Title: Double dissociation: asymmetry in visual half field recall superiority as a function of type of stimulus materials
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Title: Double dissociation: asymmetry in visual half field recall superiority as a function of type of stimulus materials
Physical Description: ix, 103 leaves : illus ; 28 cm.
Language: English
Creator: Clementino, Antonio Francis
Publication Date: 1973
Copyright Date: 1973
 Subjects
Subject: Visual perception   ( lcsh )
Cerebral dominance   ( lcsh )
Psychology thesis Ph. D   ( lcsh )
Dissertations, Academic -- Psychology -- UF   ( lcsh )
Genre: bibliography   ( marcgt )
non-fiction   ( marcgt )
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Thesis: Thesis--University of Florida.
Bibliography: Bibliography: leaves 89-102.
General Note: Typescript.
General Note: Vita.
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Bibliographic ID: UF00098369
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 - 000585208
oclc - 14199551
notis - ADB3840

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DiOUBLjE DI~SSOI~ZiAT'ION : ASYMMETRY IN
VISUAL HAlF~ F;IEiLD RETCALL SUIPER\IORITY
AS A FUN~CTIONI OF 'TYP'E O1F STIMULUS MATERIAL





Byv



Antonio Francis Clementino


A: Dissertation P'resented to th~e Graduate Council
of the UniverTsity of Florida
in Partial Fulfllmecnt of the Reauirements for the
Degree of Doctor of Philosophy



UNIVERSITY OF FLORIDA


1973







































UN I VERSITYI OFI FLORIDA 111 11 1111111111 111














ACKNOWLEDGEMENTS


In retrospect, the course through graduate studies has

been filled with people who made -a difference--some the

difference in professional preparation, some the difference

in personal growth, and some delightfully in both. Among
the most 'important is Paul, whose guidance, aid, frustration,

protection, push, laughter, anger and love made the comple-~
tion of this dissertation and graduate studies possible in

a form wce could both live with well. Thanks also go to

Dave, whose friendship and guidance made this research oper-
ational.. Thanks also to Annie, Tom, Mark, R.J., Carol,

Vicki, Shannon, Sid, Harry, Sharon, Kerry,.Mae and Val,

John, Earl, Soren, Vince, Teillard, Hugh, Reilly, Eileen,

Fritz, Pat, Vern, Bill, Chuck, Lou, Jan, Bernie, Jerry, and

many other persons without whom I might never have under-

stood the pushes, disappointments, pain and love in the

years of graduate studies. Without them I would be less,
with them I am more. And, taking them with me perhaps I

can be more for other persons. That will be for all of us

gladly. Yes.


















TABLE OF CONTENTS


Page


ACKNOWLEDGEMENTS.....

LIST OF TABLES......

LIST OF FIGURES ......

ABSTRACT .........

INTRODUCTION .......


. . . * V

. . * * * vi

. . . . . 1


VISUAL HALF FIELD STUDIES........

METHOD . . . . . . *

RESULTS . . . . . * *

DISCUSSION . . . . . *

APPENDIX

1 VERBAL STIMULI IN VHF AND AT
FIXATION, STUDY I AND STUDY III

2 NON-VERBAL DESIGN.RECOGNITION
DISPLAY, STUDY II, EXPERIMENT 1

3 NON-VERBAL DESIGN RECOGNITION
DISPLAY, STUDY II, EXPERIMENT 2,
AND STUDY III .........

4- NON-VERBAL DESIGN AND FIXATION
DIGIT ANSWER SHEET .......

BIBLIOGRAPHY ..............

BIOGRAPHICAL SKETCH ...........


80


83




85


87

89

103


. . .


. . .




. . .


. . .


. . .


iii















LIST OF TABLES


Table Page

1 VHF Mean Correct Responses and Fre~-
quency of Right VHF Superiority for
Verbal Stimuli at Three Presentation
Times 43

2 Mean Correct Recall for Letters and
VHF by Serial Position .. .. . . 46

3 Mean Recall for Non-verbal Designs
at Fixation .. .. .. . .... 48

4 Mean Correct Responses for Non-verbal
Design Stimuli by VHF at Two Presen-
tation Times with Digits at Fixation ... 50

5 Analysis of Variance of Letter Recall
.and Non-verbal Design' Recall by VHF ... 52

6 Chi Square Relationship; Between
Verbal and Non-verbal Stimuli and
Frequency of VHF ,Superiority ...... 54

7 Stearman Rank Order Correlations
Between VH~F Performances with Verbal
and Non-verbal Stimuli ......... 54

8 Mean Recall of Serial Position by
VHF for Non-verbal Design Stimuli .. 56

9 Mean Recall of Serial Position by
VHF for Verbal Letter Stimuli ...... 59

10 Analysis of Errors of Report at
Fixation by Material and Field
of Presentation ............. 61















LIST OF FIGURES


Page


45

57


Figure

1 Mean correct response scores by VHF
at three presentation times .......

2 Mean correct stimuli recall .......









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

DOUBLE DISSOCIATION: ASYMMETRY IN
VISUAL HALF FIELD RECALL SUPERIORITY
AS A FUNCTION OF TYPE OF STIMULUS MATERIAL


By
Antonio Francis Clementino

August, 1973

Chairman: Paul Satz
Major Department: Psychology


Considerable research with normal Ss has sought to

investigate hemispheric mechanisms underlying the asym-

metries in higher cortical functioning that appear in clini-

cal studies of unilateral brain injury in humans. Experi-

mental ~studies within the visual modality have been the

most numrerours,primarily as a function of the expectation

that the unique visual neuro-anatomical structure and the

use of lateral stimuli presentation in the visual half

fields (V~HF) would permit selective testing of inferences

about normal cortical asymmetry. Recent studies have devel-

oped a short-term memory (STM) paradigm which overcomes many

of the procedural and methodological limitations of earlier

paradigmns.

Using this STM paradigm, the present research presents

three major studies: First (Study I), the development of a

new verbal task. This development involves separate efforts:




~7L':


a) a change in the nature of the presentation stimuli pre-
viously employed (i.e., digits to letters); b) an increase
in the number of stimuli at fixation and in the VHF, making

the task.more analogous~ to the p~ichotic Listening Test;

c) an assessment of the effects of rate of presentation

upon the VHF asymmetry; and d) an assessment of serial order
effects. Second (Study II), thi~e development of a non-verbal

recall analogue of the STM verbal paradigm (Study I). This

development involves: a) generating a set of non-verbal

design stimuli; b) an assessment of recognition parameters
of these non-verbal design stimuli with serial presentation;

c) an assessment of the effects of rate of presentation upon
th-e VHF asymmetry for non-~verbal designs;I and d) the asse~ss-
ment of serial order effects. The third major study (Study

III) involved the- utilization of the procedures developed in
Study I and Stud r II with a new group of Ss to determined

whether VHF performance (within Ss) varied as a function of

the type of stimulus material (verbal and non-verbal).
Results from Study I confirm the previously reported

right visual half field (RVHF) recall superiority on this
STM task with verbal stimuli. Further, Study I, with fixed

order of report, demonstrates a significant serial position
effect and extends the previous findings to letter stimuli

with increased demands upon recall. Results from Study II

suggest more difficulty in the processing of the unfamiliar
non-verbal desi-gn stimuli in immediate serial presentation


vii









than in the processing of the verbal stimuli (letters) pre-

sented in the same manner. Development of an appropriate

non-verbal STM task needed to take this increased difficulty

into account.

The major test of hemispheric mechanisms underlying

performance on the VHF tasks was demonstrated in Study III.

Results showed a consistent double dissociation: asymmetries

in the VHF performance varied as a function of the type of

stimulus materials. Verbal stimuli (letters) presented to

the RVIHF were recalled significantly better than from the

LVHF and, conversely, non-verbal stimuli (;designs) were

significantly better recognized when presented to the LVHF
than to the RVHF.' Both types of stimuli exhibit significant

serial position effects in the asymmetries produced.
Results are discussed in terms of hypotheses o-f ftunc-

tional cortical asymmetry in man and appear to offer- strong

evidence from normal Ss of the cortical asymmetry hypothesized

initially on the basis of clinical patient data.

This present research is the first STM study with con-

trolled fixation to demonstrate differences in VHF recall

superiority as a function of the type of stimulus material.

Replication (verbal stimuli) and extension (non-verbal
stimuli) of the STM paradigm makes a particular methodologi-

cal contribution in that this paradigm has previously been

shown to correlate with the Dichotic Listening T~est whereas

previous paradigms (tachistoscopic studies) have not. The


viii









present data suggest thiat this STM controlled fixation para-

digm may yield a sensitive behavioral index of functional
hemis heric differences in normal human Ss.













INTRODUCTION


Lateralization is a phenomenonuniquely demonstrated

in man and expressed most dramatically in the asymmetrical

specialization of manual skills (handedness) and the more

complex cognitive speech and language skills. This func-
tional .asymmetry has no clear phy~logenetic precedent. Thus,

the development of language representation in the left hemi-

sphere in man appears to have altered the functional equiv-
alence of the two temporal lobes seen in infrahuman species

(Milner, 1962). Further, this striking functional asymmetry
has not been clearly correlated with underlying morphologi-
cal differentiation. Minor structural hemispheric differ-

ences, particularly in the left hemisphere, have recently
been demonstrated (Geschwind and Levitsky, 1968), but these

differences are small when compared to the evidence of func-

tional differences following unilateral damage to the cere-.

bral hemispheres.

Clinico-pathological studies (experiments in nature,
electro-cortical stimulation, hemispheric brain surgery,

brain bisection studies, etc.) have each provided various

methodological approaches to the understanding of this

phenomenonof hemispheric functional lateralization in man.








Taken together, data from these varied clinical studies of

brain injured adults have primarily demonstrated a dual
functional asymmetry between the cerebral hemispheres in

man: the left hemisphere has been long known to subserve

speech and language functions and,more recently,the right
hemisphere has been shown to subserve higher spatial con-

figural functions (Milner, 1968).

Left Hemisphere
Virtually all the currently recognized symptoms of

language deficits were described prior to the nineteenth
century (Benton, 1964). However, it was the interest and

controversy over the mechanisms of organic language dis-
orders (H~caen and Dubois, 1969) which established a recep-

tive Zeitgeist for Broca's 1861 presentation of evidence for
the localization of motor aphasia. With the studies of

Broca, Dax, Wernicke, and their contemporaries, the consis-
tent occurrence of aphasic symptoms subsequent to left hemi-

spheric damage became the clinical basis for the traditional
concept of cerebral dominance (Lenneberg, 1967). Within a
few decades of Broca's first studies, specified patterns of

language dysfunction began to be reliably associated with
specific areas within the language hemisphere. Wernicke
in 1874, for example, described a syndrome associated with
lesions of the first temporal gyrus which produced distur-

bances in the comprehension of language while expressive

vocabulary and verbal fluency remained uninterrupted.








Broca in 1861 had earlier described a syndrome associated

with the posterior part..of the inferior frontal convolution

in -which patients understood language but whose verbal ex-

pression was markedly impaired and non-fluent. These frontal
lobe lesions, in contrast to the posterior temporal lobe

lesions, also produced hemiparesis to the contralateral body
side.

These hemispheric and intrahemispheric effects on lan-

guage skills provided considerable support for the selective
differentiation of the left cerebral hemisphere in man

(Palmer, 1964).
More recent clinical studies continue to validate this

asymmetry of language skills. For example, recent evidence
with right-handed patients. with anatomically verified

lesions has offered strong support for the earlier clinical

observations in showing a significant incidence of impair-

ment on four categories of verbal behavior (verbal compre-

hension, expressive language form, expressive language con-

tent, and naming) subsequent to left hemisphere lesions.
In contrast, dextrals with lesions of the right hemisphere

showed no aphasic symptoms (Gloning, Gloning, Haub and

Quatember, 1969). This finding is remarkably consistent
with earlier clinical reports of aphasic symptoms associated

with only one percent of right hemisphere lesions in right-

handers (Zangwill, 1960).








The predominance of language representation in the
left hemisphere has been buttressed by recent developments

in human brain bisection research (Sperry, 1964). While

able to attach noun labels to pictures and objects, the

surgically isolated right hemisphere of dextrals is unable
to relate subject to object via a verb, to respond to verb

commands, or to comprehend the semantic aspects of verbs

(Gazzaniga and Hillyard, 1971). Like Geschwind and Kaplan's

(1962) report of the human disconnection syndrome, afferent
verbal stimuli are linguistically uninterpretable when pre-

sented primarily to the right hemisphere and isolated from

the dominant language hemisphere by collosal sectioning.


