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Developmental parameters of functional asymmetries and cerebral dominance in children

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Developmental parameters of functional asymmetries and cerebral dominance in children
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Suarez, Lenay Barron, 1948-
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English
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xii, 82 leaves : ill. ; 28 cm.

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Subjects / Keywords:
Asymmetry ( jstor )
Ears ( jstor )
Handedness ( jstor )
Hemispheres ( jstor )
High socioeconomic status ( jstor )
Low socioeconomic status ( jstor )
Socioeconomic status ( jstor )
Standard deviation ( jstor )
Syntax ( jstor )
Vocabulary ( jstor )
Cerebral dominance ( lcsh )
Clinical Psychology thesis Ph. D ( lcsh )
Dissertations, Academic -- Clinical Psychology -- UF ( lcsh )
Psychophysiology ( lcsh )
Hillsborough County ( local )
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bibliography ( marcgt )
non-fiction ( marcgt )

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Thesis:
Thesis (Ph. D.)--University of Florida, 1981.
Bibliography:
Bibliography: leaves 77-80.
General Note:
Typescript.
General Note:
Vita.
Statement of Responsibility:
by Lenay Barron Suarez.

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DEVELOPMENTAL PARAMETERS OF FUNCTIONAL ASYMMETRIES
AND CEREBRAL DOMINANCE IN CHILDREN






By

LENAY BARRON SUAREZ


A DISSERTATION PRESENTED TO THE GRADUATE COUNCIL
OF THE UNIVERSITY OF FLORIDA IN
PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF DOCTOR OF PHILOSOPHY


UNIVERSITY OF FLORIDA


1981

































To Ray With Love















ACKNOWLEDGEMENTS


I would like to express my appreciation to Dr. Jacquelin Goldman

for her invaluable assistance in the preparation of this manuscript and for her professional assistance, encouragement and support throughout. Dr. Eileen Fennell is due a special note of thanks for her careful reading of this dissertation and her helpful constructive criticism, particularly with regard to the review of the literature and the interpretation of the data. I also gratefully acknowledge Drs. Randy Carter, Jack Fletcher, and Paul Spector for their advice and counsel on the analysis of these data and for their patience in assisting me in the interpretation of computer statistics. In addition, I would like to express my gratitude to Drs. Jim Johnson and Larry Siegel for their careful reading of the manuscript and comments.

This project could not have been undertaken without the cooperation of the administration, faculty, and most especially the children of the Hillsborough County, Florida, public and private schools who were facilitative and kind in assisting my efforts in the collection of data.

I thank my cousin, Tony Sanchez, Jr., and good friends, Beth and Bob Ripple, who have provided me with a home-away-from-home and a comfortable environment in which I could complete the writing of this text. Additional thanks go to Beth, who patiently read, re-read, and corrected every page of this dissertation with me.










My thanks go to Sharon Fink and Donna Willey, who typed and retyped the manuscript without complaint.

I am appreciative to my parents who have always supported me in the pursuit of academic excellence. Finally, I thank my husband, Ray, for his understanding, caring, and support.















TABLE OF CONTENTS


CHAPTER


ACKNOWLEDGEMENTS ......................................

LIST OF TABLES ........................................

LIST OF FIGURES .......................................

ABSTRACT ..............................................

INTRODUCTION ..........................................

REVIEW OF THE LITERATURE ..............................

Dichotic Listening ...............................

Scholes Syntax Test and Peabody Picture
Vocabulary Test ...............................

Block Design .....................................

METHOD ................................................


Subjects.


Dependent Procedure Statistic, RESULTS .......

Multivari Univariat


....................................e...

Variables ..............................

...Anlysese............................

al Analyses .............................

..Anales...............................
ate Analysis ............................

e Analyses ..............................


Correlations .....................................


iii

vii

ix xi

1 3 3

II 12 15 15 15 18 19 20 20 21 61


DISCUSSION ...................

Dependent Variables .....


ONE

TWO







THREE


FOUR


FIVE


PAGE


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

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










Correlations ..................................... 70

Summary of Results ............................... 70

Conclusions ...................................... 71

APPENDIX .............................................. 73

BIBLIOGRAPHY .......................................... 77

BIOGRAPHICAL SKETCH ................................... 81















LIST OF TABLES


Table


Page


1. A Schematic Representation of the Subject Design. 2. Table of Significant Main Effects and Significant
Interactions For Independent Variables and Dependent
Variables.
3. Mean Right and Left Channel Total Recall Scores and
Standard Deviations as a Function of Age and SES.

4. Means and Standard Deviations for the Block Design Raw


Scores as 5. Means and Scores as 6. Means and Scores as 7. Means and Scores as 8. Means and
Scores as 9. Means and
Scores as 10. Means and
Scores as


a Function of Age and Sex. Standard Deviations for the Block a Function of Age and SES. Standard Deviations for the Block a Function of Sex and Handedness. Standard Deviations for the Block a Function of Sex and SES. Standard Deviations for the Block a Function of Age, Sex, and Hande Standard Deviations for the Block a Function of Age, Sex, and SES.


Design Raw Design Raw Design Raw Design Raw dness. Design Raw


Standard Deviations for the Block Design Raw a Function of Age, Handedness, and SES.


11. Means and Standard Deviations for the Peabody Picture
Vocabulary Test as a Function of Sex and SES.

12. Means and Standard Deviations for the Peabody Picture
Vocabulary Test as a Function of Age, Sex, and Handedness.

13. Means and Standard Deviations for the Peabody Picture
Vocabulary Test as a Function of Age, Sex, and SES.








Page

14. Means and Standard Deviations for the Peabody Picture 51
Vocabulary Test as a Function of Age, Handedness, and
SES.

15. Means and Standard Deviations for the Scholes Syntax 56
Test as a Function of Age and SES.

16. Means and Standard Deviations for the Scholes Syntax 58
Test as a Function of Sex and Handedness.
17. Means and Standard Deviations for the Scholes Syntax 60
Test as a Function of Age, Handedness, and SES.

18. Table of Correlation Coefficients. 62


viii















LIST OF FIGURES


Figure

1. Mean Right and Left Channel Total Scores as a Function of Age and SES.


Block Design Mean Raw Scores as Sex.

Block Design Mean Raw Scores as SES.

Block Design Mean Raw Scores as Handedness.

Block Design Mean Raw Scores as SES.

Block Design Mean Raw Scores as and Handedness.

Block Design Mean Raw Scores as and SES.

Block Design Mean Raw Scores as Handedness, and SES.

Peabody Picture Vocabulary Test Function of Sex and SES.


a Function of Age and a Function of Age and a Function of Sex and a Function of Sex and a Function of Age, Sex, a Function of Age, Sex, a Function of Age, Mean Raw Scores as a


Peabody Picture Vocabulary Test Mean Raw Scores as a Function of Age, Sex, and Handedness.

Peabody Picture Vocabulary Test Mean Raw Scores as a Function of Age, Sex, and SES.

Peabody Picture Vocabulary Test Mean Raw Scores as a Function of Age, Handedness, and SES.

Scholes Syntax Test Mean Number of Correct Responses as a Function of Age and SES.

Scholes Syntax Test Mean Number of Correct Responses as a Function of Sex and Handedness.


Page


25








Page

15. Scholes Syntax Test Mean Number of Correct Responses 59
as a Function of Age, Handedness, and SES.

16. Example of Pictures Presented as Stimuli in Scholes 80
Syntax Test.















Abstract of Dissertation Presented to the Graduate Council of the University of Florida in Partial Fulfillment of the
Requirements for the Degree of Doctor of Philosophy


DEVELOPMENTAL PARAMETERS OF FUNCTIONAL ASYMMETRIES

AND CEREBRAL DOMINANCE IN CHILDREN

By

Lenay Barron Suarez

December 1981


Chairman: Dr. Jacquelin R. Goldman, Professor Major Department: Clinical Psychology

This study investigated developmental parameters of functional asymmetries and cerebral dominance through examination of children's performances on four tasks as a function of the independent variables of age (5, 8, and 12 years), sex (male and female), handedness (right and left), and socioeconomic status (high and low SES). A dichotic listening task which involved 30 trials of 3 digits simultaneously presented to each ear at the rate of 2 pairs/second was employed as a measure of ear asymmetry. The Block Design Subtests of the Wechsler Preschool and Primary Scale of Intelligence (WPPSI) and Wechsler Intelligence Scale for Children-Revised (WISC-R) were utilized as measures of visuo-spatial competency. Form B of the Peabody Picture Vocabulary Test (PPVT) and the Scholes Syntax Test were used, respectively, as measures of semantic language ability and syntactic language proficiency.









Subjects were 192 children who were chosen from the Hillsborough County, Florida, public and private school systems. They were equally divided according to age, sex, handedness, and SES such that the smallest experimental cell was comprised of 8 subjects. Statistical analyses included a multivariate analysis of variance (MANOVA), analyses of variance (ANOVA), and post hoc tests of comparison between means.

Males and females performed essentially the same on Dichotic Listening, Block Design, Peabody Picture Vocabulary Test, and Scholes Syntax Tests. Likewise, there was no significant difference between the overall performance of right- and left-handers on these tasks. Age proved to be a significant main effect as demonstrated by the fact that the mean number of correct responses for all tasks increased as a function of age. A significant ear asymmetry was found at all ages, a finding which supports the hypothesis that the left hemisphere is, to some extent, specialized for speech functions relatively early in its maturational development. Significant social class differences were found; high SES children were superior in performance to low SES children on all dependent measures. Significant main effects and interactions in relation to hemispheric specialization were discussed.















CHAPTER ONE

INTRODUCTION


Human brain laterality can be operationally defined as the hemispheric specialization of man's higher integrative functions, vastly significant among which are his language and visuo-spatial integrative skills. Teuber (1962) has described differential hemispheric functions in such a manner that, particularly for dextral subjects, the left side of the brain is thought to control speech and language functions while the right hemisphere is believed to control visuo-spatial and constructional skills. Lenneberg (1967) postulated that "cerebral dominance" is, in fact, assessed in terms of the asymmetrical specialization of language and non-language skills within the left and right hemispheres, respectively.

The purpose of this study was to developmentally examine cerebral dominance and hemispheric specialization by observing and comparing the performances of children of different ages, sexes, socioeconomic classes, and handedness groups on tests of ear asymmetry, of semantic and syntactic language skills, and of visuo-spatial expertise. A dichotic listening test of ear asymmetry was utilized as an indirect measure of cerebral dominance for language. The Scholes Syntax Test and Peabody Picture Vocabulary Test were employed, respectively, as measures of syntactic and semantic facility with the English language; they represent abilities generally subserved by the left cerebral






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hemisphere. The Block Design subtests of the Wechsler Preschool and Primary Scale of Intelligence (WPPSI) and the Wechsler Intelligence Scale for Children--Revised (WISC-R) were used as measures of visuospatial integrative function which is an ability subserved by the right cerebral hemisphere. Each of the aforementioned tests in relation to cerebral dominance will be discussed separately.














CHAPTER TWO
REVIEW OF THE LITERATURE


Dichotic Listening
The dichotic listening technique, originally introduced by Broadbent (1954), is an excellent measure of the ear asymmetry phenomenon. That is, it provides a direct assessment of right or left ear superiority in processing linguistic and non-linguistic information. In addition, this technique has been extensively utilized in the study of the asymmetrical specialization of the human cerebral hemispheres. It is regarded by numerous researchers as a reliable behavioral indicator of hemispheric dominance for verbal and non-verbal materials (Richardson and Knights, 1970).
The dichotic listening paradigm can be operationally defined as

the simultaneous and rapid presentation of disparate pairs of materials (spoken words, digits, nonsense syllables, or musical rhythms) to a subject's ears through stereophonic headphones. After an arbitrary number of paired presentations, the subject is asked to report as many of the stimuli as he can remember. It has been consistently found that adult subjects demonstrate superior recall for verbal stimuli presented to the right ear rather than the left ear after dichotic stimulation (Dirks, 1964; Bryden, 1967). The maintenance of the relative stability of an ear asymmetry favoring the right ear has been demonstrated for digits (Broadbent and Gregory, 1964; Bryden, 1963; Kimura, 1961a, 1961b;










and Satz, Achenbach, Pattishall, and Fennell, 1965), nonsense syllables (Kimura, 1967), and word sequences (Bartz, Satz, Fennell, and Lally, 1967). Conversely, when non-verbal stimuli are presented dichotically, adult subjects exhibit superior recall for materials presented to the left ear as compared to the right ear (Curry, 1967).

Essentially, it has been postulated, particularly for dextral subjects, that speech and language functions are predominately specialized in the left cerebral hemisphere and that non-language skills are represented in the right hemisphere. An explanation of the neural structure underlying this functional asymmetry has been suggested by Kimura (1967). She hypothesized that the superior recall of verbal stimuli presented to the right ear is a direct function of more efficient connections between that ear and the speech areas in the left temporal lobe. This asymmetry can be structurally defined (a) at the cortical level, through the lateralization or dominance of speech and language, and (b) at the subcortical level, through more efficient or more numerous neural pathways between each hemisphere and its contralateral ear and less efficient pathways between each hemisphere and its ipsilateral ear. Therefore, ipsilateral inputs to the speech processor are believed to be occluded by contralateral inputs. At the subhuman level, Rosenzweig (1951) has provided physiological evidence for stronger contralateral ear-cortex connections in his studies with cats.

An association between handedness and speech dominance has been

demonstrated by Milner, Branch, and Rasmussen (1964). They found that left-handers are somewhat less likely to exhibit left-hemisphere dominance for speech as compared to right-handers. Since the dichotic










listening procedure has come to be regarded, at least for experimental purposes, as a procedure which reflects the relative superiority or dominance of one cerebral hemisphere (usually the left) in the processing of meaningful language, it logically follows that a similar relationship should exist between handedness and ear asymmetry as measured by performance on dichotic listening tasks. It has been consistently reported that dextrals generally are right ear dominant for the dichotic presentation of meaningful verbal stimuli, such as words or digits, while sinistrals appear to be divided such that the majority are right ear dominant but a small percentage exhibit a left ear superiority for recall of dichotically presented verbal materials (Curry, 1967; Bryden, 1965; Satz, Achenbach, and Fennell, 1967; Satz et al., 1965; and Zurif and Bryden, 1969). Non-familial left-handers are more likely to be right ear dominant than are familial left-handers (Zurif and Bryden, 1969). Such data could lead to the conclusion that nonfamilial left-handers are more likely to have left hemisphere speech representation than are familial left-handers who might be more disposed to have right hemisphere speech representation or bilateral speech representation.

Since performance on dichotic listening tasks can be utilized as

a behavioral index of speech lateralization, studies involving children at various age levels are valuable in contributing to the knowledge of developmental ear asymmetry and developmental speech lateralization. Such developmental dichotic listening studies have become a focal point of research interest in the past few years. However, there is a dearth of information as compared to the data which have been amassed on adult










populations. Among the studies which have been conducted in the area of developmental ear asymmetry, there are many discrepant findings reported. Age, sex, handedness, and socioeconomic status have been found to differentially affect ear asymmetry. A review of the pertinent literature for each of these variables follows.


Age

There is an enormous amount of inconsistency and discrepancy among those studies which have examined the relationship of age to ear asymmetry. Kimura (1963) demonstrated a right ear superiority in children as early as age 4. She utilized a sample of 120 right-handed children ranging in age from 4 to 9 and presented them with 1, 2, and 3 pairs of digits. She found that the greatest asymmetry occurred in her youngest children and decreased with age. Knox and Kimura's (1970) findings with children aged 5 through 9 years were consistent with Kimura's (1963) data--the youngest children exhibited the most ear asymmetry on dichotic listening tasks and this asymmetry seemed to decrease with age. Nagafuchi (1970) demonstrated a significant difference in ear superiority in favor of the right ear in children as young as 3 years of age and also found this asymmetry to be inversely related to age.

An inverse relationship between ear asymmetry and age might lead one to conclude that the process of hemispheric polarization decreases with age. This conclusion is certainly at variance with the research of Lenneberg (1967) who has postulated that the maturational process within the child is positively correlated with the differentiation and lateralization of linguistic functions in the brain. He has proposed










that by the time that language makes its appearance in the child, at around age 2, about 60 per cent of the adult values of maturation of the neurophysiological parameters of the brain are attained. This rapid maturation rate slows down and approaches an asymptote at about the same time that damage to the dominant (left) hemisphere begins to have permanent consequences. Differentiation and lateralization of language functions in the brain are highly correlated with this maturational process. Thus, during the first 10 years of life, speech and language representation evolves from a state of diffuse, bilateral representation to one of increased differentiation and lateralization within the left hemisphere. Lateralization is well established and irreversible when the maturational process has reached an advanced state, presumably at about the time of the onset of puberty. Zangwill (1960) has also suggested that the cerebral lateralization of speech is established gradually during the maturation and development of the child.

However, upon closer examination of the Kimura (1963), Knox and

Kimura (1970), and Nagafuchi (1970) studies, one procedural difficulty which could have contaminated their data must be noted. These studies employed a stimulus tape of great simplicity which could have enabled the older children to report nearly all of the stimuli presented to them, thereby decreasing the magnitude of the difference in recall of stimuli from the right and left ear channels. These authors' implication of an inverse relationship between ear asymmetry and age can be attributed to the fact that their older subjects reached a "ceiling" in responding, and this ceiling effect obliterated the ear asymmetry phenomenon.










However, while the ceiling effect can be utilized to explain the
contamination of the developmental parameters of ear asymmetry in these studies, it cannot account for the existence of ear asymmetry in children as young as 3, 4, and 5 years. Geffner and Hochberg (1971), Berlin, Hughes, Lowe-Bell, and Berlin (1973), and Borowy and Goebel (1976) have demonstrated an ear asymmetry in children of age 5. Most recently, Hiscock and Kinsbourne (1980) and Peck and Goodglass (1980) found the presence of a right-ear superiority on a dichotic listening task with children as early as age 3 as did Ingram (1975) several years earlier. These data suggest that the left hemisphere is, to some extent, specialized for speech functions very early in its maturational development.

In contrast to the preceding studies which provide evidence of ear asymmetry in young children, Bryden (1973) demonstrated a later onset and more gradual development of ear asymmetry with trends toward ear asymmetry at age 10 and a significant right ear superiority at ages 12 and 14. Similarly, a study by Darby (1974) found a significant ear by age interaction in normal children at age 12. Satz, Bakker, Teunissen, Goebel, and Van der Vlugt (1975) found that a trend for right ear superiority was apparent at 5 to 6 years of age, but the difference in recall between ear channels was not significant until the age of 9 years. The amount of ear asymmetry increased positively as a function of age. These examiners concluded that age is an extremely important variable, with the quality of performance generally increasing with age for both ears. As for the ear variable, they concluded that the right ear performs significantly better than the left ear only at later ages although a trend is set up around ages 5 or 6 (Satz et al., 1975).










Sex

There are some conflicting results with regard to the question of whether or not males and females have differential development of ear asymmetry. Nagafuchi (1970) found that, at 3 years of age, females are superior to males with regard to the development of ear asymmetry, but no differences were found between males and females in the older age groups. Bryden (1970) studied children in grades 2, 4, and 6 and found major sex differences with the pattern of ear superiority emerging at grade 4 in girls but not until grade 6 for boys. In a 1963 study, Kimura found no sex differences in the development of ear asymmetry, but in a 1967 study in which she tested children of a lower socioeconomic class, she found that 5-year-old boys did not exhibit a right ear superiority while their female counterparts did show a significant right ear effect.

Knox and Kimura (1970), Geffner and Hochberg (1971), Borowy and Goebel (1976), and Berlin et al. (1973) found no sex differences in their repective developmental studies of ear asymmetry. Satz et al. (1975) utilized a multivariate statistical approach in the analysis of their data and computed the proportion of the variance which was accounted for by sex alone to be less than 7 per cent. These researchers have concluded that there are no sex differences associated with developmental changes in ear asymmetry. Ingram (1975) administered dichotic listening tasks to 3, 4, and 5-year-old children and found absolutely no significant difference between sexes. Bryden (1973), on the other hand, tested 120 subjects at ages 6, 7, 10, 12, and 14, and he found a pronounced sex difference in ear asymmetry in favor of the females.






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Although the majority of the studies reviewed report no sex differences in ear asymmetry, there are enough discrepancies in the literature to justify that this variable be further investigated. It, therefore, was analyzed in this study.


