Title: Nonlanguage cerebral mechanisms in a visual field task
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Title: Nonlanguage cerebral mechanisms in a visual field task
Physical Description: viii, 31 leaves : ill. ; 28 cm.
Language: English
Creator: Schell, Bruce John, 1943-
Publisher: s.n.
Place of Publication: Gainesville FL
Copyright Date: 1970
 Subjects
Subject: Visual discrimination   ( lcsh )
Laterality   ( lcsh )
Psychophysiology   ( lcsh )
Genre: bibliography   ( marcgt )
theses   ( marcgt )
non-fiction   ( marcgt )
 Notes
Statement of Responsibility: Bruce Schell.
Thesis: Thesis--University of Florida.
Bibliography: Bibliography: leaves 29-30.
General Note: Manuscript copy.
General Note: Vita.
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Bibliographic ID: UF00098434
Volume ID: VID00001
Source Institution: University of Florida
Holding Location: University of Florida
Rights Management: All rights reserved by the source institution and holding location.
Resource Identifier: alephbibnum - 000561589
notis - ACY7523
oclc - 13546783

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NONLANGUAGE CEREBRAL MECHANISMS

IN A VISUAL FIELD TASK











By
BRUCE J. SCHELL














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














UNIVERSITY OF FLORIDA
1970














ACKNOWLEDGMENTS


The author wishes to express his appreciation of his committee

for the people they are. Particular thanks are due to his Chairman,

Dr. Paul Satz, for whose many forms of assistance over the years, I

can never adequately acknowledge. Special thanks are also due to

Dr. Madelaine Raimey for assistance in the statistical analysis of the

data. For the author, the most significant aspect of this study was

that he was allowed to do his own "thing," with its unique rewards

and pitfalls. For this I am truly grateful to my entire committee.

I would also like to thank my parents, Mr. and Mrs. B. J. Schell

of Las Cruces, New Mexico, for the wonderful support they have given

me throughout the years.















TABLE OF CONTENTS


PAGE
ACKNOWLEDGMENTS..................................................... 1

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

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

ABSTRACT............................................................ vi

INTRODUCTION........................................ ......... ...... 1

METHOD............................................... ............... 11

RESULTS .......... .............. .............. ......... ............ 14

DISCUSSION,..... .................... ..................... ......... 20

SUMMARY................................................................. .. 25

APPENDICES

1 STIMULUS AND ERROR TYPES EXAMPLE .......................... 27
2 SUMMARY ANALYSIS OF VARIANCE................................ 28

BIBLIOGRAPHY ................. ....................................... 29

BIOGRAPHICAL SKETCH................................................ 31














LIST OF TABLES

PAGE

TABLE 1 WAN CORRECT RECALL BY VISUAL FIELDS AND FAMILIAL HANDEDNESS... 16














LIST OF FIGURES

PAGE

FIGURE 1 DISTRIBUTION OF ERROR TYPES............................. 17

FIGURE 2 PERCENT ERROR TYPES BY VISUAL FIELD ..................... 18

FIGURE 3 FAMILIAL HANDEDNESS BY ERROR TYPES...................... 19














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


NONLANGUAGE CEREBRAL MECHANISMS
IN A VISUAL FIELD TASK

By

Bruce J. Schell

June, 1970

Chairman: Paul Sats, Ph.D.
Major Department: Psychology



In recent years, considerable literature has been devoted to

laterality differences in visual perception. The basic rationale for

these experiments is twofold. First, in vision, each visual half field

(VHF) projects directly to the contralateral cerebral hemisphere.

Second, clinical studies of brain-injured adults have demonstrated a

dual functional asymmetry between the cerebral hemispheres in man,with

the left hemisphere primarily subserving speech and language function,

while the right hemisphere has been Implicated in higher integrative

nonverbal visual-spatial functions.

The demonstration and extension of these clinical findings, through

examination of VHF asymmetries in normals, hae been hampered by method-

ological inadequacies. Recently a new paradigm seemingly obviating these

methodological shortcomings has been presented in two studies by Hines.

This paradigm, Incorporating the principle of simultaneity from the









previous approaches, has departed from them in two major ways. First,

a new method to ensure macular fixation was devised. Second, a short-

term memory variable was introduced.

The present study was designed to test the efficacy of the paradigm

with a nonverbal stimulus, to investigate the type of errors made by

the Ss, and to test what effect familial sinistrality had on these factors.

