Neur,p.xychob~qia,Vol. 28, No. 10, pp 1063 1077, 1990.
0028 3932/90$3.00+0.00 i 1990PergamonPressplc
Prinlcd in Greal Britain.
SEX DIFFERENCES IN COGNITIVE ABILITIES: CULTURAL PERSPECTIVE VIRGINIA A.
A CROSS-
M A N N , * SUMIKO S A S A N U M A , t N A O K O SAKUMA~ a n d SHINOBU M A S A K I ~
*Department of Cognitive Sciences, School of Social Sciences, University of California, Irvine, CA 92651, U.S.A.; and +Tokyo Metropolitan Institute of Gerontology, 35-2 Sakaecho, Itabashi-ku 173, Tokyo, Japan
(Received 23 March 1989: accepted 21 May 1990) Abstract--Studies in Western cultures have indicated significant sex differences in certain cognitive abilites. To determine whether similar differences occur in a non-Western culture, this study administered a cross-linguistic battery of tests to high school students in Japan and America. In both cultures, girls averaged significantly higher scores on a Story Recall test, the Digit-Symbol test and a Word Fluency test whereas boys achieved significantly higher scores on a Mental Rotation test. The analysis of standardized test scores further indicated that the size of the sex difference was cultureindependent in three out of these four cases. These results are discussed in the context of the GESCHWtND and GALABURDA [Cerebral Lateralization. Biological Mechanisms, Associations and Pathology, Bradford Books, Cambridge, Massachusetts] account of the contribution of testosterone to left right asymmetries in early cerebral development.
INTRODUCTION ]N AMERICA and other Western countries, a consistent pattern of gender-related differences highlights the possibility that biological sex might play a direct role in cognitive ability. While there is considerable overlap in the scores that individual men and women achieve on any given test, there are two certain well-replicated instances of domain-specific advantage. Females excel on certain tests of verbal skill, whereas males excel on certain tests of visual spatial skill (for reviews, see GARAI and SCHEINFELD, [1 7 ] ; MACCOBYand JACKLIN [ 3 0 ] and [24]). Among the tests which have given evidence of a female advantage are "verbal fluency" tests [22]. These include the Word Fluency test of the Thurston PMA [44]; for references see JARVlK [24] and MACCOBY and JACKLIN [ 3 0 ] and the Controlled Word Association test of BENTONand HAMSHER[3] also employed by GADDESand CROCKETT[16] and HARSHMANe t al. [19]. Some of the most consistent findings have involved "phonologically-driven" tests which allow subjects a limited amount of time to produce as many words as possible that begin with a particular letter; females tend to produce more words than males. Other language tests have yielded less conclusive results; the WAIS Vocabulary test, for example, has been observed to yield a small female advantage [47], and vocabulary tests, in general, have not always yielded female advantages [48]. Another test which has given indication of a female superiority is the Digit-Symbol test of the WAIS (e.g. [41,47].) As LEZACK [29] has noted, performance on this test requires the integration of many different abilities: memory, motor persistence, sustained attention, response speed and visualmotor co-ordination play important roles in performance on 1063
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this test. However, ESTES [11] has suggested that skills in encoding the symbols verbally is also a contributing factor which may account for the observed female superiority. Various "memory" tests have also been reported to yield female superiority [12, 17]. To some extent, such claims are based on observations about performance on the WISC Verbal Learning and Digit-Symbol subtests, tests where the female advantage in "memory" might just as well be viewed as an advantage for "verbal skills". In other cases, such as a study by WILSON et al. [48], the "memory" advantage involved a test which employed nameable drawings as stimuli, making it unclear that memory was truly "visual" (in light of the role of verbal labels in temporary memory, see e.g. [7]). Indeed, the possibility that an effective "verbal strategy" could have been the basis of the female advantage, is entirely consistent with an Australian observation that females perform less well than males on a memory test where verbal strategies are not applicable (the visual reproduction subtest of the Weschler Memory Scale [23]). Memory, then, appears a less well-defined area of female superiority. Findings about male superiority have concerned "spatial abilities", in which case both spatial visualization and spatial orientation have been discussed (for relevant findings, see e.g. [2, 13, 14, 17, 20, 28, 32, 34, 39, 43] but also see [6] for a critical evaluation). Spatial visualization, the ability to rotate two- and three-dimensional pictorially presented stimuli, enters into abstract reasoning required in solving certain mathematical problems, and into performance on tests which require the mental rotation of pictorially presented objects. Some of the most consistent and replicable findings about spatial visualization have been obtained with materials drawn from SHEPARO and METZLER'S now-classic study of mental rotation [40], males tend to be both faster and more accurate in deciding whether two perspective drawings represent the same block figure [12, 14, 19, 25, 43, 45]. Spatial orientation concerns the ability to remain unconfused by the changing orientation in which a spatial configuration may be presented and enters into tasks requiring geographic sense of direction, such as map reading and maze following (for discussion of the difference between spatial visualization and spatial orientation see MCGEE [3]). Reports of male superiority for spatial orientation have often concerned such maze tests as the Porteus maze test [37] and the maze test from the WISC-R [46] as well as certain map-following tests. Finally, reports of a consistent male advantage for mathematical