Handedness

Bryden (1970) attempted to discern if right- and left-handed children performed differently on dichotic listening tasks. Using a sample of 144 male and female children in the 2nd, 4th, and 6th grades, he found that differences between right- and left-handers emerged gradually and became statistically significant at grade 6 in which the children are approximately 11 to 12 years of age. The percentage of right ear dominance increased with grade level in the right-handers and decreased with grade level in the left-handers. There are some procedural difficulties to be noted in this study. The first difficulty lies in the fact that each subject performed on 2 tasks of only 10 trials each. The second problem which exists is in regard to the fact that Bryden did not control for the socioeconomic class of his subjects in this study. Socioeconomic class has been shown to be a significant variable in developmental studies of ear asymmetry.


Socioeconomic Status
Geffner and Hochberg (1971) found that subjects from middle and higher socioeconomic groups manifested a significant ear asymmetry at 4 years of age while subjects from the lower socioeconomic groups did not demonstrate a significant ear asymmetry until 7 years of age. Borowy and Goebel (1976) found that middle class subjects showed a






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significantly greater degree of asymmetry than their lower class counterparts. They demonstrated an approximate 2-year lag in the attainment of total right ear recall between the middle and lower social classes. The variable of socioeconomic status is definitely one which warrants further research in its relation to ear asymmetry and cerebral lateralization in children.

To summarize and simplify, this study proposed to consider several questions regarding the ear asymmetry phenomenon. They are: (1) At what age does ear asymmetry manifest itself? (2) Does the magnitude of the ear asymmetry increase developmentally with age? (3) Is ear asymmetry independent of sex? (4) Does ear asymmetry manifest itself differently in right- and left-handed children? and (5) Does the ear asymmetry developmentally manifest itself differently in children of higher versus lower socioeconomic status?


Scholes Syntax Test and Peabody Picture Vocabulary Test

These two tests are not commonly utilized as behavioral indices

of cerebral lateralization as is the dichotic listening task, but they are representative of semantic and syntactic linguistic functions which are, for nearly all of the dextral population and for the majority of the sinistral population, subserved and mediated by the left hemisphere. It is expected that semantic and syntactic skills will increase with age in children of a normal population. Other questions which are examined include (1) Do children of low socioeconomic status have inferior scores on these language tasks relative to high socioeconomic status children? (2) Is there any difference between the scores of males and females on these tasks? and (3) Do right- and left-handers perform






-12-


differentially with regard to semantic and syntactic abilities? This last question is of great interest because various experimental data have supported the hypothesis that language may be more diffusely represented in sinistrals than in dextrals at the higher cortical level (Goodglass and Quadfasel, 1954; Zangwill, 1960; Hecaen and Ajuriaguerra, 1964; Subirana, 1969; and Roberts, 1969).


Block Design Test
The right cerebral hemisphere aides in non-linguistic, visualand tactile-spatial processing. While it seems that most studies of cerebral dominance and hemispheric specialization from a developmental perspective have focused on left hemispheric function, the importance of "hemisphere specialization for spatial processing may be critical in human ontogenetic and possibly in phylogenetic development of lateralization of function in general, and it is an important aspect of the neural substrate of cognition" (Witelson, 1976, p. 425).

Yen (1975) compared the paper-and-pencil spatial performance of dextral and sinistral high school students of which 1236 were males and 1241 were females. She found that there were no differences in the performance of right- and left-handed females but that left-handed males on the average performed worse than right-handers on spatial tasks. Miller (1971) reported that the spatial performance of psychology undergraduates was poorer for subjects with mixed-handedness than for those with right-handedness although there was no significant difference between the two groups on verbal performance. Similarly, Levy (1969) selected a subject pool of dextral and sinistral graduate students with matching verbal scores on the Wechsler Adult Intelligence






-13-


Scale (WAIS) and found that the scores of the right-handers were significantly superior to the scores of the left-handers. She postulated a sort of brain symmetry among the sinistrals in which both hemispheres subserve speech. Thus, visuo-spatial functioning in these sinistrals was "down" because the right hemisphere was mediating two functions -- the linguistic as well as the visual- and tactile-spatial. In more recent studies, Levy (1974) and Levy and Nagalaki (1972) proposed that among sinistrals, a percentage of which have less complete or bilateral speech representation, one might expect to observe lowered spatial abilities relative to verbal language skills. The rationale for this conclusion is that in cases of bilateral or incomplete speech lateralization, there should be a disadvantage associated with those spatial functions subserved by the right hemisphere.

McGlone and Davidson (1973) found a non-significant trend for right-handed males and females to perform superiorly as compared to their left-handed counterparts on the WAIS Block Design subtest and on an altered version of the Primary Mental Abilities Spatial Relations.

In contrast, there are those investigators whose studies report no handedness effect on spatial performance. Newcombe and Ratcliff (1973) found that right-, mixed-, and left-handed adults performed equivalently on the verbal and performance subtests of the WAIS. They found no significant differences between sexes either. Likewise, Annett and Turner (1974) tested elementary school students on Draw-A-Man maze, and vocabulary tests and found no significant handedness or sex effects. Fennell, Satz, Van der Abell, Bowers,and Thomas (1978) failed to provide evidence for a spatial defect in normal left-handed adults.






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Witelson (1976) studied specialization of the right hemisphere for spatial processing in 200 normal males and females between 6 and 13 years of age. She found that for boys as young as 6 years, the right hemisphere is specialized for spatial processing, but that for girls, spatial processing appears to be a bilateral function until puberty. She postulated a greater plasticity in the developing female brain which is associated with fewer language disorders than are found among boys.

This study utilized comparison of scores on the Block Design subtest of the Wechsler Preschool and Primary Scale of Intelligence (WPPSI) for the 5-year-olds and the Wechsler Intelligence Scale for Children -- Revised (WISC-R) Block Design subtest for the 8 and 12year-olds to investigate the following questions in addition to expected increased performance scores as a function of age:(1) Do right- and left-handers perform differently on this test of visuo-spatial skill?

(2) Do males and females perform differently? (3) Does socioeconomic class differentially affect the development of visuo-spatial integrative skills in children?














CHAPTER THREE

METHOD

Subjects

The 192 subjects (Ss) who participated in this study were obtained from both public and private schools in Hillsborough County, Florida. All were Caucasian and of normal intelligence. They were assigned to 24 experimental cells according to the independent variables of Age (5, 8, and 12 years), Sex, Handedness, and Socioeconomic Status (SES) such that each cell was composed of 8 Ss. A graphic representation of the experimental design is shown in Table 1.

Handedness was determined by (a) verbal report of the S, (b) by preferred hand on the manual tasks of writing, drawing, throwing a ball, cutting with scissors, and kicking, and (c) by performance on a rotor pursuit task consisting of four 20-second trials with each hand; mean performance was calculated for each hand. Subjects were assigned to high or low SES groups based on teacher evaluations and according to classification by Hollingshead's (1957) Two Factor Index of Social Position involving weighted scores for occupational and educational factors. All Ss were administered a hearing test to insure that their hearing was within normal range.


Dependent Variables

The dependent variables included a Dichotic Listening (DL) test; the Block Design (BD) subtests of the WPPSI (for the 5-year-olds) and








Table 1. A Schematic Representation of the Subject Design


AGE


5 years



Male Female


SEX


SES High Low High Low

AAAA

HANDEDNESS R L R L R L R L NUMBER I I I I I I I Ss PER CELL: 8 8 8 8 8 8 8 8


8 years


12 years


Male Female Male Female


High L w HI h Low High Low High Low

AA A A AAA

R L R L R L R L R L R L R L R L I I III8I I8IIII 8 8 8 8 8 8 8 8 8 8 8 8 8 8 8 8


TOTAL NUMBER Ss: 192






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the WISC-R (for the 8 and 12-year-olds); Form B of the Peabody Picture Vocabulary Test (PPVT); and the Scholes Syntax Test. Dichotic Listening Test

The DL test was utilized as a measure of ear asymmetry. The stimulus tape was composed of 5 practice and 30 experimental trials with 3 pairs of digits comprising each trial. The digits were delivered to the Ss' ears through stereophonic headphones in such a manner that onehalf of each pair of digits was heard in each ear in a zero-delay condition. Each trial was presented at the rate of 2 pairs/second with a 10 second intertrial interval. The digits heard on the tape were 1, 2, 3, 4, 5, 8, 9, 10, 12, 13, 14, 15, and 18. They were recorded so that onset time and loudness were identical in each channel.

In order to minimize the possibility that the digits may be more easily perceived from one channel versus another and to avoid possible introduction of an ear bias, this study employed certain control methods with the aim of equalizing any anomalies in the production of the tapes. The stimulus tape was constructed so that the first 15 experimental trials were identical to the second 15 experimental trials. On each S, the headphones were reversed at Trial 16 such that the digits initially presented to the right ear were now presented to the left ear and vice versa. This constituted a within-subject reversal procedure. A between-subject reversal procedure was implemented by reversing the initial placement of the headphones for every other subject so that one-half the Ss heard Channel A in the right ear first and one-half the Ss heard Channel B in the right ear first. The recall condition was free recall with all responses recorded by this examiner.






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Peabody Picture Vocabulary Test

Form B of the PPVT was utilized in this study as a measure of each S's language facility with word meanings. Thus, it was a measure of semantic competence. Maximum score for each S was 150.


Block Design Subtest

The Block Design subtests of the WPPSI and the WISC-R were utilized as a measure of visuo-spatial ability. Maximum scores were 20 and 62 on the WPPSI and the WISC-R, respectively.


Scholes Syntax Test

The Scholes Syntax Test was included in this study as a measure of syntactic ability and is described in detail in Scholes, Tanis, and Turner (1976) and in Fletcher (1978). This test consists of 33 trials in which the S listens to a taped sentence through headphones and must choose from four line drawings the picture which depicts the appropriate sentence meaning. Maximum score was 30. Please see the Appendix for a detailed description and explanation of this test which was prepared by Fletcher (1978, pp. 70-73).

Procedure

Each child was individually tested by the Examiner (E) in a quiet room in his own school. The hearing test was administered first followed by the manual preference tasks and the rotor pursuit task. In order for a child to participate in this study, he had to exhibit consistent manual preference in verbal report; on the tasks of writing, drawing, throwing a ball, kicking a ball, and cutting with scissors; and inthemean






-19-


performance over 4 trials per hand on the,,rotor pursuit. If any inconsistency was apparent, then the S was eliminated from this study.-:TIhus, all Ss included in this study can be said.-to be "strongly" dextral or "strongly" sinistral.

After an S had passed the hearing screening and showed consistency in hand preference and performance, he then was administered the PPVT, the BD, the Scholes Syntax Test, and the DL test.


Statistical Analyses
Data collected for each of the dependent variables were analyzed by a multivariate analysis of variance (MANOVA). In this type of analysis, the scores on the dependent variables are computed together and, for any significant independent variable,-the weighted contribution of each dependent variable can be readily observed. The MANOVA is extremely sensitive to group differences and is an excellent tool for controlling Type I error rates (Hummel and Sligo, 1971).

Data for each dependent variable were also analyzed by separate analyses of variance (ANOVA); post hoc analyses of pairwise comparison between means included Newman-Keuls Tests and/or the Duncan's New Multiple Range Test.















CHAPTER FOUR

RESULTS


Multivariate Analysis
A multivariate analysis of variance (MANOVA) of the dependent variables, which included Peabody Picture Vocabulary Test (PPVT) raw scores, Block Design (BD) raw scores, Scholes Syntax Test total number correct, and Dichotic Listening (DL) Right + Left Channel Total scores, was computed on the 128 Ss who comprised the 5-year-old and 12-year-old populations. Data from the 8-year-old population were not included in the MANOVA because preliminary analysis indicated that a disproportionate number of this age group were bilingual. Thus, the 8-year-olds were not thought to be a representative sample of the population and were, therefore, excluded from this study.

The Age factor (F=187.05234; df4/l1O; p < .0001) and the SES factor (F=20.05473; df4/llO; p < .0001) were found to be significant independent variables. The main effects of Sex and Handedness were not significant.

Correlation coefficients of .81 for the PPVT, .75 for the BD, .55 for the Scholes, and .44 for R + L Channel Total illustrate the relative association of each of these dependent variables with the Age effect. For the SES effect, the correlation coefficients were .83 for the PPVT, .71 for the BD, .59 for the Scholes, and .39 for the R + L Channel Total. Thus, the significance of these main effects appears to be most related to the Ss' performances on the Peabody and Block Design Tests.

-20-






-21-


The Age X SES interaction was significant (F=7.05592; df=4/110; p < .0001) with correlation coefficients as follows: BD, .95; R + L Total, .46;Scholes, .39; and PPVT, .28. The Sex X Hand effect approached significance (F=2.18102; df4/1l0; p < .0748),and relative association of the dependent variables to this two-way interaction were BD, .80; Scholes, .66; PPVT, .20; and R + L Total, -0.092. The Sex X SES interaction also approached significance (F=2.2224; df=4/ll0; P < .0702), and correlation coefficients were as follows: BD, .91; PPVT, .57; Scholes, .20; and R + L Total, -.07.

The Age X Sex X SES interaction was significant (F=2.5323; df=

4/110; p < .0437) with correlation coefficients of .95 for the BD, .59 for the PPVT, .29 for the Scholes, and .08 for the R + L Total. Correlation coefficients of .68 for the PPVT, .66 for the Scholes, .59 for the BD, and -0.15 for the R + L Total illustrate the relative association of the dependent variables with the Age X Hand X SES interaction (F=

3.5928; df4/ll0; 2 < .0001).

Finally, the Age X Sex X Handedness X SES interaction was significant (F=2.52258; df=4/ll0; p < .0443) with correlation coefficients of .75 for the BD, .00 for the Scholes, -.08 for the PPVT, and -.47 for the R + L Total.


Univariate Analyses

Table 2 delineates all significant main effects of the independent variables of Age, Sex, Handedness, and SES in relation to the dependent variables of Dichotic Listening (DL), Block Design raw scores (BD), Peabody Picture Vocabulary Test (PPVT), and Scholes Syntax Test. Performance relative to each of these dependent variables is discussed separately.






-22-


Table 2. Table of Significant Main Effects and Significant Interactions for Independent Variables and Dependent Variables


DL BDR PPVT SCHOLES AGE * * * * SES * * * * AGE X SEX * AGE X SES * * * SEX X HANDEDNESS * * SEX X SES * * AGE X SEX X HANDEDNESS * * AGE X SEX X SES * * AGE X HANDEDNESS X SES * * * AGE X SEX X HANDEDNESS X SES *






-23-


Dichotic Listening

Analysis of the DL data included a five-way analysis of variance of right channel and left channel recall scores with Age, Sex, Handedness, and SES as between-subjects measures and with Ear as a withinsubject repeated measure; Duncan's New Multiple Range Test was utilized for post hoc pairwise comparison among means. Right channel and left channel total recall scores were analyzed in a four-way analysis of variance with Age, Sex, Handedness, and SES as between-subjects measures; Newman-Keuls analyses were utilized as post hoc tests of pairwise comparison among means.

As was expected, Age was a significant independent variable. A mean R + L channel total recall score of 106.7813 (s.d.=14.00) for the 12-year-old population was significantly better than a mean recall score of 80.7188 (s.d.=9.87) for the 5-year-old population (F=148.37; df=/112; p < .0001). A total R + L channel mean recall of 97.5469 (s.d.=ll.05) for the high SES children was significantly more superior than 89.9531 (s.d.=13.09) for the low SES children (F=12.53; df=I/112; < .0006. The Ear main effect also proved to be significant with a 51.52 (s.d.=13.37) mean right channel recall in contrast to a 42.24 (s.d.=14.08) mean left channel recall (F=18.12; df--/112; P < .0001). A significant ear asymmetry was found at age 5 and it remained essentially unchanged at age 12, thereby accounting for the non-significance of the Age X Ear interaction. The main effects of Sex and Handedness proved to be non-significant. Thus, there was no appreciable difference between the performance of right and left handers or between males and females on the DL task.






-24-


The Age X SES interaction was significant (F=6.19; df=I/112; p < .0143) and is represented in Figure 1; Table 3 lists the mean right and left channel scores and the standard deviations of the 5-year-old high and low SES Ss as well as the 12-year-old high and low SES Ss. While there is no difference between the total channel recall scores of 79.593 and 81.8438 for the low and high SES 5-year-olds, respectively, the mean score of 113.25 for the 12-year-old high SES children is significantly higher than 100.3125 for the 12-year-old low SES children. As would be expected, both SES groups exhibit a significant increase in recall scores from age 5 to age 12.

No other DL interactions proved to be significant, although the

Handedness X Ear and the Handedness X SES X Ear interactions approached significance.


Block Design

Analysis of the BD data included a four-way analysis of variance of raw scores as a function of the main independent variables of Age, Sex, Handedness, and SES and Newman-Keuls analyses of post hoc comparison between means. As in the case of the DL data, Age and SES were significant main effects while Handedness and Sex were non-significant in relation to performance on this visuo-spatial task. The 12-yearold Ss' mean raw score of 33.14 (s.d.=7.55) was significantly better than the 5-year-old Ss' mean raw score of 11.40, (s.d.=3.49), (F= 429.5976; df--/113; p < .0001). A mean score of 25.641 (s.d.=5.57) for the high SES children was significantly better than 18.9065 (s.d.=6.18) which was the mean score of the low SES children (F=41.2441; df=I/113; p< .0001).






-25-


1201F


9---0 High SES 0 Low SES


0/


//


//
/


I,
/
*1


5 Years


12 Years


AGE


Mean Right and Left Channel Total Scores as a Function of Age and SES.


I10k


I00-


90-


801-


70 -


Figure 1.






-26




Table 3. Mean Right + Left Channel Total Recall Scores and
Standard Deviations as a Function of Age and SES


5-year-olds


79.5930 81.8438


12-year-olds


s.d.

10.1680

9.5602


100.3125 113.2500


s.d.

15.4740 12. 3632


LOW SES HIGH SES






-27-


The Age X Sex interaction proved to be significant (F=6.4923; df=

1/113; p < .0122) and is illustrated in Figure 2 with means and standard deviations represented in Table 4. Both sexes improved significantly in visuo-spatial performance from age 5 to age 12. At 5 years of age, there was no appreciable difference between performance of males and females, but at age 12 years, the males' mean score of 35.25 was significantly better than the females' mean score of 31.031.

The Age X SES interaction illustrated in Figure 3 was also significant (F=26.1214; df:/113; p < .0001), and Table 5 contains the means and standard deviations for this interaction. For both high and low SES children, there is a significant increase in BD performance from age 5 to 12 years. Performance of high and low SES children is comparable at age 5, but 12-year-old high SES children with a mean BD score of 39.188 scored significantly higher than their low SES counterparts with a mean score of 27.094.

Table 6 lists the means and standard deviations for the BD raw scores as a function of Sex and Handedness, which proved to be a significant interaction (F=5.7552; df=I/113; p < .0181). Sinistral males withamean of 24.968 were superior to and significantly better than sinistral females and dextral males with respective mean scores of 20.906 and 21.125. Performance of dextral males and dextral females with respective means of 21.125 and 22.093 was without significant difference, as shown in Figure 4.

The Sex X SES interaction also was significant (F=7.5989; df= 1/113; p < .0068) and is graphically represented in Figure 5. Means and standard deviations are listed in Table 7. Means for high SES males and females were 24.968 and 26.312, respectively;






-28-


50
0---0 Males
S Females


40




W .00
Cr.e

30
0 0 U,


S20
z




10





0
5 Years 12 Years AGE


Block Design Mean Raw Scores as a Function of Age and Sex.


Fi gure 2.







-29




Table 4. Means and Standard Deviations for the Block Design Raw Scores as a Function of Age and Sex


5-year-olds 12-year-olds X s.d. X s.d. MALES 10.843 3.72 35.250 7.24 FEMALES 11.968 3.26 31.031 7.85







-30-


50
A---d High SES O"--O Low SES



40






Uj 30
w/




0
20




z

Z>



10





0

5 Years 12 Years AGE Figure 3. Block Design Mean Raw Scores as a Function of Age and SES.







-31-


Table 5.
for the


Means and Standard Deviations Block Design Raw Scores as a Function of Age and SES


5-year-ol ds


10.719 12.094


s.d.

3.54 3.45


12-year-ol ds


27.094

39.188


s.d.

8.00 7.08


LOW SES HIGH SES






-32




Table 6. Means and Standard Deviations for the Block Design Raw Scores as a Function of Sex and Handedness


Males


DEXTRALS SINISTRALS


21.125 24.968


s.d.