Fifty-one right-handed Ss were presented block design stimuli via a

16 mm. projector. Ten of these Ss were eliminated on the basis of their
o
low performance level. The stimuli were presented 3 to the left or

right of fixation. Fixation was maintained through sequential presen-

tation and initial recall of four single digit numerals. The Ss were

then required to identify the correct block design from a five-item

multiple choice array. The array consisted of the correct choice, its

lateral mirror image (LMI), its vertical mirror image (VMI), a different

shaped design (DSD) occupying the same general area, and an unrelated

design (URD).

A significant left visual field (LVF) superiority in terms of mean

VHF differences (F1,80 4.58, p .05) and the number of Ss with an over-

all LVF superiority werefound (X 14.9, df=l, p--.001). Familial

sinistrality was found to have no significant effect on the mean VHF

differences.

The typesof errors made on missed trials were found not to.be

distributed randomly (X 2r= 17.28, df= 3, p<.001). There were more LMI

and fewer URD type errors than there were VMI or DSD types.

Significantly more URD errors were made in the right visual field

(RVF) than in the left (Zr2.03, p!.025).








Those Ss with a positive history of familial sinistrality made

significantly more VMI type errors (Z=1.86, p4.05) and significantly

less URD type errors (Z=2.02, p .025) than the other Ss.

The present findings, through demonstration of a LVF superiority

for a nonverbal stimulus, lend support to the feasibility of the use

of normal Ss to demonstrate brain laterality difference, and demonstrate

the efficacy of a new technique.

The lower incidence of URD errors in the LVF provides evidence not

only for the role of the right cerebral hemisphere in the processing

of nonverbal stimuli but also for the viability of using types of errors

to provide information about cerebral function. Thus, the lower rate

of URD type errors related to a positive history of familial sinistrality

suggests the possibility of a more diffuse cortical representation for

nonverbal function in those Ss.

While the results offer a new contribution to our knowledge of brain-

behavior relations, their primary significance relates to the viability

of these new methodologies.


vill














INTRODUCTION


The specialization of speech and language functions in the left

cerebral hemisphere in man has in recent years focused attention on the

role of other higher integrative functions which may be mediated by the

right cerebral hemisphere. Clinical studies, using heterogeneous brain-

Injured populations, have suggested that the right cerebral hemisphere

may be dominant for special visual-spatial functions (Teuber, 1962).

Unfortunately, many of these studies are fraught with methodological

problems (e.g. lesion specificity and variability, age, I. Q., and

edema effects) which tend to obscure possible brain-behavior relation-

,ships. In an attempt to control for these methodological considerations

the use of normal Ss to investigate brain-behavior relations has pro-

liferated. A principal approach has been the use of laterality differences

in visual perception as an indicant of underlying cerebral hemispheric

differences. However, the use of normal Ss has introduced new method-

ological difficulties (principally habitual directional scanning effects

and uncontrolled eye movements) which have again obscured possible brain-

behavior relationships.

If these methodological considerations do tend to obscure the

results, why bother to use the visual system? The primary advantages of

the visual modality for investigation of laterality differences lie in

the potential range of stimuli that may be investigated, the division of

each retina allowing specificity of the hemisphere to which the material is








projected, and the direct connections between the visual half fields

(via crossed and uncrossed pathways) and the contralateral cerebral

hemisphere.

The present paper shall present a rationale for a new methodological

approach to the question of right cerebral hemispheric function. This

rationale will be expurgated through a review of relevant clinical,

experimental, and theoretical papers.

Two primary methodologies have been used in the visual research.

The first, historically, was sequential tachistoscopic presentation

(Type I) of verbal and nonverbal materials in the left (LVF) and right

(RVF) visual fields. The second approach (Type II) has involved simul-

taneous presentation of disparate stimulus pairs to the visual half

fields (VHF).

The Type I approach, in which Ss attend to a fixation point with

the stimulus materials presented a few degrees of visual angle to the

left or right of the fixation, has resulted in a predominant RVF super-

iority for verbal materials (White, 1969). The primary explanation for

these findings has been that the RVF has more direct connections to the

language centers in the contralateral left hemisphere. This finding

would seemingly demonstrate, in normals, the efficacy of the technique

and the predominant role of the left hemisphere in verbal processing.

