have been reported by McCall, Kennedy, and Dodds (1977) and by Cohen, Deloache, and Pearl (1977). The third aim in our discussion of infant recognition memory is to note that conditions may be arranged to discover what specific information the infant has encoded during study of a target. As an example, in a study by Fagan (1977a) on the 5 month infant’s memory for form and color, the procedure was to expose the infant to a target for a brief study period and then to present him with a recognition test, pairing the recently exposed stimulus with a novel one. By controlling the manner in which the novel and previously exposed target varied, some inference was made as to which characteristics of a stimulus were encoded during study to serve as the basis of the infant’s response on recognition testing. By further manipulation of the amount of study time allowed prior to recognition testing the order in which particular aspects of the stimulus were encoded was inferred. Specifically, the infants were allowed to study (for various periods of time) a form-color compound and then were presented with a pair of targets with a familiar and a novel cue along one dimension and the same two novel cues along the other. To test whether color alone could serve as a basis for recognition, for example, the infant might study a red diamond and then be tested on the pairing red square vs green square. In this example, the only dimension containing a familiar and novel cue is color. Attention to form during study would provide no basis for differential fixation. Hence, a reliable preference for the novel color, green in this example, would indicate that color had been encoded during study. Fagan (1977a) found that infants were able to encode either form or color information as a basis for later recognition. Further, given the forms and colors employed, it appeared that color information was encoded prior to form information, i.e., problems in which novelty depended on color differences required less study time prior to recognition than problems in which only form was varied. Other experiments in which infants have demonstrated that they are able to detect features of an abstract stimulus which have remained invariant from study to test include those of McGurk (1972) and Cornell (1975) in which

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infants between 4 and 6 months recognized a pattern even though its orientation had been changed. In addition, the infant’s ability to recognize invariant features of a pattern is not confined to abstract figures. A study by Fagan (1976), for example, showed that 7-month infants recognized a photo of a man as familiar on recognition testing even though that man appeared in a different pose during study. While additional examples might be given of the kinds of information that infants encode, the point is simply that there exist procedures which allow us to make inferences as to what information the infant has taken in during study of a complex visual stimulus. The final point we wish to make with regard to infant recognition memory is that the infant’s recognition ability as measured by visual preferences for novel targets appears to be related to later cognitive functioning. Specifically, samples of infants likely to differ in measured intelligence later in life (e.g., Down’s Syndrome and normal infants) also differ, as infants, in their ability to recognize familiar visual patterns (Miranda & Fantz, 1974). Presumably, such group differences early in life indicate differences in visual recognition memory and in cognitive functioning among individual infants. Recent work by Fagan has been aimed at estimating the predictive validity of tests of infant visual recognition memory as measures of intelligence. Preliminary results have been encouraging. A study by Fagan and McGrath (in press) reports that differences in visual fixation to novel visual patterns on the part of children initially tested from 4 to 7 months of age are reliably correlated (about .50) with later intelligence between 4 and 7 years, i.e., with performance on vocabulary tests and vocabulary subtests of standard intelligence tests. In short, there is support for the assumption that variations in early visual memory predict variations in intellectual functioning. In summary, we have seen that the assessment of visual pattern detection and recognition in the infant rests on the fact that the infant has a tendency to devote more visual fixation to some stimuli than to others. By discovering which stimuli infants prefer to look at and by taking advantage of certain naturally occurring preferences, a beginning has been made in describing the visual world of the infant. We have also seen that such description is possible for various levels of infant visual functioning: from basic visual pattern detection to instances of memory and cognition. Finally, we have touched on the possibility that basic research on infant visual perception and recognition may lead to the development of clinical tools for the measurement of individual differences in functions as disparate as acuity and intelligence. The remainder of the present article explores the notion that tests of vision and visual memory which have proved successful in informing us about the perceptual-cognitive world of one population of nonverbal, low-mental age (by definition) people, i.e., normal infants, may also be profitably employed in measuring perceptual-cognitive functioning in other low-mental age groups for whom nonverbal tests are required, such as the profoundly retarded.

Patricia Ann Shepherd and Joseph F . Fagan Ill

42

111. ASSESSM~ENTOF VISUAL PAITERN DETECTION AND RECOGNITION MEMORY IN THE PROFOUNDLY RETARDED CHILD In the present section, we will focus on recent studies by Butcher (1977), by Switzky, Woolsey-Hill, and Quoss (1979) and, in greater detail, by Shepherd and Fagan (1979, 1980). In those studies, the visual interest test, developed for the study of infant visual perception and memory, was adapted for use with profoundly retarded children. Specifically, we will begin by focusing on a study by Shepherd and Fagan (1979) in which institutionalized profoundly retarded children were given a series of visual choices between plain and patterned targets in order to identify subpopulationsof the children with regard to the presence and extent of pattern vision. We then turn our attention to studies by Butcher (1977), Switzky et al. (1979), and Shepherd and Fagan (1980) which explored visual pattern recognition on the part of profoundly retarded children. A.

Pattern Detection

The limited behavioral repertoire of profoundly retarded children presents a major obstacle to the assessment of their visual abilities. Thus, a recent review by Berkson and Landesman-Dwyer ( 1977) found that formal assessments of the visual capabilities of the profoundly retarded have been rare. In two studies in 1966, Berkson examined the eye fixations of profoundly defective children when moving or stationary stimuli were presented. He found that the children responded to movement, with response to onset of movement greater than response to offset. A number of studies of the visual behavior of deaf-blind rubella syndrome children who were also profoundly retarded have been reported by Friedlander and his associates. Rynders and Friedlander ( 1972) required children to press a panel in order to view a color motion picture of an attendant-child caretaking interaction, a series of black and white slides of the same interaction, or a black and white slide projected out-of-focus and designated “neutral. They found a significant and consistent preference for the color motion picture, although it could not be determined whether this was due to variations in brightness, color, motion, or to other differences among the stimuli. In further attempts to identify the stimulus basis for such preference, Friedlander and Knight (1973), who also required children to press a panel, evaluated light sensitivity for deafblind children. All the children studied by Friedlander and Knight could see down to 5 fc of intensity and many preferred one light intensity over another. In yet another study of preferences for more or less resolvable targets, Friedlander, Silva, and Knight (1974) found that some children, in a lever-pressing situation, could discriminate in-focus from out-of-focus black and white linear ”

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displays. Finally, in accord with Berkson (1966), Silva, Knight, and Friedlander (1973) found gross tracking ability in most of their sample of deaf-blind children. With regard to color as a basis for choice, Wallstein and Hesse (1975) studied color vision in deaf-blind children and found that two out of three subjects could learn a discrimination between red and green. Thus, a picture emerges of the general visual capabilities of at least some profoundly retarded children. They exhibit an orienting response to moving or stationary stimuli and continue to fixate a target over several minutes. They show a sensitivity to light intensity down to 5 fc and can track some stimuli, differentiate in-focus from out-of-focus pictures, and can discriminate among certain colors. All but one study of visual functioning of profoundly retarded children (Berkson, 1966) reviewed above required the children to be able to press a panel or lever. Unfortunately, most profoundly retarded children are much too handicapped to perform even so simple a response as pressing. As we have noted throughout the present chapter, however, the preferential looking paradigm developed for assessing infant visual abilities may be useful for even the most handicapped subjects, since it requires only the ability to direct one’s gaze. Let us now consider a recent study by Shepherd and Fagan (1979) in which the visual interest test was used to test visual pattern detection abilities on the part of profoundly retarded children. The Shepherd and Fagan (1979) sample included 47 profoundly retarded children with a mean chronological age of 6 years (SD 2.71 years). The retarded children resided in a private institution. The mean Bayley age of the children was about 4 months (SD 2.18 months). Two series of targets were employed. One series of targets was composed of high contrast stripes (70% contrast between darkest and lightest points). The stripes were either 1/2, 1/4, 1/8, 1/16, or 1/32 of an inch wide. The final target in the first series was a plain gray square equal in brightness to the stripes. Presenting this series of graded stripes allowed developmental comparison of normal infants with profoundly retarded children on a conventional measure of minimum separable acuity. A second series, which contained more subtle visual contrasts (5% contrast between darkest and lightest points) than the stripes, consisted of representations of faces. The face targets varied in clarity of internal detail from plain (no visible features, just an outline of the head) to clearly visible face features. This second series (faces) was employed because normal infants are well able to distinguish one face photograph from another even though the faces are judged by adults as highly similar in physical features (Fagan & Singer, 1979). Such distinctions would seem to require a more developed acuity than would distinctions among black and white stripes. Practically, use of the faces in the Shepherd and Fagan (1979) study gave a second estimate, along with the stripes, of the presence and extent of pattern vision for each child. In addition, faces represent a class of ecologically valid patterns. The retarded children in the Shepherd and Fagan experiment received 14

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Putriciu Ann Shepherd und Joseph F . Fugun III

pairings of patterned with plain stimuli and their looking time to both pattern and plain was recorded. For each pairing of pattern and plain, a percentage fixation score for the patterned stimulus was obtained by dividing the total fixation time given the patterned stimulus by the total fixation time for both the patterned and the plain stimuli. Thus, for each child there were fourteen scores, nine pattern preferences for the face series, and five pattern preferences for the stripe series. Mean pattern preference scores were then obtained separately for each child’s face and stripe series. To determine if mean pattern preference scores were greater than a chance level of 50%, t values were obtained separately for each child’s mean pattern preference for face patterns and mean preference for stripes. On the basis of these mean pattern preference scores for individuals, the retarded children were divided into three distinct groups. The 47 retarded children were initially divided according to thier mean pattern preference score for stripes into those children who had preferences greater than chance and those who did not. A total of 32 children who could resolve stripes were then further separated on the basis of their mean face preference scores. Only nine children of the 32 who had statistically significant preferences for stripes also differentiated faces from plain targets. The remaining 23 of the 3 2 who could resolve stripes gave no evidence of seeing the faces. Of those 23 who were not able to resolve the facial pattern, seven would not even fixate the face stimuli. As noted above, 15 children gave no evidence of seeing even the stripes. None of those 15 showed any ability to perceive the faces, including five who would not fixate when the faces were presented. Thus there emerges from this analysis of pattern preferences for individuals three groups of profoundly retarded children. A group of nine children who were able to resolve both high-contrast (stripes) and low-contrast (faces) patterns. A second group of 23 children perceived the stripes but not the faces. A final group of 15 children included those individuals whose mean pattern preference scores for neither stripes nor faces were greater than chance. These three groups of retarded children provided Shepherd and Fagan with the basis for a second analysis which focused on the mean preference scores for each of the 14 pairings of patterned with plain stimuli, means derived for the children in each of the three groups. Figure 1 presents the various face and striped patterns along with the mean percentage fixation to each pattern for the three samples of retarded children (labeled R1, R2, R 3 in Fig. l ) grouped as to their individual ability to resolve patterns. Figure 1 also lists the mean percentage of total fixation devoted to faces by 41 normal 7-month infants (column labeled N) also tested by Shepherd and Fagan (1979). Specifically, to the left in Fig. 1, the various face patterns are pictured. Immediately to the right of the faces, under the heading N, are the mean preferences for pattern for each face exhibited by the normal 7-month infants. As one can see, the infants reliably chose pattern over plain in every instance. In the next column ( R l ) are the mean preferences for pattern for each face stimulus yielded by the group of nine retarded children who, as indi-

45

VISION, MEMORY, A N D PROFOUND RETARDATION GROUPS

R1

R2

70'

72.

49

513'

ai**

76**

52

51

64.

71**

59*

50

70**

67'

61"

56

67*

74*'

52

45

72"

70"

51

56

74**

7a*

58

53

75"

73.'

57

46

76'

72"

46

43

FACES

GROUPS STRIPES

R1

RS

R3

85''

84**

66'*

a3**

ai**

70"

FIG. 1. Mean percentage of fixation to patterned stimuli (faces or stripes) by normal (N) and profoundly retarded children (RI,R2, and R3). *, p < .05; **, p < .01. (From Shepherd & Fagan, 1979.)

viduals, had chosen pattern over plain for the face series. As a group, the nine retarded children behaved very much like the normal 7-month infants, i.e., for each face pattern they showed a highly reliable preference for patterning. In fact, the mean preference for pattern over the nine pairings of face with plain targets was virtually identical for the 7-month normal infants and the nine retarded children in Group R1 at 72.1 and 72.6, respectively. The next two columns in Fig. 1 labeled R2 and R3 contain the face pattern preferences for those 38 retarded children (23 in Group R2 and 15 in Group R3) who, as individuals, had not reliably chosen face patterns over plain control targets. As groups, they did not choose pattern to plain with three exceptions out of 18, a number that might

46

Patricia Ann Shepherd and Joseph F . Fagan III

be expected by chance. The mean preferences over the nine pairings of face patterns with plain control targets for the 23 children in Group R2 and the 15 children in Group R3 were indistinguishable from each other or from a chance value of 50% at 53.9 and 50.8, respectively. On the right side of Fig. 1 , the mean preferences for pattern over plain for the retarded children in Groups R1, R2, and R3 are presented for each of the five pairings of stripes with gray. In Fig. 1, the stripes are arranged in descending order of ease of detection from 1/2" at the top through 1/4, 1/8, and 1/16 to 1/32 of an inch wide at the bottom of the column. Mean preferences listed under the headings R1 and R2 are for those 32 retarded children who, as individuals, chose pattern over plain for the stripe series. These 32 children included the nine who were able to resolve the pattern contained in faces (RI) and the 23 who gave no evidence of seeing the face patterns. Together, children in Groups R1 and R2 were able to reliably resolve even the narrowest width of stripes (1/32"). Groups Rl and R2, who differed in their ability to perceive faces, showed slightly similar overall preferences for the five striped patterns at 82.4 and 78.8, respectively. Finally, the last column of mean preferences for patterning when stripes were shown is for that group of 15 children (R3) who, as individuals, had not reliably chosen pattern over plain when shown either the faces or the stripes. As a group, however, these 15 children did devote more fixation to pattern than to plain when stripes of either 1/2" or 1/4" were employed, indicating some minimal ability to resolve high contrast patterns. Shepherd and Fagan (1979) performed subsidiary analyses to see if variables other than pattern detection ability might also distinguish among the retarded children in Groups R1, R2, and R3. No obvious differences in diagnostic category (e.g., trauma, infection, unknown prenatal cause, metabolic disorders) were apparent across groups. In addition, no differences were found among the groups on psychomotor age or chronological age. However, for Bayley mental age a reliable difference was found due to higher mean Bayley mental age for Group R1 (6.16 months, SD 2.83 months). The mean Bayley mental age for Groups R2 and R3 was 2.79 months (SD 1.42 months). The higher Bayley mental age for Group R1 is not surprising given the large number of items on the Bayley for the first 6 months which require the ability to resolve visual detail (e.g., regard of the red ring, regard of persons, horizontal and vertical tracking of red ring and light, regard of cubes, looking for fallen spoon). In effect, Shepherd and Fagan felt that the Bayley mental age scores confirmed the superior visual abilities of the nine children in Group R1 as measured by their visual pattern preferences. Finally, the test-retest and interobserver reliability was explored in the Shepherd and Fagan (1979) study by having 12 of the retarded children retested by an observer with no knowledge of how each child had performed on his first testing. The 12 children retested included four from Group R1, four from Group

47

VISION, MEMORY, AND PROFOUND RETARDATION

R 2 , and four from Group R3. Table I presents the mean of the original pattern preferences obtained by the first observer (0,) and the mean of the comparable As one can see, the means retest scores obtained by the second observer (02). obtained by the two observers are virtually identical. Table I also lists the mean and standard deviation for the absolute differences (i.e., without regard to sign) in percentage fixation to pattern over the 20 scores obtained by each observer. This rather stringent test of agreement between observers or between tests was also satisfactory with a mean difference of only 6.90 percentage points from one test to the next (SD 6.08). Also given in Table I is the Pearson product-moment correlation over the mean scores for the two observers. The correlation may be taken to indicate the extent of agreement between observers or as an estimate of the test-retest reliability of the pattern vision test, per se. In either case, the observed correlation of .84 was both high and statistically significant (p < .01). In summary, the Shepherd and Fagan (1979) study explored the ability of profoundly retarded children to resolve visual patterning. The visual interest test, developed for the study of infant visual perception, was adapted for use with the retarded children. Profoundly retarded children viewed several pairings of patterned and plain stimuli. Some of the patterns were high contrast (black and white stripes) while others were low contrast (faces). The test was conducted by pairing patterns with plain stimuli and recording the time spent viewing each. Three groups of profoundly retarded children were identified who were more or less able to resolve visual patterns. A small minority of the children (9 out of 47, or 19%) could resolve visual patterning at about the level of a normal 7month-old infant, i.e., they perceived both faces and stripes. Another 49% (23 children out of 47) gave evidence of pattern perception that fell somewhere

TABLE I AGREEMENT BETWEEN MEAN PERCENTAGE OF FIXATION TO PATTERNED STIMULI RECORDEDBY Two INDEPENDENT OBSERVERS (0,AND 0,) IN OBSERVING THE SAME PROFOUNDLY RETARDED CHILDREN~**

-

X SD N

66.26 17.51 20

65.45 15.84 20

6.90 6.08 20

Range 0-25 “From Shepherd and Fagan (1979). bro,o, = 34.

48

Patricia Ann Shepherd and Joseph F . Fagan I l l

between the ability of a normal 7-month-old infant and a normal newborn in resolving stripes. The final group of 32% (or 15 out of 47) acted as a group somewhat like newborn infants in that they could resolve only very wide stripes. While these estimates of the extent of pattern perception are derived from only one sample and are thus subject to sampling variation, the results do indicate some minimal level of pattern discrimination in profoundly retarded children. In fact, the results of Shepherd and Fagan (1979) which find pattern discrimination in profoundly retarded children agree with previous studies by Berkson (1966), Rynders and Friedlander (1972), Friedlander and Knight (1973), and others who found other evidence of visual function in profoundly retarded children, such as gross tracking ability, preference for color motion pictures, brightness discrimination, etc., although the Shepherd and Fagan study employed the preferential looking technique requiring only the ability to direct one’s gaze, while the previous research used techniques that, in most cases, required children to press a panel. In addition, the reliability of the visual preference test employed by Shepherd and Fagan was quite high at .84. In fact, the actual mean pattern preference scores for individuals obtained by the two observers, one of whom tested the children initially and the other who tested them later, were in very close agreement, the absolute differences between them being rather low. Practically, such high test-retest agreement indicates that tests for visual pattern preferences could be used to identify either development of or deterioration of visual function in the profoundly retarded population. The results also suggest that observers can be easily trained to evaluate the visual behaviors of profoundly retarded children.

B. Recognition Memory Just as the limited behavioral repertoire of the profoundly retarded child makes assessment of visual acuity difficult, it also presents an obstacle in the evaluation of memory. In the present section, we focus on studies by Butcher (1977), Switzky et al. (1979), and Shepherd and Fagan (1980). Each of these investigators circumscribed the problem posed by the limited behavioral abilities of their subjects by employing the visual interest test to examine the visual recognition memory abilities of profoundly retarded children. Butcher explored visual recognition memory in 16 institutionalized profoundly retarded children having a mean chronological age of 6 years and a mean Bayley mental age of 5 months. The subjects had a variety of medical diagnoses and only three of the 16 were ambulatory. Butcher tested each child’s immediate and delayed recognition memory for each of two recognition memory problems on each of 2 days. The stimuli used in the Butcher study were four achromatic photographs of faces (two males and two females) and four two-dimensional colored patterns (one solid red square and one solid green square; one set of 24

VISION, MEMORY, AND PROFOUND RETARDATION

49

small red diamonds on a white background and an identically patterned set of green diamonds). On each day, the procedure was to allow 2 minutes of study time of one of the eight stimuli, followed by a test trial which consisted of a 10-second paired comparison presentation of the previously seen stimulus with a novel stimulus of the same class (i.e., the faces were paired with faces and colored patterns with colored patterns). Using a stimulus from the remaining stimulus class (e.g., faces if colored patterns had been used in the first recognition memory problem), a second recognition task was administered. Delayed recognition for each problem was tested during a session by again pairing each previously seen stimulus with its corresponding novel stimulus for another 10 second test period. On the first day, a child was given two such immediate and delayed memory tests. On the second day, each child was given the remaining two memory tests. Thus each child was given all of the four possible memory problems (two face and two color problems). To determine if the profoundly retarded children exhibited immediate or delayed recognition, the time the children spent looking at the two stimuli during test trials was analyzed. For each of the four recognition memory problems, the total time during a test trial spent looking at the novel stimulus was divided by the total looking time for both stimuli to arrive at a percentage score. A t test was used to see if the obtained percentage to novelty deviated significantly from a chance value of 50%. Butcher found that the profoundly retarded children she studied gave evidence of immediate recognition memory for each of the two face problems and for the distinction between a large red square and a large green square. The children exhibited delayed recognition only for the large squares varying in color. Switzky et al. explored visual recognition memory in 12 institutionalized profoundly retarded children having a mean chronological age of 10.3 years and a mean Developmental Quotient of less than 6 months as measured by the Denver Developmental Screening Test. The children had no obvious visual defects and none were ambulatory. An habituation paradigm was employed. Each child was presented with either a 2 x 2 or a 12 X 12 black and white checkerboard pattern for a minimum of eight study trials. A trial began when the child first looked at the stimulus and ended when the child had not looked at the stimulus for 2 consecutive seconds. Study trials continued to be presented until the child achieved a preset habituation criterion. When the criterion for habituation had been met, the child saw three successive presentations of the previously seen stimulus alternating with a novel stimulus. For example, a child who had been allowed to study the 2 x 2 checkerboard (which we will call A for convenience), was then shown the 12 x 12 checkerboard (B) such that the order of the test trials was ABABAB. Half of the children were allowed study trials with the 2 x 2 checkerboard and half with the 12 X 12 checkerboard. Switzky et al. found that profoundly retarded children demonstrated immediate recognition memory. That

50

Patricia Ann Shepherd and Joseph F. Fagan 111

is, when presented with the novel stimulus the children looked significantly longer at it than at the previously studied stimulus. Taken together, the studies of Butcher and Switzky demonstrate that profoundly retarded children can hold in memory, at least for brief periods, a previously seen color (red or green), an abstract pattern such as a black and white checkerboard varying in size and number of elements from a second checkerboard, and can recognize achromatic photographs of faces (men and women). The profoundly retarded may also, under some conditions, remember for longer periods which of two colors they have seen. The initial aim of the Shepherd and Fagan (1980) study was to replicate the findings of Butcher and of Switzky et al. that visual recognition memory occurs on the part of profoundly retarded children for various patterned targets. Of the subjects who had participated in the Shepherd and Fagan (1979) study of visual acuity, 17 were chosen to participate in the 1980 study. The targets employed by Shepherd and Fagan (1980) were composed of pattern elements presumed to be readily visible to the children since the pattern elements of any target were at least as large as those the children had discriminated in the Shepherd and Fagan (1979) study of visual acuity. A more important aim of the 1980 study, however, was to discover if profoundly retarded children would demonstrate immediate recognition memory for each task within a series of recognition memory tasks presented during an experimental session. The profoundly retarded children tested by Butcher involved very dissimilar items from task to task (faces and colors). In the Shepherd and Fagan (1980) study, however, each child was given, during a session, four different memory problems, each involving a distinction between abstract patterns. Children were seen for three such experimental sessions, yielding a total of 12 immediate recognition tests. Finally, both Butcher and Switzky et al. reported only group data for profoundly retarded children. While it is important to learn how a group such as those called “profoundly retarded” may behave, it is also important to find out if reliable differences in memory ability among individuals in the group exist. Hence, the final goal of Shepherd and Fagan (1980) was to discover if reliable individual differences in recognition memory occur among profoundly retarded children. The sample in the Shepherd and Fagan recognition memory study included 17 profoundly retarded children with a mean chronological age of about 7 years and a mean Bayley mental age of 4 months. These children were randomly chosen from the 47 children who participated in the 1979 acuity study. Of the 17, 12 were drawn from a group of children who, as individuals, had reliable preferences for patterning over a series of five striped patterns when originally tested for acuity. The remaining five came from a group of children who, as individuals, did not have reliable preferences for all striped patterns, but only for the largest of the patterns (1/2” and 1/4” wide stripes and, possibly, 1/8” and 1/16”) when originally tested for acuity.

VISION, MEMORY, A N D PROFOUND RETARDATION

51

The stimuli displayed by Shepherd and Fagan (1980) are shown in Fig. 2. Nine of the stimuli were sharply contrasting, black and white patterns, while four were lower contrast gray and white patterns. The gray and white patterns were employed as a test of whether or not children could perceive and remember relatively low contrast stimuli. The most narrow pattern element of any target was at least 1/8 of an inch wide. In effect, all the target patterns were composed of

FIG.2. Nine high-contrast (black and white) and four lower contrast (gray and white) patterned stimuli employed to construct recognition memory problems for profoundly retarded children. (From Shepherd t Fagan, 1980.)

52

Patricia Ann Shepherd and Joseph F . Fagan 111

elements that were as large or larger than the stripes which the children had previously found to be discriminable. Additionally, all the patterns contained varying spatial frequencies presumably making the pattern elements somewhat easier to see. Thus it was assumed that each pattern was well within each child’s acuity limits. During an experimental session, each child was given four memory problems. Each memory problem employed two different patterns and consisted of two 15-second study periods followed by two 5-second test trials during which the previously seen target was paired with a novel stimulus (reversing left and right positions from one period to the next). Each child participated in three experimental sessions. Each session included four memory problems. For the f ist two experimental sessions, the children had memory problems comprised of black and white stimuli only. During the third session only gray and white stimuli were shown. Thus, four novelty preference scores were obtained during each of the three experimental sessions for a total of 12 scores for each child. To discover if the profoundly retarded children, as a group, would demonstrate immediate recognition memory for each memory problem within a series of such problems, the novelty score data were collapsed across the three experimental sessions and a mean preference for novelty was found for each serial position. The results are shown in Table 11. As one can see, the 17 profoundly retarded children in the Shepherd and Fagan study gave ample evidence of visual recognition memory. Specifically, they demonstrated an unequal distribution of visual fixation to novel and previously seen stimuli, with significantly more attention to the novel stimulus on three of the four recognition memory problems administered during a test session. Furthermore, the order of these preferences indicates TABLE I1 MEANPERCENTAGE OF FIXATION TO NOVEL PATTERNED STIMULI BY PROFOUNDLY RETARDED CHILDREN FOR EACHOF FOURRECOGNITION MEMORY PROBLEMS AS A FUNCTION OF INPUT SERIALPOSITION“ Serial position Measure

1

2

3

4

M

60.0Ob 9.68 17.00 4.38

61.Wb 14.99 17.00 2.91

61.0Ob 13.42 17.00 3.25

56.00 16.63 17.00 I .39

SD

N t

“From Shepherd and Fagan (1980). bp

< .01.

53

VISION, MEMORY, AND PROFOUND RETARDATION

TABLE 111 MEANPERCENTAGE OF FIXATION TO NOVELPATTERNED STIMULI ACROSS TWELVE RECOGNITION MEMORY PROBLEMS FOR EACHOF SEVENTEEN PROFOUNDLY RETARDEDCHILDREN a -

X

SD

r

75 70 68 65 64 63 58 65 57 56 55 54 54 54 54 48 47

23.88 17.28 31.62 18.12 24.18 17.81 14.71 38.60 19.45 18.97 14.97 19.34 13.70 20.56 14.41 16.30 21.51

3.556 4.00b 1.99' 2.80* 2.00r 2.44c 1.94c 1.35 1.26 1.oo 1.11 .65 .92 .63 1.05

- .46 - .44

"From Shepherd and Fagan ( 1980). b p < .01. ' p < .05.

that the children were capable of storing at least the first three visual stimuli for retrieval in order to discriminate previously studied from novel stimuli. That is, as a group, the retarded children gave evidence of recognition memory for the first, second, and third serial positions, while not, as a group, demonstrating recognition memory for problems presented in the fourth serial position. A more detailed analysis indicated no significant changes in novelty preference due to input serial position during a session, to contrast level (gray and white targets were retained as easily as black and white targets), or to the interaction of contrast level and position. A secondary analysis based upon each child's mean preference for novelty over the 12 recognition memory problems revealed reliable individual differences in immediate recognition memory among the 17 profoundly retarded children. In Table 111, one can see the mean preference for novelty scores for the seventeen children tested by Shepherd and Fagan (1980) along with their respective standard deviations and t values. Seven of the seventeen children (41% of

54

Patricia Ann Shepherd and Joseph F . Fagan Ill

the sample) had, as individuals, statistically significant preferences for novelty, while ten did not. In summary, the results of Shepherd and Fagan (1980), taken together with those of Butcher and of Switzky et al., lend strong support to the idea that the capacity for immediate recognition memory is a general one in the profoundly retarded, holding for faces, colors, high-contrast abstract patterns, and lowcontrast abstract patterns. Furthermore, the results of Shepherd and Fagan suggest that profoundly retarded children, like normal infants, vary in their capacity to store and retrieve visual information.

IV. SUMMARY AND DISCUSSION Our purpose has been to demonstrate that methods developed to assess visual perception and recognition memory in normal infants can be used to study similar processes in the profoundly retarded. Our definition of the profoundly retarded was limited to those persons under 12 years of chronological age with mental ages, as well as can be determined, of less than 1 year. Several methods currently used to assess visual functioning in normal infants were described. After briefly citing the advantages and disadvantages of two assessment methods, the elicitation of optokinetic nystagmus and the measurement of visual evoked potentials, we concentrated on the most frequently used method for measuring the infant’s visual abilities, the visual interest test. To date, the use of the visual interest test has enabled researchers to make estimates of infant visual acuity and has allowed exploration of parameters which affect visual recognition memory in infants. The visual interest test holds promise, not only for the continued exploration of the infant’s visual world, but also for the eventual development of clinical tools with which to measure individual differences in pattern detection and in intelligence. Drawing support from studies with normal infants, Butcher (1977), Switzky et al. (1979), and Shepherd and Fagan (1979, 1980) employed the visual interest test to show that many profoundly retarded children can see and, further, that many can remember what they see. Specifically, the majority of profoundly retarded children seem well able to detect the patterning present in highly contrasting sets of stripes as narrow as 1/16” in width. Some individuals among the profoundly retarded show even finer minimum separable acuity across more narrow stripe widths and when faced with low-contrast facial patterns. In general, the profoundly retarded demonstrate immediate recognition memory as inferred from their novelty preferences which are exhibited when they are faced with previously exposed and novel targets varying simultaneously in multiple aspects of patterning. Moreover, such immediate recognition memory is demonstrated when multiple recognition tests are administered during a single session. Finally, some profoundly retarded children seem more efficient than others in recognizing patterns.

VISION, MEMORY, AND PROFOUND RETARDATION

55

In closing, we would like to note some possibilities for future research in the study of pattern detection and pattern recognition in the profoundly retarded and to point out practical implications which may be derived from such basic research. The list of possibilities for future research is quite long, even in the seemingly limited domain of vision. Hence, the suggestions made here are not meant to be exhaustive. In the area of pattern detection, we suggest the study of monocular acuity and the derivation of acuity estimates from contrast sensitivity functions. Thresholds for minimum visual acuity (e.g., finding the narrowest black line visible on a white background) and minimum separable acuity (e.g., detection of the pattern inherent in black and white gratings) may easily be derived by covering one eye at a time and presenting the acuity test stimuli in order to yield estimates of how well the eyes function separately. If it were found that the acuity for one eye was much poorer than that of the other eye, ophthalmic techniques (e.g., patching the good eye) might be indicated to improve the sight in the poorer eye. Such a problem is likely in profoundly retarded children with strabismus. Repeated testing of monocular acuity during the course of treatment would enable the physician to assess improvement in vision. A second suggestion for further studies of pattern detection lies in the investigation of acuity via the plotting of contrast sensitivity functions. As noted in an earlier section of this article, tests of acuity derived from the presentation of stimulus patterns varying not only in stripe width but in contrast allows an especially sensitive estimate of acuity along with a description of a pattern in terms of its detectability. With an estimate of how well each profoundly retarded child detects pattern at various contrasts, we could proceed to develop stimulus materials for more sophisticated research into each child’s pattern recognition abilities, materials that we could be sure were within each child’s realm of visual detection. By the same token, educational materials could be developed to take into account an individual child’s visual needs. At present, it is often questionable whether the visual materials used in the education of profoundly retarded children are detectable by any or all of the children. Finally, refined estimates of pattern detection may have more general application within the profoundly retarded population than simply as measures of eyesight. For example, tests of acuity could be used to report side-effects resulting from medical interventions. Certain drugs, for example, are known to cause blurred vision. It would be useful if research were directed toward identification of profoundly retarded individuals who suffer such visual side-effects. It may be that drugs which disturb the acuity of normal individuals also have a distorting effect for some profoundly retarded persons. Practically, such findings could be important in the education of profoundly retarded children by allowing the determination of optimal schedules of necessary medications for those whose vision is affected. We might also find that the drugs prescribed for the profoundly retarded, which do not affect the acuity of a normal person, do affect the vision

56

Patricia Ann Shepherd and Joseph F . Fagan I l l

of a profoundly retarded individual. Tests of acuity could thus serve as both baseline and evaluative measures of drug-related medical treatments. A second, and final, example of the general use of acuity testing is to note that changes in visual acuity may be concomitant to changes in overall physical condition of a profoundly retarded child. It is possible that changes in acuity accompany general physical improvement or, more especially, physical deterioration, as in the case of progressive disease. With repeated testing, deterioration of visual acuity could be charted. Such information would be of practical value, providing an additional description of the deterioration process. Medical and support personnel who work with profoundly retarded persons could employ such information to the extent that it would be relevant to their treatment of the affected individual. In the area of pattern recognition, we suggest research on the identification of abstract patterns that may communicate meaning such as pictures of objects, hand motions, and letter-like forms. In addition, it may also be beneficial to undertake studies on the processing of the information contained in naturally occurring patterns, such as faces. The ability on the part of the profoundly retarded child to differentiate among abstract forms has significance for educational success. If one wishes, for example, to present pictures of objects to be used by retarded children as “words” for those objects or to teach sign language to retarded children, it seems reasonable to first discover if the children in such programs can recognize the objects or the manual gestures. In a similar vein, we do not know whether profoundly retarded children are able to discriminate among abstract forms which resemble letters of the English alphabet. If, indeed, on the basis of visual recognition studies, such letter-like forms are found to be discriminable, a systematic program could be developed to train profoundly retarded children in letter recognition. With regard to facial patterning, we know from previous research that some of the profoundly retarded will look at photographs of human faces and, in addition, some may also remember them. We might further ask if such children are able to perceive more subtle differences between faces, such as variations in facial expression within the same face, e.g., the difference between a happy and an angry expression. A practical reason for exploring the recognition of facial expressions is that expression signifies affect and particular affective displays may be associated with approval or disapproval of an act. The recognition of such affect would be of great importance to a deaf but sighted profoundly retarded child being taught self-help skills. For example, in being taught to feed himself, he may gain information as to the consequences of his acts if he is able to discern a frown after he throws a spoon. In general, future studies exploring the parameters of recognition memory in the profoundly retarded will be most influential in the development of appropriate educational programming. The temporal limits of delayed recognition, the possibilities of proactive and retroactive interference, the contextual or temporal

VISION, MEMORY, AND PROFOUND RETARDATION

57

factors which may hasten or impede the encoding of information from a visual target, and many other parameters remain to be systematically examined in the profoundly retarded. Programmatic research on the visual memory abilities of individual profoundly retarded children may also facilitate identification of those children who can most benefit from existing educational methods, as well as identifying, for the present, those children who may not be so likely to profit from existing programs. In closing, we would emphasize the fact that individual differences in pattern detection and in recognition memory exist among the profoundly retarded. The measurement of such differences may eventually result not only in more appropriate educational materials and procedures but also in the identification of those profoundly retarded children who will most benefit from an education. Of most importance, in our opinion, is that the development of cognitive assessment techniques, based on visual detection and recognition, will allow the description of individual profoundly retarded children in terms of their functional visual and memory capabilities which may be directly relevant to the planning of individual treatment, rather than describing such children in terms of etiology or medical symptomology. REFERENCES Banks, M. S . , & Salapatek, P. Infant pattern vision: A new approach based on the contrast sensitivity function. Journal of Experimental Child Psychology (in press). Berkson, G. Eye fixation responses of profoundly defective children. American Journal of Mental Deficiency, 1966, 71, 492-500. Berkson, G . . & Landesman-Dwyer. S. Behavioral research on severe and profound mental retardation (1955-1974). American Journal of Mental Deficiency, 1977, 81, 482-454. Bornstein. M. H. Infants’ recognition memory for hue. Developmental Psychology, 1976, 12, 1 85- 191.