6.19 5.29


22.093 20.906


Females


s.d.

6.80 5.09






-33-


Dextrals Sinistrals


A-""- -- - " ""- -- -- _


Males


Figure 4. Block
ness.


Design Mean Raw Scores as a Function of Sex and Handed-


0cO AW---A


40-


30 -


20 -


-A


10-


Females






-34-


50r


A_--A Males 0--o Females


401


301


20F


10 -


-
A- - - -


Low SES


Block Design Mean Raw Scores as a Function of Sex and SES.


Figure 5.


High SES


- -A






-35


Table 7. Means and Standard Deviations for the Block Design Raw Scores as a Function of Sex and SES Males Females X s.d. X s.d.

LOW SES 21.125 4.81 16.687 7.30 HIGH SES 24.968 6.57 26.312 4.34






-36-


means for low SES males and females were 21.125 and 16.687, respectively. High SES males and females proved to be significantly superior to their low SES counterparts, respectively, on BD performance. Low SES males were significantly better than low SES females, while high SES males and females were not appreciably different from each other in their mean scores.
Means and standard deviations for the significant Age X Sex X

Handedness interaction are shown in Table 8 (F=4.4141; dfl/113; P < .0379). There are no significant differences between 5-year-old dextral and sinistral males and females in their mean performance on the BD as observed in Figure 6. A significant increase in performance is evidenced for all Sex X Handedness groups from age 5 to age 12 years. At 12 years, male sinistrals with a mean score of 38.125 are significantly better than male dextrals with a mean score of 32.375, female dextrals with a mean score of 32.875, and female sinistrals with a mean score of 29.188. Female dextrals demonstrate a significant superiority relative to female sinistrals at age 12 on this task.

The Age X Sex X SES interaction was significant (F=9.33; df=I/113; p < .0028) and is graphically illustrated in Figure 7. Means and standard deviations, listed in Table 9, suggest that there are no differences between Sex X SES groups at age 5 and that a significant increase occurs from age 5 to age 12 years for all Sex X SES groups. Twelveyear-old high SES males and females with respective mean scores of 38.25 and 40.125 are both significantly better on this visuo-spatial task than 12-year-old low SES males and females with mean scores of 32.25 and 22.56, respectively. Also, low SES males performed significantly better than low SES females at age 12 years.






-37-


Table 8. Means and Standard Deviations for the Block Design Raw Scores as a Function of Age, Sex, and Handedness


DEXTRALS SINISTRALS


5-year-olds

Males Fema 1 es

X s.d. X s.d.

9.875 4.22 11.312 3.22 11.812 3.13 12.625 3.29


12-year-olds

Males Females

X s.d. X s.d.

32.375 7.66 32.875 9.06 38.125 6.80 29.188 6.40






-38-


50


40 -


A,---M Mole Sinistrals h- Mole Dextrals
---@ Female Sinistrals 0-6- Female Dextrals


301-


* 0
A
A


201-


10 -


5 Years


12 Years


AGE


Figure 6. Block Design Mean Raw Scores as a Function of Age, Sex, and
Handedness.






-39-


Males, High SES Males, Low SES Females, High SES Females, Low SES


7
/
7
7-


12 Years


AGE


Block Design Mean Raw Scores as a Function of Age, and SES.


Sex,


50


A----A

0----0


40 -


301


20 F


10 v


5 Years


Figure 7.






-40



Table 9. Means and Standard Deviations for the Block Design Raw Scores as a Function of Age, Sex, and SES


5-year-ol ds


Fema l es

X s.d.

11.437 3.21

12.500 3.31


12-year-ol ds

Males Females

X s.d. X s.d.

32.250 5.62 22.560 8.56 38.250 9.81 40.125 5.18


Males


LOW SES HIGH SES


s.d.

3.83 3.59


X

10.000 11.690






-41-


Table 10 illustrates the means and standard deviations for the Age X Handedness X SES interaction which was significant (F=5.0625; df=I/113; p< .0264), and Figure 8 illustrates the graphic representation of this interaction. At age 5 years, there are no significant differences between any of the Handedness X SES groups. At age 12 years, high SES dextrals and sinistrals with respective means of 39.812 and 38.562 performed significantly better than both low SES dextrals and sinistrals with respective means of 25.437 and 28.750. High SES dextrals scored comparably to high SES sinistrals as did low SES dextrals and sinistrals to each other.


Peabody Picture Vocabulary Test (PPVT)

Analysis of the PPVT data included a four-way analysis of variance of the number of correct responses as a function of the independent variables of Age, Sex, Handedness, and SES and Newman-Keuls analyses of post hoc comparison between means. Age was a significant main effect (F=504.0388; df--/113; p < .0001) suggesting that, as would be expected, semantic skills increase with age. There is a significant increase from age 5 with a mean of 54.453 (s.d.=6.26) correct responses to a mean of 93.4219 (s.d.=12.27) correct responses at age 12. The SES main effect is also significant with high SES children producing 80.4995 (s.d.=10.59) mean correct responses as compared to 67.3745 (s.d.=8.81) mean correct responses produced by the low SES children.

The Sex X SES interaction, which was significant (F=2.9873; df= 1/113; P < .0867), is graphically represented in Figure 9. There are no significant differences between males and females of low SES or between males and females of high SES. The high SES males and females,






-42-


Table 10. Means and Standard Deviations
for the Block Design Raw Scores as a Function of Age, Handedness, and SES


5-year-ol ds


High SES

X s.d.


12-year-olds


Low SES


X s.d.


High SES X s.d.


Low SES


X s.d.


DEXTRALS 10.062 3.88 11.125 3.63


39.812 7.47


25.437 9.22


14.125 2.97 10.312 3.43


SINISTRALS


38.562 6.66 28.750 6.55






-43-


50 -


Dextrols, High SES Dextrals, Low SES Sinistrals, High SES Sinistrals, Low SES
p



/
/A
'0



/
//


5 Years


12 Years


AGE


Figure 8. Block Design Mean Raw Scores as a Function of Age, Handedness,
and SES.


0O


401-


30k


20 -


101-






-44-


Males
* Females


105 100

95 90 85

80 75 70

65 60 55 50


UI I I
Low SES High SES

Figure 9. Peabody Picture Vocabulary Test Mean Raw Scores as a
Function of Sex and SES.


.- A


A....--






-45-


with respective means of 79.093 and 81.906, scored significantly higher than low SES males and females, with respective mean scores of 68.968 and 65.781. These means and standard deviations are listed in Table 11. The significance of this interaction is primarily accounted for by differences in the performances of high versus low SES groups as opposed to differences between males and females.

The Age X Sex X Handedness interaction proved to be significant (F=3.57363; df=/113; P < .0613) and is graphed in Figure 10. Means and standard deviations shown in Table 12 demonstrate that the significance of this interaction must be accounted for entirely by age differences since all Sex X Handedness groups increased dramatically from ages 5 to 12 years. No Sex X Hand differences in mean scores are significant within age groups.

Table 13 lists the PPVT means and standard deviations for the Age X Sex X SES interaction which was also significant (F=3.5736; df=/113; p < .0613). Figure 11 illustrates that at age 5 years, high SES males and females with respective means of 59.2500 and 60.1250 are significantly better than low SES males and females with respective means of 48.50 and 49.9375. At age 12, high SES males and females with respective means of 98.9375 and 103.6875 demonstrate significantly better performance than low SES males and females with respective means of 89.4375 and 81.6250. Within the low SES 12-year-old group, males had significantly better scores than females.

The means and standard deviations for the significant Age X Handedness X SES interaction (F=6.8150; df=/113; p < .0103) are shown in Table 14. The graphic representation of the means in Figure 12 displays






-46


Table 11. Means and Standard Deviations
for the Peabody Picture Vocabulary Test as a Function of Sex and SES Males Females Y s.d. X s.d. LOW SES 68.968 10.62 65.781 6.51 HIGH SES 79.093 12.37 81.906 8.44






-47-


105 100

95 90 85


70

65


60 55

50




0


0--- 0 Female, Dextral 0---0 Female, Sinistral
- A----A Mole, Dextral A Male, Sinistrol


5 Years


12 Years


AGE


Figure 10. Peabody Picture Vocabulary Test Mean Raw Scores as a
Function of Age, Sex, and Handedness.






-48




Table 12. Means and Standard Deviations for the Peabody Picture Vocabulary Test as a
Function of Age, Sex, and Handedness


5-year-olds


12-year-ol ds


Males


DEXTRALS SINISTRALS


7

55.5625 52.1875


s.d.

6.91 7.52


Fema I es

s.d.

54.5000 6.07 55.5625 3.94


X

91.43 96.93


Males Fema

s.d. X

375 16.88 94.2500 375 11.95 91.0625


1 es s.d.

9.86 8.82






-49



Table 13. Means and Standard Deviations for the Peabody Picture Vocabulary Test as a
Function of Age, Sex, and SES


5-year-ol ds

Males Females

X s.d. X s.d. 48.5000 9.05 49.9375 5.55 59.2500 4.74 60.1250 4.64


X

89.43 98.93


12-year-olds

Males Females

s.d. X s

375 11.99 81.6250 7 375 16.84 103.6875 11


LOW SES

HIGH SES


.d.

.35 .00






-50-


0----0 Females, High SES 0-----0 Females, Low SES A--A Males, High SES A Males, Low SES


/ / /
"I
//
'I,


"'I
'/7/7


/
/
/
/


/
/
/


105 100


95 90 85


5 Years


AGE


Figure 11.


Peabody Picture Vocabulary Test Mean Raw Scores as a Function of Age, Sex, and SES.


,/ ,A / /


///
/ /
/
/ /
//

// / /
,,/


60 55 50


45


12 Years


f






-51



Table 14. Means and Standard Deviations for the Peabody Picture Vocabulary Test as
Function of Age, Handedness, and SES


5-year-ol ds


Dextrals


12-year-ol ds


Sinistrals


s.d.


s.d.


Dextrals


s.d.


Sinistrals Y s.d.


LOW SES 51.6875 7.27 46.7500 7.73 82.3125 7.82 88.7500 11.69 HIGH SES 58.3750 5.63 61.0000 3.52 103.3750 17.92 99.2500 9.15






-52-


105 100

95 90 85 80 75 70 65

60 55 50 45

0


0--0 Dextrol, High SES
* Dextral, Low SES A---A Sinistral, High SES A Sinistral, Low SES


5 Years


12 Years


AGE


Figure 12. Peabody Picture Vocabulary Test Mean Raw Scores as a
Function of Age, Handedness, and SES.






-53-


that at age 5 years, the high SES dextrals and sinistrals with means of 58.3750 and 61.000, respectively, perform significantly better than the low SES sinistrals with a mean number of correct responses of 46.75, but not better than the low SES dextrals with a mean score of 51.6875. All Handedness X SES groups increased significantly with age. At age 12, low SES dextrals and sinistrals performed comparably with means of 82.3125 and 88.7500; high SES dextrals and sinistrals also performed comparably with means of 103.3750 and 99.2500. High SES 12-year-olds, both dextral and sinistral, scored significantly better than low SES 12-year-olds, both dextral and sinistral.


Scholes Syntax Test
Analysis of the Scholes Syntax Test data included a four-way analysis of variance of the number of correct responses as a function of the independent variables of Age, Sex, Handedness, and SES, and NewmanKeuls analysis of post hoc comparison between means. Consistent with the other dependent variables already discussed, Age was a significant main effect in generating differential performance on the Scholes (F= 233.7163; df=I/113; p < .0001). There was a significant increase in scores from 17.4844 (s.d.=3.08) at age 5 to 25.2656 (s.d.=3.81) at age 12. SES was also a significant main effect (F=28.5318; df=/ll3; p < .0001) with high SES children scoring 22.7344 (s.d.=2.80) which was significantly better than the low SES children's score of 20.0156 (s.d.=4.02). The main effects of Sex and Handedness were non-significant.
Figure 13 is the graphic representation of the Age X SES interaction which proved to be significant (F=4.3576; df=/113; p < .0391).






-54-


A---- High SES 0-----O Low SES


-.




A- -. - -. - -, - - .- - -. - -. -. -. - - -


I0I-


0 L I


5 Years


AGE


Figure 13.


Scholes Syntax Test Mean Number of Correct Responses as a Function of Age and SES.


40 F


30 -


20 -


12 Years






-55-


Table 15 lists the means and standard deviations for this interaction. At age 5 years, high SES children with a mean score of 18.3125 performed significantly better than low SES children with a mean score of 16.6562. A significant increase in number of correct responses was evidenced for both SES groups from age 5 to age 12. At age 12, the high SES children again scored significantly better than the low SES children with respective means of 27.1562 and 23.3750.

The Sex X Handedness interaction was significant and is shown in Figure 14 (F=3.8600; df--/113; p < .0519); means and standard deviations are listed in Table 16. Comparable scores were elicited from sinistral males and sinistral females, from dextral males and dextral females, and from dextral and sinistral females. The only significant difference lies between the sinistral males (x=22.21) and the dextral males (x=20.50).

Finally, the Age X Handedness X SES interaction was significant (F=6.3366; df=I/113; p < .0132) and is graphically presented in Figure 15. At age 5 years, high SES sinistrals with a mean score of 19.6875 are significantly better than low SES sinistrals with a mean score of 16.000. There was no appreciable difference in the scores of the high SES dextrals, the low SES dextrals, or the low SES sinistrals in this age group. A significant increase in scores was evidenced for all SES X Handedness groups from age 5 to age 12 years as is readily seen in Figure 15 and Table 17. At age 12 years, the high SES dextrals and sinistrals had comparable mean scores of 27.0625 and 27.25, respectively; the low SES sinistrals and dextrals also had comparable mean






-56



Table 15. Means and Standard Deviations
for the Scholes Syntax Test as a
Function of Age and SES


5-year-olds


16.6562

18.3125


s.d.

2.75 3.38


12-year-olds


X

23.3750 27.1562


LOW SES HIGH SES


s.d.

4.97 2.07






-57-


0---0


40 30


20-


Sinistral Dextral


A l ---- - - - - - - - -
O


10 -


Males


Figure 14.


Females


Scholes Syntax Test Mean Number of Correct Responses as a Function of Sex and Handedness.






-58



Table 16. Means and Standard Deviations
for the Scholes Syntax Test as a
Function of Sex and Handedness


Males

X s.d. X


DEXTRALS SINISTRALS


20.50 22.21


2.64 4.74


21.25 21.53


Fema 1 es


s.d.

3.50 2.52






-59-


Dextrals, High SES Dextrals, Low SES Sinistrals, High SES Sinistrals, Low SES


401-


301-


20 k


10'


v'J
5 Years 12 Years AGE

Figure 15. Scholes Syntax Test Mean Number of Correct Responses
as a Function of Age, Handedness, and SES.







-60



Table 17. Means and Standard Deviations
for the Scholes Syntax Test as a
Function of Age, Handedness, and SES


5-year-ol ds

Dextrals Sinistrals Y s.d. X s.d.

17.3125 3.13 16.0000 2.31 16.9375 3.71 19.6875 3.00


12-year-ol ds

Dextrals Sinistrals X s.d. X s.d.

22.7500 3.51 24.0000 6.09 27.0625 1.56 27.2500 2.48


LOW SES HIGH SES






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scores of 24.000 and 22.75, respectively. The high SES dextrals and sinistrals in the 12-year-old age group scored significantly better than the low SES dextrals and sinistrals in that same age group.


Correlations
Table 18 lists the correlations between the independent variables of Block Design, Peabody Picture Vocabulary Test, Scholes Syntax Test, and Dichotic Listening at ages 5 and 12 years. Performance on BD is correlated .5977 with the PPVT and .5876 with the Scholes Syntax Test at 5 years and .4347 with the PPVT and .4522 with the Scholes at 12 years of age. With correlation coefficients of .3088 and .1566, respectively, the BD is less highly correlated with DL at both 5 and 12 years of age than either the PPVT or the Scholes. The PPVT and Scholes have correlation coefficients of .5471 and .4139 at 5 and 12 years. These tests are more strongly correlated with DL at age 5 than at age 12, respectively. Correlation coefficients of .3796 and .4852 were computed for DL in relation to the PPVT and for DL in relation to the Scholes Syntax Test, repsectively, at age 5. Respective correlation coefficients of .2286 and .1596 were calculated for DL in relation to the PPVT and DL in relation to the Scholes Syntax Test at age 12.






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Table 18.


BLOCK
DESIGN PEABODY SCHOLES DICHOTIC LISTENING


Table of Correlation Coefficients


Block Design 1.0000 .5977

.5876 .3088


Peabody


1.0000 .5471


.3796


Scholes Syntax


1.0000 .4857


BLOCK
DESIGN 1.0000

PEABODY .4347 1.0000

SCHOLES .4522 .4139 1.0000
(\j
DICHOTIC
LISTENING .1566 .2286 .1596 1.0000


Dichotic Listening


1.0000















CHAPTER FIVE

DISCUSSION


Dependent Variables

Dichotic Listening

In the dichotic listening paradigm employed in this study, verbal stimuli presented to the right ear were reported by subjects significantly more frequently than verbal stimuli presented to the left ear. Thus, this study also replicates a strong overall Ear effect that has been found in nearly every major study utilizing the dichotic listening technique. If, in fact, the ear asymmetry can be regarded as a reliable behavioral indicator of hemisphere dominance for the processing of verbal and non-verbal materials, then this significant Ear effect substantiates a left hemisphere dominance for speech.

This study also proposed to examine the developmental parameters of ear asymmetry, and observation of the data reveals that an ear asymmetry is present even in the 5-year-olds and that the magnitude of this asymmetry does not appreciably increase at age 12. Thus, although the total number of R + L channel responses is significantly less for the 5-year-olds as compared to the 12-year-olds, the numerical difference between mean right and mean left channel scores for both age groups is not significantly different. The onset of a true ear asymmetry at age 5 confirms the findings of Geffner and Hochberg (1971), Berlin et al. (1973), Borowy and Goebel (1976), Ingram (1975), Hiscock


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and Kinsbourne (1980), and Peck and Goodglass (1980), to mention a few. These data support the hypothesis that the left hemisphere is, to some extent, specialized for speech functions relatively early in its maturational development.

No significance between Sex effect or interactions involving Sex as an independent variable were found. Since the performance of males and females was essentially the same in this study, the obvious implication is that there are no sex differences in either the age of onset or the development of ear asymmetry. This finding supports the earlier work of Kimura (1963), Knox and Kimura (1970), Geffner and Hochberg (1971), Borowy and Goebel (1976), Berlin et al. (1973), Satz et al. (1975), and Ingram (1975).

No relationship between Handedness and ear asymmetry was found in this study. Right- and left-handed children performed equivalentaly in contrast to the findings of Bryden (1970) which suggested that the differences between dextral and sinistral children emerged gradually, developed steadily from ages 7 to 12, and became statistically significant at about 12 years of age. The percentage of right ear dominance increased with grade level in his right-handers and decreased with grade level in his left-handers. Nevertheless, these data suggest that dextral and sinistral children do not differ either in the onset of asymmetry or in the development of that asymmetry until the age of puberty.
A hypothesis of interest to this examiner was that social class

differences might appreciably affect performance on a dichotic listening task. In fact, at 5 years of age, there was no significant






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difference between the total channel recall scores of the low and high SES children, but at 12 years of age the high SES children produced significantly higher R + L channel scores than the low SES children. The magnitude of the ear asymmetry or difference between right and left channel scores was not significantly different for high and low SES children either at age 5 or at age 12. Thus, both high and low SES children manifested a significant ear asymmetry at 5 years of age in contrast to the findings of Borowy and Goebel (1976) which support a two-year lag in the attainment of an asymmetry in favor of the right ear between the middle and lower class children. These findings also differ with Geffner and Hochberg (1971) whose subjects from the lower SES group did not demonstrate a significant ear asymmetry until 7 years of age. Because the low SES subjects, particularly at the younger ages in this study, still exhibit a definite lateralization for speech, one could infer from these data that the lack of environmental stimulation usually associated with a lower socioeconomic class background did not necessarily deter the lateralization process although one might reasonably expect that it would. These findings thus lend support to the work of Knox and Kimura (1970), who found a significant ear asymmetry in 5-year-old children of a low SES background.