Unfortunately, the value of these results is called into question by the

failure to demonstrate a corresponding LVF superiority for nonverbal

materials. The major demonstration, within the technique, of a LVF

superiority for "nonverbal materials" was by Kimura (1966). Attempts to

replicate this finding have either failed (Kinsbourne, 1970) or been

demonstrated only under special conditions (Van Nostrand, 1970).









Indeed, it has been questioned whether the task itself, enumeration of

dots, constitutes a nonverbal task.

The Type II design, simultaneous visual half field stimulation,

was based conceptually on analagous research in audition and on results

obtained from some clinical lesion groups. The clinical studies found

that patients with lesions of, for example, the right parietal lobe,

would, under simultaneous stimulation, often fail to report the stimulus

that was going to the right hemisphere (Teuber, 1962). As these patients

were fully capable of responding to sequential stimulation it was reasoned

that in the simultaneous condition somehow the "weaker" processor falls

to respond or responds inadequately to the incoming signal. Demonstration

of the phenomenon is then dependent on a "weaker" processor and the

stimulus condition of the simultaneous presentation. This phenomenon,

the extinction effect, has been demonstrated in all sensory modalities

and is routinely used in the screening of patients for cerebral insult.

It would then be expected, if in normals there are functional differences

between the two cerebral hemispheres, that the simultaneous condition

would tend to accentuate this difference. Indeed, this was found in the

auditory research (Kimura, 1967; Satz, 1968). Simultaneous presentation

of disparate auditory information resulted in a clear cut difference in

accuracy of recall between the two ears. That is, when verbal materials

were presented simultaneously to both ears in normal right handers, a

significantly greater amount of the information that was presented to the

right ear was recalled correctly. The Kimura (1967) study further demon-

strated that when nonverbal materials (melodic patterns) were presented

simultaneously to the two ears a significantly greater amount of the

material presented to the left ear was recalled correctly. With the








application of the simultaneous technique in audition we then find clear

cut differences between the two ears (cerebral hemispheres), dependent

upon type of stimulus materials, that have not been seen with sequential

presentation (Kimura, 1967), The direct extension of the simultaneous

technique to vision was not, however, particularly fruitful in the

elucidation of underlying cerebral hemispheric differences. Almost

invariably a LVF superiority has been found for verbal materials. This

is directly counter to any central nervous system (CNS) hypothesis

(White, 1969). This predominant LVF superiority for verbal materials

has been primarily explained as due to the directional scanning effects

(Heron, 1957), selective training of the right hemiretina (Orbach, 1967),

and the intrinsic directionality of the stimulus (Orbach, 1967). Aside

from these artifactual elements producing differences between the visual

and auditory research another major difference is apparent. That is,

the auditory research typically presents three to four digit pairs per

trial thus introducing a short term memory (STM) variable that has

typically not been a factor in the visual studies.

In an attempt to control for these factors and to introduce a STM

variable, a new methodological approach (Type III) has been developed.

While incorporating the principle of simultaneity from the Type II

design, the Type III design deviates otherwise by ensuring more adequate

control of macular fixation and by including an STM component. This

approach has demonstrated, within a STM paradigm, a significant RVF

superiority for verbal stimuli (Hines et al., 1969; Hines and Sats, 1970).

Further, this RVF superiority was observed in over 80% of the right

handed Ss that were tested. It remains to be seen, however, whether this

technique is superior to the previous methodological approaches, as the









demonstration of a RVF superiority for verbal materials is but half the

task. Within this methodology a LVF superiority for nonverbal materials

must also be demonstrated before its value in exploring functional

cerebral laterality differences may be adequately assessed. The present

study is designed to test the efficacy of this new paradigm for nonverbal

materials.

From the above decision three immediate questions arise. What type

of nonverbal materials should be used? How does one measure the perform-

ance of the Ss? Is it possible within the STM paradigm to demonstrate a

LVF superiority for nonverbal stimuli? Each of these questions, of

course, rests on the separate and more general assumption that the right

cerebral hemisphere is differentially specialized for "nonverbal-spatial"

functions.

Previous experimental and clinical literature can provide some

guidelines for the type of nonverbal material used. The first criterion

as negatively demonstrated by the Kimura (1966) study, Is that other

investigators should be in agreement that the stimuli are indeed non-

verbal. The second guideline is provided by the research of Bryden and

Rainey (1963), Wyke and Ettlinger (1961), and Glanzer and Clark (1964).