Brennan, W. M., Ames, E. W., & Moore, K. W. Age differences in infants’ attention to patterns of different complexities. Science, 1966, 151, 355-356. Butcher, M. 1. Recognition memory for colors and faces in profoundly retarded young children. Intelligence, 1977, 1, 344351. Caron, R. F., & Caron, A. J. The effects of repeated exposure and stimulus complexity on visual fixation in infants. Psychonomic Science. 1968, 10, 207-208. Cohen, L. B., Deloache, J. S., & Pearl, R. A. An examination of interference effects in infants’ memory for faces. Child Development, 1977, 48, 88-96. Cornell, E. H. Infants’ visual attention to pattern arrangement and orientation. Child Development, 1975, 46, 229-232. Cornell, E. H. Infants’ recognition memory, forgetting, and savings. Journal of Experimental Child Psychology, 1979, 28, 359-374. Decker, T. N., & Wilson, W. R. The use of visual reinforcement audiometry (VRA) with profoundly retarded residents. Mental Retardarion, 1977, 15, 40-41. Dobson, V., & Teller, D. Y.Visual acuity in human infants: A review and comparison of behavioral and electrophysiological studies. Vision Research, 1978, 18, 1469-1483. Fagan, J. R. Memory in the infant. Journal of Experimental Child Psychology, 1970,9, 217-226.

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Fagan, J. F. Infants' delayed recognition memory and forgetting. Journal of Experimental Child Psychology, 1973, 16, 424-450. Fagan, J. F. Infant recognition memory: The effects of length of familiarization and type of discrimination task. Child Development, 1974, 45, 351-356. Fagan, 1. F. Infants' recognition of invariant features of faces. Child Development, 1976, 47, 627-638.

Fagan, J. F. An attention model of infant recognition. Child Development, 1977,48, 345-359. (a) Fagan, J. F. Infant recognition memory: Studies in forgetting. Child Development, 1977,48,68-78. (b) Fagan, J. F. The origins of facial pattern recognition. In M. Bornstein & W. Kessen (Eds.), Psychological development from infancy. Hillsdale, N.J.: Erlbaum, 1979. Fagan, J. F. Infant memory. In T. Field (Ed.),Review in human development. New York: Wiley . (In press). Fagan, J. F., & McGrath, S. K. Infant recognition memory and later intelligence. Intelligence, 1981. (In press) Fagan, 1. F., & Shepherd, P. A. Theoretical issues in the early development of visual perception. Paper presented at the Johnson & Johnson Symposium on Developmental Disab Preschool Child. Chicago, September 6, 1979. Fagan, J. F., & Singer, L. T. The role of simple feature differences in infants' recognition of faces. Infant Behavior and Development. 1979, 2, 39-45. Fantz, R. L. A method for studying early visual development. Perceptual andMotor Skills, 1956.6, 13-15.

Fantz, R. L. Pattern vision in newborn infants. Science, 1963, 140, 296-297. Fantz, R. L. Visual experience in infants: Decreased attention to familiar patterns relative to novel ones. Science, 1964, 146, 668-670. Fantz, R. L., & Fagan, J. F. Visual attention to size and number of pattern details by term and preterm infants during the first six months. Child Development, 1975, 46, 3-18. Fantz, R. L., Fagan. J. F., & Miranda, S. B. Early perceptual development as shown by visual discrimination, selectivity, and memory with varying stimulus and population parameters. In L. Cohen & P. Salapatek (Eds.), Infant perception: From sensation to cognition. Vol. I . Basic visual processes. New York: Academic Press, 1975. Fantz, R. L., & Miranda, S. B. Newborn infant attention to form of contour. Child Development, 1975, 46, 224-228.

Fantz, R. L., Ordy. J . M., & Udelf, M. S. Maturation of pattern vision in infants during the first six months. Journal of Comparative and Physiological Psychology, 1962, 55, 907-917. Friedlander, B. Z., & Knight, M. S. Brightness sensitivity and preference in deaf-blind retarded children. American Journal of Mental Deficiency, 1973. 78, 323-330. Friedlander, B. Z., Silva, D. A., & Knight, M. S. Multiply handicapped partially sighted children's capability for resolving visual images. Exceptional Children. 1974, 41, 121-123. Friedman, S. B. Habituation and recovery of visual response in the alert human newborn. Journal of Experimenral Child Psychology, 1972, 13, 339-349. Friedman, S. B., Bruno, L. A., & Vietze, P.Newborn habituation to visual stimuli: A sex difference in novelty detection. Journal of Experimental Child Psychology, 1974, 18, 242-251. Harter, M. R., Deaton, F. K., & Odom, J. V. Pattern visual evoked potentials in infants. In J. E. Desmedt (Ed .) Visual evoked potentials in man: New developments. London: Oxford University Press (Clarendon), 1977. Hershenson, M. Visual discrimination in the human infant. Journal of Comparative and Physiological Psychology, 1964, 58, 270. Karmel, B. Z. The effects of age, complexity, and amount of contour on pattern preferences in human infants. Journal of Experimental Child Psychology, 1969, 7 , 339-354.

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Lasky, R. E. Length of familiarization and preference for novel and familiar stimuli. Infant Behavior and Development, 1980, 3, 15-28. Leehey, S., Moskowitz-Cook, A., Brill, S.,& Held, R. Orientation anistropy in infant vision. Science, 1975, 190, 900-902. McCall, R. B., Kennedy, C. B., & Dodds, C. The interfering effects of distracting stimuli on the infants’s memory. Child Development, 1977, 48, 79-87. McGurk, H. Infant discrimination of orientation. Journal of Experimental Child Psychology, 1972, 14, 151-164. Martin, R. M.Effects of familiar and complex stimuli on infant attention. Developmental Psychology, 1975, 11, 178-185. Milewski, A. E. Young infants’ visual processing of internal and adjacent shapes. Infant Behavior and Development, 1978, 1, 359-371. Milewski, A. E., & Siqueland, E. R. Discrimination of color and pattern novelty in one-month infants. Journal of Experimental Child Psychology, 1975, 19, 122-136. Miranda, S. B., & Fantz, R. L. Distribution of visual attention of newborn infants among patterns varying in size and number of details. Proceedings, American Psychological Association, Washington, D. C., 1971. Miranda, S. B., & Fantz, R. L. Recognition memory in Down’s Syndrome and normal infants. Child Development, 1974, 45, 651-660. Olson, G. M. An information processing analysis of visual memory and habituation in infants. In T. J. Tighe & N. Leaton (Eds.), Habituation: Perspectives from child development, animal behavior, and neurophysiology. Hillsdale, N.J.: Erlbaum, 1976. Olson, G. M. Infant recognition memory for briefly presented visual stimuli. Infant Behavior and Development, 1979, 2, 123-134. Rynders, J. E., & Friedlander, B. 2. Preferences in institutionalized severely retarded children for selected visual stimulus material presented as operant reinforcement. American Journal of Mental Deficiency, 1972, 76, 568-573. Salapatek, P., & Banks, M. S. Infant sensory assessment: Vision. In F. D. Minifie and L. L. Lloyd (Eds.), Communicative and cognitive abilities: Early behavioral assessment. Baltimore, Md,: University Park Press, 1978. Shepherd, P. A., & Fagan, J. F. Visual pattern perception in severely and profoundly retarded children. Paper presented at the Twelfth Annual Gatlinburg Conference on Research in Mental Retardation and Developmental Disabilities, Gulf Shores, Ala., April, 1979. Shepherd, P. A., & Fagan J . F. Visual recognition memory in the profoundly retarded child. Paper presented at the Thirteenth Annual Gatlinburg Conference on Research in Mental Retardation and Developmental Disabilities, Gatlinburg, Tenn., March, 1980. Silva, D. A,, Knight, M.S., & Friedlander, 8 . Z. Visual tracking in deaf-blind retarded preschool children. Exceptional Children, 1973, 39, 574-575. Siqueland, E. R., & DeLucia, C. A. Visual reinforcement of non-nutritive sucking in human infants. Science, 1969, 165, 1144-1 146. Stechler, G. Newborn attention as affected by medication during labor. Science, 1964, 144, 315317.

Strauss, M. S . , & Cohen, L. B. Infant immediate and delayed memory for perceptual dimensions. Paper presented at the International Conference on Infant Studies, New Haven, Ct., April, 1980. Switzky, H. N., Woolsey-Hill, J., & Quoss, T. Habituation of visual fixation responses: An assessment tool to measure visual sensory-perceptual cognitive process in nonverbal profoundly handicapped children in the classroom. American Association for the Education of the Severely and Profoundly Handicapped Review, 1979. 4 (2). 136-147. Topinka. C. V., & Steinberg, B. Visual recognition memory in 3% and 7% month-old infants. Paper presented at the International Conference on Infant Studies, Providence, R.I., March, 1978.

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Wallstein, R. S . , & Hesse, G. W. Hue discrimination in deaf, blind children. Paper presented at the meeting of the Eastern Psychological Association, New York, April, 1975. Werner, J . S., & Perlmutter, M. Development of visual memory in infants. In H . W. Reese and L. P. Lipsitt (Fils.), Advances in child development and behavior (Vol. 14). New York: Academic Press, 1979. Werner, J . S., & Siqueland, E. R. Visual recognition memory in the preterm infant. fnfanr Behavior and Development. 1978, 1, 79-94.

Studies of Mild Mental Retardation and Timed Performance T. NElTELBECK DEPARTMENT OF PSYCHOLOGY UNIVERSITY OF ADELAIDE ADELAIDE, SOUTH AUSTRALIA

N. BREWER INSTITUTE OF SPECIAL EDUCATION BURWOOD STATE COLLEGE MELBOURNE, AUSTRALIA

................................... 11. Simple Reaction Time (RT) . . . . . . . . . . . A . Absolute Differences . . . . . . . . . . . . .

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IV. Choice Reaction Time (CRT) A . Background: Correlationa

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VI. Cognitive Influences . . . . . . . . . . ........................ A. Background . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . B. Methodological Factors ........................... C. Processing Differences: Specific or General? . . . . . . . . . . . . . . . . . . . . . . . . . . . VII. Conclusions . . . . . . . . . . . . . . . . . . ............... A. Attention and Central Executi ............................. B. Suggested Directions for Futu .................... VIII. Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . References . . . . . . . . . . . . . . . . . . ...................

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INTRODUCTION

A. Background Attempts to explore the substance of mental processes date back to the beginnings of experimental psychology, and by the end of the nineteenth century Cattell, Kraepelin, Oehrm, and others had sought to develop exact measures of sensation and discrimination. Simple reaction time (RT) was among the procedures explored at that time, on the grounds that it should provide an index of the speed with which the brain makes decisions governing adaptability. Early researchers reported slowed RT in association with various psychotic conditions, and there was some evidence that “dull” children were slower to respond than “average or bright” children; but on the whole results from studies of this kind were considered disappointing (Wissler, 1901). Following the successful development of mental tests, and those practical procedures for influencing behavior that derived from theories of learning, the search for measures of cognitive activity declined. Interest in cognitive processes has been rekindled by the recognition that while available intelligence tests and the like provide some guide to an individual’s abilities to solve problems and deal with everyday circumstances, they are generally less useful if we wish to examine the nature of individual differences in ways that people think. Although it was the intention of those devising such tests to provide the skilled clinician with a means of unraveling the strategies used in reaching a particular solution, this feature of testing has often been ignored. Furthermore, the extent to which the tests reveal fundamental processes involved in problem solving is limited. From the time of Binet’s pioneering work the intention has been to devise practical means of measuring purposeful, intelligent behavior, rather than the development of a theory of intelligence. This perspective means that although an intelligence test can be used to reveal some of the behavioral and cognitive characteristics of mentally retarded individuals, test performance cannot tell us much about the structural or functional features of lower intelligence.

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Similarly, it may be seen that despite the valuable potential of stimulusresponse (S-R) theories to generate practical solutions to behavioral problems, such theories are not designed to distinguish individual differences in cognitive abilities (O’Leary & Wilson, 1975). Indeed, practitioners who work within an S-R model would regard it as an advantage of their approach that it is possible to modify behavior by manipulating the formation and strength of associations between stimuli and the responses made to them, without accounting for hypothetical entities that cannot be observed directly.

B. An Information Processing Approach An information processing approach to the study of mental events provides a framework from within which to examine more closely the nature of individual differences in mental abilities. One attempts to focus upon cognitive events which, although not directly observable, may be inferred to intervene between the occurence of a stimulus and the response that follows. When applied to the study of mentally retarded persons, the expectation is that this method may advance our understanding of their functioning in terms of mental processes involving the selection, transformation, and retention of knowledge. A theoretical issue that has generated much discussion involves a distinction between structural and functional aspects of the processing system (Atkinson & Shiffrin, 1968; Fisher & Zeaman, 1973). This distinction derives from the analogy of the brain as a computer; like “hardware” components within a computer system, structural characteristics of information processing are envisaged as stable, permanent, and not subject to modification by training. Although Atkinson and Shiffrin (1968) have suggested that some processes may be incorporated within the structural features of the system, just as some programs are permanently built into a computer system, the term “function” has generally referred to the control of processing within the structure. Functional aspects of processing therefore include the plans and strategies adopted by those executive processes that are hypothesized to be responsible for search and selection, and for the organization, transformation, and transfer of information within the system. The influence of various subjective components, such as motivation, persistence, and affect, as well as broad experiential factors related to education and culture are also included among functional characteristics. The distinction between structure and function has had heuristic value, encouraging researchers to explore the capabilities of retarded persons more thoroughly (Belmont & Butterfield, 1969; Butterfield & Belmont, 1977; Campione & Brown, 1977). However, there are differences of detail between theories as to what properties of cognition might be regarded as structural or functional. As Campione and Brown (1977) have pointed out, Piaget’s theory postulates that structural changes accompany ontongenetic development, and that subsequent functional characteristics will depend on such changes. Some researchers have

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proposed an interaction between structure and function, such that improvement in the structure of intellect can be achieved through prerequisite functional development. In these terms, providing the appropriate intervention over very extensive periods of time can result in structural improvements that overcome socioeconomic disadvantage and environmental deprivation (Clarke & Clarke, 1978), or even organic factors and genetic endowment (Feuerstein, 1977). The following examples illustrate further some of the conceptual problems with the structure-function distinction. Although short-term memory is generally regarded as a structural feature, it is well established that its capacity depends on coding (Miller, 1956). Thus capacity may remain constant if materials were organized in one way, but change appreciably if organized in another. Consider also the processes by means of which stimulus information is translated into action-processes which might presumably be regarded as functional characteristics of the system. Yet the difficulty of maintaining this structure-function distinction is illustrated by the theory of Schneider and Shiffrin (1977; Shiffrin & Schneider, 1977) who identify those processes that require attentional control and those that do not. Processes in a given situation may change, with performance approaching an asymptotic level as automatic processing develops with continued practice. Craik and Lockhart (1972) have expressed similar ideas, emphasizing functional characteristics rather than structure as determining the limits of information processing, and proposing that the degree of flexibility in processing reflects the ‘‘level” or “depth” at which analysis proceeds. Research into the cognitive functioning of mentally retarded persons has reflected this shift in theoretical emphasis from structural limitations to differences in functional characteristics. For example, where previously Ellis ( 1963) and Spitz (1963) favored explanations of the functioning of retarded persons in terms of structural ’ deficiencies, they have subsequently extended their positions to include functional components of information processing, such as attention, rehearsal, and retrieval (Ellis, 1970; Spitz, 1973). Recent research has sought to distinguish between structural and functional deficiencies in the processes of mentally retarded persons by monitoring the influence of training on performance, it being argued that, because functional processes are flexible, they are susceptible to training, whereas structural features are not (Campione & Brown, 1977). There are, however, problems with this approach, since a conclusion that structural limitations underly performance requires that no further improvement is possible, something that can never be proved. Campione and Brown (1977) have drawn attention to the reality that whether deficient performance is attributed to structure or function will depend in practice on the cost and effort required in order to develop a particular skill, with the probability that some kind of structural limitation is implicated increasing accordingly. Thus far, the outcome of training retarded subjects in specific cognitive

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strategies has not clarified the fundamental nature of limitations to retarded performance. It has been demonstrated clearly that retarded persons can learn to use processes that improve their performance dramatically-a result of considerable practical significance. However, there is as yet no evidence that such persons will spontaneously adopt these processes if required to do so. Although some studies have demonstrated limited transfer effects (Clarke & Clarke, 1974), it is generally the case that, in the absence of systematic training, retarded persons do not generate appropriate strategies on new occasions. Differences in functional processes are not necessarily overcome by training, and it remains possible that the availability of control processes is a function of intelligence, reflecting biological qualities of the brain that have yet to be determined. A widespread resurgence of interest in timed performance as an index of the brain’s biological efficiency has accompanied advances in computer technology that have permitted complexities of research design and data analysis that were not possible earlier (Broadbent, 1958; Norman, 1976; Posner, 1978; Welford, 1968). The most widely used dependent variables have involved various parameters of simple and choice RT and tachistoscopic recognition performance. These procedures are considered to provide an objective “real time” measure of mental events, under conditions that are readily learned and understood. For this reason, the measures obtained are thought to be relatively independent of motivational factors, as well as sociocultural influences. Provided that a subject is practiced sufficiently beforehand, the outcome has usually been found to be relatively stable for the same conditions, although with practice one finds continual reductions in RT, even after very long periods of time (Teichner & Krebs, 1974). However, the validity of the assumption that even such relatively uncomplicated experimental conditions are equivalent for all subjects has been questioned, particularly where retarded and nonretarded samples have been compared. The major issue involved is that the speed of reaction and the accuracy with which a response is made are not independent;these two covariates are directly controlled by the subject and are therefore extremely difficult for an experimenter to control with precision (Pachella, 1974). We will discuss this aspect of timed performance further in sections to follow. Although some earlier researchers had investigated cognitive processes in association with mental retardation (Scott, 1940) and psychopathological conditions such as schizophrenia (Shakow, 1946), most studies of information processing among retarded persons have been done within the past two decades, with a number of reviews of this work appearing more recently (for example, Baumeister & Kellas, 1968; Ellis, 1970; Hall, 1980; Karrer, Nelson, & Galbraith, 1979; Spitz, 1973; Stanovich, 1978). In this article we selectively review recent studies comparing the information processing performance of mildly retarded and nonretarded persons. In some studies mental age (MA) controls have been used, but in most instances research participants have been young adults,

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and inferences have been based on comparisons between groups of the same chronological age (CA), following the position advanced by Ellis (1969). For a discussion of theoretical issues relevant to the selection of nonretarded comparison groups the reader is referred to Stanovich (1978). We have not attempted a resynthesis of earlier reviews of the area, although it has sometimes been necessary to consider studies included in them. For comparison purposes we have also occasionally made reference to research into other areas of psychopathology. The reader is referred to King (1975) and Nuechterlein (1977), for accounts of research on psychomotor activity in relation to schizophrenia and various mental disorders, and to Welford (1980a) for a discussion of changes in various aspects of RT with aging.

II. SIMPLE REACTION TIME (RT) A. Absolute Differences Earlier research, mostly with mildly and moderately retarded subjects, established three broad conclusions:

1 . Compared with nonretarded populations, the simple RT of mentally retarded persons is slower, irrespective of the modality in which the stimulus is presented, the nature of the response required, or various temporal and intensity parameters of the task (Baumeister & Kellas, 1968). 2. The individual distributions of RT obtained from retarded subjects show greater variability and are more positively skewed than distributions from nonretarded subjects. Mean RT and variability are correlated (Berkson & Baumeister, 1967). Furthermore, retarded group distributions typically display more variability, so that retarded samples are more heterogeneous than nonretarded in this regard (Baumeister & Kellas, 1968). 3. The extent of slowing covaries with clinical estimates of retardation, although this result has not always been found, particularly within a relatively narrow range of IQ scores. However, diagnostic reliability can be improved by including more demanding RT tasks. For example, Weaver and Ravaris (1972, 1974) correctly classified 66% of a large group as either mildly or moderately retarded on the basis of simple and serial RT. Jensen, Schafer, and Crinella ( 1980) have substantially increased correlations between intelligence and performance by taking account of variability, in addition to simple and choice RT. Those studies using severely retarded subjects, including Down’s syndrome individuals, have generally found that the more retarded subjects have slower RT. Besides mentally retarded persons, individuals with diffuse forms of personality and psychotic disorders, as well as persons affected by various neurological

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disturbances and changes that accompany aging, may be characterized by slow RT (King, 1965, 1969, 1975). Distinction between populations is sometimes possible-for example, retarded from autistic individuals (Gold & Gold, 1975). Again, RTs of mildly retarded subjects are usually less slow than those of chronic schizophrenics (King, 1975). RT can also be sensitive to brain damage that is restricted or predominant within one hemisphere (Belmont, Handler, & Karp, 1972; Karp, Belmont, & Birch, 1971). However, there can be considerable overlap between RT measures from various populations when clinical estimates indicate greater severity-for example, Down’s syndrome and psychotic conditions. More recent research has attempted to identify factors influencing cognitive processes that interact with intelligence (Baumeister, 1967). The general procedure has been to compare the RT performance of retarded and nonretarded groups while manipulating additional independent variables. Two such areas of investigation have been the influence of temporal parameters in the simple RT paradigm, and the effects of changes in stimulus intensity. The approach has also been extended to include extensions of the simple RT procedure, such as serial RT where responses are required to each of two stimuli presented in rapid succession. Most studies have involved mildly to moderately retarded participants (unknown etiology), presumably because of difficulties in measuring RT of severely retarded persons in more complex situations. B. Temporal Factors

Experimental procedures involving temporal variables were pioneered by Shakow and his co-workers in their studies of schizophrenia (Huston, Shakow, & Riggs, 1937; Shakow, 1972). The length of the preparatory interval (PI) between the warning signal and the reaction stimulus in the simple RT task is either held constant within a specified block of trials, but changed across blocks (regular procedure), or varied randomly from trial to trial (irregular procedure). The typical RT outcome is as follows: with regular presentations, RT increases as PI is lengthened. With an irregular procedure, RT following short PIS is slower than for the same intervals in a regular series, but becomes faster at longer PIS. Broadly, the same relationships between RT and PI have been found with mildly retarded subjects (Baumeister & Kellas, 1968). When presentation is regular, RT becomes slower with increasing PI. With an irregular procedure, fastest RT follows longer PIS, or sometimes intervals toward the middle of the PI range, if this is extensive. Baumeister and Kellas (1968) reported that differences between retarded and nonretarded groups with the irregular procedure were less when PIS were longer. Kellas (1969a) and Gosling and Jenness (1974) have confirmed these findings. Both these papers also reported that the PI to the immediately preceding trial (termed “preceding preparatory interval * ’-PPI) in-

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fluenced RT among retarded subjects, RT being fastest when the PPI-PI sequence was short-long, and slowest following a long-short sequence. It is widely considered that PI effects involve a central expectancy factor (Baumeister & Kellas, 1968; Poulton, 1973; Shakow, 1962), it becoming increasingly difficult for the subject to focus attention as the PI within the regular procedure is lengthened. Within an irregular procedure shorter PIS permit less opportunity for the subject to develop expectancy about signal occurrence. PPI effects are thought to be the consequence of inappropriate attention to prior stimulation. Thus, if expectation is contingent on the PPI, RT accompanying long-short sequences is slower on average than for short-long sequences because a very long PPI is more likely to be followed by a shorter PI. However, why stimuli earlier than the imperative stimulus influence attention is not understood. Uncertainty about stimulus Occurrence within the irregular procedure may be partially responsible, but this is probably not a sufficient explanation. For example, providing advance information within an irregular procedure about PI length, stimulus position, or stimulus modality does not reduce RT differences between schizophrenics and normals (Nuechterlein, 1977). This line of enquiry has not been pursued more recently with mentally retarded subjects, although continuing research into schizophrenia suggests directions that the study of mental retardation might take (Cromwell, 1975; Nuechterlein, 1977). Although it is difficult to equate comparison groups drawn from different populations, it may be useful if future research attempted to define similarities and differences in the performance of samples from various pathological conditions.

C. Stimulus Intensity It has usually been found that the simple RT of mildly to moderately retarded subjects is more influenced by the intensity of the reaction stimulus than is the case with nonretarded samples (Baumeister & Kellas, 1968). Some of the fmdings can be summarized as follows: 1. Among both retarded and nonretarded subjects RT becomes faster and individual response variability decreases as signal intensity is increased. The relationship is not linear, and among nonretarded subjects RT reaches an asymptote at higher levels of intensity. As yet, the forms of RT functions describing retarded performance for a wide range of stimulus intensities have not been determined. 2. Increasing the intensity of the warning stimulus results in a more marked slowing of RT among retarded than among nonretarded subjects. Baumeister and Kellas (1968) suggested that this outcome results from an interaction with the

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reaction stimulus, the perceived intensity of this being reduced. Baumeister and Wilcox (1969) obtained a similar effect when presenting the warning stimulus without interruption until the reaction stimulus Occurred, suggesting that shortterm memory was not responsible. However, at least one earlier study has reported that a continuous warning stimulus improves retarded RT (Terrell & Ellis, 1964). At this stage no further conclusions can be drawn about the effects of intensity on simple RT among retarded subjects. These effects are not only influenced by the range of stimulation selected, but also by the order in which the subject encounters different intensity values. Conflicting outcomes have been found, depending on whether stimuli were presented within blocks of equal intensity or whether presentation order was irregular (Baumeister & Kellas, 1968; Kellas, 1969a; Kellas & Baumeister, 1970). Furthermore, the influence of both intensity and interval between warning and reaction stimulis may depend on the nature of the response required. Thus, Kellas (1969b) found that variability of RT was most influenced by these factors when the response was to press rather than release a key. More recently, Newell, Wade, and Kelly (1979) report that, even following a fixed PI, the ability of moderately to severely retarded individuals to anticipate the initiation of discrete movements deteriorated as the complexity of the required movement increased. No single explanation has yet emerged that can successfully encompass all available data, and no published research into intensity effects on the performance of mentally retarded subjects has appeared in the past decade. These issues are of theoretical importance, however, and it is to be hoped that the area will attract fresh attention.

D. Serial Reaction Time Only a few studies have compared serial RTs in retarded and nonretarded subjects. Baumeister and Kellas (1967) found that the RTs of mildly retarded subjects to a second stimulus were still markedly delayed when the interval between the initial response (R,) and the second stimulus (S,) was as long as 500 msec, and that there was some delay for R,-S, intervals up to 2 seconds. Nonretarded subjects, on the other hand, were not influenced at intervals beyond about 200 msec, a result in line with other research into the psychological refractory period (Welford, 1968, 1980b). Joubert and Baumeister ( 1970) manipulated the probabilities with which different R,-S, intervals were presented. At the shortest intervals, RTs to S , were faster in both groups when these intervals occurred more frequently. However, compared with nonretarded subjects, mildly retarded subjects were much slower following the shorter intervals, even when the probability of occurrence was

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high. Joubert and Baumeister interpreted these results in terms of an attentional deficiency hypothesis, concluding that retarded subjects were less able to develop preparatory sets appropriate to existing temporal cues. It is possible, however, that these subjects continued to monitor the outcome of the initial response to a more marked extent than nonretarded subjects, so that their attentional capacity was reduced at the time that the second stimulus was presented. Since in these earlier studies S , and S2required different kinds of response, the RTs involved could not be compared directly. Friedrich, Libkuman, and Hawkins (1974) therefore used identical stimulus-response arrangements for both occasions, S2following R, at intervals of 250,500, and 700 msec, and with these arranged either in regular blocks or randomly presented. Although mildly retarded subjects (aveage IQ about 60) were slower overall, the interval factor did not interact with the group factor. The regular procedure reduced RT, among retarded subjects, even at 250 msec, so that where assisted by a regular arrangement these subjects apparently developed appropriate expectancies about the next signal presentation. This interpretation should be treated with caution, however. A subsequent study (Friedrich & Hawkins, 1975) employing somewhat more retarded subjects (average IQ about 45) found that RT2 was slower than RT,, at an interval of 250 msec, irrespective of presentation procedure. Although it is certainly possible that intelligence level would be a critical factor determining what compensations might be gained from regular procedures, it is also the case that where samples are small and group results relatively heterogeneous (as is most frequently the case in research of this kind), interactions can be difficult to establish. At this point we consider it useful to draw attention to similarities between the results discussed so far and the findings from an extensive body of research into changes of psychomotor performance that accompany aging, particularly beyond about 60 years of age. It is now well recognized that such reduced performance in old age comes about principally as a consequence of impaired central processes, by means of which the individual prepares and maintains appropriate states of readiness to respond to stimulation; only negligible aspects of performance seem attributable to less effective sensory processes, to slower nerve conduction and muscle activation (except where very substantial effort involving the whole body is required), to reduced motivation, or to any reduced opportunity for practice (Welford, 1977). A possible explanation for this impaired ability to formulate expectations is a greater tendency among elderly people to continue to monitor the aftereffects of previous actions, so that subsequent decision processes are interfered with when attention is not switched immediately to new incoming signals (Welford, 1980a). Since less efficient performance in old age is acknowledged to be related to a deterioration in brain structures, these similar results for mentally retarded and aged subjects raise the possibility of structural limitations (yet to be established) in retarded individuals.

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E. Coincident Changes in Heart Rate Further evidence that retarded persons have difficulty in preparing to respond to expected stimulation comes from studies of heart rate (HR) deceleration and simple RT (Krupski, 1975; Runcie & O’Bannon, 1975). This work derives from findings that HR falls immediately prior to the onset of expected stimulation (Lacey, 1967; Lacey & Lacey, 1974; Obrist, Webb, Sutterer, & Howard, 1970), with RT and HR being positively correlated. The magnitude of HR deceleration increases with childhood development, as does speed of RT (Sroufe, 1971). Obrist et al. (1970) have suggested that HR changes in the RT task reflect central attentional processes arising out of the integration of both autonomic and somatic activity that prepares the organism to cope with environmental events. Krupski (1975) found much less marked deceleration in HR of mildly retarded young adults compared with university students prior to the occurrence of the reaction stimulus in a simple RT task. There was no significant group difference in HR responding to the warning stimulus, so that presumably signals were effectively registered by retarded subjects. Similar results have been obtained with retarded adults by Runcie and O’Bannon (1975), and for brain damaged war veterans by Holloway and Parsons (1972). These findings suggest that mildly retarded subjects in a simple RT task are less able to use a warning stimulus and PI as a preparation for the reaction to follow. To what extent such attentional problems are related to the accurate judgment of time duration, rather than to distractibility, remains to be established. However, there is evidence from a number of sources that retarded persons are more susceptible than nonretarded persons to distracting factors, distributing their attention over more possible sources of stimulation (O’Connor & Hermelin, 1971). By monitoring the extent to which subjects looked at a continuous warning signal in a simple RT task, Krupski (1977) has directly established that mildly retarded adolescents looked away during PI more frequently than nonretarded high school students of the same chronological age.

F. Conclusions When compared with nonretarded populations, mildly retarded persons have slower, more variable RT, and in this regard they are similar to individuals characterized by diverse forms of psychopathology. The presumably wide differences in the nature of structural damage and impairment aksumed to underlie these different psychopathological conditions suggest that an explanation for slower RT in terms of some single clearly defined structural deficiency-such as inefficient sensory registration, deficient arousal, or defective memory structures-may be inappropriate. The evidence discussed in the preceding sections suggests that attentional difficulties associated with the development of strategies appropriate to expec-

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tancy and the maintenance of set are major determinants of the slower RT of mildly retarded individuals. This position is supported by other areas of enquiry. Thus Krupski (1980) has concluded that attentional deficiencies are largely associated with voluntary processes-which would include focusing and selection-rather than with involuntary, reflex activities controlling arousal. Karrer et al. (1979) have reached a similar conclusion on the basis of an extensive review of psychophysiological research, arguing that poorer performance by retarded persons is more a question of the use made of stimulus information than of deficient registration of stimulation. However, Karrer et al. have also emphasized the importance on considering etiological variables. They draw attention to research by Wallace and Fehr (1970) and by Clausen, Lidsky, and Sersen (1976) which has found less reactive skin resistance among Down’s syndrome children in RT tasks than among normal children. Clausen et al. have also recorded higher levels of HR and skin conductance for Down’s, phenylketonuria, and encephalopathic etiologies, and lower levels for a cultural-familial subgroup, when compared with nonretarded subjects. These results would therefore seem to exclude a single explanation for RT differences in terms of an arousal deficiency, while at the same time suggesting that autonomic nervous functioning related to etiology may influence RT.

111.

