Neuropsyholosia. Vol. 17. pp. 533 10 537. cj Pcrg3mon Press Ltd. 1979. Printed in Great Brlmin.
NOTE RELATIONSHIPS
AMONG
SEX AND
HANDEDNESS,
OCULAR PAUL
Department
of Psychology,
HANDEDNESS,
BIRKETT*
University (Received
FAMILIAL
SIGHTING-DOMINANCE
of Liverpool,
Liverpool
L69 3BX, England
I5 March 1979)
Abstract-Fifty-four males and 71 females were tested on a measure of handedness and a measure of ocular sighting-dominance. Familial handedness was also ascertained via the handedness questionnaire. There were no sex or handedness differences in the incidence of familial sinistrality. Handedness, sex and familial handedness affected sighting-dominance in complex and unexpected ways. It is suggested that these variables, as well as others not tested here, will need to be considered in future studies of ocular laterality and its relationship to functional cerebral asymmetries.
SEVERAL variables have been investigated in attempts to determine which organismic factors are most closely associated with hemispheric asymmetries of function. Four such variables are sex, handedness, familial handedness and ocular sighting-dominance. There is at least some evidence for the intluence on cerebral lateralization of each one of these variables, either alone or in combination [e.g. l-9). Despite such evidence, there is little agreement as to the nature of the relationships amongst these variables themselves. Hand-eye dominance has been closely studied and has produced conflicting reports of high (IO-131 and low [I+163 associations. The role of sex in moderating these associations has been investigated and has also proved inconsistent. GUK and GUR [IO, 161 reported that handedness and sighting-dominance were related for males but not for females; both left and right handed females fended to sight with the right eye. However, in their later study [I61 left-handers numbered only 11 out of a total of 200 subjects and only 6 of these were female. CKOVITZ [I71 found that right-handers of both sexes tended to sight with their right eye but that lefthanded males were inconsistent sighters and left-handed females were very slightly biased towards right eye-sighting. These results tvere not discussed by Cur and Gur in their later paper but generally agree with their data, apart from the discrepancies in left-handers. Handedness was not considered in a study by PORAC and COREN [I81 who concluded that, whilst males were more likely than females to display ipsilateral hand-eye dominance, there were no sex-differences in the proportions of left and right eye-sighters. The main aim of the present study was to determine whether any of the above findings were replicable with diRerent handedness and eye dominance tests and using sufficient left-handers of both sexes. However, in view of the contradictory results for left-handers, and since familial handedness is known to influence cerebral asymmetries [Z-4], it was decided to include familial handedness as a variable in order to increase the precision of our results. Whilst it was not expected that the inclusion of this variable would account for all the unexplained variance in previous reports, it did seem likely that some erects would be observed. If eye dominance is one facet of a “generalized laterality”, one might expect familial left-handedness to increase eye-hand concordance in left-handers but to decrease it in right-handers. Of secondary interest in the present study were the relationships among sex, handedness and familial handedness. Of two studies of sex-differences in familial sinistrality one reported a higher incidence for females [I91 and one found no sex-difference [20]. In view of evidence that gender may play a moderating role in the inheritance of handedness [II-231 this question remains of general interest.
*The experimental work reported here was carried out as part of the author’s Ph.D. research Institute of Technology. Thanks are extended to my thesis supervisors, Dr. R. H. RANYARD and GATEHOUSE. -
533
at Bolton CHRISTISE
534
NOTE
The work of B~K-\u and his colleagues on birth stress and left-handedness (2-I. 251 argues for a higher incidence of familial sinistrality in left-handers, although the model proposed by SATZ [26. 271 suggests that this will be true only for those left-handers whose handedness is inherited and not determined by birthtrauma. Genetic theories of handedness naturally predict more familial sinistrality in left-handers [e.g. 21, 281. Although intensive family studies will provide the most reliable data, we examined our results for any signs of a relationship. Two previous studies with normal subjects found positive (191 and negative [20] evidence for the influence of familial sinistrality on handedness, whilst H~CAEN and SAUGUET (41 reported that it related to weaker left-handedness in a brain-damaged sample.