ability are quite frequent in the American literature, and the advantage is said to begin near puberty (see [2] for a review). All of the research cited above was concerned with individuals who lived in Western cultures. There is a paucity of data regarding sex differences among individuals in nonWestern cultures and what data there are do not always replicate the Western pattern of results. With regard to the female advantage on tests of verbal skill, a study of Japanese individuals whose ages ranged from 50 to 80 has revealed no sex difference on either a semantically controlled or a phonologically-controlled word fluency test [38]. Another study which investigated the word fluency performance of Hawaiian individuals [48] has also failed to find any difference in the performance of women and men, whether they were of Japanese or Caucasian ancestry. A study which investigated the automatized naming performance of American and Asian children revealed a female advantage among Caucasian-American children, but no such advantage in Japan or Korea, or among American-Chinese children [49]. Standardization of the Japanese WAIS yielded a male advantage on all subtests, including the Vocabulary test [27] and that advantage has recently been replicated in a study of 162 elderly subjects [36]. Yet, it is interesting to note that there is at least one indication that non-Western females perform at higher levels on a "verbal" test. SASANUMA et al. [38] observed a female
SEX DIFFERENCESIN COGNITIVEABILITIES
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superiority on a "story recall test" in which subjects retold a short story which had been read aloud by the experimenter. There is also an indication that the male advantage for mental rotation might be present among non-Western individuals. WILSONet al. [48] report that sex differences in mental rotation are equally present among Hawaiians of Japanese and European ancestry. Further indications of a male advantage for visual spatial ability come from SASANUMAet al.'s [38] study of Japanese individuals aged 50 to 80, which revealed a significant male advantage for Judgement of Line Orientation, replicating a previous observation by BENTON et al. [4]. It is difficult to reconcile the literature on sex differences in Japan and other non-Western cultures with research which has been conducted in the West. For one thing, there are profound variations in the ages and educational backgrounds of the subjects. Systematic comparisons with the American and European research are also made difficult by the use of different tests and different test procedures. To facilitate the comparison of sex differences in Western and non-Western cultures, we have compiled a bilingual battery of tests that can be given in either Japanese or English. We have administered this battery to high school juniors attending college-preparatory private schools in Japan and in America so that we may discern whether the "Western" pattern of sex differences will replicate when subjects are drawn from a non-European genetic pool and a non-Western culture. The test battery includes three tests of linguistic skill, two tests of visual spatial skill, a test of arithmetic ability and two tests of visual recognition memory. Two of the language tests, the Word Association test and the Digit-Symbol test, were drawn from the American literature; the third is a story recall prompted by the Japanese findings of SASANUMA et al. [38]. One of the visual spatial tests is a test of mental rotation ability adopted from the Shepard Metzler figures by VANDENBERGand KusE [45], the other is the WISC-R Maze test. The test of arithmetic ability is taken from the WRAT. The two tests of visual recognition memory both assess temporary recognition memory, one employs printed words, the other employs the non-verbal "doodle" drawings of KIMURA [26]. These tests offer a means of determining whether any advantage on the story recall test owes to a general "memory" advantage. METHOD );uhiects
The subjects were high school juniors attending private college prepartory schools in the two countries. The American students attended the Bolles School in Jacksonville, FL, and included 66 males and 51 females; the Japanese students attended the Keio University High School in Tokyo, Japan, and included 85 males and 91 females. The Japanese students happened to be enrolled in classrooms that were segregated by sex, whereas the American students were not. However. boys and girls within each school system were educated with the same textbooks, etc. All of the subjects served as unpaid volunteers with the permission of their principals and teachers. Materials
The materials include two versions an English language version and a Japanese language version of a battery of eight different cognitive tests. Each version was prepared by a native speaker. The tests sampled verbal abilities, visual spatial skills, arithmetic skills and visual recognition memory and included: a Controlled Word Association test. the Digit-Symbol test from the WAIS, a Story-Recall test, VANDENBERGet al.'s Mental Rotation test, the Maze test from the WISC-R, the Arithmetic Level [l subtest from the Wide Range Achievement test (WRAT), a Recognition Memory test for printed nonsense words, and a Recognition Memory test for nonsense designs. A detailed description of each test follows. The ('ontrolled Word Association test
The materials were based on the BENTONand HAMSHER[3] Controlled Word Association test. However, instead of an individually-administered spoken response test, we employed a group-administered pen and pencil test (as was
