Title Page
 Table of Contents
 Biographical sketch

Title: Concurrent dual task performances of right-handers
Full Citation
Permanent Link: http://ufdc.ufl.edu/UF00099508/00001
 Material Information
Title: Concurrent dual task performances of right-handers a test of Kinsbourne's functional distance model
Physical Description: vi, 72 leaves : ; 28 cm.
Language: English
Creator: Bilak, Myron, 1951-
Publisher: University of Florida
Place of Publication: Gainesville, Fla.
Publication Date: 1981
Copyright Date: 1981
Subject: Performance -- Psychological aspects   ( lcsh )
Verbal behavior -- Psychological aspects   ( lcsh )
Motor ability -- Psychological aspects   ( lcsh )
Clinical Psychology thesis Ph. D   ( lcsh )
Dissertations, Academic -- Clinical Psychology -- UF   ( lcsh )
Genre: bibliography   ( marcgt )
non-fiction   ( marcgt )
Thesis: Thesis (Ph. D.)--University of Florida, 1981.
Bibliography: Bibliography: leaves 64-70.
General Note: Typescript.
General Note: Vita.
Statement of Responsibility: by Myron Bilak.
 Record Information
Bibliographic ID: UF00099508
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 - 000297311
oclc - 08375952
notis - ABS3684


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Table of Contents
    Title Page
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        Page ii
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    Table of Contents
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        Page v
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    Biographical sketch
        Page 71
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Full Text








This endeavor would have been all but impossible if

not for the support of many individuals too numerous to

mention individually. However, there are several indivi-

duals who provided me with additional support, prodding, and

that proverbial "kick in the ---" that finally made it pos-


First of all, I would like to express my gratitude

to Paul Satz who came to my rescue and whose ideas were the

groundwork for this doctoral dissertation. Secondly, my

sincerely thanks go to Eileen Fennell who willingly took

over my committee after Paul left and who had subsequently

put up with my diversions, distractions, and seemingly end-

less streams of delays. I also extend my thanks to Hugh

Davis and Warren Rice, who throughout this have waited pa-

tiently for the outcome of my dissertation and who, on more

than one occasion, have presented me with the proper per-

spective and attitude to continue forth. Special thanks are

also extended to Nathan Perry who initially gave me the

opportunity to develop my research skills, and who was in-

strumental in my decision to attend the University of Florida.

One final member of my committee who deserves extra special

thanks is Frank Sieka. Over the years he has become a close

and lasting friend. His role as teacher, mentor and friend

made the demands of graduate school easier to cope with.

Also, the countless dinners at his home kept me from starv-

ing when funds were tight.

One other person who deserves more than just honor-

able mention is Cynthia Belar. As both a teacher and friend,

she provided me with support throughout the program. Re-

spectfully, I would like to take this opportunity to thank

all of you collectively for being my role models, supporters,

mentors, and friends.

Lastly, I thank my parents, Wolodymyr and Jaroslawa

Bilak, for not giving me a first name as long as theirs.

Otherwise, I might still be filling out applications for

graduate school.


ACKNOWLEDGMENTS . . . . . . . . . .

ABSTRACT . . . . . . . .





INTRODUCTION. . . . . . .. .
Overview of the Problem . . . . 1
Laterality of Cerebral Functioning:
Historical Perspective . . . . 4
Anatomical Asymmetry within the Brain 7
Current Research Directives
in Cerebral Organization . . . 9
Cerebral Organization and
Interhemispheric Competition . . 16
Statement of the Problem. . . ... 19
Specific Hypothesis . . . . . 21

METHOD. . . . . . . . .. 22
Subjects. . . . . . . .. 22
Apparatus . . . . . . . 22
Procedure . . . . . . . 23
Dichotic Listening Task. . . . 23
Dual Task Paradigm I . . . . 24
Dual Task Paradigm II. . . .. 26
Analyses. . . . . . . .. 27

RESULTS . . . . . . . .. 28
Preliminary Analysis. . . . .. 28
Analysis of the Dual Task
Paradigm I . . . . . . 32
Analysis of the Dual Task
Paradigm II. . . . . . .. 35
Analysis of the Verbal
Fluency Data . . . . . . 38

Summary and Conclusion

. 45

REFERENCES . . . . . . . . . .




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



Myron Bilak

December 1981

Chairman: Eileen B. Fennell
Major Department: Clinical Psychology

The present study examines dual task performances for

both verbal and motor tasks. Specifically, the verbal task

required the subject to say as many words as he/she could

think of beginning with a specific target letter. The two

motor tasks consisted of a foot tapping and a finger tap-

ping task during which the subject was asked to tap a foot

or finger counter. The dual task condition required the

subject to perform one of the motor tasks simultaneously with

the verbal fluency task.

The following questions were addressed in the study:

(1) According to Kinsbourne's model, one would predict a

drop in finger tapping under conditions of concurrent ver-

balizations but not a drop in foot tapping which is mediated

by areas more distant from language centers; (2) In contrast,

an attentional or priming model would predict a drop in both

finger and foot tapping performances under concurrent ver-

balizations; (3) One might also predict that under conditions

of concurrent foot tapping and verbalization, verbal fluency

would be improved over baseline rates; (4) Finally, one

could also predict a relatively greater increment over base-

line for verbal fluency under foot tapping than under finger

tapping conditions.

Expected results were not clearly obtained. Decreases

in the respective rates occurred for the two motor tasks,

but they were smaller for the foot tapping task than for

the finger tapping task. The obtained results support the

premise of less interference between them as a function of

their distance. The verbal fluency data showed no signifi-

cant change in performance as a function of hand or task

condition. It is surprising in that research on concurrent

dual tasks shows a decrement in performance in both tasks

when the tasks are performed simultaneously. The current

results suggest that there is a unidirectional inhibitory

effect with verbal processing showing little or no inhibition,

whereas motor tasks are inhibited. Finally, one can also

partly invoke an attentional priming model in that the verbal

nature of the instruction may have primed the language hemi-

sphere and guaranteed the verbal over motor priority on



Overview of the Problem

Research in the area of the brain and its functions

has diversified into many branches of science. It has

united many diversely unrelated researchers in joining

their endeavors and tackle its secrets with a variety of

methods and approaches. From the humble beginnings and

early days of phrenology when every mother probed her son's

scalp to see if he was presidential material, to today's

complicated, highly technological bioassays of brain tissue,

the brain has been poked, probed, dissected, timed, and

stimulated by countless researchers. Thus it is not unusual

to find various methods employed in its study ranging from

anatomical dissection to radiographic analysis of x-rays.

The present study will center around the brain and its

different functions. Specifically it will focus on the topic

of hemispheric specialization and lateralization. Research

over the past century has supported the notion of dichotomous

functioning of the two cerebral hemispheres (Gescl-wind,1970).

Various researchers have shown that in general the left hemi-

sphere processes linguistic stimuli better, whereas the right

hemisphere processes various nonlinguistic visuospatial

stimuli better.

Within the past twenty-five years, the development of

various lateral perceptual stimulation techniques, i.e.,

dichotic listening tasks, visual half field procedures, and

dichotomous tactile stimulation, has allowed researchers to

better address the problem of laterality of function in

normal subjects. Prior to that, notions of cerebral later-

ality were based on the study of patients with known cerebral

lesions to either the left or right side of the hemisphere.

Observed deficits in behavior functions were attributed to

the site of the lesion and became in theory localized centers

for specific functions. This "classical" lesion approach

had its limitations, however, in that it did not directly

assess the function of the lesioned area, but, in fact,

inferred its function from the resulting observed behavior

which was mediated by the remaining intact brain. Further

complications to the "lesion" approach were recently identi-

fied by Whitaker (1978). In a series of topographical

studies done on epileptics with long-standing seizure foci,

Whitaker showed that these patients had grossly deviant ar-

rangements of sensory, motor, and language areas within the

left hemisphere. The observed cortical reorganizations of

functional space in these patients suggest a rather poor

subject population from which to base and develop models of

"normal" brain functioning and then generalize and attri-

bute them to a normal nonlesioned population.

Previously mentioned laterality tasks developed ori-

ginally by and borrowed from the area of cognitive psychology

have helped solve the inferential problems of the "lesion"

approach and allowed researchers to study brain functions

in normal populations. In a typical laterality task, the

subject is presented with some sensory stimulus to either

lateral side or both sides of the body and asked to make some

discriminatory decision about its occurrence. Thus in a

dichotic listening task, auditory stimuli are simultane-

ously presented to each ear via stereo headphones and the

subject is asked to recall the stimuli (usually words). In

a visual half field stimulation procedure, the subject is

presented tachistoscopically with visual stimuli to one or

both visual half-fields and asked to identify or recall the

stimuli. Similarly, dichotomous tactile tasks require the

subject to manually manipulate different three-dimensional

shapes or letters by the left or right hands and identify

them later.