METHOD The sample consisted of I25 normal volunteers drawn from schools, colleges and the general public in the Bolton area of Lancashire. There were 54 males and 7 I females aged between I6 and 42 years (x = 22.5). Subjects were paid an hourly fee for participation. Some prior selection of subjects on the basis of sex and handedness was necessary in order to obtain roughly equivalent numbers in each sex handedness group. Hence, sex-differences in the incidence of left- and right-handedness were not examined here. Materials and procedure (1) Handedness questionnaire. OLDFIELD’S [29] Edinburgh Handedness Inventory was administered to all subjects individually. This instrument has IO items which were shown to be reliably intercorrelated in Oldfield’s original standardization on II00 subjects. The score ranges from - 100 (completely left-handed) to f 100 (completely right-handed). (2) Eye-dominance resf. MILES’S [I I] A-B-C Vision Test for ocular sighting-dominance was administeredto all subjects individually. For this test the subject covers his or her face with the wide end of a truncated cone held with both hands and peers at targets (small cards containing various shapes) about IO ft away. The subjective experience is that alignment of the cone is effected by placing it midway between the two eyes. This cannot be so however; the target may only be seen when the aperture at the narrow end of the cone is aligned with one eye or the other. The eye selected most often over a series of IO trials is the dominant eye for sighting. The cone itself is replaced by an identical one from time to time to prevent a subject’s response being influenced by maintainance of posture. The two tests described were given in counterbalanced order over subjects.
RESULTS
AND
DISCUSSION
Handedness classification A subject was designated left-handed if his or her score fell below the zero point on the inventory and as right-handed if he or she scored above zero. Obviously, there will be some ambilaterals in each groups as a result of such a classification. Nevertheless, the mean handedness scores were -65.6 for left-handers (n = 52) and f64.5 for right-handers (n = 73). These scores were sufficiently disparate to consider the two groups as distinct, particularly in view of the general tendency for left-handers to display considerable ambilaterality of hand usage [30]. Familial handedness was ascertained by asking subjects to indicate on the inventory whether any of their relatives showed any signs of left-handedness. The replies were followed up by questioning to determine the reliability and exact nature of any familial sinistrality. A subject was designated as a familial sinistral if he or she professed to have at least one first-degree relative or two second-degree relatives with tendencies towards left-handedness. Thirty-two of the I25 subjects were so-designated. Eye dominance classification Since no subject proved markedly inconsistent on the A-B-C vision test, it was possible to classify individuals as left or right eye-dominant on the basis of the eye most frequently used for sighting. Seventy-seven subjects were left-eyed and 48 were right-eyed. Table I gives the distribution of subjects classified by sex, familial handedness, handedness and eyedominance. FSi and FS- refer respectively to presence and absence of familial sinistrality. To test the eye-hand dominance relationship alone, results were collapsed over sex and familial handedness. Right-handers had approximately equal numbers sighting with the left [39] and right [34] eye, whilst left-handers displayed a preference for left [38] as opposed to right [I41 eye-sighting, x2 = 4.16, d./. = I, P c 0.05. This is counter to the usual observation of less consistent sighting-dominance in left-handers [e.g. 15, 17). The part played by sex in moderating concordance of eye-hand usage was examined by combining the familial handedness groups as shown in Table I and analysing the 2 (sex) X 4 (eye-hand combinations) matrix for homogeneity. The analysis showed that eye-hand concordance was dependent upon sex, x2 = 8.41
NOTE Table
I. Distribution
of subjects
by handedness,
535
eye dominance,
familial
handedness
Males Handedness Eye dominance
and sex
Females
Left
Right
Left
Right
Left
FSf
4
4
8
2
7
1
I
5
FS-
7
6
8
IS
20
3
22
I2
10
I6
I7
27
4
23
I7
Total
II
Right
Left
Right
Left
Right
Left
Right