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the case in the Thurston PMA). Our test required the subjects to write as many words as they could that start with a given letter (English version) or kana character (Japanese version), excluding proper nouns, numbers and words that differ only by a suffix. Five different letters/characters were given and the score for each was the total number of responses given. The five items were broken down into two versions of the test which differed in the amount of time that was available for responding to each letter/character, 1 rain or 3 rain. For the testing of the American subjects, we chose the letters "S", "A" and "F" for the 1 min version, and the letters "W'" and "'R" for the 3 rain version. The letters had been selected on the basis of the frequency of English words beginning with each letters, and we sampled comparable frequency levels in constructing our kana materials to arrive at the set "ka","to", "~se'" for the tirst version and "'shi", "'ko" for the second, An English dictionary was used to compute the approximate frequency of occurrence of the English letters: a Japanese dictionary was then used to compute the comparable frequency of occurrence for each of the kana characters. Five scores were computed by counting the number of words given to each letter/kamL. The analysis of the results was focused on the sum of responses to the three 1 rain tests and the sum of the responses to the two 3 min tests. The Digit-Symbol te.st.fi'om the W A I S
Both Japanese [27] and English language versions are available for this subtest of the WAIS {i.e. [47]t, and standardized test forms and instructions were used in each case. The test presents a fixed random sequence of digits with blank squares beneath, subjects fill in the blanks according to a printed key that pairs each digit with a graphic symbol. After a brief practice, subjects are given 90 sec to complete as many blanks as rapidly as possible: the score is the number of correctly-filled squares. Following the methodology of LACHMANet al. we added a control measure to assess individual differences in writing speed. This additional test required subjects to copy a randomized sequence of the graphic symbols that had been used in the WAIS test; the arrangement of symbols was identical to that m the standard test save that the number of trials was doubled to aviod a ceiling effect. Subjects werc given I rain to copy as many symbols as possible, and the score is the number of symbols completed. The Stor) Recall test
The materials for this test consist of a simple short story. (In the American version the event occurs at Niagra Falls in America, keeping all else constant.): "Once there lived a stuntman in Japan. He was very well known throughout the country as a distinguished tightrope walker. One of his best performances was held at Kegon Falls, in the spring of 1896. He walked on a 100 m long tightrope stretched across Kegon falls in front of 2500 spectators. The rope was thin and stretched between the high river banks. Spectators held their breath imagining that he would fall into the surging waters beneath him if he felt even slightly dizzy or trembled. Once more, in the summer of the same year, he walked blindfolded over the falls wearing sandals. Again, in the fall of the same year, he gave a third performance at the falls carrying a person on his back .'" The story was read aloud by a female native speaker: subjects were told to listen and when the story linished to write it down. Thirty minutes later a second "'surprise" recall test was given in which they were again asked to recall the story. The story involves 43 information units and recall is scored in terms of the number of units reported on the first (F) and second (S) retelling, following a protocol developed by Sasanuma et al. [381. Fhe W I S C - R M a z e test
Given that the Porteus test requires up to I hr to administer, we chose to usc the Maze test items from the WISC-R. Although the most difficult item in the WISC-R is a little tess complex than the most difficult Porteus maze items, LEZAK [29] has found it a satisfactory substitute for the Porteus test. Both Japanese and American versions are available for this test, which consists of a sequence of eight mazes; three practices and live lest items. To aw/id ceiling performance we enforced a time limit of 1 min for the practice and 2 rain for the test items. The score is the total number of test mazes that were correctly completed. Fandenher~! and Kuse's Mental Rotation test
This test, developed by VANDENBER¢;and KLSE [45] comprises 4 practice items and 20 test items, taken from the three-dimensional drawings taken from SH•PARD and M~TZLt~R [4(/]. Each item presents five drawings, the lirst drawing is for inspection, and subjects must decide which two of the remaining four drawings depict the same object as the inspection drawing. Items vary in complexity: the two correct responses can include a copy of the inspection drawing, or a drawing viewed from another perspective (i.e. rotated about the vertical axis), one of the foils represents a different object and one represents a mirror image of the inspection object teither or both foils may also be rotated about the vertical axis). Written instructions accompany the practice items and are also read aloud by the examiner. Following completion of the practice items, subjects are given 10 min to complete as many of the lest items as possible. The scoring system suggested by Vandenberg and Kuse (and validated by their research) gives subjects two points for each item on which there have been two correct responses (('C), one point for a single response which is correct (C), and no points when one response is correct but the other is incorrect (('WI as well as
SEX DIFFERENCESIN COGNITIVEABILITIES
1007
when a single response is wrong (W) or when both responses are wrong (WW). Given that this method might bias our sensitivity to sex differences because it does not adequately compensate for "guessing", we subjected the American data /o an alternative form of scoring which more adequately controls for "guessing". [ 2 ( C C ) + C + I 2(CW) 4 1 W W ) - W]. The correlations between the alternative score and the original score were r(124)=0.90.
