- Email: [email protected]
Handedness in Israel
Ncumpsyci~ologir. Vol. 17. pp. 83 to 87. Q PergamonPreu Ltd. 1979. Printed in Great Britain.
0028-3932/79/0101-008350200/0
NOTE HANDEDNESS Rum
SUERBERG,*
IN ISRAEL
LORAINEK. OBLER~and
HAROLD W. GORI)ON$
(Received 9 September 1978) Abstract-The handedness scores in 1171 Israeli high school students were found to be independent of ethnic origin, socio-economic class and reading direction. Contrary to other reports, sex differences were found neither between the mean handedness scores nor between the distribution of scores. The trends were in the expected direction-males were slightly less right handed than female-which was probably due to a higher percentage of males in the weak right handed range. The Israeli distribution was found to be significantly different from Taiwanese (11 and British [2] populations reported in the literature. Cultural and genetic factors giving rise to the differences in the distribution are discussed.
INTRODUCTION THE DISTRIBUTIONof
handedness has been attributed to a variety of factors including cultural demands [l], parental pressure [3], genetic factors [4,5], aging [6] and early hemispheric lesions [6,8]. The degree to which each of these contributes to the final hand use in all of the various unimanual tasks is undetermined. For example, in a Chinese population in Taiwan, use of the right hand was determined culturally for such tasks as eating and writing, but not necessarily for other unilateral tasks [l]. Children raised in orphanages are less right-handed than “privileged” children suggesting parental persuasion may influence handedness (91. The connection between handedness and cognitive functions, language in particular, has been reviewed [IO, 111but again no consistent point of view seems to emerge. Whereas it is true that left hemisphere speech representation is found in the overwhelming majority of right handers, non right handers have unpredictable lateralization but still with preference to the left hemisphere. In addition, non right handers or those with “mixed” eye-hand dominance appear to be over-represented in populations of subjects with dyslexia or stuttering [7]. Although evidence does not strongly support a causal relationship between handedness and those disorders [12], connection between handedness and cognitive functions is nevertheless apparent. In fact, one study seemed to imply a direct effect of learned behavior on cerebral dominance: subjects who read and write from right to left have significantly poorer right-left spatial orientation than those who read from left to right [13]. If cognitive functions are affected in a right to left reading population, handedness may also be influenced due to its relation to cerebral organization. In particular it could be argued that the deficits in spatial orientation could have resulted from a reduced lateral dominance for cognition as has been postulated for left handers (151and this in turn may affect hand control. 11 has also been claimed that the distribution of handedness is different for males than for females 12, 41 where males are either more left handed or less lateralized for the right hand. This observation does not support an argument that relates handedness and cognitive functions; males are repeatedly reported to have greater laterality of cognitive function [IS, 191 and according to the cognitive theory should be more right handed. A study is presented in which the influences of reading direction, cuItural background, socioeconomic group and sex on handedness were assessed. All subjects were teenagers who were native (99.2%) or near native (0.8 ‘A) speakers, readers and writers of Hebrew (written from right to left). However, the families of a larger percentage of the subjects had recently come from a variety of cultural backgrounds ranging from European or other Western countries to the Middle East and North African countries. Although not ‘Aranne Laboratory for Human Psychophysiology and Neurobehavioral Studies, Department of Neurology, Hadassah University Hospital, Jerusalem. tAphasia Research Center, Department of Neurology, Boston University Medical School and Boston VA Hospital, Boston, Massachusetts. SUnit of Behavioral Biology, Faculty of Medicine, Technion, Haifa. 83
a4
NOTE
literate in the language of their cultural ancestry, the subjects were likely to be inthtenced by many of the cultural habits of their parents. Thus in a single population, handedness could be assessed as a function of the influence of culture, socio-economic status and, of course, sex. In addition, our study could be compared to other published reports in order to determine the influence of reading direction.
SUBJECTS Subjects consisted of 1171 students, 528 male and 643 females, drawn from the last three grades of four local high schools in Jewish neighbourhoods of Jerusalem. Two of the high schools were vocational, whose students were primarily from families of lower and lower-middle class and two high schools were academic, whose students were from middle and upper-middle class families. All students attending class on the day of testing were included in the study. Classrooms consisting of about 35 subjects were tested one at a time.