Results of experimental studies utilizing the above

described procedures have shown that perceptual asymmetries

exist between the two cerebral hemispheres (Kimura, 1961;

Hilliard, 1973; Berlucchi et al., 1974; Braine, 1968;

Bryden & Rainey, 1963). Two differing models have been

proposed to account for these perceptual asymmetries.

Kimura (1966) presented an input transmission model which

postulates that sensory input is better processed by the

shorter direct pathways of the various sensory projections.

For this reason, verbal material is perceived better in

the right half visual field, and verbal right ear input is

better perceived than left ear input in the dichotic presen-

tation. Kinsbourne (1970), in contrast, states that observed

differences in perceptual asymmetries are the result of at-

tentional biases related to preponderant activation of one

hemisphere over the other as a function of the nature of the

subject's task. Thus in Kinsbourne's model, perceptual asym-

metries result when the presentation of verbal material in

a dichotic listening task creates an attentional bias to

the right, as this is congruent with the basic orientational

bias of the left hemisphere, allowing the subject to more

consistently attend to the right ear and thereby optimize

performance to the right side.

Recent research efforts have centered on the functional

organization of the brain and its relationship to concurrent

and competitive performance in simultaneous dual tasks

(Kinsbourne, 1978). Thus, the scope of this proposal will

be to address Kinsbourne's model of functional space as it

relates to cerebral organization and laterality. First,

however, a brief literature review will be presented en-

compassing past and current research perspectives in the

areas of laterality and cerebral organization.

Laterality of Cerebral Functioning:
Historical Perspective

A multitude of functions have been attributed to the

organ known as the human brain. Generally, it acts as a

huge clearing-house and processor of incoming information.

Similar to a computer, it has the capacity to not only codify,

analyze, and integrate data, but it can also act on it seem-

ingly instantaneously. What significantly distinguishes the

human brain from that of the lower primates is the relative

massive size and area of the cerebral cortex with its accom-

panying vast number of neural cells. Rough estimates place

a minimum of five million neural cells beneath each square

centimeter of surface cortex (Geschwind, 1974). Photographs

of human cortex show a highly convoluted, many times folded,

deeply fissured mantel that covers the underlying deep brain

structures in the cranium. The many fissures themselves act

to subdivide the cortex into lobes with the predominant mid-

brain fissure dividing the cortex into two cerebral hemispheres.

The presence of two cerebral hemispheres in the brain

has brought forth the concept of cerebral dominance. Cere-

bral dominance can best be defined by Geschwind (1974) as

follows: "One hemisphere may be said to be dominant for a

given function when it is more important for the performance

of that function than the other hemisphere" (p. 174). Evi-

dence for the phenomenon of cerebral dominance was first

shown by Broca (Lenneberg, 1967), who, in 1865, made the

discovery that a form of aphasia was the result of left uni-

lateral lesions. Wernicke (Lenneberg, 1967), in 1874, gave

further credence to the concept when he showed that forms

of aphasia in which loss of auditory comprehension were a

prominent feature were also the result of left unilateral

lesions. Again in 1891, Dejerdine (Lenneberg, 1967)

implicated left unilateral lesions for the loss of reading

and writing comprehension. Concurrent with this, observa-

tion of massive damage to the right hemisphere showed no im-

pairment in the language functions. This consequently lead

most people to believe that the left hemisphere was the domi-

nant one, primarily in terms of language functions, whereas

the right hemisphere was thought of as the silent or minor

hemisphere, dominant for nothing.

This concept of unilateral cerebral dominance has re-

cently been replaced, however, by one in which dominance is

more material specific, i.e., it differs according to differ-

ent functions. Thus dominance can be attributed to one hemi-

sphere for one function (i.e., left for language) and concur-

rently be attributed to another hemisphere for another func-

tion (e.g., right for visual spatial ability). As a result,

various significant differences have been observed in terms

of dominant function. Meyer and Yates (1955) showed that re-

call of verbal material presented in associative learning

tasks is impaired with lesions of the left temporal lobe.

Likewise, difficulty with verbal memory has been shown by

Milner (1954) to occur in patients with epileptogenic lesions

of the left temporal lobe. The right hemisphere in contrast

has been identified as dominant for spatial perception. Le-

sions within the right hemisphere have resulted in various

spatial deficits (Hebb, 1939; Patterson & Zangwill, 1944;

Piercy & Smyth, 1962; Warrington & James, 1967) as well as

deficits in constructional capacities (Griffith & Davidson,1966).

Evidence indicates that the right hemisphere is also domi-

nant for certain intellectual abilities such as music.

Luria (1963) presents a case study of a composer whose best

work was done after he became aphasic with a massive stroke

to the left hemisphere. Similarly, Milner (1962) reported

that following right temporal lobectomies, patients exhibit

marked deficits on musical and nonverbal auditory tests

with pronounced difficulties in comparison with tonal pat-

terns and judgment quality. Thus evidence for a bilateral

theory of cerebral dominance based on function organization

rather than unilateral dominance prompted Hecean (1962) to


The facts so far generated suggest that there
exists a specific symptomatology for each hemi-
sphere, without so far having the right to infer
from that the existence of particular functions.
It is a fact that the symptomatology is differ-
ent according to the hemisphere disturbed thus
obliging us to consider a certain functional
organization of the cortex that would be dif-
ferent for each hemisphere.

Anatomical Asymmetry within the Brain

Researchers having observed the functional differences

between hemispheres in man sought corresponding anatomic

asymmetries in the brain. Early researchers, namely Eber-

staller, Conningham, Shellshear, and Connally, noted that

the Sylvian fissure was longer in the left than in the right

hemisphere (Witelson, 1977). This was taken to indicate

that some region within the fissure was asymmetric. Later

researchers such as Pfeifer, von Economo, and Horn

(Witelson, 1977) identified the plan temporale located

within the Sylvian fissure as being larger in the left than

the right hemisphere. Von Bonin (1962) disclaimed, however,

these anatomical differences as being too trivial and of

insufficient magnitude to account for the marked functional

differences between the hemispheres and stated that no ana-

tomical differences were in evidence. Recent research ef-

forts by Geschwind and Levitsky (1968), using more refined

surgical techniques and anatomic measurements, showed that

in a sample of 100 brains, 65% showed a longer planum in the

left hemisphere, whereas only 11% had a longer right planum.

Teszner et al. (1972), using a different method of measure-

ment than Geschwind, in which they made molds of the temporal

plane and then obtained area measurements of the two-dimen-

sional projected planes of the molds, found similar results.

Likewise, Witelson and Paille (1972) observed a larger left

planum than right planum in the series of adult brains that

they examined. LeMay and Culebras (1972) looked at the cor-

responding vasculature of the brain in the Sylvian fissure

and found that the middle cerebral artery angled more sharply

on the left than it did on the right. The observed differ-

ences in arteriographic asymmetries in the whole brain speci-

mens showed a more highly developed parietal operculum (con-

sidered to be part of the central language area) on the left

than on the right.

In a review of the literature on anatomical asymmetry

in infants, Witelson (1977) notes that all of the studies

done showed a greater number of infant brains with a larger

left planum than the right. The overall percentage of speci-

mens having a larger left planum was 75%, which is comparable

to the 69% that is observed in studies of adult brains. In

light of the above data, she hypothesizes that there may be

a preprogrammed neural substrate for the left hemisphere to

be later specialized for linguistic functions.

Whether structural asymmetries within the brain lead

to later functional asymmetries in performance is a question

that is beyond the scope of this proposal to answer. How-

ever, the data do present strong inferential evidence that

the structural anatomical organization of the brain may ac-

count for later functional asymmetry.

Current Research Directives
in Cerebral Organization

The most clear-cut evidence for lateralization and

specialization of function and organization is seen in

persons who have suffered certain forms of brain lesions.

Damage localized to the left side of the brain often results

in some loss of language functions, whereas similar damage

to the right side leaves the functions of language intact.