Right Hemisphere
The early fascination with language dysfunction focused

primary, if not complete, attention to the left cerebral
hemisphere. Only in the last decade have lesion studies

demonstrated that the right hemisphere is neither non-

dominant nor silent, as often presumed. The selective

occurrence of visuo-spatial constructive deficits (Milner,

1960) following unilateral right hemisphere lesions has

suggested that the right hemisphere subserves a number of

higher cortical functions and plays a non-subordinate role
in the processing of non-verbal spatial information (Piercy,

Hdcaen and de.Ajuriaquerra, 1960; Patterson and Zangwill,

19$44 Kimura, 1963a;Warrington, James and Kinsbourne, 1966;

De Renzi,Faglioni and Scotti, 1968; Luria, 1966). Right








hemisphere lesions have been associated. with, deficits in

visual and tactile patterning (Milner, 196~4), perceptual

closure (Lansdell, 1969), visual memory for faces and

delayed recall of geometric figures (Milher, 1960), melodic
memory (Kimura, 1963,1964), complex pattern visual discrimi-

nation (Kimura, 1966), propriocepti~ve maze learning (Corkin,

1965) and reversible operations: in space (Butters, Barton

and Brody, 1970). These deficits do not appear to be a

function of type of cortical insult and have been observed

after surgical ablation, electrical stimulation, and after

cortical lesions regardless of type (i.e., neoplastic,

trauma, vascular, etc.). The localization of specific

skills within the right hemisphere h~as been less clear and

has raised the possibility that ~spatial skills may be more

diffusely represented (Kimura, 1963a;Kimura and Milner,

1964). However, recent clinical evidence suggests some

clear intrahemispheric differences. For example, perfor-

mance of right parital lobe lesion patients has been sh~own~

to be significantly inferior to all other right heinispherice

patients on a non-verbal spatial task. Matched left hemi-

sphere lesion patients with intact right hemispheres per-
formed not dissimilarly from normal controls (warrington

and James, 1967a).

The primary lateralization of spatial configural skill
has also recently been shown with commissurotomized patients,

who demonstrated an asymmetry of performance on a spatial





6_:: .


configural task consistent with patients with lateralized
lesions (Milnbr and Taylor, 1972). On a tactile-tactile

matching task, patients using their left hand (thereby send-

ing primary somatosensory input to the right hemisphere)
achieved correct matching even with experimental delay.

Alternatively, with the right hand (with the primary con-

tralateral projections isolated from the right hemisphere

by the collosal lesions), most patients were unable to per-
form the tactile-tactile matching even with zero delay.

All patients made fewer errors with the left hand in five
different intratrial delay conditions than with the right

hand in the zer1o delay conditions alone. The one commissu-

rotomized patient with a right hemisphere lesion performed

least well, suggesting that both the primary lateralization

of spatial functioning and the locus of the right hemisphere
lesion were .reflected in this inferior performance.

This lateralization of spatial configural skill within

the right hemishere does not appear limited to any one

modality. On the~ contrary, observations of visual (Kimura,

1963), auditory (imiura, 1963,1964) and tactile (Carmon and
Benton, 1969; Dee and .Benton, 1970; Fontenot and Benton,

1971) deficits subsequent to right hemisphere insult, and
i-n the absence .of contralateral tactile and motor deficits

(Dee and Benton, 1970; Semmes, 1965), support the hypothesis
of a supramodal general spatial factor (Semmes, 1965; Carmon
and Benton, 1969) which may be primarily subserved by the

right hemisphere.








Yet while lesion studies have generated considerable

support for the concept of specific right hemisphere func-
tions, this lateralization is less -clear than that of the

left hemisphere for language functions. In particular,
some evidence exists of spatial configural deficits associ-

ated not only with right hemisphere lesions but also associ-

ated with more posterior left hemisphere lesions (Semmes,

1965). Controversy still exists concerning the degree of
visuo-spatial constructive skill (Milner, 1962) subserved

by hemispheric specialization, i.e., laterality (De Renzi,

Faglioni and Scotti, 1968; Semmes, 1965; Dee and Benton,
1970). Part of the problem in understanding these results
has been the numerous sampling difficulties presented with

this subject population. Human clinical investigations,

for example, are typically based on brain injured individuals

wvho may vary in I.Q., age, education, type of lesion, locus

of l.esion, durration of lesion, etc. To control for these

many possible sources of variance can be extremely difficult.

Yet, failure to do so can severely limit the interpretation

and generalization of data from these studies. Fortunately,

many of these sources of variance are idiosyncratic to
brain damaged patients.
As a consequence of sampling problems within patient

populations, considerable recent effort has been addressed
to the development of techniques with which to investigate

brain behavior relationships with normal Ss. Again, most









of the procedural developments have been directed to the

assessment of how the left hemisphere processes verbal or

linguistic information. In recent years, considerable
laboratory effort has been addressed to the development of

special techniques to assess or tease out possible hemi-

sphieric differences ini normal Ss. Procedures have been
developed to investigate higher hemispheric processing
mechanisms in audition, somathesis, and vision.


Auditory Studies
In audition the techniyue.of simultaneous stimulation

(Broadbent, 1954) has bkeen utilized as a means of investi-

gating functional, hemispheric asymmetries in response to

linguistic and non-linguistic input. In this paradigm, Ss
are Dresented with a series of different stimuli to each

ear simultaneously (via stereo headphones) and are asked
for recall after each trial. On this Dichotic Listening

Test, Ss have ~consistently demonstrated a right ear superi-

ority of recall for verbal material (Kimura, 1961a,1967;

Sat'z, .Ach~enback, Pattishall and Fennell, 1965; Shankweiler
and Studdert-Kennedy, 1967). This recall asymmetry appears

independent of a variety of procedural and methodological
variables and appears to result from both the more efficient

contralateral pathways (Rosenzweig, 1951; Sparrow, Kanp,~

King and Roberts, 1968; Tunturi, 1946; Hall and Goldstein,
1968) and from the suppression of competing information
from ipsilateral ear input (Kimura, 1967). More recent








data suggest this asymmetry also results from the oral

report disadvantage of left ear .information that arrives
in the left hemisphere after coursing to the right hemi-

sphere and then via a transc~ollosal pathway back across to
the left auditory association area (Sparks, Goodglass, and

Nickel, 1970). Increased similarity in the dichotic mes-

sages increases the degree of competition which, in turn,
increases the magnitude of the ear asymmetry. With the

increased competition, the more direct contralateral sig-

nals to the left hemisphere: appear to be processed more

readily and the ipsilateral left ear verbal signals (both
those direct to.the left cortex and those via transcollosal

pathways) are attenuated anrd .processed less effectively by
the left hemisphere (Schwartz, 1970). Further, increased

asymmetry appears to be a function of increased short-term
memory debands (Satz, 1967;~ Goodglass and Peck, 1972).
The :Dichotic' Listeningt paradigm has been primarily

developed with:8 A focus on the processing of verbal informa-
tion. Consequently, there are considerably fewer non-

verbal auditory studies. Kimura (1964) and Shankweiler

(1966) demons-trated a dissociative left ear recall superi-
ority for non-verbal melodic patterns presented dichotically.
Both the sounds (Studdert-Kennedy and Shankweiler, 1970)

and the auditory sequences (Zurif and Sait, 1970), which

appear less.easily decodable into phonological features,
exhibit either a reduced right ear asymmetry or a left ear





10f



preference. In other words, as sounds become less lin-

guistically decodeable,there is a shift away from the right
ear advantage in the direction of increased left ear superi-

ority.. With within Ss control, Curry (1967) found a similar
shift with Ss who recalled more dichotically presented

words from the right ear and more accurate identification
of non-verbal sounds from the left ear.

Tactile Studies

Ex erimental tactile studies with normal ~Ss have only

recently been used as an alternativJe modality within which

to assess functional asymmetry in the processing of differ-

ent types of informational stimuli. For example, Hermelin

and O)'Conner (1971) recently instructed blind children and

adultsnyith no primary tactile deficits to read Braille

letters- vertically. More efficient reading and signifi-

cantly fewer errors were made .using the left hand, the hand

difference being even-more marked by performance with the

unpracticed middle finger. Some of the blind children wlho
were fluent when reading with their left hands displayed

the peculiar manifestation of being able to only produce

gibberish when reading with their right hands. The finding
of a bi.as toward left-handed Braille reading (Hermelin and

O'Conner, 1971) was felt to result from the initial primary

need to.process the tacile Braille input spatially (right

hemisphere) prior to verbal labeling, and therefore in

part this study presents results consistent with a hypothesis









of increased lateral specialization of tactile spatial

processing in the right. hemisphere (Kimura, 1966). This
inference is consistent with the demonstration that patients

with split brains (collosal disconnections) are able to con-

struct design patterns significantly better with their left

hands, presumably because of the "dominance" of spatial

analyzers in the contralateral right hemisphere (Gazzaniga,

1970).
Studies within the auditory and somasthetic modalities

with normal Ss thus provide additional support for the

results of brain injured patients: that the left hemisphere

subserves the major acoustic' and language analyzers for

verbal reception and expression and that the right hemisphere

subserves a primary, but less clearly lateralized,role in

the processing of spatial configural non-verbal information.
However, even with normal Ss the specialization of non-

.verbal spatial functions in the right hemisphere has not
been shown to be as robust as the lateralization of verbal

functions in the left hemisphere. The possible reasons for

this limited effect are as follows: First, this reduced

effect may be a result of either more diffuse representation

for non-verbal spatial functions within the right hemisphere

or bilateral though unequal representation of spatial skills.

These possibilities point out the necessity of assessing

performance of both hemispheres on clearly specified exper-
imental tasks. Second, this limited effect may be a func-

tion of the use of stimuli which involve both verbal and









spatial components. This possibility suggests the need
for clear definition and specification of both the stimuli

and the operations involved in the tasks developed to

assess right hemispheric functioning (Teuber, 1962; Satz,

1966). Third, this limited right hemisphere effect may be
a function of the modality in which hemispheric:asymmetry

is assessed. Because of the presence of ipsilateral and

contralateral pathways, the auditory and tactile modalities

do not clearly provide a means of isolating stimulation to

one hemisphere.
However, in contrast, thie visual modality provides a

unique means to specify the.hemisphere to which stimulus
material is most immediately projected. Specifically, the

lateral retinal fibers project directly to the ipsilateral

hemisphere while the medial retinal nerve fibers project to

the contralateral hemisphere via decussation of the medial

fibers at the optic chiasm. With this nerve fiber arrange-

ment, stimuli presented lateral to a point of fixation will

be projected most immediately via the lateral fibers of one

eye and the medial retinal fibers of the other eye to the
contralateral hemisphere. Thus, lateral presentation of

stimuli provides a means of isolating the most immediate

hemis heric stimulation in normal Ss and this isolation

provides a methodological advantage not available to auditory
and tactile laterality studies. Indeed, experimental studies
within the visual modality have been more numerous, primarily





'13


as a function of the expectation that this unique neuro-

anatomi~cal structure and lateral stim-uli presentation would

permit selective testing of inferences about normal cortical

asymmetry within a potentially wide range of visual stimuli.
Nevertheless, developments within visual studies have been

replete with numerous methodological and procedural limi-
tations that have obscured possible brain behavior relation-

ships and restricted their clinical interpretations.
The following section provides a brief review of the

studies using lateral stimuli presentations in the visual

half fields (VHF) and formulates a series of questions

which are experimentallry investigated in this present study.













VISUAL HALF FIELD STUDIES


The vast majority of visual half field experiments have

employed tachistoscopic procedures which utilize a recogni-
tion rather than a recall (short-term memory, STM) paradigm.
These studies contrast with the dichotic listening recall

parac gm and have been classified into two types of designs
(Hines, Satz, Schell and Schmidlin, 1969): .successive random
ta-chistoscopic presentation (Type I), and simultaneous

tachistoscopic presentation (Type II). In both designs,
st-imulation is to the lateral visual half fields which in

turn projects directly via crossed and uncrossed pathways
to the contralateral hemisphere (i.e., before decussatioh).