Arithmetic Ability Jhis test, adapted from the Level II Arithmetic test of the WRAT, contains a series of 42 problems of increasing complexity. In order to make equivalent demands on the two populations, the problems which involved feet and inches, pounds and ounces were omitted. The resulting tests began with multiplication, division, proceeded to fractions and ended with logarithms and quadratic equations. The only geometry problem was a question about the complement of an angle. Subjects were given 10 rain to complete as many problems as possible and the score is the number of correctly solved problems.
Memory lbr Printed Nonsense Wurds ] h e test assessed recognition memory for printed nonsense words, and used materials drawn from MANN [31]. Each item was a two-syllable (two-mora) phonologically plausible nonsense word in either Japanese or English. All items are shown on a projection screen at the rate of 5 sec per item, they were written vertically in Kana (Japanese version) or horizontally in lower-case letters (English version). An inspection set of 20 items is followed by a recognition set in which the inspection items are intermixed with 20 foils. Subjects must decide whether each of the 40 recognition items is "old" (i.e. seen during inspectionl or "'new" (i.e. not seen during inspection). Two scores are computed to distinguish between immediate vs slightly delayed recognition, they are the number of items correct on the first 20 items and the number on the second 20 items.
Memory Ji~r Nonsense Designs ]'his test parallels the test for nonsense words, except that the items are nonsense "'doodle" designs taken from KIMI;RA [26]. as employed in MANN [31].
Procedure All subjects were tested in large groups, during two 45 min sessions conducted within the school in a familiar environmenl. The students were told that the purpose of the research was to compare American and Japanese students: the emphasis on gender differences was not mentioned. The instructions for each test were read aloud by a female native speaker of the student's language, and teachers and research assistants were present to answer questions and ensure quiet co-operation. Testing followed a fixed sequence, in the first session subjects completed the handedness questionnaire designed by ANNETTE [1], followed by the 1 min version of the Controlled Word Association test, the Mental Rotation test, the 3 rain version of the Word Association test and the Maze test. In the second session, they completed the Immediate Story Recall test, followed by the Nonsense Word recognition test. the Digit-Symbol and Symbol Copying tests, the Nonsense Design Recognition test. the Surprise Story recall test and the Arithmetic test.
RESULTS The performance of the American males and females is summarized in Table l, and it will be seen that the present test battery replicates many of the previous observations about sex differences in Western cultures. Table 2 summarizes the performance of the Japanese subjects, and inspection of that table will reveal an almost identical pattern of sex differences. In making a statistical evaluation of the scores on the various tests it is necessary that we determine not only whether there are sex differences in the population as a whole, but also whether the extent of any difference is comparable across the two countries. Both questions can be addressed with an analysis which pools the scores on each test across gender within each country and converts them to culture-specific Z-scores (Zcs-Scores). This analysis has the advantage of standardizing the scores within each country by establishing a mean of zero and variance unity, so that we may turn to the question of sex differences and their comparability across the two cultures. The Zcs-Scores appear in Table 3, which compares the scores of males and females within the American and Japanese populations, giving the average value for each sex on each test. When these Zcs-Scores were used as the dependent variables in a series of A N O V A ' s with