METHODS Questionnaires including the ten items from the Edinburgh Handedness Inventory [2], were passed out to each classmember and instructions were read to the subjects. It was emphasized that since hand usage may differ from item to item, each response should be carefully considered. Adjacent to each item were five columns corresponding to the categories: “right hand only”, “right hand usually”, “both hands equally”, “left hand usually” and “left hand only”. For each item the subject was required to mark “X” in the column that best fit his hand use. In addition, there was a question for footedness (kicking) and eyedness (sighting). The subjects also reported age, sex, country of birth, year of immigration to Israel (if relevant) father’s country of birth and mother’s country of birth. Finally, each subject listed separately for each category all languages he spoke, read and understood. The entire procedure--instructions and completion of fonnsrequired the first 15 min of class time. A total of 1200 forms were collected, but 29 were discarded because they were inadequately completed. The handedness score for Laterality Quotient, LQ was determined by the method described by Oldfield [2] in which the difference in the number of items performed by the right and left hand (weighted according to reported strength of hand usage) was divided by the sum of items (also weighted). In this scoring method, weighting factors are relevant only if a subject reports use of the right hand for some items and left for others. Subjects reporting only left hand use, whether in the “left hand only” or “left hand usually” category would in either case have an LQ of - 100. Similarly, subjects who reported only right hand usage in their category would have an LQ of + 100.
DISCUSSION The measurement of handedness was not different among groups divided by the social and environmental factors of ethnic origin or socio-economic background. The two most distinctive cultural groups were those of the West (American and European) and those of the East (North African and the Middle East) and the mean LQ was not different between them (I = 1.05, P > 0.2). Similarly, the mean handedness score was not different (t = 0) for the groups redivided according to socio-economic level as roughly determined by attendance in either the academic or vocational high school. Within the present population, direction of reading also did not appear to be a factor in hand preference. There was no difference (t = 0.79) between subjects who read only right to left (Hebrew and other semitic languages;, as compared to Hebrew reading subjects who also read left to right (Indo-European languages). Sex differences in the mean handedness score were not found in the present population. The mean handedness score for females was 69 (S.D. + 53) and males, 67 (S.D. f 52). Although this difference was not significant (r = 0.47) the trend was for a lower mean score for males (see Fig. 1). Even though cultural background and reading directions did not appear to influence the degree of handedness, it was convenient to compare our results with two other populations which were likely to be more homogeneous than our own, yet-represent different cultural and language settings. The first nonulation was from Great Britain containing 1027 college students. 360 males and 661 females [2]. Since the-;aw data was not available the distribution-of subjects-was approximated from Fig. 3 of that study in the following way: the graph of LQ vs frequency (per mil) was enlarged by projecting it on to a wall. Precautions were taken to insure that the graph was not distorted. From this magnified projection, the frequencies for each decade were measured directly and transformed to numbers of subjects. The error in the total number of subjects obtained overestimated the reported total by about 5 %. Because of the larger numbers of subjects involved in the right hand LQ decades, it is more likely that the greater errors occurred in this area.
NOTE
LATEPALITY FIG. 1.
Frequency distribution
OUOTIENT
RANGE
of laterality quotient for Israeli population.
The second population was 4143 Chinese (Taiwan), 2073 males and 2070 females. The frequency of subjects in each decade for all ten items of the questionnaire was generously made available by Dr. E. Lee-Teng. These data included the two items, eating and writing, for which there was a reported bias for right hand use [l]. The laterality quotients of all three populations were determined similarly from the Edinburgh Handedness Inventory and thus could be compared to each other. The handedness data of the three populations were regrouped into 10 categories,* and the resulting distributions were compared for the three possible pairs using the Komogorov-Smirnov two-tailed test 1201. All pairs were significantly different from each other (P < 0.001). The Israeli population had larger proportions of subjects in the extreme left as well as the extreme right categories of the curve than either the Taiwanese or the British. What is surprising is that the larger proportion of Israeli subjects in the extreme right category occurs in spite of the cultural bias of the Taiwanese in that direction. The distribution of British and Taiwanese were more similar except for a proportionately larger number of Taiwanese subjects at the extreme right. The greater proportion of Israeli subjects in the extreme left handed category was notably larger in relation to the Taiwanese. who had nearly no subjects, and marginally larger when compared to the British. The distribution of handedness for the male population in each country was found to differ significantly from every other male distribution. Similarly, every female distribution differed from every other female distribution (all P’s < 0.001, Komogorov-Smimov test, two-tailed). Furthermore, the difference between the male and between the female distributions of each culture reflected the same difference between distribution of the parent populations. Again, the Israeli males and females were found in greater proportions of the extremes than the other males and females. The male-female distributions were compared in the British and in the Taiwanese populations. In contrast to the lack of sex differences in the Israeli population, the Taiwanese male distribution was significantly different from that of the Taiwanese female (P c 0.001). This is consistent with the report that the average male LQ was significantly lower than the female LQ [l]. However, there was no difference between the male and female distributions in the British population even though a significant difference between the LQ’s had also been reported [2].