Successive Random Tachistoscopic Designs (Type I)

Experiments with successive random tachistoscopic
stimuli presentations instruct Ss to focus on a central fix-

ation point and to report recognition of stimuli presented
in the lateral visual half field (VHF) on each trial.

The majority of Type I studies (stimuli presented to
either the left or right of fixation) have demonstrated

superior recognition for verbal material presented to the
right visual half field (RVHF). Mishkin and Forgays'(1952)
initial demonstration of an RVHF recall superiority for








words has been replicated on numerous occasions (Bryden,

1966; Forgays, 1953; Goodglass and Barton, 1963; Harcum and
Finkel, 1963; Orbach, 1952; Terrace, 1959; W~innick and

Dornbush, 1965; Overton and Wiener, 1966). Superior RVHF

recognition (binocular presentation) has also been demon-
strated for a variety of verbal stimuli includihg letters

(Bryden, 1965; Bryden and Rainey, 1963; Bryden, 1966; Heron,

1957, Kimura, 1966; Fontenot, 1.973), single letters in
mirror image (Bryden, 1966), outlines of familiar objects

(Wyke and Ettlinger,.1961; Bryden and Rainey, 1963), and

digits (Hines, 1968; Hines, Satz and Schell, 1969; Hines
and Satz, 1971). M~onocular successive tachistoscopice pres-
entation of verbal stimuli has also demonstrated an RVHF

recognition superiority for both eyes (Barton, Goodglass
and Shai,.1965; Goodglass and Barton, 1963; Overton and

Wiener, 1966; Shai, Goodglass and Barton, 1972).
The cerebral dominance hypothesis suggests that this

VHF asymmetry is due to the use of verbal stimuli and the
more direct connections between the RVHF and the speech/

language analyzers on the left hemisphere (Kimura, 1967;

Bryden, 1965). In contrast, an alternative hypothesis
(Heron, 1957) explains the VHF asymmetry in terms of a left-

right reading habit. This direction-scanning hypothesis

suggests that when words are presented to the right of fixa-
tion, both the directional scanning and the intrinsic char-
acteristics of the stimuli follow the normal left to right






16


reading habit. However, when stimuli are presented to the

left of fixation the scanning hypothesis suggests two com-

peting scanning movements are necessary: a right to left
movement to the beginning of the word and an additional

left to right movement to read the stimulus. The demon-

striation of an LVHIF superiority by Heron (1957), for example,

in this Type I design, offered at least partial support for

the directional scanning hypothesis.

However, Orbach (1952) demonstrated a limiting case of

the scanning hypothesis by showing that the LVHF superiority

for Hebrew words occurred only' if Hebrew was the Sps native

language (where early reading training was from right to

left). Goodglass and Barton: (1963) further argued that the
method of -stimuli presentation, horizontally presented words,

itself induced a scanning bias confounding the possible

demonstration of !lateral hemispheric mechanisms. The ver-

ti~cal presentation of words with native-speaking Israeli Ss

(Barton, Goodglass and Shai, 1965) indeed demonstrated lower

recognition thresholds in the RVHF for both English and
Hebrew words. Despite the fact that Hebrew is read from

right to l-eft, native readers of Hebrew, whose scanning

training is the opposite of English, produced an RVHF recog-

nition superiority, a finding consistent with CNS effects

but inconsistent with the scanning hypothesis. Orb ach

(1967) subsequently showed that both scanning and hemispheric
differences are determinants of the RVHF superiority for

verbal material. Native-born Israeli Ss who learned English~








as a second language had more accurate recognition for both

English and H-ebrew words from the RVHF. Yet, the larger
RVHiF recognition superiority occurred.with English words,

where both directional scanning and hypothesized hemi-

spheric differences favor a larger RVHF effect.,
A second line of evidence in support of a reading habit

interpretation derived from Forgays' (1953) finding that an

RVHF superiority was obtained in school children beyond the

eighth grade but was absent below the eighth grade. McKeever
and Huling (1970) have pointed out, however, that if the

RVIHF superiority is the result of training,.then there should

be an accumulative effect over the developmental years pro-

ducing a gradual increase in the RVHF superiority rather

than th~estep function observed at the eighth grade level.

These authors found~ a clear RVHF superiority independent of

acquired reading skills: two groups of seventh grade
children, one with normal reading ability and a second with

third grade reading skill both produced an RVHF recognition

superiority.
A second line of evidence in support of a central

effects (CNS) hypothesis in Type I studies is the reversal

of VHF superiority with the presentation of non-verbal
stimuli. Kimura's (1967) demonstration of more accurate

enumeration of "'non-verbal" stimuli. (dots) from the LVHF

was explained in terms of more direct access between the

IVHF and the hypothesized non-verbal spatial processors in









the right hemisphere. However, this LVH-F effect has demon-

strated no consistency: no significant VHF difference was

found for simple geometric forms (Bryden, 1960; Bryden and

Rainey, 1963; Heron, 1957); in fact,.outlines of objects

produced the opposite VHF effect (Wyke and Ettlinger, 1961;

BRryden and Rainey, 1963). These conflicting results have
recently been explained (Fontenot, 1973) in terms of the

high verbal codeability of these stimuli, e.g., a familiar

spatial three' equal-sided outline form is readily verbally
l~abeled. In a study with codeability as an independent

variable, Fontenot (1973) demonstrated that .VHF performance

varied as a function of the type of stimulus material:

superior recognition of verbal stimuli from the RVHF;

superior recognition of the complex non-verbal stimuli from
the LVH~F.

The only studies which have demonstratedd a non-verbal

LVHF superiority have' been those of Kimura (1966,1969) and

the recent study of Fontenot (1973). Kimura's studies have

to date resisted replication (Kinsbourne, 1970) except under

one very restricted special condition (Van Nostrand, 1970).

Thus, the experimental evidence for an LVHF superiority,

using Type I studies, is somewhat inconsistent with brain
lesion studies which have shown the right hemisphere to

indeed be specialized in the processing of non-verbal spatial

configural data. A replication of Fontenot's (93 td

would offer some support for this Type I design.








Nevertheless, even that would not be independent of the

RVH-F bias (Orbach, 1967) inherent in this recognition pro-

cedure or the attenitional limitation of the tachistoscopic

procedure itself (White, 1969).

Simultaneous Tachistoscopic Designs (Type II)

Experiments with simultaneous tachistoscopic stimuli

presentation instruct Ss to focus on a central fixation

point and to report recognition of stimuli presented in both
lateral visual half fields on each trial.

Undei- most conditions of simultaneous presentation

(stimuli presented to both the left and right of fixation),
studies have found an LVHiF recognition superiority for both

verbal (Brydeni, 1960; Bryden and Rainey, 1963; Heron, 1957;

Kimura, 1969; Hines, Satz, Schell and Schmidlin, 1969;

Harcum, 196C4) and for non-verbal stimuli (Bryden, 1960;

Kimura, 1969; Bryden and Rainey, 1963). An RVHF recognition

superiority has been found only infrequently: for outlines
of familiar objects (Wykei and Ettlinger, 1961) and for

letters under modified conditions (Kimura, 1969; Heron, 1957).

The more frequent occurrence of an LVHF superiority

regardless of the type of stimuli used (i.e., verbal and
non-verbal) has been explained in terms of a second kind of

directional scanning. That is, under simultaneous stimula-

tion, there is a tendency to scan the LVHF before the RVHF.
Kimura (1966) suggests that, indeed, fundamentally different

factors underly the VHF asymmetries in the Type I (successive)






20


and Type II (simultaneous) experimental designs. She hypoth-

esized that under successive presentation (Type I) the type

of stimulus material (i.e.., verbal vs. non-verbal) deter-

mined the VHF recognition superiority. Alternatively, she

suggested that under simultaneous stimulation (Type II)

directional scanning tendencies would predominate (LVHF

superiority) and functionally suppress superior RVH-F perfor-

mance. Hines (1973a)has recently demonstrated that inter-

ruption in directional scanning process causes a significant

shift of lateral asymmetry to the RVHF. Words presented to

the lateral VHI3Fs simultaneously produced an 1,VH-F superiority.

However, under identical stimuli and presentation conditions

with a fixation control, simultaneous stimulation produced

anl RVIHF -superiority larger than the previous LVIF- effect.

Hines (197312) suggested that the direction of reading hypothe-

sis cannot explain the variation in asymmetry between the

two tests, with the shift to the RVHF superiority inter-

preted as support for the cerebral dominance hypothesis.
Kinsbourne (1970) has pointed out the difficulties in-

volved in interpreting asymmetries observed in various non-

verbal tachistoscopic tasks. Nevertheless, Hines' (1973a)

demonstration of an ~RVHF superiority on a non-verbal task

with simultaneous stimulation raises serious questions of

the utility of this paradigm (Type II design) to assess

hemispheric functional differences. The direction of read-

ing effects appeared to have no effects on the non-verbal






21


task (Hines, 1973b).,yet th~e expectation of a non-verbal

LVHF superiority was not confirmed. The failure to demon-

strate an LVHF superiority with non-verbal material suggests

one of two possibilities (1) either hemispheric functional

differences are distributed significantly differently than

would be indicated by the quantity~of clinico-pathological

data (i~ce., that the right hemisphere is specialized in pro-

cessing non-verbal spatial functions), or (2) that this

paradigm continues to be confounded by the complexity of

tachistoscopic recognition tasks (Wlhite, 1969). There is an

acciumulative~ evidence from normal auditory and tactile stud-

ies as well as ~from thie successive presentation visual

studies (Type I) that the first of these possibilities is

the less likely.

In summary, while recent progress has advanced both of

these methodologies (Type I and Type II), findings suggest

that the direction and magnitude of the visual laterality

effect is dependent upon several factors including type of

stimiuli (verbal vs. non-verbal), presentation rate, scoring

procedure and method of presentation. Some support from

normal Ss, for the cerebral dominance hypothesis has ob-

tained; however, the ~failure to demonstrate a consistent

replicable L~VHF superiority with non-verbal stimuli weakens

the arguments pertaining to the specialized role of right

hemisphere mechanisms in the analysis of non-verbal cues.





22


Simultaneous St'imulation Recall Design (Type III STM

Type III recall studies present stimuli in a temporal
series simultaneously at fixation and in one.-VHF. This pro-

cedure was developed by Hines (1968) in his efforts- to

develop a visual paradigm similar to the auditory paradigm

(dichotic listening) that had been shown to be a reliable

measure of cortical asymmetry.

In the dichotic listening studies the magnitude of the

asymmetry had been shown- to be a function of increased ~list

length and the competition of the simultaneous stimulation.

Thus, in his study, Hines (1968) modified the Type II para--

digm in order to increase the number of stimuli in each VH-F
within each trial and thereby more close-ly approximate the

auditory condition producing the greatest aud~.itory asymmetry.

Further, Hines varied the location of the simultaneous_

stimuli: in each trial stimuli appeared in a temporal

sequence (in the same location) with series simultaneously
either in both VHFs (modified Type II paradigm) or simul-

taneously at fixation and one VHF (Type III paradigm).

When digit-stimuli series were presented simultaneously

in both VHFs (modified Type II.paradigm) Ss were instructed

to focus on a central fixation point (immediately prior to

the.trial stimuli) and to then recall the series of digits

presented simultaneously in the VHFs. Results from this
modified Type II paradigm demonstrated superior recall for

verbal stimuli presented to the LVHF. However, subsequent






2 3


analysis of report strategies showed that Ss primarily used,

a temporal order of report, the LVH-F .was reported prior to

the RVHF. This finding appeared consistent with the Type II

studies and substantiated the importance of directional

scanning effects~ in the VHF asymmetries.

However, when the same digit sequences were simultane-

ously pr-esented to the macula (fixation) and one visual half
field (VHF), and when report of the fixation digits was

required prior to tLhose in the VHF, then an RVHF recall

superiority (Type III paradigm) was obtained. W4ith the
fixed order of report, roughly 80% of the Ss had superior

recall for digit~s from the RVHF'. Analysis of serial posi-

tion effects for the three-pair and four-pair digit sequences

revealed a significantly higher RVHF effect for those digits

most remote in time. As the more recent digits (i.e., last

digi-t within 'a trial sequence) did not demonstrate the

significant VHF difference, the asymmetry was explained in
terms of recall or short-term memory (STM) processes rather

than visual recognition.