The first two experiments demonstrated that the use of highly

familiar objects produces a RVF superiority. This RVF superiority is

probably due to the Ss verbally identifying the stimulus, thus producing

primarily a language mediated response for this obstensibly nonverbal

task. Clinically, Kimura (1963) has further demonstrated the importance

of the familiarity-nonfamiliarity dimension. In this study, using left

and right temporal lobectomy patients, she found inferior performance for

the right lobectomy patients (compared to the left lobectomy patients) on









an overlapping nonsense figures recognition test, while the converse was

seen on a familiar overlapping figures test. The Glanzer and Clark

(1964) study suggests further that Ss often verbally encode the visual

stimuli in "nonverbal visual memory" tasks. Therefore, the second guide-

line is that the nonverbal stimuli should be unfamiliar and not readily

accessible to verbal codification.

An appropriate type of design matching the above criteria is the

block design. Historically, block designs of varying complexity have

been used in the detection of general non-specific cerebral insult

(Satz, 1966). More recently, it has been shown that lesions invading

the right cerebral hemisphere differentially impair performance on block

design tasks (Parsons, 1970). It has also been demonstrated that

patients with split brains (callosal disconnection) are able to construct

design patterns significantly better with their left hands, presumably

because of the "dominance" of the functions in the contralateral right

hemisphere (Cazzaniga, 1967). Block designs have the advantage of

professional accord with respect to their nonverbal loading and as stimuli

represent objects low in familiarity. Technically, they provide the

additional advantage of being a standard size stimulus of which specified

manipulations may be made. How, then, using block design stimuli, can

one measure the Ss performance? Three possible alternatives would appear

to be available; recall expressed by describing the stimulus, recall

expressed by drawing the stimulus, and finally, recall demonstrated

through correct identification of the stimulus from a multiple stimulus

array. The first alternative, through measuring a verbally encoded

response, would defeat the purpose of or bring Into question the value

of the study. Requiring the Ss to draw the stimuli suffers from a









number of drawbacks, the principal ones being the introduction of a

subjective scoring element and the time consumed in drawing the stimuli.

The third alternative is preferable as it interferes least with the non-

verbal quality of the task, provides an objective scoring technique,

and allows for investigation into the types of errors made when the

correct stimulus is not identified.

Relatively uninvestigated, particularly with regard to the influence

of functional cerebral laterality differences, is the question of what

types of errors Ss make when they are wrong. That is, will different

errors be made depending on the visual field to which the stimuli are

presented? Are particular types of errors more common across visual

fields than other types? Some suggestions as to possible factors to

investigate are provided by the studies of Noble (1968), Goodnow (1969),

and Mello (1965).

Noble (1968), using primates in the Wisconsin General Test Apparatus

(WGTA), has investigated some of the possible types of errors. In this

study, optic chiasm sectioned monkeys had one eye occluded and were

trained on a two choice angular discrimination. The nonreinforced element

of the discrimination was either a lateral mirror image (LMI) or a vertical

mirror image (VMI) of the reinforced stimulus. In this condition, due to

the chlasm section, one cerebral hemisphere receives direct visual input

while the other receives visual information indirectly via the corpus

callosum. After demonstrating that the discrimination had been learned,

he then reversed which eye was occluded and, thereby, which hemisphere

received direct visual stimulation. He found that the nonrelnforced LMI

was responded to at a higher level than the previously reinforced stimulus.

Thus, the information which was transmitted via the corpus callosum during









the training trials resulted in an orientational "confusion" of the

correct stimulus during the test trials. This effect was not seen with

the VMI.

Similarly, Mello (1965) found, after training pigeons on an angular

discrimination with an opaque goggle over one eye, that upon switching

eyes the pigeon responded maximally to the LMI of the reinforced stimulus.

Goodnow (1969) and Boone and Prescott (1968) have reported in children

that discrimination of changes in the vertical direction are easier than

changes in the horizontal direction.

Finally, the misperceptionsof the LMI and VMI as the correct stim-

ulus are common errors in children learning to read (e. g. reporting or

writing b for p (VMI) or d (LMI)).

The LMI and VMI errors both represent errors of direction (orienta-

tion). That is, the shape of the stimulus is preserved, but the direct-

ionality angulationn) of the stimulus is lost. This suggests, as does

the research of Hubel (1963),that, possibly, the shape and direction of

a stimulus are dissociable elements of the total perception. Hubel (1963)

has demonstrated, in the cat, with single cell recording from the visual

cortex, that there are cells that respond maximally to the shape of the

stimulus while others respond maximally to its orientation. Thus an

additional possible error is to correctly perceive the orientation

(direction) of the stimulus and yet to have an incorrect perception of

its shape. To test for this error it is necessary to have a different

shaped design (DSD) occupying the same general area.

