The Effect of Concurrent Manual Activity on the

The Effect of Concurrent Manual Activity on the Dichotic Listening Performance of Boys with Learning -

Disabilities

Sharon A. Cermak Laird S. Cermak

Threegroups of learning-disabled children, defined according to their Wechsler Intelligence Scalefor Children (WISC) profiles, and one normal control group, weregiven both a standard dichotic listening task and a dichotic listening task performed concunently with a manual tapping task. Learningdisabled children who showed no dispan'ty in their verbal and performance subscale scores on the

WISC demonstrated a r g h t ear preference under standard testing and when tapping with the left hand, but not the r g h t , which was nearly the same pattern as that obtained by the control group. Learning-disabled children whose verbal WISCscore was at least 15 points lower than their performance demonstrated a right-ear preference only when tapp'ng with their left hand. Finally, learning-disabled

Sharon A . Cermak, M.S., O T R , is a n Assistant Professor i n Occupational Therapy at Sargent College, Boston University, and a doctoral candidate in special education at Boston University.

Charles Drake, Ed.D., isfounder and Headmaster of the Landmark School for Children with Learning Disabilities. He is also a n Associate Professor at Sargent College.

Laird S. Cermak, Ph. D., is a research psychologist at the Boston Veterans Administration Hospital, and a n Associate Professor at Boston University School of Medicine and Sargent College. I n addition, he serves as Research Director at the Landmark School for Children with Learning Dzia bilities.

Charles Drake Rebecca Kenney

Rebecca Kenney is the director of motor training at the Landmark School and a research assistant at the Language Development Research Center.

children who had high verbal, low performance WISC fn-ofiles showed no ear preference under any conditions. These results were interpreted as indicating that these three types of learning-disabled children are dqferentially lateraked and dqferentially affected by thefan'litory-inhibitory effects of concurrent hemisphen'c activities.

T

he concept of hemispheric specialization originally came from research in aphasia where it was discovered that the two cerebral hemispheres did not have equal potential for language but that speech and language were localized in the left hemisphere. Since these original studies were made, in the late 1800s, other investigations of adult braindamaged patients have demonstrated that several behavioral functions are distributed between the hemispheres in an asymmetrical manner. The tendency for one hemisphere to be dominant for certain iunctions has been termed hemzipheric specialization. In general, the left hemisphere has been found to be spe-

The American Journal of Occupational Theralby 493

cialized for language, whereas the right hemisphere has been found to be specialized for spatial functions, melodies, and music. . Within the last 20 years, there has been renewed interest in the investigation of hemispheric specialization. In the past, the study of hemispheric specialization depended upon finding patients either with unilateral brain injury from strokes, gunshot wounds, or tumors, or patients who had sectioning of the corpus callosum. However, since the 1950s, techniques have been developed to enable the study of hemispheric specialization in norpal as well as in brain-damaged subjects. One such technique is dichotic listening. In the dichotic listening technique, an individual wears a set of headphones and is presented simultaneously with a different auditory stimulus to each ear. The individual is then asked to report what was heard. Typically, when the competing stimuli are linguistic (digits (numbers), words, or other speech sounds), a right ear advantage is shown ( 1-3)-the individual reports 494

that more numbers were presented to the right ear than to the left ear. Conversely, when the stimuli are nonverbal, such as melodies, or environmental sounds such as a horn, vacuum cleaner, or dog bark, a left ear advantage is shown (Kimura, 3, 4). The most frequently cited explanation for these different ear superiorities is that the contralateral quditory neural pathways from the ear to the cerebral cortex are more efficient than the ipsilateral connections. Thus, for normals, the right ear superiority for processing verbal material supports the finding of hemispheric specialization for language in the left hemisphere; whereas the finding that more nonlanguage sounds that were presented to the left ear are reported supports the notion that the right hemisphere is specialized for processing nonverbal material. The first developmental study of hemispheric specialization in the normal brain using the dichotic listening paradigm was performed by Kimura (5). Using digits as stimuli, Kimura reported a right ear superi-