d.f. = 3. P < 0.05. Further investigation led to the conclusions that handedness and eye dominance were unrelated in males, x2 < 1, but that although left-eyedness was more frequent in both left- and right-handed females, it was disproportionately represented in the left-handed group, x2 = 5.99, f/./I = I, P < 0.02. The result in males contradicts the findings of CUR and GUR [IO, 161 but agrees (though only for left-handers) with CROVITZ [ 171. That females of both handedness groups were left-eyed is also contrary to previous reports [IO, 16, 171. although the rather inconsistent preferences of right-handed females finds some support [IS]. Obviously, sex does affect eye-hand concordance and failure to consider this variable mav have accounted for some of the previous equivocal findings [I I-151. However, our own results on sex differences do not entirely agree with other reports and it seemed useful to examine whether familial handedness was a confounding factor. Analysis of the Z (familial handedness) x 8 (sex-hand-eye combinations) matrix confirmed that the distribution of subjects over columns was influenced by familial handedness, x2 = 14.05, d../. = 7, P < 0.05. Eye-dominance was independent of familial handedness in left-handed males and in left-handed females, P > 0.05 for both by the Fisher Exact test. In right-handed males left-eyedness was more common amongst familial sinistrals whilst right-eyedness was more common amongst familial dextrals, P = 0.04 by the Fisher test. For right-handed females the presence of familial sinistrality reversed the trend towards left-eyedness observed in all other female groups and the comparison with female right-handed familial dextrals was significant, P = 0.04 by the Fisher test. The result in right-handed males seems explicable in terms of the effects on eye-dominance of an inherited tendency towards amibilaterality. The reverse effect of familial sinistrality in right-handed females is thus rather puzzling, as is the absence of any effect in left-handers. It should be noted, however, that not many familial sinistrals were obtained for the present study. Only HICGENBO-I-TAM[I 31 included familial handedness in a study of hand-eye dominance and he found that a battery of eight perceptual preference measures did not discriminate between left-handedness with and without familial sinistrality. Higgenbottam did not include sex or the familial handedness of right-handers in his experiment. Finally, by combining eyedness groups and analysing the resultant 2 (familial handedness) x: 4 (sex-hand combinations) matrix, no evidence was found for sex or handedness differences in the incidence of familial sinistrality, x * = 4 46, d./. = 3, P > 0.05. It may be that more sensitive measures of handedness and familial handedness are required to make adequate tests of those theories and speculations which predict some interdependence between these variables [e.g. 19-281. It is perhaps worth noting that according to the views of SATZ [26, 271, about + of our left-handers (those without familial sinistrality) were non-genetic left-handers who handedness was determined by birth trauma. It seems unlikely that birth trauma accounts for such a large proportion of left-handedness in a normal population of somewhat higher than average intelligence. The present study has shown that sex, handedness and familial handedness intluence ocular sightingdominance. Failure to consider all these variables may have contributed to the equivocality of previous findings. Apart from this, differences in testing procedures are known to atTect results on eye-dominance [l4, IS. 311 and on handedness [29]. Age also alters eye-hand concordance [32] and the strength of subjects’ hand preference may be a further confounding variable. The nature and causes of sighting-dominance itself are as yet unclear and there are suggestions and findings that it is unrelated to cerebral hemispheric processes [33-371 although contrary evidence exists [5-91. However, the present study has illustrated that sightingdominanceis affected by those variables also known to influence functional hemispheric asymmetry, so that a meaningful elucidation of eye-dominance phenomena would seem to require that such variables are taken into account.
REFERENCES I. MCGLONE. J. and DAVIDSON, W. The relationship between cerebral speech laterality and spatial ability with special reference to sex and hand preference. Neuropsc_vhologiu 11, 105-l 13, 1973. 2. MCKEEVER, W. F. and VANDEVENTER, A. D. Visual and auditory language processing asymmetries: Influence of handedness, familial sinistrality, and sex. C’orfelc 12, 225-241, 1977. -
536
NOTE