Two principal theories are relevant to the basic question of

whether, within this paradigm, a LVF superiority for nonverbal materials

can be demonstrated. Both theories (Kimura, 1966; Kinsbourne, 1970)









are in agreement that in normal right handers language is predominately

represented in the left cerebral hemisphere and that the right hemisphere

plays a major role in nonverbal visual-spatial tasks. Kimura's (1966)

theory further proposes that stimulus input transmitted on the most

direct pathway will better maintain the integrity of the stimulus signal

and will therefore be more efficiently processed. Her theory then

predicts, barring artifacts of technique, a LVF superiority for non-

verbal materials and a RVF superiority for verbal materials. Kinsbourne

(1970) has recently proposed an alternative model: If a subject is

engaged in language behavior, prior or during a test trial, a left hemis-

pheric activation will take place and that accompanying this will be a

directional bias to the RVF regardless of the nature of the stimulus

input (e. g. verbal or nonverbal). "Such orientation will characterize

not only overt language use, but also covert (subvocal) language behav-

ior, including the state of expectancy to verbal response." His theory

thus predicts that, as long as the left cerebral hemisphere is activated

by any language behavior, verbal and nonverbal materials will be more

accurately responded to when they are in the RVF.

An additional separate variable relevant to the basic assumption

that the right cerebral hemisphere is "dominant" for nonverbal functions

is the possibility of differences in the degree of cerebral lateralis-

ation of function in the Ss.

Clinical studies by Subirana (1958) and Zangwill (1960) have found,

following cerebral insult, a more rapid remission of aphasia in right-

handed patients with left-handed relatives. This finding suggests the

possibility of a more diffuse representation of cortical function in

those right-handed subjects with a positive family history (+FH) of left-





10


handedness. Indeed, Hines and Satz (1970) have demonstrated, using the

Type III design with verbal materials, a difference in VHF performance

between those Ss with a +FH of left-handedness and those Ss with a

negative family history (-FH) of it. This difference, an attenuation in

the RVF asymmetry (i. e. superiority) in +FH Ss, is suggestive of a

difference in degree of cerebral lateralization. A preliminary investi-

gation of the influence of this factor on nonverbal materials will be

included in this research.

The present experiment is designed to investigate the following

questions. Will recall accuracy for nonverbal materials be influenced

by the VHF to which the stimulus is presented? Are some type errors

more common than other error types? Will right-handers with a +FH of

left-handedness perform differently than right-handers with a -FH of

left-handedness? That is, will the +FH Ss perform differently in regard

to either VHF asymmetry or types of errors made?















METHOD


Subjects

Fifty-one right-handed Ss from introductory Psychology classes

were used. The ages of the Ss ranged from 17 to 30 years with a mean

age of 20.14 years. No Ss were used whose visual acuity was not at

least 20/40 or who had a discrepancy of more than 1/2 minute of visual

arc between the eyes. Visual acuity was established through use of a

Snellen Eye Chart.

Materials

The stimuli vere presented via a 16 i.s. Kodak Analyst Projector

onto a rear-view screen. The stimuli were presented at about eye level,

All Ss had their heads positioned on a commercial chin rest. The test

film was administered in a dimly illuminated room with a single light

source directly behind the projector.

Procedure

All Ss were given a self-administered handedness questionnaire.

They were then screened for visual acuity and finally viewed the test

film.

The test stimuli consisted of 56 trials with 4 numbers and 1 block

design per trial. These numbers were the single digits O through 9.

No number appeared more than once in a trial. At the beginning of each

trial a central fixation point appeared for 605 msec. followed sequen-

tially by the 4 digits at fixation with the block design appearing









either to the left or right of the fixation digits. The exposure time

for each digit was 182 msec. (no interstimulus interval). The block

design was projected 30 from the fixation numerals for a total exposure

time of 606 msec. Each digit subtended approximately 45' of visual area

in height and 30' in width. The block design subtended approximately

90' of visual area in height and 60' in width. The first digit of the

sequence preceded the onset of the block design by 60.6 msec. with the

last digit remaining on the screen 60.6 msec. after the block design

was no longer present. This was done to insure initial fixation and to

reduce shift in fixation from the last digit over to the block design.