V. A. MAyy et al.
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Table 1. Sex differences in cognitive abilities: mean scores of American high school juniors N
Male students Mean SD
N
Female students Mean SD
Handedness quotient
74
1.14
2.4
47
1.45
3.1
Word fluency: F (1 min) A S Total
74 74 74 74
13.14 11.15 14.85 39.14
3.8 3.2 3.3
47 47 47 47
13.00 11.63 15.45 40.08
3.4 3.8 4.0
Word fluency: W (3 min) R Total
74 74 74
24.82 25.10 49.90
5.9 6.9
47 47 47
25.60 25.56 51.16
6.3 6.6
Story Recall: I II
66 66
16.7() 15.67
5.5 6.2
51 51
19.55 18.88
5.7 5.5
Digit-Symbol Symbol Copying Mental Rotation Mazes Arithmetic
66 66 74 74 66
78.92 112.41 24.24 4.65 19.71
13.0 24.8 9.7 0.5 5.1
51 51 47 47 51
83.80 116.24 18.38 4.43 20.18
II.I 7.l 7.9 0.6 4.9
Nonsense Word Recognition First half 66 Second half 66
16.12 15.81
2.0 1.8
51 51
t6.29 15.59
1.9 1.8
Nonsense Design Recognition First half 66 Second half 66
14.88 12.72
2.3 2.4
51 51
15.03 13.33
2.5 2.6
gender and culture as between-subjects factors, the results revealed that the male students had a v e r a g e d higher scores on the M e n t a l R o t a t i o n test, F ( 1 , 2 9 5 ) = 4 4 . 5 5 , P < 0 . 0 0 0 and that this difference r e m a i n e d equivalent across the two countries, as indicated by a lack of interaction between gender and country.* T he female students had averaged higher scores than the male students on the Story Recall test, F (1, 2 8 9 ) = 39.78, P < 0 . 0 0 0 , the Digit S y m b o l test, F ( I , 2 6 9 ) = 1 2 . 1 0 , P < 0 . 0 0 0 and the W o r d Fluency test, F ( 1 , 2 9 0 ) = 14.01, P < 0 . 0 0 0 . O n both the Story Recall test and the Digit S y m b o l test, the extent of a d v a n t a g e was relatively c o n s t a n t across the two countries, there was no interaction between sex and country. H o w e v e r , for the W o r d F l u e n c y test there was a significant interaction between gender and country, F ( 1 , 2 9 0 ) = 6 . 2 6 . N e u m a n - K e u l s tests revealed that, a l t h o u g h the females in both countries had a v e r a g e d higher scores than the males, the sex difference was only significant in the case of the J a p a n e s e subjects, q (4, 2 9 0 ) = 5.85, P < 0.001. Th er e were no o t h er main effects n o r interactions in the analysis of the verbal tests. (In the analysis of the story recall test, the i m m e d i a t e and delayed scores were treated as a repeated measure. In the W o r d Fluency test, the time allowed for r e s p o n d i n g was treated as a repeated measure using the average of the three 1 min scores vs the average of the two 3 min scores.) All of the r e m a i n i n g tests the A r i t h m e t i c test, the M a z e test and the S y m b o l C o p y i n g test indicated no significant effect of gender and no interaction bctwecn gender and country. The M e m o r y test indicated no main effect of gender and no interaction bctwccn *A separate analysis of the American data which considered the alternative system mentioned in the M e t h o d s section reveals that the male advantage obtained equally for that systcm F (1,22)= 14.642, P 10 S.D. Mean
Handedness quotient Incidence: male female
66 33 33
0.00 0.38 0.38
0.0
5 2 3
1 t.00 0.02 0.03
0.2
Word fluency: KA {I min) TO SE Total
66 66 66
11.81 9.89 9.70 31.40
3.7 3.7 3.9
5 5 5
13.20 10.40 11.40 35.00
2.2
Word fluency: SHI (3 mini KO Total
66 66
26.11 23.77 49.88
8.6 10.2
5 5
28.20 26.40 54.40
5.8 6.9
Story Recall: 1 II
66 66
26.12 26.71
7.9 7.8
5 5
27.60 29.40
5.0 5.0
Digit-Symbol Symbol Copying
63 62
74.03 122.83
8.6 14.4
5 5
85.00 124.40
3.7 10.2
Mental Rotation Mazes Arithmetic
66 66 61
28.83 4.21 25.64
6.7 0.6 3.8
5 5 5
29.40 4.40 23.40
4.2 0.5 7.3
Nonsense Word Recognition First half 63 Second half 63
18.21 17.26
1.9 2.0
5 5
18.00 17.00
1.2 1.0
Nonsense Design Recognition First half 63 Second half 63
16.73 14.11
2.5 2.9
5 5
16.80 13.40
2.5 3.8
2.3 3.9
i n d i v i d u a l d i f f e r e n c e s in c o g n i t i v e skill. H o w e v e r , it s h o u l d b e k e p t in m i n d t h a t t h e differences between the average male and female scores are relatively small when compared w i t h t h e r a n g e of d i f f e r e n c e s t h a t o c c u r w i t h i n e a c h sex. It s h o u l d a l s o b e n o t e d t h a t we o b s e r v e r e l a t i v e , n o t a b s o l u t e s u p e r i o r i t y . G i v e n t h a t t h e l a r g e s t s i g n i f i c a n t d i f f e r e n c e we o b t a i n is less t h a n o n e s t a n d a r d d e v i a t i o n , a n d m o s t a r e less t h a n a h a l f o f a s t a n d a r d d e v i a t i o n , o u r r e s u l t s d o n o t w a r r a n t d i f f e r e n t e d u c a t i o n a l g o a l s for m e n a n d w o m e n , o r d i f f e r e n t c a r e e r a s p i r a t i o n s . G i v e n t h a t t h e girls a v e r a g e d " s u p e r i o r " s c o r e s o n c e r t a i n p o r t i o n s o f t h e test b a t t e r y a n d t h e b o y s a v e r a g e d s u p e r i o r s c o r e s o n a n o t h e r , we a l s o c a n n o t g o v e r y far t o w a r d s e x p l a i n i n g w h y m a l e h i g h s c h o o l s t u d e n t s a c h i e v e h i g h e r S c h o l a s t i c A c h i e v e m e n t test ( S A T ) s c o r e s , c o m p l e t e m o r e y e a r s o f e d u c a t i o n , etc. B u t t h e s e c o n s i d e r a t i o n s s h o u l d n o t d e t e r us f r o m p u r s u i t o f " b i o l o g i c a l l y - b a s e d " a c c o u n t s of i n d i v i d u a l d i f f e r e n c e s , j u s t as t h e p u r s u i t o f " b i o l o g i c a l - a c c o u n t s " s h o u l d n o t p r e c l u d e t h e p o s s i b i l i t y t h a t s o m e , as yet u n i d e n t i f i e d s o c i o l o g i c a l f a c t o r s a l s o p l a y a n i m p o r t a n t role.