3. LAKE, D. H. and BRYDES, M. P. Handedness and sex differences in hemispheric asymmetry. Brain & Language 3, 266-282, 1976. 4. H~CAES, H. and S.G_GUET,J. Cerebral dominance in left-handed subjects. Corre.r 7, 1938, 1971, 5. ZASG~ILL, 0. L. Dyslexia in relation to cerebral dominance. In Reading Discrbiliry, J. Xioh~y (Editor). Johns Hopkins Press, Baltimore, 1962. 6. KERSHSER, J. Children’s acquisition of visuospatial dimensionality: A conservation study. Dere/. Psychol. 5, 454-462, 1971. 7. KERSHNER, J. Lateral preference and the ability to conserve multiple space relations by mentally retarded children. Percept. .\for. Skills 35, 151-152, 1972. laterality and dual hemisphere specialization. Corre.r 10, 193-302, 1974. 8. KERSHSER, J. Ocular-manual hemispheric asymmetry in visual perception: EfTects of 9. KERSHSER, J. and JENG, A. Dual functional ocular dominance and postexposural processes. h’ewopsychologio 10, 437115, 1972. sex and eyedness as moderating variables in the relation 10. GUR, R. C. and GUR. R. E. Handedness, between hypnotic susceptibility and functional brain asymmetry. J. abnortn. Psychol. 83. 635-643, 1974. demonstrated by unconscious sighting. J, exp, Psychol. 12, 113-126, II. MILES, W. R. Ocular dominance 1929. in human adults. J. gene/. Psychol. 3, 412-420, 1930. 12. MILES. W. R. Ocular dominance between sets of lateral and perceptual preference measures. Cor/e.r 9, 13. HIGGEEBOTTAC~,J. A. Relationships 403-410,1973. 14. COREN, S. and KAPLAN, C. P. Patterns of ocular dominance. ilnl. J. Oprom. 50, 283-292, 1973. a test of two hypotheses. Br. J. fsychol. 62, 15. GRON~ALL, D. M. A. and SAMPSON, H. Ocular dominance: 175-185, 1971. sighting-dominance and 16. CUR, R. E. and GUR, R. C. Sex differences in the relations among handedness, eye-acuity. Nerrropsychologia 15, 585-590, 1977. and sex Percept. MO/. Skills 37, 520, 1973. 17. CROVITZ, H. F. Lateralities part of generalized laterality? Percept. Mot. Skills 40, 18. PORAC, C. and COREN, S. Is sighting-dominance 763-769, 1975. C0rre.v 11, 230-238, 19. BRIC;GS, G. G. and NEBES, R. D. Patterns of hand preference in a student population. 1975. and degree of left-handedness. Br. J. 20. MCKEEVER. W. F. and VANDEVESTER, A. D. Familial sinistrality Ps~cl~ol. 68, 469-47 I. 1977. in families. Ann. Hltnlnn. Gene,. 37, 93-105, 1973. 21. ANNETT, M. Handedness and laterality. J. camp. 22. WEINSTEIN, S. and SERSEN, E. A. Tactual sensitivity as a function of handedness physiol. Psychol. 54, 665-669, I96 I in families: A preliminary study using dichotic listening. Brain & 23. BRYDEN, M. P. Speech lateralisation Language 2. 201-21 I, 1975. and birth order revisited. Nerrropsychologia 15, 24. BAI(AN, P.. DIBB, G. and REED, P. Left-handedness 837-839, 1977. and birth stress. Nertropsychologia II, 363-366, 1973. 25. BAKAN, P., DIBB, G. and REED, P. Handedness left-handedness: an explanatory model. C0rfe.v 8, 121-135, 1972. 26. SATZ, P. Pathological and early brain insult: an explanation. Neuropsychologiu 11, 115-l 17, 1973. 27. SATZ, P. Left-handedness Generics 72, 117-128, 1972. 28. LEVY, J. and NAGYLAKI, T. A. model for the genetics of handedness EdinburghInventory. Newopsychologia 29. ~LDFIELD, R. C. The assessment and analysis of handedness:The 9,97-l 13,197l. of manual asymmetry. Br. J. Psycho/. 63, 343-358, 1972. 30. ~SNETT, M. The distribution of ocular dominance, handedness and the controlling eye in 31. BERNER, G. and BERNER, D. Relation >inocular vision, Arch. Oprhal50, 603-608, 1953. and cerebral dominance. In Handbook of Clinical Neurology, P. J. VINKES 32. juatRANA, A. Handedness ind G. W. BRUYN (Editors), Vol. 4. North Holland, Amsterdam, 1969. eye. Psych. Bull. 83, 880-897, 1976. 33. =ORAC, C. and COREN,S. The dominant and its relationship to intelligence. Cartel 7, 34. ~ERMAS, A. The problem of assessing cerebral dominance !72-386, I97 I. and dominance. Devel. Med. Child Nerrrol. 14, 747-755, 1972. 35. ~OUWES, B. C. L. Laterality dominance is not related to neurophysio36. ~RINELLA, F. M., BECK, F. W. and ROBINSON, J. W. Unilateral ogical integrity. Child Dev. 42, 2033-2054, 1971. and perceptual asymmetry. Percept. iLlof. Skills 25, 37. ~AYASHI, T. and BRYDEN, M. P. Ocular dominance iO5-612. 1967.
537
NOTE
On P test& et
selon
de
la
une
gaucherie
prif6rence
test6es et
sur
par
manuelle
manuelle, fason
mesure
le
complexe doivenc ses
sexe
et
le
questionnaire.
la
la
gaucherie
femme5
asymetries
selon
de
la
familiale
dans
les
une
mesure
On s’assurait
11 n’y
On suggPre
consider&s aux
71
oculaire.
frkquence
inattendue.
irre
relations
horunes dominance
dans ec
ec
54 de
wait
pas
gaucherie
de
ces
c6rGbrales
la
variables
Etudes
prifGrence du
ult6rieures
nanuelle
caractlre
diffsrences
familiale.
affectaienc que
de
aussi
de
familial sexe
ni
de
La prefdrence
dominance
oculaire
d’une
ainsi
que
d’aurres
non
la
latiralit6
sur
ici
oculaire
fonctionnelles.