A between trials interval of 10 seconds was used, during which the Ss

reported the digits from the preceding trial (fixation control) and

then identified the design (dependent variable) from a 5 item multiple

choice array. The 5 item multiple choice array consisted of the

correct choice, its lateral mirror image (LNI), its vertical mirror

image (Vil), a different shaped design (DSD) occupying the sare general
1
area, and an unrelated design.

The first 12 trials were practice and included 6 trials in which

the block design was in the LVF and 6 in the RVF. Of the remaining 44

trials, 10 were not included in the investigation of error types as it

was not possible to -abk all the error types for those designs. There

were 5 of these trials in each visual field.

If, on any trial, the center fixation digits were not reported

correctly, the identification of the design was not subsequently counted.

The s were told to respond to every trial whether or not they knew the

See Appendix 1 for example.





13


correct response. A criterion of 23% correct (3% above chance) was

chosen for inclusion in the study. Ten Ss were eliminated on this

criterion. With the exception of their poor performance, they were

not distinguishable from the other Ss.

Design Rationale

This paradigm, developed by Hines et al. (1969) and modified for

this study, provides two major advantages over the previous approaches.

(1) It insures fixation which the Type I and Type II designs could not

adequately provide. (2) It utilizes STM processes which, in audition,

have uncovered the most striking asymmetries. Finally, this modification

offers a direct and timely test of Kinsbourne's (1970) model which

predicts that verbal processing during or before a test trial will result

in a directional bias to the RVF.
















RESULTS


Recall by Visual Half Field

These analyses represent the major test of the present thesis. The

first was concerned with the magnitude of the mean differences between

the RVF and LVF. The second dealt with the directional frequency diff-

erences in recall between the VHFs among the Ss. The mean correct recall

for designs in the RVF and LVF is presented in Table 1. An Analysis of

Variance (liner, 1962) based on the combined group of Ss revealed a
1
significant LVF superiority (F71,0= 4.58, p .05). The designs in the

LVF were reported correct more often than those from the RVF in 33 of the

41 Ss. This frequency difference was significant (X= 14.9, df= 1, p.001).

VHF Recall by Family History

Inspection of Table 1 reveals that family history of left-handedness

had no significant effect on the mean VHF differences.

VHF by Error Types

The following analyses were computed to see if error types were

distributed randomly and if presentation of the stimulus to a particular

VHF produced a difference in the relative incidence of the error types.

Figure 1 presents a breakdown of types of errors made on missed trials.

A Friedman Analysis (Hays, 1965) of the data revealed that the error
2
types were not distributed randomly (Xr= 17.28, df=3, p .001).

SSee Appendix 2 for Summary Analysis of Variance.









Inspection of the figure reveals there were more LMI and fewer URD errors

than there were VMI or DSD type errors.

The effect on error types of the VHF to which the design is presented

is shown in Figure 2. The significance of the differences between the

VHFs for the LKI errors and the URD errors was tested with the Wilcoxen

Test for Matched Samples (Hays, 1965). The results of the first analysis

for the LMI error typewere nonsignificant (Z=.45, p-.33). The differ-

ence between the VHFs for the URD error type was significant,

(Z=2.03, p!.025).

Error Types by Family History

The difference in error types made by +FH Ss and -FH Ss is presented

in Figure 3. The difference in incidence of VMI error types and URD

error types between the two groups of Ss was examined with the Mann-

Whitney Test (Hays, 1965). The VMI error was found to occur significantly

more often in the +FH Ss than in the -FH Ss (Z= 1.86, pC .05). The URD

error occurred significantly less frequently in the +FH Ss than in the

-FH Ss (Z=2.02, p .025).






















TABLE 1

Mean Correct Recall by Visual
Fields and Familial Handedness


Left Field Right Field

-FH (n 32) 13.06 (59.36%) 11.28 (51.27%)

+FH (n 9 ) 13.55 (61.59%) 11.66 (53% )





















FIGURE I


Distribution of Error Types



32

30 -

28

426

S24
S22

' 20
18

16

14 -
12


LMI VMI DSD URD
















FIGURE 2


Percent Error Types by Visual Field





38

36

34

32

30

28

26 A

24

22

20

18

16

14


12.