Type III studies not only control for order of report

but also provide a most reliable control of fixation and

directional scanning, both of which have been poorly con-

trolled for in tachistoscopic studies, Type I and Type II

(White, 1969). Replications of Type III studies have
without exception continued to demonstrate the RVHF superi-

ority (i.e., verbal effect) for both a wide range of









presentation times and stimuli pair sequence lengths. Hines

and Satz (1971) showed that the greatest asymmetry was

demonstrated with -the faster presentation times (17 7

msec./digit pair) on a 4 x 3 presentation sequence (four

digits at fixation, three digits to the left or right VHF,
the first six digits presented in pairs followed by the

fourth digit at fixation). McKeever and Huling (1971a)

have offered additional support that this Type III paradigm

continues to display an RVHF superiority for word recall

for both.1eft and right eye monocular presentation. Further,

in a Type III paradigm a significant RVHF superiority was

even. demonstrated when the method of presentation employed

simultaneous presentation of only one stimulus pair (one

word to the left and one~ to the right of fixation, and a

digit at fixation), and thus recall was subsequent to report

of only one fixation digit. McKeever and Huling (1971b)

suggested that this finding contradicted the earlier studies

that displayed an -LVHF superiority with bilateral word pres-

ehtation .(e.g., Heron, 1957). This suggestion has, however,.

been refuted by the demonstration that the procedural .con-

trol of fixation by the fixation digit is an important

determinant in the VHF asymmetry. Hines (1973b3)has recently

s-hown that when the center digit was not presented, Ss

recognized more words from the LVHF, a finding consistent

with the Type II studies of simultaneous VHF stimulation.

But, when the center digit was present Ss recognized 5.3






'25


times as many words from the .R~VHF (Hines, 1973b). For the

verbal -condition, the Type III design offers consistent

evidence of an RVHIF superiority while controlling many of

the sources of variance evidenced in previous designs (Types

I and II). Nevertheless, the strongest support for the

hypothesis of dual functional hemispheric differences would
come from the dlemonistration of differences in VHF a-symmetry

as a function of differences in stimulus material (verbal

vs. non-verbal).' Hines (19738)was recently unable to demon-

strate thlis -doub~le dissociation, as he failed to demonstrate

an LVHF asymmetry with design stimuli using the modified

Type III paradigm (one d~igit at fixation, one non-verbal

design in either the left or right ViHFs). Only the study

of Schel-l (-1970) reported a {(significant) non-verbal LVHF

superiority -using the Type III paradigm; however, this find-

i~ng is limited because of the failure to employ a verbal
condition control.

In summary, the siligular consistency of the Type III

RVHF effect for verbal stimuli is most often interpreted as

being consistent with a CNS brain asymmetry hypothesis

(Kimura, 1967). The addition of a fixation control and the

recall paradigm (STM) provides a methodology that controls

for many of the criticisms of Type I and Type II paradigms.

Haber's (1970) recent demonstration that linguistic memory

is quite distinct from pictorial memory (i-.e., non-verbal)

appears consistent with Schell's (1970) suggestion of a VHF









shift as a function.of stimulus material. There .i~s then

both theoretical and empirical support for the utility of

the ~Type III paradigm. This paradigm also offers promise

in attempts to explore further parameters of laterality

mechanisms in man including the processing of non-verbal

information.

Whiile this paradigm appears the more promising in

controlling procedural and methodological sources of vari-

ance, any fur-ther study must also control for those several

sources of sample vatri~ance that have in earlier studies been

shown to obscure the assessment of possible hemispheric

effects. Specifically, age (Len~neberg, 1967; Kimura, 1963b;

Netley, 1972; Gazzaniga and Hil~lyard, 1971), handedness

(Gloning, Gloning, aHau and Q~uatember, 1969; Serafetinides,

Hoare and Driver, 1965; Zangwill, 1962; Branch, Milner, and

Rasmussen, 1964), and familial Ihistory of manual preference

(Zurif and Bryden, 1969; Hines and Satz, 1971) have been

shown to obscure attempts to assess lateralization with

normal Ss.

The present' study seeks to control these sources of S.
variance and to address itself to the following general

questions.

(1) Can previous findings of an RVHF asymmetry in a

Type III paradigm be replicated using letters.rather than

digit stimuli? Previous Type III studies using digits have
been limited by the range of the single digit universe





2T.


(0-9). The use of letters would increase the stimulus uni-

verse (26-letter alphabet) and would decrease the chances

of guessing--a criticism ~that could be leveled against the

use of digits. -Failure to produce an -RVHF asymmetry with

letter stimuli would offer major criticism of the Type III

paradigm as a sensitive measure of hemispheric specialization
of verbal materials.

(2) What are -th~e effects, if any, of rate of presenta-
tion (intrastimulus interval) and increased number of VHF.

stimuli per trial on the VHF recall? Previous studies with

digits (Hines and Satz, 1971) have suggested no ~significant

changes in asymmetry across it wide range of presentation

time. Increasing the memory demands of the Type III task

as in the present study~may, however, alter .the asymmetry.

Nonetheless, increasing the length of verbal letter pairs

within each trial would make the Type III paradigm more

analogous to the Dichotic Listening Test wJhich has shown

that the magnitude of the ear asymmetry increased as a

function of list length.

(3) What are the effects of serial position and percep-

tual factors on the recall from the VHFs? Specifically,

the effects of memory will be evaluated by increasing the

number of verbal stimuli within each letter pair sequences

and examining recall within each serial position. The

effects of backward masking (selective reduction in the

accuracy of recall of a stimulus by presentationof another






28


stimulus immediately subsequent to the presentation of-the

first stimulus) will be evaluated on the verbal task pro-

ducing the greatest; asyrge:?~ctrly. '-Comparison will be made

between recall from the serial positions most remote in time

with recall from the most recent serial position (no subse-

quent sti-muli). On the task producing the greatest asym-

metry, perceptual factors will be evaluated by~varying

presentation ~time w~ith the same interstimulus interval.
Failure to produce a significant difference in performance

across VH~F when only presentation time is varied would argue

against criticism that perceptual factors play a major role-
in the VHIF asymmetry at these presentation rates.

(4) Whnat. a-re the effects on; VHF asymmetry when design
stimuli are used wuit~h the specific intent of creating a non-

verbal analogue of the Type III paradigm? This general

question requires the development of a set of spatial con-

figural designs that nave ~imited access to verbal coding.
These stimuli for fixation and/or VHF presentation (see

Method section for specific objectives) will then be used

in a Type III paradigm to evaluate the hypothesis that the

right hemisphere plays a distinctively important role in

the perception of non-verbal spatial configural information.

Superior recognition of- non-verbal spatial configural stim-
uli in' the LVHF would offer evidence in support of this

hypothesis. RE;ate of presentation will be identical to that
found to produce the greatest asymmetry withi the letter






29


stimulus task. The effect .of memory will be evaluated by

examining the effects of serial position on the VHF asym-

metry.

(5) Assuming that a non-verbal- analogue can be devel-

oped, can it be shown that VHF superiority varies` as a func-

tion of stimulus material (verbal and non-verbal)? Specifi-

cally, Ss will be given both the verbal and the non-verbal

task. The consistent demonstration of a superior recall of

verbal material from the RVHF has been interpreted' as imply-

ing left hemisphere superiority in the processing of verbal

information. Consequently, subjects in the study will be

expected to show this RVHE superiority. If they do not,

there would be grounds for questioning ~the meaningfulness

of the results and to su~p~ect the i~diosyncrasy of this par-

ticular experimental situation. However, if Ss show supe-

rior recall. for the verbal stimuli presented to the -RVHPF,

then any difference in VHF~~superiority with the non-verbal

stimuli with the same Type III paradigm would appear to be

a function of differences in stimulus input. A demonst-ra-

tion of an LVHF recall superiority for non-verbal spatial

configural stimuli would offer evidence supporting the

hypothesis that the .right hemisphere plays a distinctive
role in the processing of spatial configural information.

In view of the procedural advantages .of the control fixation

paradigm, a Type III demonstration of an LVHF recall superi-

ority Ifor non-verbal stimuli and a within S's RVIHF recall






30


superiority for verbal stimuli would be strong evidence

supporting Kimura's (1966) hypothesis of a dual functional

asymmetry in hemispheric' organization.

















Th-is research presents three major studies. First

(Study I), the devJelopment of a new verbal task within the

Type III paradigm.- Thiis development involves separate
efforts: (a) a change in the natu-re of the presentation

s timul i (i.e,, di gits~ to lIette rs ); (b) an increase~in the
number of stimuli at -fixatich and in the VHF to make this

task more analogollus to thie Pichotic Listening Test; (c) an

assessment of-the effects of presentation rate upon VHF

asymmetry; and (d) an assessment of serial order effects.
Second- (Study II),the development of a non-verbal recall

analogue of the Type: III verbal paradigm (Study I). This

development involves (a) generating a set of non-verbal

design stimuli; (b) an assessment of recognition parameters
`of these non-verbal stimuli with serial presentation; (c) an

assessment- of the effects of rate of presentation upon VHF

asymmetry for non-verbal designs; and (d) the assessment
of serial order effects. The third major study (Study III)

is 'to then utilize the procedures developed in Study I and

Study II with a new group ofSs to determine whether VHF

performance (within Ss) varies as a function of the type of
stimulus material (verbal and non-verbal). -Study III


METHOD









further involves an attempt, to replicate the effects of

serial position in Study TI and Study II.


:Study I

Subjects
All Ss were undergraduates at the University of Flor-

ida. Subjects were all right-handed by self-report and had

corrected or uncorrected visual acuity of at least 20/20.

Visual acuity was established through the use~ of a Snellen

Eye Chart .

Materials

All tests were administered in a dark windowless room

with one sinall 25-watt light to the Sp side and used by the

experipieriter to record thle St answers on the answer sheets

(see Appendix 1). Subjects were seated at a long table

with their :heads positioned by a commercial chin rest

mounted on the end of the ;table. Stimuli were projected ait~

about eye level onto a large rear view projection screen

4'-10" in front of the Ss. Each experimental procedure em-

ployed a motion picture film made with the stimuli and
stimulus parameters for that particular procedure. A Kodak

Analyst 16 mmn-projector with a modified governor was used
to obtain a variety of speeds ranging from -10-24 frames per

second. The projection rate was checked by means of a time

loop after the machine had warmed up prior to each experi-
mental session.






33


Stimuli (letters)

The verbal test stimuli were single block letters of

the English alphabet which appeared white against the darker

background of the screen. Letters were employed rather than

digits in order to be able to increase the stimulus pairs
without repetition within any one trial sequence. Each

l-etter subtended one degree of visual are in height and 45'

in -width. The inner edge of each V'HF stimulus letter was.

approximately three degrees of visual are from the center
of fixation.


Procedure (5 fixation letters, 5 VHF letters)

At the beginning of each verbal letter trial, a central

fixation indicator (a cross the same size as the stimnuli)

~appeared for approximately one and one half seconds depend-

ing on the film presentation _speed. The cross at fixation

was immediately followed by five sequential letter pairs with

five letters at fixation and five letters simultaneously in

the VHF. Wi~ithin each trial all five VHF letters were pre-

sented to the same VHF. No letter appeared more than once

on any given trial. All trials were counmter-balanced; each

trial letter sequence presented in one VHF was also pre-

sented to the other VHF with the same fixation letter se-

quence. Each five-letter sequence was presented twice to

each VHF by repetition of the first 30 experimental trials.

Letter sequences were presented at fixation and alternately









to e-ach VHF. An intertriial interval of approximately 15

seconds was used for recall.

Subjects were instructed to fixate on the central fixa-
tion cross and then on the fi~ve-letter sequence presented:

at fixation. Subjects were instructed to wait for ~the trial

completion and then to report (orally) in any order, the
five-letter sequence presented at fixation before recalling

any letters presented to the left or right VHF. Subjects
were also permitted to recall- letters from the VHF in any

order and were instructed that they did not need to be sure

of their answer-but only needed to think they saw a particu-

lar letter in the VHF in order to report it. Six practice

trials and 60 test trials were administered in each verbal

condition.. All responses were recorded by E. .Trials in

which-all letters from fixation were not reported correctly

were scored as zero aznd reportsof VHF stimuli on these trials

were eliminated froni subsequent analysis.