DISCUSSION Distribution of handedness was found to be independent of social and environmental factors such as ethnic origin, socio-economic class or direction of reading. There was no evidence that subjects from poorer economic backgrounds were more right or left handed than their more well-to-do counterparts. Nor were there differences betwen thosesubjects whosefamilies came from Western countries and those whose families came from Eastern countries. However, the effect of culture cannot satisfactorily account for the differences between the Israeli population and the Taiwanese. The greater numbers of Israelis in the right hand group *~e~tego~~were:(l)-l~to-~1,(2)-~0to-~1,(3)-~0to+30,(4)+31 to-t40,(5)+41 (6) +51 to +60, (7) +61 to +70, (8) +71 to +80, (9) + 81 to +90, (10) + 91 to 4100.
to+50,
NOTE
86
is especially significant since the Taiwancse population was already biased in this direction by cdtural factors that had predetermined right hand use for at least two out of the ten items on the questionnaire (11. No such item bias wx apparent in the Israeli population and yet there were greater percentages of subjects in the right extreme. However, the greater difference between the Israeli and the Taiwancsc populations was in the moderate right hand region, whereas the Taiwancse did not differ from the British in this area. However, the Taiwanese would probably have had an even greater proportion of subjects here. had the reported cultural bias been eliminated. Another cultural influence on the pattern of responses could be the response attitude itself. For example, subjects who tend to respond more categorically would mark all items of the questionnaire either “right” or “left” when their hand use was actually less absolute. A similar argument has already been used to explain sex differences in handedness [21] where males tended to be less likely to use extreme categories, thereby accounting for their lower proportions in the extreme right handed categories. The scoring system partly accounts for such a bias since it does not distinguish between subjects who answer always in the “only” categories, and subjects who answer only in the “usually” categories. In fact, in the Taiwanese study these two categories were not differentiated. Since culture, s&o-economic class and ethnic group cannot adequately account for the differences among distributions both between populations across cultures and between sexes within cultures, other major factors must be considered. Undoubtedly, the most important of these and one which was not tested by our study is genetic expression [4,5]. Whereas a number of models have been proposed to explain handedness distribution according to inherited characteristics, none have proven to be completely satisfactory [22]. The sex differences found in most handedness distributions and the cultural differences found in the present study emphasize the need for elaboration of these models. Sex differences are also well-known for cognitive functions, and some of these have been shown to be genetically determined [23]. It cannot be ruled out that a genetic sex linkage to handedness might exist as well. Furthermore, different cultures reportedly have cognitive styles that reflect differences in cultural organization [24]. Although there is no positive evidence that sex and cultural differences in handedness distributions are genetically determined, our data rule out some of the environmental factors. Acknow!edgemenrs-The authors acknowledge the help and cooperation of the Jerusalem Board of Education and the principals and teachers of Bezek, Seligsburg, Beit Hakerem and Gymnasia HaIvrit High Schools. We thank Dr. 2. GILULAfor his professional advice and performing the statistical analyses.
REFERENCES 1. TENT, E. L., LEE, P., YANTE, K. and CHANG, P. C. Handedness in a Chinese population: biological, social and pathological factors. Science 193, 1148-1150, 1977. 2. OLDFIELD,R. C. The assessment and analysis of handedness: the Edinburgh Inventory. Neuropsychologia 9,97-113, 1971. 3. FALEK,A. Handedness: a family study. Am. J. Hum. Genet. 11,52-62,1959. 4. Am, M. Binomial distribution of right, mixed and left handedness. Q. J. exp. Psychol. 19,327-333, 1967. 5. LEW, J. and NAGYLAKI,T. A model for the genetics of handedness. Genetics 72,117-128,1972. 6. FLEMINGER,J. J., DALTON,R. and STANDAGE,K. F. Age as a factor in the handedness of adults. Neuropsychologia 15,471-473, 1977. 7. HBCAEN,H. and DE AJURIAGUERRA, J. Lefr Handedness. Grune & Stratton, New York, 1964. 8. GORDON,H. Left handedness and mirror writing especially among defective children. Brain 43,313-365, 1920. 9. SUBIRANA,A. Cerebral dominant.