REACTION TIME IN MEMORY SCANNING

Sternberg’s (1969a,b, 1975) additive factors procedure requires a choice reaction to a single stimulus presentation. Having first memorized a list of items, termed the “positive” set, the subject decides as quickly as possible whether or not a test stimulus presented subsequently was a member of the positive set. Choice reaction time (CRT) for both positive and negative responses has typically been found to increase in approximately linear fashion, and at the same rate (about 40 msec per item), with the number of items in the positive set. Sternberg assumes that units of information are processed serially through a sequence of independent stages-in particular, stimulus encoding, a comparison between the representation of the target stimulus and memorized material, choosing an appropriate response, and response initiatiodexecution. The essential technique is to influence the duration of CRT by manipulating experimental variables, determining those which produce additive effects and which can therefore be assigned to different stages, and those which because they interact, reflect the operation of some common factor. Sternberg’s interpretation of the linear relationship between CRT and set size is that the slope of this function reflects retrieval operations, representing the rate of memory scanning. Where that function intercepts the ordinate is taken as the time required by the other three stages-namely, encoding, choice of response, and execution of action. Since

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CRT for positive and negative responses increases at the same rate, Sternberg infers that memory scanning is an exhaustive process. Despite a body of evidence which lends support to Sternberg’s theory (Blackman, 1975; Nickerson, 1972; Sternberg, 1975), objections have been raised with regards (a) the procedural assumptions involved (Pachella, 1974), (b) evidence suggesting self-terminating (as opposed to exhaustive) processing (Theios, Smith, Haviland, Traupmann, & Moy, 1973), and (c) the problems that parallel operations pose for the additive factors method (Stanovich & Pachella, 1977; Taylor, 1976). Nevertheless, the additive factors method has generated a great deal of research in the past decade, being accepted as a most useful and powerful procedure for studying information processing. Four published studies have used Sternberg’s procedure to compare memory search in mildly to moderately retarded and nonretarded subjects (Dugas & Kellas, 1974; Harris & Fleer, 1974; Maisto & Jerome, 1977; Silverman, 1974). All have reported higher intercept values for RT functions among retarded subjects than among nonretarded subjects of the same chronological age. These results suggest that the retarded subjects were less effective in perceptual encoding, or in formulating a response, or both. Maisto and Jerome (1977) further examined the question of perceptual encoding by including an experimental condition in which the quality of the test stimulus was degraded so as to extend a subject’s encoding time. Intercept values among mildly retarded subjects were more influenced by this procedure than were those of nonretarded controls, suggesting the conclusion that the encoding processes of retarded subjects were slower. This result did not, however, rule out the possible contribution of response processes. Dugas and Kellas (1974), Harris and Fleer (1974), and Maisto and Jerome (1977) have reported slope functions for retarded groups that were considerably steeper than those in the nonretarded groups. This is therefore evidence that central scanning processes of retarded persons are slower than those of nonretarded persons. Silverman (1974) did not find slope differences between mildly to moderately retarded and nonretarded subjects but RT functions for both groups were unusually steep in this experiment, probably reflecting his use of a continuously displayed positive set-a departure from Sternberg’s procedure. Thus, Silverman’s task did not require a memory scan as defined by Sternberg (1975). There is indirect evidence that the retarded-nonretarded difference suggested by the results of the other three studies is not a consequence of mental age, but is more long-term. Thus, slopes of RT functions found for nonretarded adult groups and for nonretarded children of different ages have been similar, suggesting similar memory scanning rates, despite intercept differences implying that the efficiency of encoding and/or response organization is a function of increasing age (Harris & Fleer, 1974; Hoving, Morin, & Konick, 1970; Maisto & Baumeister, 1975). McCauley, Kellas, Dugas, and DeVellis (1976) combined

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results from a comparison of nonretarded children with above average and below average intelligence (IQ less than 9 3 , and those obtained on another occasion, but under similar experimental conditions, from retarded children. This demonstrated a systematic inverse relationship between the IQ scores of participants in the two experiments and both slope values and intercept values of the associated RT functions. Despite these promising results, however, there are grounds for questioning the conclusions about the nature of differences between retarded and nonretarded subjects in those experiments reviewed here. First, a close examination of these studies reveals a number of awkward anomalies in the results from nonretarded subjects when these are compared with other published studies (see for example Cavanagh, 1972). These differences are impossible to resolve since different experiments have involved subjects from different chronological and mental age groups, together with wide differences in stimulus materials and procedure. Silverman (1974) and Maisto and Jerome (1977) used a fiied-set procedurethat is, the positive set remained unchanged for each set of a given size. However, in the other two studies (Dugas & Kellas, 1974; Harris & Fleer, 1974) the positive set changed from trial to trial (varied set procedure). Second, at least one experiment (Herrmann & Landis, 1977) has produced results indicating a much slower memory scanning rate among normal children aged about 7 years (223 msec per item) than among 12-year-olds (84 msec per item) or 17-year-olds (42 msec per item), in addition to considerable intercept differences. Two control studies subsequent to the main experiment replicated the results among 7-year-olds under instructions emphasizing fast responding and when memory sets were presented visually (instead of being read aloud as in the main study). Furthermore another follow-up experiment established that the slower rate among young children could not be attributed to difficulty in encoding the test stimulus, although there was some suggestion that the outcome may have been different had these children been permitted additional practice. Third, Silverman (1978) and Maisto (1978) have drawn attention to significant negative correlations between slope and intercept values of RT functions for retarded subjects in the available studies. These correlations suggest that the memory search measured by the slope and those other processes measured by the intercept are not independent, so that retarded and nonretarded participants may not have approached the task in the same way. Although Chase (1978) has pointed out that statistical correlation between two variables does not necessarily prove processing interdependence, since separate stages may all be influenced by some other process, the correlations expected under such circumstances would be positive-not negative as found. Bearing in mind the doubts raised by Silverman (1978) and Maisto (1978), it is interesting to note that at least one study of hospitalized schizophrenics has recorded slope values for RT functions that were virtually identical with those

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widely established for normal subjects, although intercept values were considerably higher (Checkosky, cited by Sternberg, 1975). Of course, it is possible that this result reflects important differences between the scanning processes of retarded and schizophrenic individuals, but this would need to be established by a comparative study. At this stage it seems reasonable to conclude that although the additive factors method holds promise for investigating possible differences between mental processes of retarded and nonretarded individuals, future research must first address the substantive issue of whether subjects in comparison groups are operating in a comparable way. This may be a matter of the extent to which participants are practiced beforehand. There is evidence from studies of nonretarded persons that the composition of processing stages can change as a consequence of practice (Sanders, 1977), so that this variable could well be of critical importance where retarded participants are involved. As yet insufficient attention has been paid to the influence of errors on the speed with which a response is made in this type of experiment. Error rates have been reported for groups only, and there may well have been considerable individual differences in this regard, especially in retarded groups. Harris and Fleer (1974) reported average error rates in their first session of 11.9% for mildly to moderately retarded subjects and 3.6% for nonretarded subjects, so that some retarded subjects may have memorized material less effectively. Pachella (1974) has discussed statistical approaches to the error problem that might provide a starting point for future research. Error rates have also been found to increase with larger positive set sizes among all subjects, but particularly among retarded (Harris & Fleer, 1974; Maisto & Jerome, 1977; Silverman, 1974); it is possible that this may reflect group differences in encoding and/or response strategies. In a recent unpublished experiment (varied set procedure) C. Doyle found that whereas among nonretarded subjects set-size/CRT functions for positive and negative sets were approximately parallel, this was not the case among mildly retarded subjects. For smaller sets of one and two items, negative responses of retarded subjects were markedly slower than positive responses, this difference decreasing as set size increased. Thus, when five or six items were involved, CRTs for positive and negative sets were much the same. For these larger sets retarded subjects also made many more positive errors; in other words, they failed to recognize that test stimuli belonged to the positive set. However, errors of commission associated with the negative set were extremely low. Although Dugas and Kellas (1974) did not report error rates for separate sets, their results also suggest nonparallel functions for positive and negative sets, these functions converging as set size approached four items. It is possible, therefore, that retarded subjects in this kind of experiment have been switching to different strategies when the set size involved became fairly large-and so perhaps nearing the limits of short-term memory span.

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IV. CHOICE REACTION TIME (CRT) A. Background: Correlational and Comparative Studies of the Role of Motor Factors Following the finding by Distefano, Ellis, and Sloan (1958) of a significant positive relationship between mental age and motor proficiency there has been considerable research activity investigating the contribution of response processes to the generally slower performance of retarded persons on perceptualmotor tasks. In an early study Dingman and Silverstein (1964) concluded that the greater portion of variance of both simple and complex RTs was due to intelligence-related differences in motor proficiency, since controlling for the effects of motor disabilities eliminated the correlation between intelligence and RT. Knights, Atkinson, and Hyman (1967), on the other hand, found that this correlation was unaffected after controlling for motor disabilities. Groden ( 1 969) attributed this discrepancy to differences in the tasks used in these studies. While Dingman and Silverstein (1964) had required subjects to tap a finger between two targets set apart, the task used by Knights et al. (1967) merely involved finger oscillation. Groden suggested that, since the former task apparently involved a greater degree of perceptual-motor coordination, it was likely that problems of perceptual-motor coordination rather than motor disability were implicated in the relationship between intelligence and RT. This hypothesis was supported by his finding, using tasks that varied in the degree of perceptual-motor coordination involved, that the relationship between intelligence and RT was affected only when RT effects on a task requiring complex perceptual-motor coordination were partialled out (Groden, 1969). As the ensuing discussion will reveal, subsequent comparative investigations of RT in retarded and nonretarded samples have tended to support Groden ’s interpretation of the correlational studies. Berkson (1960a,b,c) appears to have been first to try to isolate the cause of slowed RT among retarded persons in terms of a specific locus within an information processing system. Simple RT when the subject had only to lift a finger in response to the onset of a stimulus light was compared with timed performance when the subject had to lift a finger and then turn a knob through a prescribed angle (Berkson, 1960~).The significant interaction obtained between intelligence and response complexity, together with the absence of any interaction between intelligence and number of stimulus alternatives (Berkson, 1960b), suggested the conclusion that slowness did not involve factors governing either the speed of stimulus identification or planning a response, but motor components responsible for “initiating and executing movement. Evidence outlined in this article suggests that Berkson was only partially correct; limitations to motor stages assumed to operate later within a sequential process may contribute to slower performance to some extent, but the principal limiting factors involve ”

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earlier central processes that determine the timing of action, as discussed above in the section on simple RT (Section II), as well as which response is selected from among various alternatives. In line with this argument, the task used to examine response complexity in Berkson ’s study appeared to involve significant central processing components associated with both stimulus discrimination and stimulus-to-response translation (Nettelbeck & Brewer, 1976).

B. Varying Choice Two experiments by Lally and Nettelbeck (1977) have compared choice reactions with varying stimulus-response alternatives (lights-keys) for mildly retarded and nonretarded young adults. In one experiment a separate finger was used to respond to each of the different stimuli involved, so that response alternatives increased with two, four, six ,and eight stimulus alternatives. Mean CRT in both groups became slower as alternatives were increased, but the effect was much more marked in the retarded group. CRT data for both groups were well fitted by Hick’s Law (Hick, 1952), the slopes of regression lines corresponding to information processing rates of 3.7 bits per second among retarded subjects, and 5.7 among nonretarded subjects. Error rates in both groups were negligible. For the second experiment, which involved the same subjects as the first, the stimulus lights were arranged in a semicircle equidistant from a “home” key. To respond, a subject first released the home key (“decision time”), then moved a short distance to depress the key adjacent to the active stimulus light (“movement time”). The same index finger was used to respond on every occasion, irrespective of the particular light activated, or the number of alternative lights involved. In this task decision times for both groups increased with stimulus alternatives, as described by Hick’s Law. Once again the effect was significantly greater in the retarded group. On this occasion processing rates were 6.2 and 9.1 bits per second for retarded and nonretarded groups, respectively. Comparing these results with those from the first experiment, it seems that reducing the necessity of selection among response alternatives improved the rate of processing in both groups, but influenced retarded subjects more in this regard. The slopes of movement timehncreasing choice functions in the second experiment were close to zero for both groups, as one would expect if subjects made the choice between stimulus alternatives before moving to turn off the stimulus light involved. However, the intercept values to these functions reflected the considerably slower movements of retarded subjects, the difference between the groups being 160 msec. There was only a small difference of 50 msec between intercept values for decision time functions, the retarded group being slower. Lally and Nettelbeck’s (1977) results are in line with Bruinink’s (1974) conclusion that retarded children are more impaired with regard to fine than gross

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motor abilities, but extend that conclusion to include retarded adults. Their results do suggest that some small difference between retarded and nonretarded RT can be attributed to the actual action involved-in this case lifting a finger to release a key. However, the major difference seems to be related to perceptual and decision processes. Where more gross movement is involved then slower performance may reflect decisions responsible for guiding movement. When fine motor activity is required, however, the influence of central factors determining response selection is most marked. Compared to nonretarded subjects the retarded are particularly affected where selection between alternative responses requires that specific fine finger movements are activated in response to particular stimuli, presumably reflecting processes whereby a stimulus is translated into action. In the next section we review a number of studies in which this aspect of processing has been examined.

C. Discrimination Factors Mulhern and Baumeister (197 1) have demonstrated that limitations in processes linking stimulus to response lengthen the CRT of mildly retarded young adults. They manipulated the compatibility of stimulus-response arrangements, compatibility being “high” when symbols identifying stimulus alternatives were consistent with those identifying response keys, and ‘‘low’’ when they were not. Compared with nonretarded subjects, CRT of retarded subjects was slowed relatively more by the incompatible arrangement. However, even when stimulus-response arrangements appear highly compatible, central translation processes are less effective among retarded than among nonretarded persons. Some of the factors influencing stimulus-response translation have been examined in a recent series of studies in which a layout of the eight stimulus lights was always compatible with eight response keys (Brewer, 1976, 1978; Brewer & Nettelbeck, 1977; Nettelbeck & Brewer, 1976). Response requirements remained stable throughout, but in different conditions some change was made to the stimulus array. Thus, in the first study (Nettelbeck & Brewer, 1976) the eight stimulus lights were arranged either immediately above the reaction keys (close condition), or removed to a distance of 2.8m to the front of the subject (distance condition). A white line down the center of the display divided it into two rows of four lights. In another experiment this line was either present or removed (Brewer & Nettelbeck, 1977). CRTs of mildly retarded and nonretarded young adults were compared. The principal findings from these studies have been replicated a number of times. These were; 1. For both groups, reactions involving ring and middle fingers were slower than those for index and little fingers; this effect was significantly more pro-

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nounced among retarded subjects in the close condition, and even more so in the distance condition. 2. In both groups reactions were faster if they were repetitions of the response in the preceding trial (repetition effect), but this effect was also significantly more pronounced among retarded subjects. Particularly among retarded subjects, sequential effects were not restricted to repetitions of the previous trial since proximity effects were also apparent-that is, CRTs were faster in trials where the position of the stimulus and response was adjacent to that in the previous trial and became slower as the position of the stimulus and response in the ongoing trial was further removed from the position of the previous trial. 3. In addition to repetition trials certain other features of the experimental situation were particularly salient for retarded subjects, in that CRT was significantly faster where these features were involved. Such features were the lights at the end of the stimulus array, and the presence of the center line. Removing this line did not appreciably affect performance of nonretarded subjects, whereas CRTs of retarded subjects to stimuli at the center of the display increased sharply. Furthermore, the presence of the center line together with a repeated trial resulted in faster average CRT among retarded subjects than was the case when either of these two conditions applied separately (Brewer & Nettelbeck, 1977). Control experiments established that only minor aspects of performance could be attributed to peripheral motor factors (Brewer, 1976, 1978), and it was concluded that the much slower CRT of retarded persons reflects slower processes by which a stimulus is translated into the appropriate response. The importance of processes associated with stimulus-response translation was confirmed by an examination of error data collected from these and other experiments. Brewer and Nettelbeck (1979a) reported that when the stimulus display was adjacent to the response keys, error rates for retarded (3.7%) and nonretarded subjects (3.9%) were similar. Retarded subjects made more errors than nonretarded subjects, however, when the stimulus display was at a distance from the subject (5.7 and 4.9%, respectively). Furthermore, this effect was particularly marked when subjects were required to respond with ring and middle fingers. In other words, when the task was more demanding in terms of the processing associated with stimulus-response translation, the accuracy of responding by the retarded subjects declined. Brewer (1978) has further demonstrated that only a very small part of the between-group CRT differences can be attributed to peripheral motor components and that central aspects of processing are the principal determinants of CRT performance. He compared CRT of mildly retarded and nonretarded adults when eight stimulus lights were adjacent to the response keys, with a condition where the fingers used to respond were directly stimulated by vibrotactile keys, thereby

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linking stimulus and response directly and greatly reducing the central processing required. The main outcome was very clear; whereas CRT differences between retarded and nonretarded subjects in the lights condition were as already reported, CRT of retarded subjects was reduced to within about 40 msec of that of nonretarded subjects by directly stimulating the responding finger. Sequential effects virtually disappeared, and CRTs for the eight fingers used to respond were very similar. The small difference between the groups in the vibrotactile condition is similar to the difference of 50 msec between the intercepts of the decision timehcreasing choice functions for mildly retarded and nonretarded groups found by Lally and Nettelbeck (1977), and referred to in the previous section. While this duration may reflect differences in the neuromuscular control of finger movement, it is clear that slower central processes are the main contributory factors to slower CRT among retarded individuals. Kirby, Nettelbeck, and Tiggemann (1977) emphasized central processes at the level of response selection by requiring that subjects use different fingers on different occasions while responding to the same stimulus set. Thus, in a twochoice task (lights) subjects responded either with both index fingers or with the index and middle fingers on the preferred hand. It was assumed that the discrimination required between responding fingers was greater in the second condition. Results showed a marked interaction between intelligence and response requirements; mildly to moderately retarded subjects were slower when fingers on the same hand were involved and in this condition showed a strong repetition effect. Nonretarded subjects, however, remained unaffected by these varying response requirements. A recent unpublished experiment by Kirby, Nettelbeck, and Western has demonstrated the relative importance of stimulus and response components within the same setting. Performance of mildly retarded and nonretarded adolescents in a four-choice task (lights) involving the index and middle finger of each hand (Condition 1) was compared with performance in three other conditions: Condition 2: the four stimuli were embedded within a row of eight stimulus positions, the outside two at each end never being activated; Condition 3: the four responding keys were embedded within an array of eight keys so that all eight fingers rested on keys but only the four central keys were ever required; Condition 4: the stimulus conditions in 2 above and the response conditions in 3 above applied. When compared with Condition 1 , retarded subjects were slower in Condition 2 and even more so in Condition 3. Nonretarded subjects remained relatively unaffected by any of these manipulations. This result confirms the contribution

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of both stimulus discrimination and response selection to CRT, but suggests that the latter requires more central time than the former. This conclusion is therefore in line with findings with nonretarded populations in other contexts (Welford, 1980~).That retarded subjects are relatively slower than nonretarded in this regard is also consistent with results obtained by Marshall (1973) with schizophrenic patients.

D. Conclusions Taken together, these results suggest that, at least when fine motor activity is involved, the slower CRT of mildly retarded persons is largely determined by slower central processing relevant to discrimination and stimulus-response translation, while limited to only a small degree by peripheral motor deficiency. It is not clear to what extent the central factor involves slower rates of processing, as opposed to criterial aspects of performance, like the degree of caution exercised before a response is made. Brewer and Nettelbeck (1979a) have discussed evidence suggesting that some mildly retarded subjects in an eight-choice RT task spend additional time not in central response selection but in confirming by visual checking that the response to be made is the appropriate one. In the next section we describe an attempt to measure a fundamental rate at which central decisions proceed, by isolating this feature from criteria1 aspects of performance.

V.

AN INDEX OF PROCESSING SPEED

A. Background It is only recently that attempts have been made to measure the fundamental speed of information processes among mentally retarded persons, in a manner that is independent from the influence of the higher level strategic activities that make RT measures difficult to interpret (Pachella, 1974). The principal characteristic of this approach is that stimulus exposure is limited and under direct experimental control, so that differences in the rate at which information is analyzed can be estimated from the accuracy of performance. The outcome of research of this kind has generally been thought to support suggestions that mental retardation in some way involves a slower speed of central processing (see, for example, Savage, 1970), although Ross and Ward (1978) have cautioned against accepting this conclusion. Ross and Ward (1978) have provided a theoretical discussion of the processes thought to be involved in the analysis of information from short-term visual storage, together with a consideration of some applications of backward masking

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techniques to the investigation of relationships between mental speed and normal mental age development, mental retardation, some childhood behavioral and learning disorders, and old age. With a few exceptions we have limited our discussion in this section to more recent research not already reviewed by Ross and Ward. The earlier work can be summarized briefly as follows:

I . A briefly presented comparison circle must be exposed for a longer duration than is required by nonretarded subjects before the illusion of gamma movement' is reported by mildly retarded subjects (Winters & Gerjuoy, 1967). 2. Mildly retarded persons are less accurate than nonretarded when reporting the number of stimuli seen in a briefly exposed array, whether items are simultaneously presented dots (Clausen, 1966; Hoats, 1971; Spitz, Hoats, & Holden, 1968) or successive flashes of light (Thor, 1973; Thor & Holden, 1969). This result has been found for different levels of numerosity and a wide range of interstimulus intervals; evidence from at least one study (Thor, 1973) suggests that it is not readily attributable to poor counting ability on the part of retarded persons. 3 . Mildly retarded subjects require longer separation between successive stimuli than nonretarded subjects in order to discriminate between successive and simultaneous presentation (Clausen, 1966; Thor, 1970; Thor & Thor, 1970). 4. Mildly retarded subjects require longer exposures than nonretarded to recognize tachistoscopically presented material (Clausen, 1966; Deich, 1968, 197 l ) , and moderately retarded subjects require even longer still (Griffith, 1960). Similarly, moderately retarded subjects have longer search times than mildly retarded subjects (Rosenberg, 1961). Libkuman and Friedrich (1972) and Friedrich, Libkuman, Craig, and Winn (1977) have obtained similar results using a poststimulus cue (Averbach & Coriell, 1961; Sperling, 1960) to designate an item to be recalled from the previously displayed stimulus array (this is termed a partial-report technique). Mosley ( 1978a) has also found that tachistoscopic recognition performance among mildly retarded young adults is poorer than that of university students, both under a partial-report procedure (recalling a single item) and a whole-report procedure (recalling one of two rows of items). Essentially the same outcome has been found using a backward masking paradigm (Galbraith & Gliddon, 1972; Spitz & Thor, 1968; Welsandt & Meyer, 1974), the interference from the backward mask producing a more marked effect among mildly retarded than among nonretarded persons. 5 . There is some evidence that rate of visual processing may increase with MA (Spitz & Thor, 1968; Thor, 1970; Thor & Thor, 1970; Welsandt & Meyer, 'Gamma movement is experienced when two circles of objectively equal size are exposed briefly but for different periods of time. As a consequence, the more briefly exposed stimulus is judged to be larger.

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1974), the performance of mildly retarded adolescents in these tasks being similar to that of younger nonretarded subjects having a similar MA. Results are equivocal, however, with some studies reporting that mildly retarded adolescents did less well than MA controls (Deich, 1968; Hoats, 1971; Spitz et al., 1968). 6. A Recent Application of a Backward Masking Procedure In several recent experiments a cumulative processing model of discrimination developed by Vickers (1970, 1979; Vickers, Nettelbeck, & Willson, 1972) has been used to investigate the speed of central processes and their influence upon the speed of reactions among mentally retarded young adults (Lally & Nettelbeck, 1977, 1980; Nettelbeck, Kirby, Haymes, & Bills, 1980; Nettelbeck & Lally 1976, 1979). This model assumes that, following sensory registration, representations of stimulus information are perceptually encoded into short-term memory. A criterion-by which is meant the level of evidence accumulated to favor one of the alternative outcomesr‘etermines when a response is made. Further encoding is then required so as to translate the outcome into a response. Some minimal time is required to complete even the simplest task since there is assumed to be somewhere in the system a discrete switching mechanism which limits sampling rate; for example, readout from initial registration into short-term storage. The unit of time limiting the rate at which these processes operate is termed “inspection time. Within this framework an estimate of inspection time is obtained by having subjects judge which of two lines of markedly different length and located side by side is shorter. This task constitutes a very easy discrimination if viewing is not restricted, it being assumed that the correct decision requires only a single inspection. However, when viewing is restricted by covering the stimulus lines with a masking figure then encoding from sensory registration is interrupted, being limited to the time between the onsets of the stimulus and masking figures. [This masking technique assumes that the processes involved are central rather than peripheral, on the grounds that the masking pattern is very similar to that of the stimulus figure, and that intensity levels used have been well above those that appear to influence performance (Turvey, 1973). However, this assumption has not been tested by rigorous experimental procedures.] Inspection time is defined as the stimulus exposure duration at which the subject’s judgment is correct on virtually every trial. By measuring the speed of reaction in this situation, one obtains two measures of discriminative performance; exposure duration is controlled by the procedure so that the measure of inspection time is separate from discrimination reaction time (DRT) which is under subject control, and hence may reflect more than one “inspection” because of conceptual factors. ”

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C. Inspection Time Nettelbeck and Lally (1976) reported correlations of - .92 and - .89 between IQ scores and two separate estimates of inspection time obtained from 10 young adult subjects. (IQ ranged from 47 to 119, seven subjects having scores below 85.) Subsequently, Lally and Nettelbeck (1977) obtained a correlation of - .80 between IQ and inspection time from a sample of 48 subjects whose IQ scores ranges from 57 to 138. Retarded subjects made more errors of judgment than nonretarded subjects at all but the very shortest stimulus exposures, at which the frequency of a correct response was near chance level for all subjects. Results from these and similar follow-up experiments suggest that average inspection time is about 100-150 msec for nonretarded subjects and about twice as long for young mildly retarded adults. There is some evidence that the finding is not simply attributable to lower mental age, since average estimates from nonretarded adults and from nonretarded children aged approximately 7, 8, 9, and 10 years appear very similar (130, 147, 142, 137, 139 msec, respectively), and only about half as long as those from mildly retarded adults (256 msec) (Nettelbeck & Lally, 1979). Saccuzzo, Kerr, Marcus, and Brown (1979) have recently addressed the issue of speed of processing in the mentally retarded using a backward masking procedure that resembles the inspection time paradigm just described. Despite differences in materials and procedural details, they have obtained results similar to those reported by Nettelbeck and Lally. Mildly retarded (mean IQ = 5 5 ) and moderately retarded (mean IQ = 47) young adults required substantially longer access to letter stimuli before recognition than did either CA controls or MA controls (aged 7 and 9 years). However, although performance in both groups of children was superior to that in the retarded groups, 7-year-old subjects required significantly longer access to stimuli in order to do the task than did nonretarded adult subjects. This result is in general agreement with a number of backward masking studies, some of which have been outlined above; and despite considerable procedural variations between these studies, they have suggested an increase in processing capacity with MA development up to about 10 years of age (Ross & Ward, 1978). Although Nettelbeck and Lally’s (1979) results are at variance with this body of work, their study is the only one in which the speed of responding has been measured as an index of strategic activity. As our discussion below of discrimination reaction time (DRT) will clarify, the form of DRTs at the different stimulus durations in this experiment suggested that nonretarded adults and children were doing the task in similar ways, although children’s responses were much slower overall. Thus, these data can be interpreted in terms of criteria1 factors, rather than as due to differences in central limitations. However, Nettelbeck and Lally’s samples were very small and their result requires replication. At this time an

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appropriate conclusion would seem to be that the precise nature of change in inspection time with increasing MA is not clear. The proposal that inspection time reflects processing speed gains some support from a correlation of - .63 between estimates of this index and the rate at which the same retarded and nonretarded subjects processed information, as measured by Hick’s procedure (Hick, 1952) in a series of RT tasks involving different numbers of stimulus-response alternatives (Lally & Nettelbeck, 1977). Inspection time has also been found to reflect the numbers of errors made by retarded persons canying out an industrial sewing task (Nettelbeck, Cheshire, & Lally, 1979).

D. Discrimination Reaction Time (DRT) When DRT measures in the studies of inspection time are examined as a function of stimulus exposure duration, different trends are seen in the DRT functions of nonretarded and retarded samples. The general pattern of DRT among nonretarded samples, including the occasion where children have been tested, can be summarized as follows: mean correct DRT, variability, and positive skewness for individual distributions all increase as the stimulus figure is exposed for shorter durations; DRTs in trials when errors are made are slower than those for correct responses. Among retarded subjects, on the other hand, means and standard deviations of correct DRTs are relatively constant irrespective of stimulus exposure duration, and skewness scores are consistently lower than those found among nonretarded subjects; incorrect DRTs are slower than correct but not markedly so. In short, DRTs from retarded subjects in these experiments have revealed trends opposite to those usually characterizing mentally retarded personsnamely, slower responding, and more variable, more positively skewed distributions of responses (Baumeister & Kellas, 1968). The differences between nonretarded and retarded groups indicate differences in response strategies. The patterns of DRT found among nonretarded subjects in these experiments can be equated with the accumulation of high levels of information (Vickers er a l . , 1972)-that is, such subjects appear to process relatively more evidence before reaching a decision, even when, as at short stimulus durations, only minimal information is registered initially. Why nonretarded subjects respond in this way is not clear. However, their DRT functions are compatible with an accumulation process that is prolonged following briefer stimulus exposures, when poorer quality information contributes smaller additions to stored information, and there is little difference between the weight of accumulated evidence favoring alternative outcomes. In these same terms, patterns of DRT found in retarded groups suggest that these subjects have adopted low response criteria. When decisions are based on

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consistently shorter sampling sequences, DRT changes less as a function of stimulus duration, times for correct and incorrect responses become more similar, and there is less opportunity for variability to develop.

E. Conceptual Factors Ryan and Jones (1975) have emphasized the implicit assumption underlying much research into the cognitive functioning of mentally retarded persons-that subjects of different intellectual levels are equivalent with respect to their conceptualizations of the task requirements. In the inspection time studies an attempt has been made to avoid this criticism by carefully training participants beforehand. Thus, training for each retarded subject has usually taken from about 1 to 1.5 hours-relatively long periods of preparation if one compares this to the degree of preparation reported in much of the published work. Rigorous criteria have been used to decide whether subjects have grasped the significance of concepts essential to the experimental task, like a distinction between longer and shorter, left and right, speed and accuracy, where and when to focus attention, and the function of a backward mask. The general success of these procedures is attested to by the findings that under a random presentation procedure only a very few retarded subjects have made any errors in occasional trials in which the stimulus figure was not followed by a backward mask, that no obvious evidence has been found of regularities in the response patterns of retarded subjects that would indicate poor understanding, and that subsequent questioning of retarded participants has suggested that they understood what was required, and have tried hard to do it. However, as Ross and Ward (1978) have pointed out, the procedure of presenting occasional unmasked trials does not satisfactorily control for some factors that might influence masking performance differentially; like inappropriate shifts in eye fixations or changes in motivation associated with tolerance of ambiguity. Although it seems reasonable to infer that slower inspection time measures among retarded groups are not simply attributable to these subjects not trying as hard as nonretarded subjects, we are less confident that retarded subjects have learned the task as effectively as nonretarded subjects. These considerations notwithstanding, it seems clear that retarded subjects in these experiments have responded on the basis of much less evidence than has usually been required by nonretarded participants. This does not appear to be a consequence of retarded subjects intentionally sacrificing accuracy for speed, since encouraging subjects to slow their reactions when making a judgment (Nettelbeck, Kirby, Haymes, & Bills, 1980), or to withold a response until a decision has been considered carefully (Lally & Nettelbeck, 1980), does not influence to any marked extent the estimates of inspection time obtained. It is possible that slower inspection times among retarded individuals are, at

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least in part, a consequence of a less efficiently registered image. Pennington and Luszcz (1975) found that mildly retarded subjects consistently reported fewer stimulus items (letters) than nonretarded CA controls following a brief tachistoscopic exposure, and Saccuzzo et al. (1979) have reported that their two retarded samples required longer stimulus exposure durations than nonretarded subjects, even when stimuli were not followed by a backward mask. This is not unequivocal evidence for poorer iconic storage among retarded persons, however. Pennington and Luszcz (1975) also found evidence that the rates of decay within the iconic storage systems of their retarded and nonretarded subjects were equivalent, and it is possible that group differences were caused by higher distractibility among the retarded participants (Krupski, 1977), rather than the consequence of some structural deficiency. In any case, a structural explanation would not of itself account for the faster DRTs of retarded subjects in the inspection time experiments. Our tentative conclusion at this stage is that, over and above the possible influence of poor registration, the apparently slower rates of processing among retarded subjects in the inspection time studies reflect a general impairment influencing the development of central executive functions that plan and control all aspects of information processing. We are in agreement with Mosley’s (1978,) suggestion that retarded individuals appear not to use efficient perceptual encoding strategies that make simultaneous input tasks manageable. Indirect support for this proposal comes from an experiment reported by Lally and Nettelbeck (1980) in which estimates of inspection time among mildly retarded subjects were lengthened by requiring a more complex response, whereas nonretarded controls were not influenced by this procedure. In other words, the performance of retarded subjects deteriorated when response selection was more demanding, suggesting the influence of central processes responsible for translating evidence relevant to the discrimination into the appropriate response. This result clearly resembles Chow and Murdock’s (1975) finding that a concurrent memory task slows the rate at which the iconic memory processes of university students proceed-an outcome which, as Ross and Ward (1978) point out, questions the usefulness of the concept of an invariant rate of perceptual processing. The function of central executive processes may be presumed to include the detection and use of subtle perceptual cues in the task situation while at the same time disregarding irrelevant information, so that training could perhaps reduce differences between retarded and nonretarded persons to some extent. However, although it is not known what effects prolonged experience with the task would produce, it is not necessarily to be expected that group differences in processing speed would be eradicated entirely. Thus, in a series of unpublished studies of changes in function that accompany increasing age L. Wenger has found that even when trends in DRThtimulus duration functions are very similar for different age groups, estimates of inspection time suggest that processing slows

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appreciably beyond about 50 years of age. On the average, estimates among subjects aged more than 70 years were about double those measured among young adults in their twenties.

VI. COGNITIVE INFLUENCES A. Background Our interpretation of the results of research outlined in the preceding sections is that central processes underlying the integration of sensory information and the choice of response, but antecedent to action, are the major components of differences in performance in tasks of the kind described; the speed with which a movement is made is a relatively minor determinant of the slower performance of mildly retarded persons. A complementary examination of the relative importance of the various processes contributing to the speed of reaction among retarded persons has been provided by Wade, Newell, and Wallace (1978). They examined the effects of manipulating response complexity on the decision and movement time components of both simple and choice RT for severely retarded and nonretarded subjects. Response complexity was defined in terms of the amplitude and precision of movement (Fitts, 1954). They required subjects to lift a stylus from a home key in response to a stimulus (decision time) and move it as rapidly as possible to contact a target of varying size and distance from the starting point (movement time). The data of Wade et al. indicated that increased movement difficulty (that is, response complexity) resulted in a disproportionate increase in choice but not simple RT for retarded subjects. They concluded that, since the choice RT situation prevented subjects from preprogramming responses as may occur in the simple RT situation (Klapp, Wyatt, & Lingo, 1974), these longer RTs presumably reflected less efficient processing at the level of response organization. Wade et al. also reported significant group differences in the movement time regression coefficients and interpreted this result in terms of the increased latency with which retarded persons made decisions with respect to error detection and correction as the difficulty of the movements increased. In summary, Wade et al. ( 1978) concluded that information processing differences between retarded and nonretarded individuals can be attributed to response parameters, although it was not suggested that response parameters alone underlie the slower performance of retarded persons.

6. Methodological Factors Our experiments (Brewer, 1976, 1978; Brewer & Nettelbeck, 1977; Nettelbeck & Brewer, 1976) and that of Wade et al. (1978) have clearly established

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that the contribution of peripheral motor factors to the longer RTs of retarded subjects is relatively minor. (By “peripheral” we mean stages that are assumed to follow more “central” translation and organization and that are responsible for the execution of action.) However, there are differences between us and Wade et al. in the emphasis given to central processes associated with stimulus discrimination and stimulus-response translation on the one hand and central processes associated with response organization and control, on the other. Although these differences in emphasis have been discussed elsewhere (Brewer & Nettelbeck, 1979b), this issue warrants further attention here since it is central to our eventual conclusions. All of these studies have been concerned with identifying those mechanisms underlying differences in information processing abilities between retarded and nonretarded persons. Yet, the experimental methodologies employed, and particularly the levels of response complexity involved in the respective tasks, have differed markedly. We suggest that it is from these methodological considerations that different positions have arisen regarding the psychological processes underlying the slower performance of retarded persons. The tasks used in our experiments (Brewer, 1976, 1978; Brewer & Nettelbeck, 1977; Nettelbeck & Brewer, 1976) have required that subjects make relatively complex discriminations between an array of stimuli and subsequently press the appropriate key in a corresponding response array. The motor response required only that one of those response keys on which the subject’s fingers rested be depressed through an amplitude of about 2 mm. Furthermore, the termination of that movement was determined by the distance through which the key could travel before reaching the resting position, and not by the subject’s cognitive processes. Klapp (1975) has demonstrated that very short movements are predominantly ballistic in nature and can be programmed in advance. It seems likely, therefore, that the motor responses involved in our CRT tasks would reflect those characteristics of very short movements that Klapp has described, particularly since the subjects did not have to control or program the termination of movements. Consequently, it would have been surprising if CRT differences had emerged that reflected differences in the programming and control of motor responses between retarded and nonretarded subjects. The demands of this CRT task made it likely that the observed differences between retarded and nonretarded populations were related to central processes associated with stimulus discrimination and stimulus-response translation. On the other hand, the characteristics of the motor responses involved in the task of Wade et al. (1978) were different from those just described. In their CRT task, subjects were required to program a relatively long movement, ranging from 7.62 to 30.54 cm, on each trial. Then, once the movement had been initiated, subjects had to make progressive adjustments or refinements consistent with terminating the movement on a target. Both movement amplitude and target width varied between blocks of trials. In other words, this task involved

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movements that were under feedback control and most likely involved further response programming as the movement proceeded (Keele, 1968; Klapp, 1975). The task of Wade et al., therefore, included significant components related both to central processes associated with response programming and to ongoing error detection and correction after the movement had been initiated. Thus, the extent to which differences in information processing capabilities between retarded and nonretarded persons are related to such response parameters should be detected using such a methodology. This argument would also seem to be applicable to those results of Berkson (1960~)that were discussed earlier.