September 1978, Volume 32, No. 8

ority for children as young as four years of age, suggesting that language is already lateralized in the left hemisphere by that age. Other studies have shown that a right ear superiority for verbal material might exist even earlier: in three-year-old children studied by Nagafuci (6) and Ingram (7), and in 67-1/2 percent of two-and-one-half-yearolds tested by Bever (8). Interestingly enough, however, environmental conditions and one's sex were also found to affect the age at which hemispheric specialization is present on dichotic listening tasks. For instance, Kimura (3) found that boys from lower socioeconomic backgrounds did not show a right ear effect until the age of six, and Geffner and Hochberg (9) reported that children from low socioeconomic backgrounds did not show significant right ear effects until the age of seven. This means that a lack of hemispheric specialization at certain ages does not imply the existence of brain damage in the child, but rather, may be indicative of a maturational lag in the development of this specialization (see also Satz and Sparrow (10); Zurif and Carson (11) ). The possibility that a maturational lag in the development of hemispheric specialization might exist for some children leads to the further suggestion that, since reading is known to be a linguistic skill, developmental reading disabilities might stem from faulty or incomplete lateralization of the language functions (12). Several investigators have already shown that poor readers do often fail to show normal right ear superiority for verbal stimuli presented dichotically. For example, Taylor (13) found that boys with reading problems made relatively more left ear choices than boys with normal reading skills, and Zurif and Carson (11) found a slight trend favoring the left ear in a read-

measure of dichotic listening performance among children with Table 1 learning disabilities was explored. Although researchers question whether handedness is a reliable Mean lQ for the Nonnal and Leamlng-Dlsabled SubJects measure of speech and language repGroup Full Scale Verbal Performance resentation, it is generally agreed that there is a close relationship beLV-H P 101.31 91.81 111.06 tween language and motor activity. 108.13 116.27 97.00 HV-LP Kirnura (18) has shown that speakV=P 100.37 101.44 99.25 ing is strongly tied to other motor CONTROL 110.06 behaviors as evidenced by greater The Wechsler Intelligence Scale for Children was given the learningdisabled submanual gesture activity of the right jects; the OLMAT test was was used for the normal controls. hand during speaking than during nonspeaking activities. Since, in right-handed adults, this manual ing disability group. Kawar (14) also such as spelling and reading, thus in- gesture activity is almost always asfound that good re,aders have a sig- dicating a possible maturational lag sociated with the right hand rather nificantly greater right ear effect of the left hemisphere. This suggests than the left, Kimura suggested that than do learning-disabled children. that the Low Verbal-High Perform- activation of speech system in the left However, other similar investigations ance learning-disabled children hemisphere is often associated with have reported somewhat disparate might be more likely candidates to concomitant activation of certain results on this issue. For instance, demonstrate a lack of right ear su- other motor systems in that hemiBryden (15) found a right ear advan- periority on a dichotic listening task. sphere. She proposed that the intertage for both normal and reading- If this is true, then it might account action between speaking and manual disabled children, although the dif- for the differences in left hemispheric activity is due to an overlap between ference between ears was greater for specialization found in the dichotic the systems controlling speaking and the good than for the poor readers, listening studies performed with those controlling certain hand movewhereas Yeni-Komshian and others learning-disabled children since ments, specifically movements of the (16) found equal right ear advantage these studies did not take the child's contralateral right hand. This makes for both good and poor readers. WISC profile into account. Conse- anatomical sense since Broca's area, Thus, the evidence, supporting a quently, the present investigation ex- which is responsible for expressive theory of maturational lag in hemi- plored the existence of hemispheric speech, is anatomically close to the spheric specialization among learn- specialization unthin three groups of area of the motor cortex responsible ing-disabled children does exist, but learnzng-disabled children: Those for hand movement. Increased rightcontradictory evidence must be con- with Low Verbal-High Performance handed gesturelike activity during sidered. subscale scores (a 15-point or greater speaking has also been found to exist One possible e~planationfor these spread) on the WISC; those with a in preschool children as young as discrepant results is suggested by the High Verbal-Low Performance pro- three years old (19). work of Rourke, Young, and Flew- file (also 15 points or more); and In contrast to the association beelling (17) who found that learning- those with no disparity (5 points or tween speaking and generalized gesdisabled children with different pat- less) between these subscales of the turelike activity, speaking has been terns on the Wechsler Intelligence WISC. Performance of these three reported to depress performance of Scale for Children (WISC) per- groups was compared to that of a the right hand on specified manual formed differently on a variety of control group of normal readers. tasks. Kreuter and others (20) extests. Learning-disabled children In addition to investigating hemi- amined the effect of finger tapping with Low Verbal-High Performance spheric specialization using dichotic while performing concurrent verbal WISC IQ profiles were inferior to listening with different types of tasks by brain-bisected patients. learning-disabled children with High learning-disabled children, the ques- They found that moderately difficult Verbal-Low Performance IQ profiles tion of whether performing a second- verbal tasks disrupted only right inon most measures of verbal abilities ary task would have an effect on the dex finger tapping. Since the patient The AmericanJournal of Occufiational Therapy