10. 11. 12. 13. 14.
In Ha&book of Clinical Neurology. _. P. J. VINKENand G. W. BRUYN (Editors),Vol. 4, p. 253, 1967. HARDYCK,C. and PETRINOV,L. F. 1 :ft handedness. Psychol. Bull. 84,385a, 1977. ZANGWILL,0. The ontogeny of cerrbral dominance in man. In Foundations of Language Development. H. LENNEBERG and E. LENNEBERG(Editors), pp. 137-145. Academic Press, New York, 1975. ZANGWILL, 0. Cerebral Dominance and its Relation to Psychological Functioning. Oliver & Boyd, Edinburgh, 1960. ALBERT.M. L. Cerebral dominance and reading habits. Nature 256.403-407. 1975. LEW, i Possible basis for the evoluticn of iateral specialization of the human brain. Nature 224, 614-615,
1949.
15. LEVY, J. Lateral specialization of the human brain behavioral manifestations and possible evolutionary basis. In Biology ofBehavior. J. A. KIGER (Editor). Oregon State Univ. Press, Oregon, 1972. 16. B~ERI,J., BRADBURN,W. M. and GALINSKY,M. D. Sex differences in perceptual behavior. J. Personality 26, 1-12, 1958.
NtY?lJ
87
R. Genetic analysis of analytic spatial ability: Raven’s progressivematrices.Behav. Gmetics
17. GUN,
4,273-284.1974.
18. Wmu~, H. A. Individual differences in case of perception of embedded figures. /. Personality 19,1-lS, 1950. 19. MCGLOM, J. and D~vuxorr, W. The relation between cerebral speech Iatcrality and spatial ability with special reference to sex and hand preference. Neuropsychologia 11, 105-l 13, 1973. 20. SIEGEL,S. Non Paramefric Stafisficsfir Behavioral Sciences, pp. 127-135. Kogakusha (McGraw-Hill), Tokyo, 1956. 21. BRYDEN.M. P. Measuring handedness with questionnaires. Neuropsychologia 15,617-624, 1977. 22. HICKS. R. C., K~XSBOUR>T,M. On the genesis of human handedness: a review. J.MotorBehuv. 8, 257-266, 1916. 23. Boclr, R. D. and KOLAKOWSKJ, 0. Further evidence of sex-linked major gene influence on humanspatial visual ability. Am. /. Hum. Genetics 25,I-14, 1973.
24.BOGEN,J. E., DE ZURE, R., TENHOUTEN,W. D. and MARSH,J. F. The other side of the brain-IV. A-P ratio. Bull. Los Ang. Neural. Sot. 37(2). 49-61, 1972.
tisumd
:
On a trouv6 que les scores de preference 1171 coll6giens Isr.&liens Btaient independants de la classe socio+conomique
manuelle
chez
de l'origine ethnique,
et du sens de la lecture. Contrairement
Zld'autres rlsultats, on ne trouvait pas de difference
selon le sexe
ni entre le score moyen de prdference manuelle ni dans la distribution des scores. Les tendances se manifestaient dans la direction attendue c'est-a-dire que les garqons Btaient l$gSrement wins droitiers que les filles
mais
ceci
6tait probablement
dli a un pourcentage
de garyons parmi les droitiers faibles. La distributia Israeliens etait treuv6e significativement tee dans les populations de Taiwan
superieur
chez les
differente de celle consta-
(1) et d'Anqleterre
(2). On discute
les facteurs culture1 et genetique qui peuvent rendre compte des diff& rences de distribution.
Deutschsprachige Zusammenfassung: Bei 1171 israelischen Oberschiilernzeigten sich die HBndigkeitswerte unabhgngig von der ethnischen Herkunft, der sozio8konomischen Klassenzugehiirigkeitund der Leserichtung der Probanden. Im Gegensatz zu anderen Berichten fanden sich Geschlechtsunterschiede weder bei den durchschnittlichen Hgndigkeitswerten noch bei der Verteilung der Werte. Die Trends gingen in die erwartete Richtung, die mCinnlichenProbanden waren e'cwasweniger stark ausgeprsgte RechtshXnder als die weiblichen, was wahrscheinlich auf einen hijherenAnteil voti H8nnern in der Gruppe der Schwach-Rechtshadigen zuriickzu-. fiihrenwar. Die Verteilung bei der israelischen Gruppe unterschied sich signifikant von den in der Literatur dargestellten taiwanischen und britischen Grqppen. Kulturelle und genetische Faktoren, die fiirdie Unterschiede in der Verteilung verantwortlich sein kb;nnten,werden diskutiert.