C. Processing Differences: Specific or General? The evidence discussed in the preceding section suggests that apparent theoretical conflict regarding the contribution of response parameters to retarded and nonretarded information processing differences is related to differences in research methodologies. We have suggested that the task requirements, in terms of the relative involvement of central perceptual, translational, and response mechanisms, will shape the nature of information processing differences. Further consideration of those studies that were discussed in earlier sections supports this suggestion. For example, the manipulation of various temporal and contextual factors using measures of simple RT (Baumeister &*Kellas, 1968) and autonomic nervous system functioning (Karrer, 1966; Krupski, 1975) has provided evidence of poorly developed expectancy or preparedness for stimulus processing. Similarly, the effects of variations in stimulus intensity on simple RT have pointed to possible arousal deficiencies in retarded persons (Baumeister & Kellas, 1968). The first studies using the Stemberg recognition-memory paradigm implicated slower stimulus encoding and/or response selection (Dugas & Kellas, 1974; Harris & Fleer, 1974; Silverman, 1974) while, more recently, Maisto and Jerome ( 1977) have manipulated probe stimulus quality within this paradigm, drawing attention to the possibility of less efficient encoding of information by retarded individuals. The authors’ CRT studies (Brewer, 1976, 1978; Brewer & Nettelbeck, 1977; Nettelbeck & Brewer, 1976), in which parameters associated with stimulus discrimination and stimulus-response translation were manipulated, have emphasized slower processing of information associated with discrimination and translation. Other experimental studies using a limited exposure discrimination task (Lally & Nettelbeck, 1977, 1980; Nettelbeck e f al., 1980; Nettelbeck & Lally, 1976, 1979; Saccuzzo et al., 1979) have suggested slower perceptual processes among retarded persons. Experiments involving the manipulation of response complexity have highlighted processes associated with the programming, control, and execution of motor responses (Berkson, 1960c; Wade et al., 1978). The manipulation of response complexity in association with temporal uncertainty has emphasized the contribution of poorly developed expec-

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tancy or preparedness to the less efficient preprogramming of more complex responses by retarded persons (Newel1 et al., 1979). Thus, these studies provide evidence, consistent with the suggestion advanced here, that the performance of retarded persons is limited by the relative processing requirements of the components within the task, which may vary between experimental situations. Where evidence of a processing deficit has not been found, it is possibly the case that the experimental task has been either inappropriate to the aims of the research, or not sufficiently demanding to highlight a deficit. Taken together, virtually every distinguishable stage of an information processing system has been invoked to account for the diversity of findings in studies of timed performance-for example, processes associated with perceptual encoding or organization, central preparedness and arousal, stimulusresponse translation or response selection, response programming and control. O’Connor and Hermelin (1978) have indicated that this outcome is an inevitable consequence of the application of a distinct stage information processing model to the study of cognitive processes in association with mental retardation. They, and others (for example, Odom-Brooks & Arnold, 1976), have argued that attempts to explain cognitive handicap in terms of such a model may be misleading because all stages of a processing system interact, with activity at any one level of processing presumably being reflected at other levels. The difficulties associated with maintaining a strict serial stage model of information processing are clearly exemplified, both with retarded and nonretarded samples, by those studies using Sternberg’s additive factors procedure, which, as suggested in our earlier discussion of this method, raise the possibility of temporally overlapping stages (Maisto, 1978; Silverman, 1978; Stanovich & Pachella, 1977). Thus even though mentally retarded individuals may be characterized by some specific processing deficit, such an impairment at one stage should affect processing at all stages, as O’Connor and Hermelin (1978) have argued. Having extensively reviewed information processing research involving nonretarded participants, Sanders (1 977) has concluded that separate stages responsible for perceptual encoding, choice of response, and the initiation of action do not of themselves provide a sufficient theoretical account of certain effects of signal intensity and temporal uncertainty. He suggests therefore an additional factor termed “immediate arousal,” which can have an ovemding influence on the operation of other stages. This position is consistent with that developed in this article and it is interesting to note that recent theories about general information processing have had to invoke explanatory constructs of this kind. The evidence reviewed thus far in this article has drawn attention to processing impairments in association with mental retardation at all stages of the processing chain. It remains to be shown, however, to what degree, if any, these impairments reflect a specific processing deficit that affects the operation of all other stages. On the other hand, these findings do suggest the possibility that the nature

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and magnitude of any observed impairment of timed performance in association with mental retardation are a consequence of some central executive function that directs and controls perceptual, translational, and response organizational processes. Other researchers have also emphasized the role of executive central processes in cognitive development, particularly in relation to strategy usage in memory (for example, Butterfield & Belmont, 1977; Campione & Brown, 1978; Havell, 1970). There is, moreover, a body of evidence that points to the influence of central executive or general cognitive factors on the timed performance of retarded persons. For example, comparative studies of the speed and accuracy of responding in CRT tasks (Brewer & Nettelbeck, 1979a), the capacity and duration of a sensory storage system (Hornstein & Mosley, 1979; Mosley , 1978a,b; Pennington & Luszcz, 1975), and the rate of perceptual processing (Lally & Nettelbeck, 1977; Nettelbeck & Lally, 1976, 1979; Ross & Ward, 1978; Ryan & Jones, 1975) have all raised the question of whether the experimental tasks employed can be regarded as equivalent for both retarded and nonretarded participants. Moreover, although personal experience suggests that most retarded subjects try very hard to meet experimental requirements and seem sufficiently motivated, a number of studies have shown that the performance of retarded persons can be improved, relative to that of nonretarded persons, subject to the provision of incentives of a verbal or monetary nature (for example, Baumeister & Kellas, 1968; Hasazi & Allen, 1973). This might be particularly important where subjects from an institutional background have been used, since institutionalization has been shown to influence retarded individuals over and above the effects of any genuine intellectual deficit (Baumeister, 1968; Harter, 1967; Zigler, 1969). All of these studies suggest the possibility, therefore, that retarded persons are affected by general cognitive factors that lead them to employ different strategies or “plans of action” on the experimental tasks and, furthermore, that these strategic differences place retarded subjects at a disadvantage in terms of the levels of performance that can be achieved. The performance of retarded individuals may also be limited by a lower ability to implement-in a consistent manner-fficient strategies that govern processing operations (Ryan & Jones, 1975). This is suggested (see Underwood, 1978) by the characteristically greater between- and within-subject variability among retarded samples (for example, Berkson & Baumeister, 1967; Nettelbeck & Brewer, 1976). If some flexible executive function or overall plan that directs and controls the various processing operations does underly those processing deficiencies described, what is the nature of this “executive”? Thus far, those aspects of information processing that have been implicated-for example, preparedness, arousal, less efficient accumulation of information relevant to perceptual, translational, or response processes, strategic and motivational deficiencies-are all concepts relevant to attention (Kahneman, 1973; Moray, 1969). The identifica-

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tion of attention, or concepts related to attention, as factors underlying performance deficiencies of retarded persons is, by no means, a novel hypothesis. Numerous theories have attempted to account for performance differences between retarded and nonretarded individuals in terms of specific attentional deficits (for example, Baumeister & Kellas, 1968; Clausen, 1966; Clausen et al., 1976; Denny, 1966; Furby, 1974;Goldstein, 1942-1943; Luria, 1963; O’Connor & Hermelin, 1963; Siege1 & Foshee, 1960; Zeaman & House, 1963; Zigler, 1966). The proliferation of such theories can be seen to have derived from the range of experimental paradigms employed by researchers to examine specific aspects of attentional abilities. Consequently, although some of these theories have been particularly valuable both in accounting for the behavior of retarded persons in particular situations and in generating useful research (for example, Zeaman & House, 1963), many lack generality and predictive value.

VII. CONCLUSIONS A. Attention and Central Executive Function We suggest that the attentional deficit of retarded persons is more general in nature than has sometimes been suggested, and consistent with that concept of attention described by the theorizing of Hochberg (1970), Neisser (1976), and Norman (1976). Attention is regarded as a reflection of active, flexible, anticipatory, and strategic processes that selectively govern all aspects of information processing. Attention is not, therefore, a specific mechanism but rather a reflection of the cognitions or strategies, built up or developed from past and ongoing experiences, that select and prepare what we will perceive. In these terms, we suggest that mentally retarded individuals are characterized by an impairment of those executive processes responsible for directing attention to different aspects of the overall processing operation. In other words, the attentional problems of retarded persons relate to the selection of voluntary organizational or strategic processes which govern all levels of information processing. This position distinguishes between specific fixed features of processing systems and the executive control processes that determine the functioning of those fixed components. From the available data this conclusion appears to be inevitable, although it does have certain unappealing features. For example, it is rather general in the sense that all retarded-nonretarded differences can be described in terms of some as yet unexplicated attentional limitation. Furthermore, the prospects for ameliorating the behavioral consequencesof the handicapping condition are less obvious where the deficit is general rather than specific in nature. The contribution of central executive processes to the level of cognitive functioning of retarded individuals has also been emphasized in other contexts

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where the accuracy rather than the speed or timing of performance has been the primary concern. Studies of short-term memory in retarded persons (Brown, 1974; Campione & Brown, 1977, 1978), for example, have demonstrated that these individuals are less capable of spontaneously developing the appropriate strategic or control processes that permit new learning to occur in an efficient manner. Thus, work in that area has already progressed some distance toward elaborating a theory of control processes related to memory development. To date, however, the study of timed performance among mentally retarded persons has not considered in detail the processes of executive control involved.

B. Suggested Directions for Future Research Although the evidence we have reviewed points to limitations in the central executive functioning of retarded persons, the basis of this is at this stage unresolved. To the extent that the timed behavior of retarded individuals can be manipulated-for example, by inducing changes in strategies that govern the eventual level of performance, or by systematic training that facilitates the development of appropriate attentional control over the various processing operations-initial levels of performance may be regarded as resulting from a failure to implement spontaneously or voluntarily those processing strategies that promote efficient responding in particular experimental situations. On the other hand, should the timed performance of retarded individuals prove to be insensitive to attempts to induce strategic changes or develop improved attentional control, that outcome would suggest that less efficient or adaptive executive function is one of the structural correlates of lower intelligence. This distinction has usually been taken as evidence for a separation between function and structure. We suggest, however, that the extent to which special strategic intervention is required ultimately reflects structural limitations-a departure from the structure-function distinction, but admittedly a position that probably cannot be proved. In other words, the performance of the retarded would appear to be characterized by some basic structural limitation, although in our current state of knowledge at least, no particular aspect of the processing hardware would necessarily be implicated. We suggest, therefore, that the clarification of functional limitations on the timed performance of retarded individuals remains as the critical issue for researchers in this area. Two promising approaches for investigating this issue are:

I . The examination of possible retarded-nonretarded differences with regard to conceptual factors that influence timed performance. To the degree that between-group differences are sensitive to the manipulation of strategies or control processes, these differences reflect the nature and extent of functional limitations. In this context it is worth noting that, although experimen-

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tal subjects are generally required to meet certain learning criteria, personal observation suggests that there are some subjects who appear to develop a more complete understanding of the task than others. Brewer (1976), for example, observed that while nonretarded subjects generally demonstrated an awareness that CRT was a measure of some basic ability, such an appreciation of the purpose of the CRT task was not so apparent among retarded persons. The possible influence of such conceptual factors on the outcome of experimental research is not known, although recent research on memory in the retarded has highlighted the importance of metacognitive factors (Brown & Barclay, 1976; Brown, Campione, & Murphy, 1977; Friedman, Krupski, Dawson, & Rosenberg, 1977). It is also often the case that retarded subjects used in experimental research are a selected group, in that only those individuals meeting certain learning criteria are included. Thus, those retarded persons who consistently make errors due to misunderstanding may often be excluded from studies of timed performance. It seems likely, therefore, that the traditional research paradigms may have underemphasized important cognitive influences by concentrating on the performance of the more competent or successful retarded individuals. In the study of timed performance, the empirical demonstration of betweengroup differences in terms of conceptual factors is most likely to be contained in an examination of the speed-accuracy trade-off adopted by the subjects. As Pachella (1974) has shown, speed and accuracy are related in such a way that when accuracy is high, as is usually required in studies of timed performance, slight differences in accuracy between subjects may be indicative of substantial differences in the intentions or strategies of subjects. To date, however, studies of timed performance with retarded individuals have excluded systematic examinations of incorrect responses, generally because the number of errors was too small to permit this analysis, or because average error rates for different goups were similar. Differences in error rates between experimental conditions also have been traditionally ignored, despite the interpretive difficulties that may result from this procedure (Pachella, 1974). Rabbitt (1969, 1979) and Rabbitt and Vyas (1970) have suggested that, in order for experimental subjects to comply with the usual instructions given in a CRT task-namely, to respond as quickly as possible while keeping errors to a minimum-they must respond with increasing speed until an error occurs, detect this error, and then adjust their speed of responding to a level just above that at which the error occurred. Consequently, fast and accurate CRT performance will depend on a subject’s ability to exercise control over certain critical parameters. First, subjects must be able to detect the occurrence of incorrect responses. Second, if subjects are to conform to that trade-off between speed and accuracy that the task requirements demand, they must be able to monitor accurately the speed of their responses. Finally, to maintain the appropriate speed-accuracy trade-off, subjects must also be able to adjust or control the speed of responding within those relatively narrow

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limits that are consistent with attaining the prescribed degree of accuracy, while still responding as rapidly as possible (Rabbitt, 1979). In two experiments investigating the locus of slower CRTs in the aged, Rabbitt (1979) reported that old subjects were capable of responding just as quickly as young ones and could detect and correct errors just as efficiently. That old subjects are generally slower to respond is therefore presumable due either to less efficient monitoring of the speed of responses, or to an inability to make subtle adjustments to response speed. There have been no attempts, however, to investigate the extent to which retarded persons may be impaired in the ability to exercise these parameters of executive control. Perhaps, for example, those retarded subjects who consistently fail to meet the accuracy requirements of a CRT task are not able to recognize errors when they occur. Alternatively, their difficulty may be related to an inability to either monitor or adjust the speed of responding in order to meet task accuracy requirements. For those retarded persons who do satisfy such requirements, it remains possible that their monitoring of CRT is grossly inefficient. It may be possible for such subjects to make significant improvements in the speed of responding without further impairing accuracy. Indirect support for the possibility that the accuracy of responding of some retarded persons may be independent of speed, at least within the traditional CRT paradigms, is provided by Brewer and Nettelbeck’s (1979a) finding that there was no significant negative correlation between CRT and errors among retarded subjects. At this stage, however, this suggestion is advanced somewhat tentatively since the possibility of finding a significant correlation with these data was diminished because of the restricted range of errors made within the group. In summary, we suggest that the extent to which CRTs can be improved by manipulating the strategies of retarded persons would provide some indication of the contribution of functional limitations of the type described by Rabbitt (1979). At this stage it is not possible to say definitely that any of these parameters underlie the less efficient timed performance of retarded persons. Nevertheless, the examination and manipulation of the speed-accuracy trade-off functions for retarded individuals would appear to be a promising and necessary direction for future research. 2. The examination of the effects of systematic training or practice on timed performance. In many investigations of timed performance in retarded individuals there has been little evidence to suggest that subjects have been highly practiced on the relevant tasks. Generally, there appears to have been much less emphasis placed on practice in comparative than in noncomparative studies of information processing operations. While several RT studies have reported some practice effects

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with retarded subjects (Kellas & Baumeister, 1970; Morelan, 1976; Scott, 1971), the precise effects of systematic training or practice have not been resolved. Whether practice, or possibly even specific training, can direct executive or attentional control to the various processing operations in a more efficient manner or whether certain functional limitations are untrainable correlates of low intelligence, are questions the answers to which must await the outcome of further research.

VIM. SUMMARY An information processing approach to the study of mental events provides a framework for examining the nature of individual differences in mental abilities, focusing upon cognitive events inferred to intervene between stimulus and response. The expectation has been that this approach may advance our understanding of mental retardation in terms of processes involving the selection, transformation, and retention of knowledge. In this article we discuss the assumptions underlying this approach, including problems associated with maintaining a distinction between structural and functional properties of an information processing system. Research reviewed includes studies of the effects on timed performance of various temporal and stimulus intensity factors, and of the manipulation of the relationshp between stimulus and response arrangements. Other areas of research reviewed include the application of Sternberg’s additive factors procedure and studies of tachistoscopic recognition to the study of mild mental retardation. An attempt to measure both the speed of central processing and the influence of conceptual factors within the one experimental context is described. The general conclusion is that, while the rate of processing appears to be slower among mildly retarded persons, this may reflect important cognitive differences between retarded and nonretarded populations. Evidence derived from a diversity of theoretical positions leads to the conclusion that the performance of mildly retarded individuals is best understood in terms of a general attentional deficiency, reflecting poorly developed executive control processes that govern all aspects of information processing. This conclusion does not exclude the possibility of structural limitation, either specific or general. It is further suggested that differing emphases regarding mechanisms underlying the less efficient timed performance of retarded persons have been the consequences of differences in the experimental procedures used. Possible approaches to the clarification of the nature of various executive control processes and their relative contributions to the performance of retarded persons are discussed. Particular consideration is given to conceptual factors that influence performance, and the effects of systematic training and practice.

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Preparation of this article was supported by Grant No. A68/16972 from the Australian Research Grants Committee to the first author and by a research grant from Bunvood State College to the second author. We are grateful to Dr. S. H. Haskell for helpful comments on an earlier version. The relative contributions of the authors have been approximately equal.

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Motor Function in Down’s Syndrome FERIHA ANWAR MRC DEVELOPMENTAL PSYCHOLOGY UNIT LONDON, ENGLAND

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I. Introduction . . . . . . . . . . . . . . . . . . . . . 11. 111.

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Perceptual-Motor Functions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Slowness in Down’s Syndrome . . . . . . . . . . . . . . . . . .

V. A.

Components of “Motor-Expressive Difficulties” . . . . .

B. Proprioception VI.

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Feedback Systems in A. Vision as a Feed

System . . . . . . . . . . . . . . . . . . . . . . . .

VII . The Importance of Eye-Hand Coordination v111. Evaluation and Conclusions Practical Consideration

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INTRODUCTION

Down’s syndrome (DS) subjects are the most easily differentiated subgroup of the severely subnormal (SSN) population. They are physically distinct and genetically characterized by the additional chromosome, and the brain stem and the cerebellum are found to be considerably reduced in size. It is not surprising, therefore, that the past three decades have seen the emergence of a host of empirical research into the behavioral abnormalities of DS subjects. The present article aims to provide some experimental evidence concerning handicaps involving the kinesthetic or proprioceptive modality and to interpret the findings. From a review of the SSN literature, it seems that one of the most frequently recurring anomalies demonstrated with this type of subnormality is impairment of the 107 INTERNATlONAL REVIEW OF RESEARCH IN MENTAL RETARDATION, Vol 10

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kinesthetic or proprioceptive systems. However, disparities between general psychometric and experimental studies present a far from clear picture of this handicap. The purpose of this article is to redefine these previously observed anomalies in the light of recent experiments concerned with the motor abilities of DS adolescents. A review of the current literature suggests that the kinesthetic/ proprioceptive information system in DS subjects may not be as deficient as has been previously suggested. However, there is some evidence to indicate that DS subjects lack or are unable to utilize motor programs. It is proposed that this deficiency may arise from a lack of visual-motor integration, which seems to be evident early in development and in adulthood.

II. NEUROPATHOLOGY The primary neuropathology of DS subjects has been reported by Benda (1960), Penrose and Smith (1966), Crome, Cowie, and Slater (1966), and Cowie (1970). These researchers report that the brain stem and the cerebellum of DS

subjects are generally smaller and weigh less as compared with other parts of the DS brain and as compared with the intact brain. Crome et a f . associated the small cerebellum and brain stem with low muscle tone, an opinion also corroborated by O’Connor and Berkson (1963), O’Connor and Hermelin (1961), and a number of other empirical studies in the 1960s. Hypotonia was considered to be a major factor which contributed to the abnormal psychomotor development of those who were affected by the Syndrome. This relationship between hypotonia and motor activity will be referred to again in later sections. With respect to neurological findings, one other feature peculiar to DS is the early occurrence of senile dementia (O’Hara, 1972; Solitaire 8t Lammarche, 1966, 1967). In postmortem studies these authors found that senile changes were not evident in cases of other forms of mental deficiency at similar ages. Thus there is evidence of premature neurological aging specific to DS. The implications of these briefly summarized neurological aberrations in DS will be discussed with reference to the empirical evidence concerning perceptual motor handicaps. Their small cerebellum and hypotonic musculature implicates motor defects over and above other defects shown by non-DS subjects. The early identification of the syndrome has advanced a number of clinical and empirical observations on the developmental profiles which show that perceptual motor defects become obvious in the first year of life. 111.

MOTOR DEVELOPMENT

The literature presents little agreement on the development of perceptual motor activities in the DS child. This is not surprising, particularly in view of the wide individual variation in the course of maturation within the syndrome.

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Brouseau and Brainerd (1928) were probably the first to present an empirical description of motor development in the DS child. They claimed that response to various stimuli is usually diminished and the early clinical profile is therefore that of a placid child who squirms, kicks, cries, or wriggles less than other children of the same chronological age. Along with an inert listlessness, Brouseau and Brainerd noted the marked degree of muscular and tendon hypotonia, and they also reported the tactile senses to be diminished in sensitivity. The young DS child was found to be handicapped in distinguishing tactile qualities of sandpaper, glass, velvet, etc. Weight differences were not accurately judged by DS subjects of 5-year mental age. According to Broseau and Brainerd, reduced ability for kinesthetic, tactile, or cutaneous judgment reflects central nervous system disturbances in the sensory areas rather than a reduction of peripheral sensing capacity. These data were all based on clinical and anecdotal observations but on a large number of cases. In contrast, Engler’s (1949) statistical observations analyzed the variability in the developmental profile of DS subjects. For example, Engler provided statistical evidence to show that whereas on average the DS child will walk at 3 years of chronological age, the onset of this behavior between DS subjects ranged from 10%months to 10 years. Similarly, most DS subjects began to talk at about 4 years of chronological age, with a range from 15 months to 14 years. Over the past two decades the deceleration of early development in DS has been fairly well established. Employing psychometric scales of mental and motor development, evidence has been gained for a nonlinear regression of development (Carr,1970; Benda, 1960; Cowie, 1970; Kralovich, 1959; Fishler, Share, & Koch, 1964). That is, unlike normal development, the mental indices for DS children decrease over chronological age, and some psychomotor indices reflect a decreased performance which is even below that expected for a particular mental age. Fishler et al. reported motor growth for DS children to be close to normal during the first 6 months. Carr (1970) administered the Bayley Motor Scale to DS infants and found a sharp decline in performance from 6 weeks to 2 years of chronological age. However, whereas Carr reports lack of correlation between mental age and motor ability in DS children, Cowie (1970) assumed motor performance in the syndrome to correspond approximately with their intellectual development. Kralovich ( 1959) administered the Cattell infant scale and found no significant difference between DS and other SSN infants up to 5 months of mental age. The significant differences between DS and other SSN infants occurred between 5 and LO months of mental development. DicksMireaux (1966, 1972) also reports convincing evidence to show that motor growth is arrested in DS infants at some point during the first year. It does seem that the psychometric evidence supporting good visual motor coordination or motor behavior is convincing only for the very young DS infant. The rapid deterioration of such abilities is observed soon after the first year. Cornwell and Birch (1969) and Cornwell (1974) have provided corroborative

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evidence for the better performance by younger DS subjects on eye-hand coordination and self-help skills. Nevertheless, these authors note that with increasing age there is a deceleration of finer, visual and motor manipulative skills as these are required to meet age-graded norms. Dalton, Crapper, and Schlotterer (1974) tested short-term visual retention on a delayed matching task. Their results also indicated that older DS subjects make more errors than younger DS or other SSN controls. In conclusion, the nonlinear trend noted in motor development could be attributed to the following causes: 1. Psychometric measures which have been developed and standardized on normal children may be insensitive to the particular kinds of neuromotor deficits of the DS subject. After all, the initial observations are of a rather docile and passive child. Perhaps more sensitive scales may reduce this variability and afford early detection of syndrome-specific defects. 2. Neuropathological evidence has been found which favors the early occurrence of senile dementia or Alzheimer’s Disease in DS (Solitaire & Lammarche, 1966; O’Hara, 1972). These authors have recommended that histochemical and morphological features of aging and their behavioral correlates should be studied in younger DS subjects to determine the relation of performance potential to the unique decline of the DS nervous system.

It must be pointed out, however, that the generally observed regression over age on motor tasks may not be a unique feature of DS. Possibly other subgroups of the SSN population may show a similar trend. The early identification of the DS abnormality affords studies of developmental trends which are possible only retrospectively in other children who later become classified as SSN. It has generally been assumed that a relationship exists between mental age and motor proficiency. Hence SSN groups are usually compared with a control group of normal children matched for mental age. For example, earlier work clearly demonstrated that reaction time was correlated with mental age, when chronological age is held constant (Tizard & Venables, 1956; Scott, 1940; Pascal, 1953). Scott’s finding that bright school children have faster reaction times than dull children in the same class and of the same chronological age would find much support from the subsequent voluminous research on perceptual-motor profiles or normal development which effectively correlate with mental age rather than chronological age. The exception to this “rule” seems to come from studies on DS subjects. Even when these subjects are matched on chronological and mental age with other subgroups of the SSN population, they tend to show greater abnormalities on perceptual-motor tasks. Thus within the SSN population, mental age-matched groups on standard psychometric indices may still yield qualitative differences on motor tasks.

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Since the DS subjects have been found to differ from both normal and other SSN subjects matched for mental age, low mental age, per se, cannot be used as explanation for the usually observed impairments of motor skills. Furthermore, the developmental profiles indicate that the motor expressive difficulties may increase with age in DS. Posture, gait, and limb movements continue to be clumsy into adulthood. In the following sections an overview of studies which have isolated some perceptual-motor handicaps which are specific to DS adolescents and adults as compared with other SSN groups is presented.

IV. PERCEPTUAL-MOTOR FUNCTIONS One of the frequently used paradigms for assessing motor control has been reaction time (RT). Tasks that require rapid short movement lend themselves easily to the experimental situation and appeal to most subjects. As a result, RT paradigms have a long-standing history in the study of information processing during voluntary movements (Woodworth, 1938). The task requirements are not nearly as simple as they seem. The subject who must respond as quickly as possible to the external stimulus has to make a number of decisions about selection and execution of movement. The stimulus has to be encoded and associated with the tasks requirements. From the literature on normal adults there is evidence to indicate that decisions regarding response selection and response preparation require time which covaries with the complexity of the task (Klapp, 1976). The time taken to prepare or select the response is considered to reflect “response programming time” (Kerr, 1978; Stelmach, 1978). According to the proponent of motor learning theories, ‘‘response program” refers to the sequencing of movement components prior to the response movement execution. Presumably such programming occurs centrally in the central nervous system. Response execution time, or movement time, is also known to be affected by task complexity (Fitts & Peterson, 1964; Ellis, 1973; Kerr, 1976) and across subjects initiation time and movement time within a given task are not highly correlated. A fast initiation time does not predict a fast movement time (Henry & Rogers, 1960). In studies of RT in DS subjects, the movement initiation and execution times together have generally been considered as an index of RT.

Slowness in Down’s Syndrome In contrast to apparent contradictions in other domains, one of the most consistent findings with DS subjects has been their slow RTs (Belmont, 1971; Berkson, 1960a,b,c; Hermelin, 1964; Hermelin & Venables, 1964; O’Connor & Berkson, 1963; O’Connor & Hermelin, 1961; Wallace & Fehr, 1970). Most of these authors have proposed a connection between slow motor speed and muscle tone.

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A seemingly contradictory result is given by Astrup, Sersen, and Wortis (1967) who found no RT differences between DS and other mental age-matched SSN subjects. However, these authors do report a greater degree of motor retardation in DS than in other SSN subjects. Notwithstanding the prevailing finding of slower RT for the Syndrome, there are some important considerations of antecedent controls. The pioneer studies of Berkson ( 1960a,b,c) recognized the complicated processes involved in RT measures and attempted to isolate the perceptual, central, and motor phases of RT. Berkson found no relationship between IQ and the length of time a visual stimulus had to be exposed in order to be recognized. Thus slower RTs cannot be attributed to visual duration thresholds, which must surely be one of the factors affecting decision time in response selection. However, Berkson did find mental age to be related to functions involved in the initiation and execution of the movement response. That is, if the number of lights were changed but the required response remained the same, then no interaction of mental age and task could be observed. However, when the stimulus was constant and the complexity of the movement response was varied, then SSN subjects were significantly impaired. Furthermore, DS subjects were significantly more retarded in speed on simple and complex movements than the undifferentiated SSN subjects matched on mental and chronological age. It thus seems that DS affects RT even where IQ is controlled. Hermelin and O’Connor (1961) and O’Connor and Hermelin (1961) had found that differences between stimuli usually need to be emphasized before they are perceived by the SSN subjects. This impaired discrimination ability led to the hypothesis that some degree of uncertainty and longer RTs may result when both the warning stimulus and RT signal are in the same modality rather than when they differ. This hypothesis was confirmed (Hermelin, 1964) for DS and other nondifferentiated groups of SSN subjects matched for mental age. Modifications of time interval between warning and reaction signal did not lead to improvements in RT (Hermelin, 1964). The significant finding of this study was that in contrast to results usually obtained with normals and other SSN subjects, DS subjects responded relatively faster to light than to sound. The slowness in response to sound was more marked when both warning and reaction signal were in the auditory modality. Clausen (1968) has also suggested that for DS subjects some combinations of sensory perception and motor speed might be particularly impaired. The particular disability of the auditory motor integration has also been observed in discrimination experiments (Zekulin, Gibson, Mosley & Brown, 1974) and has been offered as an explanation for the difficulties in spontaneous articulation in DS children (Dodd, 1976). Wallace and Fehr (1970) used an auditory stimulus and reported significantly longer RT latency periods. However, these authors differed in their interpretation from Zekulin et al. and suggested instead that development of motor set, drive potentials, and motor impulsivity differences contribute to the longer RTs in DS subjects.

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Pragmatically, the slow RTs for DS corroborate clinical observations of their poor gait and habitual clumsiness. However, the particularly retarding effect of the auditory stimulus on RT is interesting. What is so peculiar about auditory motor integration in DS? Berkson’s (1960) study, mentioned earlier, had measured visual threshold effects on RT and had not found DS cases to be particularly handicapped in this respect. It would be a relevant question to ask whether there is an imbalance of the auditory threshold that covaries with maturation in the DS subject. However, there is some anecdotal evidence to suggest that auditory thresholds may not be retarded. Zekulin et al. (1974) have shown that in a peg placement task the auditory modality shows a greater susceptibility to distraction than the visual modality. McDonald and MacKay (1974) also report the proactive interference of an auditory stimulus on recall by DS subjects. These studies suggest lowered auditory thresholds, thus the previously reported longer RTs for an auditory stimulus must be due to factors other than delays in perceiving the signal. It is important to note here a study by Pick, Pick, and Klein (1967). These authors found that visual and proprioceptive localizations attain precision early in normal development and show no further improvements from 9 to 16 years of age. However, auditory localizations (i.e., pointing without visual feedback from the hand to an auditory stimulus) still improve considerably over ages 9 to 16. In such tasks the modality of response was proprioceptive and the stimulated modality was audition, and effective tasks execution thus required perceptual integrations or coordination between these two modalities. It could be concluded that the development of auditory-motor integration occurs later in normal development and because of the early occurrence of senile dementia, this kind of integration may remain permanently retarded in DS. Thus, despite considerable variability in experimental parameters, the RT paradigm provides considerable evidence for the “slowness ” of DS subjects. The visual and auditory stimulus evokes slower RTs which are probably not due to raised thresholds for the respective modalities. It is suggested that the information processing system required to make the discrete response is at fault. Within this context auditory-motor perceptual integration is at a greater disadvantage than visual-motor integration. Accordingly, ballistic movements to an external stimulus are slow in the DS subject. However, what is still not clear is whether delays in the time to react are due to the programming time prior to the onset of movement (response preparation) or due to response execution. The former would involve decisions of sequencing, direction extent, and torque of movement; thus effective or ineffective perceptual integration will influence this time (Kerr, 1977). However, the effectiveness of perceptual integration may also affect movement time, and it has been suggested by Schmidt (1977) that in motor tasks normal subjects may make two possible kinds of error: (a) Errors in response selection. This is a kind of error which, according to Schmidt, would result from improper perception of the state of the environment, or from im-

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proper perception of the subject’s limb positions or orientation in space prior to response selection. If the RT delays in DS subjects reflect incorrect response selections, then the slow RTs could be conceived as being due to missing the key or bar press and then correcting the error. From the literature on normal adults there is evidence to indicate that such corrections from feedback are possible only after a delay of at least one reaction time (Schmidt, 1977). Thus in case of an incorrect response selection, the correction cannot appear until the movement has been completed. The implication is that in RT studies the movement must be planned before it began. Not only normal, but also SSN subjects might be prone to this kind of error. However, the particularly low arousal levels reported in DS subjects by Hermelin (1964) and Johnson and Olley (1971) would contribute to sizable lags in dealing with feedback regarding an incorrect response. Response error information of the type suggested would yield valuable information in this regard. (b) Errors and delays in response execution. Even if the response selection is correct, errors may occur because the motor system fails to execute the response properly (random deviation during movement) and/or it takes longer to execute the motor program. DS subjects have been reported to have a lowered muscle tone (O’Connor & Berkson, 1963). This abnormality may affect response execution and thus contribute to the RT delays as has been suggested by O’Connor and his colleagues. This aspect may be isolated specifically in RT tasks by measuring the execution time alone as divorced from initiation time as has been done in adult motor control studies (Klapp, 1976; Schmidt, 1972, 1977). If it is found that delays in RT tasks in DS subjects are clearly due to the execution time and not initiation time, then it could be assumed that even discrete movements in DS are guided to a large extent by immediate proprioceptive or visual feedbacks. It has already been proposed (Frith & Frith, 1974) that in tracking tasks, DS subjects do not make use of motor programs but rely on immediate feedback. The hypotonic musculature of DS subjects has been considered as an explanation for the longer RTs. O’Connor and Hermelin’s (1963) interpretation was that as lowered muscle tension is associated with longer RTs (Kirman, 1951), hypotonia in DS would result in poor muscle tension and correspondingly slower reactivity. It would be a reasonable conclusion to draw, that hypotonia or peripheral insensitivity may be implicated if long response execution times are recorded. However, the RT delays could be primarily due to the initiation time (i.e., the subject is slow in processing the information) or errors in response selection (i.e., the subject selects an incorrect response and then makes the necessary correction). DS subjects are known to have a small cerebellum in proportion to other parts of their own brain and in comparison with a normal brain (Crome et al., 1966). Motor programs have been reported to be a function of the cerebellum (Evarts, 1977), hence its impairment in the DS population has been used as an explanation for the lack of motor programs or strategies (Frith & Frith, 1974).

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The RT paradigm does not allow conclusions regarding (a) whether or not DS subjects use motor programs and/or (b) whether or not they make effective use of their proprioceptive feedback systems to guide the response. Both these strategies involve perceptual integration across modalities. If a motor program is used then perceptual-motor integration or information processing would occur before the movement is executed. Cross-modality integration between vision and proprioception would be required even if the hand remains under the control of immediate proprioceptive feedback during movement. Experimental evidence does suggest that visual perception is not particularly deficient in DS subjects (Berkson, 1960a,b,c; O’Connor & Hermelin, 1963). Experiments which will be discussed later on target localizations in the absence of vision suggest that DS subjects can effectively use proprioceptive kinesthetic information to guide movement. Thus the “slowness” of DS subjects must be due to deficits in collating and integrating information across modalities. The retardation of perceptual-motor functions in DS encompasses a far wider range than the RT paradigm. The following section outlines behavioral research on the problems of perceptual discrimination where speed is not a necessary component but sensory-motor integration is. The purpose of the following sections will be to elucidate briefly some issues of intra- and intermodality integration. Intramodality integration refers to the coordination or collation of perceptual information within the same modality. Intermodality integration refers to the collation of perceptual information across modalities.

V.

INTERMODALITY AND SENSORY-MOTOR INTEGRATION

A favored approach to the study of perceptual abilities involves comparison of DS and other nondifferentiated SSN subjects, matched for mental age and for

chronological age, on performance in separate intramodal tasks. Gibson (1978) presents a comprehensive summary of this area. In the present review only some pertinent studies which report defective abilities in the motor response area are discussed. The significance of research on discrimination reproduction and copying tasks is its contribution regarding perceptual-motor capacity differences. However, as will be discussed later, the roles of the peripheral and central nervous systems have not always been clearly differentiated. One of the first studies on perceptual discrimination in DS was conducted by Gordon (1944). Gordon compared DS subjects with mental age-matched normals on the execution of a tactile discrimination task. It was found that whereas normal children showed tactile discrimination efficiency, the DS child tended to be inferior on tactile or stereognoitic discrimination tasks but equally good on visual discrimination tasks. Similar findings of poor tactile or motor discrimina-

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tion have been reported by Girardeau (1959), Rude1 (1960), and Serson, Astrup, Floistad, and Wortis (1970). Knights, Hyman, and Wozny (1965) report results which indicate that tactual perception in DS is inferior to that of normals and other retardates. In a study which isolated perceptual factors and memory and motor factors, Hermelin and O’Connor (1961) also found corroborative results. Normal, DS, and matched SSN subjects were compared on matching, recognition, copying, and reproduction of simple figures which varied in direction and proportion. No group differences were observed when the subjects were required to match the figures or recognize them from memory. Thus when compared with normal children, the DS and other SSN subjects did not show visual perceptual impairment. However, in copying and drawing tasks, DS subjects performed less well than the other two groups. This result confirmed earlier findings by the same authors (O’Connor & Hermelin, 1961) which showed DS subjects to be significantly inferior in other matched SSN subjects on stereognostic recognition, but not on visual recognition tasks. In explanation, these authors attributed the defects in stereognostic recognition and reproduction to their small cerebellum and hypotonic musculature. Thus DS subjects were shown to exhibit particular strengths and weaknesses depending on the input modality. Kennedy and Sheridan (1973) also compared DS and matched non-DS groups on a shape-matching task using visual and tactual channels. The DS subjects were found to be superior on only the visual to visual matching channel. That is, advantageous intramodality facilitation was observed for only the visual channel. Coleman (1960) had also reported that visual perception proficiency did not differ obviously between DS and other SSN subjects. However, the picture of deficient tactile or motor performance is not entirely free from seemingly contradictory results. For example, Komiya (1973) found no difference between DS and other SSN subjects on simple figure copying to time limits. Belmont (1971) found DS to be inferior in size, form, patterning, and texture type tasks, but reported no modality-specific deficit. Studies on a variety of motor tests have noted a general relation between mental age and motor proficiency (Ellis & Sloan, 1957, 1958). Tests of tactual perception and motor skills have demonstrated that SSN subjects are considerably poorer than normal subjects matched for mental age. It is concluded that for the particular etiological classification of DS the results on motor abilities have not so much been contradictory but have merely yielded very variable results (Gibson, 1978). The reasons for the apparent inconsistencies are resolved when one considers the methodological issues. First, the age range has varied considerably across studies of DS, and literature has already been reviewed which shows that age effects are particularly significant in this; and second, the motor tasks have not only been ill defined, but the variety of tasks employed have been very diverse. Researchers have failed to isolate the tasks which require a considerable amount of cognitive ability from those that do not.