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5. CAMIL,O. A cross-cultural study on gender differences in cognitive abilities. Unpublished BA. Honors thesis. Bryn Mawr College, Bryn Mawr, Pennsylvania, 1985. 6. CAPLAN, P. J., MACPHERSON, G. M. and TOBIN, P. Do sex-related differences in spatial abilities exist? Am. Psychol. 40, 786 799, 1985. 7. CONRAD, R. Acoustic confusions in immediate memory. Br. J. ~fPsyehol. 55, 75 84, 1964. 8. CORKIN, S. Tactually-guided maze-learning in man, effects of unilateral cortical excisions and bilateral hippocampal lesions. Neuropsychologia 3, 339 351, 1965. 9. CCMMINCiS,J. L. Clinical Neuropsychiatry. Grune & Stratton, New York, 1985. 10. DITUNNO, P. and MANN, V. A. Right-hemisphere mediation of mental rotation in normal subjects and brain-damaged subjects. Cortex (in press). 11. ESTES, W. K. Learning theory and intelligence. Am. Psvchol. 29, 740 749. 1974. 12. FAIRWEATHER,O. Sex differences in cognition. Cognition 4, 231 280, 1976. 13. FLANCY, F. and BALLING,D. Developmental changes in hemispheric specialization for the tactile spatial ability. Devlop. Psychol. 15, 364 372, 1979. 14. FREEMAN,F. and ROVENGO,R. Ocular dominance, cognitive strategy and sex differences in spatial ability. Percept. Motor Skills 52, 651 654, 1981. 15. FUKUSAKO, Y., MONOI, H., WATAMORI,Y. and SASANUMA,S. Patterns of performance on Higher Cortical Functions Test in dementia and aphasia. Paper presented at the l lth Meeting of the Japanese Neuropsychological Society, Tokyo, 1987. 16. GADI~S, W. H. and CROCKETT,D. J. The Spreen Benton Aphasia tests, Normative data as a measure of normal language development. Brain Lured. 2, 257 280, 1975. 17. GARAI, S. and SCHEINFELD, K. Sex differences in mental and behavioral traits. Gene. Psyehol..,'~lono~lr. 77, 169 299, 1968. 18. GESCHWIND. N. and GALABURI)A, A. M. Cerebral Lateralization: Biological meehanisms, Associations and Pathaloyy. Bradford Books, Cambridge, Massachusetts, 1987. 19. HARSHMAN,R. A., HAMPSON, E. and BERENBAUM,S. A. Individual differences in cognitive abilities and brain organization: I. Sex and handedness. Can. J. Psyehol. 37, 144 192, 1983. 20. HARTI.AI)GE, S. Sex linked inheritance of spatial ability. Percept. Motor Skills 31,610, 1970. 21. HECAEN, H. Clinical symptomatology in right and left hemisphere lesions. In Interhemispheric Relations aml Cerebral Dominance, V. B. MOtJNTCASTLr: (Editor), pp. 2l 5 243. Johns Hopkins Press, Baltimore, 1962. 22. HOBSON, J. R. Sex differences in primary mental abilities. J. Educ. Psyehal. 41, 126 132, 1947. 23. IVlSON, D. J. The Weschler Memory Scale: Preliminary findings toward an Australian standardization. Australian Psycholo~tist 12, 303 312, 1977. 24. JARVIK,L. E. H u m a n intelligence: sex differences. Acta Genetieae Medical et Gemello~tiae 24, 189 211, 1975. 25. KAIL, R. The locus of sex differences in spatial ability. Percept. & Motor Skills 26, 182 186, 1979. 26. KIMURA. D. Right temporal lobe damage. Archs Neurol. 8, 264 271, 1963. 27. KOI~AMA,H., SHINAGAWA,F. and INDO, T. WAIS: Japanese Edition. Nihon Bunkakagakusha, Tokyo, 1958. 28. KOLm B. and WmSHAW, R. Fundamental o['Human Neuropsycholo~ly. Freeman & Co., New York, 1985. 29. L~ZAK, M. Neuropsyeholo,qieal Assessment. Oxford Press, New York, 1982. 30. MAcctmv, E. E. and JACKLIN, C. N. The Psycholo~ly o[Sex Di[lerenees. Stanford University Press, Stanford, 1974. 