The
0028-3932/79/0101-008350200/0
NOTE HANDEDNESS Rum
SUERBERG,*
IN ISRAEL
LORAINEK. OBLER~and
HAROLD W. GORI)ON$
(Received 9 September 1978) Abstract-The handedness scores in 1171 Israeli high school students were found to be independent of ethnic origin, socio-economic class and reading direction. Contrary to other reports, sex differences were found neither between the mean handedness scores nor between the distribution of scores. The trends were in the expected direction-males were slightly less right handed than female-which was probably due to a higher percentage of males in the weak right handed range. The Israeli distribution was found to be significantly different from Taiwanese (11 and British [2] populations reported in the literature. Cultural and genetic factors giving rise to the differences in the distribution are discussed.
INTRODUCTION THE DISTRIBUTIONof
handedness has been attributed to a variety of factors including cultural demands [l], parental pressure [3], genetic factors [4,5], aging [6] and early hemispheric lesions [6,8]. The degree to which each of these contributes to the final hand use in all of the various unimanual tasks is undetermined. For example, in a Chinese population in Taiwan, use of the right hand was determined culturally for such tasks as eating and writing, but not necessarily for other unilateral tasks [l]. Children raised in orphanages are less right-handed than “privileged” children suggesting parental persuasion may influence handedness (91. The connection between handedness and cognitive functions, language in particular, has been reviewed [IO, 111but again no consistent point of view seems to emerge. Whereas it is true that left hemisphere speech representation is found in the overwhelming majority of right handers, non right handers have unpredictable lateralization but still with preference to the left hemisphere. In addition, non right handers or those with “mixed” eye-hand dominance appear to be over-represented in populations of subjects with dyslexia or stuttering [7]. Although evidence does not strongly support a causal relationship between handedness and those disorders [12], connection between handedness and cognitive functions is nevertheless apparent. In fact, one study seemed to imply a direct effect of learned behavior on cerebral dominance: subjects who read and write from right to left have significantly poorer right-left spatial orientation than those who read from left to right [13]. If cognitive functions are affected in a right to left reading population, handedness may also be influenced due to its relation to cerebral organization. In particular it could be argued that the deficits in spatial orientation could have resulted from a reduced lateral dominance for cognition as has been postulated for left handers (151and this in turn may affect hand control. 11 has also been claimed that the distribution of handedness is different for males than for females 12, 41 where males are either more left handed or less lateralized for the right hand. This observation does not support an argument that relates handedness and cognitive functions; males are repeatedly reported to have greater laterality of cognitive function [IS, 191 and according to the cognitive theory should be more right handed. A study is presented in which the influences of reading direction, cuItural background, socioeconomic group and sex on handedness were assessed. All subjects were teenagers who were native (99.2%) or near native (0.8 ‘A) speakers, readers and writers of Hebrew (written from right to left). However, the families of a larger percentage of the subjects had recently come from a variety of cultural backgrounds ranging from European or other Western countries to the Middle East and North African countries. Although not ‘Aranne Laboratory for Human Psychophysiology and Neurobehavioral Studies, Department of Neurology, Hadassah University Hospital, Jerusalem. tAphasia Research Center, Department of Neurology, Boston University Medical School and Boston VA Hospital, Boston, Massachusetts. SUnit of Behavioral Biology, Faculty of Medicine, Technion, Haifa. 83
a4
NOTE
literate in the language of their cultural ancestry, the subjects were likely to be inthtenced by many of the cultural habits of their parents. Thus in a single population, handedness could be assessed as a function of the influence of culture, socio-economic status and, of course, sex. In addition, our study could be compared to other published reports in order to determine the influence of reading direction.
SUBJECTS Subjects consisted of 1171 students, 528 male and 643 females, drawn from the last three grades of four local high schools in Jewish neighbourhoods of Jerusalem. Two of the high schools were vocational, whose students were primarily from families of lower and lower-middle class and two high schools were academic, whose students were from middle and upper-middle class families. All students attending class on the day of testing were included in the study. Classrooms consisting of about 35 subjects were tested one at a time.