Subjects were administered one of three experimental
conditions: (1) 280 msec. presentation time, no intrastimu-

lus interval between letter pairs, (2) 330~ msec. presenta-

tion time, no intrastimulus interval, and (3) 165 msec.

presentation time, 165 msec. intrastimulus interval.

Study II

Subjects
Subjects were undergraduates at the University of
Florida and selected as in Study I as right-handed by









self-report and with corrected or uncorrected visual acuity

of 20/'20. Different Ss were -used in the two parts of Study

II (Experiments 1 and 2).

Materials

All tests (Study II, Experiments 1 and 2) were adminis-

tered as in Study I.


Stimuli (designs)

The non-verbal design test stimuli were single designs

of a group of preselected 24 designs of approximately the

same. complexity as the letter. stimuli (see Appendix 2).

In a preliminary study-, the number of experimental designs

hrad been reduced to 24 by elimination of those designs in

whichi there was any consensus of verbal labeling among five.

Ss in an age range similar to that of the experimental sub-

j ect s. Like the verbal letters, the non-verbal designs also

appeared white against the darker background of the screen.
Each design was approximately the same size as the verbal

letters and .was positioned like the verbal stimuli with its

inner edge approximately three degrees of visual arc from
the center

Procedure

Experiment 1 (3 fixation designs, no VHF stimuli)
The purpose of this experiment was to examine recogni-

tion, parameters of these non-verbal fixation stimuli with

serial presentation.









In the pilot studies, previous Ss had been adminis-

tered one of five experimental conditions: (1) three de-

signs at fixation, two designs in the VHF; (2) two designs-
at fixation, two designs in the VHF; -(3) two designs at

fixation, two designs in the VHF, forced choice; (4) two

designs at fixation, one design in the VHF, at 280 msec.;

and (5) two designs at fixation, one design in the VHF at
330 ms~ec. In each of these studies trials .a~peared too

difficult for Ss with response scores at a random level with

no significant VHF differences.

To assess th~e discrepancy between these random level

performances .and performance on the verbal task (Study I)
with five letter pairs, Experiment 1 (S'tudy II) employed

pnly fixation design stimulii and no VHF' stimiuli.
Like the verbal stimulus. film (Study I), the beginning

of each non-verbal design trial wvas preceded byi a central

fixation cross appearing~ for approximately one and one half

seconds. The cross at fixation was immediately. followed by

three. sequential digits at fixation with no stimuli in the

dark VHF. No design was repeated -within any one trial.

Subjects were instructed to.fixate on the central cross and
then on the designs presented at fixation. At~the end of

each trial, Ss were required to select from a visual display

of 10 designs, the three designs presented at ~fixation (see

Appendix 2). Subjects were permitted to recognize the

designs in any order and were instructed that they did not






-37


need to be certain of their decision in order to make a

selection. The designs were numbered and all responses

were recorded by E on the 20 experimental trials. Subjects

were administered one of two experimental conditions:

(1) 330 msec. presentation time, no intrastimulus interval,
40 trials, or (2) 500 msec, presentation time, no intra-

stimulus inte-rval, 40 trials.

The results of Experiment 1 indicated that the initial

tasks of fixation recognition (pilot studies) were too dif-

ficult: Condition. 1 (mean correct 2.03), Condition 2

(mean correct' = 2.03)~. This performance precluded the use

of design stimuli ~at fixation and the VHF because of the

requirements of the Type III` paradigm (i.e., perfect fixa-
tion recall to control for directional eye movements). For

this reason, it was decided to explore the use of digits

at fixation and designs in the VHF.


~Experiment 2 (2 fixation digits, 1 VHF design)
The purpose of this experiment was to develop a Type
III task with non-verbal design stimuli only in the VHF.

In this experiment the initial cross at fixation was fol-

lowed by two digits sequentially at fixation and one design

in the VHF. The initial digit of the sequence preceded the

onset of the design by one half of presentation time. The

second digit remaining on the screen for one half the

presentation time after the design was no longer present








in order to control for the effects of visual scanning.

Identical. trials were counterbalanced with each design pre-

sented to both VHFs with the same digit sequence at fixation.

Rotation of the design stimuli in the counterbalance trials

(i.e., what was the left side of the stimulus became the

right) was achieved to control for directional cues in the
stimuli designs. Designs were presented alternately to each

VHF. Subjects were instructed to fixate on the central cross,

to report th-e digits at fixation, and then to select from

a visual display of five designs the design presented in the

VH.All responses were recorded by E. Trials in which the

digits at fixation were not reported correctly were scored
as zero and reports of VHF stimuli on these trials were

eli-minated from subsequent analyses. Subjects were adminis-

tered one of two experimental. conditions : (1) 330 msec.

presentation time, no i~ntrastimulus interval, 16 trials, or

(2) 280 msec. presentation time, no intrastimulus interval,
16 trials.


Study III
In Study III Ss were administered both verbal and non-

verbal stimuli.


Subjects
Subjects in Study III had not participated in any of

the previous VHF studies. Subjects were selected not only
as right-handed by self-report but also by evidencing no









behavioral indications of mixed dominance (Satz self-

administered survey of lateral dominance). Subjects were

excluded who reported any history of sinistrality or cere-

bral, s inal or peripheral nerve disease. No Ss were used
whose corrected or uncorrected visual acuity was not at

least 20/20 as tested prior to the experiment. The fifteen

Ss' ages ranged from 18 to 23 years with a mean age of 20.6

years.

Materials

All tests were administered as in Study I and Study II

(Experiments 1 and 2).

Stimuli ~(letters--5 fixation letters, 5 VHIF letters)

The verbal stimuli were those developed in Study I and

presented at the rate (330 msec.) found in Study I to pro-
duce the greatest VHF asymmetry with verbal stimuli.

Stimuli (designs--3 fixation digits, 2 VHF designs)

The non-verbal design stimuli were those developed in

Study II and presented at the rate (330 msec.) found in

Study I to produce the greatest RVHF asymmetry with verbal
stimuli.

Procedure

The verbal letter film was presented first to all Ss

in order to allow for subsequent analysis of the attentional

hypothesis l(Kinsbourne, 1970). Presentation and scoring









were the same as in Study I. The non-verbal design film

(with digits at fixation) was presented immediately after
the verbal film.

The non-verbal condition was modified on the basis of

results from Study II. First, the use of designs at fixa-

tion had proved to be too difficult (Experiment 1) and

second, the use of two digits at fixation and only one

design in the VHF had proved to be too easy (Experiment 2).
For these reasons a new non-verbal design film was

created. The center fixation cross of approximately one

and one half seconds on each trial was immediately followed

by three digits at fixation and two designs in the VHIF.
The onset of~ the initial fixation digit 'in the sequence

preceded the onset of the first design in the VJHF by 165
msec. and the third fixation digit remained on the screen

for 165 msec. after the second design was no longer present.

Identical trials were counterbalanced and designs rotated

as in Study II, with each design sequence presented twice
to each VHF in both the rotated and not rotated orientation

for a total of 72 trials. Designs were presented alter-

nately to each VHF and within each trial both designs were

presented to the same VHF. No design appeared more than
once :Ln any given trial. An intertrial interval of 15

seconds was employed for recognition recall. .Subjects were
instructed to -fixate on the center cross and then on the

three digits presented at fixation. At the end of each









trial Ss were instructed to report the three digits pre-

sented at fixation before pointing to the two designs from

a visual display of five designs. Each trial had a differ-

ent five-design display with the two correct designs and

three incorrect designs randomly distributed (see Appendix

3). Subjects were also permitted to recall the designs in

any sequence as long as the designs were recalled subsequent
to.the report of the digits of fixation. Trials on which

all three digits from fixation were not reported correctly

were scored as zero and reports of VHF stimuli on these

trials were eliminated from subsequent analyses. All

responses were recorded by E (both the digit report and
the designs pointed out; see Appendix 4).














RESULTS


Study I

The purpose of this study was to develop a new verbal
task (Type III paradigm) using letters at fixation and in
the VHF.


Analysis of VHF mean differences for verbal stimuli
The mean correct responses for each VHF under the three

experimental conditions with letter stimuli are shown in
Table 1.

The mean correct response scores for the left and right

visual half fields were analyzed for- VHF mean differences by

presentation times. The mean correct scores for the RVH~F
were superior in all three presentation times. At the 280

msec. presentation time, the VHF mean scores showed an 18.32%

RVHF superiority. At the 330 msec. presentation time, the

VHF mean scores showed a 32.36% RVHF superiority. At the

165 msec. presentation time the VHF mean scores showed a

29.70% RVHF superiority.

The mean correct response scores for the visual half

fields were also analyzed for overall (across three condi-

tions) differences between VHFs. The overall differences

between mean correct response scores in the VHFs were highly
















280 msec. None 1 8.40 22.13 11' of 15 13. 5 18.32

330 msec. None 23.67 31.33 14 of 15 18.3 32.36

165 msec. 165 msec. 23.33 30.26 14 of 15 17.9 29.70


*Percent of right superiority determined by subtracting left score from the
right, dividing by the left score and multiplying by -100.


Table 1

VHF Mean Correct Responses and Frequency of Right VHF Superiority
for Verbal Stimuli at Three Presentation Times


Subject with
Presentation Intrastimulus Left VH-F Right VHF Right VHF
Time Interval Mean Mean Suaeirt


Percent Recall Percent of Ri~ght
from Both VHFs VHF Superiority*









significant (F = 68.04, df = 1,14, p <~ .001) with recall of

letters presented to the RVHF superior to recall of letters

presented to the LVHF. The meat correct response scores

are presented graphically in Figure 1.

A larger RVHF asymmetry was demonstrated at the 165 and

330 msec. presentation times. A trend toward increased over-

al~l recall at these presentation times was observed but the

scores were not statistically different from the 280 msec.

condition.

The differencesin mean correct recall by VHF and by

presentation rate were also reflected in the frequency of Ss

showing higher RVHF correct recall scores. In the 280 msec.

condition only 11.of the 15 Ss showed superior_ RVHF scores.

However, in both the 165 and 330 msec. conditions, 14 of

the 15 Ss showed s-uperior RVH-F scores.


Mean recall by serial position for verbal stimuli

The overall mean recall by serial position for verbal

stimuli is presented in Table 2 for each VHF. The mean

recall pattern by serial position showed superior recall

of the fifth letter followed by decreasing mean recall in

the fourth, third, first and second positions. However,

while recall of the letters presented to the RZVHP was higher

in all five serial positions, the percent of RVHF superi-

ority was higher for those letters in serial positions most
remote in time from the termination of each trial sequence.


























330 msec. presentation
time, no intrastfimulus
interval

165 msec. presentation
time, 165 msec. intra-
stimulus interval








280 msec. presentation
time, no intrastimulus
interval


Left


VHF


Figure 1. Mean correct response scores by VHF at
three presentation times.


Right






Tab le 2

Mean Correct.Recall for Letters and VHF
by Serial Position

Letters
VHF 1 2 3 4: 5 1 to 4 1 to 5

Left 2.28 2.04 2.82 3.84 10.82 10.98 21.80


Ri ght 3. 53 3.44 3.98 4 33 12.42 15. 28 27 70


% of Right
Superiority


54.82 68.63 41.13 12`.76 14.79 39.16 27.06






47


Study II

The purpose of this study was to develop a non-verbal
analogue of the Type III paradigm.


Exp Pr i ment 1

The purpose of Experiment 1 was to assess recognition

parameters of these non-verbal design stimuli with serial

presentation at fixation.

Mean recognition for non-verbal designs at fixation

The mean recognition of three designs presented at

fixation at two presentation times is presented in Tabl~e 3.

W~ith no stimuli in the lateral half field, the mean recall

for designs presented at fixation at the 330 msec. presen-

tation time was 1.79 designs. With experience (same Ss,

task repetitions), the mean recall increased to 2.03 designs

recalled per trial. At 500 msec. and 40 trials (task repe-

tition), mean design recall performance (same Ss) was only

slightly improved. When compared to the verbal performance
with letter stimuli at the same speed, this experiment

suggested increased difficulty in the processing of non-
verbal stimuli in immediate serial presentation. Future

studies had to be modified in terms of this finding.

ExDeriment 2

The purpose of Experiment 2 was to assess differences
in VHF recall with one design in the lateral VHFs and

digits at fixation.







