hand preferences in sign-learning students with autistic disorder

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Hand preferences insign-learning studentswith autistic disorderJohn D. Bonvillian a , ElizabethThompson Gershoff b , Brenda C. Seal c

& Herbert C. Richards aa University of Virginia, USAb Columbia University, USAc James Madison University, USAPublished online: 15 Oct 2010.

To cite this article: John D. Bonvillian , Elizabeth Thompson Gershoff ,Brenda C. Seal & Herbert C. Richards (2001) Hand preferences in sign-learning students with autistic disorder, Laterality: Asymmetries of Body,Brain and Cognition, 6:3, 261-281, DOI: 10.1080/713754414

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Hand preferences in sign-learning studentswith autistic disorder

John D. BonvillianUniversity of Virginia, USA

Elizabeth Thompson GershoffColumbia University, USA

Brenda C. SealJames Madison University, USA

Herbert C. RichardsUniversity of Virginia, USA

The purpose of the study was fourfold: (a) to document the hand preferences ofnonspeaking individuals with autism as they produced signs and nonsign actions;(b) to find out if sign-language proficiency in such individuals is associated withdirectionality or consistency of signing hand preference; (c) to explore the linkbetween hand preference for signing and standardised measures of cognitive andmotor development; (d) to compare the hand preferences (sign and nonsignactions) of such individuals to sign-learning children with normal cognitivefunctioning. In this study, the hand preferences of 14 nonspeaking students withautistic disorder were determined from videotape records of their sign productionand nonsign actions. In their sign production, four students strongly favoured theirright hands, four had a distinct left-hand preference, and six did not significantlyfavour either hand. There was little evidence linking sign-language proficiency,cognitive maturity, or motor development to strongly lateralised signing or

LATERALITY, 2001, 6 (3), 261–281

Address correspondenc e to John D. Bonvillian, Department of Psychology, 102 Gilmer Hall, P.O.Box 400400, University of Virginia, Charlottesville, VA 22904-4400 , USA.E-mail: [email protected]

This research was supported in part by Social and Behavioral Sciences Research Grants 12-FY90-248 and 12FY92-0571 from the March of Dimes Birth Defects Foundation awarded to the firstauthor. Portions of this research were presented at the biennial meeting of the International Societyfor the Study of Behavioural Development in Berne, Switzerland, July 1998. The authors expresstheir gratitude to the administration, staff, and students of the Grafton School in Winchester, Virginiafor their assistance and participation in the study. The authors also wish to thank Theodore SiedleckiJr. and Stacy E. Curtis for their assistance in collecting and analysing the videotape records.

# 2001 Psychology Press Ltdhttp://www.tandf.co.uk/journals/pp/1357650X.html DOI:10.1080/13576500042000197

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handedness in general in these students. Compared with the hand preferences ofthe children in the two comparison groups, the autistic students were markedly lesslateralised with respect to signing, but not nonsign actions.

Children diagnosed with autistic disorder frequently fail to acquire usefulspoken language (Konstantareas, 1985; Rutter, 1966; Schuler & Prizant, 1987).In fact, communication deficits are so common in this population that they areamong the primary identifying features of childhood autism (AmericanPsychiatric Association, 1994; Lord, Rutter, & LeCouteur, 1994; World HealthOrganization, 1993). Because so many children with this disorder face profounddifficulties in acquiring spoken language, some have been taught alternativemethods of communication. Through sign-language training, many who hadfailed to develop even limited speech skills learned to communicate for the firsttime (Bonvillian, Nelson, & Rhyne, 1981; Layton, 1987). Unlike the temporarygains made by those who acquired some spoken language, most who learnedmanual signs maintained their communication skills over time (Gaines, Leaper,Monahan, & Weickgenant, 1988).

Although many nonspeaking autistic children have learned to communicateeffectively using signs, there have been wide individual differences in outcome.Bonvillian and Blackburn (1991) found that some children with autism acquiredhundreds of signs in a relatively short time, whereas others made only modestgains after years of training. In other research, Seal and Bonvillian (1997) foundthat such sign-learning children vary dramatically in their accuracy of signformation as well. In general, those who scored higher on tests of receptivelanguage, cognitive ability, social competence, and fine motor skills learned tosign more readily than peers who scored lower (Bonvillian & Blackburn, 1991;Seal & Bonvillian, 1997).

Whatever their communication skills, children with autistic disorder oftenperform poorly on tasks requiring the imitation of simple arm and handmovements (DeMyer, 1976; DeMyer et al., 1972) and motor sequencing (Wing,1988). In fact, such children find most imitation tasks difficult (Smith & Bryson,1994, 1998). Findings such as these suggest that individuals with autism sufferfrom apraxia (DeMyer, Hingtgen, & Jackson, 1981; Rapin, 1996), a neuromotordisorder that precludes or severely constrains voluntary, preplanned, andpurposeful motor movements (Wertz, LaPointe, & Rosenbek, 1984). Suchdeficits in praxis may undermine the acquisition of both speech (Page &Boucher, 1998) and signs (Seal & Bonvillian, 1997), and suggest that all theseproblems may have a neurological origin. Although no one has yet discovered asingle underlying cause or brain abnormality characteristic of autism (Bristol-Power & Spinella, 1999; Filipek et al., 1999; Filipek, Kennedy, & Caviness,1992), data such as these suggest that the neurological make-up of childrendiagnosed with the disorder is unlike that found in the general population

262 BONVILLIAN ET AL.

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(Alexander, Cowdry, Hall, & Snow, 1996). Today, nearly all investigatorsbelieve that the most intractable problems of children with autistic disorder arisefrom brain or neurological dysfunction.