METHODS Questionnaires including the ten items from the Edinburgh Handedness Inventory [2], were passed out to each classmember and instructions were read to the subjects. It was emphasized that since hand usage may differ from item to item, each response should be carefully considered. Adjacent to each item were five columns corresponding to the categories: “right hand only”, “right hand usually”, “both hands equally”, “left hand usually” and “left hand only”. For each item the subject was required to mark “X” in the column that best fit his hand use. In addition, there was a question for footedness (kicking) and eyedness (sighting). The subjects also reported age, sex, country of birth, year of immigration to Israel (if relevant) father’s country of birth and mother’s country of birth. Finally, each subject listed separately for each category all languages he spoke, read and understood. The entire procedure--instructions and completion of fonnsrequired the first 15 min of class time. A total of 1200 forms were collected, but 29 were discarded because they were inadequately completed. The handedness score for Laterality Quotient, LQ was determined by the method described by Oldfield [2] in which the difference in the number of items performed by the right and left hand (weighted according to reported strength of hand usage) was divided by the sum of items (also weighted). In this scoring method, weighting factors are relevant only if a subject reports use of the right hand for some items and left for others. Subjects reporting only left hand use, whether in the “left hand only” or “left hand usually” category would in either case have an LQ of - 100. Similarly, subjects who reported only right hand usage in their category would have an LQ of + 100.
DISCUSSION The measurement of handedness was not different among groups divided by the social and environmental factors of ethnic origin or socio-economic background. The two most distinctive cultural groups were those of the West (American and European) and those of the East (North African and the Middle East) and the mean LQ was not different between them (I = 1.05, P > 0.2). Similarly, the mean handedness score was not different (t = 0) for the groups redivided according to socio-economic level as roughly determined by attendance in either the academic or vocational high school. Within the present population, direction of reading also did not appear to be a factor in hand preference. There was no difference (t = 0.79) between subjects who read only right to left (Hebrew and other semitic languages;, as compared to Hebrew reading subjects who also read left to right (Indo-European languages). Sex differences in the mean handedness score were not found in the present population. The mean handedness score for females was 69 (S.D. + 53) and males, 67 (S.D. f 52). Although this difference was not significant (r = 0.47) the trend was for a lower mean score for males (see Fig. 1). Even though cultural background and reading directions did not appear to influence the degree of handedness, it was convenient to compare our results with two other populations which were likely to be more homogeneous than our own, yet-represent different cultural and language settings. The first nonulation was from Great Britain containing 1027 college students. 360 males and 661 females [2]. Since the-;aw data was not available the distribution-of subjects-was approximated from Fig. 3 of that study in the following way: the graph of LQ vs frequency (per mil) was enlarged by projecting it on to a wall. Precautions were taken to insure that the graph was not distorted. From this magnified projection, the frequencies for each decade were measured directly and transformed to numbers of subjects. The error in the total number of subjects obtained overestimated the reported total by about 5 %. Because of the larger numbers of subjects involved in the right hand LQ decades, it is more likely that the greater errors occurred in this area.
NOTE
LATEPALITY FIG. 1.
Frequency distribution
OUOTIENT
RANGE
of laterality quotient for Israeli population.
The second population was 4143 Chinese (Taiwan), 2073 males and 2070 females. The frequency of subjects in each decade for all ten items of the questionnaire was generously made available by Dr. E. Lee-Teng. These data included the two items, eating and writing, for which there was a reported bias for right hand use [l]. The laterality quotients of all three populations were determined similarly from the Edinburgh Handedness Inventory and thus could be compared to each other. The handedness data of the three populations were regrouped into 10 categories,* and the resulting distributions were compared for the three possible pairs using the Komogorov-Smirnov two-tailed test 1201. All pairs were significantly different from each other (P < 0.001). The Israeli population had larger proportions of subjects in the extreme left as well as the extreme right categories of the curve than either the Taiwanese or the British. What is surprising is that the larger proportion of Israeli subjects in the extreme right category occurs in spite of the cultural bias of the Taiwanese in that direction. The distribution of British and Taiwanese were more similar except for a proportionately larger number of Taiwanese subjects at the extreme right. The greater proportion of Israeli subjects in the extreme left handed category was notably larger in relation to the Taiwanese. who had nearly no subjects, and marginally larger when compared to the British. The distribution of handedness for the male population in each country was found to differ significantly from every other male distribution. Similarly, every female distribution differed from every other female distribution (all P’s < 0.001, Komogorov-Smimov test, two-tailed). Furthermore, the difference between the male and between the female distributions of each culture reflected the same difference between distribution of the parent populations. Again, the Israeli males and females were found in greater proportions of the extremes than the other males and females. The male-female distributions were compared in the British and in the Taiwanese populations. In contrast to the lack of sex differences in the Israeli population, the Taiwanese male distribution was significantly different from that of the Taiwanese female (P c 0.001). This is consistent with the report that the average male LQ was significantly lower than the female LQ [l]. However, there was no difference between the male and female distributions in the British population even though a significant difference between the LQ’s had also been reported [2].