Deutschsprachige Zusammenfassung: 54 mannllche und 71 weibliche Personen wurden hinsichtlich
ihrer manuellen und ocularen Lateralisation getestet. Die familiar-eHandigkelt wurde iibereinen Hlndigkeits-Fragebogen erfafit.Es gab keine Unterschiede hinsichtlich Ceschlecht oder Handigkeit beim Vorliegen familiairerLinkshandigkeit. Handigkeit, Geschlecht und famililre Linkshandigkeit hatten in komplexer und unerwarteter Weise EinfluR auf die oculare Dominanz. Es wird die Auffassung vertreten, da0 diese Variablen, ebenso wie andere hier nicht getestete, in zukiinftigenUntersuchungen zur ocularen Dominanz und iiber Beziehungen zu funktionellen cerebralen Asymmetrien einer weiteren Bearbeitung bediirfen.
-
NOTE RELATIONSHIPS
AMONG
SEX AND
HANDEDNESS,
OCULAR PAUL
Department
of Psychology,
HANDEDNESS,
BIRKETT*
University (Received
FAMILIAL
SIGHTING-DOMINANCE
of Liverpool,
Liverpool
L69 3BX, England
I5 March 1979)
Abstract-Fifty-four males and 71 females were tested on a measure of handedness and a measure of ocular sighting-dominance. Familial handedness was also ascertained via the handedness questionnaire. There were no sex or handedness differences in the incidence of familial sinistrality. Handedness, sex and familial handedness affected sighting-dominance in complex and unexpected ways. It is suggested that these variables, as well as others not tested here, will need to be considered in future studies of ocular laterality and its relationship to functional cerebral asymmetries.
SEVERAL variables have been investigated in attempts to determine which organismic factors are most closely associated with hemispheric asymmetries of function. Four such variables are sex, handedness, familial handedness and ocular sighting-dominance. There is at least some evidence for the intluence on cerebral lateralization of each one of these variables, either alone or in combination [e.g. l-9). Despite such evidence, there is little agreement as to the nature of the relationships amongst these variables themselves. Hand-eye dominance has been closely studied and has produced conflicting reports of high (IO-131 and low [I+163 associations. The role of sex in moderating these associations has been investigated and has also proved inconsistent. GUK and GUR [IO, 161 reported that handedness and sighting-dominance were related for males but not for females; both left and right handed females fended to sight with the right eye. However, in their later study [I61 left-handers numbered only 11 out of a total of 200 subjects and only 6 of these were female. CKOVITZ [I71 found that right-handers of both sexes tended to sight with their right eye but that lefthanded males were inconsistent sighters and left-handed females were very slightly biased towards right eye-sighting. These results tvere not discussed by Cur and Gur in their later paper but generally agree with their data, apart from the discrepancies in left-handers. Handedness was not considered in a study by PORAC and COREN [I81 who concluded that, whilst males were more likely than females to display ipsilateral hand-eye dominance, there were no sex-differences in the proportions of left and right eye-sighters. The main aim of the present study was to determine whether any of the above findings were replicable with diRerent handedness and eye dominance tests and using sufficient left-handers of both sexes. However, in view of the contradictory results for left-handers, and since familial handedness is known to influence cerebral asymmetries [Z-4], it was decided to include familial handedness as a variable in order to increase the precision of our results. Whilst it was not expected that the inclusion of this variable would account for all the unexplained variance in previous reports, it did seem likely that some erects would be observed. If eye dominance is one facet of a “generalized laterality”, one might expect familial left-handedness to increase eye-hand concordance in left-handers but to decrease it in right-handers. Of secondary interest in the present study were the relationships among sex, handedness and familial handedness. Of two studies of sex-differences in familial sinistrality one reported a higher incidence for females [I91 and one found no sex-difference [20]. In view of evidence that gender may play a moderating role in the inheritance of handedness [II-231 this question remains of general interest.
*The experimental work reported here was carried out as part of the author’s Ph.D. research Institute of Technology. Thanks are extended to my thesis supervisors, Dr. R. H. RANYARD and GATEHOUSE. -
533
at Bolton CHRISTISE
534
NOTE
The work of B~K-\u and his colleagues on birth stress and left-handedness (2-I. 251 argues for a higher incidence of familial sinistrality in left-handers, although the model proposed by SATZ [26. 271 suggests that this will be true only for those left-handers whose handedness is inherited and not determined by birthtrauma. Genetic theories of handedness naturally predict more familial sinistrality in left-handers [e.g. 21, 281. Although intensive family studies will provide the most reliable data, we examined our results for any signs of a relationship. Two previous studies with normal subjects found positive (191 and negative [20] evidence for the influence of familial sinistrality on handedness, whilst H~CAEN and SAUGUET (41 reported that it related to weaker left-handedness in a brain-damaged sample.