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Knights, Atkinson, and Hyman (1967) found that a discrimination demanding the manipulation of concepts such as “rougher than” or “bigger than” was often beyond the grasp of DS subjects as compared with other mental age-matched SSN controls. These authors have argued for a conceptual handicap in DS subjects as they found no special deficiency of motor functions. Penrose and Smith (1966) had also proposed that DS subjects cannot make effective discriminations between weights of similar size and shape merely because they do not comprehend instructions, and Stedman and Eichorn (1964) confirm the inferior performance on the symbolic test item in psychometric profiles. Recently, Cornwell (1974) also concluded that DS subjects reveal severe limitations in concept formation, abstraction, and integrative abilities. The separation of motor components from conceptual functions is not an easy problem. Knights et al. employed strictly motor-based tasks such as maze coordination, hand steadiness, keyboard tapping, reaction time, and dynamometer, and found no significant differences between DS and other mental age-matched SSN subjects. There is also some evidence however that the DS are deficient in motor skills on tasks that are relatively free from conceptual components (Anwar & Hermelin, 1979; Frith & Frith, 1974). Frith and Frith (1974) found DS subjects to be less able than mental age-matched SSN and normal subjects on simple pursuit rotor and finger tapping tasks. These authors proposed that the motor difficulty of DS subjects were a result of an inability to select or execute motor sequences. It was contended that both pursuit rotor tracking and tapping tasks require the utilization of motor programs which release the subject from his initial dependence on feedback by which the hand is under the immediate control of the eye. Indeed, there is merit in this differentiating motor output hypothesis and some explanation for the inability of DS subjects to use motor programs will be offered in the light of the experiments by the present author on target localizations and the role of visual and proprioceptive feedbacks. Experimental evidence from O’Connor and Hermelin (1961) and Kennedy and Sheridan (1973) on perceptual discrimination suggests that the use of visual information is not particularly retarded in DS subjects. The following discussion analyzes the motor components of a perceptual-motor task.

A.

Components of “Motor-Expressive Difficulties”

Despite methodological differences and complexities of task requirements, the general conclusion to be drawn from the experimental literature is that the “motor-expressive’’ component in DS is handicapped (Gibson, 1978). This is a relevant and valid conclusion to draw as the DS has been found to be inferior to other mental age-matched SSN subjects on stereognostics, kinesthetic tactile shape discrimination, copying, reproducing, and RT tasks. The “motorexpressive” component is clearly evident in all such tasks. However, the sensory systems responsible for this variety of motor tasks have not been considered.

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Besides the fact that any motor task, e.g., reading, copying, writing, etc. requires intermodality integration, i.e., integration of at the least vision and proprioception, there are a number of qualitatively different information sources within the “motor-expressive” system. For example, Hermelin and O’Connor have described the perception of the shape of an object by the exploring hands in the absence of vision as stereognostic perception. This kind of perception has also been termed “haptic” (Gibson, 1966), which is a Greek term literally meaning “able to lay hold of. According to Gibson the receptive units involved for this kind of exploration would be skin, joints, and muscles (including tendons). In such a task the subject moves his hand around the object, he may “feel” the object’s contours, size, texture, etc. and try to match the haptic shape to other subsequent haptic shapes (intramodality integration) or to a visual shape (intermodality integration). Thus stereognostic has been used to mean haptic and a similar meaning has also been intended when “shape-tactile discrimination” has been used as a task description. It is obvious that such a task probably requires the collation of information from a number of dimensions, within the same modality. The term “kinesthesis” is even more ambiguous as it has been used to describe a number of behavioral responses and has often been used to mean the same thing as “motor” or “proprioceptive.” Knights et al. (1967) described maze coordination, hand steadiness, keyboard tapping, and dynamometer tasks as “motor based” or “kinesthetic.” For the present purpose only those tasks which require movement will be called motor tasks. Tasks like dynamometer hand steadiness and weight discrimination require only muscular effort as distinct from movement. The sources of information which motor tasks require will be termed kinesthesis or proprioception as they have been used interchangeably to mean the same thing. In the literature whereas proprioception has neurological connotations, kinesthesis has been used as a behavioral term to describe the “position sense. According to Howard and Templeton ( 1966) kinesthesis means the discrimination of the position of body parts and discrimination of active and passive movements of body parts-in the absence of visual or auditory information. In the present article the term “proprioception” will be used operationally to confer both the behavioral and neurological connotations. ”

”

B. Proprioception The interoceptive sources of motor information are not clearly understood and the obscurity lies in the complexity of the many systems involved, e.g., muscles, joints, Golgi tendons, etc. Either some or all have been regarded as being responsible for our sense of location and of movement. As mentioned earlier, the term proprioception has various connotations both behavioral and neurological, which are briefly summarized below. The proprioceptive senses are generally taken to include the receptor

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mechanisms associated with the muscles, the tendons, the joints, and the nonauditory part of the inner ear. A number of psychologists have speculated that, even as early as the fetal stage, the activity of the joints and muscles and the consequent proprioceptive stimulation are important in laying the foundations of the organism’s later ability to maintain equilibrium and to judge spatial relations (Montessori, 1964; Zinchenko, 1957). The extensive tactal exploratory behavior which does occur early in development led to the inference by these authors that tactal perception develops prior to, and forms the basis for, visual perception. This interpretation was reinforced by the earlier superficial observations of the young infant’s random visual behavior. However, the impressive work of Bower (1974), Bruner (1973), Bryant (1974), and Fantz (1961) has clearly shown that even very young infants are capable of making fine visual judgments. These results do not allow any conclusive statements regarding the assumption “touch teaches vision. ” However, what is quite certain is that the sense of limb position and movement of our limbs forms the basis of knowledge of the spatial position of our limbs in relation to the rest of our body-independent of vision. Sherrington (1906) coined the term “proprioception” to describe the sense subserved by the “proprioceptors,” which according to him were the deep receptors in the muscles, tendons, and joints and the receptors of the labyrinth. Consequently, this terminology begs the question of which receptors subserve proprioception. According to Mountcastle and his colleagues (Mountcastle, 1961; Mountcastle, Pogio, & Werner, 1963) it is the receptors in the joints which are mainly responsible for the sense of proprioception. These authors reported clear empirical evidence indicating how position and movement information is represented at higher levels (thalamus and cortex in monkeys). It was found that cells representing joint afferents fire at a particular rate for a particular angle of joint movement. Furthermore, the rate of firing at any one angle is a function of the previous angle of the joint. Thus the central nervous system is capable of constant “updating of the position sense by accounting for previous movements and maintaining output in a state of dynamic equilibrium. After all, the same movement is not always made from the same starting position and the system must be able to assess the difference in order to provide effective proprioceptive information in the absence of vision. Howard and Templeton (1966) present an exhaustive review of the role of joint receptors in the perception of movement sense. Cells that are excited by joint movement have also been isolated in the precentral or motor cortex (Rosen & Asanuma, 1972). Some studies on cats, however, suggest that the role of joint in the perception of proprioception is not unique (Clark & Burgess, 1975; Skoglund, 1973). A review of the neurological literature presents many changes in opinion regarding the classical role given by most physiologists and psychologists to joint receptors in the perception of movement. Whereas Marteniuk, Shields, and Campbell (19721, Marteniuk and Roy (1972), and Skoglund (1973) favor the classical ”

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position, Grigg (1976) and Clark and Burgess (1975) argue that the sense of position depends upon receptors other than joint afferents. Advances in neurology have made it possible to record evoked responses which indicate that particular classes of receptors (e.g., joints, muscles, spindles, and Golgi tendons) project via particular pathways (Goodwin, 1977). However, from his review, Goodwin concludes that such experiments still do not provide an insight into how the information from the various receptors is integrated. Apparently, there are three different kinds of receptors in the joints alone and the system is complex indeed as is the spatial sense of position. As long as neurophysiologists are unable to resolve the issue, it is tempting to adhere to the classical approach. Goodwin (1977) offers some suggestion that muscle tone may affect tension in the joint capsule which is sensitive to muscle contraction. Thus it could be conceded that the hypotonic musculature of DS may have secondary effects on this source of proprioceptive information. The proprioceptive position information is registered through kinesthesis. This is a complex kind of information obtained by the subject’s own action-it is not externally imposed on the subject. The input is not merely afferent, but reafferent, that is, contingent upon afferent output. The term in motor learning theories for such proprioception or action-produced input is “feedback. The DS subjects are generally slow, clumsy, and deficient in performance on motor and haptic tasks. To what extent is this reported deficiency due to the use, misuse, or neglect of the proprioceptive information system? This question will be attended to in the following sections. ”

VI.

FEEDBACK SYSTEMS IN MOTOR SKILLS

In general, tests of tactal perception and motor skills have demonstrated that DS subjects are considerably poorer than normal or other mental age-matched SSN subjects. Within the context of the methdological issues which may have contributed to the sometimes contradictory results, the motor disability of DS subjects is a recurring finding. When tactal, stereognostic discrimination tasks have been employed, the common finding in all studies where DS subjects have been tested has been a motor deficiency. What then are the minimum requirements which must be stipulated. The two main sources of information in general spatial tasks are vision and proprioception. Woodworth (1938) had very early suggested that any overt activity demands “obedience to two masters ”-vision and proprioception. A number of more recent studies have emphasized the importance of correlation and integration between the visual and proprioceptive schemas (Held, 1961, 1968; Held & Hein, 1963; Kay, 1970). The relative effectiveness of these two sources of feedback in DS subjects has not been extensively studied.

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According to Held (1961, 1968) accurate movements require the continuous correlation of reafferent visual and proprioceptive information systems. Held and Hein (1963) suggested that the efference copy of movement also retains information of the previously achieved results of movements in visual terms. Subsequent movement would thus be checked against a “copy” containing visual as well as motor information. Thus according to this hypothesis, the visual information resulting from movement is important during ongoing movement and in the development of motor skills. The visual information resulting from movements is fed back and compared with the visual schema based on previous movements. The concept of a “macro-strategy’’ system developed by Kay (1970) also demands a continuous reaction between input and output monitoring-an interaction which must match the varying demands of the various sources of information. If a visual schema or reference system is essential for coding aspects of limb movements, to what extent are the DS subjects handicapped in this respect. The studies which have addressed themselves to this issue have been few and are briefly discussed in the following section.

A. Vision as a Feedback System The study of Berkson (1960), mentioned earlier, had already shown that DS subjects are not particularly handicapped in visual thresholds. The following experiments are mentioned to elucidate the role of vision in obtaining and collating visual information. An early study by O’Connor and Berkson (1963) is particularly relevant in extending the explanation of poor motor performance in DS. O’Connor and Berkson studied lateral eye movements to static and changing visual displays in DS and non-DS subjects. DS subjects were found to make more eye movements under all conditions and in explanation these authors supposed that hypotonus may prevent controlled eye movements and therefore contribute to faulty attention and slower RTs. In other words, O’Connor and Berkson claimed that hypotonus may prevent controlled movements of they eyes and thereby obscure the distinction between visual discrimination and motor variables. Within this context a study by Sackett (1967) is also relevant. He found DS subjects showed a preference for the more complex visual stimuli in a visual discrimination task. Sackett thought his findings showed that DS individuals enjoy a greater potential for visual exploration as compared with other braindamaged subjects. Perhaps this “exploration” is nothing more than an inability to control eye movements and thus the subjects exhibit indiscriminate and uncontrolled movements as suggested by O’Connor and Berkson. A detailed scrutiny of the ways in which young normal and DS babies scan two- and three-dimensional patterns has been made by Claxton and Bryant (1980). The eye movements of the two groups of infants (20-30 weeks old) were photographed using infrared sensitive films. These authors report that regardless

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of whether patterns were two- or three-dimensional, DS children do not scan patterns extensively but instead tended to fixate one part or a portion of the side. The matched normal children, on the other hand, even at the youngest age scanned the pattern quite extensively, and concentrated their fixations on several parts of each figure. Furthermore, whereas the older children demonstrated a tendency to fixate the center of the pattern as well as the external contours-this did not occur in DS children of up to 30 weeks. Earlier, Warner (1935) had reported that in DS children the ability to follow a light with the eyes appears late in development. The experiments which have focused on eye movements have been few and limited. However, they do provide evidence to suggest that adult DS subjects make random undifferentiated eye movements to stimuli. Appropriate visual scanning seems to be deficient in DS development. The above findings are reminiscent of oculomotor programming disturbances observed in Dementia Syndrome (Alzheimers Disease). Hutton, Johnston, Shapiro, and Pirozzolo ( 1979) identified three types of oculomotor programming disturbances in patients with Alzheimer’s Disease. These patients were found to show (a) poorly regulated gaze patterns in contrast to normal controls, (b) persistance of previous response patterns, and (c) a hypokinetic “staring” type of gaze pattern. As has already been discussed, senility plaques have been detected very early in the DS brain, implicating Alzheimer’s Disease. There seems to be some parallel observations of the visual feedback system in DS subjects and patients with senile dementia. Further neurological and histochemical studies may reveal the nature and age at which cerebral atrophy is evident in DS subjects. What are the implications of such early sensory-motor deficiency in DS? There is extensive evidence in the literature based on animal research which suggests that visual feedback is involved in the development of early motor skills (Hein, 1972; Ganz, 1975). According to Held and his colleagues visual information about hand or limb movements is coded along with a copy of the reafferent proprioceptive information for future reference of similar movements. From the studies discussed above it would be reasonable to conclude that the intake and processing of visual information in DS subjects are deficient. There is, in addition, considerable experimental evidence to indicate that movement may be accurately executed in the absence of vision by DS subjects. For movements where visual reference is either not required or is not available, the internal source of feedback that the subject relies on to execute and correct his movements is praprioception.

B. Proprioception as a Feedback System Pointing to a visual target requires the minimum amount of conceptual/ cognitive involvement. Varied moments in space are carried out with and without visual guidance and with considerable accuracy. Reaching movements in space

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require very little attention and at times we are not even aware of whether we guide the hand visually or merely execute the movement on the basis of proprioceptive feedback alone. Such variables were controlled in an experiment on visual target localization, which employed conditions of visually guided and visually directed localizations. The former refers to an experimental situation in which the subject is allowed to see his hand while he guides it and the latter refers to lack of such visual feedback concerning hand position. Thus in the visually directed condition the subject may see the target but not his pointing hand, and the feedback that he relies on to guide the response is purely proprioceptive. Such a task is different from those previously described perceptual motor tasks, on which DS subjects were found to be deficient in the following manner: 1. Reaction time tasks have a time component and the subject is asked to point as quickly as he can. There is some evidence to suggest (Kelso & Wallace, 1978; Kerr, 1978; Schmidt, 1977) that the movement is programmed centrally prior to it being triggered and cannot be modified until the program has run its course. Thus, whereas some visual or proprioceptive feedback may be used (after the lapse of at least one RT) during the movement, proprioceptive feedback is not used to guide the response. This is in contrast to studies of target localizations where there is no time component and the subject may use proprioception to guide his response in the absence of vision, because the movement must not be planned completely before it begins. Kerr (1978) suggests that in such a condition the subject may move his hand in the general direction of the spatial location but may rely on some feedback (visual or proprioceptive) to correct his movement en route. 2. Studies on stereognostic discrimination required a number of tactile motor movements around the perimeter of shapes in the absence of vision. Thus a more complicated conceptual judgment was required than would be the case for a discrete limb movement to a spatial location. For accurate perception, the subject would have to not only collate and analyze various movements without vision but also remember the sequence of movements, and perhaps encode these as a shape (haptic perception). 3. In a discrete task such as target localizations, decisions about extraneous environmental parameters (e.g., where the visual target is in relation to the body) are probably made before the movement begins. Thus in the visually directed condition the only source of feedback for correction would be proprioception as the subject would be unable to see his hand while he localized the target. Motor tasks such as tracking mentioned earlier (Frith & Frith, 1974) require anticipation and continuous integration of visual and proprioceptive information. The same is true for reproduction and copying tasks (O’Connor & Hermelin 1961). Thus perceptual factors may not be easily distinguished from processes that contol limb movement, once the external goal has been determined. A localization task should enable such a distinction to be made, however.

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Thus a discrete goal-directed motor response in the presence of vision (visually guided) and in the absence of vision (visually directed) was studied. The subject always saw a visual target in front of him. A number of different target positions were used which were approximately “straight ahead” of the subject at arm’s length. In the visually directed condition, the subject could not see his hand while he localized the target and in the visually guided condition the subject had the opportunity to guide his hand visually to the target and receive visual knowledge of results. It was found (Anwar, 1981a) that in the visually directed condition pointing without knowledge of results, SSN subjects (i.e., DS and non-DS subjects) performed just as well as mental age-matched normals, when no external feedback was given, visual or otherwise. In the same study similar results were also found in the condition of visually directed pointing where proprioceptive knowledge of results was given at the completion of the proprioceptive response. That is, after pointing, without seeing his hand, the subject was able to feel the correct target position with the pointing hand. Thus when the amount of sensory processing was limited to the proprioceptive modality then mental age-matched normals were no better than a group of DS and non-DS subjects. Thus, in addition to the internally obtained proprioceptive feedback (kinesthesis), error information was also given to the subject by requiring him to feel the extent of his error (knowledge of results). This is a form of imposing proprioceptive information in addition to that which the subject is internally registering. The collation of such error information would require intramodality integration and DS subjects were not particularly handicapped in this respect. In three further conditions of visually directed pointing, all SSN subjects were found to be significantly less accurate than their mental age-matched normals. The conditions were: (a) when proprioceptive feedback was obtained via the other nonpointing hand; (b) when visual knowledge of results was given at the completion of the response-i.e., subjects could see the correct target position in relation to the result of the pointing response; and (c) visually guided pointing with visual knowledge of results. The conditions of proprioceptive knowledge of results will be discussed first. Practically speaking, if one were to reach for a cup on the table with the right hand, fail to touch it and instead touch the edge of the table, the proprioceptive feedback of touching the table would allow one to calibrate the error within the same movement approximately. The proprioceptive information of where the hand was and where it should be probably requires the minimum of sensory modality integration. However, if one were to feel the same error with the left hand then the error magnitude would have to be related to the central body schema for it to be effectively utilized by the other hand. In such a condition the immediate proprioceptive information is no longer relevant. For this error information to be effectively used, it may have to be coded centrally, presumably with

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vision. There is evidence to suggest that spatial information is mapped on the visual representational scheme (O’Connor & Hermelin, 1978). These authors have shown that in the absence of vision “geometric” spatial concepts are lost (O’Connor & Hermelin, 1978). Such higher order perceptual integration is apparently beyond the scope of all SSN subjects under 6 years of mental age and DS subjects are not unique in this respect. The visually guided condition requires perceptual integration of visual and proprioceptive information modalities. All SSN subjects were deficient in this simple visual-motor task as compared with mental age-matched normal children. It seemed at the time that concurrent visual and proprioceptive feedback were not easily integrated by DS and other SSN subjects. Similarly, visual knowledge of results obtained at the end of the pointing response was also not effectively used to improve pointing accuracy. Abercrombie (1970) had earlier reported from observations of drawing difficulties in SSN children that these children probably attended differentially to their visual and proprioceptive frame of reference. In other words, they cannot attend simultaneously to the two sources of stimulation. The present results on visual-motor localizationscould be considered as adequate support for Abercrombie’s observations. That is, if SSN subjects are given an opportunity to respond on the basis of just one modality, then they are just as able as normal children. It is only when they have to obey two masters, vision and proprioception, that the problem arises. Birch e? al. (Birch & Belmont, 1965; Birch & Lefford, 1963) have also cited evidence to suggest that in braindamaged subjects intermodality integration is more likely to be disturbed than intrarnodality integration. The results reported above lend support to such a hypothesis. There is some recent evidence from normal adult performance that vision does not aid the reproduction accuracy of movements which is either preselected by the subject or determined by the experimenter (Kelso & Wallace, 1978). Indeed, detrimental effects were observed when vision was concurrently present. These authors claimed that the reproduction errors reflect an overload in the limited capacity processing system if the subject has to attend simultaneously to the visual information and to the execution of the motor plan. In the visual-motor localization tasks the DS and other SSN subjects did better when they could initiate and execute the movement proprioceptively without attention to the concurrent visual stimulation. In fact, in the conditions where visual knowledge of results was given at the completion of the motor response, this feedback had a detrimental effect. That is, these SSN subjects did better under conditions of no feedback than they did under conditions of visual knowledge of results following visually directed pointing. It is tempting to speculate that this condition probably imposed an increase in central processing demands and whereas normal children were able to deal with these demands, mental age-matched SSN subjects were not able to do so. It could be that SSN subjects do not preplan the movements to

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the extent that normal subjects do; thus reliance on immediate proprioceptive and visual feedbacks to guide the response may result in the increased processing demands. Thus, when movement to a visual spatial stimulus does not require central processing of two different sources of perceptual information, DS and other SSN may be considered as a group to be no different from other mental age-matched normal children. In fact, it was found that in the absence of a visual target, “straight ahead” movements (made with a blindfold) were more accurate for the DS group than either the other mental age-matched SSN or normal children (Anwar & Hermelin, 1979). A possible conclusion from these results would be that, as an etiologically distinguished group, DS are not specifically retarded in executing such proprioceptive localizations and this would be in contradiction to the usually observed deficits in motor tasks. For example, O’Connor and Hermelin (1961) found that DS subjects were unable to make accurate proprioceptive judgments of shapes in the absence of vision. In these tasks the shapes were left in the subject’s hand for a few seconds and they were then asked to recognize these shapes visually or proprioceptively. Such a task requires from the subject a strategy to trace sequentially the perimeter of the shape with his hands. Perhaps DS subjects did not obtain the relevant information in the first place to enable subsequent recognition. From experiments at present being done there is some tentative evidence to suggest that if DS subjects’ hand movements are guided by the experimenter along a shape pattern (without vision) then these subjects are in fact more accurate than other mental age-matched SSN subjects in subsequently assessing orientation of the felt shape. Thus when attention is systematically focused on proprioceptive information, then DS subjects can effectively use this feedback in improving localization accuracy and in recognizing shape orientation. However, from tasks like pursuit rotor, finger tapping (Frith & Frith, 1974), and RT (O’Connor & Hermelin, 1961; Berkson, 1960a,b,c) there seems to be evidence to suggest that DS subjects are unable to utilize motor programs to increase performance efficiency. The following results, also on motor movement, confirm that DS subjects suffer some handicap in collating and evaluating positional information as a function of extent of previous movement information. Such a handicap may affect the development of motor programs, lack of which probably results in the previously observed deficiencies in motor tasks.

C. Lability of the Proprioceptive Information System In the above mentioned experiments on visual-motor localizations, the target positions were all straight ahead in the subject’s frontal median plane. There was some suggestion from another experiment on adaptation to visual displacement (Anwar, 1981b) that DS subjects are particularly susceptible to the visual point-

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ing positions which are asymmetrical to the straight ahead position. That is, more than other mental age-matched SSN subjects, DS subjects tend to be considerably biased in the direction of their previous movements. It is a prevalent finding in the literature that a limb maintained in one position for some time will be subsequently placed nearer to the previously held position (Craske & Crawshaw, 1974; Nachmias, 1953). Such kinesthetic movement after effects are usually explored to demonstrate the lability or instability of the proprioceptive system, that is, its susceptibility to previous states. Kinesthetic or proprioceptive information about body position is “relative” in nature. That is, a body position or movement is judged with reference to previous position or movements. As there was some suggestion that DS subjects were particularly susceptible to previous movements, the extent of the lability of the proprioceptive system was studied experimentally (Anwar & Hermelin, 1979). Measures of straight ahead judgments were recorded for DS subjects, mental age-matched normals, chronological age-matched normals, and mental and chronological age-matched non-DS subjects. Subjects were blindfolded throughout the experiment. No differences were found between groups on their first straight ahead judgments without vision. Following this period all subjects made a number of judgments to an asymmetrical position which was located at 45” toward the side of the dominant hand. All subjects pointed only with their dominant hand and head position was maintained in the straight ahead position. Subsequent to the asymmetrical pointing condition straight ahead judgments were made again and the difference between the first and second straight ahead measures was taken as a measure of the extent of the kinesthetic aftereffect. Normal subjects matched for mental age and non-DS subjects also matched for mental age showed a tendency to overcompensate for the asymmetrical pointing stimulation and their second straight ahead pointing position was slightly biased in the direction opposite to that of the previous asymmetrical stimulation. In comparison, the older normal children (matched for chronological age) did show a kinesthetic aftereffect toward the previous asymmetrical position. However, most significant was the finding that the DS subjects were consistently biased toward the side of the previous stimulation (Anwar & Hermelin, 1979). The extent of the bias was considerably greater than that shown by normal subjects. Thus from these studies on visual-motor target localizations it may be concluded that DS children can generate accurate movements to spatial locations on the basis of their internal kinesthetic or proprioceptive feedback only. These subjects were just as accurate as chronological age-matched normals on their initial straight ahead judgments. However, this reliance on and persistence of motor information also makes the system particularly labile. Thus the same sensory information which on some tasks can be effectively used by these DS subjects can also produce such extensive aftereffects that subsequent movements may become distorted. If, as suggested by Goodwin (1977), the joint capsule is

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sensitive to muscle contraction, then the hypotonic musculature of DS subjects may ‘have secondary effects on this source of proprioceptive information. Whereas the specific role of various receptors in signaling proprioceptive information must await more advanced neurophysiological evidence, the “relative” nature of proprioceptive information proposed by Mountcastle (1961) is attractive. It seems reasonable to conclude that proprioceptive information will always have to be “updated.” In contrast to vision where a subject has available to him simultaneously information on a number of stimulus dimensions, proprioceptive information from the motor system is successively obtained. Proprioceptive movement information is also relative. That is, one can accurately judge hand position at any given moment, but it is always in relation to previous positions and to other body parts. Some central mechanism must constantly account for the relative nature of proprioceptive information and yet maintain perceptual motor-orienting stability. From the above mentioned results it seems that whereas DS subjects can use immediate proprioceptive information quite effectively, this system is subject to disruption because of the nature of previous movements. The particularly reduced size of the cerebellum in DS may be responsible for such an abnormality. The limitations of the proprioceptive system would also implicate retardation in the development of motor programs. Pew (1974) and Schmidt (1975, 1976) postulated that motor programs are not represented one to one in terms of movement produced, but rather that the programs are “generalized” so that any one could reproduce a number of similar movements of a given class. This is the basis of a “schema” as postulated by these authors. However, the concept of generalized motor programs requires an additional explanation about how subjects generate the parameters before the program is executed. According to Schmidt, the parameters for the motor program are generated through a motor response schema based upon past experience with similar motor responses using the same motor programs. Obviously if the proprioceptive feedback system is particularly labile and susceptible to previous environmental demands-then the DS subject would be handicapped in developing such a schema. Thus proprioception as a reference system for “correctness” would be limited and at times even erroneous. Could vision be a corrective reference system? As proprioceptive information is relative and obtained only successively, the visual schema must surely serve to correct for any inconsistencies due to lability of the proprioceptive system as normal adults also show kinesthetic movement aftereffects (Craske & Crawshaw, 1974; Nachmias, 1953). The following results showed that visual information or a visual reference does not totally compensate for the proprioceptive lability in DS subjects. In the previously discussed experiment, the lability of the proprioceptive information system was assessed in the absence of vision as the concept of

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“straight ahead” was clearly understood by all subjects. In another experiment in which visual references were available for “straight ahead” and the asymmetrical pointing positions, it was found that whereas a visual reference system reduced the lability of the proprioceptive information for mental and chronological age-matched normal subjects (i.e., they showed little or no aftereffect), this was not so for the DS subjects (Anwar, 1981~).Thus, whereas in DS subjects visual direction reduced the amount of aftereffect, it did not affect it as much as was the case for normal children. This result may be considered as further support for the hypothesis that integration between vision and proprioception is deficient. In normal subjects, whatever the disruption may be in the proprioceptive information system due to previous pointing positions, the visual reference remains dominant. Thus, visually directed commands to the motor system probably overcome the nature of the disruption. In DS subjects the disruption of proprioceptive information remains to some extent even in the presence of vision. The following section reviews some developmental work on normal children in order to search for trends which highlight the use of visual and proprioceptive information, and the importance of both in normal and DS development.

VII. THE IMPORTANCE OF EYE-HAND COORDINATION It would be impossible to deny the importance of vision in the control of hand movements. Nevertheless, there is some evidence to suggest that very young babies (under 20 weeks of age) are unable to utilize visual feedback in order to correct inaccurate reactions. According to Bower (1974) reaching in the newborn is visually elicited or triggered and is not affected by any visual feedback received during the course of the movement. A similar observation has been reported by Bruner (1968) who noted that in reaching for a visual target the very young infants tend to close their eyes as if reducing their degrees of freedom will enable more effective execution. Bower (1974) adds that older infants can use visual feedback of the hand in order to correct inaccurate reaching. The suggestion here is that the development of a visually guided reaching relies on a maturation process which is dependent upon learning effects and a parallel growth in attention span (Bower, 1974). However, a very relevant observation is that visually directed reaching is not replaced by visually guided reaching (Bower & Wishart, 1972). Once the human infant is capable of accomplishing reaching, visual feedback of the hand is not necessary for reaching, although it may later be used to correct inaccurate reaching induced by illusions or distortions. According to Bower, the senses of sight and touch are independent and the young child learns to predict the information potential available to these senses through associative learning.

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As mentioned earlier Bruner (1968) observed that young babies tend to close their eyes when attempting to reach for an object, as if reducing the degrees of freedom they have to attend to. The comparable accuracy of DS and normal subjects in the absence of visual guidance or knowledge of results suggests that like young infants when the degrees of freedom requiring attendance are reduced then DS subjects are not particularly handicapped. However, whereas normal children learn to predict the information potential available to vision (or other senses) and develop visually guided behavior, this is not so for DS subjects. Piaget (1954) had also argued against the theory that the development of eye-hand coordination is purely a function of maturation (Gesell & Thompson, 1934). According to Piaget the development of eye-hand coordination involves a mapping of visual and proprioceptive schematas. This mapping is accomplished early in life by observing the hand within the visual field. It is often observed that once infants are able to reach for things they spend a great deal of time looking at objects which they hold in their hand (Bruner, 1973; Piaget, 1954; White, Castle, & Held, 1964). Some anecdotal evidence has already been discussed which showed that (a) DS children make very few limb movements and are generally passive and (b) DS infants make few eye movements to objects in the visual field and do not shift scanning strategies as normal infants do over age. The secondary consequences in adult DS subjects are random and nonspecific eye movements. These particular deficiencies observed in DS subjects may prevent effective development of their visual and proprioceptive schemas. Thus, like young infants, they can use proprioceptive information to guide their movements quite accurately. Proprioceptive error information can also be used to increase accuracy by DS subjects. However, the labile nature of this source of information may prevent the development of motor programs. Perhaps young infants may also show greater lability of proprioceptive information which is reduced in development through associative learning with the visual reference system. In tasks that require the use of both the proprioceptive and visual reference systems, DS subjects are deficient. For example, tasks such as drawing and copying require the coordination or transfer of information across modalities. In copying a simple geometric form such as a square, there must be a mechanism which analyzes the visual stimulus and one which transforms the visual pattern into a kinesthetic or proprioceptive code. Such integration of perceptual information determines the coordinated pattern of movement sequence from a visual stimulus. Hermelin and O’Connor (1961) and O’Connor and Hermelin (1961) reported DS subjects to be significantly less able to copy or reproduce simple shapes as compared with other matched SSN subjects. The importance of visual-motor integration is implicated in the basic development of posture and gait. For example, Fraiberg (1977) studied motor development in the congenitally blind and found that whereas static postures such as sitting or standing are delayed, other postures such as crawling and walking (which Fraiberg refers to as dynamic) are significantly retarded. According to

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Fraiberg, visual feedback is not intrinsic to motor development but vision may serve only to motivate movements. The same evidence has been reconsidered by Butterworth and Cicchetti (1978) who suggest instead that lack of visual feedback may disrupt the developmental relation between motor central processes., Butterworth and Cicchetti (1978) cite experimental evidence to suggest that DS infants who have recently learned to sit unsupported are significantly less responsive to surrounding visual movements than normal infants. On the other hand, when DS infants have recently learned to stand then they are more responsive to visual movements of the surroundings than are matched normal infants. According to Butterworth and his colleagues (Butterworth & Cicchetti, 1978; Butterworth & Hicks, 1977) postural control depends on congruence between mechanical vestibular and visual indices of postural stability. The DS child’s failure to calibrate the early sitting behavior visually might add an increment to the lag in acquisition of later postures (Butterworth & Cicchetti, 1978).

VIII.

EVALUATION AND CONCLUSIONS

From the prevailing studies with DS subjects, a hypothesis of lack of perceptual integration must remain a hypothesis. Nevertheless, the points that are relatively clearer regarding the visual and proprioceptive feedback systems may be summarized as follows: 1. DS subjects do not show any deficiency in visual thresholds (Berkson, 1960a,b,c) or visual recognition of simple shapes (Hermelin & O’Connor, 1961). However, these subjects show disturbances in visual scanning stragegies and oculomotor programming from birth into adulthood (Claxton & Bryant, 1980; O’Connor & Berkson, 1963). These disturbances may retard the development of the visual schema, thus disabling the effective use of this reference system. The visual schema or reference system must essentially rely on effective intake of visual feedback information. 2. When the conceptual demands are simple, even DS subjects can use immediate proprioceptive information to guide their movements in the absence of vision (Anwar, 1981a,b,c; Anwar & Hermelin, 1979). However, these subjects show some instability in the use of this source of information, which may affect the building and development of motor programs and/or proprioceptive schema. From these results it seems quite clear that any task which requires attention to visual and proprioceptive reafferent information [in terms of Held’s (1961, 1968) formulation both are important in development] would be difficult for DS subjects. Nevertheless, the finding that DS subjects can effectively use immediate proprioceptive information is promising. This result suggests some relevant practical implications for remediation.