DISCUSSION Distribution of handedness was found to be independent of social and environmental factors such as ethnic origin, socio-economic class or direction of reading. There was no evidence that subjects from poorer economic backgrounds were more right or left handed than their more well-to-do counterparts. Nor were there differences betwen thosesubjects whosefamilies came from Western countries and those whose families came from Eastern countries. However, the effect of culture cannot satisfactorily account for the differences between the Israeli population and the Taiwanese. The greater numbers of Israelis in the right hand group *~e~tego~~were:(l)-l~to-~1,(2)-~0to-~1,(3)-~0to+30,(4)+31 to-t40,(5)+41 (6) +51 to +60, (7) +61 to +70, (8) +71 to +80, (9) + 81 to +90, (10) + 91 to 4100.
to+50,
NOTE
86
is especially significant since the Taiwancse population was already biased in this direction by cdtural factors that had predetermined right hand use for at least two out of the ten items on the questionnaire (11. No such item bias wx apparent in the Israeli population and yet there were greater percentages of subjects in the right extreme. However, the greater difference between the Israeli and the Taiwancsc populations was in the moderate right hand region, whereas the Taiwancse did not differ from the British in this area. However, the Taiwanese would probably have had an even greater proportion of subjects here. had the reported cultural bias been eliminated. Another cultural influence on the pattern of responses could be the response attitude itself. For example, subjects who tend to respond more categorically would mark all items of the questionnaire either “right” or “left” when their hand use was actually less absolute. A similar argument has already been used to explain sex differences in handedness [21] where males tended to be less likely to use extreme categories, thereby accounting for their lower proportions in the extreme right handed categories. The scoring system partly accounts for such a bias since it does not distinguish between subjects who answer always in the “only” categories, and subjects who answer only in the “usually” categories. In fact, in the Taiwanese study these two categories were not differentiated. Since culture, s&o-economic class and ethnic group cannot adequately account for the differences among distributions both between populations across cultures and between sexes within cultures, other major factors must be considered. Undoubtedly, the most important of these and one which was not tested by our study is genetic expression [4,5]. Whereas a number of models have been proposed to explain handedness distribution according to inherited characteristics, none have proven to be completely satisfactory [22]. The sex differences found in most handedness distributions and the cultural differences found in the present study emphasize the need for elaboration of these models. Sex differences are also well-known for cognitive functions, and some of these have been shown to be genetically determined [23]. It cannot be ruled out that a genetic sex linkage to handedness might exist as well. Furthermore, different cultures reportedly have cognitive styles that reflect differences in cultural organization [24]. Although there is no positive evidence that sex and cultural differences in handedness distributions are genetically determined, our data rule out some of the environmental factors. Acknow!edgemenrs-The authors acknowledge the help and cooperation of the Jerusalem Board of Education and the principals and teachers of Bezek, Seligsburg, Beit Hakerem and Gymnasia HaIvrit High Schools. We thank Dr. 2. GILULAfor his professional advice and performing the statistical analyses.
REFERENCES 1. TENT, E. L., LEE, P., YANTE, K. and CHANG, P. C. Handedness in a Chinese population: biological, social and pathological factors. Science 193, 1148-1150, 1977. 2. OLDFIELD,R. C. The assessment and analysis of handedness: the Edinburgh Inventory. Neuropsychologia 9,97-113, 1971. 3. FALEK,A. Handedness: a family study. Am. J. Hum. Genet. 11,52-62,1959. 4. Am, M. Binomial distribution of right, mixed and left handedness. Q. J. exp. Psychol. 19,327-333, 1967. 5. LEW, J. and NAGYLAKI,T. A model for the genetics of handedness. Genetics 72,117-128,1972. 6. FLEMINGER,J. J., DALTON,R. and STANDAGE,K. F. Age as a factor in the handedness of adults. Neuropsychologia 15,471-473, 1977. 7. HBCAEN,H. and DE AJURIAGUERRA, J. Lefr Handedness. Grune & Stratton, New York, 1964. 8. GORDON,H. Left handedness and mirror writing especially among defective children. Brain 43,313-365, 1920. 9. SUBIRANA,A. Cerebral dominant.
10. 11. 12. 13. 14.