Table 3

Mean Recall for Non-verbal Designs at Fixation


Designs at Designs in Number of Mean Design
N Fixation VHF Time Trials ~Recall

6 3 0 500 msec. 40 2.08


10 3 0 330 msec. 20 1.79


10 3 .0O 330 msec. 40 2.03









Analysis of VHF mean differences for non-verbal
design stimuli

The mean correct responses for non-verbal designs pre-

sented in the VHF with digits at fixation are presented in

Table 4. At 330 msec. presentation time with 2 digits at

fixation and 1 design presented to the VHF, performance of

4 of 5 subjects was without error on both the fixation and

VHF stimuli. On this film one subject missed only one

trial from each VHF, yielding a near perfect 97.5 overall

mean percent correct. At the faster presentation time of

280 msec., performance in both VHFs was lower for the same

number of trials. .However, at the same 280 msec. speed with

twice as many trials- (16), performance on the secondd half

of the trial was performed with a near perfect -15.6 mean

correct. This performance rate in both VHFs raised the

overall mean percent correct to 90.6' at the 280 msec. pres-

entation time with 16 trials in each VHF. Performance on

the last half of the trials at 280 msec. presentation time

paralleled the near perfect performance at the slower 330

msec. presentation speed. This suggested that, with prac-

tice, even at the faster speed the task was not difficult

enough to tap possible differences in the way non-verbal

information was processed when presented to the left or

right VHF.




















330 msec. 5 8 2 1 7.8 7. 8 97.5

280 msec. 5 8 2 1 6.8 6.6 83.8

280 msec. 5 16 2' 1 14.5 14. 5 90.6

330 msec.* 15 36 3 2 43.9 41.5 59.3


*From Study III for comparison.


Table 4

Mean Correct Responses for Non-verbal Design Stimuli
by VHF. at Two Presentation' Times with Digits at Fixation


Presentation
Time


Number of Trials Digits at Designs
per VHF Fixation -in VHF


Left VHF
Mean


Right VHF
Mean


Overall Mean
% Correct


o1









Study III
Analysis of VHF mean differences for subjects
presented both verbal and non-verbal 'stimuli
Verbal stimuli.--The purpose of this study was to

determine whether the perception of recall of materials in

each VHF varied as a function of the type of stimulus mate-

rials (verbal vs. non-verbal). Table 5 presents the VHF

means and ANOVA of the VHF performance differences at the

330 msec. presentation time for the verbal letter task. Mean

recall of letters presented to the LVHF was 32.33, while mean

recall of letters presented to the RVIHF was 43.20. The dif-
ference between mean letter recall in the two visual half

fields was significant with a right field superiority for

the recall of letters (F = 34.743, df = 1,14,' pi .001).

Non-verbal .design stimuli.--Table 5 also presents the

VHF means and ANOVA of the VHF performance differences at

the same 330 msec. presentation time for the non-verbal

design stimuli (3 fixation digits, 2 VHF designs). Perfor-
mance across trials showed a 59.3% overall mean percent cor-

rect (Table 4). Mean recall of designs presented to the

LVHF was 43.87, while mean recall of designs presented to

the RVHF was 41.47. The difference between mean design

recall in the two visual half fields was signiificant with

an LVHF superiority for recall of designs (F = 4.965,

df = 1,14, p < .05).












































LVHF X = 43.87, RVHF X = 41.47


*p < .05


~~


Source SS df MS F

Treatment 43.20 1 43.20 4.965*

Error 121,80- 14 8.70

Total 165.00 15


Table

Analysis of Variance of


5

Letter Recall by VHF


MS

885.63

25.49


F

34.743*


Source

Treatment

Error

Total


SS

885.63

356.84

1242.47


LVHF X = 32.33, RVHF X = 43.20


*p < .001


Anailysis of Variance of
Non-'verb-al Design Recall by VHF









The differences in mean correct recall by VHF and by

different types of stimuli (verbal an~d non-verbal) were also

reflected in the frequency of Ss showing higher RVHF correct

recall scores with the verbal letter stimuli and showing

higher LVHF correct recall scores with the non-verbal design
stimuli.

Table 6 presents a chi square analysis of the VHF dif-

ferences by films. With the verbal letter stimuli all 15 Ss

showed an RVHF superiority of letter recall. W~ith the non1-

verbal design stimuli, 12 of 15 Ss showed an LVHF superi-

ority of recall -for designs. The chi square .test suggested

a significant relationship between type of stimuli (letters

and designs) and the VHF superiority of recall. (Z = 24.49489,

df = 1, p ( .001).

An analysis of recall performance rank order data with

both the verbal and non-verbal design stimuli is presented

in Table 7. The relationship between rank order recall per-

.formances on the RVHFs was not significant (t = .484,

pt .05), indicating that those Ss with the higher RVHF
recall scores on the verbal stimuli did not have the higher

RVHF recall scores with the non-verbal stimuli. Thus,

abi-lity at recall from the RVHF was significantly a-ffected

by the type -of material presented in that VHF.
The relationship between rank order recall performances

in the verbal RVHF and the non-verbal LVHF: was signifi-

cant. (t = 3.23, df = 13, p < .01). Higher mean recall























Non -ve rb al
12 3
designs
15
12 18 30

X2 = 24.49489, p < .001








Table 7

Spearman Rank Order Correlations Between VHF
Performances with Verbal and Non-verbal Stimuli


Verbal Letters
LVHF RVHF


Table 6

Chi Square Relationship Between
Verbal and Non-verbal Stimuli
and Frequency of VHF Superiority


VHF
Left Right


Verbal
letters


STIMULI


LVHF



RVH F


.5884


.6678


Non-verbal
Designs


(p<.05) [(p<.01)


.028


.1331


(p>.05) (p>.05)






55


performance on the verbal RVHF stimuli appears significantly
related to the LVHF performance level on the design stimuli.

The relat-ionship between rank order recall performances

in both the LVHFs also appeared significant (t = 2.63_, df=

13, p < .05), indicating that those Ss who display the higher
mean recall for verbal stimuli in the LVHF also displayed the

higher mean recall for non-verbal stimuli in the LVHF.

However, the relationships between rank order recall

performances in the verbal LVHF and the non-verbal RVHF was
not significant (t 1.01, df = 13, p > .05), indicating

that Ss rank order performance on the verbal letters to.the.

LVHF was not significantly related~to~ the Ss rank order per-

for~mance withn des-igns presented to- the RVHF.


VHF mean recall by serial position .fo~r
non-verbal stimuli

The VHF mean recalls by serial position for non-verbal

design stimuli are presented in Table 8 and in Figure 2.

Mean recall of designs in both VHFs was highest for designs

presented more recent in time (serial position 2) with both
VHFs having lower mean recall for designs more remote in

time. However, while recall of designs from serial position

2 was higher (.?~.33% from the RVHF, recall from serial

position 1 indicated an LVHF superiority (44.11%). On those
trials where only one design was recalled there was a similar

shift: an RVHF superiority (25.66%) when correct recall was

limited to serial position 2; an LVHF superiority (103.63%)



















Left 14.80 29.07 3.93 18.20 10.87 6.27 4, 60 43.87

Right 10.27 31.20 1.93 22.87 8.33 4.20 4.13 41.47


*Percent of left superiority determined by subtracting right score from the
left, dividing by-the right score and multiplying by 100.


Table 8


Mean Recall of Serial Position by VHF for Non-verbal Design Stimuli


Correct Report
for
Serial
Position 1 Only.


Correct Report
for
Serial
Position 2 Only


Position
1 and 2
Reported
Together


Serial Serial
Position Position
1 2


1,2
Sequence
of Report


2,1 Total
Sequence Mean
of Report Recall


VHF


7.33
g~ht


25.66


ef* 44.11


103.63


30.49 49.26


11.38


5.79





44
43
42
41
40
39
38
37
36
35
34
33
32


24
23
22
21
20
19
18


11
10
9
8
7
6
5
4
3
2
1


/
/
/


/
/


Total letters


Total designs
















Designs in 2nd serial
position only








Total designs on trial
with 2 designs correctly
recalled

2 designs correctly re-
called in 2,1 report
sequence

2 designs correctly re-
called in 1,'2 report
sequence

Designs in 1st serial
position only


,>

///'


'2------L""-- '


z-


Left


Right


VHF


Figure 2. Mean correct stimuli recall.









when correct recall was limited to serial position 1, those

designs more remote in time.

On those trials where two designs per trial were re-

called, an LVHF superiority was demonstrated regardless of

the sequence in which the two designs were reported. Trials

with correct recall of two designs showed an LVHF superi-

ority of 30.49%. Total mean recall also yielded an LVHF

(5.79%) recall superiority.


VHF mean recall by serial position for verbal stimuli

Th~e VHF mean recalls by serial position for verbal

letter stimuli are presented :'u Table 9 and in Figure 2.

Mean recall by serial position in both VHFs was- lowest for

the first letter, followed by a progressive increase in

recall for the secon~d, third, fourth and fifth letters.

Recall was higher for letters presented to the RVHF regard-

less of serial position with an overall right VHF mean

superiority of 33.8%. However, the percent of RVHF superi-

ority was higher for those letter serial positions more
remote in time.


Analysis of Errors of Report at Fixation

The purpose of this analysis was to determine-whether
those trials missed at fixation varied as a function of

type of stimulus material and field of presentation. Missed

trials were computed separately for each film (verbal and

non-verbal) and a comparison was made to see whether fixation



















Left 2.40 2.86 3.86 5 67 17.53 14.80 32.33


Right 4.53 5.00 5.13 9.60 18.93 24.27 43.27


Tab le 9

Mean Recall of Serial Pos-ition by VHF
for Verbal Letter Stimuli


Letters


VHF


1 to 4


1 to 5


% of Right
Superiority


88.9


74.4


32.8


69.4


8.0


63.9


33. 8






60


errors varied as a function of the VHF in which the differ-

ent stimulus materials were presented.

Errors at fixation for Ss presented both verbal: and

non-.verbal design stimuli are presented in Table 10. With

the verbal letter stimuli there were significantly (p < .05)

more errors in the report of the fixation stimuli when the

simultaneous VHF verbal stimuli were presented in the LVHF.

By contrast, more errors occurred in the report of fixation
stimuli on the non-verbal trials when the simultaneous VHF.

non-verbal design stimuli were presented in -the RVHF.















Simultaneous VHF Presentations
LVHF RVHF

Errors at fixation 72 54
(S mean) X = 4.80X=3.0




Errors at fixation 15 16


Tab le 10

Analysis of Errors of Report at Fixation
by Material and Field of Presentation


Verbal Trials





Non-verbal Trials


*Significant at p < .05.














DISCUSSION


The present research was addressed to three major
issues. First (Study I), the development of a new verbal

task (Type III paradigm) with letters at fixation and in
the VHF. Previous studies with the Type III paradigm (Hines,

1968; Hines and Satz, 1971; Hines, 1973) had demonstrated the
methodological advantages of employing this controlled fixa-
tion paradigm in the assessment of differences in VJHF per-
formance. Study I sought to assess the methodological reli-

ability of the verbal Type III paradigm as well- as to evalu-
ate criticism of the use of digit stimuli in previous Type
III .studies.

The second major issue (Study II) addressed in this

present research was the development of a non-.verbal analogue
(VHF design stimuli) employing the Type III paradigm. A
series of design stimuli with no reliable verbal labels

(p-ilot studies) were produced. Further, Study II sought to
evaluate the appropriate conditions under which the design
stimuli could be used to develop a non-verbal Type III task.
The third issue (Study III) addressed the assessment

of the effect of type of stimulus material (verbal and non-
verbal) on VHF asynimetry (within Ss). Subjects were








administered both the verbal and non-verbal films previously

developed (Study I and Study II) in order to assess whether
the VHF asymmetry varied as a function of type of stimulus
material and VHF of presentation.