The notion that some manifestations of autistic disorder stem fromneurological dysfunction is indirectly supported by studies of hand preference.Clinicians have long viewed atypical hand preference as a sign of possible braindamage (Goldstein, 1948), and researchers have found that non-right-handed-ness is common in neuropathological populations (Hicks & Barton, 1975). Non-right-handedness has been found to be especially prevalent among children whofunction at lower intellectual levels (Soper et al., 1986) and in mentally retardedadults with language problems (Lucas, Rosenstein, & Bigler, 1989).

Bishop (1990) identified similar anomalies in hand preference for childrenwith autistic disorder. In the several studies she reviewed, she found that adramatically disproportionate number of autistic children, compared with age-matched peers, favoured their left hand or showed a mixed hand preference.Others have reported similar findings (Barry & James, 1978; Boucher, 1977;Colby & Parkison, 1977; Cornish & McManus, 1996; Gillberg, 1983; Soper etal., 1986; Tsai, 1982, 1983; Tsai & Stewart, 1982). Perhaps even more tellingthan the high incidence of non-right-handedness is the discovery that manyautistic youngsters display ambiguous handedness (Soper et al., 1986). Byambiguous, these authors mean that the individual does not consistently chooseone hand or the other to accomplish a given task. For example, a child mightthrow a ball with the left hand on one occasion and with the right on another.

For most people, a distinct right-hand preference is associated with leftcerebral hemispheric dominance for language. The link between right-handedness and language production has been clearly documented in studiesof early signing. For example, in investigations of deaf and hearing childrenlearning to sign, a large majority developed a strong right-hand preference forsign production. Moreover, right-handedness appeared earlier and proved to bemuch stronger for sign production than for nonsign actions that werecontemporaneously observed (Bonvillian, Richards, & Dooley, 1997; Seal &Bonvillian, 1996). These findings, together with those of earlier case studyaccounts (Bellugi et al., 1986; Marentette, Girouard, & Petitto, 1990; Vaid,Bellugi, & Poizner, 1989), provide strong evidence that sign-languageproduction in most instances emanates primarily from the left side of the brain.Thus, it is possible that language production, spoken or manual, is so often left-lateralised that most individuals who learn to sign—autistic or not—will developa strong right-hand preference for signing.

In contrast, the absence of any distinct hand preference in so many childrenwith autistic disorder in previous studies suggests an atypical pattern ofhemispheric dominance. Moreover, at least some autistic children may havesuffered left-hemisphere or bilateral brain impairment that precludes the normaldevelopment of language skills and manual dominance (Chiron et al., 1995;

HAND PREFERENCES AND SIGNING IN AUTISM 263

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Dawson, Finley, Phillips, & Galpert, 1986). Thus, it is possible that braindevelopment for many (perhaps most) autistic individuals who learn to sign is soatypical that they fail to develop any strong hand preference—even for signing.

Whether or not hand preference anomalies persist as those individuals withautism learn to communicate in modalities other than speech is, at present,unknown. No one has yet studied the signing hand preferences of suchindividuals as they converse manually. The present study was designed to learnmore about such preferences. More specifically, the purpose of our investigationwas fourfold:

First, we wanted to find out if autistic individuals, who had never learned aspoken language, would display a distinct hand preference in their signproduction, and, if they did, which hand was preferred. We were also interestedin whether hand preference for signing differs from hand preference for nonsignactions. We offered no directional hypotheses about the signing handpreferences of this population because plausible, literature-based argumentscan be made to support a variety of outcomes.

Second, we wanted to learn more about individual differences in thelateralisation of hand preference in autistic individuals who have been taught tosign. On the basis of literature cited earlier, it is plausible to expect greater sign-language proficiency to be associated with either a distinct right-hand preferencefor signing or, at the very least, a strong hand preference in one direction or theother. Accordingly, we tested two related hypotheses: (a) Autistic individualswho acquire a larger sign lexicon will sign more consistently with the righthand; or, alternatively, (b) Such individuals will sign more consistently with apreferred hand—either the right or the left.

Third, we wanted to explore the relationship between hand preference forsigning and standardised measures of cognitive and motor development. Again,based on the literature, there is reason to expect some positive associationbetween hand preference and these indices of early development.

Finally, we wanted to determine if the hand preferences of autistic individualswho are learning to sign differ from those of young children with normalcognitive functioning who are learning to sign.

