Journal of Autism and Childhood Schizophrenia, Vol. 7, No, 1, 1977

Handedness in Autistic Children

Kenneth Mark Colby and Carole Parkison Department of Psychiatry, University of California, Los Angeles, School of Medicine

A test o f handedness in a sample o f 20 autistic children and 25 normal children revealed marked differences. The frequency o f non-right-handed- ness in normal children was 12o70, whereas it was 65070 in autistic children. The significance o f this difference for the etiology o f autism is discussed.

INTRODUCTION

Some informal observations of autistic and normal children playing with a computer-controlled audiovisual display (Colby & Kraemer, 1975) led to the notion that the distribution of their handedness might be different in the two groups. Our initial impression was that the frequency of definite right- handedness was lower in autistic children while the frequency of left- handedness and ambilaterality was higher compared to normal children. If true, this hypothesis would have implications for the etiology of autism, as will be discussed.

The exact distribution of handedness in a population is difficult to de- termine. Much depends on the definition of handedness, the sample, and the method of measurement used to determine hand preference. Bystander observation, self-report, and questionnaires are all known to be somewhat unreliable (Hardyck & Petrinovich, 1976). Currently, it seems agreed that the frequency of dextrality is about 90~ and sinistrality about 10~ Among the 90~ dextrals, 99.7~ have left-hemisphere dominance. Among the 10~ sinistrals, about 65070 have left-hemisphere dominance while about 35070 have right-hemisphere dominance (Levy, 1974). During the first 4 years of childhood, normal children show some degree of ambilaterality and oscillate in their hand preference (Gesell & Ames, 1947). The adult preference becomes established at about 4 years.

There are several studies in the literature reporting increased sin- istrality in epilepsy (17.5~ compared with 8~ in controls), in mental retar-

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4 Colby and Parkison

dation (23%), and in both monozygotic and dizygotic twins (10.9% com- pared with 6.6~ in nontwins). These findings are cited and discussed by Levy (1974). For each of these conditions it has been proposed that damage to the left hemisphere produces a switch in natural (genotypic) handedness. Since roughly 90070 of people are genotypically dextrals and 10% are genotypically sinistrals with 65070 of the sinistrals having left-hemisphere dominance, a random distribution of lesions between the two hemispheres would lead to an increase in phenotypic (pathological) sinistrals (Satz, 1973).

We have been unable to find in the literature a systematic study of handedness in autistic children. In a recent report, Hauser, DeLong, and Rosman (1975) stated that 8 out of their 17 autistic children were left- handed while 3 had failed to establish dominance.

To check out the hypothesis that the distribution of handedness dif- fered in autistic children, we first made a pilot survey of 120 UCLA hospital records of autistic children from 1963 to 1976. The criteria used at UCLA for the diagnosis of autism are thoroughly discussed in Ornitz and Ritvo (1976). They include disturbances of perception, of developmental rate, of relating to others, and of speech and language.

In this sample of 120 children we found 40 whose handedness was mentioned. As can be seen from Table I, 52.5070 of the autistic children were non-right-handers as compared to the 1007o assumed for the normal popu- lation.

It is easy to question the reliability of clinical records reporting casual observations rather than results of specific performance tests. Hospital charts usually do not indicate the particular observations on the basis of which the judgment of hand preference is made. Also, there might be a

Table I. Handedness Information on Autistic Children a

Boys Girls Total

Right-handers 15 4 19 Left-handers 10 3 13 Ambilaterals 6 2 8

Total 31 9 40 %RH 48.4% 44.4% 47,5% %LH 32.3% 33.3% 32.5% %Ambi 19.3% 22.3% 20.0%

Total non-right- handers = 52.5%

aTaken from charts at the Neuropsychiatric Institute, UCLA.

Handedness in Autistic Children 5

greater tendency to report a child as being left-handed in contrast to right- handed, thus biasing the sample. It is because of these possible unreliabili- ties that we decided to test the handedness of a group of autistic children and compare them with a group of normal children.

METHOD

Subjects

From September 1975 to July 1976 we tested 20 autistic children, 16 males and 4 females, hospitalized on the wards of the UCLA Neuropsy- chiatric Institute. All were diagnosed as autistic according to the UCLA criteria (Ornitz & Ritvo, 1976). Similar testing was carried out in July 1976 on 25 normal children, 16 males and 9 females, from the UCLA Child Care Center. All the children tested ranged from 2.2 to 6.9 years of age, with a mean age of 4.3 years and a standard deviation of 1.6 years. All of the children participated without complication and the testing required about 20 minutes per child.