Block Design
Visuo-spatial performance on the Block Design subtest significantly increased as a function of Age as was expected. The high SES children had significantly better scores than the low SES children, a finding which supports the idea that the quality and/or quantity of






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environmental stimulation differentially affects the development of cortical function. The difference between SES groups is clearly seen at age 12, while no SES difference appears to be present at age 5. On an overall basis, performance on the Block Design did not vary significantly as a function of Sex or Handedness.

No appreciable difference between the performance of males and females at 5 years of age were observed, but 12-year-old males were significantly better in visuo-spatial ability than 12-year-old females. Thus, this study partially supports Witelson's (1976) hypothesis that the right hemisphere in male children is more specialized than it is in female children. However, whereas the male subjects in this study were not significantly better than their female counterparts until age 12, these data do not reinforce the developmental pattern found in Witelson's study in which the 6-year-old males manifested a right hemispheric specialization for visuo-spatial skills.

An unusual finding which is difficult for this investigator to explain involves the Age X Sex X Handedness interaction in which the 12-year-old sinistral males performed significantly better than the 12-year-old male dextrals, female dextrals, and female sinistrals. This finding is in direct contrast to the conclusions of virtually every study cited in this text which discussed age, sex, and/or handedness in relation to visuo-spatial skills (Levy, 1969, 1974; Miller, 1971; Levy and Nagalaki, 1972; McGlone and Davidson, 1973; and Yen, 1975). Even those studies which reported no spatial defect among sinistrals (Newcombe and Ratcliff, 1973; Annett and Turner, 1974; and Fennell et al., 1978) never reported finding the sinistrals to be







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superior to the dextrals in visuo-spatial skills. However, the 12-yearold dextral females in this study were significantly better on the Block Design than their sinistral counterparts, and this finding is in accordance with some of the aforementioned studies (Levy, 1969, 1974; Miller, 1971; Levy and Nagalaki, 1972; McGlone and Davidson, 1973; and Yen, 1975).

High SES males and females proved to be significantly superior to their low SES counterparts on block design performance. The low SES males performed significantly better than the low SES females, while high SES males and females were not appreciably different from each other in mean scores. When the Age X Sex X SES interaction is examined, it can be readily seen that there were no differences between any Sex X SES groups at age 5, but at age 12 both sexes of high SES were significantly better than both sexes of low SES. However, within the 12-year-old low SES subjects, the males demonstrated superior visuo-spatial skills as compared to the females. These data partially support the findings of Witelson (1976) with regard to more advanced right hemisphere specialization in males in that the low SES male subjects, even with an assumed lack of environmental stimulation, still managed to perform superiorly to females on this visuo-spatial task.


Peabody Picture Vocabulary Test

Sex and Handedness prove to be non-significant main effects in relation to performance on the PPVT. Thus, boys and girls as well as dextrals and sinistrals performed comparably on this task of semantic expertise. These data are not in agreement with the findings of those examiners who postulate a more diffuse hemispheric representation






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of language in sinistrals than in dextrals and, thus, who propose that left-handers might perform more poorly on verbal tasks. As was expected, Age was a significant main effect. Of considerable interest to this examiner is the significant SES main effect and significant interactions which consistently supported the hypothesis that children of low socioeconomic status produce inferior scores on this language test relative to the high socioeconomic status children. No significant differences were found between males and females of both SES groups.

Socioeconomic class differences in semantic skills were visible at age 5; the high SES boys and girls had significantly superior PPVT scores as compared to the low SES children of that age bracket. At age 12, this pattern of difference in language skills, according to SES class differences, continues to be maintained with low SES boys and girls scoring significantly poorer than high SES boys and girls.

When the SES and Handedness factors are considered over age groups, it is of interest to note that the poorest performance was generated by the low SES sinistral children who, hypothetically, could have been operating at a disadvantage. These children would be expected to be operating at an-environmental disadvantage for the quanity and/or quality of the stimulative factors which might enhance semantic skills. If the hypothesis of more diffused hemispheric specialization for sinistrals operates at all, it appears only under low SES conditions. Combined together, the cumulative effects of these factors might serve to explain the poor performance of the low SES sinistral 5-year-olds as compared to the low SES dextrals, high SES dextrals, and high SES sinistrals within this age group. At age 12 years, the high SES dextrals






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and sinistrals scored significantly better than the low SES dextrals and sinistrals.


Scholes Syntax Test

Consistent with the pattern generated by the three previously

discussed dependent variables, there were no significant Sex or Handedness differences found in performance on the Scholes Syntax Test. Boys and girls were comparable in syntactic skills; there were no differences between right- and left-handers on this measure of syntactic expertise. Improvement in the use of syntax increased over age, as would be expected. There were visible SES class differences in performance on this test. These differences were apparent even at age

5 when formal academic training in syntactic skills is either non-existant or just commencing. Thus, SES differences occurring at this age must primarily be accounted for by differences in environmental stimulation encountered by the low versus the high SES group.

The high SES dextrals and sinistrals in the 12-year-old age group scored signficantly better than the low SES dextrals and sinistrals in that same age group. When Handedness and SES are examined at age 5, it appears that the performances of the dextrals and sinistrals within both SES groups are comparable to each other. However, a significant difference lies between the high and low SES sinistrals. Again, as the data suggested for the PPVT scores, the low SES sinistrals demonstrate the poorest performance on this syntactic measure relative to the high SES sinistrals, high SES dextrals, and low SES dextrals.






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Correlations
At age 5, the relatively high correlation coefficient found between the Peabody Picture Vocabulary Test and the Scholes Syntax Test is not surprising as these tests are both measures of language functions. This pattern is consistent at age 12 years. The Block Design was also highly correlated with these verbal tests at both ages and this might be explained by the fact that all three of these tests employ visual cues and verbal instructions. Dichotic Listening is not highly correlated to Block Design at either age, and this would be expected as these tests are measures of different specialized hemispheric functions. Dichotic Listening is mostly highly correlated at age 5 to the Scholes Syntax Test, and this might be accounted for by the fact that both of these tests are measures of short-term memory and involve auditory sequencing. It is very lowly correlated with all other dependent measures at age 12 years.


Summary of Results
When the data are reviewed collectively, it can be clearly seen

that the Sex and Handedness independent measures were consistently noncontributory to differences in performance on the dependent measures of Dichotic Listening, Block Design, Peabody Picture Vocabulary Test, and Scholes Syntax Test. Improvement in performance was noted on all dependent measures as a function of age. However, it was unfortunate that the 8-year-old population was eliminated from this study because of sampling error as some continuity from a developmental perspective would have been provided in observation of functional asymmetries. Singularly, the socioeconomic status factor consistently proved to provide






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differences in performance on all dependent measures. The significance of the effects of socioeconomic class differences cannot be underestimated or ignored when considering the functional asymmetry of the developing brain and the cognitive growth of children.


Conclusions
Based on the data collected in this study, it would appear that optimal spatial and language performance of children of all ages depends upon neurophysiological changes in cortical development as well as upon environmental stimulation. Although this study found no difference between dextrals and sinistrals with regard to functional asymmetries, the dearth of data comparing right- and left-handers warrants future research designed to examine differences between children of different handedness groups. This research should discriminate between familial and non-familial left-handers, the former of which are proposed to have more unusual patterns of cerebral organization. Also, these findings directly support the hypothesis that there are no significant differences between males and females either in semantic and syntactic language proficiency or visuo-spatial skills and indirectly support the hypothesis that hemispheric development is not appreciably different in male and female children. Differences related to the variables of handedness and sex in the performances of males and females and/or dextralsandsinistrals become apparent only when socioeconomic class differences are taken into consideration. The effects of environment serve to contribute to more inferior or superior performances as a function of SES classification on only certain tasks at younger ages,






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but it is apparent on all tasks at age 12 years that the effects of environment serve to produce pronounced differences in the performances of children from low versus high SES classes. Some of the low SES children appear to start out at a disadvantage relative to their high SES counterparts. All low SES children in this study, nevertheless, show significant improvement over age; however, they do not achieve the levels of proficiency that the high SES children appear to achieve over the course of time from 5 years to 12 years of age. Future research on the effects of SES, particularly in relation to variables such as handedness and sex, is certainly needed.

A trend toward a significant Handedness X Ear interaction was

noted on the Dichotic Listening test with right-handers demonstrating a qreater ear asymmetry than left-handers. The Handedness X Ear X SES interaction also approached significance. This finding provides further evidence for a greater ear asymmetry in high SES dextrals and suggests that something in the experience of higher SES right-handed subjects facilitates earlier cerebral lateralization. The trend toward significance for these effects warrants that cerebral lateralization as measured by tests of functional asymmetry be further investigated, particularly with regard to Handedness and SES factors.















APPENDIX

SCHOLES SYNTAX TEST


The basis for the Scholes Syntax Test is covered in Scholes, Tanis, and Turner (1976). It is a test of syntactic comprehension based on the location and presence of the article "the" in the resolution of direct/indirect object ambiguity. This ambiguity is presented in three sets of 11 sentences each. Sentence types are shown in the following example set, where the slash indicates a pause.


Reading

I I
I I I
II II II II II
Ambiguous


Cl ue

B
A
D
AT
DT
B
A
D
AT DT


Sentence

He showed pictures to the girl's baby. He showed the girl's baby the pictures. He showed the girl's baby / pictures. It's the girl's baby the pictures were shown to. It's the girl's baby / pictures were shown to. He showed baby pictures to the girls. He showed the girls the baby pictures. He showed the girls / baby pictures. It's the girls the baby pictures were shown to. It's the girls / baby pictures were shown to. He showed the girls baby pictures.


There are two readings (I and II) of these sentence types, each

representing a different version of the direct-indirect object relationship. Several types of sentence forms (Clues) are used. B clues represent the Base form of the sentence. They are the least linguistically complex units in the sentence set and form the basis upon which other sentence types were generated. A and D forms are more complex linguistic forms of the Base sentences. In the A form the clue is based on


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the location of the article in specifying direct and indirect objects. The D form, however, is based on a simple stress; failure to process correctly the syntactic clue represented by the stress would lead to a misunderstanding of the meaning of the sentence, such that I and II Readings might be confused. AT and DT Clues are even more complex forms of the Base. The increase in linguistic complexity was designed to make the test sensitive to syntactic development at older ages, a factor of vital importance to a developmental study. Finally, the Ambiguous form of the sentence is used as a measure of Reading preferences. The interpretation a child makes of this sentence form will indicate the presence of any response sets or strategies.

Each sentence is accompanied by presentation of four pictures, one of which corresponds to the sentence Reading presented. Another will refer to the Reading corresponding to the opposing clue. The other two drawings correspond to opposing readings of another lexical set of sentences.

As an illustration, consider sentence 1, Reading A, Clue A: "He

showed the girl's baby the pictures." If the child selects the correct picture, that of a man showing pictures to a baby, it is assumed that he correctly processed the syntactic structure of the sentence. If he points to the picture of a man showing baby pictures to a lady, we presume that the child processed the lexical items correctly (i.e., man, baby, pictures, and woman), but failed to process the article clue distinguishing direct/indirect object. This is indicative of a failure to process syntactic structure. If either of the other two pictures was chosen, it would be inferred that the child failed to process the






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lexical items in the sentence. This would suggest a cognitive or semantic problem.

The child's responses will be scored as correct, incorrect, or inappropriate. A percentage of correct answers would be calculated for each response category. For an example of the picture stimuli accompanying each sentence of the Scholes Syntax Test, please see Figure 16.







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Figure 16.


( '





















Example of Pictures Presented as Stimuli in Scholes Syntax Test.
















BIBLIOGRAPHY


Annett, Marian, and Turner, Ann. Laterality and the growth of
intellectual abilities. British Journal of Educational
Psychology, 1974, 44, 37-46.

Bartz, W. H., Satz, P., Fennell, E., and Lally, J. R.
Meaningfulness and laterality in dichotic listening. Journal
of Experimental Psychology, 1967, 71, 204-210.


Berlin, C. I., Hughes, L. F., Lowe-Bell, S. S.,
Dichotic right ear advantage in children 5
1973, 9, 393-402.


and Berlin, H. L. to 13. Cortex,


Borowy, T. D., and Goebel, R. Cerebral lateralization of speech:
the effects of age, sex, race, and socioeconomic class.
Neuropsychologia, 1976, 14, 363-370.


Broadbent, D. E. The
and memory span.
47, 191-197.


role of auditory localization in attention Journal of Experimental Psychology, 1954,


Broadbent, D. E., and Gregory, M. Accuracy of recognition for
speech presented to the right and left ears. Quarterly
Journal of Experimental Psychology, 1964, 16, 359-360.


Bryden, M. P. Ear preference in auditory perception.
Experimental Psychology, 1963, 65, 103-105.

Bryden, M. P. Tachistoscopic recognition, handedness,
dominance. Neuropsychologia, 1965, 3, 1-8.


Journal of


and cerebral


Bryden, M. P. An evaluation of some models of laterality effects in
dichotic listening. Acta Otolaryngologica, 1967, 63, 595-604.


Bryden, M. P. Laterality effects in dichotic listening:
with handedness and reading ability in children.
Neuropsychologia, 1970, 8, 443-450.


Rel ations


Bryden, M. P. Dichotic listening and the development of linguistic
processes. Paper presented at the International Neuropsychology
Society, New Orleans, Louisiana, February, 1973.

Curry, F. K. W. A comparison of left- and right-handed subjects on
verbal and nonverbal dichotic listening tasks. Cortex, 1967, 3,
343-352.


-.77-






-78-


Darby, R.O. Developmental dyslexia: A possible lag mechanism.
Master's Thesis, University of Florida, 1974.

Dirks, D. Perception of dichotic and monaural verbal material and
cerebral dominance for speech. Acta Otolaryngologica, 1964,
58, 73-80.

Fennell, Eileen, Satz, P., Van den Abell, T., Bowers, Dawn, and
Thomas, R. Visuo-spatial competency, handedness and cerebral
dominance. Brain and Language, 1978, 5, 206-216.

Fletcher, J. Developmental changes in the linguistic performance
correlates of reading disability: An evaluation of a theory.
Doctoral Dissertation, University of Florida, 1978.

Geffner, D. S., and Hochberg, I. Ear laterality performance of
children from low and middle socioeconomic levels on a verbal
dichotic listening task. Cortex, 1971, 7, 193-203.

Goodglass, H., and Quadfasel, F. A. Language laterality in lefthanded aphasics. Brain, 1954, 77, 521-548.

Hecaen, H., and Ajuriaguerra, J. De. Left-Handedness. New York:
Grune and Stratton, 1964.

Hiscock, M., and Kinsbourne, M. Asymmetries of selective listening
and attention switching in children. Developmental Psychology,
1980, 16, 71-82.

Hollingshead, A. B. Two Factor Index of Social Position. New Haven:
A. B. Hollingshead, 1957.

Hummell, T. J., and Sligo, J. R. Empirical comparison of univariate
and multivariate analysis of variance procedures. Psychological
Bulletin, 1971, 76, No. 1, 49-57.

Ingram, D. Cerebral speech lateralization in young children. Neuropsychologia, 1975, 12, 103-105.

Kimura, D. Some effects of temporal lobe damage on auditory perception. Canadian Journal of Psychology, 1961a, 15, 156-165.

Kimura, D. Cerebral dominance and the perception of verbal stimuli.
Canadian Journal of Psychology, 1961b, 15, 166-171.

Kimura, D. Speech lateralization in young children as determined
by an auditory test. Journal of Comparative Physiological
Psychology, 1963, 56, 899-902.






-79-


Kimura, D. Functional asymmetry of the brain in dichotic listening.
Cortex, 1967, 3, 163-178.

Knox, C., and Kimura, D. Cerebral processing of nonverbal sounds
in boys and girls. Neuropsychologia, 1970, 8, 227-237.

Lenneberg, E. H. Biological Foundations of Language. New York:
John Wiley and Sons, 1967.

Levy, Jerre. Possible basis for the evolution of lateral
specialization of the human brain. Nature, 1969, 224, 614-615.

Levy, Jerre. Psychobiological implications of bilateral asymmetry.
In Diamond, S., and Beaumont, J. G. Hemispheric Function in
the Human Brain. New York: Halstead Press, 1974, 121-183.

Levy, Jerre, and Nagalaki, T. A model for the genetics of handedness.
Genetics, 1972, 72, 117-128.

McGlone, J., and Davidson, W. The relation between cerebral speech
laterality and spatial ability with special reference to sex
and hand preference. Neuropsychologia, 1973, 11, 105-113.

Miller, E. Handedness and the pattern of human ability. British
Journal of Psychology, 1971, 62, 111-112.
Milner, B., Branch, C., and Rasmussen, T. Observations on cerebral
dominance. In A. V. S. DeReuck and M. O'Conner (Editors), CIBA Symposium on Disorders of Language. London: J.and A.
Churchill, 1964, 200-241.

Nagafuchi, M. Development of dichotic and monaural hearing abilities
in young children. Acta Otolaryngologica, 1970, 69, 409-415.

Newcombe, Freda, and Ratcliff, G. Handedness, speech lateralization
and ability. Neuropsychologia, 1973, 2, 399-407.

Peck, E. A., and Goodglass, H. Dichotic ear asymmetries in children
ages 3 to 9. Paper presented at Eighth Annual Meeting of the
International Neuropsychology Society, San Francisco, 1980.
Richardson, D. H., and Knights, R. M. A bibliography on dichotic
listening. Cortex, 1970, 6, 236-240.

Roberts, L. Aphasia, apraxia, and agnosia in abnormal states of
cerebral dominance. In P. J. Vinken and G. W. Bruyn (Editors),
Handbook of Clinical Neurology. Amsterdam: North Holland
Publishing Company, 1969, 4, 312-316.






-80-


Rosenzweig, M. R. Representation of two cats at the auditory cortex.
American Journal of Physiology, 1951, 67, 147-158.

Satz, P., Achenbach, K., and Fennell, E. Correlations between
assessed manual laterality and predicted speech laterality in
a normal population. Neuropsychologia, 1967, 5, 295-310.

Satz, P., Achenbach, K., Pattishall, E., and Fennell, E. Order of
report, ear asymmetry, and handedness in dichotic listening.
Cortex, 1965, 1, 377-396.

Satz, P., Bakker, D. J., Teunissen, J., Goebel, R., and Van der
Vlugt, H. Developmental parameters of the ear asymmetry: A multivariate approach. Brain and Language, 1975, 2, 171-185.

Scholes, R., Tanis, D., and Turner, A. Syntactic and strategic
aspects of the comprehension of indirect and direct object
constructions by children. Language and Speech, 1976, 19.3,
212-223.

Subirana, A. Handedness and cerebral dominance. In P. J. Vinken
and G. W. Bruyn (Editors), Handbook of Clinical Neurology.
Amsterdam: North Holland Publishing Company, 1969, 4, 248272.

Teuber, H. L. Effects of brain wounds implicating right or left
hemisphere in man: Hemisphere differences and hemisphere
interaction in vision, audition, and somesthesis. In
Mountcastle, V. (Editor), Interhemispheric Relations and
Cerebral Dominance. Baltimore: Johns Hopkins Press, 1962,
264-291.

Witelson, Sandra. Sex and the single hemisphere: Specialization
of the right hemisphere for spatial processing. Science,
1976, 193, 425-427.

Yen, Wendy. Independence of hand preference and sex-linked genetic
effects on spatial performance. Perceptual Motor Skills,
1975, 41, 311-318.

Zangwill, 0. L. Cerebral Dominance and its Relation to Psychological
Function. Edinburgh: Oliver and Boyd, 1960.

Zurif, E. B., and Bryden, M. P. Familial handedness and left-right
differences in auditory and visual perception. Neuropsychologia,
1969, 7, 179-187.














BIOGRAPHICAL SKETCH


Lenay Barron Suarez was born May 26, 1948, in Tampa, Florida. The initial fourteen years of her education were in private, parochial schools and were completed with her graduation as valedictorian of her senior class from Sacred Heart Academy in May, 1966. She enrolled at the University of Florida in 1966 and completed her Bachelor of Arts degree in psychology with high honors in June, 1970. She entered the doctoral program at the University of Florida in clinical psychology in September, 1970,and received her Master of Arts degree in August, 1973. She completed her clinical internship at this institution in 1975.
She was the recipient of United States Public Health Services

Traineeships over the years 1970-1971, 1971-1972, 1972-1973. She is a member of Alpha Lambda Delta, Phi Kappa Phi, and Phi Beta Kappa.