LMI V.I DSD URD
Error Types
Right Field=---N=41, Trials Rated 295
Left Field ----- N=41, Trials Rated 272

















FIGURE 3



Familial Handedness by Error Types


LMI VMI DSD URD
Error Types
+FH= -- N=9, Trials Rated 123
-FH=-- - N=32, Trials Rated 444


\1















DISCUSSION


The present findings confirmed the hypothesis that recognition of

nonverbal visual designs is facilitated by side of VHF input. Visual

designs presented to the left VF were more accurately recognized than

those presented to the right VF. This directional asymmetry, moreover,

was observed in over 80% of the Ss. The fact that a reversal in the VHF

asymmetry has been long reported for verbal stimuli (Kimura, 1966)

strongly suggests that brain laterality mechanisms probably underlie the

VHF asymmetry. This superior recognition for design patterns presented

to the left VF suggests that the right cerebral hemisphere may be differ-

entially specialized for processing visual-spatial information. Clinical

studies on brain injured patients have already suggested this possibility

(Milner, 1967).

This experiment, with the presentation during the test trials of

the fixation digits, would appear to have been an ideal test of

Kinsbourne's (1970) theory of VF asymmetries. His theory predicts a RVF

superiority regardless of the nature of the VHF stimuli (verbal or non-

verbal) whenever the subject is engaged in verbal activity concurrent

with or immediately preceding the test trial. The LVF superiority seen

in this study would then appear to disconfirm Kinsbourne's theory at








least in its present form. It is, of course, possible that in the

absence of adequate control of central fixation, Kinsbourne's theory

would be maintained. A review of the evidence offered by Kinsbourne

suggests that indeed this may be the case.

The failure to find a statistically significant difference, in

terms of VHF recall, between those Ss with a +FH and those with a -FH,

is at variance with the Hines and Satz (1970) study. That study, using

the Type III design with verbal materials, found a decreasing difference

between the two groups as the difficulty level of the task increased. At

the speed of 177 msec. per digit pair they found no difference between

the groups. It may be that the difficulty level, for nonverbal materials,

in this study was similar to that of the Hines and Sate (1970) study with

verbal material at its faster speeds. Alternatively, it may be that

the influence of familial sinistrality upon cerebral lateralization of

nonverbal function is more subtlely felt than are differences in degree

of language lateralization. Consonant with this hypothesis is the

difference in types of errors made by the two groups. A significantly

lower incidence of URD errors among the +FH as compared to the -FH group

is suggestive of the possibility of a more diffuse representation for

nonverbal function in the +FH group. That is, the URD error is the only

error that has no relationship to the original stimulus. Thus, when

that error was committed no portion of the stimulus gestalt was utilized.

This implies that the +FH group was able to utilize more consistently

at least a portion of the stimulus gestalt. The greater incidence of VMI

errors in the +FH group suggests that the more diffuse representation

seen in this group is primarily related to some "recognition of shape"

function rather than a directional or orientational factor.









The finding that the LMl error was the preferred error for all Ss

supports the infrahuman research findings of Noble (1968) and Mello (1965).

The demonstration, within this study, of a higher rate of LMI type errors

does not represent a new discovery about humans. This, however, is the

first study of types of errors made within the visual field research.

The mechansim predisposing species ranging from humans to pigeons for

this type error remains obscure. Speculatively, it is as if the synaptic

signal for direction in the vertical dimension is somehow "weaker" or

more tenuously linked to the total. Ve do know that in ontology

discrimination in the vertical dimension is slower to develop and more

difficulties are experienced with this dimension than with the horizontal

dimension (Boone and Prescott, 1968). The lower incidence of URD errors,

the error with no relationship to the stimulus, emphasizes that Ss,

even when they do not correctly identify the stimulus, still have pro-

cessed part of the stimulus gestalt. That is, if the Ss had no inform-

ation about the stimulus, then the rate of response to the URD error

should have been the same as that of the DSD and VMI type error.

This study represents the first investigation of the influence of

the VHF upon types of errors made. The significantly lower incidence

of URD errors in the LVF thus provides evidence not only for the role

of the right cerebral hemisphere in the processing of nonverbal stimuli

but also for the viability of using types of errors to provide infor-

mation about cerebral function. Thus, even in the absence of a demon-

strable LVF superiority for block designs, this evidence, that the Ss

were able to utilize more of the stimulus information from the LVF,

would have, alone, been indicative of the predominant role of the right

hemisphere in nonverbal function.