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Practical Considerations From his extensive review of DS,Gibson (1978) concludes that psychological gains are imminent if the early intervention programs are adjusted to those properties of the sensory, motor, and arousal systems which are characteristic of the disorder. In order to implement such a remediation program it is essential to reduce the gap between basic and applied research in mental retardation. Taking into account the present review, one might expect that early training of motor skills may reduce the generally observed motor-expressive handicap in this syndrome. From the experiments which have been reported here, the following suggestions could be made: I.It was found that proprioceptive feedback in the absence of vision could be handled efficiently by DS children. This efficient use of proprioceptive feedback under some conditions suggests that training which emphasizes attention to such proprioceptive reafferent feedback may have merit. Perhaps writing and copying skills could be improved in older DS subjects by incorporating a number of teaching trials where visual feedback from the hand would be prevented. Thus the subject would be forced to attend to only one feedback system, i.e., proprioception . 2. DS subjects were susceptible to interpolated movements which disrupted a previously established pointing response. Such detrimental effects of asymmetrical pointing suggest that when working with DS subjects tasks should be arranged in such a way that the teaching of movements should be restricted to those in the same direction at any one time. Only after the rules are adequately learned, can transfer to wider sets of movements be attempted. 3. In addition, for the very young DS children, some training of the visual scanning system may be beneficial. However, this is not easily done, as scanning via the visual system incorporates a number of different stimulus dimensions simultaneously. For example, in teaching visual recognition of the differences between a square and a circle, the DS child may be unable to attend simultaneously to the relevant features which distinguish the two shapes. The impressive work by Zeaman and House (1963) has already shown such attentional difficulties with SSN subjects. The advantage with proprioceptive reafferent feedback is that it is successive, and relevant features are felt consecutively. Shape recognition and reproduction may thus be aided if the subject is forced to trace the contours of shapes actively. This could be done by using shapes which have deeply imbedded grooves, along which a cursor could be moved by the subject or by the experimenter guiding the subject’s hand. There is some preliminary evidence from a pilot study (in collaboration with Judith Lazlo and P. Bairstow) that such proprioceptive or kinesthetic information can be effectively coded by DS subjects. When the subject, either actively or passively, moves his hand along the contours of the shape, visual attention may not be necessary and may even be superfluous.

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Thus a tentative hypothesis is that a training paradigm which emphasizes only the proprioceptive source of reafferent feedback early in DS development may be effective. Once the redundancies are established, and the contingent probabilities learned, the DS subject may learn the rules and strategies which must form the basis of a motor schema. Strategies once adopted through the kinesthetic/proprioceptive system may then transfer to the congruent and/or subsequent visual oculomotor system, which must continue to be regarded as the feedback system “par excellence.” There is some evidence from normal development (Gregg, Haffner, & Korner, 1977) that vestibular stimulation serves to enhance oculomotor pursuit movements in newborn babies. Thus there may be some substance in the hypothesis that remedial training carried out via the proprioceptive system may have a positive effect on the visual system. ACKNOWLEDGMENTS

Dr.Neil O’Connor and Dr.Beate Hermelin. I am very grateful to these colleagues for clearly identifying the “wood” when I got lost in the “trees.” 1 would also like to thank Dr. Antoinette Krupski for her critical but helpful suggestions. I would like to acknowledge the helpful suggestions and critical appraisal given to me by

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Fitts, P. M., & Petersen, J. R. Information capacity of discrete motor responses. Journal of Experimental Psychology, 1964, 67, 103-1 12. Fraiberg, S. lnsights from the blind. New York: Basic Books, 1977. Frith, U., & Frith, C. D. Specific motor disab es in Down’s Syndrome. Journal of Child Psychology and Psychiatry, 1974, 15, 293-301. Ganz, L. Orientation in visual space by neonates and its modification by visual deprivation. in A. H. Riesen (Ed.), The developmental psychology of sensory deprivation. New York Academic Press, 1975. Gesell, A,, & Thompson, H. Infant behaviour. New York: McGraw-Hill, 1934. Gibson, D. Down’s Syndrome: The psychology of mongolism. London: Cambridge Univ. Press, 1978.

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Gregg, C. L., Haffner, M. E., & Komer, A. F. The relative efficacy of vestibular-proprioceptive stimulation and the upright position in enhancing visual pursuit in neonates. Child Development. 1976, 47 309-314.

Grigg, P. Response of joint afferent neurons in cat medial articular nerve to active and passive movements of the knee. Brain Research. 1976, 118,482-485. Hein, A. Acquiring components of visually guided behavior. In A. Pick (Ed.), Minnesota symposium on child psychology. Minneapolis: Univ. of Minnesota Press, 1972. Held, R. Exposure history as a factor in maintaining stability of perception and co-ordination. Journal of Nervous and Mental Diseases, 1961, 132, 26-32. Held, R. Plasticity in sensorimotor co-ordination. In S. J. Freeman (Ed.), The neuropsychology of spatially oriented behaviour. Homewood, 111.: Dorsey, 1968. Held, R., & Hein, A. Movement-produced stimulation in the development of visually guided behaviour. Journal of Comparative and Physiological Psychology, 1963, 56, 872-876. Henry, F. M., & Rogers, D. E. Increased response latency for complicated movements and “memory drum” theory of neuro-motor reaction. Research Quarterly, 1960, 31, 448-458. Hermelin, B. Effects of variation in the warning signal on reaction time of severe subnormals. Quarterly Journal of Experimenfal Psychology, 1964, 16, 241-249. Hermelin, B., & O’Connor, N. Shape perception and reproduction in normal children and mongo1 and non-mongo1 imbeciles. Journal of Mental Deficiency Research, 1961, 5 , 67-72. Hermelin, B., & Venables, P. Reaction time and alpha blocking in normal and subnormal subjects. Journal of Experimenral Psychology, 1964, 67, 365-372. Howard, 1. P., & Templeton, W. B. Human spatial orienrarion. New York: Wiley, 1966.

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Kerr, B. Task factors that influence selection and preparation for voluntary movements. In G . E. Stelmach (Ed.), Information processing in motor control and learning. New York: Academic Press, 1978. Kirman, B. H. Epilepsy in mongolism. Archives of Diseases in Childhood, 1951, 26, 501. Klapp, S. T. Short-term memory as a response preparation state. Memory and Cognition, 1976, 4, 721-729.

Knights, R. M., Atkinson, B. R., & Hyman, J. A. Tactual discrimination and motor skills in mongoloid and non-mongoloid retardates and normal children. American Journal of Mental Deficiency, 1967, 71, 894-900. Knights, R. M., Hyman, J. A., & Wozny, M. A. Psychomotor ab es of familial brain-injured and mongoloid retarded children. American Journal of Mental Deficiency, 1965, 70, 454-457. Komiya, M. Comparative studies of Down’s Syndrome and physiologically mentally retarded children on figure copying ability. Japanese Journal of Special Education, 1973, 11, 3 1-38. Cited by D. Gibson in Down’s Syndrome: The psychology of mongolism. London: Cambridge Univ. Press, 1978. Kralovich, A. M. A study of performance differences on the Caltell infant intelligence scale between matched groups of organic and mongoloid subjects. Journal of Clinical Psychology. 1959, 15, 198- 199.

McDonald, G.,& MacKay, D. N. The effects of proximal and distal proactive interference on recall by subnormals. Journal of Mental Deficiency Research, 1974, 18, 377-391. Marteniuk, R. G., & Roy, E. A. The codability of kinesthetic location and distance information. Acta Psychologica, 1972, 36, 47 1-479. Marteniuk, R. G., Shields, K . W., & Campbell, S. C. Amplitude, position, timing and velocity as cues in reproduction of movement. Perceptual and Motor Skills. 1972, 35, 51-58. Montessori, M. The Montessori method. New York: Schocken, 1964. Mountcastle, V. B. Some functional properties of the somatic afferent system. In W. A. Rosenblith (Ed.). Sensory communication. Cambridge, Mass.: MIT h e s s , 1961. Mountcastle, V. B., Poggio, G. F., & Werner, G. The relation of thalmic cell response to peripheral stimuli varied over an intensive continuum. Journal of Neurophysiology, 1963, 26, 807-839. Nachmias, J. Figural after-effects in kinesthetic space. American Journal of Psychology, 1953, 66, 609-6 12. O’Connor, N., & Berkson, G. Eye movement in normals and defectives. American Journal of Mental Deficiency. 1963, 68, 85-90. O’Connor N . , & Hermelin, B. Visual and stereognostic shape recognition in normal children and mongo1 and non-mongo1 imbeciles. Journal of Mental Deficiency Research, 1961, 5 , 63-66. O’Connor, N., & Hermelin, B. Speech and thought in severe subnormality. New York: Macmillan, 1963.

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O’Connor N., & Hermelin, B. Seeing and hearing and space and time. New York: Academic Press, 1978. O’Hara, P. T. Electron microscopic study of the brain in Down’s Syndrome. Brain, 1972, 95(4), 681-684. Pascal, G. R. The effect of a disturbing noise on the reaction time of mental defective. American Journal of Mental Deficiency, 1953. 57, 691. Penrose, L. S . , & Smith, G. F. Down’s anomaly. London: Churchill, 1966. Pew, R. W. Human perceptualmotor performance. In B. H. Kantowitz (Ed.), Human information processing: Tutorials in performance and cognition. Hillsdale, N. J.: Erlbaum, 1974. Piaget, J. Origins of intelligence. New York: Basic Books, 1954. Pick, H. L., Pick, A. D., & Klein, R. E. Perceptual integration in children. In L. P. Lipsett & C. C. Spiker (Eds.), Advances in child development and behavior (Vol. 3). New York Academic Press, 1967. Rosen, I . , & Asanuma, H. Peripheral afferent inputs to the forelimb area of the monkey motor cortex: Input-output relations. Experimental Brain Research, 1972, 14, 257-273. Rudel, R. G. The transposition of intermediate size by brain-damaged and mongoloid children. Journal of Comparative and Physiological Psychology 1960, 53, 89-94. Sackett, G. P. Response to differentiated visual complexity in four groups of retarded children. Journal of Comparative and Physiological Psychology, 1967, 64, 200-205. Schmidt, R. A. The index of pre-programming: A statistical method for evaluating the role of feedback in simple movements. Psychonomic Science, 1972, 27, 83-85. Schmidt, R. A . A schema theory of discrete motor skill learning. Psychological Review, 1975, 82, 225-260. Schmidt, R. A . The schema as a solution to some persistent problems in motor learning theory. In G. E. Stelmach (Ed.), Motor control: Issues and trends. New York Academic Press, 1976. Schmidt. R. A. Control processes in motor skills. Exercise and Sporrs Therapy Review, 1977, 4. Scott, W. S. Reaction time of young intellectual deviates. Archives OfPsychology, 1940, No. 256. Sersen, E. A., Astrup, C., Floistad, I., & Woris, J. Motor conditional reflexes and word associations in retarded children. American Journal of Mental Deficiency, 1970, 74, 495-501. Sherrington, G. S. The integrative action of the nervous system. London: Constable, 1906. Skoglund, S. Joint receptors and Kinesthesis. In I. Iggo (Ed.), Handbook of sensory physiology: Somatosensory system (Vol. 2). Berlin: Springer-Verlag. 1973. Solitaire, G. B., & Lamarche, J. B. Alzheimer’s Disease and senile dementia as seen in mongoloids: neuropathological observations. American Journal of Mental Deficiency. 1966, 70, 840-848. Solitaire, G. B., & Lamarche, J. B. Brain weight in adult mongol. Journal ofMental Deficiency Research, 1967, 11, 79-84. Stedman, D. J., & Eichorn, D. H. A comparison of the growth and development of institutionalized and home reared mongoloids during infancy and early childhood. American Journal of Mental Deficiency, 1964, 69, 391-401. Stelmach, G. E. Information processing in motor control and learning. New York: Academic Press, 1978. Tizard, J., & Venables, P. H. Reaction time responses by schizophrenics, mental defectives and normal adults. American Journal of Psychiatry, 1956, 112,803. Wallace, R. M., & Fehr, F. S. Heart rate, skin resistance and reaction time of mongoloid and normal children under baseline and distraction conditions. Psychophysiology, 1970, 6, 722-73 1. Warner, E. N. A survey of mongolism with a review of 100 cases. Canadian Medical Association Journal. 1935, 33, 495-500. White, B. L., Castle, P., & Held, R. Observations on the development of visually directed reaching. Child Development, 1964, 35, 349-364.

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Rumination NIRBHAY N. SINGH DEPARTMENT OF PSYCHOLOGY MANGERE HOSPITAL AND TRAINING SCHOOL MANGERE, AUCKLAND, NEW ZEALAND

I. Introduction . . . . . . . . . . ..................... A . Prevalence of Rumin in the Mentally Retarded B. Differential Diagnosis of Rumination ........................... C. Vomiting and Ruminative Vomiting. ....................... 11. Theories of Etiology . . . . . . . . . . . . . . . . ........................... 111. Intervention Studies . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . A. Psychopharmacological . . . . . ........................... B. Surgical . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . C. Psychodynamic and Psychotherapeutic ................................. D. Behavioral . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1V. Summary and Conclusions . . . ........ ...... References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

139 140 141 144

144 148 148 149 149 155 174 171

I. INTRODUCTION Although rumination is a relatively rare psychosomatic disorder both in child and adult populations, it commands increasing attention from clinicians because of its life-threatening nature and resistance to psychopharmacological interventions. The disorder or syndrome was first noted in adults by Fabricio di Acquapendente in 1618, but it was not until 1907 that its occurrence was first reported in children (Brockbank, 1907; Hollowell & Gardner, 1965; Maas, 1907). Rumination can be defined as deliberate regurgitation or the bringing up of previously ingested food into the mouth, much in the manner of ruminant animals. This differs from ordinary regurgitation which is involuntary and requires no effort on the part of the patient. Deliberate regurgitation can be achieved 139 INTERNATIONAL REVIEW OF RESEARCH IN MENTAL RETARDATION, Vol. 10

Copyright @ 1981 by Academic Ress. Inc. All righta of rcpmduction in any form msmcd. ISBN 0-12-366210-9

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either by thrusting the fingers in the mouth or by a series of vigorous thrusting movements of the tongue backward and forward. Usually, the patient catches a part of the regurgitated gastric contents in the mouth and attempts to rechew and reswallow it. Often some of this food drools or oozes from the corners of the mouth. The rumination syndrome usually appears between the ages of 3 weeks (Hollowell & Gardner, 1965) and about 12 months (Kanner, 1957; Williams, 1955) and may persist for many months or even years, especially in the mentally retarded. When this disorder reaches pathological proportions, it may lead to severe weight loss, growth failure, dehydration, severe malnutrition, and electrolyte imbalance. Although scant observational data are available, the clinical literature suggests that the severity of rumination varies considerably. Various morality rates have been reported, ranging from 12 to 50% (Clark, 1956; Gaddini & Gaddini, 1959; Kanner, 1957; Lourie, 1955; Sajwaj, Libet, & Agras, 1974). Although the declining number of publications on rumination in the current literature would suggest a major decline in these figures, this may be due only to the overall improvement in the pediatric care of infants and the mentally retarded. Further information of a historical nature is reported in an early review by Kanner (1936).

A.

Prevalence of Rumination in the Mentally Retarded

There are no systematic studies reporting prevalence of rumination either in ‘‘normal” or in mentally retarded populations. However, some unpublished data are available from one state facility for the mentally retarded showing a prevalence of about 6.02%(Singh & Dawson, 1980). Singh and Dawson surveyed the entire inpatient population in an institution for the mentally retarded. The initial screening, which was carried out in collaboration with the ward changes, recorded the names of children from each ward who were known ruminators. The ward personnel were then interviewed to determine the frequency and duration of rumination for each patient. Finally, random observations of the children who engaged in rumination were carried out for 4 weeks. Case data and the history of rumination for each patient were obtained from their medical and nursing files. Of a total population of 349, 21 (6.02%) were found to be ruminators at the time of the survey. The subject characteristics of these patients are presented in Table I. Of the 21 ruminators, 8 were profoundly retarded and 13 were severely retarded. That is, 22.2%of the profoundly retarded ( N = 36) and 8.5% of the severely retarded ( N = 153) patients at the institution were ruminators. No mildly retarded (N = 27) or moderately retarded (N = 133) patients engaged in rumination. Only 4 of the 21 ruminators were female. This finding is in accord

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with informal observations made by previous investigators of rumination in “normal” infants (e.g., Einhorn, 1977; Gaddini & Gaddini, 1959). The age of onset of rumination could not be determined for 12 patients since they were known ruminators at the time of their institutionalization. However, of the other 9, none had engaged in rumination in early infancy or even before the age of 6.5 years. All 9 children developed rumination some years after they were institutionalized. The duration of rumination varied from a few minutes to about 2 hours, with most of the patients engaging in rumination immediately after each meal. The frequency of rumination varied considerably, but 7 patients ruminated after most meals.

B. Differential Diagnosis of Rumination Although rumination does not appear to be the result of any organic abnormality, anatomic or physiologic, this syndrome is often confused with a variety of other disorders. In the absence of a differential diagnosis, many erroneous diagnoses may be made before the physician, who may be unfamiliar with this relatively rare syndrome, labels it rumination by a process of elimination. For example, Richmond, Eddy, and Green (1958) k t the following diagnoses which had been considered for their patients before the symptom complex was recognized as that of rumination: adrenal insufficiency, pyloric stenosis, food allergies, duodenal ulcer, esophageal chalasia, and severe feeding problems of unspecified origin. As a result of their own extensive experience with this syndrome, Richmond et al. caution against a mistaken diagnosis since it might result in the physical deterioration of the patient and may even prove to be fatal if appropriate treatment is not provided. Einhorn (1977) suggested that the following points be kept in mind when making a differential diagnosis of gastrointestinal disorders. Rumination should be strongly suspected if the patient is emaciated and from an economically disadvantaged home and has vomitus constantly plastered over his chin, neck, and upper shirt but is never actually seen vomiting. This suspicion can then be confirmed by observational techniques. Also, rumination should be strongly suspected if the patient appears to derive sensory pleasure from mouthing the regurgitated gastric contents instead of suffering the discomforts related to the act of vomiting. A close scrutiny of the outward appearance of the patient is also helpful in the diagnosis. Ruminators, particularly infants, are thought to be quiet, sad, and singularly wide-eyed. They are often seen to be lost in inner contemplation, seemingly quite detached from their immediate environment but are quick to respond to external stimulation. Richmond ef al. (1958) have noted that ruminators have associated neurotic traits such as autistic self-stimulatory and

TABLE I CHARACTERISTICS OF INSTITUTIONALIZED RUMINATORS

Subject 1

3

4 5

6 7 8

9

Level of retardation and diagnosis

Sex

Present age (years, months)

Profoundly retarded of unknown etiology Severely retarded due to microcephaly Profoundly retarded with epilepsy of unknown etiology Severely retarded of unknown etiology

F

19, 4

Severely retarded with spastic quadriplegia and microcephaly probably due to cerebral injury Profoundly retarded of unknown etiology Severe brain damage with severe mental retardation and epilepsy Profoundly retarded with epilepsy due to birth injuries Profoundly retarded with spastic quadriplegia of unknown etiology

Age at institutionalization (years, months) 9, 10

Age at onset of ruminative vomiting (years, months) 15, 3

After each meal, for 1-2 hours

Present at admission 24, 5

After each meal, for 10-30 minutes After each meal, for 15-25 minutes

0-3 times a week, attention seeking, for 0-10 minutes 0-3 times a week, only when upset, for 0-10 minutes

F

18

F

30, 6

16, 4 17, 8

M

16, 6

4, 10

12, 3

F

18, 4

17, 4

17, 6

M

24, 2

12, 11

18, 1

F

18, 4

7, 8

M

25, 6

M

24, 9

10

9, 1

Current frequency and duration

Present at admission

20, 4 Present at admission

0-3 times, a week, after meals, for 5-15 minutes 3-5 times a week, after meals, for 10-30 minutes 0-3 times a week, after meals, for 10-30 minutes 0-3 times a week, after meals, for 10-30 minutes

10 11

12 13 14

15 16 17 e

ti

18

19 20 21

Profoundly retarded with spastic quadriplegia of unknown etiology Severely retarded of unknown etiology probably due to microcephaly and prematurity Severely retarded of unknown etiology

M

30, 3

M

8. 5

M

Severely retarded due to Down’s syndrome Severely retarded with spastic quadriplegia of unknown etiology Severely retarded with epilepsy Severely retarded due to congenital rubella Severely retarded associated with multiple congenital abnormalities Severely retarded of unknown etiology Severely retarded probably due to cerebral birth damage Profoundly retarded of unknown etiology in monozygous twins Profoundly retarded of unknown etiology in monozvgous twins

17, 8

Present at admission

4

Present at admission

25, 1

13, 5

Present at admission

M

21, 2

9, 7

Present at admission

M

10, 1

4, 2

Present at admission

M

M

11, 1 14, 4

3, 11 10, 7

Present at admission 12. 3

M

8, 1

3, 2

Present at admission

M

16, 10

13, 9

Present at admission

M

10, 3

8, 9

Present at admission

M

16, 5

3, 11

6, 6

M

16, 5

3, 11

6, 6

0-3 times a week, after meals, for 0-10 minutes After most meals for 30-60 minutes

0-3 times a week, after meals for 30 minutes 0-3 times a week, when upset, for 0-10 minutes 0-3 times a week, when not satisfied with quality of food After each meal for 1-2 hours 4-5 times a week, after meals, for 10-30 minutes 3 4 times a week, only at breakfast, for 10-30 minutes 0-3 times a week, after meals, for 10-20 minutes 0-3 times a week, when upset, for 0-10 minutes During and after each meal, for 1-2 hours During and after each meal, for 1-2 hours

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stereotyped behaviors. It is suggested that these external cues be systematically considered when making a diagnosis of rumination.

C. Vomiting and Ruminative Vomiting Several investigators have made the observation that rumination is usually preceded by a prolonged period of vomiting (e.g., Gaddini & Gaddini, 1959; Richmond et al., 1958). This vomiting, which is without an organic cause, does not appear to be functionally different from ruminative vomiting or deliberate regurgitation. While most pediatric textbooks refer to these disorders separately (e.g., Forfar & Ameil, 1973; Rudolph, 1977) vomiting is usually associated with rumination and has often been referred to as ruminative vomiting (e.g., Lang & Melamed, 1969; Mulick, Schroeder, & Rojahn, 1980). In this article, rumination and ruminative vomiting will be considered as being functionally equivalent. The vomiting which precedes rumination tends to be mistaken for habitual vomiting or vomiting due to certain organic dysfunctions. It is necessary to make a differential diagnosis between the two types of vomiting for the purposes of treatment since involuntary vomiting is one of the commonest symptoms in young children. In young children involuntary vomiting is usually seen in association with infections, both enteral (e.g., shigella, salmonella) and parenteral (e.g., tonsillopharyngitis, otitis media, pertussis, septicemia). It is also associated with nonobstructive organic disorders of the alimentary tract, e.g., hiatus hernia (partial thoracic stomach) and chalasia (gastroesophageal incompetence), and is usually a feature of the central nervous system diseases, e.g., meningitis and encephalitis. Vomiting due to such organic dysfunctions invariably disappears when the primary presenting problem is given appropriate medical treatment. The primary purpose of this article is to summarize and critically review the relatively small number of studies dealing with the treatment of rumination. A brief overview of etiological theories is provided for the reader who is not already familiar with this general area. Although the coverage is not to be taken as exhaustive, an effort has been made to include all the published clinical and treatment literature from the last 30 years on rumination in the mentally retarded.

II. THEORIES OF ETIOLOGY There has been no lack of theoretical speculation about the nature and etiology of rumination. Kanner (1957) lists the following theories which had some currency at various times: heredity, dilatation of the lower end of the esophagus or of the stomach, overaction of the sphincter muscles in the upper portions of the alimentary canal, cardiospasm, pylorospasm, gastric hyperacidity, achlorhydria,

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movements of the tongue, insufficient mastication, pathologic conditioned reflex, aerophagy ,finger sucking, neuropathic constitution, motility neurosis, gastric neurosis, and lack of occupation, boredom analogous to “cage sickness” of animals. All of these theories received only limited acceptance mainly because they did not generate effective treatment strategies for the disorder. Furthermore, the early theorists did not have access to adequate experimental methods to investigate and substantiate their theoretical speculations. More recent speculation has emphasized the psychosomatic nature of the disarder, with particular emphasis being placed on tHe disordered mother-infant relationship, chronic familial disharmony, and maternal psychopathology. Although these notions share a theoretical communality, most formulations have different emphases within this theoretical umbrella. The earliest speculation stressed inadequate mothering, emotional disturbances in the mother, and a disturbance of “mothering activities” as the variables of importance in the occurrence of ruminative vomiting and other gastrointestinal disorders. Ribble (1944), for example, maintained that an increase in mothering activities (i.e., handling, fondling, and rocking) should result in the amelioration of the disorder. In general, she suggested that there must be a prolonged period of such mothering for normal physiological and psychological development of children since they respond directly and immediately to the emotional tone of their environment. Ribble’s views, however, have been criticized on theoretical grounds (e.g., Pinneau, 1950). Furthermore, Hopper and Pinneau (1957) present experimental evidence contrary to Ribble’s (1944) postulates which show no causal relation between increased stimulation and decreased regurgitation and ruminative vomiting. Theorists with a psychoanalytic orientation have implicated feeding disturbances, especially during the oral phase of psychosexual development, as a major causal factor in ruminative vomiting (e.g., Sylvester, 1945). Furthermore, rumination is thought to be related to early oral-anal fixations precipitated by a severe disturbance in the mother-child relationship dating from the pregenital period. Others (e.g., Sperling, 1949) have speculated on the importance of the mother’s unresolved conflicts in the genesis of this disorder. In this regard, Berlin, McCullough, Liska, and Szurek (1957) have stated that the mother’s character and her emotional state is one of the major determinants of ruminative vomiting. In a similar vein, Stein, Rausen, and Blau (1959) have suggested that rumination is a “physiological concomitant of anxiety and depression, coincident with a similar emotional disturbance in the mother. Gaddini and Gaddini (1959) found that mothers of ruminant children were immature, with disturbed object relationships, profound anxiety, death fears, ambivalence toward their babies, and, in general, a marked inadequacy when faced with the demands of feminine roles. Reinhart, Evans, and McFadden (1977) have suggested that the disorder is “one of prolonged symbiotic relationship and the failure of the child ”

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to separate and individuate. That is, the parent is too involved in controlling the child’s behavior beyond the time that the child should have control himself.” In general, these theorists view ruminative vomiting as a nonspecific response to the chronic tensions inherent in unsatisfactory mother-child relationships. The best theoretical formulation of a psychoanalytic persuasion has been provided by Richmond et al. (1958) who suggested that rumination results from a disturbed or unsatisfactory mother-infant relationship. They suggested that the mothers of ruminant infants were not able to fulfill an adult psychosexual role and their urge to satisfy their own dependent needs undoubtedly contributed to their marital disharmony. Such mothers are regarded as incapable of providing warm, comfortable, and intimate physical care for the infants because of their inability to give up their own dependent needs. As a result of this inadequate mothering, the infant seeks and recreates such gratification from within. Richmond et al. suggested that in the absence of external stimulation and gratification from the environment, the infant tends to substitute other experiences in its stead. Regurgitation and rumination belong to this category of experiences. This theoretical formulation was particularly popular in the 1950s and 1960s and it generated a plethora of clinical case studies which attempted to treat rumination by the interruption of the mother-child relationship and the provision of a warm and loving mother substitute. It should be noted that Richmond et al. did not postulate that specific maternal psychopathology invariably results in rumination in the infant. They hypothesized that any factors which deprived the infant of intimate, stimulating relationships may predispose him to the disorder. It has been suggested that certain children may have a biologic predisposition physiologically to gastrointestinal disorders (e.g., Apley, 1975; Weiner, Thaler, Reiser, & Mirsky, 1957) since only some individuals exposed to such early childhood conditions develop this disorder. Although the psychoanalytic and psychotherapeutic case reports provide some support for the Richmond et al. (1958) theory, there is no experimental evidence to show whether the unsatisfactory family dynamics are the causal variables or the maintaining variables of this disorder. It is highly likely that certain emotional factors may be important early elicitors of ruminative vomiting in some children but in others, rumination may originally develop for nonfamilial reasons. Once the behavior or disorder is in the child’s repertoire, his parents or caretakers may unwittingly reward some of the symptoms of the disorder. There is no compelling evidence to show that ruminative vomiting occurs only in children who were exposed to unsatisfactory family dynamics during their early years. Kanner ( 1957, p. 484) maintained that ‘‘rumination is acquired incidentally and then taken up as a pleasurable habit practised voluntarily, suggesting that the etiology of this disorder can be explained in terms of learning principles. ”

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Learning theorists have classified rumination as a self-injurious behavior (see, e.g., Frankel & Simmons, 1976) and consonant with this view, the etiology of this disorder can be explained in terms of instrumental conditioning. Skinner (1953) advanced two hypotheses which account for this class of disorders: the discriminative stimulus hypothesis and the avoidance hypothesis. Since both of these hypotheses have been considered at length in terms of self-injurious behavior in several reviews (Bachman, 1972; Baumeister & Rollings, 1976; Carr, 1977; Frankel & Simmons, 1976), only a brief overview of the hypotheses specific to rumination is warranted here. According to the discriminative-stimulus hypothesis ruminative vomiting can function as a conditioned positive reinforcer if it has been selectively associated with or predicts positive reinforcement. Given a history of conditioning, ruminative vomiting can function as a discriminative stimulus for positive reinforcement. Several studies in the behavioral literature on rumination are pertinent here. Wolf, Birnbrauer, Williams, and Lawler (1965) and Wolf, Birnbrauer, Lawler, and Williams (1970) found that attention maintained a vomiting response in a mentally retarded child and that the withdrawal of attention resulted in a temporary increase in the response. Singh and Dawson (1980) found that some of their patients engaged in ruminative vomiting only under certain conditions. For example, some instances in some patients were under discriminative control of certain attendants who were a source of social attention for their ruminative vomiting. Others were observed to engage in this behavior only when attention was withdrawn. Smeets (1970) reported that his patient vomited in the presence of a nurse but stopped when she left the room. Thus, either the absence or presence of the ward attendants might function as a discriminative cue for vomiting. White and Taylor (1967) found that the suppression of ruminative vomiting through response-contingent electric shock resulted in an increase in arm-biting. Similarly, Galbraith, Byrick, and Rutledge (1970) found that the use of aversive control procedures in the suppression of ruminative vomiting in a young boy resulted not only in response suppression but also in an increase in the boy’s self-stimulatory and self-injurious behaviors. These studies suggest that the suppression of ruminative vomiting may become discriminative for other forms of maladaptive behavior. Other than for anecdotal reports, there is no experimental evidence in the literature to support the avoidance hypothesis interpretation of ruminative vomiting. According to this hypothesis, children may engage in ruminative vomiting if by so doing they can avoid other, more aversive, consequences. Singh and Dawson (1980) found that some children engaged in ruminative vomiting if they did not like the food they were offered. Possibly, they found retention of the food more aversive than rumination. Although it is also possible that the vomiting was controlled by its effect on the behavior of the nursing staff.

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In summary, it can be argued that most theoretical accounts of rumination have been little more than unsubstantiated speculations about its nature and etiology. By and large, the earlier the proposed hypothesis, the more speculative it has been. The psychodynamic and psychotherapeutic hypotheses have been mainly clinical in nature, often impressionistic and invariably untestable. However, these hypotheses did generate a plethora of treatment-based studies, which will be reviewed in Section II1,C. The instrumental-learning model is not only the most parsimonious formulation advanced to date, but has also offered most in terms of treatment possibilities with the mentally retarded.

111.

INTERVENTION STUDIES

A wide variety of therapeutic regimens have been advocated for the treatment of rumination. With the exception of behavioral techniques, however, it would be difficult to evaluate the effectiveness of any one particular approach. For example, some parents have reported success with osteopathic treatments and others have reported a marked improvement as a result of their visit to a clinic in spite of no specific treatment being given (Hoyt & Stickler, 1960). Various other symptomatic treatments have also been favored at times, including change of climate, thickened feeds, limited fluids and/or feedings, and the administration of a number of syrups. Various mechanical devices have also been used to control rumination, including ruminating caps, inflatable balloons (which are inserted in the esophagus), arm restraints and splints (Menking, Wagnitz, Burton, Coddington, & Sotos, 1969; Sheinbein, 1975), and even nose packing (Clark, 1956). Other treatment approaches which have had some popularity at various times are detailed below.

A. Psychopharmacological There is only a limited experimental literature on psychopharmacological treatments of classical psychosomatic disorders, and fewer still on its use in the treatment of rumination. Drugs are usually used to treat the physiological rather than the psychological component of these disorders. Some data on the effects of various drugs on psychosomatic disorders are available in the animal literature. For example, Bonfils and Dubrasquet (1969) found imipramine to be effective against the development of restraint-produced stomach ulceration in rats. Furthermore, chlorpromazine, thioridazine, and thioproperazine were found to be not as effective as imipramine, whereas reserpine actually increased the frequency of ulcers. The clinical literature is replete with anecdotal reports on the use of psychopharmacological agents in the treatment of rumination. Kanner (1957) has

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noted that hydrochloric acid, atropine, luminal, and the gastric juice of pigs have been tried and found ineffective. However, virtually all other drugs have been tried since Kanner made his observations. Antiemetics, antinauseants, antihistamines, anticonvulsants, and antispasmodics have all proved of little value (Clark, 1956; Hoyt & Stickler, 1960; Lang & Melamed, 1969; Stein er al., 1959). Although it appears that drugs are not indicated in the treatment of rumination, at this point it is difficult to draw definitive conclusions from the current literature. The anecdotal reports suffer from various problems which make it hazardous to infer a causal relation between a given drug and the consequent behavior change. For example, none of the reports used experimental controls adequate to yield unambiguous results (see Aman & Singh, 1980; Sprague 8c Werry, 1971). Certainly, well-designed and controlled drug investigations are needed to confirm the findings of the anecdotal reports before psychopharmacological interventions are dismissed as useless.

B. Surgical Surgical treatments of rumination have never had as widespread a popularity as psychopharmacological regimens. Although there is some experimental evidence from animal studies that surgical manipulation of the central nervous system may be an effective treatment (e.g., Borison, 1959), there is scant support for this type of therapy with humans. Kanner (1957) has noted that in the last century, trephining of the skull was usually advised as a treatment for rumination and cites the case report by Hammond (1 894) which shows that such operations were actually carried out. Since then, there have been cases in the literature which have reported "cures" due to the removal of a normal appendix and after an exploratory laparotomy (see Hoyt & Stickler, 1960). Surgical interventions have also been used when the clinician has been unable to make a differential diagnosis of gastrointestinal disorders. In general, however, surgery does not appear to have much to offer diagnostically or therapeutically in this syndrome.