METHOD

Participants

There were three groups of participants—one served as the major focus of thestudy, the other two were used for follow-up comparisons. Members of all threegroups were in the process of learning to sign. Other than learning to sign, theparticipants in the three groups were not matched on any other ability orcharacteristic. The principal sample (the ‘‘autistic’’ group) consisted of 14students (12 boys and 2 girls) at the Grafton School. Grafton is a privateresidential facility for children and adolescents with developmental disorders


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located in Winchester, Virginia. The autistic students ranged in age from 9 years2 months to 20 years 4 months (the mean was 13 years 8 months). All had beendiagnosed with autistic disorder according to DSM-III or DSM-III-R guidelines.To be included in the study, there had to be a documented absence of spokenlanguage, on-going involvement in a sign-language training programme for atleast six months, and written permission to participate. These same youngpeople served as participants in a study of sign-formation accuracy reportedelsewhere (Seal & Bonvillian, 1997).

The first comparison sample (the ‘‘deaf parent’’ group) consisted of 24infants and young children (9 boys and 15 girls) who came from homes whereone or both parents were deaf. At the time of initial observation, they ranged inage from 6 to 46 months. Three were deaf, and 21 had normal hearing. All useda sign language, typically American Sign Language (ASL), as the principalmeans of communication at home. The 21 participants with normal hearing alsoreceived spoken English input from other adults, older children, and television.Additional details about these children and their families can be found inBonvillian et al. (1997).

The second comparison sample (the ‘‘deaf children of hearing parents’’group) consisted of 20 deaf children (12 boys and 8 girls) with hearing parents.When they were first observed, there were five children in each age categoryranging from 2 to 5 years (i.e. five 2-year-olds, five 3-year-olds, five 4-year-olds, and five 5-year-olds). All had been diagnosed with bilateral hearing lossprior to their third birthday. None of the parents had been introduced to a signlanguage until after the child’s hearing loss had been diagnosed. Additionalinformation about these children and their parents can be found in Seal andBonvillian (1996).

Measures, procedures, and coding

Autistic group. Much of the sign-language instruction that the autisticstudents received at the Grafton School was relatively structured and systematic.Typically, students were initially prompted, then reinforced for producing signs.As the students progressed, the number of prompts was gradually reduced. Thestudents were also exposed to simultaneous presentations of speech and sign inthe context of incidental language activities. Although ASL signs constituted themajority of the teachers’ sign productions, a number of the signs that weretaught to the students had been modified slightly to make them easier for thestudents to form. In addition to their sign-language programmes, seven of ourparticipants were given instruction with communication books that featuredpictures of objects and their corresponding signs.

Teachers were informed of the nature of our study several weeks prior to thefirst visit. Each was told that we planned to videotape the students as theyinteracted with their teachers through signs. During taping sessions, teachers


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were asked to elicit as many signs as possible from their students, but otherwiseto work with them as they would on a typical day. Because they knew theirstudents well, teachers were permitted to choose whatever method they thoughtbest for meeting the objectives of the study. Some teachers elicited signcommunication with material objects (e.g. puzzles, blocks, picture cards); othersused edible reinforcers (e.g. crackers, raisins).

Each participant was videotaped as he or she worked with his or her principallanguage teacher—either the classroom instructor or a speech-languagepathologist. In most cases, the videotaping of student–teacher interaction wascompleted in a single session. These taping sessions typically took place in anactivities room at the Grafton School, an environment that was familiar to theparticipants, well lit, and, for the most part, free from interruptions ordistractions. The remaining sessions took place in the students’ regularclassrooms. Most sessions were successful in that the individual student beingtaped engaged in sign conversations with his or her teacher throughout . In a fewother sessions, the individual student behaved aggressively or repeatedlyengaged in stereotypic movements. Whenever a teacher indicated that a studentwas not cooperating satisfactorily, the session was terminated. In such instances,videotaping was recommenced during a subsequent visit. The duration of theindividual videotape segments ranged from 9 to 32 minutes—the mean wasslightly over 18 minutes.

Two independent raters viewed the videotaped segments of the autisticparticipants conversing in sign language with their teachers and coded theobserved signs according to hand preference. For each student and teacher, theraters coded the signs made with the right hand, left hand, or both. A sign wasconsidered right-handed if it was made with the right hand alone or, for two-handed asymmetrical signs, if the right hand was the active or dominant handand the left served as the base. A sign was considered left–handed if it was madewith the left hand alone or, for two-handed asymmetrical signs, if the left handwas the active or dominant hand and the right served as the base. Two-handedsigns were classified as both if the handshape, location, and movement aspectswere the same (or symmetrical) for each hand. The data were massed andinterrater agreement calculations made. The raters agreed 93%of the time aboutwhich actions represented meaningful signs, and, for those signs identified byboth, the raters agreed 95% of the time about hand preference.