This study, representing the fruition of several years of collab-

orative research, has demonstrated two new methodological breakthroughs

in the investigation of cerebral laterality differences. While the

results offer a new contribution to our knowledge of brain-behavior

relations, their primary significance relates to the viability of

these new methodologies. Thus, while the demonstration of a LVF super-

iority for a nonverbal stimulus represents the first unequivocal visual

research showing the unique functional specialization of the right

hemisphere in processing nonverbal stimuli in normal adults, its value

is overshadowed by the potential contribution that this paradigm (Type III)

offers in the study of cerebral mechanisms In perception. Similarly,

the new information about brain function garnered through investigation

of the types of perceptual errors has less significance as new data then

it does as a demonstration of the feasibility of this approach to the

question of cerebral laterality.

The potential extentlons of these techniques to the investigation

of cerebral laterality differences in normals are myriad. For example,

through examination of the types of errors it would be possible to

investigate the relative contribution of the orientation and shape of

the stimulus to the gestalt and to assess the relative contribution

of these two factors depending on the VHF in which the stimulus is

presented. We have completed a preliminary investigation, using the

Type III design with normal right-handed Ss, that demonstrated, in a

single experiment, a dissociation between the VHFs for verbal and non-

verbal stimuli between Ss. Currently we are attempting to demonstrate

this VHF dissociation for verbal and nonverbal materials within Ss and

to investigate the relative influence of varying degrees of left-and






24


right-handedness on VHF performance. The role of familial history of

left-handedness on performance is also being investigated in the current

study. Projected future studies involve variations in the stimulus

input and extension into new modalities.

The Type III design is, at present, the only approach with normal

right-handed Ss in which a RVF superiority for verbal materials

(iines et. al., 1969) and a LVF superiority for nonverbal materials has

been reliably demonstrated. These findings are thus consonant with

empirical findings on hemispheric asymmetry in brain injured patients.

The major factors unique to this design and, thus, probably responsible

for the results, involved control of macular fixation, the introduction

of a short term memory variable, and the fact that the experimental

conditions were more analogous to a sensory overload situation than

to a sensory threshold situation with its possible peripheral sensitivity

factors.















S tLMARY


The present study investigated, through the use of two new method-

ologies, VHF recall and error differences to block design stimuli.

Fifty-one right-handed Ss were tested, of which 10 fell below a 23%

cutoff point (3% above chance) and were eliminated. These Ss did not

fall into any definable group. The block designs were presented, via

a 16mm. projector, 30 to the left or right of fixation. Fixation was

maintained through sequential presentation and initial recall of 4

single digit numerals. The Ss were then required to identify the correct

block design fronw a 5 item multiple choice array. A significant LVF

superiority was observed. This finding casts doubt on Kinsbourne's

activation theory of VHF asynnmetries.

The types of errors made by the Ss were also analyzed. This

analysis revealed that the majority of errors represented reversal

orientations of the original stimuli. Further analysis of the error

types revealed an effect attributable to the VHF to which the stimulus

was presented and an effect due to familial history of left-handedness.

Famillal history of left-hendedness was found to have no effect on the

recall scores of the Ss.

The significance of these methodologies for the assessment of

cerebral laterality mechanisms was discussed.















APPENDICES



























APPENDIX 1




STIMULUS AND ERROR TYPES EXAMPLE


VMI DSD


Sti mlus LMI


URD
















APPENDIX 2


SUiMARY ANALYSIS OF VARIANCE


Source SS df ms F

Yethod 66 1 66 4.58*

Error 1152 80 14.4

Total 1218 81
* p .05















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BIOGRAPHICAL SKETCH


Bruce John Schell was born August 6, 1943, in El Paso, Texas.

He graduated from Las Cruces High School In Las Cruces, New Mexico,

in June, 1961. He obtained a Bachelor of Arts degree, majoring in

Psychology, in June, 1966, from New Mexico State University. In June,

1968, he received a Master of Arts degree, with a major in Clinical

Psychology, from the University of Florida.

Bruce Schell is married to the former Marcy Myers and has one

son, Eric Kendall.















This dissertation was prepared under the direction of the chairman

of the candidate's supervisory committee and has been approved by all

members of that committee. It was submitted to the Dean of the College

of Arts and Sciences and to the Graduate Council, and was approved as

partial fulfillment of the requirements for the degree of Doctor of

Philosophy.

June, 1970





Dean, College of Art and Sciences





Dean, Graduate School

Supervisory Committee:





Chalan




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