C. Psychodynamic and Psychotherapeutic Until the late 1960s, the most acceptable form of therapy for psychological problems in the mentally retarded was psychotherapy, especially of the psychodynamic variety. The literature to be reviewed in this section certainly attests to this fact. While several studies appeared in the literature from the mid-1950s to the late 1960s on the psychotherapeutic treatment of rumination of both normals and the mentally retarded, the 1970s literature is noteworthy because of its singular lack of such studies. The majority of the psychotherapeutic studies reviewed in this section used

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mentally normal infants and children as subjects. These studies have been included not only because of their apparent success in the suppresion of rumination but also because of the applicability of some of these procedures to the mentally retarded. This is especially true of the studies which have used “substitute” mothers as a crucial component of the overall treatment. 1. TREATMENT OUTCOME

One of the best documented studies on psychogenic vomiting from a psychoanalytic orientation is a case report by Berlin et al. (1957). Eight months of therapy was provided to a hospitalized 3 year 10-month-old boy and his parents at the Langly Porter Clinic. The boy vomited when his mother was anxious and tense or when his wishes and demands were not met. On admission, the most notable clinical features were his emaciation, dehydration, cyanosis, and lack of tissue turgor. He presented as a sullen, depressed, and withdrawn child. Within an hour of admission he changed from a sad, sick, cyanotic, vomiting child to a vivacious, vigorous, hungry youngster, with vomiting occurring only when his demands were thwarted. Therapy was scheduled for an hour each day in the playroom where the nurse assigned to the case gave him continuous attention. Although the general therapeutic framework was psychoanalytic, several components can be clearly identified as behavioral procedures. For example, noncontingent attention procedures were used throughout the treatment, often leading to an increase in the frequency of vomiting. At other times, punishment via withdrawal of positive reinforcement was used, although the authors labeled this technique as untherapeutic from a psychoanalytic orientation. Also, it was reported that vomiting ceased for short periods when the patient’s mother got very angry with the child contingent on his vomiting. This suggests that verbal reprimand was punishing to the child. Concomitant with the therapy being given to the child, the parents were given counseling in marital adjustment. Apparently, this resulted in a reduction of tension in both parents and the consequent easier relationship between them coincided with their ability to better handle the child at home. As for the child, his frequency of vomiting was greatly reduced over the 8 months he received therapy. Berlin et al. (1957) noted that there were no durable character changes during treatment in either the child or his parents. The results were discussed in terms of “the reciprocal relation between the intra-psychic dynamics of each family member and the infrafamilial events important in the child’s vomiting” (Berlin et a l . , 1957, p. 229). The mother’s character and her unbalanced emotional state was considered one of the determinants of the child’s vomiting. In this regard, these authors agree with Sperling’s (1949) hypothesis that the mother’s unresolved childhood conflicts are important in the genesis of psychosomatic disorders in children. Other more recent papers (e.g., Davenport,

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1972; Sperling, 1968) have also looked at psychogenic vomiting in terms of family interaction and emotional dynamics within the psychoanalytic framework. The outcome of psychodynamic therapy as exemplified by this study depends on various factors including a proper diagnosis of the problem, stage of “illness,” ego capacity, and ability of the patient to establish rapport with his therapist. Psychoanalysts have found that only a minority of psychosomatic patients are suitable candidates for classical psychoanalytic treatment (Sifneos, 1972; Stokvis, 1960). At best, psychoanalysis would be ineffective with the severely and profoundly retarded since they do not fulfill the criteria for psychodynamic therapy. However, a dynamic approach may be possible with the mildly and moderately retarded if appropriate modifications in the procedure are made and the treatment is judiciously prescribed. Using an approach suggested by Spitz (1946, 1950), Lourie (1955) used a three-stage treatment technique to control rumination in four infants. In the first stage, Lourie (1955) provided a substitute mother to these infants. It was thought that “since these infants had obviously turned away from the world, having withdrawn their object cathexis and reinvested it in the self, any attempt at emotional replacement therapy to accompany the dietary, blood and biochemical replacements were blocked. It quickly became apparent that the important primary goal was to help these children to trust those around them, and reinvest their libido in the substitute mothers available” (Lourie, 1955, p. 255). The second stage of therapy was introduced once the infants learned to accept their substitute mothers. This required the substitute mother to be actively involved with the infant during their rumination periods. During these periods, the substitute mothers would hold, carry, or be in general physical contact with the infants. It was hoped that an infant’s need for gratification by rumination would be substituted by other more adaptive social behaviors. Once this was achieved, the final stage of therapy involved the provision of other forms of stimulation to the infants. In addition to toys, the infant’s own motility patterns were used and encouraged. Of the four infants reported by Lourie (1955), three were successfully treated for rumination with the program outlined above. Rumination was eliminated within a week to 3 weeks and long-term follow-up showed that it had not recurred at 6 and 12 months following termination of treatment. The fourth case was less successful but it was later found that the infant’s rumination could have been attempts to relieve anxiety due to organic disturbances, chiefly pain. A physical examination showed an upper abdominal distension and a peculiar tympany in his chest indicating a diaphragmatic hernia. This diagnosis was confirmed by barium studies and a surgical correction of the diaphragmatic defect quickly eliminated his rumination. In a much quoted study, Richmond et al. (1958) presented their observations on four infants and their mothers, and the subsequent treatment of rumination in

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these infants. The infants, all males, varied in age at the time of referral (6 to 20 months) and all appeared to have associated neurotic traits. Autistic posturing, excessive genital and fecal play, body rocking, head rolling and banging, and excessive finger and thumb sucking were observed in these infants. Richmond et af. described their infants as having “somewhat flattened affect” and widely opened and searching (“radar-like”) eyes. Apparently, these infants were also depressed and preoccupied with themselves. None were breast-fed. Only one case is presented in detail as an illustration of the case material and treatment. Unfortunately, the actual details of the therapy are well concealed in this report. The infant ceased ruminating apparently as a result of the nursing staff providing “stimulating tender and intimate care. The interruption of the insecure mother-infant relationship by hospitalization of the baby and the provision of a warm and stimulating environment with a substitute mother-figure was thought to be responsible for the dramatic results. Gaddini and Gaddini (1959) presented six cases of infant rumination collected over a period of 10 years. Of the six infants, one died as a direct result of his rumination. In all but one case, rumination was preceded by prolonged vomiting. In one case this was precipitated by gastroenteritis but in the other four, it was apparently a nonspecific physiological response to the strained mother-infant relationship. In most cases, the specifics of therapy of a psychological nature are sketchy at best. One could say that in addition to medical treatment for severe dehydration and loss of body weight, the hospital staff offered a mother substitute who was required to establish a warm and positive relationship with the infants. The importance of having a stable mother-child relationship has also been stressed by Stein et al. (1959) in their treatment of infant rumination. They suggested that when the infant’s mother cannot be directly involved, it is essential to provide a mother surrogate since the infant will make only limited progress in treatment without a satisfactory mother-child interrelationship. Stein et a f . presented a detailed case report on an 8-month-old boy who was hospitalized because of malnutrition, an inability to retain food, and a severe weight loss (1000 gm) within the 2 months prior to admission. After several false starts at tender-loving-care therapy on an intermittent basis, a full-time special nurse was engaged as the infant’s therapist for 8 hours daily. The baby responded to her holding, warmth, and attention and ceased to ruminate within 1 month, increasing his weight by 1600 gm in this period. Furthermore, as a consequence of this treatment the baby became more responsive and happy. He began vocalizing and laughing and paid more attention to his social environment. A similar treatment technique was employed by Fullerton (1963) with a 7-month-old infant. Earlier treatment regimens had included thickened feedings and a change in the infant’s posture during feeding, with no appreciable change in the infant’s ruminative vomiting. Treatment with a mother substitute, how”

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ever, saw the cessation of rumination in 4 days and an increase in the patient’s general awareness and social behavior. Hollowell and Gardner (1965) and Menking et al. (1969) have also found substitute mothering by the hospital staff to be effective in the treatment of infant ruminators. As mentioned above, most of the cases reviewed so far concerned normal infants and children who had suffered emotional deprivation in the first few months of life. The next study (Wright & Menolascino, 1966, 1970) deals with four mentally retarded children who indulged in rumination and were treated within the same general psychotherapeutic framework as used with otherwise normal infants and children. This was probably the first study to deal with rumination in the mentally retarded, a disorder once thought to be a rare phenomenon in mentally retarded children (e.g., Gaddini & Gaddini, 1959; Richmond & Eddy, 1957). Wright and Menolascino (1966, 1970) reported a multicomponent treatment technique called “nurturant nursing” which incorporated psychotherapeutic and learning theory techniques. Treatment was carried out in three phases. The initial phase focused on the establishment of a relationship with the child. Tactile stimulation and verbalizations were increased and rhythmic music was played, especially at feeding times. The continuity of nursing personnel was emphasized so that the children could develop close relationships with them. In the middle phase, the children were introduced to new social activities which could compete with their self-stimulatory behaviors. This led to a further development of a warm and dependent relationship with the nursing staff. In the final phase, the nurses concentrated on consolidating the children’s therapeutic gains and extending their developmental potential. According to Wright and Menolascino, this comprehensive therapeutic program was effective in controlling rumination in four mentally retarded children. Despite obvious methodological problems (discussed below), this study was important in that it attempted to treat rumination in the mentally retarded. Furthermore, it provided an impetus for a long list of behavioral studies which have followed. Herbst, Friedland, and Zboralske (1971) have observed that several of the studies describing the treatment of rumination in infants 6 to 16 months of age used positional therapy as a major component of their technique. In these studies (e.g.. Gaddini & Gaddini, 1959; Hollowell & Gardner, 1965; Lourie, 1955; Menking eta!., 1969) the patients were held in an upright position for prolonged periods of time, during and after each meal. Herbst et al. (1971) hypothesized that rumination was a manifestation of a broad spectrum of abnormal movements occurring in association with hiatal hernia and that appropriate positional therapy or surgical repair of the hernia would reverse the rumination symptoms. Their data from three children indeed showed this to be true. However, there is ample evidence (e.g., Fullerton, 1963; Menking et al., 1969) to show that positional therapy by itself or in combination with other procedures is not effective in

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ameliorating rumination in 6- to 16-month-old infants. Furthermore, there is evidence to show that infants without demonstrable hiatal hernia exhibit rumination (e.g., Stein er a l . , 1959). Current evidence does not support the hypothesis of Herbst et a l . (1971) about the origins of rumination and its treatment. 2. METHODOLOGICAL CONSIDERATIONS

The studies reviewed in this section have all been totally within the area of patient care and essentially represent clinical case presentations. As such they suffer from methodological problems which by their very nature are difficult to avoid. However, methodological rigor would require that such treatment be subjected to, at least, quantitative documentary research, and, where possible, to systematic experimental testing. In psychodynamic and psychotherapeutic endeavors, it is not clear exactly why patients improve during treatment. Little useful information vis-a-vis treatment variables is obtained by using pre- and posttreatment measures of behavior change in such situations. Since a complex set of therapist-patient interactions takes place during therapy, such an approach would be inadequate in unscrambling the causal influence of what actually occurs during therapy and the outcome. Furthermore, such an approach does not provide adequate data throughout successive treatment sessions on the effectiveness of individual components of the procedure which can be used to modify or eliminate the nontherapeutic components. Unfortunately research therapists have not developed an adequate causal inference methodology in this area which could be used to verify these techniques experimentally. However, there are several redeeming features of the studies reviewed above. For example, Gaddini and Gaddini (1959) used two observers to record the behavior of their patients. In addition to this, they used cine film to record the same events. This careful and reliable technique for making behavioral observations is now an accepted tool in the armamentarium of behavioral psychologists. These studies are noteworthy in another respect. They provide a wealth of information on the patient in terms of case material, family dynamics, and the conjectured causes of the problem. This enables other researchers to interpret the course of events in terms of other treatment paradigms. The fact that a treatment has been termed psychotherapeutic does not preclude it from being analyzed in terms of other treatment paradigms. The treatment label is not important, it is the process which is of significance in terms of treatment effects. It has already been stated that several behavioral techniques could be identified as components of the treatment package used by psychotherapists. Thus, there could be alternative reasons why such therapy should have been effective in the studies discussed above. It is not unusual for psychotherapeutic studies to have a welter of procedures within single-case presentations. A good example of this sort of study is a

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quasi-experimental report by Wright and Menolascino (1966, 1970). Wright and Menolascino used a variety of techniques including increased social and physical attention, individualized feeding, rhythmic music, tactile stimulation, verbalizations, and environmental stimulus change. This sort of therapy, now commonly known as a “treatment-package strategy” in the behavioral literature (see Kazdin, 1979), is used only when the investigators are interested in the therapeutic outcome of the package without regard to the efficacy or contribution of the individual components within the package. While this is a valid therapeutic technique, only a dismantling or component analysis of the treatment package will lead to an understanding of why the treatment works and which components account for most of the change. Unfortunately, such analyses have not been performed in psychotherapeutic studies of rumination. In summary, it is evident that while the psychotherapeutic studies did not have the methodological niceties required of studies executed today, they appear to have been effective in the treatment of rumination. The general impression one gains from this literature is that “something worked” in these cases, although one is not able to isolate the crucial variable or variables responsible for this effect. However, these studies cannot be dismissed simply on the grounds of methodological shortcomings. Instead, these studies should provide researchers with the impetus for further investigations delineating the conditions under which such interventions are generally effective and why. ,

D. Behavioral A wide variety of behavioral procedures have been used in the treatment of chronic regurgitation and rumination in the mentally retarded. Several problems emerge when one attempts to evaluate the effectiveness of the different treatment techniques used. When the patient is in a potentially life-threatening condition due to severe weight loss, one is ethically bound to provide immediate intervention rather than adhere to the methodological rigor necessary for evaluation research. Thus early reports in this area are almost anecdotal in nature, often without quantitative data. Clinicians have also tended to combine treatment modalities without a conceptual focus, since they have been primarily interested in the question: “Does this treatment procedure work?” rather than the effects of its individual components. Attempts to compare different treatments are thus rendered impossible by the singular lack of studies which isolate a treatment approach, measure the effects, and then replicate it using the same treatment. It is not surprising, therefore, to discover that empirical evaluation of the different treatment techniques has lagged behind their clinical implementation. Even within the last decade, well after the publication of Baer, Wolf, and Risley ’s ( 1968) classic paper on applied behavior analysis, the literature concerning outcome evaluation in the treatment of ruminative vomiting was limited to

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clinical observations in the absence of empirical data or reports of uncontrolled single-subject studies. Although methodological standards of outcome studies have improved somewhat in recent years, with a few exceptions (e.g., Linscheid & Cunningham, 1977; Mulick et al., 1980; O’Neill, White, King, & Carek, 1979) current research still falls short of controlled experiments. Given this state of affairs, the elucidation of some methodological problems with the research in this area appears warranted; a brief section on methodological evaluation of the behavioral studies is provided in Section 111, D,3. 1. TREATMENT OUTCOME

I

a . Punishment Procedures Punishment has been defined as “the presentation of an aversive event or the removal of a positive event following a response which decreases the frequency of that response” (Kazdin, 1975a, pp. 33-34). A variety of aversive events have been employed to suppress ruminative vomiting in mentally normal and retarded persons including electric shock, bitter substances, and overcorrection. Although electric shock is now only infrequently used in applied settings, it is one of the most powerful punishing stimuli available today (Azrin & Holz, 1966). It has several advantages over other punishing stimuli used in aversive control (Rachman, 1965) and has been used to treat a variety of behavioral problems in children and adults (Rachman & Teasdale, 1969). With children, however, shock has normally been used in those cases which have presented lifethreatening problems (e.g., Bucher & Lovaas, 1968; Lovaas & Simmons, 1969) and have not responded to positive reinforcement procedures or to less intense aversive events. What is probably the first published use of electric shock in the treatment of rumination was reported by White and Taylor (1967). Although the study has serious methodological inadequacies (e.g., design, lack of adequate quantitative data) it strongly suggested that rumination could be controlled by aversive conditioning. White and Taylor were interested in suppressing rumination in a 23year-old severely retarded woman and a 14-year-old profoundly retarded boy. Medical examinations had excluded an organic etiology for rumination in both subjects and subsequent radiological studies excluded diverticuli and other physical aberrations as possible causes for their rumination. Preliminary behavioral observations indicated both subjects vomited during or immediately after meals and it was during this period that the treatment was in effect. Both subjects were shocked, for approximately 2 seconds whenever throat, eye, or coughing gestures signaled rumination. Only mild shock (400 V at 1 mA) was initially used but this was increased (500-700 V at I mA) later to make it more effective. The electrodes were attached to the legs of the female subject and on the hands of the male subject. White and Taylor (1967) reported a

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significant, but variable, reduction in rumination in both patients. They suggested the main function of the shock was to distract the subjects so that they could engage in other more adaptive behaviors.. Luckey, Watson, and Musick (1968) used mild electric shock to suppress vomiting and chronic rumination in a severely retarded 6-year-old boy. This subject had a 2-year history of rumination which became chronic with associated persistent vomiting during the 3 months before aversive treatment was initiated. Other treatments, including varied feeding schedules, different types and quantities of food, and continuous staff attention, had no significant effect on the frequency of vomiting and rumination. An anabolic steroid (Adroyd) was partially successful but this had to be discontinued after several weeks because of possible negative side effects. A 60-V battery source was used to deliver shock for 1 second to the subject’s waist contingent on ruminative vomiting. Although no baseline data are given, treatment data indicate a marked decrease in the frequency of ruminative vomiting by the fifth day. The therapeutic gains were maintained at a 3 month followup. In addition to this, informal observations indicated a general improvement in the patient’s behavior and no negative side effects due to aversive conditioning were reported. Kohlenberg ( 1970)described an experimental study with a 7-year-old severely retarded girl who had exhibited vomiting following every meal for a period of 3 months, and whose life was endangered by loss of body weight. Treatments were scheduled to follow each meal for a period of 1.5 hours, over a period of 3 days. Shock (peak voltage of 2250 V and current varying between 400 and 100 mA) was administered to the girl’s thigh for 1 second contingent on stomach tensions which preceded the vomiting response. Stomach tensions and vomiting were reduced to near-zero levels within 1 day. A ward-wide program was instituted after the 3-day experimental phase. If any vomitus was observed on the patient she was immediately confined to a chair and observed for 1 hour. If stomach tensions occurred during this period, they were punished by the ward personnel in exactly the same manner as during the experimental phase. Data for 25 days showed that the patient vomited only after 11 of the 75 meals. Furthermore, the vomiting during this phase was less severe and involved smaller amounts of vomitus when compared to baseline levels. The ward program was continued for 5 months and a near-zero level of vomiting was maintained. However, at 1 year follow-up the frequency of vomiting had reached baseline levels in the absence of a programmed maintenance procedure. The treatment procedure used by Luckey et al. (1968) was replicated by Galbraith et al. (1970) with a 13.5-year-old severely retarded boy who vomited up to 20 times per day. The vomiting was rapidly reduced and maintained at very low levels. However, in contrast to the previous study, Galbraith et al. reported the occurrence of negative side effects in their patient due to the aversive control

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procedure. There was an increase in his hyperactivity, masturbation, and selfinjurious behavior. This finding is consonant with previous reports documenting the desirable and undesirable side effects of punishment with infrahumans (Azrin & Holz, 1966) and humans (Johnston, 1972; Kazdin, 1972). In a study with a 14-year-old severely retarded boy, Watkins (1972) reported the treatment of vomiting using electric shock without the occurrence of any detectable negative side effects. The boy was extremely emaciated and his survival was in question. In a 7-week treatment program shock was used to punish vomiting or vomiting attempts. No programmed reinforcement procedures were used. In addition to the reduction of vomiting to very low levels, the study showed that negative side effects are not necessary concomitants to the use of aversive procedures. However, in this study, as in most others using aversive control procedures, the role of nonspecific treatment effects (e.g., increased staff attention, unfamiliar observers) has not been controlled for and its importance in the nonappearance of negative side effects needs to be investigated. In a similar study, Wright and Thalassinos (1973) treated a 4-year-old severely retarded female for ruminative vomiting. Shock (60 V at 3 mA) was used for 12 sessions and within that time vomiting was reduced from a base rate of 15 to one per 30-minute treatment session. A milder aversive program was instituted at the end of this period. Vomiting now resulted in the patient’s leg being slapped by the parents. A 6-month follow-up indicated maintenance of treatment gains. Although no data were presented, Wright and Thalassinos reported that their patient became “more alert and showed a higher level of cognitive functioning, improved interpersonal contact, and greater attentiveness to the environment. ” No negative side effects were observed. Despite methodological problems inherent in these case reports, the one consistent finding has been the efficacy of electric shock as an aversive stimulus in the suppression of vomiting and rumination in mentally retarded persons. Brief response-contingent electric shocks have also been used to control vomiting and rumination in nonretarded infants with whom other approaches had apparently failed (Cunningham & Linscheid, 1976; Lang & Melamed, 1969; Linscheid & Cunningham, 1977; Toister, Condron, Worley, & Arthur, 1975). These studies are important for two reasons. First, they show quite conclusively that even infants can be treated with a strong aversive such as shock and second, they exhibit methodological advances in terms of design, data collection, and execution when compared to previous studies. Lang and Melamed (1969) used electric shock to eliminate ruminative vomiting in a 9-month-old infant. Aversive conditioning was used only after several earlier treatments (e.g., dietary changes, antinauseants, mechanical devices, and intensive nursing care on a one-to-one basis) failed to provide adequate control of ruminative vomiting. Visually, the imminent onset of vomiting can be recognized by observing the throat movements (reverse peristalsis) which precede it

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but occur at no other time and mechanically, an EMG recording appartus can be used to detect reverse peristalsis. Lang and Melamed (1969) used both, the observation of a nurse and the EMG recording of muscle activity, to determine the onset of vomiting. An avoidance-conditioning paradigm was used in the treatment of this infant. One-second electric shocks were administered to the leg at 1-second intervals as soon as vomiting occurred and terminated when vomiting ceased. The shock level was determined subjectively: it was judged painful and unpleasant by the therapists and was sufficient to elicit signs of distress in the infant. The frequency and duration of vomiting decreased markedly within the first two feeding sessions and was suppressed completely by the sixth session. However, there was some spontaneous recovery after 2 days of nontreatment. Administration of the shock for a further 3 days resulted in the response being reduced to very low levels. The electromyographic recordings from the thorax and throat region used by Lang and Melamed (1969) to detect the physiological antecedents of the infant’s vomiting response were found to be unreliable by Toister et al. (1975) as predictors of the vomiting response. They found that no reliable physiological antecedent activity could be demonstrated when they took EMG recordings of the deltoid, trapezius, and sternocleidomastoid muscles. Toister et al. were concerned with the chronic vomiting of a 7.5-month-old infant. They replicated the treatment procedure used by Lang and Melamed (1969) except that shock was delivered on the basis of continuous observations of the infant’s behavior. Using a shock generator which delivered a brief pulse of 2.5 mA, they delivered shock to the infant’s calf for .5 second as soon as vomiting occurred and repeated it at .5-second intervals until it ceased. Vomiting was suppressed in 7 days. Follow-up at 8 months revealed no recurrence of vomiting. Cunningham and Linscheid (1976) also used an avoidance conditioning paradigm to control chronic rumination in a 9-month-old infant. Shocks of .5second duration were administered at 1-second intervals to the infant’s calf whenever ruminating was observed and terminated when it ceased. The shock intensity was initially set at .5 mA but this had to be increased (in .5-mA steps) to 4.5 mA to make it more effective. Rumination was suppressed within 2 weeks and a 6-month follow-up revealed no recurrence of the behavior. There is very little evidence for the generalization of response suppression effects when aversive control procedures are used with the mentally retarded (Birnbrauer, 1976). Treatment effects are generally situation and trainer specific and systematic generalization must be programmed (Stokes & Baer, 1977). In the Cunningham and Linscheid (1976) study, the maintenance of treatment gains was ensured by programming generalization across therapists and situations. This is one of the very few studies which systematically incorporated generalization training as a part of the procedure.

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In the best-controlled study reviewed so far, Linscheid and Cunningham (1977) used a reversal design to demonstrate the efficacy of electric shock in eliminating chronic ruminative vomiting in a 9-month-old infant. The treatment procedures were similar to those described by Cunningham and Linscheid (1976) although the intershock duration was reduced to.5 second in this study. The treatment program, conducted in a hospital setting, began by obtaining baseline observations on the frequency of rumination. After baseline, the aversive control procedure was invoked whereby a series of shocks was delivered each time a ruminating episode was observed and discontinued when it ceased. Rumination decreased dramatically to zero by the third day. When the baseline conditions were reinstated and response-contingentshocks were no longer in operation there was a systematic increase in rumination. The reintroduction of the shock contingency again resulted in a sharp decrease in rumination, demonstrating a functional relationship between rumination and the treatment program. In summary, the case report literature suggests that electric shock may be effective in eliminating ruminative vomiting. However, these reports do not lead to any definitive conclusions about the general effectiveness of electric shock because of methodological limitations. Indeed, only 1 of the 10 studies reviewed fulfilled all of the necessary design requirements for evaluative studies (cf. Baer, Wolf, & Risley, 1968), and, furthermore, most studies were deficient in several respects. Even though the increasing sophistication in the techniques of behavioral analysis has led to somewhat better studies in recent years, these studies should still be taken as preliminary, needing further documentation with appropriate controls. b . Overcorrection Another procedure which appears to be effective in the treatment of numerous behavior problems in the mentally retarded is a mild punishment technique developed by Foxx and Azrin (1972), called overcorrection. The rationale of overcorrection as stated by Foxx and Azrin (1973) is “(1) to overcorrect the environmental effects of an inappropriate act and (2) to require the disruptor intensively to practise overly correct forms of relevant behavior. The two components of this procedure have been termed restitution and postive practice, respectively. Although scant information is available regarding the parameters of overcorrection, the procedure itself appears to be based on a variety of behavioral components including extinction, time-out, and punishment. Three cases have been reported illustrating the use of overcorrection procedures in eliminating vomiting and chronic rumination in the mentally retarded. Azrin and Wesolowski ( 1975) employed a combination of self-correction and positive practice for habitual vomiting in the treatment of a 36-year-old profoundly retarded, nonverbal woman. They compared the efficacy of this treatment technique with two other frequently used behavioral techniques, required ”

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relaxation in bed (Webster & Azrin, 1973) and time-out by seclusion. During the required relaxation phase, the woman was required to lie down in her bed for 2 hours after each vomiting episode. During the time-out phase she was secluded in a room by herself for 30 minutes contingent on each vomiting response. Following this, self-correction and positive practice overcorrection was instituted. Self-correction required the woman to clean up her vomitus and change her clothes or bed sheets if they had been soiled. Once self-correction was completed she was required to engage in 15 trials of positive practice. This involved the woman being taken to the toilet where she bent over the bowl for several seconds with her mouth open and then flushing the toilet. As a preventive measure, she was reminded every hour during the day of the consequences of situationally inappropriate vomiting. Required relaxation was not an effective technique in the control of vomiting in this patient. Time-out proved to be only partially successful although the treatment was terminated while the response rate was decelerating. However, vomiting was eliminated with overcorrection within the first 2 weeks and follow-up data at 1 year showed the maintenance of complete suppression. Azrin and Wesolowski (1975) suggested that positive practice and selfcorrection were not only very effective, they also taught the woman the correct mode of reacting to an urge to vomit. In this study, positive practice and self-correction procedures were imposed as the third treatment (after required relaxation and timeout) and for a substantially longer period of time than the other treatments. The use of this design (i.e., an ABCD design) leads to problems in the interpretation of the data. The design is not able to overcome the possibility of sequential confounding and timecorrelated artifacts which usually occur when two or more treatments are tested for several sessions one after another. It is difficult to evaluate the reliability or replicability of an effect if proper experimental controls are not used. Thus, it would appear that in the absence of additional data from methodologically sound studies, Azrin and Wesolowski’s (1975) claims about the general effectiveness of their procedure may be an overstatement of their data. Restitutional overcorrection procedures were used by Duker and Seys (1977) to eliminate vomiting in a 19-year-old profoundly retarded female. Contingent on each vomiting episode the patient was required to wash her face with cold water and to clean the area where the vomit was, the floor, window sill, and walls. Following this, she was required to change into new clothes. Using a repeated reversal design, Duker and Seys demonstrated quite clearly a functional relationship between overcorrection and vomiting in this patient. A 5-week follow-up at 2 months showed that the frequency of vomiting was maintained at near-zero levels. Simpson and Sasso (1978) reported a case in which a multicomponent treatment package, perhaps incorrectly labeled overcorrection, was used to treat a 10-year-old severely disturbed and functionally retarded boy with chronic rumi-

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nation. Contingent on each rumination response, he was verbally reprimanded and made to swallow it. Swallowing of the vomitus was followed by lemon juice therapy (Sajwaj et a l . , 1974) in which the subject was required to swallow 15 to 20 ml of unsweetened lemon juice which had been squirted in his mouth. Following this procedure, the subject’s lip and exterior mouth area were washed with soap and water for 30 seconds. Finally, face cream was massaged on his lips and exterior mouth area for an additional 45 seconds. During baseline the subject spent 44% of his time ruminating. Introduction of the treatment package resulted in a dramatic reduction of rumination. Removal of the behavioral contingencies resulted in a gradual increase in rumination, and a reintroduction of the procedures once again resulted in response suppression. Some anecdotal evidence was presented suggesting a strong situational generalization effect. Although the procedures used by Simpson and Sasso (1978) appeared to be effective in eliminating the occurrence of rumination in this patient, it is unclear which aspects of the treatment procedure accounted for most of the therapeutic gains. It has been shown, for example, that lemon juice therapy is by itself a highly effective procedure in the treatment of rumination (Sajwaj et a l . , 1974; Turner, Sajwaj, & Becker, 1977) and masturbation in a severely retarded boy (Cook, Altman, Shaw, & Blaylock, 1978). Clearly, an evaluation of the contribution of individual components is warranted. It has been mentioned that the term overcorrection may not be entirely correct as a description of the procedures used by Simpson and Sasso (1978). Not only does their treatment package include a purely punishment procedure (i.e., lemon juice therapy) which in no way forms a part of the overcorrection technique, it also does not meet one of the requirements of a proper overcorrection procedure as stated by Foxx and Azrin (1972). They maintain that restitution and positive practice should be actively performed by the patient since the physical effort required in its performance is thought to be aversive (see Murphy, 1978, and Ollendick & Matson, 1978, for reviews of overcorrection). Perhaps it is instructive to reiterate at this point the other three major characteristics of overcorrection: (a) Overcorrection responses should be topographically related to the inappropriate behaviors (Foxx & Azrin, 1972). There is some evidence, however, which suggests that this component may not be a critical aspect of the overcorrection procedure (Doke & Epstein, 1975; Epstein, Doke, Sajwaj, Sorrell, & Rimmer, 1974; Ollendick, Matson, & Martin, 1978; Roberts, Iwata, McSween, & Desmond 1979; Wells, Forehand, Hickey, & Green, 1977). (b) Overcorrection should be contingent on an inappropriate behavior and it should be executed immediately. This means that extinction contingencies would be in effect for the inappropriate behavior. Azrin and Powers (1975) provide the only experimental evidence showing that the immediate contingent application of overcorrection provides better control of inappropriate behaviors than when it is delayed. (c) Overcorrection should be extended in duration. Studies reporting

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success with the overcorrection procedure have used varying treatment durations. With self-injury, for example, treatment durations have ranged from a few seconds to 20 minutes (Duker & Seys, 1977; Freeman, Graham, & Ritvo, 1975; Singh, Dawson, & Gregory, 1980; Webster & Azrin, 1973) without any differential effectiveness. Clearly, more research is needed to evaluate the necessary and desirable conditions for the application of the overcorrection procedure and more extensive analyses are required to evaluate the contribution of individual components. c . Bitter Substances Bitter substances have been used as aversive events in the treatment of maladaptive behaviors in children. Parents commonly use something bitter (e.g., spiced mustard) on an infant’s thumb to inhibit thumbsucking. The first use of bitter substances as punishing stimuli for rumination was reported by Clark (1956). Quinjne was used with an infant’s milk, presumably to make the regurgitated contents aversive to reswallow. Although this treatment was apparently successful, only anecdotal evidence is available for its efficacy. Two substances have been used with ruminators, on an experimental basis, namely, lemon juice and pepper sauce (Tabasco brand). Sajwaj et al. (1974) demonstrated successful treatment of rumination in a 6-month-old infant via punishment with lemon juice. Five to 10 milliliters of real lemon juice was squirted into the infant’s mouth whenever rumination or its precursors were detected. During baseline, the infant ruminated during 40 to 70% of the time following a feeding in a 20-minute session. Lemon juice therapy reduced this to below 10% of the time. Withdrawal of the treatment contingencies resulted in a return to high levels of rumination. Reintroduction of lemon juice therapy again reduced rumination to near-zero levels. With the suppression of rumination and an increase in body weight, the infant became more attentive to adults, and began to smile, babble, and grab objects near her. No negative side effects were reported. A similar success with lemon juice has been reported by Becker, Turner, and Sajwaj (1978). Bright and Whaley (1968) were the first to use pepper sauce with an 1 1-yearold severely retarded male who regurgitated his food and indulged in rumination for as long as 2 hours after each meal. It was hypothesized that if the subject’s regurgitation was reinforced and maintained by his rumination, the elimination of rumination should result in its extinction. Bright and Whaley punished the ruminating response by sprinkling pepper sauce on the vomitus thereby making its reconsumption aversive. When compared to the baseline, there was a dramatic reduction in the rate of rumination but only a slight decrease in the patient’s regurgitation. Although pepper sauce proved to be effective, its use had to be terminated after only 10 days since the patient was still regurgitating and the consequent weight loss posed the problem of malnutrition and dehydration. To

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hasten the treatment, response-contingentelectric shock was used as the aversive stimulus for both responses, regurgitation and rumination. Both responses were eliminated within three sessions. The effectiveness of pepper sauce could not be fully tested in this study since it was used for only a limited time period. However, it was clear that pepper sauce had only a minimal effect on regurgitation. And, what of Bright and Whaley’s hypothesis that “a primary behavior in a chain (regurgitation) can be suppressed through punishing a secondary behavior (rumination)”? The data do not support this contention. It is possible that both responses could have been eliminated if only the primary behavior (regurgitation) was punished. Research evidence (e.g., Aronfreed & Reber, 1965) suggests that punishment tends to be more effective if it is delivered early in the response chain. If a response chain is completed (i.e., when the final link of a response chain has resulted in reinforcement) then punishment of that response means the suppression of a reinforced response, which is theoretically a more difficult process than the suppression of a nonreinforced response. This notion was tested in an experiment by Singh (1979), who evaluated the differential effects of lemon juice and pepper sauce in the treatment of rumination. In this study, only the first link of the response chain (tongue thrusting backward and forward) was punished. In the first experiment, 5 to 10 ml of pure lemon juice was used for 20 days as the aversive event with a 4.8-year-old profoundly retarded boy who ruminated for about an hour following each meal. Introduction of the lemon juice contingency showed an initial decrease in the subject’s response rate when compared to the baseline. However, from the fourth day the rate began to increase until it approximated the baseline rate. After a reversal period, 5 to 10 ml of pepper sauce (diluted with water 4: 1) was used as the response-contingent aversive event. There was a dramatic reduction in the subject’s response rate within a few sessions and rumination was later completely suppressed. A follow-up at 12 months showed a complete absence of rumination. The efficacy of pepper sauce in the treatment of rumination was further tested in a second experiment with a 6-year-old profoundly retarded boy. It was shown, by using a reversal design, that punishing the initial link of the response chain resulted in the suppression of rumination. Singh (1979) suggested that the procedural difference could account for the discordance in the results of this and the Bright and Whaley (1968) study. The data provided by Singh (1979) support the contention that, to be maximally effective, aversive contingencies should be applied to the primary behavior in a response chain. d . Withdrawal of Positive Reinforcement Daily vomiting in a 9-year-old mentally retarded girl was successfully treated by Wolf et al. (1965, 1970), who used an extinction procedure. Extinction is the withdrawal or withholding of positive reinforcement from a previously rein-

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forced response. Preliminary observations had indicated that the child’s in-class vomiting was reinforced and maintained by the teacher since she permitted the child to leave the classroom and return to the dormitory following each vomiting response. During extinction, the teacher was instructed to ignore the vomiting and the child was not permitted to withdraw to her room until school ended. In addition, the teacher was instructed to reward her with praise and candy for appropriate classroom behavior but to terminate this procedure during vomiting episodes. After a slight initial increase following the introduction of the extinction procedure, vomiting ceased by the end of 30 class days. Removal of the extinction procedure resulted in a return of vomiting and its reintroduction led to a final cessation of the behavior. The use of a reversal procedure demonstrated clearly that vomiting in this child was maintained by the teacher allowing her to leave the classroom following each vomiting episode. Smeets (1970) found that manipulating the social contingencies of an 18year-old profoundly retarded boy was effective in controlling his vomiting and rumination. This boy, who had a 14-year history of this behavior, vomited and ruminated during the entire observation period which consisted of the patient’s total mealtime. During the initial 3 weeks of treatment, the first signs of rumination or regurgitation resulted in his meal being taken away. He was given sweets if he did not ruminate or vomit in the presence of his usual mealtime attendant. This resulted in a decrease in rumination and an increase in the patient’s weight. Socially, he was more alert and took more notice of his environment. The second phase of treatment took advantage of this change in the patient’s behavior. For the next 5 weeks, regurgitation and rumination resulted in (1) the rest of his meal being taken away, and (2) being immediately deprived of social contact with the mealtime attendant. The attending nurse was required to close the blinds and depart for a half hour without changing the patient’s diapers. If the patient did ruminate or vomit, he was placed on a chair in front of rhe open door from where he could interact socially with the nursing staff. Smeets (1970) reported that while rumination and vomiting were not totally eliminated, they gradually decreased over the 5-week period to near-zero rates. In a final study, Smith and Lyon (1976) scheduled extinction for vomiting and reinforcement for its nonoccurrence in the treatment of a 25-year-old profoundly retarded girl. If the patient had not vomited during a 30-minute period, the staff praised and verbally interacted with her. However, vomiting resulted in her being ignored for 30 minutes. Vomiting was eliminated in 3 weeks and a 30-day follow-up at 11 months showed only two occurrences on day one with no other episodes during the final 29 days. Why the occurrence of rumination during follow-up should suddenly cease, apparently without the treatment being reintroduced, was not explained by Smith and Lyon (1976). The results of these studies cannot be taken as evidence for the efficacy of extinction procedures. Methodologically, these studies leave a lot to be desired.