She has been employed for four years at the Hillsborough Community Mental Health Center, Tampa, Florida, where she works one-half-time doing diagnostics and psychotherapy in Children's Outpatient Services and one-half-time in the Charles Mendez Day Care Center, a day school for emotionally handicapped children; this school is a joint project between the Hillsborough County Public School System and the Mental Health Center. She is a therapist to one classroom of this school and administers individual, group, and recreation therapy to the children of that class; in addition, she administers psychological evaluations to the Mendez


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students. She is the Hillsborough Community Mental Health Center Consultant to the Hillsborough County Head Start Program.

She has been married to Ray Suarez for nine years.









I certify that I have read this study and that in my opinion it conforms to acceptable standards of scholarly presentation and is fully adequate, in scope and quality, as a dissertation for the degree of Doctor of Philosophy.



R odmdn, Chairman Professor of Clinical Psychology

I certify that I have read this study and that in my opinion it conforms to acceptable standards of scholarly presentation and is fully adequate, in scope and quality, as a dissertation for the degree of Doctor of Philosophy.



Eileen B. Fennell
Assistant Professor of Clinical Psychology

I certify that I have read this study and that in my opinion it conforms to acceptable standards of scholarly presentation and is fully adequate, in scope and quality, as a dissertation for the degree of Doctor of Philosophy.



danes- H. Johnson
AsPociate ProYessor of Clinical Psychology


I certify that I have read this study and that in my opinion it conforms to acceptable standards of scholarly presentation and is fully adequate, in scope and quality, as a dissertation for the degree of Doctor of Philosophy.


Associate ProfesP


T lbtx -1 Pi


Psychology










I certify that I have read this study and that in my opinion it conforms to acceptable standards of scholarly presentation and is fully adequate, in scope and quality, as a dissertation for the degree of Doctor of Philosophy.



Randolph L. tarter
Assistant Professor of Statistics


This dissertation was submitted to the Graduate Faculty of the Department of Clinical Psychology in the College of Health Related Professions and to the Graduate Council, and was accepted as partial fulfillment of the requirements for the degree of Doctor of Philosophy.

December, 1981


Dean, College of Health Re1ated Professions


Dean for Graduate Studies and Research




Full Text

PAGE 1

DEVELOPMENTAL PARAMETERS OF FUNCTIONAL ASYMMETRIES AND CEREBRAL DOMINANCE IN CHILDREN By LENAY BARRON SUAREZ A DISSERTATION PRESENTED TO THE GRADUATE COUNCIL OF THE UNIVERSITY OF FLORIDA IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF DOCTOR OF PHILOSOPHY UNIVERSITY OF FLORIDA 1981

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To Ray With Love

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ACKNOWLEDGEMENTS I would like to express my appreciation to Dr. Jacquelin Goldman for her invaluable assistance in the preparation of this manuscript and for her professional assistance, encouragement and support throughout. Dr. Eileen Fennell is due a special note of thanks for her careful reading of this dissertation and her helpful constructive criticism, particularly with regard to the review of the literature and the interpretation of the data. I also gratefully acknowledge Drs. Randy Carter, Jack Fletcher, and Paul Spector for their advice and counsel on the analysis of these data and for their patience in assisting me in the interpretation of computer statistics. In addition, I would like to express my gratitude to Drs. Jim Johnson and Larry Siegel for their careful reading of the manuscript and comments. This project could not have been undertaken without the cooperation of the administration, faculty, and most especially the children of the Hillsborough County, Florida, public and private schools who were facilitative and kind in assisting my efforts in the collection of data. I thank my cousin, Tony Sanchez, Jr., and good friends, Beth and Bob Ripple, who have provided me with a home-away-from-home and a comfortable environment in which I could complete the writing of this text. Additional thanks go to Beth, who patiently read, re-read, and corrected every page of this dissertation with me.

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My thanks go to Sharon Fink and Donna Willey, who typed and retyped the manuscript without complaint. I am appreciative to my parents who have always supported me in the pursuit of academic excellence. Finally, I thank my husband, Ray, for his understanding, caring, and support. TV

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TABLE OF CONTENTS CHAPTER PAGE ACKNOWLEDGEMENTS iii LIST OF TABLES vii LIST OF FIGURES ix ABSTRACT xi ONE INTRODUCTION 1 TWO REVIEW OF THE LITERATURE 3 Dichotic Listening 3 Scholes Syntax Test and Peabody Picture Vocabulary Test 11 Block Design 12 THREE METHOD 15 Subjects 15 Dependent Variables 15 Procedure 18 Statistical Analyses 19 FOUR RESULTS 20 Multi variate Analysis 20 Univariate Analyses 21 Correlations 61 FIVE DISCUSSION 63 Dependent Variables 63 V

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Correlations 70 Summary of Results 70 Conclusions 71 APPENDIX 73 BIBLIOGRAPHY 77 BIOGRAPHICAL SKETCH 81 VI

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LIST OF TABLES Table Page 1. A Schematic Representation of the Subject Design. 16 2. Table of Significant Main Effects and Significant 22 Interactions For Independent Variables and Dependent Variables . 3. Mean Right and Left Channel Total Recall Scores and 26 Standard Deviations as a Function of Age and SES. 4. Means and Standard Deviations for the Block Design Raw 29 Scores as a Function of Age and Sex. 5. Means and Standard Deviations for the Block Design Raw 31 Scores as a Function of Age and SES. 6. Means and Standard Deviations for the Block Design Raw 32 Scores as a Function of Sex and Handedness. 7. Means and Standard Deviations for the Block Design Raw 35 Scores as a Function of Sex and SES. 8. Means and Standard Deviations for the Block Design Raw 37 Scores as a Function of Age, Sex, and Handedness. 9. Means and Standard Deviations for the Block Design Raw 40 Scores as a Function of Age, Sex, and SES. 10. Means and Standard Deviations for the Block Design Raw 42 Scores as a Function of Age, Handedness, and SES. 11. Means and Standard Deviations for the Peabody Picture 46 Vocabulary Test as a Function of Sex and SES. 12. Means and Standard Deviations for the Peabody Picture 48 Vocabulary Test as a Function of Age, Sex, and Handedness . 13. Means and Standard Deviations for the Peabody Picture 49 Vocabulary Test as a Function of Age, Sex, and SES.

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Page 14. Means and Standard Deviations for the Peabody Picture 51 Vocabulary Test as a Function of Age, Handedness, and SES. 15. Means and Standard Deviations for the Scholes Syntax 56 Test as a Function of Age and SES. 16. Means and Standard Deviations for the Scholes Syntax 58 Test as a Function of Sex and Handedness. 17. Means and Standard Deviations for the Scholes Syntax 60 Test as a Function of Age, Handedness, and SES. 18. Table of Correlation Coefficients. 62 vi i i

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LIST OF FIGURES Figure Page 1. Mean Right and Left Channel Total Scores as a Function 25 of Age and SES. 2. Block Design Mean Raw Scores as a Function of Age and 28 Sex. 3. Block Design Mean Raw Scores as a Function of Age and 30 SES. 4. Block Design Mean Raw Scores as a Function of Sex and 33 Handedness. 5. Block Design Mean Raw Scores as a Function of Sex and 34 SES. 6. Block Design Mean Raw Scores as a Function of Age, Sex, 38 and Handedness. 7. Block Design Mean Raw Scores as a Function of Age, Sex, 39 and SES. 8. Block Design Mean Raw Scores as a Function of Age, 43 Handedness, and SES. 9. Peabody Picture Vocabulary Test Mean Raw Scores as a 44 Function of Sex and SES. 10. Peabody Picture Vocabulary Test Mean Raw Scores as a 47 Function of Age, Sex, and Handedness. 11. Peabody Picture Vocabulary Test Mean Raw Scores as a 50 Function of Age, Sex, and SES. 12. Peabody Picture Vocabulary Test Mean Raw Scores as a 52 Function of Age, Handedness, and SES. 13. Scholes Syntax Test Mean Number of Correct Responses 54 as a Function of Age and SES. 14. Scholes Syntax Test Mean Number of Correct Responses 57 as a Function of Sex and Handedness. IX

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Page 15. Scholes Syntax Test Mean Number of Correct Responses 59 as a Function of Age, Handedness, and SES. 16. Example of Pictures Presented as Stimuli in Scholes 80 Syntax Test. X

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Abstract of Dissertation Presented to the Graduate Council of the University of Florida in Partial Fulfillment of the Requirements for the Degree of Doctor of Philosophy DEVELOPMENTAL PARAMETERS OF FUNCTIONAL ASYMMETRIES AND CEREBRAL DOMINANCE IN CHILDREN By Lenay Barron Suarez December 1981 Chairman: Dr. Jacquelin R. Goldman, Professor Major Department: Clinical Psychology This study investigated developmental parameters of functional asymmetries and cerebral dominance through examination of children's performances on four tasks as a function of the independent variables of age (5, 8, and 12 years), sex (male and female), handedness (right and left), and socioeconomic status (high and low SES). A dichotic listening task which involved 30 trials of 3 digits simultaneously presented to each ear at the rate of 2 pairs/second was employed as a measure of ear asymmetry. The Block Design Subtests of the Wechsler Preschool and Primary Scale of Intelligence (WPPSI) and Wechsler Intelligence Scale for Children-Revised (WISC-R) were utilized as measures of visuo-spatial competency. Form B of the Peabody Picture Vocabulary Test (PPVT) and the Scholes Syntax Test were used, respectively, as measures of semantic language ability and syntactic language proficiency. XI

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Subjects were 192 children who were chosen from the Hillsborough County, Florida, public and private school systems. They were equally divided according to age, sex, handedness, and SES such that the smallest experimental cell was comprised of 8 subjects. Statistical analyses included a multivariate analysis of variance (MANOVA), analyses of variance (ANOVA), and post hoc tests of comparison between means. Males and females performed essentially the same on Dichotic Listening, Block Design, Peabody Picture Vocabulary Test, and Scholes Syntax Tests. Likewise, there was no significant difference between the overall performance of rightand left-handers on these tasks. Age proved to be a significant main effect as demonstrated by the fact that the mean number of correct responses for all tasks increased as a function of age. A significant ear asymmetry was found at all ages, a finding which supports the hypothesis that the left hemisphere is, to some extent, specialized for speech functions relatively early in its maturational development. Significant social class differences were found; high SES children were superior in performance to low SES children on all dependent measures. Significant main effects and interactions in relation to hemispheric specialization were discussed.

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CHAPTER ONE INTRODUCTION Human brain laterality can be operationally defined as the hemispheric specialization of man's higher integrative functions, vastly significant among which are his language and visuo-spatial integrative skills. Teuber (1962) has described differential hemispheric functions in such a manner that, particularly for dextral subjects, the left side of the brain is thought to control speech and language functions while the right hemisphere is believed to control visuo-spatial and constructional skills. Lenneberg (1967) postulated that "cerebral dominance" is, in fact, assessed in terms of the asymmetrical specialization of language and non-language skills within the left and right hemispheres, respectively. The purpose of this study was to developmentally examine cerebral dominance and hemispheric specialization by observing and comparing the performances of children of different ages, sexes, socioeconomic classes, and handedness groups on tests of ear asymmetry, of semantic and syntactic language skills, and of visuo-spatial expertise. A dichotic listening test of ear asymmetry was utilized as an indirect measure of cerebral dominance for language. The Scholes Syntax Test and Peabody Picture Vocabulary Test were employed, respectively, as measures of syntactic and semantic facility with the English language; they represent abilities generally subserved by the left cerebral 1 -

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2 hemi sphere. The Block Design subtests of the Wechsler Preschool and Primary Scale of Intelligence (WPPSI) and the Wechsler Intelligence Scale for Children--Revised (WISC-R) were used as measures of visuospatial integrative function which is an ability subserved by the right cerebral hemisphere. Each of the aforementioned tests in relation to cerebral dominance will be discussed separately.

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CHAPTER TWO REVIEW OF THE LITERATURE Dichotic Listening The dichotic listening technique, originally introduced by Broadbent (1954), is an excellent measure of the ear asymmetry phenomenon. That is, it provides a direct assessment of right or left ear superiority in processing linguistic and non-linguistic information. In addition, this technique has been extensively utilized in the study of the asymmetrical specialization of the human cerebral hemispheres. It is regarded by numerous researchers as a reliable behavioral indicator of hemispheric dominance for verbal and non-verbal materials (Richardson and Knights, 1970). The dichotic listening paradigm can be operationally defined as the simultaneous and rapid presentation of disparate pairs of materials (spoken words, digits, nonsense syllables, or musical rhythms) to a subject's ears through stereophonic headphones. After an arbitrary number of paired presentations, the subject is asked to report as many of the stimuli as he can remember. It has been consistently found that adult subjects demonstrate superior recall for verbal stimuli presented to the right ear rather than the left ear after dichotic stimulation (Dirks, 1964; Bryden, 1967). The maintenance of the relative stability of an ear asymmetry favoring the right ear has been demonstrated for digits (Broadbent and Gregory, 1964; Bryden, 1963; Kimura, 1961a, 1961b; 3 -

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-4and Satz, Achenbach, Pattishall, and Fennell, 1965), nonsense syllables (Kimura, 1967), and word sequences (Bartz, Satz, Fennell, and tally, 1967). Conversely, when non-verbal stimuli are presented dichotically , adult subjects exhibit superior recall for materials presented to the left ear as compared to the right ear (Curry, 1967). Essentially, it has been postulated, particularly for dextral subjects, that speech and language functions are predominately specialized in the left cerebral hemisphere and that non-language skills are represented in the right hemisphere. An explanation of the neural structure underlying this functional asymmetry has been suggested by Kimura (1967). She hypothesized that the superior recall of verbal stimuli presented to the right ear is a direct function of more efficient connections between that ear and the speech areas in the left temporal lobe. This asymmetry can be structurally defined (^) at the cortical level, through the lateralization or dominance of speech and language, and (^) at the subcortical level, through more efficient or more numerous neural pathways between each hemisphere and its contralateral ear and less efficient pathways between each hemisphere and its ipsi lateral ear. Therefore, ipsi lateral inputs to the speech processor are believed to be occluded by contralateral inputs. At the subhuman level, Rosenzweig (1951) has provided physiological evidence for stronger contralateral ear-cortex connections in his studies with cats. An association between handedness and speech dominance has been demonstrated by Milner, Branch, and Rasmussen (1964). They found that left-handers are somewhat less likely to exhibit left-hemisphere dominance for speech as compared to right-handers. Since the dichotic

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-5listening procedure has come to be regarded, at least for experimental purposes, as a procedure which reflects the relative superiority or dominance of one cerebral hemisphere (usually the left) in the processing of meaningful language, it logically follows that a similar relationship should exist between handedness and ear asymmetry as measured by performance on dichotic listening tasks. It has been consistently reported that dextrals generally are right ear dominant for the dichotic presentation of meaningful verbal stimuli, such as words or digits, while sinistrals appear to be divided such that the majority are right ear dominant but a small percentage exhibit a left ear superiority for recall of dichotically presented verbal materials (Curry, 1967; Bryden, 1965; Satz, Achenbach, and Fennell, 1967; Satz ^ , 1965; and Zurif and Bryden, 1969). Non-familial left-handers are more likely to be right ear dominant than are familial left-handers (Zurif and Bryden, 1969). Such data could lead to the conclusion that nonfamilial left-handers are more likely to have left hemisphere speech representation than are familial left-handers who might be more disposed to have right hemisphere speech representation or bilateral speech representation. Since performance on dichotic listening tasks can be utilized as a behavioral index of speech lateralization, studies involving children at various age levels are valuable in contributing to the knowledge of developmental ear asymmetry and developmental speech lateralization. Such developmental dichotic listening studies have become a focal point of research interest in the past few years. However, there is a dearth of information as compared to the data which have been amassed on adult

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6 populations. Among the studies which have been conducted in the area of developmental ear asymmetry, there are many discrepant findings reported. Age, sex, handedness, and socioeconomic status have been found to differentially affect ear asymmetry. A review of the pertinent literature for each of these variables follows. Age There is an enormous amount of inconsistency and discrepancy among those studies which have examined the relationship of age to ear asymmetry. Kimura (1963) demonstrated a right ear superiority in children as early as age 4. She utilized a sample of 120 right-handed children ranging in age from 4 to 9 and presented them with 1, 2, and 3 pairs of digits. She found that the greatest asymmetry occurred in her youngest children and decreased with age. Knox and Kimura ‘s (1970) findings with children aged 5 through 9 years were consistent with Kimura 's (1963) data the youngest children exhibited the most ear asymmetry on dichotic listening tasks and this asymmetry seemed to decrease with age. Nagafuchi (1970) demonstrated a significant difference in ear superiority in favor of the right ear in children as young as 3 years of age and also found this asymmetry to be inversely related to age. An inverse relationship between ear asymmetry and age might lead one to conclude that the process of hemispheric polarization decreases with age. This conclusion is certainly at variance with the research of Lenneberg (1967) who has postulated that the maturational process within the child is positively correlated with the differentiation and lateralization of linguistic functions in the brain. He has proposed

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-7that by the time that language makes its appearance in the child, at around age 2, about 60 per cent of the adult values of maturation of the neurophysiological parameters of the brain are attained. This rapid maturation rate slows down and approaches an asymptote at about the same time that damage to the dominant (left) hemisphere begins to have permanent consequences. Differentiation and lateralization of language functions in the brain are highly correlated with this maturational process. Thus, during the first 10 years of life, speech and language representation evolves from a state of diffuse, bilateral representation to one of increased differentiation and lateralization within the left hemisphere. Lateralization is well established and irreversible when the maturational process has reached an advanced state, presumably at about the time of the onset of puberty. Zangwill (1960) has also suggested that the cerebral lateralization of speech is established gradually during the maturation and development of the child. However, upon closer examination of the Kimura (1963), Knox and Kimura (1970), and Nagafuchi (1970) studies, one procedural difficulty which could have contaminated their data must be noted. These studies employed a stimulus tape of great simplicity which could have enabled the older children to report nearly all of the stimuli presented to them, thereby decreasing the magnitude of the difference in recall of stimuli from the right and left ear channels. These authors' implication of an inverse relationship between ear asymmetry and age can be attributed to the fact that their older subjects reached a "ceiling" in responding, and this ceiling effect obliterated the ear asymmetry phenomenon.

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8 However, while the ceiling effect can be utilized to explain the contamination of the developmental parameters of ear asymmetry in these studies, it cannot account for the existence of ear asymmetry in children as young as 3, 4, and 5 years. Geffner and Hochberg (1971), Berlin, Hughes, Lowe-Bell, and Berlin (1973), and Borowy and Goebel (1976) have demonstrated an ear asymmetry in children of age 5. Most recently, Hiscock and Kinsbourne (1980) and Peck and Goodglass (1980) found the presence of a right-ear superiority on a dichotic listening task with children as early as age 3 as did Ingram (1975) several years earlier. These data suggest that the left hemisphere is, to some extent, specialized for speech functions very early in its maturational development. In contrast to the preceding studies which provide evidence of ear asymmetry in young children, Bryden (1973) demonstrated a later onset and more gradual development of ear asymmetry with trends toward ear asymmetry at age 10 and a significant right ear superiority at ages 12 and 14. Similarly, a study by Darby (1974) found a significant ear by age interaction in normal children at age 12. Satz, Bakker, Teunissen, Goebel, and Van der Vlugt (1975) found that a trend for right ear superiority was apparent at 5 to 6 years of age, but the difference in recall between ear channels was not significant until the age of 9 years. The amount of ear asymmetry increased positively as a function of age. These examiners concluded that age is an extremely important variable, with the quality of performance generally increasing with age for both ears. As for the ear variable, they concluded that the right ear performs significantly better than the left ear only at later ages although a trend is set up around ages 5 or 6 (Satz et §1. , 1975).

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-9Sex There are some conflicting results with regard to the question of whether or not males and females have differential development of ear asymmetry. Nagafuchi (1970) found that, at 3 years of age, females are superior to males with regard to the development of ear asymmetry, but no differences were found between males and females in the older age groups. Bryden (1970) studied children in grades 2, 4, and 6 and found major sex differences with the pattern of ear superiority emerging at grade 4 in girls but not until grade 6 for boys. In a 1963 study, Kimura found no sex differences in the development of ear asymmetry, but in a 1967 study in which she tested children of a lower socioeconomic class, she found that 5-year-old boys did not exhibit a right ear superiority while their female counterparts did show a significant right ear effect. Knox and Kimura (1970), Geffner and Hochberg (1971), Borowy and Goebel (1976), and Berlin ^ (1973) found no sex differences in their repective developmental studies of ear asymmetry. Satz eit (1975) utilized a multivariate statistical approach in the analysis of their data and computed the proportion of the variance which was accounted for by sex alone to be less than 7 per cent. These researchers have concluded that there are no sex differences associated with developmental changes in ear asymmetry. Ingram (1975) administered dichotic listening tasks to 3, 4, and 5-year-old children and found absolutely no significant difference between sexes. Bryden (1973), on the other hand, tested 120 subjects at ages 6, 7, 10, 12, and 14, and he found a pronounced sex difference in ear asymmetry in favor of the females.