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exhibited more competition between concurrent activities (speaking and tapping) when both were monitored by the same hemisphere, and relatively little between activities monitored on the opposite side of the brain, Kreuter suggested that concurrent activities compete when both are in the same hemisphere. Kinsbourne and Cook (21) also examined this relationship between motor and language performance, and they found a similar decrement in right hand performance with normal subjects when they were required to balance a dowel rod while repeating sentences. It was +covered that balancing time decreased for the right hand but increased for the left hand when sentence repetition was added to the balancing task. Kinsbourne and Cook concluded that concurrent activities of sufficient difficulty compete in proportion to the extent to which their cerebrally located neural programs share the same functional space, such as one hemisphere, a result and interpretation also reported by Johnson and Kozma (22). While Kinsbourne and Cook and others have attempted to overload the left hemisphere with verbalization and measured the effect of this manipulation on the ability to perform on a manual task, Botkin, Schmaltz, and Lamb (23) attempted to determine whether motor overloading would interfere with a subject's ability to perform digit repetition, a left hemisphere task. These researchers found that subjects who performed a motor task with their left arm were able to repeat more digits backward than were those who performed the task with the right arm, thus further supporting the finding of overloading the left hemisphere when two concurrent tasks have to be performed. Since, in the

Table 2 Mean Number of Taps Per 10-Second Trial tor Rlght and Left Hands for Learning-Disabled and Normal Subjects

Lv-HF

Grou

HV-LP V=P CONTROL

Right Hand 28.22

Left Hand 25.50

28.37 28.66 29.81

25.13 25.06 26.59

abled and normal subjects are presented in Table 1. The mean age for the LV-HP, HV-LP, V = P, and normal subjects were 134 months, 132 months, 136 months, and 128 months, with no significant difference among groups. Procedure. Each subject was individually tested on each of four tasks: Method rapid tapping, dichotic listening, diSubjects. The subjects were 61 chotic listening combined with left right-handed males who ranged in hand tapping, and dichotic listening age from 8 years, 3 months, to 13 combined with right hand tapping. years, 7 months. Forty-seven children The latter two tasks were given in a had diagnosed learning disabilities. counterbalanced fashion across subOf these, 16 children had Low Ver- jects with the other two tasks always bal-High Performance (LV-HP) given in the order stated. WISC scores as defined by a differRapid Tapping. On this task the ence between these two scales of at subject was asked to tap alternately least 15 points; 15 children had High on two 8.25 cm (3-1/4 inch) square Verbal-Low Performance (HV-LP) metal plates with a metal stylus. The WISC scores (also at least a 15-point plates were mounted 28.58 cm (11differential); and 16 children showed 1/4 inches) apart on a rectangular no discrepancy between their Verbal wooden base. Contact of the stylus and Performance Scales (V = P) of with the plate closed an electric cirthe WISC (a 5-point or less differ- cuit and activated a metal counter ential). There were 14 normal chil- that added the number of tapping dren from a public school. All chil- movements. Tapping movements of dren were from middle and upper the left and right hands were measmiddle income families. ured independently. The normal children all had IQs The subjects were allowed a 10equal to or above 90, were normal second practice period with each academic achievers, and had reading hand, followed by two experimental scores at or above grade level. All the trials of 10 seconds for each hand, children with learning disabilities administered in an alternating manhad either a Verbal or Performance ner. The final score for each hand I Q equal to or above 90 on the represented the average for the two WISC, and had a reading score at trials. Half the subjects performed least two years below grade level. the test first with the right hand and The mean IQs for the learning-dis- then with the left ; the remaining sub-

academic setting, children are often required to listen to the teacher (process language) and take notes (a skilled motor task) at the same time, it made sense to inuestigate the effect of a concurrent motor task on dichotic listening, particularly in children with learning disabilities.