According to Lenneberg (1967), time of onset of injury is

very important as a prognostic indicator of recovery of

function. For lesions occurring in the very young, either

during or immediately after the age in which language is

acquired, full recovery of function is obtained. In a

review of clinical cases, Lenneberg maintains that if

language had developed before the onset of the disease,

and if the lesion is confined to a single hemisphere, lan-

guage function will return if the child is nine years old

or younger at the time of onset. However, if onset of

brain injury, or if recovery of function is not yet ob-

tained by the age of puberty, aphasic symptoms will remain

and continue into adulthood. Basser (1962) looked at chil-

dren who sustained lesions during the first two years of

life, either to the left or right side of the head, and

found that in half of them the onset of speech was delayed,

whereas in the other half, language developed normally.

This distribution held true regardless which side of the

head the lesion was incurred. It seems that before the on-

set of speech, both hemipsheres are equipotential in sus-

taining language. This equipotentiality is apparently lost

after the onset of speech. Basser notes that after language

acquisition begins, and up to the age of ten, left-sided

lesions result in speech distrubance 45% of the time.

Other researchers, namely Sperry (1966) and Zangwill (1960),

likewise hypothesize that both cerebral hemispheres possess

equal potentials for language at least until four to five

years of age.

Evidence for lateralization of speech functions has

been found by others. Studies involving dichotic listening

tasks show that verbal or linguistic stimuli such as words,

digits, single syllables or nonsense syllables are reported

more accurately when presented to the right ear and hence

transmitted to the left hemisphere (Kimura, 1961; Shank-

weiller & Studdert-Kennedy, 1967). In contrast to this,

nonverbal or nonlinguistic stimuli, i.e., steady state vowels,

melodies, environmental sounds, tend to be processed more ef-

ficiently by the left ear--right hemisphere circuit (Chaney &

Webster, 1966; Kimura, 1964; Milner, 1962).

Hemispheric lateralization has also been demonstrated

utilizing dichoptic visual techniques. Kimura (1969, 1973)

found that verbal material is more readily identified in the

left hemiretinas--(i.e., right visual fields in either eye)

left hemisphere circuit, while the right hemiretinas--(i.e.,

left visual fields in either eye) right hemisphere system is

more specialized to process nonverbal stimuli, e.g., geome-

tric forms. Kimura postulates that right hemisphere mediates

those functions involving a spatial-nonverbal component.

Further evidence for support of Kimura's hypothesis

was presented by Hilliard (1973) and Berlucchi et al. (1974).

Hilliard reported significant differences in recognition and

recall between verbal material (i.e., trigrams) and nonverbal

material (i.e., faces) when presented to subjects' right and

left visual fields. Left visual field superiority was found

for faces, whereas right visual field superiority was found

for the trigrams. Berlucchi et al. modified the above para-

digm and looked at reaction times to the presentation of

verbal and nonverbal material to the left and right visual

fields. They reported a differential increase in reaction

times to letter and face stimuli dependent on the visual

field in which it was presented. A superiority of the right

visual field was found for letters, while a superiority of

the left visual field was observed for faces. Reaction times

to a patch of light did not exhibit any interfield differ-

ences between left and right visual fields.

Various researchers have attempted to establish elec-

trophysiological measures as correlates of hemispheric

lateralization. Buchsbaum and Fedio (1969) studied averaged

evoked potentials of verbal and nonverbal stimuli from left

and right hemispheres in normal subjects. They found that

the averaged evoked response waveforms for both sets of

stimuli were different from the left hemisphere than those

from the right. Averaged evoked responses to verbal stimuli

were also found to have shorter latencies when recorded from

the left hemisphere. Morrell and Salamy (1971) were able

to differentiate between evoked potentials produced by pho-

nemic sounds and pure tones. Amplitudes to the pure tones

were larger on the right side, particularly over the parietal

region. In contrast to this, the evoked potentials produced

by phonemic sounds were larger and more stable over the left

parietal region.

Task demands in regard to processing complexity can

enhance asymmetry between hemispheres as reported by Poon

et al. (1976). They reported an increased positive P2

component in the right hemisphere as compared to the left

hemisphere during a simple recognition task of tachisto-

scopically presented letters. This asymmetry was further

enhanced when task demands required more complex processing.

Gallin and Ellis (1975) compared the asymmetry of

averaged evoked potentials and the electroencephalography

(EEG) alpha function as indicators of lateralized cognitive

functions. They engaged the subjects in spatial and verbal

tasks while simultaneously presenting light flashes. Results

showed that the alpha ratio was lowered in the task engaged

hemisphere, i.e., spatial tasks lowered alpha frequency in

the right hemisphere, whereas verbal tasks lowered alpha in

the left hemisphere. Similar results were obtained by Dumas

and Morgan (1975) who compared a population of engineers and

artists on different tasks. They found no differences be-

tween occupations in terms of alpha asymmetry nor were there

differences as a function of task difficulty. However, dif-

ferences were observed in amount of alpha present within

the hemisphere that is dominant for a particular task. Thus,

alpha suppression was observed in the right hemisphere for

right hemisphere tasks, i.e., facial recognition and Nebes

ring test, along with alpha suppression being observed within

the left hemisphere for left hemisphere tasks, i.e., linguis-

tic and verbal material.

Recent empirical data have cast some doubt, however,

as to whether the lateralization of speech is as simplistic

as described previously. Whereas it is fairly well

established that the left cerebral hemisphere is usually

specialized for language functions in right-handed persons,

left-handers show far more variability for language to be

lateralized in the left hemisphere. Results of studies of

left-handers have been contradictory. Some studies have

found that strongly left-handed subjects can be divided into

two groups: one having left hemisphere language and the

other having right hemisphere language (Lishman & McMeekan,

1977; Satz, Achenbach, & Fennell, 1967). Likewise, Dee

(1971) reported that in performance on dichotic listening

tasks, strongly left-handed subjects showed left hemisphere

language control and weak left-handers displayed variable

language lateralization. In contrast, however, Knox and

Boone (1970) found that when the dichotic listening task

was made more difficult, performance of strong left-handers

was under right hemisphere language control.

Other confounding variables related to handedness and

cerebral organization that have been identified are the

presence of a positive history of familial sinistrality and

sex. Clinical and experimental studies of subjects having

a positive history of familial sinistrality show less depen-

dence upon the left hemisphere for language processing

(Hecean & Sauget, 1971; Hines & Satz, 1971; Subirana,

1964, Zuriff & Bryden, 1969). In a study done by Luria

(1969), he reports that recovery of language in aphasics

is likely to be more improved, regardless of the patient's

own handedness, if there is a left-hander in the immediate

family of the patient. In contrast, Briggs et al. (1975)

found that familial sinistrality has no outcome on language

processing, whereas others have shown that a positive history

of familial sinistrality may indicate more dependence rather

than less on the left hemisphere for language processing

(Newcomber & Ratcliffe, 1973; Warrington & Pratt, 1973).

Further confusion and contradiction have been found

in the few studies that have addressed sex as a significant

variable in performance differences related to hemispheric

asymmetry. However, in a review of the dichotic listening

literature, Lake and Bryden (1976) concluded that "studies

dealing with sex differences in dichotic listening are vir-

tually unanimous in showing greater laterality effects in

men than in women" (p. 144). Visual half tachistoscopic stu-

dies by Bradshaw, Gates, and Nettleton (1977), and Hannay and

Malone (1976) show that females tend to be less lateralized

than their male counterparts. Contrary to this, a signifi-

cant sex effect was found by McKeever and Van Deventer (1977)

who reported females having left hemispheric superiority in

visual and auditory processing of verbal stimuli, whereas

males failed to show any hemispheric asymmetry.

It appears then that several variables may affect or

mediate cerebral organization and performance asymmetry,

namely, handedness, familial sinistrality, and sex. As a

consequence, further research endeavors need to incorporate

these salient factors and allow for control of their effects

as they cannot be neglected.

Cerebral Organization and
Interhemispheric Competition

To this point the review of the literature has centered

on research studies examining subjects' performances of

singular tasks and their relationship to cerebral organiza-

tion. However, researchers have also focused on subjects'

performances on dual tasks to study the effects of cerebral

competition and facilitation. Studies have shown that a sub-

ject, when working at full capacity, will lose efficiency if

he is required to simultaneously perform a second task.