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10 A1 though the majority of the studies reviewed report no sex differences in ear asymmetry, there are enough discrepancies in the liter ature to justify that this variable be further investigated. It, therefore, was analyzed in this study. Handedness Bryden (1970) attempted to discern if rightand left-handed chil dren performed differently on dichotic listening tasks. Using a sample of 144 male and female children in the 2nd, 4th, and 6th grades, he found that differences between rightand left-handers emerged grad ually and became statistically significant at grade 6 in which the children are approximately 11 to 12 years of age. The percentage of right ear dominance increased with grade level in the right-handers and decreased with grade level in the left-handers. There are some procedural difficulties to be noted in this study. The first difficulty lies in the fact that each subject performed on 2 tasks of only 10 trials each. The second problem which exists is in regard to the fact that Bryden did not control for the socioeconomic class of his subjects in this study. Socioeconomic class has been shown to be a significant variable in developmental studies of ear asymmetry. Socioeconomic Status Geffner and Hochberg (1971) found that subjects from middle and higher socioeconomic groups manifested a significant ear asymmetry at 4 years of age while subjects from the lower socioeconomic groups did not demonstrate a significant ear asymmetry until 7 years of age. Borowy and Goebel (1976) found that middle class subjects showed a

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-nsignificantly greater degree of asymmetry than their lower class counterparts. They demonstrated an approximate 2-year lag in the attainment of total right ear recall between the middle and lower social classes. The variable of socioeconomic status is definitely one which warrants further research in its relation to ear asymmetry and cerebral lateralization in children. To summarize and simplify, this study proposed to consider several questions regarding the ear asymmetry phenomenon. They are: (1) At what age does ear asymmetry manifest itself? (2) Does the magnitude of the ear asymmetry increase developmental ly with age? (3) Is ear asymmetry independent of sex? (4) Does ear asymmetry manifest itself differently in rightand left-handed children? and (5) Does the ear asymmetry developmental ly manifest itself differently in children of higher versus lower socioeconomic status? Scholes Syntax Test and Peabody Picture Vocabulary Test These two tests are not commonly utilized as behavioral indices of cerebral lateralization as is the dichotic listening task, but they are representative of semantic and syntactic linguistic functions which are, for nearly all of the dextral population and for the majority of the sinistral population, subserved and mediated by the left hemisphere. It is expected that semantic and syntactic skills will increase with age in children of a normal population. Other questions which are examined include (1) Do children of low socioeconomic status have inferior scores on these language tasks relative to high socioeconomic status children? (2) Is there any difference between the scores of males and females on these tasks? and (3) Do rightand left-handers perform

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12 differentially with regard to semantic and syntactic abilities? This last question is of great interest because various experimental data have supported the hypothesis that language may be more diffusely represented in sinistrals than in dextrals at the higher cortical level (Goodglass and Quadfasel , 1954; Zangwill, 1960; Hecaen and Ajuriaguerra , 1964; Subirana, 1969; and Roberts, 1969). Block Design Test The right cerebral hemisphere aides in non-linguistic, visualand tactile-spatial processing. While it seems that most studies of cerebral dominance and hemispheric specialization from a developmental perspective have focused on left hemispheric function, the importance of "hemisphere specialization for spatial processing may be critical in human ontogenetic and possibly in phylogenetic development of lateralization of function in general, and it is an important aspect of the neural substrate of cognition" (Witelson, 1976, p. 425). Yen (1975) compared the paper-and-pencil spatial performance of dextral and sinistral high school students of which 1236 were males and 1241 were females. She found that there were no differences in the performance of rightand left-handed females but that left-handed males on the average performed worse than right-handers on spatial tasks. Miller (1971) reported that the spatial performance of psychology undergraduates was poorer for subjects with mixed-handedness than for those with right-handedness although there was no significant difference between the two groups on verbal performance. Similarly, Levy (1969) selected a subject pool of dextral and sinistral graduate students with matching verbal scores on the Wechsler Adult Intelligence

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13 Scale (WAIS) and found that the scores of the right-handers were significantly superior to the scores of the left-handers. She postulated a sort of brain symmetry among the sinistrals in which both hemispheres subserve speech. Thus, visuo-spatial functioning in these sinistrals was "down" because the right hemisphere was mediating two functions -the linguistic as well as the visualand tactile-spatial. In more recent studies. Levy (1974) and Levy and Nagalaki (1972) proposed that among sinistrals, a percentage of which have less complete or bilateral speech representation, one might expect to observe lowered spatial abilities relative to verbal language skills. The rationale for this conclusion is that in cases of bilateral or incomplete speech lateralization, there should be a disadvantage associated with those spatial functions subserved by the right hemisphere. McGlone and Davidson (1973) found a non-significant trend for right-handed males and females to perform superiorly as compared to their left-handed counterparts on the WAIS Block Design subtest and on an altered version of the Primary Mental Abilities Spatial Relations . In contrast, there are those investigators whose studies report no handedness effect on spatial performance. Newcombe and Ratcliff (1973) found that right-, mixed-, and left-handed adults performed equivalently on the verbal and performance subtests of the WAIS. They found no significant differences between sexes either. Likewise, Annett and Turner (1974) tested elementary school students on Draw-A-Man maze, and vocabulary tests and found no significant handedness or sex effects. Fennell, Satz, Van der Abell, Bowers, and Thomas (1978) failed to provide evidence for a spatial defect in normal left-handed adults.

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-14Wi tel son (1976) studied specialization of the right hemisphere for spatial processing in 200 normal males and females between 6 and 13 years of age. She found that for boys as young as 6 years, the right hemisphere is specialized for spatial processing, but that for girls, spatial processing appears to be a bilateral function until puberty. She postulated a greater plasticity in the developing female brain which is associated with fewer language disorders than are found among boys. This study utilized comparison of scores on the Block Design subtest of the Wechsler Preschool and Primary Scale of Intelligence (WPPSI) for the 5-year-olds and the Wechsler Intelligence Scale for Children — Revised (WISC-R) Block Design subtest for the 8 and 12year-olds to investigate the following questions in addition to expected increased performance scores as a function of age: (1) Do rightand left-handers perform differently on this test of visuo-spatial skill? (2) Do males and females perform differently? (3) Does socioeconomic class differentially affect the development of visuo-spatial integrative skills in children?

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CHAPTER THREE METHOD Subjects The 192 subjects (_Ss) who participated in this study were obtained from both public and private schools in Hillsborough County, Florida. All were Caucasian and of normal intelligence. They were assigned to 24 experimental cells according to the independent variables of Age (5, 8, and 12 years). Sex, Handedness, and Socioeconomic Status (SES) such that each cell was composed of 8 ^s. A graphic representation of the experimental design is shown in Table 1. Handedness was determined by (a) verbal report of the (b) by preferred hand on the manual tasks of writing, drawing, throwing a ball, cutting with scissors, and kicking, and (c) by performance on a rotor pursuit task consisting of four 20-second trials with each hand; mean performance was calculated for each hand. Subjects were assigned to high or low SES groups based on teacher evaluations and according to classification by Hollingshead's (1957) Two Factor Index of Social Posi tion involving weighted scores for occupational and educational factors. All ^s were administered a hearing test to insure that their hearing v/as within normal range. Dependent Variables The dependent variables included a Dichotic Listening (DL) test; the Block Design (BD) subtests of the WPPSI (for the 5-year-olds) and 15 -

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Table 1. A Schematic Representation of the Subject Design -16-

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-17the WISC-R (for the 8 and 12-year-o1ds) ; Form B of the Peabody Picture Vocabulary Test (PPVT); and the Scholes Syntax Test. Dichotic Listening Test The DL test was utilized as a measure of ear asymmetry. The stimulus tape was composed of 5 practice and 30 experimental trials with 3 pairs of digits comprising each trial. The digits were delivered to the ^s ' ears through stereophonic headphones in such a manner that onehalf of each pair of digits was heard in each ear in a zero-delay condition. Each trial was presented at the rate of 2 pairs/second with a 10 second intertrial interval. The digits heard on the tape were 1,2, 3, 4, 5, 8, 9, 10, 12, 13, 14, 15, and 18. They were recorded so that onset time and loudness were identical in each channel. In order to minimize the possibility that the digits may be more easily perceived from one channel versus another and to avoid possible introduction of an ear bias, this study employed certain control methods with the aim of equalizing any anomalies in the production of the tapes. The stimulus tape was constructed so that the first 15 experimental trials were identical to the second 15 experimental trials. On each S, the headphones were reversed at Trial 16 such that the digits initially presented to the right ear were now presented to the left ear and vice versa. This constituted a wi thin-subject reversal procedure. A between-subject reversal procedure was implemented by reversing the initial placement of the headphones for every other subject so that one-half the ^s heard Channel A in the right ear first and one-half the ^s heard Channel B in the right ear first. The recall condition was free recall with all responses recorded by this examiner.

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-18Peabody Picture Vocabulary Test Form B of the PPVT was utilized in this study as a measure of each ^'s language facility with word meanings. Thus, it was a measure of semantic competence. Maximum score for each ^ was 150. Block Design Subtest The Block Design subtests of the WPPSI and the WISC-R were utilized as a measure of visuo-spatial ability. Maximum scores were 20 and 62 on the WPPSI and the WISC-R, respectively. Scholes Syntax Test The Scholes Syntax Test was included in this study as a measure of syntactic ability and is described in detail in Scholes, Tanis, and Turner (1976) and in Fletcher (1978). This test consists of 33 trials in which the ^ listens to a taped sentence through headphones and must choose from four line drawings the picture which depicts the appropriate sentence meaning. Maximum score was 30. Please see the Appendix for a detailed description and explanation of this test which was prepared by Fletcher (1978, pp. 70-73). Procedure Each child was individually tested by the Examiner (^) in a quiet room in his own school. The hearing test was administered first followed by the manual preference tasks and the rotor pursuit task. In order for a child to participate in this study, he had to exhibit consistent manual preference in verbal report; on the tasks of writing, drawing, throwing a ball, kicking a ball, and cutting with scissors ; and in the mean

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-19performance over 4 trials per hand on the-rotor pursuit. If any inconsistency was apparent, then the ^ was eliminated from this study . •'-Thus, all Ss included in this study can be saidr-to be "strongly" dextral pr "strongly" sinistral. After an ^ had passed the hearing screening and showed consistency in hand preference and performance, he then was administered the PPVT, the BD, the Scholes Syntax Test, and the DL test. Statistical Analyses Data collected for each of the dependent variables were analyzed by a multivariate analysis of variance (MANOVA). In this type of analysis, the scores on the dependent variables are computed together and, for any significant independent variable,, the weighted contribution of " .A «• weach dependent variable can be readily observed. The MANOVA is extremely sensitive to group differences and is an excellent tool for controlling Type I error rates (Hummel and Sligo, 1971). Data for each dependent variable were also analyzed by separate analyses of variance (ANOVA); post hoc analyses of pairwise comparison between means included Newman-Keuls Tests and/or the Duncan's New Multiple Range Test.

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CHAPTER FOUR RESULTS Multivariate Analysis A multivariate analysis of variance (MANOVA) of the dependent variables, which included Peabody Picture Vocabulary Test (PPVT) raw scores. Block Design (BD) raw scores, Scholes Syntax Test total number correct, and Dichotic Listening (DL) Right + Left Channel Total scores, was computed on the 128 ^s who comprised the 5-year-old and 12-year-old populations. Data from the 8-year-old population were not included in the MANOVA because preliminary analysis indicated that a disproportionate number of this age group were bilingual. Thus, the 8-year-olds were not thought to be a representative sample of the population and were, therefore, excluded from this study. The Age factor (F=187. 05234; ^=4/110; £< .0001 ) and the SES factor (F=20. 05473; df=4/l 10; £ < .0001) were found to be significant independent variables. The main effects of Sex and Handedness were not significant. Correlation coefficients of .81 for the PPVT, .75 for the BD, .55 for the Scholes, and .44 for R + L Channel Total illustrate the relative association of each of these dependent variables with the Age effect. For the SES effect, the correlation coefficients were .83 for the PPVT, .71 for the BD, .59 for the Scholes, and .39 for the R + L Channel Total. Thus, the significance of these main effects appears to be most related to the ^s' performances on the Peabody and Block Design Tests. 20 -

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21 The Age X SES interaction was significant (F=7. 05592; ^=4/110; £ < .0001) with correlation coefficients as follows: BD, .95; R + L Total, .46; Scholes, .39; and PPVT, .28. The Sex X Hand effect approached significance (F=2. 18102; df=4/l 10; £ < .0748), and relative association of the dependent variables to this two-way interaction were BD, .80; Scholes, .66; PPVT, .20; and R + L Total, -0.092. The Sex X SES interaction also approached significance (F=2.2224; ^=4/110; £ < .0702), and correlation coefficients were as follows: BD, .91; PPVT, .57; Scholes, .20; and R + L Total , -.07. The Age X Sex X SES interaction was significant (F=2.5323; 4/110; £ < .0437) with correlation coefficients of .95 for the BD, .59 for the PPVT, .29 for the Scholes, and .08 for the R + L Total. Correlation coefficients of .68 for the PPVT, .66 for the Scholes, .59 for the BD, and -0.15 for the R + L Total illustrate the relative association of the dependent variables with the Age X Hand X SES interaction (F= 3.5928; ^=4/110; £ < .0001 ). Finally, the Age X Sex X Handedness X SES interaction was significant (F=2. 52258; df=4/l 10; £ < .0443) with correlation coefficients of .75 for the BD, .00 for the Scholes, -.08 for the PPVT, and -.47 for the R + L Total . Univariate Analyses Table 2 delineates all significant main effects of the independent variables of Age, Sex, Handedness, and SES in relation to the dependent variables of Dichotic Listening (DL), Block Design raw scores (BD), Peabody Picture Vocabulary Test (PPVT), and Scholes Syntax Test. Performance relative to each of these dependent variables is discussed separately.

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22 Table 2. Table of Significant Main Effects and Significant Interactions for Independent Variables and Dependent Variables DL BDR PPVT SCHOLES AGE * * * * SES * * * * AGE X SEX * AGE X SES * * * SEX X HANDEDNESS * * SEX X SES * * AGE X SEX X HANDEDNESS * * AGE X SEX X SES * * AGE X HANDEDNESS X SES * * * AGE X SEX X HANDEDNESS X SES *

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-23Dichotic Listening Analysis of the DL data included a five-way analysis of variance of right channel and left channel recall scores with Age, Sex, Handedness, and SES as between-subjects measures and with Ear as a withinsubject repeated measure; Duncan's New Multiple Range Test was utilized for post hoc pairwise comparison among means. Right channel and left channel total recall scores were analyzed in a four-way analysis of variance with Age, Sex, Handedness, and SES as between-subjects measures; Newman-Keuls analyses were utilized as post hoc tests of pairwise comparison among means. As was expected. Age was a significant independent variable. A mean R + L channel total recall score of 106.7813 (s.d.=14.00) for the 12-year-old population was significantly better than a mean recall score of 80.7188 (s.d.=9.87) for the 5-year-old population (F=148.37; ^=1/112; £< .0001 ). A total R + L channel mean recall of 97.5469 (s.d.=11.05) for the high SES children was significantly more superior than 89.9531 (s.d.=13.09) for the low SES children (F=12.53; ^=1/112; £ < .0006. The Ear main effect also proved to be significant with a 51.52 (s.d.=13.37) mean right channel recall in contrast to a 42.24 (s.d.=14.08) mean left channel recall (F=18.12; ^=1/112; £< .0001 ). A significant ear asymmetry was found at age 5 and it remained essentially unchanged at age 12, thereby accounting for the non-significance of the Age X Ear interaction. The main effects of Sex and Handedness proved to be non-significant. Thus, there was no appreciable difference between the performance of right and left handers or between males and females on the DL task.

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-24The Age X SES interaction was significant (F=6.19; ^=1/112; £ < .0143) and is represented in Figure 1; Table 3 lists the mean right and left channel scores and the standard deviations of the 5-year-old high and low SES Ss as well as the 12-year-old high and low SES ^s. While there is no difference between the total channel recall scores of 79.593 and 81.8438 for the low and high SES 5-year-olds, respectively, the mean score of 113.25 for the 12-year-old high SES children is significantly higher than 100.3125 for the 12-year-old low SES children. As would be expected, both SES groups exhibit a significant increase in recall scores from age 5 to age 12. No other DL interactions proved to be significant, although the Handedness X Ear and the Handedness X SES X Ear interactions approached significance. Block Design Analysis of the BD data included a four-way analysis of variance of raw scores as a function of the main independent variables of Age, Sex, Handedness, and SES and Newman-Keuls analyses of post hoc comparison between means. As in the case of the DL data. Age and SES were significant main effects while Handedness and Sex were non-significant in relation to performance on this visuo-spatial task. The 12-yearold ^s' mean raw score of 33.14 (s.d.=7.55) was significantly better than the 5-year-old ^s' mean raw score of 11.40, (s.d.=3.49), (F= 429.5976; ^=1/113; £ < .0001). A mean score of 25.641 (s.d.=5.57) for the high SES children was significantly better than 18.9065 (s.d.=6.18) which was the mean score of the low SES children (F=41.2441; df=l/113; £ < . 0001 ) .

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MEAN TOTAL RECALL: RIGHT AND LEFT CHANNEL -2570 / 12 Years 0 5 Years AGE Figure 1. Mean Right and Left Channel Total Scores as a Function of Age and SES.

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-26Table 3. Mean Right + Left Channel Total Recall Scores and Standard Deviations as a Function of Age and SES 5-year-olds X s.d. LOW SES 79.5930 10.1680 HIGH SES 81.8438 9.5602 12-year-olds 2L s.d. 100.3125 15.4740 113.2500 12.3632

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-27The Age X Sex interaction proved to be significant (F=6.4923; 1/113; £ < .0122) and is illustrated in Figure 2 with means and standard deviations represented in Table 4. Both sexes improved significantly in visuo-spatial performance from age 5 to age 12. At 5 years of age, there was no appreciable difference between performance of males and females, but at age 12 years, the males' mean score of 35.25 was significantly better than the females' mean score of 31.031. The Age X SES interaction illustrated in Figure 3 was also significant (F=26.1214; ^=1/113; £ < .0001), and Table 5 contains the means and standard deviations for this interaction. For both high and low SES children, there is a significant increase in BD performance from age 5 to 12 years. Performance of high and low SES children is comparable at age 5, but 12-year-old high SES children with a mean BD score of 39.188 scored significantly higher than their low SES counterparts with a mean score of 27.094. Table 6 lists the means and standard deviations for the BD raw scores as a function of Sex and Handedness, which proved to be a significant interaction (F=5.7552; ^=1/113; £ < .0181). Sinistral males wi th a mean of 24.968 were superior to and significantly better than sinistral females and dextral males with respective mean scores of 20.906 and 21.125. Performance of dextral males and dextral females with respective means of 21 . 125 and 22.093 was without significant difference, as shown in Figure 4. The Sex X SES interaction also was significant (F=7.5989; 1/113; £ < .0068) and is graphically represented in Figure 5. Means and standard deviations are listed in Table 7. Means for high SES males and females were 24.968 and 26.312, respectively ;

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MEAN RAW SCORE -28Figure 2. Block Design Mean Raw Scores as a Function of Age and Sex.

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-29MALES FEMALES Table 4. Means and Standard Deviations for the Block Design Raw Scores as a Function of Age and Sex 5-year-olds X s ,d. 10.843 3.72 11.968 3.26 12-year-olds X s .d. 35.250 7.24 31.031 7.85

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MEAN RAW SCORE -30Figure 3. Block Design Mean Raw Scores as a Function of Age and SES.