496 September 1978, Volume 32, N o . 8

jects performed the test in the reverse sequence. Dichotic Ltjtening. The stimuli for this task consisted of pairs sing1e digits that were placed simultaneously to the left and right ears (one digit to each ear) through a set of stereophonic headphones. A trial consisted of three such pairs of digits presented at the rate of one pair per second. The subject was told the nature of the stimulus presentation, and instructed to report as many of the numbers as could be remembered immediately following their presentation. Two practice trials with two pairs of numbers per trial were given. Subjects concerned about the order in which to report the material were told to use the order that was most natural and comfortable for them. Each subject was then given 20 trials during which they received the series of 10 triplets twice; once with the headphones worn in one position; and then with the headphones reversed to control for any systematic error that might be introduced by stimuli or equipment that would favor one ear over the other. Tapping Concu~~ently with Dichotic Ltktening. The effect of tapping with either the right or the left hand upon dichotic listening performance was next tested. The subject was asked to tap in an alternating manner, as described, prior to and during the presentation of each dichotic trial. The subject started tapping at the tone of a buzzer, which was presented 3 seconds before the dichotic presentation, and continued to tap during the entire presentation of digits until recall was requested. As in the basic dichotic procedure, two series of 10 three-digit pairs were presented while the subject tapped with his right hand; and two series of 10 three-digit pairs were presented while the subject tapped with his left hand. Half the subjects

Table 3 Mean Number of Dlgits Correctly Reportedfor Each Ear by Each Group for Each Condltlon Dlchotic with Dlchotic with Basic Dichotlc Right HandTapplng Left Hand Tapplng Rlght Ear Left Ear Right Ear Left Ear Right Ear Left Ear LV-HP HV-LP v=p CONTROL

< ,.

21.8 23.2 22.7' 26.4t

20.6 21.1 18.8 24.1

22.2 22.3 21.4 26.3

18.8 22.8 19.3 24.8

23.9' 23.6 23.9' 27.1'

18.3 20.3 17.3 24.1

-n5

tn < -10

F(2,114) = 2.62, P < .lo, no other main effects or interactions were significant. The difference between groups in the ability to retain digits was largely a function of the fact that the control group consistently recalled more toResults The results of the tapping task tal digits than either the low verbal alone are shown in Table 2, which or the verbal-equals-performance shows the mean number of taps per groups. This was true on the basic 10-second trial for the right and left dichotic task (P at least < .05). after hands of the learning-disabled and right-hand tapping (P < .001), and normal subjects. Subjects from all after left-hand tapping (P < .001). groups made significantly more taps The low performance group also perwith their right than with their left formed below the control group, but hand (P at least < .05). There were not significantly so. When the number of correct reno differences between groups in speed of right hand (F less than 1) or sponses was scored as a function of ear input (Table 3), the superiority left hand (F less than 1) tapping. Table 3 shows the mean number of the control groups was more eviof digits reported correctly from each dent in left than in right ear recall. ear by subjects in each of the four This difference was significant (9 < groups on first, the basic dichotic .05) when the control group was contask; second, the dichotic task cou- trasted with the V = P group under pled with tapping by the right hand; all three conditions, and when the and third, the dichotic task coupled controls were contrasted with the low with left-hand tapping. A 4 ~ 3 x 2 verbal group under both tapping analysis of variance performed on conditions. The only specific inthis data revealed a significant over- stance of superior "right" ear recall all difference between groups, for the control group exists when F(3,57) = 7.36, P < .001, and be- they are contrasted with the low verbal group on the basic dichotic task. tween ears, F(1,57) = 31.99, p < Correlated t-tests revealed that on.001. Although the condition by ear interaction approached significance, ly the V = P Group had recalled sig-

performed the test first with their right hand and then with the left, while the remaining subjects carried out the task in reverse sequence.

The American Journal of Occupational Therapy 497

nificantly more digits presented to their right than to their left ($ < .05) ear on the basic dichotic task. The control group demonstrated performance in the same direction as the V = P group, but the left-right difference was only marginally significant ($ < .lo). When performance on the dichotic task with concurrent right -hand tapping was assessed, none of the groups showed significant ear differences in recall. However, when performance was measured during left hand tapping, all groups except the HV-LP group demonstrated a significant right ear effect ($ < .05). In other words, the V = P groups, the LV-HP group, and the control groLp all reported more digits presented to right ear than they did those presented to the left. Contrasting dichotic performance when concurrent tapping tasks occurred with performance on the basic dichotic task revealed that the only group to show any significant change was the LV-HP group. When concurrent left-hand tapping occurred, the right ear recall of the group improved significantly ($ < .05) relative to their basic dichotic performance, while their left ear recall deteriorated significantly ($ < .05) .This made this group's betweenear differential significantly greater following left-hand tapping than it had been on the basic dichotic task (p < .05). These same differences did not exist following right-hand tapping for this group nor for any other group. In fact, no other between-condition differences in recall existed for any of the other groups.