The raters also observed 5-minute videotape segments of the autisticparticipants producing nonsign gestures and actions and coded each observedactivity according to hand preference. Nonsign activities were categorised asfollows: (a) object actions (such as rolling objects or manipulating a toy); (b)self-touching (such non-injurious behaviours as thumb or finger sucking or hairtwisting); (c) communicative gestures (such as pointing to convey information);(d) noncommunicative gestures (such as pointing to orient the self or reaching);and (e) motor stereotypies (such self-stimulatory or repetitive behaviours as


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hand biting or finger flicking). To allow time for students to adjust to thecamera, raters did not code any events that occurred during the first minute of asession. As with signs, raters coded each nonsign gesture or action according tohand use as either right-handed, left-handed, or both. As with the signjudgements, intercoder agreement was high. (Because it was not always possibleto identify which particular nonsign action produced by an autistic participantwas being coded by a rater, we elected to calculate interrater reliabilitycoefficients for the two independent raters across the different nonsign actioncategories and the three hand-preference classifications. The mean correlationwas .94.)

In addition, a videotaped interview was conducted with all participatingteachers. Each was asked about the communicative behaviour and signproduction of his or her students. Also, the teachers demonstrated how theyformed each of the signs in their students’ vocabularies. Most teachers broughtwritten records of their students’ sign vocabularies to their interviews as an aidin making these demonstrations. Interview times varied widely. They rangedfrom a little over 2 minutes (with a teacher whose student had a small signlexicon) to almost an hour (with a teacher whose student signed extensively).The mean duration was 14.3 minutes.

Finally, each student’s permanent record was reviewed to learn more abouthis or her cognitive and motor functioning. Although the specific tests givenvaried from student to student, we were able to cull out three developmentalindices common to nearly everyone in the sample: a cognitive (or mental) age, agross motor age, and a fine motor age.1

Comparison groups. For the deaf parent group, videotaped records of thechildren using their hands, both to sign and to engage in nonsign actions, wereobtained during periodic home visits. In most cases, each child was visited every4–6 weeks for about an hour. The median number of home visits for theparticipating families was 7, with the range extending from a single visit to 13visits. During these sessions, the parents were asked to encourage their child tosign. To elicit nonsign actions, the researchers spread a blanket on the floor andplaced age-appropriate toys on it. Each participant was then invited to play withthe toys. In this manner, many parent-prompted sign productions and play-inspired nonsign actions were captured on videotape.

1 The autistic participants’ cognitive, gross motor, and fine motor test scores, and age equivalentswere obtained from the following tests: the Bayley Scale of Mental Development , the LearningAccomplishment Profile, the Leiter International Performance Scale, the Peabody Developmenta lMotor Scales, the Stanford-Binet Intelligence Test, the Vineland Adaptive Behavior Scales, and theWechsler Intelligence Scales for Children–Revised. Where multiple tests had been administered to aparticular individual over a period of years, the most current age equivalent score was selected.


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For the deaf children with hearing parents group, participants werevideotaped as they took part in various preschool or kindergarten programmesfor hearing-impaired children. The researchers made no attempt to alter orcontrol any of the ongoing activities of those they observed, and each child’ssign production and nonsign actions were recorded as he or she played withother children or interacted with the classroom teacher. All of the children weretaught by teachers who used simultaneous communication (i.e. the teachersspoke and signed at the same time). The teachers’ bimodal utterances typicallyinvolved putting ASL signs together with spoken English words in sentencesthat followed the word order of English. For most participants, recordings werespread over periods ranging from 4 to 12 months. The number of videotapedsessions varied from child to child. One child was taped only once, four otherstwice, and the remaining 15 three or four times. On average, taping sessionslasted 44 minutes.

For both comparison groups, two—and in the case of those with deaf parents,three—raters viewed the tapes and coded the children’s sign productionaccording to hand preference. As with the autistic participants of the primarysample, raters coded the signs made with the right hand, left hand, or both.Likewise, the first 3–5 minutes of each child’s videotaped record were coded fornonsign actions. With the exception of motor stereotypies, which were unique tothe autistic individuals, the nonsign action coding categories were the same asthose previously described. As before, interrater agreements about handpreferences were high for both signs (94% for the deaf parent group; 92% forthe deaf children of hearing parents group) and nonsign actions (95% for thedeaf parent group; 96% for the deaf children of hearing parents group).Disagreements were resolved by a third (and for the deaf parent group,sometimes a fourth) coder. Additional details about procedures and coding forthe comparison groups can be found in Bonvillian et al. (1997) and Seal andBonvillian (1996).

Data reduction

For each participant, we computed two Hand Preference Index (HPI) scores, onefor signs, the other for nonsign actions. We also computed sign HPI scores forthe teachers of the autistic students. An HPI score for signs was computed bysubtracting the number of left-handed signs from the number of right-handedsigns and dividing by the total number of signs (including symmetrical signsmade with both hands). Thus, a participant who signed only with the right handwould be given an HPI score of + 1.0; one who signed only with the left, 71.0.Nonsign HPI scores were computed in a similar manner on the basis of otherobserved actions and gestures. Because only the autistic participants exhibitedmotor stereotypies, nonsign HPI scores were computed twice for this group—


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once with stereotypies excluded from the calculation, and once with themincluded.