Procedure

We constructed a battery of simple tests based on traditional indica- tors of handedness. We selected tasks which autistic and normal children between the ages of 2 and 6 years might perform. Our tests were writing, drawing, stacking blocks (at least five), eating with a spoon or fork, ham- mering, winding thread on a spool (moving hand), spinning a top, throw- ing, turning pages, putting marbles into a small-necked bottle, pulling the top off a plastic bottle, unscrewing a lid, cutting with scissors, reaching, and other informal tests which the children invented while playing with the test items, such as peeling the price tag off a ball, turning a doorknob, knocking on a door, scribbling, and similar tasks.

Because the dexterity necessary to successfully execute an activity varied from item to item, we weighted activities according to the amount of dexterity required (in our judgment). Tasks using strength were considered less important than ones requiring more refined coordination. Tasks re- quiring language and coordination were considered the most important. Consequently, we constructed the following weight classifications: (1) 3 points for tasks requiring dexterity and language, (2) 2 points for tasks needing dexterity but no language, and (3) 1 point for tasks using strength or minimal dexterity (see Figure 1). All informal observations were also given 1 point.

TASK

Colby and Parkison

WEI GHT

1. Draw . . . . . . . . . . . . . 3

2 . Write . . . . . . . . . . . . . 3

3. Stack blocks, number . . . . . . 2

4. Wind thread on spool (moving hand) 2

5. Spin top . . . . . . . . . . . . 1

6. S p o o n / F o r k . . . . . . . . . . 1

7. Throw . . . . . . . . . . . . . 1

8. Hammer . . . . . . . . . . . . 1

9. Turn pages . . . . . . . . . . . 1

10. Put marbles into bott le . . . . . . 1

11. Pull top off bott le . . . . . . . . 1

12. Unscrew l id . . . . . . . . . . 1

1 3 . S c i s s o r s . . . . . . . . . . . . 1

1 4 . R e a c h e s . . . . . . . . . . . . 1

15. Other informal observations

a . . . . . . . . . . . . . . 1

b . . . . . . . . . . . . . . !

C ~ * * �9 �9 �9 �9 �9 �9 �9 �9 �9 �9 �9 1

Handedness test items and their corresponding weights. Fig. 1.

During a testing session all the test items were put on the floor and the child was allowed to play with the ones he chose. We used little language to direct his play. To entice the child to perform a task, we would do it our- selves with either hand and then set the toy in front of him so that he could imitate the activity. If he would not try, we would start another task and return to the uncompleted one later in the testing. To ensure that the child was not ambilateral, we observed him doing each task more than once. All materials were picked up from the floor by the child; we did not hand him the materials.

Since the ages and abilities of the children varied, we did not expect each child to perform all the tasks. We considered a test sufficient if the child performed at least five of the listed activities. If the child completed fewer than five, we retested him on a different day. We scored the tests as follows: A point score was obtained for each of four possibilities by adding the weight of each activity attempted to one of the following subtotals: (a) right hand--per formed task with right hand only; (b) left hand- -per fo rmed

Handedness in Autistic Children 7

task with left hand only; (c) both--used both hands at the same time to per- form task; (d) ambilateral--performed task with either hand separately.

We totaled the points from the above four conditions, i.e., a + b + c + d = T, and obtained a percentage for each of the four conditions (x/T X 100, where x = a,b,c, or d). Since we counted only the tasks which the child performed, the total for each child cot~ld be different. A child was said to have a "right-hand preference" if he used only his right hand for at least 60070 of the items he tried. Under 60%, the child was considered a "non-right-hander."

RESULTS

It is clear from Tables II and Ill that the distribution of handedness differs greatly in our tested samples of autistic and normal children. In the autistic sample 65070 were non-right-handed by our test whereas in the normal sample 12070 were non-right-handed. The difference is of obvious statistical significance (chi square = 11.45, p < .001).

The well-known sex ratio of autism with a preponderance of males appears in both the hospital records and test data. There was no need for our normal controls to be matched in accordance with this ratio since handedness distributions between males and females in normal populations differ by only 1 to 2% (Hardyck & Petrinovich, 1976).

DISCUSSION

Our findings indicate that the distribution of handedness in autistic children differs greatly from that of normal children, with 65% of the autistic children being non-right-handed compared to 12070 of the normals.