Discussion The outcome of the performance of each group on the basic dichotic task suggests a possible means of interpreting the previously conflicting results concerning hemispheric spe-

cialization in learning-disabled children. Whereas some studies (1l) found a slight trend favoring the left ear in learning-disabled children, others (15) found either weak right ear effects in learning-disabled children or no difference in right ear superiority between learning-disabled and normal children (16). The present investigation shows that children who exhibit disparities in verbal-performance scores on the WISC (interestingly enough, in either direction) fail to show a significant right ear advantage, but children with no scatter between their verbal performance WISC scores do show a right ear effect. Thus, in the basic dichotic task, it appears that the "type" of learning-disabled child involved in the study may determine whether or not a lateralization will be demonstrated. A second major finding on the basic dichotic task, which also carried through the dichotic and tapping tasks, was that all three learning-disabled groups recalled significantly fewer overall digits than did the controls. This outcome, which has also been observed by Ayres (24), might conceivably reflect these children's difficulty in handling competing stimuli. The control group's superior recall was more evident in the retention of digits presented to their left ear than was the case for those presented to the right. In fact, the between-group right ear differential may be even more dramatic than that indicated by the present study because the controls' retention of digits presented to the right ear approached a ceiling level. This "ceiling effect" might also be responsible for the minimal asymmetry seen in the control group during the basic dichotic task. When dichotic task was performed concurrently with right hand tapping, all three learning-disabled groups failed to show hemispheric

498 September 1978, Volume 32, No.8

specialization as did the control group. Thus, use of the right hand appeared to interfere with language processing. However, when left hand tapping was performed, the control, even scatter (V = P) groups and low verbal (LV-HP) groups, showed a right ear advantage. Thus, it appeared that left-hand tapping facilitates lateralization for all except the high verbal learning-disabled children. The low verbal (LV-HP) group seemed to be most affected by the tapping task; although they did not demonstrate right ear specialization on the basic dichotic task, they did when the task was accompanied by left handed tapping. This lateralization was produced by an increase in reporting right ear digits and a decrease in reporting left ear digits. It was as if the left hemisphere was facilitated while the right was being inhibited. Perhaps, for this group under normal conditions, the left and right hemispheres compete with one another for language processing with a resultant interference of performance. The high verbal (HV-LP) learning-disabled children did not show a lateralization effect under any conditions. It is possible that, for this group, both hemispheres process linguistic information, but neither has this as its "primary" responsibility. The even scatter (V = P) group was the only group, including the controls, to show a right ear effect on the basic dichotic task. With right hand tapping, this lateralization no longer existed, but with left hand tapping, it returned. Thus, these children evidenced a pattern similar to the normal controls in lateralization.

Conclusion In conclusion, it can be stated that the different types of learninp disabled-chilaen examined in this study seem to be differentially later-

lation to cerebral dominance and alized. In addition, they appear t o b e Kiley Brothers School, Peabody temporal analysis. Neuropsycholosomewhat differently affected b y the School, for their.support o f this p r o gia 8:351-361,1970 facilitory-inhibitory effects o f con- ject a n d f o r allowing us to test in 12. Zangwill OL: Dyslexia in relation to cerebral dominance. In Reading Discurrent activities. T h e low verbal their school, a n d also to Susan T a r ability: Progress and Research ( L V - H P ) children did n o t appear to low who helped t o tabulate the data. Needs in Dyslexia, J Money, Editor. be normally lateralized f o r language Foremost, thanks are extended to a l l Baltimore: Johns Hopkins, 103-113, 1962 processing, although the concurrent the children f r o m the L a n d m a r k 13. Taylor LB: Perception of digits preuse o f the right hemisphere f o r a School f o r Children with Learning sented to right and left ears in chilm a n u a l task did facilitate this spe- Disabilities a n d f r o m the Kiley dren with reading difficulties. Paper read at the ~ a n a d i a nPsychological cialization. T h e left hemisphere o f Brothers Elementary School who Association Meeting. Hamilton, Onhigh verbal ( H V - L P ) children also participated in this study. T h i s retario, Canada, 1962 did n o t appear t o b e specialized f o r search was supported in p a r t b y a n 14. Kawar M: The effects of sensorimotor training on dichotic listening in processing verbal material n o r was N I C H D Grant HD-09508 to Boston children with learning disabilities. specialization facilitated under any University School o f Medicine a n d is Am J Occup Ther 27:226-231, 1973 conditions. T h e even scatter ( V = P) based o n a paper presented at the 15. 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