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-31LOW SES HIGH SES Table 5. Means and Standard Deviations for the Block Design Raw Scores as a Function of Age and SES 5-year-olds ^ s ,d. 10.719 3.54 12.094 3.45 12-year-olds — s .d. 27.094 8.00 39.188 7.08

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-32Table 6. Means and Standard Deviations for the Block Design Raw Scores as a Function of Sex and Handedness Males X s .d. Females X s .d. DEXTRALS 21.125 6.19 22.093 6.80 SINISTRALS 24.968 5.29 20.906 5.09

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MEAN RAW SCORE Figure -3350 Dextrals Sinistrais 40 30 20 10 0 O Males Females 4. Block Design Mean Raw Scores as a Function of Sex and Handedness.

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MEAN RAW SCORE -34Figure 5. Block Design Mean Raw Scores as a Function of Sex and SES.

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-35LOW SES HIGH SES Table 7. Means and Standard Deviations for the Block Design Raw Scores as a Function of Sex and SES Males ^ s .d. 21.125 4.81 24.968 6.57 Females X s .d. 16.687 7.30 26.312 4.34

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-36means for low SES males and females were 21.125 and 16.687, respectively. High SES males and females proved to be significantly superior to their low SES counterparts, respectively, on BD performance. Low SES males were significantly better than low SES females, while high SES males and females were not appreciably different from each other in their mean scores. Means and standard deviations for the significant Age X Sex X Handedness interaction are shown in Table 8 (F=4.4141; ^=1/113; £ < .0379). There are no significant differences between 5-year-old dextral and sinistral males and females in their mean performance on the BD as observed in Figure 6. A significant increase in performance is evidenced for all Sex X Handedness groups from age 5 to age 12 years. At 12 years, male sinistrals with a mean score of 38.125 are significantly better than male dextrals with a mean score of 32.375, female dextrals with a mean score of 32.875, and female sinistrals with a mean score of 29.188. Female dextrals demonstrate a significant superiority relative to female sinistrals at age 12 on this task. The Age X Sex X SES interaction was significant (F=9.33; df=l/113; £ < .0028) and is graphically illustrated in Figure 7. Means and standard deviations, listed in Table 9, suggest that there are no differences between Sex X SES groups at age 5 and that a significant increase occurs from age 5 to age 12 years for all Sex X SES groups. Twelveyear-old high SES males and females with respective mean scores of 38.25 and 40.125 are both significantly better on this visuo-spatial task than 12-year-old low SES males and females with mean scores of 32.25 and 22.56, respecti vely . Also, low SES males performed significantly better than low SES females at age 12 years.

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-37DEXTRALS SINISTRALS Table 8. Means and Standard Deviations for the Block Design Raw Scores as a Function of Age, Sex, and Handedness 5-year-olds Males Females _X s.d. J s.d, 9.875 4.22 11.312 3.22 1.812 3.13 12.625 3.29 12-year-olds Males Females K s.d. J s.d. 32.375 7.66 32.875 9.06 38.125 6.80 29.188 6.40

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MEAN RAW SCORE 38 Figure 6. Block Design Mean Raw Scores as a Function of Age, Sex, and Handedness .

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MEAN RAW SCORE -39Figure 7. Block Design Mean Raw Scores as a Function of Age, Sex, and SES.

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-40Table 9. Means and Standard Deviations for the Block Design Raw Scores as a Function of Age, Sex, and SES 5-year-olds 12-year-olds Males Females Males Females X s .d. X s .d. X s .d. X s .d. LOW SES 10.000 3.83 11.437 3.21 32.250 5.62 22.560 8.56 HIGH SES 11.690 3.59 12.500 3.31 38.250 9.81 40.125 5.18

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-41Table 10 illustrates the means and standard deviations for the Age X Handedness X SES interaction which was significant (F=5.0625; ^=1/113; £< .0264), and Figure 8 illustrates the graphic representation of this interaction. At age 5 years, there are no significant differences between any of the Handedness X SES groups. At age 12 years, high SES dextrals and sinistrals with respective means of 39.812 and 38.562 performed significantly better than both low SES dextrals and sinistrals with respective means of 25.437 and 28.750. High SES dextrals scored comparably to high SES sinistrals as did low SES dextrals and sinistrals to each other. Peabody Picture Vocabulary Test (PPVT) Analysis of the PPVT data included a four-way analysis of variance of the number of correct responses as a function of the independent variables of Age, Sex, Handedness, and SES and Newman-Keuls analyses of post hoc comparison between means. Age was a significant main effect (F=504.0388; ^=1/113; £ < .0001) suggesting that, as would be expected, semantic skills increase with age. There is a significant increase from age 5 with a mean of 54.453 (s.d.=6.26) correct responses to a mean of 93.4219 (s.d.=12.27) correct responses at age 12. The SES main effect is also significant with high SES children producing 80.4995 (s.d.=10.59) mean correct responses as compared to 67.3745 (s.d.=8.81) mean correct responses produced by the low SES children. The Sex X SES interaction, which was significant (F=2.9873; 1/113; £ < .0867), is graphically represented in Figure 9. There are no significant differences between males and females of low SES or between males and females of high SES. The high SES males and females.

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-42Table 10. Means and Standard Deviations for the Block Design Raw Scores as a Function of Age, Handedness, and SES 5-year-olds 12-year-olds High X SES s.d. X Low SES s.d. High SES X s.d. Low X SES s.d. DEXTRALS 10.062 3.88 11.125 3.63 39.812 7.47 25.437 9.22 SINISTRALS 14.125 2.97 10.312 3.43 38.562 6.66 28.750 6.55

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MEAN RAW SCORE 43 Figure 8. Block Design Mean Raw Scores as a Function of Age, Handedness, and SES.

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105 100 95 90 85 80 75 70 65 60 55 50 0 9 . 44 A— A Males Females Low SES High SES eabody Picture Vocabulary Test Mean Raw Scores as a unction of Sex and SES.

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-45with respective means of 79.093 and 81.906, scored significantly higher than low SES males and females, with respective mean scores of 68.968 and 65.781. These means and standard deviations are listed in Table 11. The significance of this interaction is primarily accounted for by differences in the performances of high versus low SES groups as opposed to differences between males and females. The Age X Sex X Handedness interaction proved to be significant (F=3. 57363; ^=1/113; £ < .0613) and is graphed in Figure 10. Means and standard deviations shown in Table 12 demonstrate that the significance of this interaction must be accounted for entirely by age differences since all Sex X Handedness groups increased dramatically from ages 5 to 12 years. No Sex X Hand differences in mean scores are significant within age groups. Table 13 lists the PPVT means and standard deviations for the Age X Sex X SES interaction which was also significant (F=3.5736; ^=1/113; £ < .0613). Figure 11 illustrates that at age 5 years, high SES males and females with respective means of 59.2500 and 60.1250 are significantly better than low SES males and females with respective means of 48.50 and 49.9375. At age 12, high SES males and females with respective means of 98.9375 and 103.6875 demonstrate significantly better performance than low SES males and females with respective means of 89.4375 and 81.6250. Within the low SES 12-year-old group, males had significantly better scores than females. The means and standard deviations for the significant Age X Handedness X SES interaction (F=6.8150; df=l /1 1 3 ; £ < .0103) are shown in Table 14. The graphic representation of the means in Figure 12 displays

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-46Table 11. Means and Standard Deviations for the Peabody Picture Vocabulary Test as a Function of Sex and SES Males Females X s.d. X s.d. LOW SES 68.968 10.62 65.781 6.51 HIGH SES 79.093 12.37 81.906 8.44

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MEAN RAW SCORE -475 Years |2 Years AGE Figure 10. Peabody Picture Vocabulary Test Mean Raw Scores as a Function of Age, Sex, and Handedness.

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-48Table 12. Means and Standard Deviations for the Peabody Picture Vocabulary Test as a Function of Age, Sex, and Handedness 5-year-olds 12-year-olds Males Females Males Females X s.d. X s.d. X s.d. X s DEXTRALS 55.5625 6.91 54.5000 6.07 91.4375 16.88 94.2500 9 SINISTRALS 52.1875 7.52 55.5625 3.94 96.9375 11.95 91.0625 8

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-49Table 13. Means and Standard Deviations for the Peabody Picture Vocabulary Test as a Function of Age, Sex, and SES 5-year-olds Males Females A s.d. J s.d. LOW SES 48.5000 9.05 49.9375 5.55 HIGH SES 59.2500 4.74 60.1250 4.64 12-year-olds Males Females A s.d. J s.d. 89.4375 11.99 81.6250 7.35 98.9375 16.84 103.6875 11.00

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105 100 95 90 85 80 75 70 65 60 55 50 45 0 n. O O Females, High SES O O Females, Low SES Males, High SES 5 Years I 12 Years AGE 3abody Picture Vocabulary Test Mean Raw Scores as a jnction of Age, Sex, and SES.

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-51Table 14. Means and Standard Deviations for the Peabody Picture Vocabulary Test as a Function of Age, Handedness, and SES 5-year-olds Dextrals Sinistrals ^ s.d. X s.d. LOW SES 51.6875 7.27 46.7500 7.73 12-year-olds Dextrals Sinistrals X s.d. s.d. 82.3125 7.82 88.7500 11.69 HIGH SES 58.3750 5.63 61.0000 3.52 103.3750 17.92 99.2500 9.15

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105 100 95 90 85 80 75 70 65 60 55 50 45 0 12 . • • Dextral, High SES Dextral, Low SES L Sinistral, High SES ^ A Sinistral, Low SES / / //' / / / I 5 Years I 12 Years AGE ^eabody Picture Vocabulary Test Mean Raw Scores as a -unction of Age, Handedness, and SES.

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-53that at age 5 years, the high SES dextrals and sinistrals with means of 58.3750 and 61.000, respectively, perform significantly better than the low SES sinistrals with a mean number of correct responses of 46.75, but not better than the low SES dextrals with a mean score of 51.6875. All Handedness X SES groups increased significantly with age. At age 12, low SES dextrals and sinistrals performed comparably with means of 82.3125 and 88.7500; high SES dextrals and sinistrals also performed comparably with means of 103.3750 and 99.2500. High SES 12-year-olds, both dextral and sinistral, scored significantly better than low SES 12-year-olds, both dextral and sinistral. Scholes Syntax Test Analysis of the Scholes Syntax Test data included a four-way analysis of variance of the number of correct responses as a function of the independent variables of Age, Sex, Handedness, and SES, and NewmanKeuls analysis of post hoc comparison between means. Consistent with the other dependent variables already discussed. Age was a significant main effect in generating differential performance on the Scholes (F= 233.7163; df=l/113; £ < .0001). There was a significant increase in scores from 17.4844 (s.d.=3.08) at age 5 to 25.2656 (s.d.=3.81) at age 12. SES was also a significant main effect (F=28.5318; ^=1/113; £ < .0001) with high SES children scoring 22.7344 (s.d.=2.80) which was significantly better than the low SES children's score of 20.0156 (s.d.=4.02). The main effects of Sex and Handedness were non-significant. Figure 13 is the graphic representation of the Age X SES interaction which proved to be significant (F=4.3576; ^=1/113; £ < .0391).

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MEAN NUMBER CORRECT RESPONSES -54Figure 13. Scholes Syntax Test Mean Number of Correct Responses as a Function of Age and SES.

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-55lable 15 lists the means and standard deviations for this interaction. At age 5 years, high SES children with a mean score of 18.3125 performed significantly better than low SES children with a mean score of 16.6562. A significant increase in number of correct responses was evidenced for both SES groups from age 5 to age 12. At age 12, the high SES children again scored significantly better than the low SES children with respective means of 27.1562 and 23.3750. The Sex X Handedness interaction was significant and is shown in Figure 14 (F=3.8600; ^=1/113; £ < .0519); means and standard deviations are listed in Table 16. Comparable scores were elicited from sinistral males and sinistral females, from dextral males and dextral females, and from dextral and sinistral females. The only significant difference lies between the sinistral males (7=22.21) and the dextral males (x=20.50). Finally, the Age X Handedness X SES interaction was significant (F=6.3366; ^=1/113; £ < .0132) and is graphically presented in Figure 15. At age 5 years, high SES sinistrals with a mean score of 19.6875 are significantly better than low SES sinistrals with a mean score of 16.000. There was no appreciable difference in the scores of the high SES dextrals, the low SES dextrals, or the low SES sinistrals in this age group. A significant increase in scores was evidenced for all SES X Handedness groups from age 5 to age 12 years as is readily seen in Figure 15 and Table 17. At age 12 years, the high SES dextrals and sinistrals had comparable mean scores of 27.0625 and 27.25, respectively; the low SES sinistrals and dextrals also had comparable mean

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-56LOW SES HIGH SES Table 15. Means and Standard Deviations for the Scholes Syntax Test as a Function of Age and SES 5yearolds A s.d. 16.6562 2.75 18.3125 3.38 12-yearolds ^ s.d. 23.3750 4.97 27.1562 2.07

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MEAN NUMBER CORRECT RESPONSES -5750 r A A Sinistral Dextral 40 30 20 AO10 0 Males Females Figure 14. Scholes Syntax Test Mean Number of Correct Responses as a Function of Sex and Handedness.

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-58Table 16. Means and Standard Deviations for the Scholes Syntax Test as a Function of Sex and Handedness X Males s.d. Females X s.d. DEXTRALS 20.50 2.64 21.25 3.50 SINISTRALS 22.21 4.74 21.53 2.52

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MEAN NUMBER CORRECT RESPONSES -59Figure 15. Scholes Syntax Test Mean Number of Correct Responses as a Function of Age, Handedness, and SES.

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-60Table 17. Means and Standard Deviations for the Scholes Syntax Test as a Function of Age, Handedness, and SES 5-yearolds 12-yearolds Dextrals Sinistrals Dextrals Sinistrals X s.d. X s.d. X s.d. X s.d. LOW SES 17.3125 3.13 16.0000 2.31 22.7500 3.51 24.0000 6.09 HIGH SES 16.9375 3.71 19.6875 3.00 27.0625 1.56 27.2500 2.48

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-61scores of 24.000 and 22.75, respectively. The high SES dextrals and sinistrals in the 12-year-old age group scored significantly better than the low SES dextrals and sinistrals in that same age group. Correlations Table 18 lists the correlations between the independent variables of Block Design, Peabody Picture Vocabulary Test, Scholes Syntax Test, and Dichotic Listening at ages 5 and 12 years. Performance on BD is correlated .5977 with the PPVT and .5876 with the Scholes Syntax Test at 5 years and .4347 with the PPVT and .4522 with the Scholes at 12 years of age. With correlation coefficients of .3088 and .1566, respectively, the BD is less highly correlated with DL at both 5 and 12 years of age than either the PPVT or the Scholes. The PPVT and Scholes have correlation coefficients of .5471 and .4139 at 5 and 12 years. These tests are more strongly correlated with DL at age 5 than at age 12, respectively. Correlation coefficients of .3796 and .4852 were computed for DL in relation to the PPVT and for DL in relation to the Scholes Syntax Test, repsecti vely , at age 5. Respective correlation coefficients of .2286 and .1596 were calculated for DL in relation to the PPVT and DL in relation to the Scholes Syntax Test at age 12.

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12 -year -olds 5yearolds -62Table 18. Table of Correlation Coefficients Block Scholes Dichotic Design BLOCK DESIGN 1 .0000 PEABODY .5977 SCHOLES .5876 DICHOTIC LISTENING .3088 BLOCK DESIGN 1.0000 PEABODY .4347 SCHOLES .4522 Peabody Syntax Listening 1.0000 .5471 1 .0000 .3796 .4857 1.0000 1.0000 .4139 1.0000 DICHOTIC LISTENING .1566 .2286 .1596 1.0000

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CHAPTER FIVE DISCUSSION Dependent Variables Dichotic Listening In the dichotic listening paradigm employed in this study, verbal stimuli presented to the right ear were reported by subjects significantly more frequently than verbal stimuli presented to the left ear. Thus, this study also replicates a strong overall Ear effect that has been found in nearly every major study utilizing the dichotic listening technique. If, in fact, the ear asymmetry can be regarded as a reliable behavioral indicator of hemisphere dominance for the processing of verbal and non-verbal materials, then this significant Ear effect substantiates a left hemisphere dominance for speech. This study also proposed to examine the developmental parameters of ear asymmetry, and observation of the data reveals that an ear asymmetry is present even in the 5-year-olds and that the magnitude of this asymmetry does not appreciably increase at age 12. Thus, although the total number of R + L channel responses is significantly less for the 5-year-olds as compared to the 12-year-olds, the numerical difference between mean right and mean left channel scores for both age groups is not significantly different. The onset of a true ear asymmetry at age 5 confirms the findings of Geffner and Hochberg (1971), Berlin ^ (1973), Borowy and Goebel (1976), Ingram (1975), Hiscock 63 -

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-64and Kinsbourne (1980), and Peck and Goodglass (1980), to mention a few. These data support the hypothesis that the left hemisphere is, to some extent, specialized for speech functions relatively early in its maturational development. No significance between Sex effect or interactions involving Sex as an independent variable were found. Since the performance of males and females was essentially the same in this study, the obvious implication is that there are no sex differences in either the age of onset or the development of ear asymmetry. This finding supports the earlier work of Kimura (1963), Knox and Kimura (1970), Geffner and Hochberg (1971), Borowy and Goebel (1976), Berlin ^ (1973), Satz et al . (1975), and Ingram (1975). No relationship between Handedness and ear asymmetry was found in this study. Rightand left-handed children performed equi valentaly in contrast to the findings of Bryden (1970) which suggested that the differences between dextral and sinistral children emerged gradually, developed steadily from ages 7 to 12, and became statistically significant at about 12 years of age. The percentage of right ear dominance increased with grade level in his right-handers and decreased with grade level in his left-handers. Nevertheless, these data suggest that dextral and sinistral children do not differ either in the onset of asymmetry or in the development of that asymmetry until the age of puberty. A hypothesis of interest to this examiner was that social class differences might appreciably affect performance on a dichotic listening task. In fact, at 5 years of age, there was no significant

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-65difference between the total channel recall scores of the low and high SES children, but at 12 years of age the high SES children produced significantly higher R + L channel scores than the low SES children. The magnitude of the ear asymmetry or difference between right and left channel scores was not significantly different for high and low SES children either at age 5 or at age 12. Thus, both high and low SES children manifested a significant ear asymmetry at 5 years of age in contrast to the findings of Borowy and Goebel (1976) which support a two-year lag in the attainment of an asymmetry in favor of the right ear between the middle and lower class children. These findings also differ with Geffner and Hochberg (1971) whose subjects from the lower SES group did not demonstrate a significant ear asymmetry until 7 years of age. Because the low SES subjects, particularly at the younger ages in this study, still exhibit a definite lateralization for speech, one could infer from these data that the lack of environmental stimulation usually associated with a lower socioeconomic class background did not necessarily deter the lateralization process although one might reasonably expect that it would. These findings thus lend support to the work of Knox and Kimura (1970), who found a significant ear asymmetry in 5-year-old children of a low SES background. Block Design Visuo-spatial performance on the Block Design subtest significantly increased as a function of Age as was expected. The high SES children had significantly better scores than the low SES children, a finding which supports the idea that the quality and/or quantity of

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66 environmental stimulation differentially affects the development of cortical function. The difference between SES groups is clearly seen at age 12, while no SES difference appears to be present at age 5. On an overall basis, performance on the Block Design did not vary significantly as a function of Sex or Handedness. No appreciable difference between the performance of males and females at 5 years of age were observed, but 12-year-old males were significantly better in visuo-spatial ability than 12-year-old females. Thus, this study partially supports Witelson's (1976) hypothesis that the right hemisphere in male children is more specialized than it is in female children. However, whereas the male subjects in this study were not significantly better than their female counterparts until age 12, these data do not reinforce the developmental pattern found in Witelson's study in which the 6-year-old males manifested a right hemispheric specialization for visuo-spatial skills. An unusual finding which is difficult for this investigator to explain involves the Age X Sex X Handedness interaction in which the 12-year-old sinistral males performed significantly better than the 12-year-old male dextrals, female dextrals, and female sinistrals. This finding is in direct contrast to the conclusions of virtually every study cited in this text which discussed age, sex, and/or handedness in relation to visuo-spatial skills (Levy, 1969, 1974; Miller, 1971; Levy and Nagalaki, 1972; McGlone and Davidson, 1973; and Yen, 1975). Even those studies which reported no spatial defect among sinistrals (Newcombe and Ratcliff, 1973; Annett and Turner, 1974; and Fennell et ^. , 1978) never reported finding the sinistrals to be