31. MANN,V. A. Temporary memory h)r linguistic and nonlinguistic materials in relation to the acquisition of K ana and Kanji. Ann. Bull. RILP 18, 135 151, 1984. 32. MCGLONE, S. and DAVlDSON, D. Relation between cerebral speech laterality and spatial ability with special reference to sex and hand preference. Neuropsycholoqia 11, 105 113, 1973. 33. McGH~, M. G. H u m a n spatial abilities: psychometric studies and environmental, genetic, hormonal and neurological influences. Psyehol. Bull. 86, 889 918, 1979. 34. M('GuINIiSS, P. Sex differences in the organization of perception and cognition. In E~plorinq .S'e\ l)i[[erences, B. LLOYD (Editor). Academic Press, New York, 1976. 35. MILYER, B. Visually-guided maze learning in man: effects of bilateral hippocampal, bilateral frontal and unilateral cerebral lesions. Neuropsycholoclia 3, 317 338, 1965. 36. NAKAZATO,K. and SHIMONAKA,g. Structure ofintelligence a m o n g the Japanese aged. Geropsvcholo~/ieal Res. 7, 39 49, 1981 (in Japanese). 37. PORTEUS, S. D. Porteus Maze Test: 50 Years (?] Application. California Pacific Books, Palo Alto, 1965. 38. SASANUMA, S., ITOH, M., WATAMORI, T. S., EUKUZAWA, K., SAKUMA,N., F1;KI:SAK(}. Y. alld MtlNt~I, 11. Linguistic and nonlinguistic abilities of the Japanese elderly and patients with dementia. 77w .l¢ti,~t Brain. Communication in the Elderly, College Hill Press, California, 1985. 39. SATZ, P. and ZAIDk, H. Sex differences: clues or myths on genetic aspects of speech and language. In (ieneti~ Aspects (~[Speech and Languacle Disorders, C. LL'DLOW (Editor) Academic Press, New York, 1983. 40. SHEPARD,R. N. and METZLER, J. Mental rotation of three-dimensional objects..S'ciente 171, 701 703. 1971. 41. SMITH, A. Consistent sex differences in a specific (decoding) test performance. Educational and t'sycholo~ticul Measurement 27, 1077 1083, 1967.
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42. SIRUIL R. L. and GESCHWIND, N. Localization in Gerstman Syndrome. In Localization in Neuropsycholo~ty, pp. 295 321. Academic Press, New York, 1983. 43. TAI'LEY, R. and BRYDEN, B. An investigation of sex differences in spatial ability: mental rotation of 3-D objects. Can. J. Psych. 31, 122 t30, 1977. 44. THtJRSTON, L. L. and THURSTON, T. G. SRA Primary Mental Abilities Test Ji~r 11 17. Science Research Associates, Chicago, 1947. 45. VANDENBERG,S. G. and KtSE, A. R. Mental rotations, a group test of three-dimensional spatial visualization. Perceptual and Motor Skills 47, 599 604, 1978. 46. WES('HSLER, D. Weschler lntelli~lence ScaleJ~r Children. Psychological Corporation, New York, 1949. 47. WESCHLSER, D. The Measurement and Appraisal q( Adult Intelliqence. (4th edn). Williams and Wilkins, Baltimore, 1958. 48. WILSON, J. R., DE FR[I'S, J. C., MCCLEARN, G. E., VANDENBERG,S. G., JOHNSDN, R. C. and RASHAD, M. N. Cognitive abilities: use of family data as a control to assess sex and age differences in two ethnic groups. Int. J. A~tin~l Hum. Devel. 6, 261 276, 1975. 49. WOLEt:, P. H., HURWITZ, l., IMAMURA, S. and LEE, K. W. Sex differences and ethnic variations in speed of automatized naming. Neuropsychologia 21,283 288, 1983.
0028 3932/90$3.00+0.00 i 1990PergamonPressplc
Prinlcd in Greal Britain.
SEX DIFFERENCES IN COGNITIVE ABILITIES: CULTURAL PERSPECTIVE VIRGINIA A.