Finally, to determine which participants signed more often with one hand orthe other, the number of left-handed signs was subtracted from the number ofright-handed signs. According to Lederer and Redfield (1939), such differencescan be converted to z-scores by dividing them by the square root of the totalnumber of right- and left-handed signs (note that symmetrical signs made withboth hands have been excluded from this calculation). Participants who scoredhigher than 1.96 significantly (p < .05) preferred the right hand over the left;those who scored lower than 71.96 significantly preferred the left over theright. Similar computations were made for nonsign action hand preferences.

RESULTS

A preliminary analysis revealed that 12 of our 14 autistic participants displayeda variety of stereotypies. Many of these behaviours, such as finger flicking, wereself-stimulatory; others, such as hand biting and head hitting, were self-injurious. Unlike our comparison groups in which such activity was notobserved, stereotypical behaviours were common among the autistic students.While being videotaped, our participants produced 172 such movements—about12.3 per individual—and one individual produced 51. Although slightly morestereotypical behaviours were performed with the right hand than the left, theinclusion of these data in the computation of nonsign HPI scores made littledifference, statistically or practically. Means of the nonsign HPI scores with andwithout the inclusion of stereotypies were .07 and .04 respectively (a negligibledisparity), and the scores generated were highly correlated (r = .97). To maintaincontinuity with our two comparison groups, we excluded stereotypies from allsubsequent computations.

To address the first objective of the study, namely to find out if our autisticparticipants displayed distinct hand preferences, we studied the groupcollectively. The participants produced a total of 534 signs on videotape. Ofthese, 173 (32%) were classified as right-handed, 206 (39%) as left-handed, and155 (29%) with both hands performing symmetrical actions. (Of the totalnumber of signs produced by the autistic students, 15.2% were two-handedasymmetrical signs.) They also performed 599 nonsign actions—299 (50%) withthe right hand, 231 (38%) with the left, and 69 (12%) with both. Taken as agroup, our autistic students failed to exhibit a strong right- or left-hand bias forany actions. For signing, there was a slight preference for the left; for nonsignactions, a somewhat stronger preference for the right. Furthermore, the autisticstudents’ hand-preference scores were relatively consistent across the differentcategories of nonsign action that we scored. The students’ mean hand-preferencescores for the various nonsign action categories did not differ significantly from


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one another and each of the scores was positively correlated with overallnonsign action hand-preference scores.

Sign production, nonsign actions, HPI scores, and hand preferences for eachparticipant with autism are shown in Table 1. As can be seen by their z-scores,four participants signed significantly more often with the right hand, four moreoften with the left, and six displayed no significant hand preference. As forproduction of nonsign actions, four participants significantly preferred the righthand, one the left, and nine showed no significant hand preference. Looking atthe autistic group as a whole, we found no significant difference (t = 71.17,n.s.) between mean HPI scores for signing (M = 7.13) and nonsign actions(M = .04). Finally, although positive, the correlation between sign and nonsignHPI scores proved to be modest (r = .39, n.s.). Thus, signing was neither morelateralised in terms of hand preference than other types of manual activity, norwas sign hand preference a particularly good predictor of hand preference ingeneral.

In addition to the students’ hand preferences in their overall signing, we wereinterested in the question of whether or not individual autistic students wereconsistent in their hand preferences in their production of the same sign overtime. For example, would a student form the sign for drink with his or her righthand at one time on the videotape and then elect to make the sign with his or herleft hand later in the videotape? To answer this question, we first examined eachstudent’s videotape records, listing each sign made with either the left or righthand that was a repetition of a previously produced sign. This list was thenreduced in length by eliminating those signs that were repetitions of animmediately preceding sign; this way perseverative productions of the same signwere excluded. Altogether, there were 177 instances, not including immediaterepetitions, involving 11 of the students in which an individual student producedthe same sign on videotape more than once. For those students whodemonstrated a distinct signing hand preference, changes in the hands theyused to form particular signs were rare; they changed their signing hand, onaverage, in only 7.2% of their nonconsecutive sign repetitions. In contrast, forthose students without a distinct signing hand preference, there was considerablygreater variability in which hand they elected to use to form the same sign intheir lexicons on different occasions; they changed their signing hand, onaverage, in 34.2% of their nonconsecutive sign repetitions.

Before addressing the next two objectives of the investigation, it is importantto consider the influence of teachers as a possible confounding variable. To findout if the sign hand preferences of the teachers strongly influenced the actions oftheir students, case by case comparisons were made. The results are shown inTable 2. As can be seen in the table, the teachers signed far more often with theirright hands than did their students—mean HPI score difference was .76,t(13) = 4.14, p < .001. Moreover, the correlation between the teacher and studentsign HPI scores was not only nonsignificant, but directionally backwards


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(r = 7.27). Thus, we found no evidence that participants shared the sign handpreferences of their teachers.