Table II. Our Tested Sample of Autistic Children l _

Boys Girls Total

Right-handers 7 0 7 Left-handers 6 1 7 Ambilaterals 3 3 6

Total 16 4 20 %RH 43.8% .0% 35.0% %LH 37.5% 25.0% 35.0% %Ambi 18.7% 75.0% 30.0%

Total non-right- banders = 65.0%

8 Colby and Parkison

Table III. Our Tested Sample of Normal Children

Boys Girls Total

Right-handers 14 8 22 Left-handers 1 1 2 Ambilaterals 1 0 1 Total 16 9 25 %RH 87.5% 88.9% 88.0% %LH 6.25% 11.1% 8.8% %Ambi 6.25% .0% 4.4% Total non-right-

handers = 12.0%

Replication of these findings should be attempted by other investigators in other settings in order to establish factual status.

Not all the autistic children in our sample were non-right-handed, some (35%) appearing to be fully right-handed according to our criteria. This finding raises questions about possible subgroups in the autistic syndrome. The right-handers and non-right-handers might differ in respect to other properties. Are the non-right-handers those with histories of pregnancy/ birth complications? Are they the ones who develop epilepsy later in life? Do they have the greater language defects? Do they have superior or inferior right-hemisphere functions? Answers to such questions may lead to a more refined classification of subgroups of autism.

Since only 35o/0 of our tested autistic children are definitely right- handed compared to 88~ of our tested normals, this great difference suggests that the process of normal lateralization of cerebral functions fails in many autistic children. Whatever causes autism may also be responsible for a failure to lateralize. Damage to one cerebral hemisphere or its surgical removal early in life can result in the other hemisphere taking over the missing functions. If autism were simply the result of damage to the left hemisphere before birth or during the first few months of life, then homolo- gous areas in the right hemisphere should be able to carry out its functions such as language competence. However, this does not appear to be the case since autistic children have great difficulty using language. Hence one would be led to postulate that the cerebral damage is bilateral, affecting lan- guage areas in both hemispheres. Since a high percentage of autistic children are non-right-handed, we might assume they have failed to develop the usual left-hemisphere dominance. In those autistic children who are left- handed we do not know whether they are left- or right-cerebral dominant. Further studies will be necessary to decide this. Also, since we do not yet know the patterns of handedness in the families of autistic children our results have not excluded a genetic hypothesis. We would guess that the fre- quency of left-handedness is higher in autistic children than in their siblings

Handedness in Autistic Children 9

and relatives, but again further investigation would be required to rule out genotypic left-handedness which might somehow predispose to autism.

Failure to lateralize in the normal way is a clinical indicator of brain damage. Our results add to the now-strong evidence that autism results from some type of selective brain damage early in life. Since no thorough and extensive autopsy studies have yet been documented in the literature, little is known about the nature of the brain damage. With a shift or failure in cerebral dominance accompanied by defective language development, one would expect to find abnormalities in the hand and language areas of the cerebral cortex. However, the damage may not be observable at a gross or microscopic level. If cell studies show no abnormality, then the pathology might be analyzed at a molecular level.

It is striking how much difficulty autistic children have with all sym- bolic rules, not just those for language. As a speculation, we would suggest that to acquire symbolic rules requires synthesis of specific brain proteins. If an agent, such as a virus, has damaged some step in the DNA-RNA-pro- tein sequence for symbolic rules, it would be consistent with the clinical findings of the severe specific disabilities of autism in children with grossly and microscopically intact brains.

CONCLUSION

A test for handedness in a sample of 20 autistic and 25 normal children of approximately the same age indicated that the frequency of non- right-handedness is greatly increased in autistics (65%) as compared to normals (12%). This marked difference may have significance for the etiol- ogy of autism. Replications of these results should be attempted by others in the field to increase confidence in the reliability of these findings.

REFERENCES

Colby, K. M., & Kraemer, H. C. An objective measurement of nonspeaking children's per- formance with a computer-controlled program for the stimulation of language behavior. Journal of Autism and Childhood Schizophrenia, 1975, 5, 139-146.

Gesell, A., & Ames, L. B. The development of handedness. Journal of Genetic Psychology, 1947, 70, 155-175.

Hardyck, C., & Petrinovich, L. F. Left-handedness. Unpublished manuscript, 1976. Hauser, S. L., DeLong, R., & Rosman, M. P. Pneumographic findings in the infantile

autism syndrome. Brain, 1975, 98, 667-688. Levy, J. Psychobiological implications of bilateral asymmetry. In S. J. Dimond (Ed.), Hemi-

spheric function in the human brain. New York: Wiley, 1974. Ornitz, E. M., & Ritvo, E. R. The syndrome of autism: A critical review. American Journal

of Psychiatry, 1976, 133, 609-621. Satz, P. Left-handedness and early brain insult: An explanation. Neuropsychologia, 1973, 11,

115-117.