METHOD The sample consisted of I25 normal volunteers drawn from schools, colleges and the general public in the Bolton area of Lancashire. There were 54 males and 7 I females aged between I6 and 42 years (x = 22.5). Subjects were paid an hourly fee for participation. Some prior selection of subjects on the basis of sex and handedness was necessary in order to obtain roughly equivalent numbers in each sex handedness group. Hence, sex-differences in the incidence of left- and right-handedness were not examined here. Materials and procedure (1) Handedness questionnaire. OLDFIELD’S [29] Edinburgh Handedness Inventory was administered to all subjects individually. This instrument has IO items which were shown to be reliably intercorrelated in Oldfield’s original standardization on II00 subjects. The score ranges from - 100 (completely left-handed) to f 100 (completely right-handed). (2) Eye-dominance resf. MILES’S [I I] A-B-C Vision Test for ocular sighting-dominance was administeredto all subjects individually. For this test the subject covers his or her face with the wide end of a truncated cone held with both hands and peers at targets (small cards containing various shapes) about IO ft away. The subjective experience is that alignment of the cone is effected by placing it midway between the two eyes. This cannot be so however; the target may only be seen when the aperture at the narrow end of the cone is aligned with one eye or the other. The eye selected most often over a series of IO trials is the dominant eye for sighting. The cone itself is replaced by an identical one from time to time to prevent a subject’s response being influenced by maintainance of posture. The two tests described were given in counterbalanced order over subjects.
RESULTS
AND
DISCUSSION
Handedness classification A subject was designated left-handed if his or her score fell below the zero point on the inventory and as right-handed if he or she scored above zero. Obviously, there will be some ambilaterals in each groups as a result of such a classification. Nevertheless, the mean handedness scores were -65.6 for left-handers (n = 52) and f64.5 for right-handers (n = 73). These scores were sufficiently disparate to consider the two groups as distinct, particularly in view of the general tendency for left-handers to display considerable ambilaterality of hand usage [30]. Familial handedness was ascertained by asking subjects to indicate on the inventory whether any of their relatives showed any signs of left-handedness. The replies were followed up by questioning to determine the reliability and exact nature of any familial sinistrality. A subject was designated as a familial sinistral if he or she professed to have at least one first-degree relative or two second-degree relatives with tendencies towards left-handedness. Thirty-two of the I25 subjects were so-designated. Eye dominance classification Since no subject proved markedly inconsistent on the A-B-C vision test, it was possible to classify individuals as left or right eye-dominant on the basis of the eye most frequently used for sighting. Seventy-seven subjects were left-eyed and 48 were right-eyed. Table I gives the distribution of subjects classified by sex, familial handedness, handedness and eyedominance. FSi and FS- refer respectively to presence and absence of familial sinistrality. To test the eye-hand dominance relationship alone, results were collapsed over sex and familial handedness. Right-handers had approximately equal numbers sighting with the left [39] and right [34] eye, whilst left-handers displayed a preference for left [38] as opposed to right [I41 eye-sighting, x2 = 4.16, d./. = I, P c 0.05. This is counter to the usual observation of less consistent sighting-dominance in left-handers [e.g. 15, 17). The part played by sex in moderating concordance of eye-hand usage was examined by combining the familial handedness groups as shown in Table I and analysing the 2 (sex) X 4 (eye-hand combinations) matrix for homogeneity. The analysis showed that eye-hand concordance was dependent upon sex, x2 = 8.41
NOTE Table
I. Distribution
of subjects
by handedness,
535
eye dominance,
familial
handedness
Males Handedness Eye dominance
and sex
Females
Left
Right
Left
Right
Left
FSf
4
4
8
2
7
1
I
5
FS-
7
6
8
IS
20
3
22
I2
10
I6
I7
27
4
23
I7
Total
II
Right
Left
Right
Left
Right
Left
Right