To address the second objective, to determine if those students who develop alarger sign lexicon sign more consistently with the right hand or, alternatively, ifsuch individuals sign more consistently with either the right or left hand, we firstcorrelated sign and nonsign HPI scores with sign vocabulary size. Then, usingthe absolute values of the HPI scores as an index of a ‘‘preferred hand’’, wegenerated two additional correlations. (The use of absolute values wouldtransform the HPI scale into a scale extending from 0 to 1. Individuals whoshowed a strong hand preference, either distinctly left-handed or right-handed,would earn higher scores.) The results are shown in the first column of Table 3.As can be seen, the correlations are neither directionally consistent norsignificant. We found no evidence that sign-language proficiency is associatedwith either a strong right-hand or a left-hand signing preference, nor was thisskill linked with handedness in general.

To address the third objective of the study, to determine if hand preference isa positive predictor of cognitive and motor development, we correlated HPIscores and their absolute values with our indices of cognitive, gross motor, andfine motor age. The results are shown in the last three columns of Table 3. SignHPI scores, but not their absolute values, tended to be positively correlated

TABLE 2Teacher and student HPI scores, sign vocabulary size, and cognitive and motor ages by

case for autistic group

HPI score Motor age

Case Teacher Student

Signvocabulary

sizeCognitive

age Gross Fine

1 .39 7.67 95 44 41 342 .29 .05 31 24 NA 473 .40 7.19 21 24 36 394 .15 .25 39 48 72 365 1.00 71.00 6 26 36 246 1.00 7.84 3 8 36 117 .71 .34 19 28 36 308 1.00 7.67 7 33 NA 299 .67 7.42 20 24 72 48

10 .82 .82 9 48 36 4011 .78 .74 21 24 72 6012 .67 .00 3 23 36 2413 .50 7.42 9 48 52 6014 .47 .12 123 27 83 83Mean .63 7.13 29.00 30.64 50.67 40.36SD .27 .57 35.92 12.02 18.57 18.37

Cognitive and motor ages are in months. Gross motor ages were unavailable for Cases 2 and 8.


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(coefficients ranged from .25 to .42) with all three measures of development.None was statistically significant. The results are directionally consistent withour initial conjectures, but more research is needed to determine if handpreference for signing is more than a chance predictor of development.

Finally, to meet the fourth objective of the study, we compared the handpreferences of the autistic young people with those of the comparison groups.We computed sign and nonsign HPI means for the respective groups andconducted two one-way (three group) analyses of variance to test for significantdifferences. The results are shown in Table 4. As shown in the table, the groupsdiffered with respect to sign HPI scores, F(2, 55) = 13.72, p < .001, but notnonsign HPI scores, F(2, 55) = 1.45, n.s. An a priori test of simple effectsconfirmed what is visually apparent by inspecting the means—the autisticstudent group generated a significantly lower sign HPI score mean than that ofthe comparison groups, t(55) = 75.17, p < .001.

TABLE 3Correlations of sign and nonsign HPIs and absolute values with sign vocabulary size

and with cognitive, gross motor, and fine motor ages

Motor ageSignvocabulary

sizeCognitive

age Gross Fine

Sign HPI score .06 .25 .29 .42Nonsign HPI score 7.35 .05 7.05 7.09Sign HPI absolute value 7.26 .04 .28 7.34Nonsign HPI absolute value .12 .40 7.34 7.28

None of the tabled correlations are significant at the .05 level.

TABLE 4Means and standard deviations of sign and nonsign HPI scores of autistic and

comparison groups and associated F-ratios

Autisticstudents(n = 14)

Childrenwith deafparents(n = 24)

Deaf childrenwith hearing

parents(n = 20) F-ratio

Sign HPI scores 7.14(.57)

.47(.26)

.40(.28)

13.72**

Nonsign HPI scores .04(.39)

.18(.23)

.09(.15)

1.45

Standard deviations are in parentheses.** p < .001.


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Descriptively, the students with autism formed a slight majority of their one-handed signs and two-handed asymmetrical signs (54.4%) with their left handsas the sole or dominant hand. Both comparison groups did the opposite—that is,they formed these types of signs (82.9% and 77.4% for the children with deafparents and deaf children with hearing parents groups, respectively) in mostinstances with their right hands as the sole or dominant hand. To determine if theparticipants’ sign hand preferences differed from chance, single sample t-testswere conducted on the sign HPI means. The comparison groups clearly favouredthe right hand in their signing. Their means were +.26, t(23) = 9.01, p < .001, forthe children with deaf parents group and +.40, t(19) = 6.03, p < .001 for the deafchildren with hearing parents group. For the autistic student group, however, themean HPI for signing was 7.14 and did not differ significantly from zero,t(13) = 7.89, n.s. When signing hand preference was examined case by case, theproportion of right-handers was much lower among the autistic participants(28.6%) than either comparison group (76.2% and 85.0%, respectively).