Usually the performance of both tasks is altered (Taylor,

Lindsay, & Forbes, 1967). Kinsbourne and Cook (1971) re-

ported that subjects engaged in verbal activity had lower

balancing times with the right hand, whereas the left hand

balancing times were higher and enhanced. Kinsbourne thus

proposed a model for this asymmetrical phenomenon which in-

corporates the following: In a dual task paradigm, the dual

task performance decreases to the extent that cerebral pro-

grams controlling the two tasks share the same functional

space. In this situation, the functional distance or space

between any two cerebral control centers decreases or in-

creases according to the extent to which they collaborate

on concordant tasks and to the extent they compete on dis-

cordant tasks. According to this model, if effector A can

be paired with either effector B (functionally close) or

effector C (functionally distant), then the AB combination

will more efficiently perform concordant tasks, whereas the AC

combination will more effectively perform discordant tasks.

Within the framework of this model, right balancing times

were depressed because the left hemisphere had to simultane-

ously program both speech and motor movement of the contra-

lateral hand (functionally close--discordant task), whereas

left hand balancing times were increased because motor move-

ments (discordant tasks) are programmed in the right hemi-

sphere (functionally distant).

Data for support of Kinsbourne's model were provided

by Hicks (1975) who found that increased phonetic difficulty

of the verbalized material increased the interference in

right hand performance. In contrast, performance of the

left hand was unaffected by the difficulty level of the

verbalizations. Likewise, Hicks also showed that when hum-

ming was substituted for the speech tasks, similar deficits

appeared in the right hand whereas no interference effects

were found for the left hand. In another experiment by

Briggs (1975), it was demonstrated that in a bimanual step

tracking task with a concurrent verbal task, the right hand

made more errors than the left hand. Hicks, Provenzano, and

Rybstein (1975) combined a motor sequencing task with a verbal

task and found an asymmetrical interference in the motor task

with the right hand showing more deficits than the left.

In contrast, however, Lomas and Kimura (1976) failed

to replicate the results obtained by Kinsbourne and Hicks

for either speech or humming tasks. Instead they found

symmetrical bilateral interference for both hands when

combined with the verbal and humming tasks. In an experi-

ment done by Bowers et al. (1978) in which a visuospatial

task was combined with a finger tapping task, performance

on the motor task was equally depressed for both hands with

no asymmetry in evidence. However, results from the simul-

taneous verbal tasks and concurrent finger tapping showed

asymmetrical interference in tapping performance with the

right hand being more depressed than the left.

In general then it appears that concurrent motor ac-

tivity performed simultaneously with varied verbal tasks

results in an asymmetrical performance deficit in the right

hand. However, extending Kinsbourne's theory further, one

can also hypothesize that some performance deficit would

occur in the verbal tasks when the subject was engaged in

right sided motoric activity. One can assume this on the

premise that discordant tasks performed by functionally close

effector centers would compete for locus control and have

an inhibiting effect requiring certain "time sharing" of

neural space. Some evidence has been shown that this in

effect does happen as Hicks et al. (1975) reported that

finger tapping depressed performance on a verbal memory task.

However, recently Bowers et al. (1978) found no decrements on

three different verbal tasks of varying cognitive difficulty.

The evidence to date implies that in a dual task in-

volving a cognitive verbal component combined with a motoric

activity, a one-sided interference effect is observed with

an asymmetrical depression of the motor performance. This

is not accounted for, however, by Kinsbourne's model of

functional distance, as it instead implies a mutual inter-

ference for tasks functionally close. This question conse-

quently needs further examination and will be hopefully ad-

dressed by this study.

Statement of the Problem

Kinsbourne's functional distance model predicts that

a concurrent verbal task will interfere with right-handed

performance more than with left-handed performance in those

subjects with left hemisphere speech. This prediction is

based on the premise that the right hand control center is

functionally closer to the left hemisphere speech center than

the left hand control which is contralaterally located in the

right hemisphere motor strip. Studies of hemispheric con-

nections likewise show that motor control for the feet fol-

lows a similar contralateral pairing, i.e., motor control of

the left foot is found within the right motor cortex and

motor control for the right foot is centered within the left

motor cortex. Specifically, the motor control center for

the right foot is located more medially along the motor cor-

tex than the motor control center for the right hand which

is closer to the speech center. Extrapolating Kinsbourne's

model further, the functional distance between the left-

sided speech center and motor control for the right foot

would be greater than the functional distance between the

left-sided speech center and the right hand. Likewise, one

could predict then that because of the greater functional

distance between the two control centers, less interference

in motor performance would be observed for the right foot

than for the right hand.

In order to test the above hypothesis a study will be

designed that will first attempt to replicate the previously

reported results of right hand performance deficits. Sec-

ondly, a paradigm will be designed that will effectively test

the hypothesis that the functional distance between the speech

center and effector control for the right foot is greater

(i.e., less decrement) than that of the speech center and

right hand.

Since the above results are expected to occur in right-

handers with speech lateralized to the left side, a dichotic

listening task originally developed by Satz and associates

(Fennell et al., 1978) will be employed to identify subjects

with left-sided speech centers. A handedness inventory will

also be used in conjunction to help in further identifica-

tion of subjects. This will help insure that only subjects

with a strong right hand preference and speech localized to

the left hemisphere will be selected.

A foot tapping device has been developed that will be

used to test the motor performance of the subject's foot

tapping skills. This task has been chosen as being the most

effective in activating that part of the motor cortex that

controls the foot. Likewise, it will allow us to measure

performance differences, if any, between the two contralateral

homologous limbs (left foot/right foot), and ipsilateral

limbs (right foot/right hand).

Specific Hypothesis

In this experiment subjects were asked to perform

simultaneously a verbal fluency task while either tapping a

finger board or a foot board. The hypothesis that was tested

included the following: First, according to Kinsbourne's

model, one could predict a decrease in finger tapping under

conditions of concurrent verbalizations but not a decrease

in foot tapping which is mediated by areas more distant

from language centers. Secondly, one would predict that

under conditions of finger tapping and verbalization, verbal

fluency rates would be larger for the left hand than the

right hand as there would be less interference effects from

the contralateral left-sided motor centers. Similarly, com-

parison of verbal fluency rates for foot and finger tapping

conditions would predict a relatively greater increment over

baseline for verbal fluency under foot tapping conditions

than under finger tapping conditions. Finally, and in con-

trast to the above, an attentional or priming model would

predict a drop in both finger and foot tapping performances

under the premise that verbal instructions presented by the

examiner would prime the subject's left hemisphere to action

at the expense of adjacent functional areas.



The subjects were 40 right-handed college students,

20 males and 20 females, with ages ranging from 18 to 25

years. Subjects were selected on the basis of having the

following qualifications: a) no family history of sinis-

trality, and b) a positive right-hand preference score +9,

(range -24 to +24) on the Briggs and Nebes Handedness In-

ventory (1975). Subjects were obtained from a pool of

undergraduates at the University of Florida, Psychology 201

students, whose participation in this study partially ful-

filled the requirements of this Psychology 201 coursework.


Two different apparati were used in this experiment:

the finger tapping board and the foot tapping pedal. The

finger tapping apparatus consisted of a metal level 3.75 cm.

long mounted in the upper center quadrant of a 20.3 x

17.5 cm. board. This lever was suspended approximately

2.54 cm. above the board and was attached to a decimal

counter that mechanically advanced each time the lever was

depressed. Similarly, the second apparatus, the foot tapping

pedal, consisted of a pedal in the shape of a shoe attached

at its base by a hinge to a board 450 x 330 cm. with a spring

on the underside of its toe raising it approximately 6.0 cm.

From the side of the pedal a 9 cm. dowel extended to and

came in contact with a metal level 3.75 cm. long mounted to

the left of the foot pedal. This lever was suspended 2.54 cm.

above the board and attached to a decimal counter. Whenever

the pedal was depressed, the dowel likewise depressed the

lever and the counter was advanced.


Dichotic Listening Task

Each subject was presented with a dichotic listening

task on two separate days approximately one week apart, in

which he was asked to recall groups for one syllable con-

crete words presented simultaneously to each ear. This

task had been developed by Satz and associates in prelimi-

nary pilot work done at the Neuropsychology Lab at the Uni-

versity of Florida. Forty-five different pairs of one

syllable concrete words, e.g., pipe/cone, were used as

stimuli. The 45 pairs of words were grouped into 15 test

trials, with each trial consisting of three pairs of words

being presented one to each ear at the rate of 500 msec.

per pair. Each trial, from onset to offset, lasted 1.5 sec.

followed by a 10 sec. intertrial interval. Stimuli, re-

corded earlier on Scotch Mylar Tape, were played on a Tann-

berg Stereophonic tape recorder and presented via Stennheiser

Stereophonic headphones to the subject. The subject was

seated at a table facing a blank wall. The subject's task

at the end of each trial was to say aloud to the examiner

as many words as he could remember from that trial without

regard for order of presentation or ear. At the end of 15

trials, the headphones were reversed and the 15 trials re-

peated so that words previously heard in the right ear were

heard in the left ear and vice versa. Prior to the testing

session, each subject was presented with five practice

trials to familiarize himself with the task. Scores were

the total number .of words correctly recalled on each trial

from each ear.