Stud dL
Results from Study I confirm the previously reported

RVH-F recall superiority on a verbal.STM task (Hines, Satz,
Schell and Schmidlin, 1969; Hines and Satz, 1971) with fixed

order of report and extend the findings to letter stimuli
with increased demands upon recall.
The magnitude of the RVHF asymmetry with letter stimuli

was greater than in previous Type III studies using digit
stimuli (Hines and Satz, 1971). For example, in the com-
bined conditions, Ss recalled 33% more from the RVHF with
the letter trials as compared with 21% more from the RVHF
when the seven-digit trials were employed (Hines and Satz,

1971).
The increased magnitude of the RVHF asymmetry with
letter stimuli was also reflected in the frequency with
which Ss recalled more letters from this VHF. Twenty-eight

of the thirty Ss (93%) in the combined 165 msec. and 330
msec. conditions (Study I) recalled more letters from the
RVHF. Ninety-seven percent (97%) of the Ss in the combined
330 msec. conditions (Study I and Study III) recalled more
letters from the RVHF. A lower frequency of RVHF superi-

ority was found in all previous studies using the seven-digit









trials (Hines, Satz, Schell and Schmidlin, 1969; Hines and

Satz, 1971).
The overall mean percent recall (16.6%d) was consider-

ably lower than that found in previous studies (33.5%)

using fewer digit stimuli within each trial sequence (Hines
and Satz, 1971). However, while the larger number of letter
stimuli within trials increased the mnemonic demands of the

task, the magnitude of the VHF asymmetry also increased.
This effect is similar to that found with the Dichotic

Listening Test (Satz, 1967).
Decreasing presentation time.without altering inter-
stimulus interval had little effect upon either recall effi-

ciency or the VHF asymmetry. This suggests that perceptual
factors (forming an iconic image) at these slow speeds are

not responsible for the RVHF asymimetry. Hlaber (1970) has

previously shown that, across a wide range of stimulus dura-
tions (4 msec. to 200+ msec.), the duration of iconic images

appears independent of the duration of the original stimulus.
The effective duration of all such flashes, regardless of

the actual physical stimulus duration, has been shown to be

in the range of 200-250 msec. (Haber, 1970). Thus, decreas-

ing the presentation time (165 msec.) without altering the
interstimulus interval (330 msec.) would not alter the

effective length of each stimulus' iconic image and thus,
as shown, would be expected to have little effect on the
VHF asymmetry. Decreasing the presentation time (280 msec.)






65


allowed less timne to process the iconic images into short-

term memory (STM) before disruption by the subsequent stim-

ulus, i.e., the stimulus duration more nearly equaled the

upper limits of dark adapted iconic image formation. Both
recall efficiency and the VHF asymmetry decreased as back-

ward masking increased.

Serial position effects further reflect the role of

STM factors in the RVHF recall superiority. While mean

recall from each serial position was greater from the RVHF,

the magnitude of the RVHF asymmetry was greatest for those

letter stimuli most remote in time. This finding is con-

sistent with previous reports using the controlled fixation

paradigm with digit stimuli (Hines .and Sat-z, 1971) and

again suggests the role of central mediating factors in

this type of VHE asymmletry task ('Type III paradigm).


Study II
Results from Study II suggest that Ss had more diffi-

culty in the processing of unfamiliar non-verbal stimuli

(designs) in immediate serial presentation than in processing
verbal stimuli (letters) presented in the same manner.

Neither practice nor decrease in the rate of presentation

(Experiment I) had a significant effect upon increasing
mean correct non-verbal recognition from fixation (e.g.,

two designs). Designs that pilot Ss had suggested to be

more complex than letter stimuli had been eliminated from

the experimental designs. Yet, mean design recognition









from fixation was inferior 'to recall of the verbal stimuli

(86% of verbal trials had correct recall of five fixation

letters plus one VHF letter) at the same presentation speeds.

The demonstration of a VHF asymmetry with the design

stimuli appeared to be considerably affected by the task

difficulty. Data from Experiment I (Study II) had suggested

that using designs in the VHF while maintaining designs also
at fixation would have exceeded the limits of the recogni-

tion of non-verbal designs at.these speeds. Thus, with

designs in the VHF, digits were employed at fixation. With

only one VHF design and fixation digits, high recall per-
formance levels in both VHFs indicate that the task was not

difficult enough to produce a VHF asymmetry. However, with

only one VHF design but at a much faster presentation rate

(modified Type III paradigm), McKeever and Gill (1972) had
demonstrated a LVHF asymmetry. In the present study, in

order to keep the presentation rate consistent with that

used in the verbal studies (Study I, 330 msec.) and yet in-

crease the task difficulty, the number of fixation digits

and -VHF designs was increased. Increasing the recall

demands of the design task lowered the overall mean percent

correct and produced a significant LVHF recall superiority

(Study III).

Study III

The major test of hemispheric mechanisms underlying

performance on these VHF tasks was demonstrated in Study III.






67


The results showed a consistent double dissociation: the

asymmetries in VHIF performuances.varied as a function of the

type of stimulus materials. Ver'bal stimuli (letters) pre-
sented to the RVHF were recalled better than from the LVHF

and conversely, non-verbal. stimuli (designs) were recog-

nized better when presented to the LVHF than to the RVHF.

The within Ss experimental control is the strongest evi-

dence that the dual asymmetries are a function of the type

of stimulus material.

Letter stimruli.--Resu~lts from Study III replicate the

findings of~ Study I in demonstrating a RVHF recall superi-

ority with verbal letter stimuli and buttress the reliability
of this effect across Ss. Thle increased frequency of occur-

rence of the RVHF asymmetry in Study III (15/15) suggests

that the reduced frequency (39/45) observed in Study I may

have been in part due .to the reliance on the self-report of

Ss handedness. The differences in these frequencies suggest

the importance of controlling the unreliability of handedness

self-report (Satz, Fennell and Jones, 1969) as in Study III

in experiments from which inferences about hemispheric

dominance are to be drawn. Replication of serial order

effects were.also observed; that is, those letters most

remote in time produced the greatest VHF asymmetry.

Design stimuli.--Results from Study II'I with non-verbal

design stimuli suggest that hemispheric mechanisms probably
underlie the superior recognition of the LVHF: input; that is,









right hemispheric analyzers may be more specialized for
this type of visual-spatial analysis of stimuli with no

familiar verbal labels. This interpretation is compatible

with the results of multiple clinical studies of unilateral

brain injury in humans.

Although digits were employed as fixation stimuli on

the non-verbal task, it appears unlikely that the LVHF asym-

metry is a function of the fixation stimuli. Earlier studies

(Hines, 1968) employed more digits at fixation and produced

an RVHF asymmetry with digits in the lateral half fields.

In the present study there were fewer digits at fixation and

one would expect a similar RVHF asymmetry on this easier

task if the fixation stimuli were responsible for the asym-

metry. The finding of the LVH-F asymmetry is contrary to
this expectation and alternatively is most parsimoniously

explained in terms of the hemispheric differences in the

processing of the design stimulus material. Such an inter-

pretation is consistent with the findings of a LVHF superi-

ority with non-verbal stimuli observed by Fontenot (1973)

using a Type II paradigm and by Schell (1970) using a Type

III paradigm with block designs.

Analysis of serial position data suggests that the

sequence of the design identification (always subsequent to
correct recall of fixation stimuli) altered the direction

of the LViHF asymmetry only when identification was limited

to the second stimulus. The occurrence of an RVHF superi-

ority when recall was only from the second serial position









(most recent) suggests that at this slow presentation speed
directional scanning may take place on the terminal stimulus

in a trial sequence. Such an interpretation is consistent

with the most typical finding (Hines and Satz, 1971a;McKeever

and Huling, 1971; Parker, 1973) of less asymmetry in the

terminal serial~position with verbal stimuli. Nevertheless,
recall` o~f the most- remote design stimulus, either alone
with the second stimulus,produced a consistent LVHF asym-

metry and suggests that it was the mnemonic processing of
the more remote design stimulus that produced the LVHF

effect. Stimuli in the LVHF are transmitted via crossed and

uncrossed pathways most directly to the spatial processing

centers in the right hemisphere. It has already been shown

that impairment in right hemisphere functioning specifically

im airs mnemonic processing of spatial configural patterns.

(Goodglass and Peck, 1972).~

The preceding LVHF effect for non-verbal designs repre-
sents a successful demonstration of the special role of the

right hemispheric analyzers in the processing of spatial
configural patterns. Previous attempts at such an LVHF
have either failed to produce the effect (Hines, 1973%) or

have remained un~repl~icated. For example, the LVHF asymmetry

reported by Kimura (1966) has resisted several attempts at

replication. The more recent studies by Schell (1970),
Fontenot (1973), and Geffen, Bradshaw and Nettleton (1972)

have yet to be reported as replicated.






70


The present LVHF effect is particularly strengthened

by the reversal in the VHF superiority when verbal stimuli

(letters) are employed. Further-' recent evidence suggests
that the most common failure of previous studies to produce

this LVHF effect may result from the choice of experimental

stimuli with which to investigate this effect. This sug-

gestion is consistent with previous studies that have demon-
strated smaller RIVH-F asymimetries with less co~deaibl-e stimuli

(Bryden and Rainey, 1963) and suggest a major source of dif-

ficulty in previous studies that have failed to demonstrate

an LVHF superiority with "nron-verbal" stimuli.

The present non-verbal stimuli were modifications and
extensions of tactile stimuli previously used to assess

spatial configural deficits in right hemisphere injured

patients -(Butters, Barton and Brody, 1970). As such, the
stimuli are considerably less complex than those used by

Fontenot (1973) and yet do not have the limitations of the

Hines: (19736) stimuli which produced no VHF differences at

a much faster presentation rate. Subjects' descriptions

of the H-ines (197i) stimuli as "blobs" apparently indicated

that the designs were not easily seen as dissimilar. The

lack of easily identifiable distinguishable characteristics

at the fast presentation rate employed may have severely

limited this previous attempt to demonstrate an LVHF asym-

metry with design stimuli.









The lack of consistency in the LVHF asymmetry across Ss

(12/15) produced with the present stimuli suggest the diffi-

culty in generating a set of simple stimuli which maintain
low codeability or association value across Ss. The report

by one S that one design looked like "a Hebrew letter upside
down" suggests the S's associative skills that make truly

non-verbal stimuli difficult to generate.' The advantage of

this paradigm (Type III) as developed in this research is

the consistency of the RVHF 'verbal asymmetry (15/15) with

pre-selected dextral Ssagainst which to compare non-verbal
effects.

Analysis of the rank order correlations between VHF

performances on the two tasks (verbal and non-verbal) sug-

gests additional findings which may indicate how the pro-
cessing of verbal and non-verbal stimuli is related. The

lack of significant correlations between the two RVHF per-

formances suggests that performances on the two tasks are

not mediated by a single process and therefore not explain-

able simply in terms of different levels of verbal coding.

While there is no significant correlation between the

RVH~F performances, LVHF performances are significantly

related.. This difference may result from the ability to

process both types of stimuli (letters and designs) spatially
in the right hemisphere but an inability to process both

types of stimuli verbally in the left hemisphere. The in-
creased significance in the RVHF verbal and the LVHF non-









verbal correlation suggests that the verbal processing of

the left hemisphere may be a specialization of the proces-

sing of specific spatial familiar stimuli called verbal
stimuli. The non-significant relationship between verbal

performance in the LVHF and non-verbal performance in the
RVHF suggests that the dual VHF asymmetries demonstrated in

this present study do not result from the activation of

only one visual processing system. Instead, while there

appears to be a common spatial processing facility that is
at different levels for individual Ss across stimuli. types,

this common facility is over-ridden by the shift in VHF

superiority as a result of the type of stimulus material.
Indeed, VHF performances appear related most significantly

to the specific stimuli being projected to the hemisphere

primarily subserving processing of that type of stimuli;

i.e., when the non-verbal stimuli are projected to the right

hemisphere and the verbal stimuli are projected to the left

hemisphere.