Unlike signing, the autistic participants resembled the comparison groups inthat they slightly preferred the right hand for one-handed nonsign actions. Forsuch movements, the autistic group used the right hand 56.5% of the time, thedeaf parents group 59.9%of the time, and the deaf children with hearing parentsgroup 56.2% of the time. This observation of a slight preference for the righthand in one-handed nonsign actions across the three groups is in general accordwith previous research on the development of hand preference in youngchildren. Most investigators have found hand preference to be poorly defined inchildren under 2, but to have become relatively well established for most by age3 (McManus et al., 1988). In the present study, however, as shown by thenonsign action HPI means and associated statistical tests, only the handpreference scores of the children with deaf parents group proved to besignificantly above chance, M = +.18, t(23) = 3.82, p < .01. Neither the autisticstudents M = +.04, t(13) = .35, n.s., nor the deaf children with hearing parents,M = +.14, t(19) = 2.05, n.s., group yielded nonsign HPI means that differedsignificantly from zero.

DISCUSSION

An important finding of the present study is that the autistic students had a lowerincidence of right-handed signing than that of the young children in the twocomparison groups. In those two groups, the large majority of the childrenshowed a strong preference for their right hands in their sign production.Moreover, this preference for right-handed signing was greater than that fornonsign action production. In contrast, fewer than one-third of the students withautistic disorder clearly favoured their right hands in their sign production.Furthermore, for the autistic students, the sign HPI score mean was much lowerthan those of the children in the two comparison groups. Moreover, the sign HPI


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score mean of the students with autism did not differ significantly from theirnonsign HPI mean.

What might underlie such contrasting patterns of hand preference betweengroups? In our accounts of the hand preferences of the young deaf and hearingchildren in the two comparison groups, the children’s strong right-handpreference in signing probably reflected a fundamental hemispheric asymmetryfor language and sequential motor processing (Bonvillian et al., 1997; Seal &Bonvillian, 1996). Because signs are both linguistic events and sequential motoractions, a right-hand preference for signing provides evidence of left-cerebraldominance (or lateralisation) for language (Best, Hoffman, & Glanville, 1982;Entus, 1977; Molfese, Freeman, & Palermo, 1975) and for complex motormovements (Heilman, 1979) that emerge in early childhood. Although theautistic students typically made progress in learning to communicate for the firsttime through signs, their sign learning did not appear to progress as easily or inthe same way as that of the two comparison groups.

The autistic students often needed repeated sign presentations, handmoulding, and considerable prompting before a sign was learned. For those inthe comparison groups, sign acquisition was much less structured and seeminglyless effortful. Perhaps underlying the autistic students’ failure in learning tospeak, their seemingly more effortful sign learning, and the frequent absence ofa distinct right-hand preference for signing is some form of left hemisphere orbilateral brain damage. Another possibility is that cerebellar abnormalities,which are often found in individuals with autism (Kemper & Bauman, 1998),may have adversely affected the motor movements and sequencing involved inthe present participants’ sign acquisition and production. In addition, McManusand Cornish (1997) have advanced the view that abnormalities in the cerebellummay contribute to the ambiguous handedness frequently seen in persons withautistic disorder. This speculation is supported by the finding that the pattern ofcerebellar asymmetry associated with right-handedness often is absent in non-right-handed persons (Snyder et al., 1995).

In our analyses of the relationships between handedness and measures of signlanguage, cognitive, and motor development, we included both the autisticstudents’ sign and nonsign HPI scores and the absolute values of these scores.This latter approach enabled us to examine whether the presence of a distincthand preference—regardless of direction—was an important predictor ofdevelopment. The absence of any significant correlations in these analyses isconsistent with the view that autistic students’ development in the domainsexamined is largely independent of the establishment of a distinct handpreference, right or left.

Among the participants with autism, four showed a distinct left-handpreference in their signing whereas only one showed a distinct left-handpreference for nonsign action production. (That student favoured the left handin making both signs and nonsign actions.) One possible explanation for the


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students’ higher incidence of left-handed signing is the positioning of theteachers when they interacted with their students. When we reviewed ourvideotaped records, we were surprised to discover that when both the teachersand students were seated, the teachers typically sat to their students’ immediateleft. In this seating arrangement, the teachers’ right hands were in closeproximity to their students’ left hands. The teachers would then occasionallyreach over with their right hands and touch their students’ left hands to mouldor to prompt their sign production. There were also several instances on thevideotapes when a student appeared to mirror a teacher’s signing. Mirroringoccurred when a teacher and student were facing each other and the studentwould sign using the hand closest to the teacher’s active signing hand. Becauseteachers signed more with the right hand, the students facing them wouldimitate by signing with the left. Taken together, the autistic students’occasional mirroring of their teachers’ signing and the teachers’ apparentlymore frequent prompting of their students’ left hands for signing probably hadat least a small effect on the students’ development of a signing handpreference (or lack of one). This effect may not be universal, however. Someof the autistic students who showed a strong right-hand signing preference alsohad teachers who sat to their left. In any case, the signing hand preferences ofthe children in the comparison groups did not appear to be affected by suchpositioning.