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Two studies used AB designs and one used a BAB design, with none reporting interobserver reliability data. Because of the serious limitations of these studies, it can be only tentatively concluded that extinction procedures may provide some control of rumination in mentally retarded persons. Certainly, this area of research merits further investigation. Various other studies, with mentally normal populations, have indicated that extinction procedures may be effective in the treatment of ruminative vomiting (e.g., Alford, Blanchard, & Buckley, 1972; Sheinbein, 1975; Wright, Brown, & Andrews, 1978). However, this demonstrated efficacy must be balanced by the consideration that the behavior change with this procedure tends to be much slower than that resulting from the punishment techniques discussed above. A gradual decrease in the response rate may result in the execution of a large number of responses before ruminative vomiting is finally extinguished. Extinction may be an inappropriate technique to use if the patient’s condition is lifethreatening and immediate intervention is required. Other considerations should also be noted when extinction is chosen. For example, the frequency of vomiting or rumination may increase, compared to baseline levels when extinction procedures are first introduced. Such an increase may actually prove harmful to the patient. Also it is entirely possible that the behavior may be inadvertently reinforced during this burst of responses, resulting in even higher rates of inappropriate responding. e . Food Satiation Extinction procedures require the withholding of reinforcement from a previously reinforced response. Another way of manipulating the reinforcement contingencies is by reducing or removing the reinforcing qualities of the reinforcer. Within limits, the magnitude of reinforcement is directly related to performance. However, a reinforcer can lose its reinforcing qualities when given in excessive amounts. This process is termed satiation and has been used in a variety of applied settings to control a variety of behavior problems (e.g., AylIon, 1963; Welsh, 1971). Jackson, Johnson, Ackron, and Cowley (1975) used a food satiation procedure to decelerate the frequency of vomiting in two profoundly retarded males. The treatment consisted of allowing the patients to eat all of the food they could consume. The food satiation condition required the first patient to eat double portions of the standard meal in addition to cereal, ice cream, and milk shakes. The second patient was required to eat all of the soft diet food he could eat. The criterion for satiation for both patients was the refusal of food twice with a 1-minute interval between the food refusals. There was a 94% reduction of vomiting in the first patient but only 50% in the second. The reduced level of vomiting was maintained at a 10-day follow-up. It was suggested that the probability of the patient’s vomiting was decreased because the reconsumption of the

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vomitus (which reinforced the vomiting response) decreased in reinforcer effectiveness as a result of food satiation. Libby and Phillips (1978) provided a second example of the use of food satiation in the elimination of rumination in a profoundly retarded boy. Although adequate methodological controls were not used, the results of this study suggest that vomiting and rumination may be rapidly eliminated by food satiation. Foxx, Snyder, and Schroeder (1979) tested the efficacy of food satiation by itself and in combination with a punishment procedure, called oral hygiene, in two profoundly retarded adults. The oral hygiene procedure required the subjects to clean their teeth and gums with Listerine for 2 minutes following each episode of rumination. The effects of treatment, which was carried out only during the lunch periods, were evaluated via a multiple-baseline across-subjects design. The introduction of food satiation resulted in a decrease in rumination and even further decreases were observed when satiation was combined with oral hygiene. Generalization of treatment effects were observed during breakfast and dinner meals. During follow-up, oral hygiene was used following all meals but satiation was restricted to only one meal daily. The follow-up data showed that rumination was maintained at near-zero levels during the 16-week period. Foxx et al. suggested that satiation in combination with oral hygiene could be a very effective technique for controlling non-life-threatening rumination in retarded individuals. The efficacy of the oral hygiene component when used in the absence of satiation, however, has yet to be determined. f. Combined Treatment Procedures Treatment procedures which have multiple components may have a central conceptual focus (e.g., overcorrection) or may be put together to rapidly bring under control an intractable behavioral problem. In the latter case, the basic strategy is to determine whether the combined treatment procedures produce the desired therapeutic outcome. Although this procedure may detract from the analytical value of the data, it is irrelevant in terms of its practical or treatment value. A good example of this procedure is provided by Murray, Keele, and McCarver (1976). [What appears to be the same case report was published in another journal the following year (Murray, Keele, 8i McCarver, 1977).] They used a seven-component procedure in the treatment of a nonretarded 6-month-old boy who was hospitalized in a seriously malnourished condition due to ruminative vomiting. Attention appeared to maintain this behavior since the infant’s mother and the nursing staff paid considerable attention to the infant whenever he vomited. Treatment included the following procedures: stimulus control (thickened feedings), attention during feeding, punishment (withdrawal of positive reinforcement), punishment (pepper sauce), extinction, and differental reinforcement of incompatible behavior. Rumination was eliminated in 10 days. To facilitate generalization of the treatment, the mother was given instructions on the treat-

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ment procedure before the infant was discharged. A 4-month follow-up showed the infant had nearly doubled his hospitalization weight and no further episodes of ruminative vomiting had occurred. Although the effects of this treatment procedure were immediate and longlasting, it is impossible to delineate which aspects of this treatment accounted for the change. In a treatment such as this, where a large battery of procedures has been used, it would be useful to ascertain which components are necessary, sufficient, or facilitative in terms of treatment effects. While the combination of reinforcement and punishment procedures represent an unusually powerful and efficient behavior change technique, the use of a seven-component procedure may well be a case of behavioral overkill. This is especially so when it has been shown that several of the components are effective even when presented alone (e.g., pepper sauce, extinction, differential reinforcement of other behavior). g. Special Feeding Technique Ball, Hendricksen, and Clayton (1974) reported a study which compared the effects of standard institutional and a special feeding technique in the treatment of chronic regurgitation in two profoundly retarded patients. The standard institutional technique involved no active participation from the patient in the feeding process. Active participation was required, however, in the special feeding technique. Using a reversal design with the first patient, Ball et al. (1974) were able to show that regurgitation could be eliminated by their special feeding technique. Although a full reversal design could not be used, this success was replicated with a second subject.

h . Differential Reinforcement Procedures Maladaptive behaviors in the mentally retarded can also be decreased by increasing other, socially adaptive, behaviors. One way of doing this is by ignoring instances of maladaptive behaviors, such a ruminative vomiting, and reinforcing the Occurrence of alternative or incompatible behaviors. This technique is commonly referred to as differential reinforcement procedures. When the behavior being reinforced is other than rumination, the procedure is called differential reinforcement of other behavior (DRO). Variations of this procedure include DRI (reinforcement of incompatible behavior) and DRL (reinforcement of low rate of the maladaptive behavior). O’Neil et al. (1977) tested the efficacy of a DRO procedure in the control of rumination in a severely malnourished 26-month-old girl. A multifaceted treatment program which included, in different phases, punishment with lemon juice and knuckle tapping and time-out from positive reinforcement was used. They were able to show via a single-subject reversal design a functional relationship between the child’s rumination and the use and withdrawal of the DRO procedure. Lemon juice was found to be only minimally effective although the period

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of its use was limited to only four sessions. Generalization was achieved by the use of a combination of procedures and at the termination of intervention, rumination was controlled by social consequences. Although this study was well executed, the data pertaining to the efficacy of the DRO procedure may have been confounded by sequence effects. This point was nicely acknowledged by O’Neil et al., who noted that DRO was initially paired with a punishment procedure and was then presented by itself. In the absence of additional data, the effects of DRO without a history of punishment still remain to be determined. In a more recent study, Mulick et al. (1980) used a multiple schedule withinsubject design to compare the effects of DRO with three other treatments. During the DRO condition, periods of no vomiting scheduled reinforcement. In the second treatment (DRI), periods of no vomiting and sustained toy play were followed by reinforcement and the lack of either postponed reinforcement. In the third treatment (extinction), vomiting was ignored and in the fourth treatment (extinction and alternative behavior), vomiting was ignored and alternative behaviors were reinforced. Mulick et al. found that DRO by itself was not very effective in the control of ruminative vomiting. The best results were achieved when vomiting was ignored and alternative behaviors were systematically reinforced. These results are consistent with previous findings from the self-injury literature which suggest that the reinforcement of specified incompatible behavior is more effective than the reinforcement of unspecified alternative behavior (e.g., Tarpley & Schroeder, 1979). However, whether these experimental results can be translated into actual practice in the clinical situation still remains an empirical question. 2. SIDE-EFFECTS OF PROGRAMMED TREATMENT

Basic research in operant conditioning indicates that behavior such as escape, avoidance, and aggression often occurs as a result of punishment (Azrin & Holz, 1966). The data from applied studies are equivocal. Reviews of studies with humans (e.g., Johnston, 1972) suggest that such negative effects are rarely reported in experiments using punishment although, periodically, reports appear in the literature documenting evidence for negative side effects (e.g., Mayhew & Harris, 1978; Rollings et al., 1977). Studies using punishment procedures in the treatment of ruminative vomiting generally report positive side effects. Most studies reported a general improvement in the social behaviors of the subjects (e.g., Becker et al., 1978; Cunningham & Linscheid, 1976; Lang & Melamed, 1969; Luckey et al., 1968; Sajwaj et al., 1974; Wright & Thalassinos, 1973), an increase in their social and motor activity to normal levels (e.g., Bright & Whaley, 1968; Cunningham & Linscheid, 1976; Sajwaj et al., 1974), increase in play (e.g., Becker et al., 1978; Luckey et al., 1968; Sajwaj et al., 1974), and higher levels of cognitive functioning (e.g., Wright & Thalassinos, 1973). Although punishment often leads to the

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avoidance of the person delivering it, White and Taylor (1967) reported that their subjects appeared to be more aware of and interacted more with the therapists than with other staff members. Luckey et af. (1968) reported that in addition to a general improvement in their patient’s social behavior, there was a concomitant decrease in tantrums and excessive motor activity as a consequence of the treatment. Symptom substitution was reported in only two case reports (Becker et a f . , 1978; Galbraith et al., 1970). It has been repeatedly noted that psychodynamic approaches, and in particular psychoanalytic theory, predict that removing a symptom while ignoring the underlying cause of the disorder will result in either the recurrence of that symptom or the appearance of a substitute symptom (see Eysenck, 1969; Ullmann & Krasner, 1965). It is a moot point whether this can be empirically tested, as Bandura (1969) has already pointed out, since its adherents have specified neither the nature of the substitute symptoms nor the contingencies which reliably predict its occurrence. In line with Cahoon (1968), symptom substitution will be used here to refer to undesirable behavioral side effects, without recourse to “underlying causes” as an explanatory construct. Within this framework, the appearance of head-slapping , rocking, and head-weaving in the Becker et al. (1978) study and the increase in hyperactivity, incessant talking, masturbation, hair pulling, and self-mutilation which occurred as a result of the treatment in the Galbraith er al. (1970) study, can be classed as symptom substitution. Several hypotheses have been advanced to account for symptom substitution and the collateral development of positive behaviors. Lovaas, Frietag, Gold, and Kassorla ( 1963, for example, suggested that stereotypic behaviors in the response repertoires of retarded persons may be arranged in a hierarchy according to their probability of reward and punishment. The individual is thought to sample his behaviors in different environmental contexts to determine which has the highest probability of reinforcement. In terms of treatment effects, the reduction of one behavior should lead to an increase in another, if both are governed by the same set of contingencies. The new behavior need not necessarily be maladaptive. A fuller discussion of this and other hypotheses for symptom substitution is provided by Baumeister and Rollings (1976). 3 . METHODOLOGICAL CONSIDERATIONS

Table I1 presents a methodological analysis of the behavioral studies which have used mentally retarded children as subjects. The studies presented in the table reflect considerable methodological shortcomings. Most of the investigations were clinical case reports of single patients and the majority of these did not even include single-subject methodology. Single-subject studies provide useful information about a treatment technique only if adequate controls are used (cf. Lazarus & Davison, 1971; Leitenberg, 1973).

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The most frequently used design was of the AB type, where A refers to the baseline period and B to the experimental or treatment program. The two earliest studies (Luckey et al., 1968; White & Taylor, 1967) did not report quantitative baseline data. The most serious problem with the use of the AB design is that the therapist is unable to demonstrate a clear functional relationship between the target behavior and the experimental or treatment contingencies. Although the frequency of ruminative vomiting decreased rapidly in all these studies commensurate with the introduction of treatment, this change could have been a function of events other than the programmed intervention. For example, in most of these studies it is impossible to exclude the possibility that nonspecific treatment effects (e.g., presence of experimenters, changes in ward routine, and attitude of ward attendants) could account for the observed behavior change. The reversal or ABAB design is the most frequently used single-case experimental design in applied research (Kazdin, 1975b). This design requires that the treatment contingencies be presented and temporarily withdrawn at some point in time to demonstrate the effect of the intervention. A causal interpretation of intervention effects is possible if the target behavior changes systematically during the different phases. Five studies (Ball et al., 1974; Becker ef af., 1978; Jackson et af., 1975; Simpson & Sasso, 1978; Singh, 1979) in Table I1 used ABAB designs, with Duker and Seys (1975) using a repeated replication (ABABAB) design. Two studies tested the efficacy of different intervention strategies using either an ABC (Bright & Whaley, 1968) or an ABCD design with a single subject (Azrin & Wesolowski, 1975). A casual interpretation of the results in both these studies is difficult because of the lack of systematic reversals between treatments and order effects of treatment. However, a dramatic decrease in the target behavior produced by only one treatment does provide suggestive rather than definitive evidence for the effects of that treatment. The use of a simultaneous treatment design (Browning, 1967; Kazdin & Hartman, 1978) would have overcome these problems since it allows the comparison of two or more different treatments with an individual subject. A particularly noteworthy study in this respect has recently been reported by Mulick et al. (1980) who used a multipleschedule within-subject design to test the effects of four different treatments. Another methodological issue concerns the reliability of the reported data in these studies. The demonstration of an acceptable level of interobserver agreement is crucial since it sets the upper limit to the validity of inferences derived from the data. Only nine (Ball et al., 1974; Becker et al., 1978; Foxx ef al., 1979; Jackson et al., 1975; Kohlenberg, 1970; Libby & Phillips, 1978; Mulick et al., 1980; Simpson & Sasso, 1978; Singh, 1979) of the 20 studies listed in Table I1 provided data on interobserver agreement. Four studies (Becker et al., 1978; Foxx et al., 1979; Jackson ef af., 1975; Singh, 1979) calculated interobserver agreement in terms of percentage agreement using a given formula and

TABLE I1 A METHODOLOGICAL ANALYSIS OF BEHAVIORAL STUDIES Study

-2

Treatment

Design

WITH

MENTALLY RETARDED SUBJECTS~**

Interobserver agreement

Generalization

Follow-up

-

-

-

-

White and Taylor (1967)

Electric shock

Luckey, Watson, and Musick (I%@ Kohlenberg ( 1970) Galbraith, Byrick, and Rutledge (1970) Watkins (1972) Wright and Thalassinos (1973) Azrin and Wesolowski (1975)

Electric shock

B (Subject 1) B (Subject 2) B

Electric shock Electric shock

AB AB

-

Electric shock Electric shock

AB AB

-

3 months 6 months

Required relaxation, time-out, positive practice, and self-correction Restitutional overcorrection Lemon juice, overcorrection Lemon juice

ABCD

-

1 year

ABABAB

-

ABAB

3 observers:

ABAB

2 observers:

ABC

-

ABAC (Expt 1 )

2 observers:

Duker and Seys (1977) Simpson and Sass0 (1978) Becker, Turner, and Sajwaj (1978) Bright and Whaley (1968) Singh (1979)

Pepper sauce, electric shock Lemon juice, pepper sauce

ABAB (Expt 2)

2 observers:

100% agreement

Yes, ward staff

-

-

25 days -

Yes, ward staff

2 months

100% agreement

-

-

89% agreement

Yes, parents

6 months -

86.5-1006 agreement (Expt 1 ) 85-966 agreement (Expt 2)

-

1 year

Wolf, Bimbrauer, Williams, and Lawler (1965)' Wolf, Birnbrauer, Lawler, and Williams (1970) Smeets ( 1970) Smith and Lyon (1976) Jackson, Johnson, Ackron, and Crowley (1975)

5 w

Extinction

BAB

Extinction, differential reinforcement Extinction, differential reinforcement Food satiation

AB AB ABAB (Expt 1)

2 observers:

ABA (Expt 2)

%-loo% agreement (Expt 1) %-loo% agreement (Expt 2) r = .%

Libby and Phillips (1978)

Food satiation

AB

5 observers:

Foxx, Snyder, and Schroeder (1979)

Food satiation, oral hygiene

ABC (multiple baseline)

Ball, Hendricksen, and Clayton (1974)

Special feeding technique

ABAB (Subject 1)

Several observers: 87.99-99.8% agreement (Subject 1) 99.1-99.5% agreement (Subject 2) 87% agreement 2 observers: (Subject 1)

NA

1 year

NA

1 year

Yes, programmed maintenance procedure

10 days

Yes, programmed maintenance procedure Yes, unprogrammed

3 months

NA

NA

16 weeks

AB (Subject 2) Mulick, Schroeder, and Rojahn (1980)

Differential reinforcement, extinction

ABCDE (multiple schedule)

2 observers:

RStudiesare presented in order of their appearance in Section III,D. Abbreviations used: A, baseline; B,C,D,represent treatment techniques; NA, not applicable. Follow-up data are presented in the second (1970) paper.

(Subject 2) r = .80 to .97

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two studies (Libby & Phillips, 1978; Mulick et al., 1980) used correlation coefficients to calculate interobserver agreement. The other studies failed to report the statistical procedure used to calculate agreement. It is important to include this information since interobserver agreements vary with the calculation method employed and the rate of the behavior (Haynes, 1978). Furthermore, no studies provided specific information on other variables which are known to affect the accuracy of observers (e.g., overt or covert methods of assessment, the schedule of assessing observer accuracy, observer drift). Only 5 of the 20 studies reviewed in Table I1 (Becker et al., 1978; Duker & Seys, 1977; Jackson et al., 1975; Kohlenberg, 1970; Libby & Phillips, 1978) reported programmed generalization as a component of their treatment procedure. It is usual for response change to occur and be maintained only in those environments in which systematic contingencies have been applied. Generalization has to be programmed to ensure that the behavior change is maintained beyond the treatment setting. Although most of the studies reviewed did not report generalization data, some reported generalization effects as an unprogrammed side effect of treatment (e.g., Simpson & Sasso, 1978). However, we need to take note of the dictum of Baer ef al. (1968) that the transfer of newly acquired behaviors must be specifically programmed rather than left to chance. Several studies reported on the maintenance of therapeutic gains once the intervention had been terminated. In some cases, long-term follow-up was programmed (e.g., Becker etal., 1978; Foxx et al., 1979; Singh, 1979) but in most cases it was presented on an ad hoc basis depending on the availability of medical notes after the patients’ routine checkup. Several studies indicated response maintenance for a period of up to a year. In general, it can be concluded that the number of studies which meet the current requirements of methodological rigor in applied behavior analysis is small indeed. Of utmost importance are studies which permit a clear evaluation of the comparative effectiveness of different treatment procedures, generalization data, and programmed periodic follow-ups.

IV. SUMMARY AND CONCLUSIONS The major focus of this article has been on the results of treatment outcome research, with a special emphasis on methodology. The treatment of rumination has been approached from various therapeutic perspectives including psychopharmacological, surgical, psychodynamic and psychotherapeutic, and behavioral; however, no single treatment has been accepted or recognized as the most effective. A review of the current literature contraindicates the use of psychopharmacological and surgical interventions although further research with some

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methodological rigor is clearly warranted before a more definitive conclusion can be reached. The psychodynamic approaches have focused on the long-term effects of treatment, with the literature being notable for its preoccupation with the etiology and theoretical dynamics of this disorder. The results of psychodynamic therapy have been rather vague, with most studies relying upon global impressions to assess treatment outcome. The psychotherapeutic studies concentrated on the disordered mother-child interaction and familial disharmony as variables of major importance in this disorder. In terms of treatment, the proponents of this approach emphasized the need for totally removing the patient (via hospitalization)from his family and the provision of a warm and loving mother substitute. Therapeutic counseling was also provided to the parents since it was emphasized that the patient usually returns to the home and family environment, where treatment gains have to be maintained. Also, the cessation of rumination is not accepted as a sufficient criterion for improvement and the restructuring of the family dynamics has been thought to be necessary to prevent a relapse after discharge from the hospital. Furthermore, if one assumes as a logical corollary of the psychotherapeutic approach that the dynamics of this disorder involve pathology within the family then the benefits of involving the parents in treatment are theoretically and clinically apparent. It has been evident that most of the psychotherapeutic case reports were not designed to be empirical studies but were reported as afterthoughts. However, based on the available data, it does appear that something “worked” although the exact nature of these causal variables remains in the realm of speculation. What emerges from the present review is the scarcity of well-designed and tightly controlled investigations supportive of the value of psychotherapy in the treatment of rumination. Furthermore, it suggests that extreme care must be taken in interpreting studies which do not have the necessary experimental controls. Finally, the practical relevance of psychotherapeutic techniques in the treatment of rumination in mentally retarded persons deserves to be mentioned. If one takes the Singh and Dawson (1980) prevalence data to be indicative of the type of subject who requires treatment for rumination then it is apparent that these techniques may have little, if anything, to offer. However, since psychotherapeutic techniques have been used in only one study with the mentally retarded the effectiveness of this form of therapy with this population still remains an empirical question. Although a variety of behavioral treatments for rumination have been reported, the general lack of methodological rigor in this literature renders definitive conclusions about the various techniques rather premature. With one exception, all the studies which have attempted to demonstrate the effects of responsecontingent electric shock on rumination are little more than case reports. Indeed, it would be impossible to replicate these studies. Consequently, little can be

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inferred about the treatment effects in terms of durability, generalization, and the development of collateral behaviors. Obviously, it is imperative that the suppression achieved through response-contingent electric shock is not transient, limited to specific settings, or solely under the discriminative control of the therapist. The meager evidence available on the use of overcorrection procedures in the treatment of rumination makes inferences about its efficacy highly tenuous. Although Azrin and Wesolowski (1975) and Duker and Seys (1977) suggest that overcorrection can effectively and immediately control rumination in profoundly retarded persons, several methodological and practical issues remain unclear. For example, overcorrection consists of a number of distinct behavioral techniques, including extinction, timeout from positive reinforcement, physical restraint, response prevention, prompting, and the reinforcement of competing responses. Since component analysis of overcorrection has so far been a neglected area of research, it is difficult to specify the contributing effects of each variable to treatment outcome. Other considerations include the finding that overcorrection does not always work (cf. Rollings, Baumeister, & Baumeister, 1977) and when it does work, its effectiveness appears to be limited to the training setting (Foxx & Azrin, 1973). A practical consideration in the evaluation of overcorrection as a general method of treatment for rumination is its feasibility. It is difficult to imagine how this procedure can be effectively implemented when the majority of the persons requiring treatment are severely and profoundly retarded. In the Azrin and Wesolowski (1975) study, the patient is described as a nonverbal profoundly retarded woman who was considered the most disruptive of all residents on her ward because of her screaming, hyperactivity, and vomiting. Obviously it would take an extremely skilled therapist to make such a patient engage in behaviors such as cleaning up her own vomitus, changing her clothes or bedsheets if they had been soiled, and then engage in 15 trials of positive practice. Furthermore, it may not always be feasible to use this procedure in many institutions because their large patient-staff ratios would exclude the possibility of such a complex and time-consuming procedure being implemented consistently. While the efficacy of lemon juice therapy in the treatment of infant rumination has been attested to in two well-controlled studies (Becker etal., 1978; Sajwaj et a!., 1974), caution must be exercised in its general use because of potential medical complications (e.g., aspiration into the lungs, and irritation of the mouth). Furthermore, this procedure may be useful only with infants since at least one study with an older child showed it to be ineffective (Singh, 1979). Older children may require a more potent punisher, such as pepper sauce, to control rumination. With the exception of one study (Singh, 1979), the effects of bitter substances with older children and adults remain virtually unstudied. At this point, it is too early to draw definitive conclusions about the efficacy of procedures such as extinction, food satiation, special feeding techniques, and the

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differential reinforcement of other behaviors. The problem has been that these techniques have received only transient attention from researchers in this area and no programmatic research with any one technique has been evident. In general, it is apparent that most of the behavioral studies reviewed in this article do not meet the standard of experimental rigor which is necessary for a demonstration of a functional relationship between a treatment technique and the resulting behavior change. Even such basic requirements as adequate baseline data, full details of the subject, use of internally valid experimental designs, and interobserver reliability data were found to be missing with monotonous regularity. Other factors which have not received sufficient attention, include the durability or maintenance of the observed behavioral change and the generalization of treatment effects across therapists, time, and situations. Furthermore, most investigators have focused on rumination in isolation, ignoring the effects of their treatment on the adaptive behaviors of the patients. Some mentioned the development of collateral behaviors but these were based on clinical impressions rather than on independent behavioral assessment. It is appreciated that the problems of conducting treatment research in clinical settings with elegant research designs can be momentous; nevertheless, a few studies were reviewed which have been noteworthy in this respect and these should serve as models for future research. ACKNOWLEDGMENTS The author gratefully acknowledges the contribution of Dr.Ivan L. Beale to his thinking and for the constructive feedback in the preparation of this article. Special thanks to Professor N. R. Ellis for his critical reading of an approximation to this article and his many helpful suggestions. Appreciation is also extended to Laurie Hinchcliff who undertook the bulk of the literature research, and to Heather King, Karen Page, and Judy Singh for their assistance in the preparation of the manuscript.

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Epstein, L. H., Doke, L. A,, Sajwaj, T. E., Sorrell, S . , & Rimmer, B. Generality and side effects of overcorrection. Journal of Applied Behavior Analysis, 1974, 7, 385-390. Eysenck, H. L. Learning theory and behaviour therapy. Journal of Mental Science, 1959, 105, 61-75.

Forfar, J. O.,& Arneil, G. C. (Eds.), Textbook of pediatrics. London: Churchill, 1973. Foxx, R. M., & Auin, N. H. Restitution: A method of eliminating aggressive-disruptive behaviours of retarded and brain damaged patients. Behaviour Research and Therapy, 1972, 10, 15-27. Foxx, R. M., & Auin, N. H. The elimination of autistic self-stimulatory behavior by overcorrection. Journal of Applied Behavior Analysis, 1973, 6 , 1-14. Foxx, R. M., Snyder, M. S., & Schroeder. F. A food satiation and oral hygiene punishment program to suppress chronic rumination by retarded persons. Journal of Aurism and Developmental Disorders, 1979, 9, 399-412. Frankel, F., & Simmons, J. Q. Self-injurious behavior in schizophrenic and mentally retarded children. American Journal of Mental Deficiency, 1976, 80, 5 12-522. Freeman, B. J., Graham,V.,& Ritvo, E. R. Reduction of self-destructive behaviour by overcorrection. Psychological Reports, 1975, 37, 446. Fullerton, D. T. Infantile rumination. Archives of General Psychiatry, 1963, 9, 593-600. Gaddini, R. D. B., & Gaddini, E. Rumination in infancy. In L. Jessner & E. Pavenstadt (Eds.), Dynamic psychopathology in childhood. New York Grune & Stratton, 1959. Galbraith, D. A,, Byrick, R. J., & Rutledge. J. T. An aversive conditioning approach to the inhibition of chronic vomiting. Canadian Psychiatric Associarion Journal, 1970, IS,31 1-313. Hammond, W . A. Merycism. Journal of Nervous and Menral Diseases, 1894. 21, 680-681. Haynes, S. N. Principles of behavioral assessment. New York Gardner, 1978. Herbst, J., Friedland, G . W.,& Zboralske, F. F. Hiatal hernia and rumination in infants and children. Journal of Pediatrics, 1971, 78, 261-265. Hollowell, J. G., & Gardner, L. 1. Rumination and growth failure in male fraternal twin: Association with disturbed family environment. Pediatrics, 1965, 36, 565-571. Hopper, H. E., & Pinneau, S. R. Frequency of regurgitation in infancy as related to the amount of stimulation received from the mother. Child Development, 1957, 28, 229-235. Hoyt, C. S., & Stickler, G. B. A study of 44 children with the syndrome of recurrent vomiting. Pediatrics, 1960, 25, 775-779. Jackson, G. M., Johnson, C. R., Ackron, G. S . , & Crowley, R. Food satiation as a procedure to decelerate vomiting. American Journal of Mental Deficiency, 1975, 80, 223-227. Johnston, J. M. Punishment of human behavior. American Psychologisf, 1972, 27, 1033-1054. Kanner, L. Historical notes on rumination in man. Medical Life, 1936, 43, 27-60. Kanner, L. Child psychiatry. Springfield: 111.: Thomas, 1957. Kazdin, A. E. Response cost: The removal of conditioned reinforcers for therapeutic change. Behavior Therapy, 1972.3, 533-546. Kazdin, A. E. Behavior modification in applied settings. Homewood, Ill.: Dorsey, 1975. (a) Kazdin, A. E. Characteristics and trends in applied behaviour analysis. Journal of Applied Behavior Analysis, 1975, 8, 332. (b) Kazdin, A. E. Therapy outcome questions requiring control of credibility and treatment-generated expectancies. Behavior Therapy, 1979, 10, 81-93. Kazdin, A. E., & Hartmann, D. P. The simultaneous-treatment design. Behavior Therapy, 1978.9, 912-922.

Kohlenberg, R. J. The punishment of persistent vomiting: A case study. Journal ofApplied Behavior Analysis, 1970.3, 241-245. Lang, P. J., & Melamed, B. G. Avoidance conditioning therapy of an infant with chronic ruminative vomiting. Journal of Abnormal Psychology, 1969. 74, 1-8.

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Lazarus, A. A., & Davison, G. C. Clinical innovations in research and practice. In A. E. Bergin & S. L. Garfield (Eds.), Handbook ofpsychotherapy and behavior change. New York: Wiley, 1971. Leitenberg, H. The use of single-case methodology in psychotherapy research. Journal of Abnormal Psychology, 1973, 83, 87-101. Libby, D. G., & Phillips, E. Eliminating rumination behaviour in a profoundly retarded adolescent: An exploratory study. Mental Retardation, 1978, 16, 57. Linscheid, T. R., & Cunningham, C. E. A controlled demonstration of the effectiveness of electric shock in the elimination of chronic infant rumination. Journal of Applied Behavior Analysis, 1977, 10, 500. Lourie, R. S. Experience with therapy of psychosomatic problems in infants. In P. Hoch & J. Zubin (Eds.), Psychopathology of children. New York Grune & Stratton, 1955. Lovaas, 0. I., Frietag, G., Gold, V. J., & Kassorla, I. C. Experimental studies in childhood schizophrenia: Analysis of self-destructive behaviour. Journal of Experimental Child PsycholOgy, 1965, 2, 67-84. Lovaas, 0 . I., & Simmons, J. Q. Manipulation of self-destruction in three retarded children. Journal of Applied Behavior Analysis, 1969.2, 143-157. Luckey, R. E., Watson, C. M., & Musick, J. K. Aversive conditioning as a means of inhibiting vomiting and rumination. American Journal of Mental Deficiency, 1968, 73, 139-142. Maas, H. Zur casuistic der rumination beim saeugling. Medical Klinik. 1907, 3, 926. Mayhew, G. L., & Harris, F. C. Some negative side effects of a punishment procedure for stereotyped behaviour. Journal of Behavior Therapy and Experimental Psychiatry, 1978, 9, 245-251.

Menking, M.,Wagnitz, J. G., Burton, J. J., Coddington, R. D., & Sotos, J. F. Rumination-Nearfatal psychiatric disease of infancy. The New England Journal of Medicine, 1969, 280, 802804.

Mulick, J. A . , Schroeder, S. R., & Rojahn, J. Chronic ruminative vomiting: A comparison of our treatment procedures. Journal of Autism and Developmental Disorders, 1980, 10, 203-21 3. Murphy, G. Overcorrection: A critique. JournalofMentalDejciencyResearch, 1978.22, 161-173. Murray, M. E., Keele, D. K., & McCarver, J. W. Behavioural treatment of ruminations: A case study. Clinical Pediatrics, 1976, 15, 591-596. Murray, M. E., Keele, D. K., & McCarver, 1. W. Treatment of ruminations with behavioral techniques: A case study. Behavior Therapy, 1977, 8, 999-1003. Ollendick, T. H., & Matson, J. L. Overcorrection: An overview. Behavior Therapy. 1978, 9, 830-842.

Ollendick, T. H., Matson, J. L., & Martin, J. E. Effectiveness of hand overcorrection for topographically similar and dissimilar self-stimulatory behaviours. Journal of Experimental Child Psychology. 1978.25, 396-403. O’Neil, P. M., White, J. L., King, C. R., & Carek, D. J. Controlling childhood rumination through differential reinforcement of other behaviour. Behaviour Modification. 1979, 3, 355-372. Pinneau, S. R. A critique on the articles by Margaret Ribble. Child Development. 1950, 21, 203-228.

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Index

A

motor development in, 108-1 1 I neuropathology of, 108 perceptual-motor functions, slowness and, I 1 1-1 I5 practical considerations, 132- 133

Attention, central executive function and, mild mental retardation and. 93-94

B Behavioral intervention, rumination and, 155174

E Eye-hand coordination, importance in Down’s syndrome, 129-131

C Cognitive influences, mild mental retardation and background, 88 methological factors, 88-90 processing differences: specific or general?, 90-93

I Intellectually handicapped, see also Mental retardation visual fixation in, 1 I - 15 visual scanning in match-to-sample situations, 15-18 visual scanning in visual search and other task situations, 18-24

D Development changes in visual scanning and, 5-8 motor, Down’s syndrome and, 108-1 I I Developmental theory, scanning and, 8-1 1 Down’s syndrome evaluation and conclusions, I3 1 feedback systems in motor skills, 120-121 lability of proprioceptive information system. 126-129 proprioception as feedback system, 122126 vision as feedback system, 121-122 importance of eye-hand coordination in, 129-131 intermodality and sensory-motor integration in, 115-117 components of motor-expressive difficulties, 117-1 18 proprioception, 118-120

M Mental retardation choice reaction time and background: correlational and comparative studies of the role of motor factors, 76-77 conclusions, 8 1 discrimination factors, 78-8 1 varying choice, 77-78 cognitive influences and, 88-93 index of processing speed background, 8 1-83 conceptual factors, 86-88 discrimination reaction time, 85-86 inspection time, 84-85 recent application of backward masking process, 83 183

184

Index

prevalence of rumination in, 140- 141 reaction time in memory scanning and, 7275 simple reaction time and absolute differences, 66-67 coincident changes in heart rate, 71 conclusions, 7 1-72 serial reaction time, 69-70 stimulus intensity, 68-69 temporal factors, 67-68 studies of timed performances attention and central executive function, 93-94 background, 62-63 cognitive influences, 88-93 information processing approach, 63-66 suggested directions for future research, 94-97 Mentally retarded children, visual pattern detection and recognition memory in assessment in infant, 33-41 assessment in profoundly retarded child, 42-54 ’ Motor-expressive difficulties, in Down’s syndrome, 117-1 18 Motor skills, feedback systems in, Down’s syndrome and, 118-129

N Neuropathology, of Down’s syndrome, 108

P Perceptual-motor functions, Down’s syndrome and, 111-115 Processing speed, index of, mild mental retardation and, 81-88 Proprioception in Down’s syndrome, 118-120 as feedback system, 122-126 lability of system, 126-129 Psychodynamic intervention, rumination and, 149-155 Psychopharmacology, rumination and, 148I49 Psychotherapeutic intervention, rumination and, 149- 155

R Reaction time choice, mild mental retardation and, 76-81 in memory scanning, mild mental retardation and, 72-75 simple, mild mental retardation and, 66-72 Rumination differential diagnosis of, 141-144 intervention studies behavioral, 155-174 psychodynamic and psychotherapeutic, 149- I55 psychopharmacological, 148- 149 surgical, 149 prevalence in mentally retarded, 140-141 theories of etiology, 144-148 vomiting and, 144

S Surgery, rumination and, 149

V Vision, as feedback system, in Down’s syndrome, 121-122 Visual fixation, in intellectually handicapped, 11-15 Visual pattern detection and recognition memory assessment in infant operational definitions, 33-35 pattern detection, 35-38 pattern recognition, 38-41 assessment in profoundly retarded child pattern detection, 42-48 recognition memory, 48-54 in children with profound mental retardation objectives of article, 3 1-32 population characteristics, 32-33 summary and discussion, 54-57 Visual scanning developmental changes in, 5-8 developmental theory and, 8- 1 1 in intellectually handicapped match-to-sample situations, 15-18 visual search and other task situations, 18-24 Vomiting, ruminative vomiting and, 144