In addition, recent research with reaction times (Geffen,

Bradshaw and Nettleton, 1972) suggests that the type of task

may be as important in the demonstration of hemispheric

asymmetry as the type of stimulus material. .Geffen, Brad-
shaw and Nettleton (1972) found faster processing of phys-

ically identical stimuli (letters) on a task of spatial

comparisons (physical identity) when directed to the right
hemisphere. Alternatively, they found faster processing of









stimuli with the same name (letters) on a task of verbal

label comparison when the stimuli were directed to the
left hemisphere. While these results are confounded by the

limits of the Type I paradigm previously discussed, they
are instructive in cautioning against interpretation of the

present results entirely in terms of the types of stimuli
material. The differential processing of the specific

types of stimuli material appears to play a major role in
the asymmetries produced. The present research was directed
toward developing a reliable methodology for assessing these

asymmetries. Further studies will have to be developed to
address the contributions of the type of task (e.g., physi-

ca-l identity.) upon the asymmetries demonstrated in the Type

III paradigm.
The finding of the double dissociation demonstrated in

Study III bears further scrutiny as it raises serious issue
with a prominent hypothesis of functional cortical asym-

metry. In particular, the attentional hypothesis of Kins-
bourne (-1970) suggests that concurrent verbal activities
bi-as attentional mechanisms in such a way as to produce an

RVHF asymmnetry independent of the type of stimulus material

e~mployed. The attentional hypothesis suggests that if an
S is engaged in language behavior prior or during a test
trial a left hemispheric activation will take place and that

accompanying that activation would be a directional bias to
the RVrHF regardless of the type of stimulus material (verbal









or non-verbal). This hypothesis suggests that such an

orientation would characterize "not only overt~ language use,

but also covert .(subvocal) language behavior including the

state of expectancy to verbal response" (Kinsbourne, 1970).

Initial support for this hypothesis (Kinsbourne, 1970) had

inadequate control of fixation and recent evidence with the

controlled fixation paradigm (Type III) has been discrepant

with the attentional hypothesis and earlier results. Schell

(1970), for example, demonstrated an LVHF asymmetry in the

presence of concurrent verbal activity.

The present: results are consistent with the findings

of Schell (1970) in demonstrating an LVrHF asymmetry that was

produced with five concurrent verbal activities. First,
the instructions for the design film were~ verbal and immedi-

ately prior to the film presentation. Second, presentation

of the verbal film always preceded the non-verbal film in

a single experimental session. Third, fixation stimuli

on the non-verbal film were digit stimuli which previously

had been shown to produce an RVHF asymmetry when presented

in the lateral VHFs. Fourth, the digit fixation stimuli

had to be attended to during and after the presentation of

the non-verbal stimuli. And fifth, verbal report of the.

fixation stimuli immediately preceded identification of the

non-verbal stimuli.

Nevertheless, with this concurrent verbal activity the

non-verbal des-ign film produced a significant LVHF recall






75


superiority. This asymmetry and its strength as measured

by -the number of Ss who exhibited the asymmetry (12/15)

appear: inconsistent with the attentional hypothesis and

appear more parsimoniously explained in terms of central

hemispheric processes.

Further, the attentional hypothesis suggests that

attentional mechamisms are involuntarily directed toward

the VHF (or ear) contralateral to the hemisphere dominant

for the class of stimuli (verbal or non-verbal) presented.

However, analysis of the errors at fixation on both the

verbal and non-verbal films suggests results at variance

with this hypothesis. Errors at fixation occurred most often

on those trials in which the class of stimuli were being pro-

jected to the hemisphere not dominant for that class of

stimuli. Indeed, since performance on the fixation tasks

w~as:: overall at such a high mean percent correct the dis-

tribution of the errors at fixation suggests that they were

not simply a function of the task difficulty. Rather, the

distribution of fixation errors suggests that attention to

the fixation stimuli was most often interrupted when Ss

tried to compensate for the fact that.the VHF stimuli were

not being projected to the hemisphere where they cou-ld be

most readily processed. The attentional hypothesis would

have predicted the opposite distribution.

Despite the methodological and evaluative advantages

in the control fixation paradigm (Type III), the present






76


results pose a number of unanswered questions. First, to

what extent are the VHF asymmetries demonstrated in the

present research a function of pelrceptual or mnemonic fac-

tors? While this question is unanswered, it is striking

that on both the verbal and non-verbal tasks the stimulus

most remote in time produced the largest percent of VHF

superiority. Any argument that the asymmetries are a func-

tion of perceptual factors would have to account for the

fact that the stimulus durations are more than eleven times

longer than those used by Fontenot (1973) in his modified

Type III study. Further', Haber'.s (1970) findings of success-

ful stimulus recognition at presentation rates down to four

msec. suggests that the present results can best be under-

stood not in terms of perception but in sterns of differen-

tial abilities to hold the stimulus.

Conclusions as to the differential laterality of mnemonic

functions processing of design stimuli are not without pre-

vious clinical and experimental evidence. For example, in

the processing of non-verbal information, Milner (1968) con-

cluded that, indeed, right temporal lobe lesions affect both

mnemonic and perceptual factors but that the perceptual

changes are very difficult to elicit. Wils on .(1.968) .has

also-suggested that both spatial configural memory and per-

ception are right hemisphere mediated processes. Iwan and

Mishkin (1969) have further shown that, indeed, the primary

focus of pattern discrimination is in the right hemisphere.

Such studies are consistent with hypotheses of functional






77


asymmetry that suggest the LV/HF design recall is a function
of the more effective processing in the right hemisphere.

Second, while mnemonic processes are implicated, to

what extent is the procedure itself a recognition or recall

task? Clearly, it is a recall .task in that the VHF report

is delayed beyond correct report of the intervening fixation

stimuli (fixed order of report). It is also the recall

demands from the more remote serial position which produced

the LVJHF asymmetry. On the. other hand, identification of

design stimuli is essentially a delayed recognition task in
that Ss choose from a visual display. The present data do

not resolve this issue. However, the development of the

Type III paradigm~~presents a good place to begin to separate
the effects of recall and recognition parameters on the VHF

asymmetries observed in this type' of task.
Third, to what extent are the design stimuli developed

in the present study indeed "non-verbal"? While this ques-

tion is unanswered, results from a replication study in the

process of data analysis suggest that this Type III paradigm
provides the first replicated demonstration of the double

dissociation in 1 F asymmetries. The replicability of the

paradigm wirll -allow further studies to tease out the. rela-
tionships between the non-verbalness of the designs and the

procedural tasks (e.g., recognition).

The primary significance of this present study lies in
its replication of the Type III paradigm with letter stimuli









and the extension of the control fixation paradigm to non-

verbal design stimuli. As such, the present study provides

a contribution in the development of a new visual paradigm

for studying central mechanisms in the processing of visual

stimuli. The Type III paradigm provides a methodology with

which to tease out central effects while controlling for the

limitations of the Type I and Type II paradigms previously

discussed. The present research is the first control fixa-

tion study that has demonstrated significant differences in

VHF recall superiority as a function of type of stimulus

material. Replication (verbal stimuli) and extension (non-

verbal stimuli) of the control -fixation paradigm make.- a

particular methodological .contribution in that this paradigm

hias previously been- shown to correlate with the Dichotic

Listening Test whereas previous tachistoscopic studies (Type

I and Type II) have not (Bryden, 1967). The pres ent~ data

suggest that this extended control fixation paradigm may

yield a sensitive behavioral index of functional hemispheric
differences in normal human adults.

Further studies employing this present methodology may

be addressed to parameters of VHF asymmetries associated

with specific differences in the type of stimulus.material

and in the type of procedural task. Some specific studies

are proposed:

1) a replication of Study III with a larger group of
dextral Ss to assess the effects of handedness and familial

right-handedness upon VHF recall asymmetries.









2) a replication of Study III with the non-verbal film

preceding the verbal film to assess the effects of fatigue.

and attentional set on the non-verbal task performance in

the present study.

3) a replication of Study III with sinistral Ss to
assess the effects of handedness and familiar left-handedness

on VHF performance.

4) the presentation of both verbal and non-verbal films

with slower presentation times and va-ried intrastimulus

intervals to assess: the relationship between stimulus dura-

tion, iconic imagery, and ?HF1I asymmetry.

5) the development of a new film in which similar ver-

bal and non-verbal trials are presented in a random fashion

in order to further contro-l attentional set.

6) the -development of another film with four letters
at fixation and three letters in the lateral VHFs in order

to compare the effects of letter stimuli independent of the

increased STM demands in the present non-verbal film.

7) the development of a similar non-verbal design film

using as stimuli the- designs used by Fontenot (1973) with.

tachistoscopic presentation. Such a film would offer the

possibility -of replicability independent of the particular

stimuli used in the present study and would provide a means

of evaluating VHF asymmetry in terms of stimuli codeability.






























APPENDIX 1

VERBAL STIMULI IN VHF AND AT FI-XATION,
STUDY I AND STUDY III








Subject #
VHF Trial Fixation
L 1 DBJGIT
R 2 E fiR
L 3 CPUSW
R 4 DPJGI
L 5 ~RTUTIT
R 6 CPUSW

L 1 KNQTE
R 2 EVNKY
L 3 EW187
R 4 TFTCY
L 5 STOT% I
R 6 ETG~ff
L 7 AYCWF
R 8 TFGOPF
L 9 XATUF
R 10 IEZTER
L 11 NTISTTF
R 12 XKVEY
L 13 ERIZTY
R 14 HCGETI
L -15 NPTED

R 16 1(NYE
L; 17 EVNKY
R 18 EWRMY
L 19 TFTGE K


Name
Handedcness:


VHF
RFACLE
XDLUN
XCRAS L
RFACL
177MUN
XRAFL
W'PB-S

;rTTIT

QPG JB
H-CAUCZ
LTTEKV
ESXXU
TINFY
RCNBI
HCUIJY

vqYGrA
GUZKBE
TNGCJ
RDTIN

cQBIR
1707J`B
WYTBSV

JTTIT

QYTPCJB
ITCATT






82


VHF Trial Fixation

R' 20 SXYODM

L 21 PJGOH

R 22 AYCWF

L 23 TFGOP

R 24 XATDF

L 25 M1E ZTR

R 26 NISDF

L 27 XKVEW J

R 28 BAZTY

L 29 HGEPL

R 30 NPYSO

L 31 KNQYE
R 32 EVNKY

L 33 EWRA1Y

Ri 34 TFIGK

L 35 SXODM

R 36 PJGOH

L 37 AYCWF

R 38 TF~GOP

L 39 XRTIUT

R 40 MZY

L 4 1 ` ISEif

R 4 2 XRVEY

L 43 BAZTY


VHF

LTEK(V

BSXUZ

IRNBT

RCNBI

HJLUW2Y

VQRGA
GUZ 2)]

TNOCJ

KD IUM ~


LWKJB

WTBSV

JIQZD

QPGJB
HCAUZ

LTE KV

BSXU2

TEREY

RCNBI








KDIUM


VHF Trial Fixation

R 44 HGEPL

L 45 97735

R 46 KNQYE
L 47 EVNKY

R 48 EWRRY

L 49 TFTGK

R 50 SXODI\

L 51 PJT;UR

R 52 AYTWF

L 53 TFGOjP

R 54 XXTID-E

L 55 MEZTR

R 56 NI~SD-F

L 57 XKVEW

R 58 BALTY

L 59 HGEP~L

R 60 NPYSO


VHF

cqsxrr
LIWKJB

'WTERY

IT TU

QFUIR
H-CAIE

LTEXV

BSXRJT

IRNWBT

RCNB I

HLUWrY

7 ~RGAE
GUZHB

TNOCJ

KDI;UM

CQSXR
LWKJB






























APPENDIX 2

NON-VERBAL DESIGN RECOGNITION DISPLAY,
STUDY II, EXPERIMENT 1




Recognition Display Number 17


~


Recognition Display Number 18


c~j






























APPENDIX 3

NON-VERBAL DESIGN RECOGNITION DISPLAY,
STUDY II, EXPERIMENT 2, AND STUDY III








Number 17


Number 18






























APPENDIX 4

NON-VERBAL DESIGN AND FIXATION DIGIT
ANSWER SHEET









Trial Fixation

1 72K

2 3VTT

3 1 7 2

4 2116

5 75

6 -V

7 TOT

8 T "

9 ITS'

10 ETT

11 873

1 2 K S'

13 68

1 4 5'T

15 "IT

16 976'

1 7 6T

1 8 29 U


Design








5 3


IT

2

-iT

1







27

17


VHF

R

L

R

L

R

L

R

L

R

L

R

L

R

L

R

L

R

L


Trial Fixation Design

19 9T

20 THZ 9

2 1 27617

2 2 7 50 3

2 3 T

2 4 V9 1 0

2 5 8"B V

2 6 ITY ~-

2 7 672' 2

2 8 BFTT Z

29 iT56 .-

3 0 `62~ Z

31 U' T

3 2 470" 2T

33 576' 17

34 T6T E

3 5 2'9-1 5

3 6 ~77 T 17


VHF

R

L

R

L

R

L

R

L

R

L

R

L

R

L

R

L

R

L















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