Dual Task Paradigm I

An experimental task developed by Bowers et al. (1978)

was used as the first dual task. Each subject was given a

preliminary finger tapping task consisting of four 10 sec.

trials using first the right hand and then repeated with

the left hand. Subjects were shown and instructed to tap

the lever as rapidly as possible with their index finger,

restricting movement to the proximal joint. The subjects

were asked to keep the wrist and remaining fingers still

while positioned on the finger tapping board. This was done

to familiarize the subject with the task. Following this,

the experimental session consisted of two baseline and one

dual task condition including the following tasks: a) finger

tapping alone (FT), b) verbal fluency alone (VF), and c) fin-

ger tapping and verbal fluency performed simultaneously (FF).

The baseline FT condition will consist of four 30 sec.

finger tapping trials as described above, alternating be-

tween right and left hands (RLRL or LRLR). Intertrial in-

tervals were 10 sec. long.

The baseline verbal fluency consisted of four 30 sec.

trials in which the subject was asked to say as many words

as possible beginning with a specified target letter identi-

fied by the experimenter. One of 12 letters (A, D, F, T, B,

P, etc.) was used for each of the four trials. Proper names

and their derivatives were not allowed. Each trial began

with the announcement of a specified target letter by the

experimenter and ended 30 sec. later. A tape recorder was

used to record the subject's responses for later scoring.

The dual task condition required the above described

finger tapping task and verbal fluency task to be performed

together. Each trial began with the experimenter present-

ing a target letter at which time the subject was asked to

begin tapping and generating words. Four trials were done,

alternating hands (RLRL or LRLR). Subjects were asked to

divide their attention equally between the two simultaneous


The Dual Task Paradigm I consisted of a total of 12

trials per subject, four per condition. Half of the base-

line trials (two FT and VF) were done at the beginning of

the session and the remainder at the end. Hand and letter

order were balanced across subjects and condition.

Dual Task Paradigm II

The second dual task was similar to the procedure

described above for Dual Task Paradigm I. Foot tapping

(FtT) was substituted, however, for the FT task. Likewise,

each subject was given a preliminary foot tapping task con-

sisting of four 10 sec. trials using first the right foot

and then repeated using the left foot (RLRL). Subjects were

shown and instructed to tap the pedal as rapidly as possible

with their foot, restricting movement to the tibial tarsal

joint. Following this, the experimental session consisted

of one dual task condition including the following tasks:

a) foot tapping alone (FtT) and b) foot tapping and verbal

fluency performed simultaneously (FtF). Verbal fluency

baseline data were used from data obtained in Dual Task

Paradigm I.

The baseline FtT condition consisted of four 30 sec.

foot tapping trials as described above, alternating between

right and left foot (RLRL). Intertrial intervals were 10

sec. long.

In the dual task condition, the subjects were asked

to perform the FtT described above and VF task previously

described simultaneously. Four trials were done alternating

feet (RLRL). Concurrently, each subject was asked to gener-

ate concrete words to a specific target letter. Throughout

the session, subjects were asked to divide their attention

equally between the two tasks. A tape recorder was used to

record the subjects' responses.

Dual Task Paradigm II consisted of a total of eight

trials per subject, four per condition. Half of the base-

line trials (two FtT) were done at the beginning of this

part of the session and the remainder at the end. Foot

and letter order were balanced across subjects and condi-



The proposed analyses were three-fold. First, test-

retest reliability were assessed for the dichotic listening

task over two sessions using Pearson Correlations of right

ear scores, left ear scores, and a difference score

(R-L/R+L). High correlation coefficients were added sup-

port to the reliability of the dichotic listening task as

a measure of speech laterlaity.

Secondly, separate analyses of variance were performed

with verbal fluency scores and respective motor tapping

scores as the dependent variables for both previously de-

scribed test paradigms I and II. Within subject factors

in Paradigm I were hand (R or L) and condition (baseline or

dual task). Similar analyses were performed for results

obtained on verbal fluency scores and foot tappings in

Paradigm II using foot (R and L) and condition (baseline

or dual task) as within subject factors.

Thirdly and lastly, comparisons were made between the

two Dual Task Paradigms I and II using R-L difference scores

for each condition. Mean test scores were examined for each

paradigm and T-tests run to check for significant differences.


The obtained results are presented in four sections.

The first section will primarily deal with evaluating the

reliability of the subjects' performances on the individual

tasks from Day 1 to Day 2. The second and third sections

concern themselves with motor performance data obtained on

test Paradigm I and test Paradigm II. These sections ad-

dress themselves to evaluating Kinsbourne's functional

distance model which predicts that a concurrent task will

interfere with right-sided performance more than with left-

sided performance in those subjects with left hemisphere

speech. The fourth and final section will present the

verbal fluency data and address itself to answering the

questions of whether motor performance finger tapping vs.

foot tapping has a reciprocal effect on verbal fluency as

expected by extrapolating Kinsbourne's model.

Preliminary Analysis

Three different sets of correlation measures were ob-

tained, one for each performance measure (ear, hand, and

foot) comparing Day 1 and Day 2. These were done to evalu-

ate the reliability of the test data from Day 1 to Day 2.

Table 1 presents the r-values for the dichotic listen-

ing task for both ears (R and L) and Days (1 and 2). A cor-

relation coefficient of r = .77 was obtained for the right

ear between Day 1 and Day 2 with a p value of .0001. Over-

all means for the R Ear Day 1 = 57.39 with a standard devia-

tion (S. D.) = 9.42. Overall means for the R Ear Day 2 were

62.47 with an S. D. = 9.93. A higher correlation was ob-

tained for the left ear from Day 1 and Day 2 with an r-value

.84 and a p value of .0001. The overall means for the L Ear

Day 2 were37.71 with an S. D. = 9.52. The mean for L Ear

Day 2 was 43.61 with an S. D. = 13.37. It is assumed that

the increased means for both ears on the second day of the

experiment were due to practice effects and increased famili-

arity with the task by the subjects. The above data indicate,

however, that the dichotic listening task was a reliable

measure and indicator of right ear dominance.

Table 2 shows the correlation coefficients for the

finger tapping practice trials on both hands between Days

1 and 2. A correlation coefficient of .72 was obtained for

right-handed finger taps between Day 1 and Day 2 with a p

value of .0001. The overall means for right finger taps

on Day 1 werel00.66 with an S. D. of 17.43. The overall

mean obtained for right finger taps on Day 2 was 102.58

with an S. D. of 13.97.

Correlation coefficients for the left hand on Days 1

and 2 were observed to be somewhat higher with an r-value

of .84 statistically significant at the p = .0001 level.


Table 1
for Ears:

Right Ear
Day 1

Day 1 vs. Day 2

Right Ear
Day 2




Left Ear
Day 1



Left Ear
Day 2




Right Ear
Day 1

Right Ear
Day 2

Left Ear
Day 1

Left Ear
Day 2

Table 2
Correlations for Finger Taps:

Right Finger Taps
Day 1

Right Finger Taps
Day 1

Right Finger Taps
Day 2



Left Finger Taps
Day 1

Left Finger Taps
Day 1

Left Finger Taps
Day 2



Day 1 vs. Day 2

Right Finger Taps
Day 2



Left Finger Taps
Day 2



The overall means for left finger taps on Day 1 were91.03

with an S. D. of 14.02. The overall means obtained for left

finger taps on Day 2 wereM = 95.05 with an S. D. of 12.53

Once again the observed slight increase in finger tap scores

from Day 1 to Day 2 on both hands can be attributed to prac-

tice effects and familiarity with the task by the subject

along with individual subject differences. Despite these

observed variances in the data, the relatively high r-values

suggest that the finger tapping task is a reliable measure

over time.

Analysis of the Dual Task Paradigm I

An analysis of variance was performed on the finger

tap performances from Day 1 and Day 2 which was collapsed

into one data pool. Four conditions were analyzed: Right

Hand alone (RH), Left Hand alone (LH), Right Hand combined

with Verbal Fluency (RHVF), and Left Hand combined with

Verbal Fluency (LHVF).