Another possible reason for this greater left-handed preference for signing inthe autistic students is that their right hemispheres may have become moreactively involved in language processing than commonly occurs in the course ofnormal language development. Perhaps the right hemisphere becomes moreinvolved in language acquisition and use when a language is not introducedeither in infancy or early childhood (see Locke, 1997), as would be the case forthe present participants with autism.

In addition to determining whether students with autistic disorder wouldshow a distinct hand preference in their signing, we examined the data to see ifthese students would be consistent in their production of individual signs fromtheir lexicons. Those students who had a distinct left or right signing handpreference not only favoured a particular hand overall, but rarely changed thehand they used in forming individual signs. In contrast, those students who didnot demonstrate a distinct signing hand preference were much more likely toswitch from one occasion to the next. Thus, the less lateralised studentsdisplayed an ambiguous handedness pattern (Soper et al., 1986), both for theirsigning overall, and in their formation of individual signs in their lexicons.

The finding that most of the students with autistic disorder did not show adistinct right-hand preference in their production of nonsign actions is consistentwith the results of a number of previous studies (e.g. Boucher, 1977; Colby &Parkison, 1977; Gillberg, 1983). However, only 28.6%of the autistic students inthe present study showed a distinct right-hand preference in their nonsign action


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production, a somewhat lower percentage than in previous studies. In the handpreference studies reviewed by Bishop (1990), the percentage of autisticchildren identified as right-handed was 10 to 20% higher than that found in thepresent study. We can offer two plausible explanations for the relatively lowincidence of right-handedness among our participants:

First, our participants constituted an atypical sample of individuals withautism, in that we selected only individuals who lacked spoken language.Because the presence of spoken language in autistic individuals is associatedwith higher levels of cognitive functioning (Bryson, Clark, & Smith, 1988; Winget al., 1976), our sample of nonspeaking participants probably contains a higherproportion of individuals who are cognitively low-functioning and have seriouslanguage disturbances than did previous studies of autism and handedness. Suchan interpretation would be consistent with the finding that a low incidence ofright-handedess is common among cognitively low-functioning individuals withserious language disturbances (Bradshaw-McAnulty, Hicks, & Kinsbourne,1984; Douglas, Ross, & Cooper, 1967; Hicks & Barton, 1975; Lucas et al.,1989). Thus, the present rather anomalous handedness findings may well beattributable to the unusual composition of our sample.

Second, largely because of the nature of our sample and the focus of ourstudy, we depended on naturalistic observation, not tests, to assess handedness.Most handedness tests include tasks that require the exclusive use of one hand orthe other, and tend to yield more definitive handedness scores. Had we used suchtests in our study, it is possible that more right-handed participants would havebeen identified. Of course, it is often quite difficult to get low-functioningindividuals with autism, much less the very young children in the comparisongroups, to actively engage in such testing.

Although the autistic students as a group made a much lower proportion oftheir signs with their right hands than did the children in both comparisongroups, it should be recalled that the three groups did not differ significantly intheir nonsign action hand preferences. In reflecting on this latter result, it shouldbe noted that although the students with autism were chronologically mucholder, the three groups did not appear to differ markedly in their cognitive andmotor ability levels. The autistic students’ median cognitive age was 28 monthsand their median gross and fine motor ages were both 38 months. Becausestandardised tests of cognitive and motor abilities were not administered to theyoung children in the deaf and hearing parents groups, this precluded systematiccomparisons of ability scores across groups. But with most of the deaf andhearing children in the comparison groups between the ages of 1 and 5 yearschronologically, we would have anticipated that their cognitive and motorability age levels would have been similar to those of the students with autism.This observation about similarities in developmental levels might help explainwhy there was some resemblance across the three groups in their nonsign actionhand preferences.


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The present study represents an initial effort to describe the hand preferencesof individuals with autistic disorder who have learned to communicate throughsigns. In the future, we would like to expand on this work by exploring severalrelated topics. Because the participants in this study were much older than thesign-learning children in the comparison groups, we would like to explore handpreference in sign and nonsign actions in younger children diagnosed withautistic disorder. One reason for this interest is that earlier onset of interventionhas been associated with improved outcomes, including language (Rogers,1996). Perhaps children with autism who were introduced to signs earlier in lifemight demonstrate more distinct signing-hand preferences. A second topic thatmerits examination is whether the nonsign hand preferences of autisticindividuals who communicate primarily by signs differ from those individualswith autism who acquire useful speech. If these groups are found to differ, thenthis might indicate that they differ on dimensions other than the modality of thelanguage they use. A third topic that merits additional exploration is thedevelopmental course of autistic individuals’ signing-hand preferences. In ourtwo studies of young deaf and hearing children learning to sign, most of thechildren who became right-handed signers showed a distinct right-handpreference for signing beginning with their initial sign productions. Alongitudinal investigation of the hand preferences of autistic individuals asthey are being taught to sign might help indicate whether any hand preferencesthat are observed are more the product of learning or are more the reflection ofdifferences in the brain tied to sign-language processing.

Manuscript received 26 April 2000Revised manuscript received 25 August 2000

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ecem

ber

2014

hand preferences in sign-learning students with autistic disorder

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