d.f. = 3. P < 0.05. Further investigation led to the conclusions that handedness and eye dominance were unrelated in males, x2 < 1, but that although left-eyedness was more frequent in both left- and right-handed females, it was disproportionately represented in the left-handed group, x2 = 5.99, f/./I = I, P < 0.02. The result in males contradicts the findings of CUR and GUR [IO, 161 but agrees (though only for left-handers) with CROVITZ [ 171. That females of both handedness groups were left-eyed is also contrary to previous reports [IO, 16, 171. although the rather inconsistent preferences of right-handed females finds some support [IS]. Obviously, sex does affect eye-hand concordance and failure to consider this variable mav have accounted for some of the previous equivocal findings [I I-151. However, our own results on sex differences do not entirely agree with other reports and it seemed useful to examine whether familial handedness was a confounding factor. Analysis of the Z (familial handedness) x 8 (sex-hand-eye combinations) matrix confirmed that the distribution of subjects over columns was influenced by familial handedness, x2 = 14.05, d../. = 7, P < 0.05. Eye-dominance was independent of familial handedness in left-handed males and in left-handed females, P > 0.05 for both by the Fisher Exact test. In right-handed males left-eyedness was more common amongst familial sinistrals whilst right-eyedness was more common amongst familial dextrals, P = 0.04 by the Fisher test. For right-handed females the presence of familial sinistrality reversed the trend towards left-eyedness observed in all other female groups and the comparison with female right-handed familial dextrals was significant, P = 0.04 by the Fisher test. The result in right-handed males seems explicable in terms of the effects on eye-dominance of an inherited tendency towards amibilaterality. The reverse effect of familial sinistrality in right-handed females is thus rather puzzling, as is the absence of any effect in left-handers. It should be noted, however, that not many familial sinistrals were obtained for the present study. Only HICGENBO-I-TAM[I 31 included familial handedness in a study of hand-eye dominance and he found that a battery of eight perceptual preference measures did not discriminate between left-handedness with and without familial sinistrality. Higgenbottam did not include sex or the familial handedness of right-handers in his experiment. Finally, by combining eyedness groups and analysing the resultant 2 (familial handedness) x: 4 (sex-hand combinations) matrix, no evidence was found for sex or handedness differences in the incidence of familial sinistrality, x * = 4 46, d./. = 3, P > 0.05. It may be that more sensitive measures of handedness and familial handedness are required to make adequate tests of those theories and speculations which predict some interdependence between these variables [e.g. 19-281. It is perhaps worth noting that according to the views of SATZ [26, 271, about + of our left-handers (those without familial sinistrality) were non-genetic left-handers who handedness was determined by birth trauma. It seems unlikely that birth trauma accounts for such a large proportion of left-handedness in a normal population of somewhat higher than average intelligence. The present study has shown that sex, handedness and familial handedness intluence ocular sightingdominance. Failure to consider all these variables may have contributed to the equivocality of previous findings. Apart from this, differences in testing procedures are known to atTect results on eye-dominance [l4, IS. 311 and on handedness [29]. Age also alters eye-hand concordance [32] and the strength of subjects’ hand preference may be a further confounding variable. The nature and causes of sighting-dominance itself are as yet unclear and there are suggestions and findings that it is unrelated to cerebral hemispheric processes [33-371 although contrary evidence exists [5-91. However, the present study has illustrated that sightingdominanceis affected by those variables also known to influence functional hemispheric asymmetry, so that a meaningful elucidation of eye-dominance phenomena would seem to require that such variables are taken into account.
REFERENCES I. MCGLONE. J. and DAVIDSON, W. The relationship between cerebral speech laterality and spatial ability with special reference to sex and hand preference. Neuropsc_vhologiu 11, 105-l 13, 1973. 2. MCKEEVER, W. F. and VANDEVENTER, A. D. Visual and auditory language processing asymmetries: Influence of handedness, familial sinistrality, and sex. C’orfelc 12, 225-241, 1977. -
536
NOTE