Significant differences were found to exist between

all four different experimental conditions with an obtained

F value = 72.27 and p = .001. Table 3 presents the results

of the analysis for the Finger Tap data. The means for

these conditions are presented in Table 4. Rate of finger

tapping was greatest for the RH alone conditions with an

obtained M of 288.30. The largest difference in observed

rates of performance was between the RH alone and the LH

combined with Verbal Fluency. The mean rate of performance


Table 3
Analysis of Variance for Finger Taps

Source DF F Value Pr F

Condition 3 72.27 0.0001

Sex 1 136.36 0.0-001

Subject (sex) 36 23.21 0.0001

Day 1 12.14 0.0006


Table 4
Mean Finger Taps per













Number of
Finger Taps





Number of
Finger Taps



Number of
Finger Taps



for the LHVF condition was found to be 238.88 which, using

Duncan's Multiple Range Test, was significantly different

at the .05 level.

Smaller absolute differences were found for the other

two conditions with the overall mean for RHVF (M = 262.21)

being greater than the overall mean of the LH alone condi-

tion (M = 254.50). Figure 1 shows the actual results for

the finger tap data drawn from research on concurrent tasks.

As one can see, both the actual data and expected data are

congruent with each other. Subjects performed better with

their RH's alone than with their LH's alone. These results

were as expected and reflect the subject pool of all right-

handers. Similarly, their performance dropped for both

hands when a concurrent task was added, namely, verbal


Analysis of the Dual Task Paradigm II

A similar analysis of variance was done on the foot

tapping performance from Day 1 and Day 2 as was done on

the finger tap data. Four conditions were analyzed also:

Right Foot alone (RF), Left Foot alone (LF), Right Foot

combined with Verbal Fluency (RFVF), and Left Foot com-

bined with Verbal Fluency (LFVF). Significant differences

were observed between three of the four conditions. The

F-value obtained was 18.66 with p = .0001. Table 5 pre-

sents the results of the analysis of variance for the Foot

Tap data. Differences were obtained between both alone






Figure 1. Finger Tap Rates


Table 5
Analysis of Variance for Foot Taps




Subject (sex)


F Value





Pr > F





conditions which were also significantly different from

the combined tasks conditions. There were no differences

between the tasks conditions for either the left or right

foot. Table 6 presents the means for the four different

conditions. As one can see, rate of foot tapping was

greatest for the RF alone condition with a mean of 230.89.

Foot taps dropped significantly when the nonpreferred foot

was used alone with an observed mean of 211.02. When a

verbal task was added, foot rates for the right foot were

lowered further to an observed mean of 199.56. Foot tap

rates dropped for the left foot also when a verbal task was

added, but the obtained results were not statistically dif-

ferent from those for the RFVF condition. Figure 2 shows

the means plotted out for the different conditions. Sub-

jects performed better with their preferred foot when en-

gaged in one task, but there were no differences between

feet when another task was added. These results are some-

what different from those obtained for the figer tap data

where all four conditions were statistically different.

Analysis of the Verbal Fluency Data

An analysis of variance was performed on the verbal

fluency data for both the hand and foot conditions. No

significant differences were found in verbal fluency rates

across the different conditions. An obtained F-value of .97

was found which was nonsignificant at the .05 level. This

is seen in Table 7 which shows the analysis of variance


Table 6
Mean Foot Taps per Trial









Mean Response





Mean Response



Mean Response







S 200





Figure 2. Foot Tap Rates


Table 7
Analysis of Variance for Verbal Fluency

Source DF F Value

Condition 4 0.97

Sex 1 0.10

Subject (sex) 36 26.01

Day 1 30.73

P 4 F






results that were obtained. Significant differences were ob-

served between Days I and II, but these are likely due to

practice effects that the individual experienced. Mean

values for the different conditions are given in Table 8

and presented graphically in Figure 3. The greatest drop

in VF rates is when the right-handed motor task is added.

The VF rate drops from 20.19 words/trial to 19.27 words/



Table 8
Mean Verbal Fluency Rates










Mean Response






Mean Response



Mean Response












Figure 3. Verbal Fluency Rates


According to Kinsbourne's theory of functional dis-

tance and shared space, it was expected that respective

rates of performance for concurrent tasks would not decrease

as their respective loci of control became more distant from

each other. Specifically, the model predicts a decrease in

overall finger tapping performance under conditions of con-

current verbalization but not necessarily a decrease in foot

tapping performance whose control is mediated by areas more

distant from language center than those controlling finger

tapping performance. In conjunction with this, the model

further predicts a greater decrease in finger tapping per-

formance for the right hand over baseline rates than that

of the left hand with concurrent verbalization. This is

based on the premise that the loci of control for the left

hand are contralaterally located and more distant from the

language centers than the control centers of the right hand

which are ipsilateral to the speech control areas. Like-

wise, a similar effect would be predicted for foot tapping

rates under conditions of concurrent verbalization with

right foot tapping performance being more adversely affected

than left foot tapping.

Further extrapolation of Kinsbourne's model allows

us to predict that verbal fluency rates will be better when

the subject is engaged in a motor task involving either the

left hand or foot as there will be less interference between

the two control centers with the contralaterally located

speech center. In contrast, verbal fluency rates for sub-

jects will be lower when the subjects are engaged in right-

sided motor tasks as their loci of control are more adjacent

and ipsilateral to the language center.

Expected results were not completely obtained, how-

ever. Specifically, decreases in the respective rates of

performance did occur within motor tasks under concurrent

motor and verbal task conditions, but there was no signi-

ficant change in rates for the verbal component of the dual

task paradigm. Partial support of Kinsbourne's theory was

illustrated in the differences from baseline rates for left

hemisphere controlled motor tasks (i.e., right finger and

foot tapping) were larger than those for right hemisphere

controlled motor tasks (i.e., left finger and foot tapping)

under dual task conditions (see Figure 4). One would ex-

pect this according to Kinsbourne's model in that motor

areas of control for left-sided motor tasks are located in

the right hemisphere and are functionally distant from

their counterparts in the left hemisphere. Subsequently,

when the two hemispheres are engaged in separate competing

tasks, there is less interference from the activation of

the left hemisphere in its performing a verbal task while

the right hemisphere is engaged a competing motor activity.


290 --

280 --

270 --

S 260 / Concurrent
.7 UF




Finger Tapping

230 --

220 --

210 --

200 Concurrent


Foot Tapping

Figure 4. Finger and Foot Tap Rates

Similarly, the argument can be put forth that the ob-

served large deficits in right-sided performance from base-

line rates were the function of having two competing tasks

originating from or controlled by neural areas that are

nearer to each other, i.e., within the same hemisphere.

In this case, both the verbal task and right-sided motor

tasks have their loci of control in the left hemisphere.

The nearness of the two loci of control results in inter-

ference effects between them whenever either of the two

centers is activated for function. Support for this hy-

pothesis is presented from EEG studies.

When a subject is about to perform a unilateral manual

movement, a slow negative potential shift is observed which

is maximally recorded over the contralateral motor cortex

(McAdam & Seales, 1969; Vaughn, Costa, & Ritter, 1968).

Likewise, McAdam and Whitaker (1971), who recorded surface

potentials from the left and right motor cortex (precentral

gyri) as well as the left and right inferior frontal regions

(Broca's area), found that during speech production, greater

electrical activity occurred over Broca's area than in the

corresponding area of the right hemisphere. In conjunction

with this, they also found more electrical activity in the

left precentral gyrus than in the contralateral right pre-

central gyrus. The latter finding suggests that activation

of the speech system (Broca's area) is associated with con-

current activation of adjacent motor systems in the left

hemisphere which may induce interference in that neural area.

Although it appears that related research lends it-

self to Kinsbourne's model, the results obtained in this

study do not completely support it. If Kinsbourne's model

was accurate, one would expect an improvement in verbal

fluency rates when the subject was engaged in motor tasks

which were controlled by motor centers more distant from

the language center. Thus, whenever a subject was engaged

in using either the left hand or foot which are both con-

trolled by right hemisphere motor centers, less interfer-

ence would be expected between the two functional areas

with a resultant increase in verbal fluency performance

levels. This effect was not observed, however, as verbal

fluency rates remained constant under all concurrent condi-

tions and were statistically nonsignificant (see Figure 5).

Why then do the obtained results lend only partial

support to the theory proposed by Kinsbourne? One answer

that immediately comes to mind is sampling error due to in-

divudual subject differences. In this particular study,

subjects were all strongly right-handed, exhibited right

ear dominance, and had no history of immediate familial

left-handedness, i.e., neither parent was left-handed.