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-67superior to the dextrals in visuo-spatial skills. However, the 12-yearold dextral females in this study were significantly better on the Block Design than their sinistral counterparts, and this finding is in accordance with some of the aforementioned studies (Levy, 1969, 1974; Miller, 1971; Levy and Nagalaki, 1972; McGlone and Davidson, 1973; and Yen, 1975). High SES males and females proved to be significantly superior to their low SES counterparts on block design performance. The low SES males performed significantly better than the low SES females, while high SES males and females were not appreciably different from each other in mean scores. When the Age X Sex X SES interaction is examined, it can be readily seen that there were no differences between any Sex X SES groups at age 5, but at age 12 both sexes of high SES were significantly better than both sexes of low SES. However, within the 12-year-old low SES subjects, the males demonstrated superior visuo-spatial skills as compared to the females. These data partially support the findings of Wi tel son (1976) with regard to more advanced right hemisphere specialization in males in that the low SES male subjects, even with an assumed lack of environmental stimulation, still managed to perform superiorly to females on this visuo-spatial task. Peabody Picture Vocabulary Test Sex and Handedness prove to be non-significant main effects in relation to performance on the PPVT. Thus, boys and girls as well as dextrals and sinistrals performed comparably on this task of semantic expertise. These data are not in agreement with the findings of those examiners who postulate a more diffuse hemispheric representation

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68 of language in sinistrals than in dextrals and, thus, who propose that left-handers might perform more poorly on verbal tasks. As was expected. Age was a significant main effect. Of considerable interest to this examiner is the significant SES main effect and significant interactions which consistently supported the hypothesis that children of low socioeconomic status produce inferior scores on this language test relative to the high socioeconomic status children. No significant differences were found between males and females of both SES groups. Socioeconomic class differences in semantic skills were visible at age 5; the high SES boys and girls had significantly superior PPVT scores as compared to the low SES children of that age bracket. At age 12, this pattern of difference in language skills, according to SES class differences, continues to be maintained with low SES boys and girls scoring significantly poorer than high SES boys and girls. When the SES and Handedness factors are considered over age groups, it is of interest to note that the poorest performance was generated by the low SES sinistral children who, hypothetical ly , could have been operating at a disadvantage. These children would be expected to be operating at an environmental disadvantage for the quanity and/or quality of the stimulative factors which might enhance semantic skills. If the hypothesis of more diffused hemispheric specialization for sinistrals operates at all, it appears only under low SES conditions. Combined together, the cumulative effects of these factors might serve to explain the poor performance of the low SES sinistral 5-year-olds as compared to the low SES dextrals, high SES dextrals, and high SES sinistrals within this age group. At age 12 years, the high SES dextrals

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-69and sinistra! s scored significantly better than the low SES dextrals and sinistrals. Scholes Syntax Test Consistent with the pattern generated by the three previously discussed dependent variables, there were no significant Sex or Handedness differences found in performance on the Scholes Syntax Test. Boys and girls were comparable in syntactic skills; there were no differences between rightand left-handers on this measure of syntactic expertise. Improvement in the use of syntax increased over age, as would be expected. There were visible SES class differences in performance on this test. These differences were apparent even at age 5 when formal academic training in syntactic skills is either non-existant or just cormiencing. Thus, SES differences occurring at this age must primarily be accounted for by differences in environmental stimulation encountered by the low versus the high SES group. The high SES dextrals and sinistrals in the 12-year-old age group scored signficantly better than the low SES dextrals and sinistrals in that same age group. When Handedness and SES are examined at age 5, it appears that the performances of the dextrals and sinistrals within both SES groups are comparable to each other. However, a significant difference lies between the high and low SES sinistrals. Again, as the data suggested for the PPVT scores, the low SES sinistrals demonstrate the poorest performance on this syntactic measure relative to the high SES sinistrals, high SES dextrals, and low SES dextrals.

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-70Correlations At age 5, the relatively high correlation coefficient found between the Peabody Picture Vocabulary Test and the Scholes Syntax Test is not surprising as these tests are both measures of language functions. This pattern is consistent at age 12 years. The Block Design was also highly correlated with these verbal tests at both ages and this might be explained by the fact that all three of these tests employ visual cues and verbal instructions. Dichotic Listening is not highly correlated to Block Design at either age, and this would be expected as these tests are measures of different specialized hemispheric functions. Dichotic Listening is mostly highly correlated at age 5 to the Scholes Syntax Test, and this might be accounted for by the fact that both of these tests are measures of short-term memory and involve auditory sequencing. It is very lowly correlated with all other dependent measures at age 12 years. Summary of Results When the data are reviewed collectively, it can be clearly seen that the Sex and Handedness independent measures were consistently noncontributory to differences in performance on the dependent measures of Dichotic Listening, Block Design, Peabody Picture Vocabulary Test, and Scholes Syntax Test. Improvement in performance was noted on all dependent measures as a function of age. However, it was unfortunate that the 8-year-old population was eliminated from this study because of sampling error as some continuity from a developmental perspective would have been provided in observation of functional asymmetries. Singularly, the socioeconomic status factor consistently proved to provide

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71 differences in performance on all dependent measures. The significance of the effects of socioeconomic class differences cannot be underestimated or ignored when considering the functional asymmetry of the developing brain and the cognitive growth of children. Conclusions Based on the data collected in this study, it would appear that optimal spatial and language performance of children of all ages depends upon neurophysiological changes in cortical development as well as upon environmental stimulation. Although this study found no difference between dextrals and sinistrals with regard to functional asymmetries, the dearth of data comparing rightand left-handers warrants future research designed to examine differences between children of different handedness groups. This research should discriminate between familial and non-familial left-handers, the former of which are proposed to have more unusual patterns of cerebral organization. Also, these findings di rectly support the hypothesis that there are no significant differences between males and females either in semantic and syntactic language proficiency or visuo-spatial skills and indirectly support the hypothesis that hemispheric development is not appreciably different in male and female children. Differences related to the variables of handedness and sex in the performances of males and females and/or dextral s and si nistral s become apparent only when socioeconomic class differences are taken into consideration. The effects of environment serve to contribute to more inferior or superior performances as a function of SES classification on only certain tasks at younger ages.

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-72but it is apparent on all tasks at age 12 years that the effects of environment serve to produce pronounced differences in the performances of children from low versus high SES classes. Some of the low SES children appear to start out at a disadvantage relative to their high SES counterparts . All low SES children in this study, nevertheless, show significant improvement over age; however, they do not achieve the levels of proficiency that the high SES children appear to achieve over the course of time from 5 years to 12 years of age. Future research on the effects of SES, particularly in relation to variables such as handedness and sex, is certainly needed. A trend toward a significant Handedness X Ear interaction was noted on the Dichotic Listening test with right-handers demonstrating a greater ear asymmetry than left-handers. The Handedness X Ear X SES interaction also approached significance. This finding provides further evidence for a greater ear asymmetry in high SES dextrals and suggests that something in the experience of higher SES right-handed subjects facilitates earlier cerebral lateralization. The trend toward significance for these effects warrants that cerebral lateralization as measured by tests of functional asymmetry be further investigated, particularly with regard to Handedness and SES factors.

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APPENDIX SCHOLES SYNTAX TEST The basis for the Scholes Syntax Test is covered in Scholes, Tanis, and Turner (1976). It is a test of syntactic comprehension based on the location and presence of the article "the" in the resolution of direct/indirect object ambiguity. This ambiguity is presented in three sets of 11 sentences each. Sentence types are shown in the following example set, where the slash indicates a pause. Readi nq Clue Sentence I I I I I II II II II II Ambiguous B A D AT DT B A D AT DT He showed pictures to the girl's baby. He showed the girl's baby the pictures. He showed the girl's baby / pictures. It's the girl's baby the pictures were shown to. It's the girl's baby / pictures were shown to. He showed baby pictures to the girls. He showed the girls the baby pictures. He showed the girls / baby pictures. It|s the girls the baby pictures were shown to. It's the girls / baby pictures were shown to. He showed the girls baby pictures. There are two readings (I and II) of these sentence types, each representing a different version of the direct-indirect object relationship. Several types of sentence forms (Clues) are used. B clues represent the Base form of the sentence. They are the least linguistically complex units in the sentence set and form the basis upon which other sentence types were generated. A and D forms are more complex linguistic forms of the Base sentences. In the A form the clue is based on 73 -

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-74the location of the article in specifying direct and indirect objects. The D form, however, is based on a simple stress; failure to process correctly the syntactic clue represented by the stress would lead to a misunderstanding of the meaning of the sentence, such that I and II Readings might be confused. AT and DT Clues are even more complex forms of the Base. The increase in linguistic complexity was designed to make the test sensitive to syntactic development at older ages, a factor of vital importance to a developmental study. Finally, the Ambiguous form of the sentence is used as a measure of Reading preferences. The interpretation a child makes of this sentence form will indicate the presence of any response sets or strategies. Each sentence is accompanied by presentation of four pictures, one of which corresponds to the sentence Reading presented. Another will refer to the Reading corresponding to the opposing clue. The other two drawings correspond to opposing readings of another lexical set of sentences. As an illustration, consider sentence 1, Reading A, Clue A: "He showed the girl's baby the pictures." If the child selects the correct picture, that of a man showing pictures to a baby, it is assumed that he correctly processed the syntactic structure of the sentence. If he points to the picture of a man showing baby pictures to a lady, we presume that the child processed the lexical items correctly (i.e., man, baby, pictures, and woman), but failed to process the article clue distinguishing direct/indirect object. This is indicative of a failure to process syntactic structure. If either of the other two pictures was chosen, it would be inferred that the child failed to process the

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-75lexical items in the sentence. This would suggest a cognitive or semantic problem. The child's responses will be scored as correct, incorrect, or inappropriate. A percentage of correct answers would be calculated for each response category. For an example of the picture stimuli accompanying each sentence of the Scholes Syntax Test, please see Figure 16.

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-76Figure 16. Example of Pictures Presented as Stimuli in Scholes Syntax Test.

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BIBLIOGRAPHY Annett, Marian, and Turner, Ann. Laterality and the growth of intellectual abilities. British Journal of Educational Psychology , 1974, U, 37-46. Bartz, W. H., Satz, P., Fennell, E., and Lally, J. R. Meaningful ness and laterality in dichotic listening. Journal of Experimental Psychology , 1967, 71_, 204-210. Berlin, C. I., Hughes, L. F., Lowe-Bell, S. S., and Berlin, H. L. Dichotic right ear adyantage in children 5 to 13. Cortex, 1973, 9, 393-402. Borowy, T. D., and Goebel, R. Cerebral lateralization of speech: the effects of age, sex, race, and socioeconomic class. Neuropsychologia . 1976, T4, 363-370. Broadbent, D. E. The role of auditory localization in attention and memory span. Journal of Experimental Psychology, 1954. 47, 191-197. ^ ^ Broadbent, D. E., and Gregory, M. Accuracy of recognition for speech presented to the right and left ears. Quarterly Journal of Experimental Psychology . 1964, 26, 359-360. Bryden, M. P. Ear preference in auditory perception. Journal of Experimental Psychology . 1963, 65, 103-105. Bryden, M. P. Tachistoscopic recognition, handedness, and cerebral dominance. Neuropsychologia , 1965, 3, 1-8. Bryden, M. P. An eyaluation of some models of laterality effects in dichotic listening. Acta Otolaryngol ogica . 1967, 63, 595-604. Bryden, M. P. Laterality effects in dichotic listening: Relations with handedness and reading ability in children Neuropsychologia . 1970, 8, 443-450. Bryden, M. P. Dichotic listening and the development of linguistic processes. Paper presented at the International Neuropsychology Society, New Orleans, Louisiana, February, 1973. Curry, F. K. W. A comparison of leftand right-handed subjects on verbal and nonverbal dichotic listening tasks. Cortex , 1967, 3, 77 -

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-78Darby, R.O. Developmental dyslexia: A possible lag mechanism. Master's Thesis, University of Florida, 1974. Dirks, D. Perception of dichotic and monaural verbal material and cerebral dominance for speech. Acta Otolaryngol oaica. 1964. 73-80. ^ Fennell, Eileen, Satz, P., Van den Abell, T., Bowers, Dawn, and Thomas, R. Visuo-spatial competency, handedness and cerebral dominance. Brain and Language , 1978, 5 , 206-216. Fletcher, J. Developmental changes in the linguistic performance correlates of reading disability: An evaluation of a theory. Doctoral Dissertation, University of Florida, 1978. Geffner, D. S., and Hochberg, I. Ear laterality performance of children from low and middle socioeconomic levels on a verbal dichotic listening task. Cortex , 1971, _7, 193-203. Goodglass, H., and Quadfasel , F. A. Language laterality in lefthanded aphasics. Brain , 1954, 77, 521-548. Hecaen, H., and Ajuriaguerra , J. De. Left-Handedness . New York: Grune and Stratton, 1964. Hiscock, M. , and Kinsbourne, M. Asymmetries of selective listening and attention switching in children. Developmental Psvcholoov. 1980, 16, 71-82. ^ Hollingshead, A. B. Two Factor Index of Social Pos ition. New Haven: A. B. Hollingshead, 1957. Hummel 1, T. J., and Sligo, J. R. Empirical comparison of univariate and multivariate analysis of variance procedures. Psychological Bulletin , 1971, 76, No. 1, 49-57. Ingram, D. Cerebral speech lateralization in young children. Neuropsychologia , 1975, 12, 103-105. Kimura, D. Some effects of temporal lobe damage on auditory perception. Canadian Journal of Psychology , 1961a, 2^, 156-165. Kimura, D. Cerebral dominance and the perception of verbal stimuli. Canadian Journal of Psychology , 1961b, 2^, 166-171. Kimura, D. Speech lateralization in young children as determined by an auditory test. Journal of Comparative Physiological Psychology , 1963, 899-902.

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-79Kimura, D. Functional asymmetry of the brain in dichotic listening. Cortex , 1967, 3, 163-178. Knox, C., and Kimura, D. Cerebral processing of nonverbal sounds in boys and girls. Neuropsychologia , 1970, 8, 227-237. Lenneberg, E. H. Biological Foundations of Language . New York: John Wiley and Sons, 1967. Levy, Jerre. Possible basis for the evolution of lateral specialization of the human brain. Nature , 1969, 224, 614-615. Levy, Jerre. Psychobiological implications of bilateral asymmetry. In Diamond, S., and Beaumont, J. G. Hemispheric Function in the Human Brain . New York: Halstead Press, 1974, 121-183. Levy, Jerre, and Nagalaki,T. A model for the genetics of handedness. Genetics , 1972, 72, 117-128. McGlone, J., and Davidson, W. The relation between cerebral speech laterality and spatial ability with special reference to sex and hand preference. Neuropsychologia , 1973, JJ_, 105-113. Miller, E. Handedness and the pattern of human ability. British Journal of Psychology , 1971, 6Z, 111-112. Milner, B., Branch, C., and Rasmussen, T. Observations on cerebral dominance. In A. V. S. DeReuck and M. O'Conner (Editors), Cl BA Symposium on Disorders of Language . London: J. andA. Churchill, 1964, 200-241. Nagafuchi , M. Development of dichotic and monaural hearing abilities in young children. Acta Otolaryngol ogica , 1970, 6^, 409-415. Newcombe, Freda, and Ratcliff, G. Handedness, speech lateralization and ability. Neuropsychologia , 1973, 2, 399-407. Peck, E. A., and Goodglass, H. Dichotic ear asymmetries in children ages 3 to 9. Paper presented at Eighth Annual Meeting of the International Neuropsychology Society, San Francisco, 1980. Richardson, D. H., and Knights, R. M. A bibliography on dichotic listening. Cortex , 1970, 6, 236-240. Roberts, L. Aphasia, apraxia, and agnosia in abnormal states of cerebral dominance. In P. J. Vinken and G. W. Bruyn (Editors), Handbook of Clinical Neurology . Amsterdam: North Holland Publishing Company, 1969, 4, 312-316.

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-80Rosenzweig, M. R. Representation of two cats at the auditory cortex American Journal of Physiology . 1951, S7_, 147-158. Satz, P. , Achenbach, K. , and Fennell, E. Correlations between assessed manual laterality and predicted speech laterality in a normal population. Neuropsycholoqia , 1967, 5, 295-310. Satz, P., Achenbach, K. , Pattishall, E., and Fennell, E. Order of report, ear asymmetry, and handedness in dichotic listening. Cortex , 1965, 377-396. Satz, P., Bakker, D. J., Teunissen, J., Goebel, R., and Van der Vlugt, H. Developmental parameters of the ear asymmetry: A multivariate approach. Brain and Language . 1975, 171-185. Scholes, R., Tanis, D., and Turner, A. Syntactic and strategic aspects of the comprehension of indirect and direct object constructions by children. Language and Speech , 1976, 19.3 , Subirana, A. Handedness and cerebral dominance. In P. J. Vinken and G. W. Bruyn (Editors), Handbook of Clinical Neurology . Amsterdam: North Holland Publishing Company, 1969, 4, 248Teuber, H. L. Effects of brain wounds implicating right or left hemisphere in man: Hemisphere differences and hemisphere interaction in vision, audition, and somesthesis. In Mountcastle, V. (Editor), Interhemi spheric Relations and Cerebral Dominance . Baltimore: Johns Hopkins Press, 1962, Witelson, Sandra. Sex and the single hemisphere: Specialization of the right hemisphere for spatial processing. Science, 1976, 193, 425-427. Yen, Wendy. Independence of hand preference and sex-linked genetic effects on spatial performance. Perceptual Motor Skills, 1975, 311-318. Zangwill, 0. L. Cerebral Dominance and its Relation to Psychologic al Function . Edinburgh: Oliver and Boyd, 1960. Zurif, E. B., and Bryden, M. P. Familial handedness and left-right differences in auditory and visual perception. Neuropsycholoqia 1969, 7, 179-187. ^ ^

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BIOGRAPHICAL SKETCH Lenay Barron Suarez was born May 26, 1948, in Tampa, Florida. The initial fourteen years of her education were in private, parochial schools and were completed with her graduation as valedictorian of her senior class from Sacred Heart Academy in May, 1966. She enrolled at the University of Florida in 1966 and completed her Bachelor of Arts degree in psychology with high honors in June, 1970. She entered the doctoral program at the University of Florida in clinical psychology in September, 1970, and received her Master of Arts degree in August, 1973. She completed her clinical internship at this institution in 1975. She was the recipient of United States Public Health Services Traineeships over the years 1970-1971, 1971-1972, 1972-1973. She is a member of Alpha Lambda Delta, Phi Kappa Phi, and Phi Beta Kappa. She has been employed for four years at the Hillsborough Community Mental Health Center, Tampa, Florida, where she works one-half-time doing diagnostics and psychotherapy in Children's Outpatient Services and one-half-time in the Charles Mendez Day Care Center, a day school for emotionally handicapped children; this school is a joint project between the Hillsborough County Public School System and the Mental Health Center. She is a therapist to one classroom of this school and administers individual, group, and recreation therapy to the children of that class; in addition, she administers psychological evaluations to the Mendez 81 -

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82 students. She is the Hillsborough Community Mental Health Center Consultant to the Hillsborough County Head Start Program. She has been married to Ray Suarez for nine years.

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I certify that I have read this study and that in my opinion it conforms to acceptable standards of scholarly presentation and is fully adequate, in scope and quality, as a dissertation for the degree of Doctor of Philosophy. icqueFin Professor R. of Goldman, Clinical Chairman Psychology I certify that I have read this study and that in my opinion it conforms to acceptable standards of scholarly presentation and is fully adequate, in scope and quality, as a dissertation for the degree of Doctor of Philosophy. Eileen B. Fennell Assistant Professor of Clinical Psychology I certify that I have read this study and that in my opinion it conforms to acceptable standards of scholarly presentation and is fully adequate, in scope and quality, as a dissertation for the degree of Doctor of Philosophy. i± s H. John^n ciate ProYessor of Clinical Psychology I certify that I have read this study and that in my opinion it conforms to acceptable standards of scholarly presentation and is fully adequate, in scope and quality, as a dissertation for the degree of Doctor of Philosophy.

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I certify that I have read this study and that in my opinion it conforms to acceptable standards of scholarly presentation and is fully adequate, in scope and quality, as a dissertation for the degree of Doctor of Philosophy. This dissertation was submitted to the Graduate Faculty of the Department of Clinical Psychology in the College of Health Related Professions and to the Graduate Council, and was accepted as partial fulfillment of the requirements for the degree of Doctor of Philosophy. December, 1981 Assistant Professor of Statistics Dean for Graduate Studies and Research