3. LAKE, D. H. and BRYDES, M. P. Handedness and sex differences in hemispheric asymmetry. Brain & Language 3, 266-282, 1976. 4. H~CAES, H. and S.G_GUET,J. Cerebral dominance in left-handed subjects. Corre.r 7, 1938, 1971, 5. ZASG~ILL, 0. L. Dyslexia in relation to cerebral dominance. In Reading Discrbiliry, J. Xioh~y (Editor). Johns Hopkins Press, Baltimore, 1962. 6. KERSHSER, J. Children’s acquisition of visuospatial dimensionality: A conservation study. Dere/. Psychol. 5, 454-462, 1971. 7. KERSHNER, J. Lateral preference and the ability to conserve multiple space relations by mentally retarded children. Percept. .\for. Skills 35, 151-152, 1972. laterality and dual hemisphere specialization. Corre.r 10, 193-302, 1974. 8. KERSHSER, J. Ocular-manual hemispheric asymmetry in visual perception: EfTects of 9. KERSHSER, J. and JENG, A. Dual functional ocular dominance and postexposural processes. h’ewopsychologio 10, 437115, 1972. sex and eyedness as moderating variables in the relation 10. GUR, R. C. and GUR. R. E. Handedness, between hypnotic susceptibility and functional brain asymmetry. J. abnortn. Psychol. 83. 635-643, 1974. demonstrated by unconscious sighting. J, exp, Psychol. 12, 113-126, II. MILES, W. R. Ocular dominance 1929. in human adults. J. gene/. Psychol. 3, 412-420, 1930. 12. MILES. W. R. Ocular dominance between sets of lateral and perceptual preference measures. Cor/e.r 9, 13. HIGGEEBOTTAC~,J. A. Relationships 403-410,1973. 14. COREN, S. and KAPLAN, C. P. Patterns of ocular dominance. ilnl. J. Oprom. 50, 283-292, 1973. a test of two hypotheses. Br. J. fsychol. 62, 15. GRON~ALL, D. M. A. and SAMPSON, H. Ocular dominance: 175-185, 1971. sighting-dominance and 16. CUR, R. E. and GUR, R. C. Sex differences in the relations among handedness, eye-acuity. Nerrropsychologia 15, 585-590, 1977. and sex Percept. MO/. Skills 37, 520, 1973. 17. CROVITZ, H. F. Lateralities part of generalized laterality? Percept. Mot. Skills 40, 18. PORAC, C. and COREN, S. Is sighting-dominance 763-769, 1975. C0rre.v 11, 230-238, 19. BRIC;GS, G. G. and NEBES, R. D. Patterns of hand preference in a student population. 1975. and degree of left-handedness. Br. J. 20. MCKEEVER. W. F. and VANDEVESTER, A. D. Familial sinistrality Ps~cl~ol. 68, 469-47 I. 1977. in families. Ann. Hltnlnn. Gene,. 37, 93-105, 1973. 21. ANNETT, M. Handedness and laterality. J. camp. 22. WEINSTEIN, S. and SERSEN, E. A. Tactual sensitivity as a function of handedness physiol. Psychol. 54, 665-669, I96 I in families: A preliminary study using dichotic listening. Brain & 23. BRYDEN, M. P. Speech lateralisation Language 2. 201-21 I, 1975. and birth order revisited. Nerrropsychologia 15, 24. BAI(AN, P.. DIBB, G. and REED, P. Left-handedness 837-839, 1977. and birth stress. Nertropsychologia II, 363-366, 1973. 25. BAKAN, P., DIBB, G. and REED, P. Handedness left-handedness: an explanatory model. C0rfe.v 8, 121-135, 1972. 26. SATZ, P. Pathological and early brain insult: an explanation. Neuropsychologiu 11, 115-l 17, 1973. 27. SATZ, P. Left-handedness Generics 72, 117-128, 1972. 28. LEVY, J. and NAGYLAKI, T. A. model for the genetics of handedness EdinburghInventory. Newopsychologia 29. ~LDFIELD, R. C. The assessment and analysis of handedness:The 9,97-l 13,197l. of manual asymmetry. Br. J. Psycho/. 63, 343-358, 1972. 30. ~SNETT, M. The distribution of ocular dominance, handedness and the controlling eye in 31. BERNER, G. and BERNER, D. Relation >inocular vision, Arch. Oprhal50, 603-608, 1953. and cerebral dominance. In Handbook of Clinical Neurology, P. J. VINKES 32. juatRANA, A. Handedness ind G. W. BRUYN (Editors), Vol. 4. North Holland, Amsterdam, 1969. eye. Psych. Bull. 83, 880-897, 1976. 33. =ORAC, C. and COREN,S. The dominant and its relationship to intelligence. Cartel 7, 34. ~ERMAS, A. The problem of assessing cerebral dominance !72-386, I97 I. and dominance. Devel. Med. Child Nerrrol. 14, 747-755, 1972. 35. ~OUWES, B. C. L. Laterality dominance is not related to neurophysio36. ~RINELLA, F. M., BECK, F. W. and ROBINSON, J. W. Unilateral ogical integrity. Child Dev. 42, 2033-2054, 1971. and perceptual asymmetry. Percept. iLlof. Skills 25, 37. ~AYASHI, T. and BRYDEN, M. P. Ocular dominance iO5-612. 1967.
537
NOTE
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Deutschsprachige Zusammenfassung: 54 mannllche und 71 weibliche Personen wurden hinsichtlich
ihrer manuellen und ocularen Lateralisation getestet. Die familiar-eHandigkelt wurde iibereinen Hlndigkeits-Fragebogen erfafit.Es gab keine Unterschiede hinsichtlich Ceschlecht oder Handigkeit beim Vorliegen familiairerLinkshandigkeit. Handigkeit, Geschlecht und famililre Linkshandigkeit hatten in komplexer und unerwarteter Weise EinfluR auf die oculare Dominanz. Es wird die Auffassung vertreten, da0 diese Variablen, ebenso wie andere hier nicht getestete, in zukiinftigenUntersuchungen zur ocularen Dominanz und iiber Beziehungen zu funktionellen cerebralen Asymmetrien einer weiteren Bearbeitung bediirfen.
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