Studies have shown that left-handers exhibit more varied

and different decrements than do right-handers in both uni-

manual and concurrent tasks (Lomas & Kimura, 1976; Hicks,

1975). Furthermore, left-handers showed less difference

between the ears for dichotic listening tasks that employ

verbal stimuli which include words, consonants, and digits


Motor Task



Figure 5. Verbal Fluency Rates




2: 19 4

(Bryden, 1970; Curry, 1967; Satz, Achenbach, & Fennell,

1967). In contrast to this, right-handers exhibit greater

right ear superiority for the same stimuli (Kimura, 1967;

Shankweiler & Studdert-Kennedy, 1967; Spellacy & Blumstein,

1970). If support for the model cannot be found in the

simplest design paradigm in which subjects are carefully

selected to maximize right/left differences, another ex-

planation must be sought.

A more probable explanation for the lack of support

of Kinsbourne's model is that which is proposed by Bowers

et a!. (1978). In a test of Kinsbourne's model, in which

they presented subjects with a dual task requiring them to

simultaneously perform a motor task and verbally articulate

words, they found that the verbal articulation task exerted

a bilateral asymmetrical interference on the motor task.

They also found that the motor task had no apparent recipro-

cal effect on the verbal articulation task. According to

Kinsbourne's model, however, one would expect a reciprocal

inhibitory effect on verbal articulation when the right hand

was engaged in a motor task. No such effect would be ex-

pected, however, when the left hand was engaged in a motor

task as its motor control strip is in the contralateral,

more distant, hemisphere from that of the left hemisphere

speech center. If, in fact, observed interference effects

for concurrent dual tasks are due to the overlap of func-

tionally adjacent neural areas, the nearness of the right-

sided controlling motor strip to the language center would

adversely affect the performance of a verbal articulation

task. No such effect was observed, however, by Bowers et

al. (1978). They consequently proposed that under dual

task conditions in which a simple motor task is in competi-

tion with a verbal task, a "one-way street" phenomenon is

present where priority is given to the language component

of the dual task.

This one-sided interference effect, in which motor

and cognitive tasks do not mutually interfere with each

other, but instead cognitive tasks have priority over motor

tasks, does not fit within the framework of Kinsbourne's

model. Such a proposition is tenable only if one assumes

a hierarchical structuring of systems in which higher order

functions, i.e., speech, interfere with lower order func-

tions, i.e., motoric movement, and there is no reciprocal

interference flowing the other way.

Hicks (1975) reported, however, a study supporting

Kinsbourne's model. In a series of experiments in which

subjects were asked to balance a dowel rod on either their

left or right index finger while simultaneously repeating

phrases, results indicated that concurrent verbalization

had a decremental effect on right hand balancing times.

He further showed that increased phonetic difficulty of the

phrases had a greater decremental effect on right hand bal-

ancing. In contrast to the results of Bowers et al. (1978),

increase phonetic difficulty caused more verbalization er-

rors on trials of the right hand but not with trials of the

left hand. In other words, a mutually reciprocating inhibi-

tory effect was observed with increased difficulty of the

verbal task.

Studies reporting effects of increased task diffi-

culty under concurrent task conditions show mixed and varied

results. Hicks, Provenzano, and Rybstein (1975) requested

their subjects to perform a sequential tapping task that

required either bilateral or unilateral synchronized move-

ments alone and concurrently while rehearsing verbal lists

of varying redundancy silently or vocally. The results in-

dicated support for an intrahemispheric competition inter-

pretation a la Kinsbourne in that the right hand leading bi-

manual performance and right hand unimanual performance

were interfered with greater than their left hand counter-

parts under conditions of concurrent verbal rehearsal.

They also found some left-handed interference which was not

predicted within the framework of the intrahemispheric com-

petition model. They subsequently proposed that obtained

results reflected the inherent difference of the tasks.

Whereas in the previous study (Hicks, 1975), dowel balancing

and simple phrase repetition were the two concurrent tasks,

their inherent cognitive demands were rather simple and not

as taxing as those in the latter study. They consequently

attributed the interference effects that were generalized

across hands to the increased cognitive demands inherent

within the tasks of sequential tapping and verbal rehearsal.

In the earlier study (Hicks, 1975), in which the interference

effects were lateralized as task difficulty increased, the

difficulty factor reflected a phonetic or speech production

component. In the latter study, however, increased dif-

ficulty appears to be due primarily to an increased cogni-

tive component which is inherent in the rehearsal of verbal

lists and in which a greater amount of cognitive process-

ing is involved than in the continuous repetition of short

phrases. Similarly, they surmised that sequential finger

movements require greater cognitive demands in that correct

sequencing involves a mediating memory component that is

not present in a-simple dowel balancing task.

Other studies do not show, however, that increasing

cognitive demands of the concurrent task will necessarily

result in a generalized though asymmetrical decrement in

hand performance. In fact, Lomas and Kimura (1976) showed

that a bilateral interference effect was seen in simple

finger tapping and concurrent verbalization, whereas on a

more complex finger sequencing task combined with verbali-

zation, only right-sided interference effects were observed.

They further showed that right hand performance was also

disrupted not only by sequential taps but also by a se-

quential arm tapping task, where only gross motor movements

were required to change the location of the arm from one

location to another. They differentiated their sequential

tapping task into more than just a repetition of the same

discrete movement as one sees in a straightforward finger

tapping task. In their finger tapping sequencing, the

subject was required to use different fingers on different

key locations and all done in rapid sequence. Since the

same lateralized effect in right hand performance was seen

in both the sequential finger tapping and sequential arm

tapping, they proposed that the effects are due to the

rapid positioning of a limb, or parts of a limb, in which

there is minimal visual guidance. They went on to hypothe-

size that the observed effect is not merely the result of

concurrent processing within the same hemisphere but rather

it is the result of the degree of functional similarity of

the different competing systems within the hemisphere.

Thus, it is the degree of congruency of two competing motor

systems within the same hemisphere than produce lateralized

performance effects.

Lomas (1980) repeated in part his previous experiment

(Lomas & Kimura, 1976) and added the independent variable

of varying visual feedback of the subject's performance.

His results showed that right hand interference effects

were only seen when the subjects did not receive any visual

feedback and could not rely on visually guiding their limb

or digit positioning. In contrast, when subjects had re-

course to visual feedback, speaking failed to selectively

disrupt right hand activity and, in fact, disrupted left

hand performance. Although Lomas failed to account for

the disruption to left hand performance when visual con-

trol was present, he nevertheless hypothesized that intra-

hemispheric competition is only present for certain motor

tasks and only when these tasks are under the control of a

specific cerebral motor system.

Other researchers, in trying to test Kinsbourne's

model of intrahemispheric competition, devised experiments

that utilized tasks specific to and presumably localized

to the right hemisphere. McFarland and Ashton (1978b)

utilized a visuospatial concurrent task (i.e., right hemi-

sphere controlled) to test whether the obtained results

would be reversed from those obtained with a concurrent ver-

bal task (i.e., left hemisphere controlled). They hypothe-

sized that if verbal tasks lead to a right-handed performance

decrement, then a visuospatial task should cause a decrement

in left hand performance. They found that, in fact, such an

effect was observed. When subjects were asked to perform

a memory task involving shapes in conjunction with a finger

tapping task, left hand performance was disrupted, whereas

right hand performance was not disrupted. Although such

results tend to support Kinsbourne's intrahemispheric compe-

tition model, McFarland and Ashton instead chose to inter-

pret it in terms of an attentional bias model also proposed

by Kinsbourne (1970). An attentional model suggests that

lateralized cerebral activity biases attention to the contra-

lateral side of the body and would consequently interfere

with a task performed on that side. Consequently, it is ex-

pected that a concurrent verbal task would bias attention

to the right side and disrupt right-handed performance. Like-

wise, the visuospatial task would bias attention to the left

and subsequently disrupt left hand performance.

Another experiment utilzing a visuospatial concurrent

task was performed by Hellige and Longstreth (1981). They

asked their subjects to simultaneously tap a telegraph key

while solving a block design problem from the Weschler In-

telligence Scale for Children-Revised (WISC-R) using the

hand. Results indicated that decrements in performance

were greater for the left hand than for the right hand.

The obtained effect was opposite of that in which the con-

current task was a verbal one. They summarily concluded

that when the concurrent activity is primarily known to in-

volve the right cerebral hemisphere, observed interference

is greater for the left hand than for the right hand on a

unimanual task.