In Ha&book of Clinical Neurology. _. P. J. VINKENand G. W. BRUYN (Editors),Vol. 4, p. 253, 1967. HARDYCK,C. and PETRINOV,L. F. 1 :ft handedness. Psychol. Bull. 84,385a, 1977. ZANGWILL,0. The ontogeny of cerrbral dominance in man. In Foundations of Language Development. H. LENNEBERG and E. LENNEBERG(Editors), pp. 137-145. Academic Press, New York, 1975. ZANGWILL, 0. Cerebral Dominance and its Relation to Psychological Functioning. Oliver & Boyd, Edinburgh, 1960. ALBERT.M. L. Cerebral dominance and reading habits. Nature 256.403-407. 1975. LEW, i Possible basis for the evoluticn of iateral specialization of the human brain. Nature 224, 614-615,
1949.
15. LEVY, J. Lateral specialization of the human brain behavioral manifestations and possible evolutionary basis. In Biology ofBehavior. J. A. KIGER (Editor). Oregon State Univ. Press, Oregon, 1972. 16. B~ERI,J., BRADBURN,W. M. and GALINSKY,M. D. Sex differences in perceptual behavior. J. Personality 26, 1-12, 1958.
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R. Genetic analysis of analytic spatial ability: Raven’s progressivematrices.Behav. Gmetics
17. GUN,
4,273-284.1974.
18. Wmu~, H. A. Individual differences in case of perception of embedded figures. /. Personality 19,1-lS, 1950. 19. MCGLOM, J. and D~vuxorr, W. The relation between cerebral speech Iatcrality and spatial ability with special reference to sex and hand preference. Neuropsychologia 11, 105-l 13, 1973. 20. SIEGEL,S. Non Paramefric Stafisficsfir Behavioral Sciences, pp. 127-135. Kogakusha (McGraw-Hill), Tokyo, 1956. 21. BRYDEN.M. P. Measuring handedness with questionnaires. Neuropsychologia 15,617-624, 1977. 22. HICKS. R. C., K~XSBOUR>T,M. On the genesis of human handedness: a review. J.MotorBehuv. 8, 257-266, 1916. 23. Boclr, R. D. and KOLAKOWSKJ, 0. Further evidence of sex-linked major gene influence on humanspatial visual ability. Am. /. Hum. Genetics 25,I-14, 1973.
24.BOGEN,J. E., DE ZURE, R., TENHOUTEN,W. D. and MARSH,J. F. The other side of the brain-IV. A-P ratio. Bull. Los Ang. Neural. Sot. 37(2). 49-61, 1972.
tisumd
:
On a trouv6 que les scores de preference 1171 coll6giens Isr.&liens Btaient independants de la classe socio+conomique
manuelle
chez
de l'origine ethnique,
et du sens de la lecture. Contrairement
Zld'autres rlsultats, on ne trouvait pas de difference
selon le sexe
ni entre le score moyen de prdference manuelle ni dans la distribution des scores. Les tendances se manifestaient dans la direction attendue c'est-a-dire que les garqons Btaient l$gSrement wins droitiers que les filles
mais
ceci
6tait probablement
dli a un pourcentage
de garyons parmi les droitiers faibles. La distributia Israeliens etait treuv6e significativement tee dans les populations de Taiwan
superieur
chez les
differente de celle consta-
(1) et d'Anqleterre
(2). On discute
les facteurs culture1 et genetique qui peuvent rendre compte des diff& rences de distribution.
Deutschsprachige Zusammenfassung: Bei 1171 israelischen Oberschiilernzeigten sich die HBndigkeitswerte unabhgngig von der ethnischen Herkunft, der sozio8konomischen Klassenzugehiirigkeitund der Leserichtung der Probanden. Im Gegensatz zu anderen Berichten fanden sich Geschlechtsunterschiede weder bei den durchschnittlichen Hgndigkeitswerten noch bei der Verteilung der Werte. Die Trends gingen in die erwartete Richtung, die mCinnlichenProbanden waren e'cwasweniger stark ausgeprsgte RechtshXnder als die weiblichen, was wahrscheinlich auf einen hijherenAnteil voti H8nnern in der Gruppe der Schwach-Rechtshadigen zuriickzu-. fiihrenwar. Die Verteilung bei der israelischen Gruppe unterschied sich signifikant von den in der Literatur dargestellten taiwanischen und britischen Grqppen. Kulturelle und genetische Faktoren, die fiirdie Unterschiede in der Verteilung verantwortlich sein kb;nnten,werden diskutiert.
The