This effect is not as clear or consistent, however,

when a verbal component is employed in the solution of the

visual spatial task. Bowers et al. (1978) looked at the

effects of a recognition task believed to be subserved by

the right hemipshere and is nonverbal in nature on concur-

rent tapping. They found that both right- and left-sided

tapping were bilaterally and symmetrically disrupted with

concurrent visuospatial processing. They suggested that

despite the nonverbal nature of the task, subjects may

have nevertheless verbally tagged the faces resulting in

bilateral processing of the task. Similarly, even if the

faces were processed by the right hemisphere, their pro-

cessing need not necessarily overlap with the motoric pro-

grams of the same hemisphere for control of the left hand.

Contradictory results were also obtained by Johnson and

Kozman (1977) who failed to find lateralized effects on fin-

ger tapping when employing a musical task which likewise is

allegedly subserved by the right hemisphere.

It is apparent that previous studies have provided

numerous explanations for the varied and conflicting re-

sults obtained from experiments on concurrent tasks. The

fact that no reciprocal inhibitory effect was found in

this study does not necessarily refute Kinsbourne's theory.

If one accepts the hypothesis of a hierarchical structuring

of control in which interference effects are one-way, the

present obtained results lend themselves to that interpre-

tation. However, if one examines the trend of the data

across all four concurrent tasks, one sees that even if

significance was not attained, the greatest disruption in

verbal fluency occurs for the right finger tapping condi-

tion. Furthermore, the trend in the data shows that the

further the motor control center is from the left speech

center, verbal fluency approaches baseline rates.

A reciprocal inhibitory effect may not have been ob-

tained due to the lack of a significant demand component

in the verbal task. Although the verbal fluency task used

in this study is inherently more difficult than the repeti-

tion of a simple phrase, it is not as difficult as that of

a task requiring a memory component. Subsequently, if the

task demand was not cognitively stringent enough, no recipro-

cal inhibitory effect would be expected.

The results obtained on the concurrent foot tapping

and verbal fluency task are somewhat surprising. A bi-

lateral though asymmetrical interference effect was ob-

served on foot taps. It was expected that left-sided foot

tapping would not be adversely affected by a concurrent

verbal task as the motor control for left-sided foot tap-

ping is furthest removed from the speech center. An argu-

ment can be put forth that the motor control center for

feet is less lateralized than that of the speech center,

and subsequently the left hemisphere exerts bilateral con-

trol over the neuromusculature system for the left and

right feet. Such an explanation is tenable if one assumes

that the task demands were harder for the foot tapping task

and concurrent verbal processing than those for either task


The verbal articulation task required the subject to

use a specific target letter and generate a list of words,

all of which required the subject to begin with that target

letter. The demands for the particular task require not

only a simple vocalization of a word but also require the

subjects to actively scan and sort out targeted words from

their preexisting vocabulary source. In terms of the at-

tentional model, this implies that both hemispheres are

being used to process the concurrent task. Subsequently

there would be no left or right attentional biases that

would cause a differential disruption of manual perform-

ance. This assumes then that the biasing characteristics

are not due to the characteristics inherent in the task as

the task was kept constant but more likely on the strategy

employed by the subjects to perform the task. In this

case, the degree of the memory load for the verbal fluency

task caused the subjects to focus their attention to that

task and thereby neglect or decrease the involvement of

the right hemisphere in the left foot tapping. The fact

that the left foot tapping was not disrupted, however, as

greatly as that of right foot tapping can also be explained

via a functional distance model. This implies that the

right hemisphere motor control center for the left foot

was less adversely affected than that of the more adjacent

left hemisphere motor control center of the right foot.

Another interpretation for the obtained results may

be that of Lomas and Kimura (1976) who proposed a motor

theory of disruption. They propose that performance of a

verbal task may make use of neural mechanisms that overlap

with those neural mechanisms of the left hemispheres which

are associated with controlling rapid repositioning of the

limbs. Consequently, a verbal task is likely to disrupt

concurrent foot performance because the neural units for

controlling right foot positioning and speech are closer

than those controlling left foot positioning and speech.

However, with the increased memory for the verbal task, the

resulting verbal output is likely to involve more diffuse

neural activity and thereby overlap with the neural system

controlling the rapid repositioning of both left and right


Summary and Conclusion

In summary, one can see that the results of this study

do not entirely lend support to Kinsbourne's model of func-

tional distance and shared space. If, in fact, the model

was completely accurate, two different main effects would

have been clearly obtained. First, an asymmetrical de-

crease from baseline rates would be seen in right-sided

finger and foot tapping tasks during concurrent verbaliza-

tion. Secondly, verbal fluency rates, in turn, would be

asymmetrically decreased by motor task conditions, speci-

fically more so when control of those tasks is centered in

the left hemisphere. The first main effect was obtained

and found to be statistically significant. The second ef-

fect, however, was not found although a trend in the data

suggests that further research and refinement in techniques

may lend support to its basic premise. A plausible explana-

tion that may account for the results of this study can be

presented as follows.

The two hemispheres of the brain are structurally pro-

grammed for differential activation dependent on stimulus

input and task demands. Thus, a task requiring a subject

to tap a keyboard with the left index finger activates the

motor strip in the right hemisphere. Similarly, a verbal

stimulus activates the language center within the left hemi-

sphere. In conjunction with this, activation of a functional

neural system may cause activation of other adjacent neural

system may cause activation of other adjacent neural systems

because of their proximity. Since neural efficiency is some-

what dependent and limited by the availability of informa-

tion storage and processing capabilities, priority for a

given task is likely to be allocated when two separate tasks

are performed simultaneously. This allocation of priority

may be preprogrammed and based on a hierarchical organiza-

tion of neural systems in which higher cortical functions

(i.e., language) subsume simpler cortical functions (i.e.,

digit tapping). This inherent supremacy of higher cortical

functions, however, can be modified by such variables as

the complexity of specific task demands, a subject's cogni-

tive set, and stimulus specific attentional biases. In

the present study, verbal fluency rates did not significantly

change as a function of motor task conditions, as was pre-

dicted. One possible explanation is that there was greater

activation of the left hemsiphere due to the verbal nature

of the task. This allowed and resulted in the language

center controlling a greater percentage of the total neural

efficiency of the brain and thereby allocating greater at-

tention to, and better performance of, the verbal task.

Although the above explanation presents an alterna-

tive to Kinsbourne's model, the reason for lack of support

of his model may have been due, in part, to various in-

tangible factors, some of which are methodological in na-

ture. Laterality studies have always been plagued by poor

psychological methodology as well as lack of specification

or standardization of treatment parameters. Laterality re-

search has failed to make a distinction between direction

and degree of laterality. Both imply similar constructs

but are vastly different when used in the literature.

Similarly, there is no unambiguous description of what is

meant by the term "bilateral representation." If valid

research is to be done in the area of neuropsychology,

these issues need to be addressed in future research stu-

dies or otherwise our research efforts will be similar to

that of the all too familiar parable of the four blind men

standing around an elephant and basing their separate "views"

of what the object is in front of them on their own tactile

sensing experience.


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Myron Bilak was born on September 23, 1951, in Lorain,

Ohio,and subsequently spent the next 17 years of his life

there doing what most little boys do while they are grow-

ing up. He experienced the usual traumas: getting his

first kiss from a girl other than his mother, his first day

in kindergarten, and the day he struck out in the bottom

of the ninth inning with the tying run on third base. Some-

how he survived all of this, made it through adolescence,

and successfully completed high school. He went on to col-

lege, attending Case-Western Reserve University, from which

he successfully graduated in 1973 with honors in psychology.

For a year he explored other avenues other than school and

became involved in the world of full-time employment as a

research assistant, part-time waiter, and part-time child

care worker.

After a year of soul searching and exploring career

options, he left cold and cloudy northeastern Ohio for the

warm and sunny climate of north central Florida to pursue

his degree in clinical psychology. Little did he know then

that it would take more time than he expected to success-

fully complete what he had started. Finally after some

seven years, he is ready to begin on a new direction. What


that will be is yet unbeknownst to him, yet he is sure that

it will be as exciting and challenging as the years before.

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

Eileen B. Fennell, Chairman
Assistant Professor of
Clinical Psychology

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

Hugh C. Davis, Jr.
Professor of Clinical Psychology

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

Nathan W. Perry, Jr.
Professor of Clinical


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

Warren J. R' e
Associate PVofessor of
Clinical Psychology

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

Frank L. Sieka
Associate Professor of
Rehabilitation Counseling

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

December, 1981

Dean, College of Health
Related Professions

Dean tor Graduate Studies and


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