A CROSS-
M A N N , * SUMIKO S A S A N U M A , t N A O K O SAKUMA~ a n d SHINOBU M A S A K I ~
*Department of Cognitive Sciences, School of Social Sciences, University of California, Irvine, CA 92651, U.S.A.; and +Tokyo Metropolitan Institute of Gerontology, 35-2 Sakaecho, Itabashi-ku 173, Tokyo, Japan
(Received 23 March 1989: accepted 21 May 1990) Abstract--Studies in Western cultures have indicated significant sex differences in certain cognitive abilites. To determine whether similar differences occur in a non-Western culture, this study administered a cross-linguistic battery of tests to high school students in Japan and America. In both cultures, girls averaged significantly higher scores on a Story Recall test, the Digit-Symbol test and a Word Fluency test whereas boys achieved significantly higher scores on a Mental Rotation test. The analysis of standardized test scores further indicated that the size of the sex difference was cultureindependent in three out of these four cases. These results are discussed in the context of the GESCHWtND and GALABURDA [Cerebral Lateralization. Biological Mechanisms, Associations and Pathology, Bradford Books, Cambridge, Massachusetts] account of the contribution of testosterone to left right asymmetries in early cerebral development.
INTRODUCTION ]N AMERICA and other Western countries, a consistent pattern of gender-related differences highlights the possibility that biological sex might play a direct role in cognitive ability. While there is considerable overlap in the scores that individual men and women achieve on any given test, there are two certain well-replicated instances of domain-specific advantage. Females excel on certain tests of verbal skill, whereas males excel on certain tests of visual spatial skill (for reviews, see GARAI and SCHEINFELD, [1 7 ] ; MACCOBYand JACKLIN [ 3 0 ] and [24]). Among the tests which have given evidence of a female advantage are "verbal fluency" tests [22]. These include the Word Fluency test of the Thurston PMA [44]; for references see JARVlK [24] and MACCOBY and JACKLIN [ 3 0 ] and the Controlled Word Association test of BENTONand HAMSHER[3] also employed by GADDESand CROCKETT[16] and HARSHMANe t al. [19]. Some of the most consistent findings have involved "phonologically-driven" tests which allow subjects a limited amount of time to produce as many words as possible that begin with a particular letter; females tend to produce more words than males. Other language tests have yielded less conclusive results; the WAIS Vocabulary test, for example, has been observed to yield a small female advantage [47], and vocabulary tests, in general, have not always yielded female advantages [48]. Another test which has given indication of a female superiority is the Digit-Symbol test of the WAIS (e.g. [41,47].) As LEZACK [29] has noted, performance on this test requires the integration of many different abilities: memory, motor persistence, sustained attention, response speed and visualmotor co-ordination play important roles in performance on 1063
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V.A. MANN et al,
this test. However, ESTES [11] has suggested that skills in encoding the symbols verbally is also a contributing factor which may account for the observed female superiority. Various "memory" tests have also been reported to yield female superiority [12, 17]. To some extent, such claims are based on observations about performance on the WISC Verbal Learning and Digit-Symbol subtests, tests where the female advantage in "memory" might just as well be viewed as an advantage for "verbal skills". In other cases, such as a study by WILSON et al. [48], the "memory" advantage involved a test which employed nameable drawings as stimuli, making it unclear that memory was truly "visual" (in light of the role of verbal labels in temporary memory, see e.g. [7]). Indeed, the possibility that an effective "verbal strategy" could have been the basis of the female advantage, is entirely consistent with an Australian observation that females perform less well than males on a memory test where verbal strategies are not applicable (the visual reproduction subtest of the Weschler Memory Scale [23]). Memory, then, appears a less well-defined area of female superiority. Findings about male superiority have concerned "spatial abilities", in which case both spatial visualization and spatial orientation have been discussed (for relevant findings, see e.g. [2, 13, 14, 17, 20, 28, 32, 34, 39, 43] but also see [6] for a critical evaluation). Spatial visualization, the ability to rotate two- and three-dimensional pictorially presented stimuli, enters into abstract reasoning required in solving certain mathematical problems, and into performance on tests which require the mental rotation of pictorially presented objects. Some of the most consistent and replicable findings about spatial visualization have been obtained with materials drawn from SHEPARO and METZLER'S now-classic study of mental rotation [40], males tend to be both faster and more accurate in deciding whether two perspective drawings represent the same block figure [12, 14, 19, 25, 43, 45]. Spatial orientation concerns the ability to remain unconfused by the changing orientation in which a spatial configuration may be presented and enters into tasks requiring geographic sense of direction, such as map reading and maze following (for discussion of the difference between spatial visualization and spatial orientation see MCGEE [3]). Reports of male superiority for spatial orientation have often concerned such maze tests as the Porteus maze test [37] and the maze test from the WISC-R [46] as well as certain map-following tests. Finally, reports of a consistent male advantage for mathematical ability are quite frequent in the American literature, and the advantage is said to begin near puberty (see [2] for a review). All of the research cited above was concerned with individuals who lived in Western cultures. There is a paucity of data regarding sex differences among individuals in nonWestern cultures and what data there are do not always replicate the Western pattern of results. With regard to the female advantage on tests of verbal skill, a study of Japanese individuals whose ages ranged from 50 to 80 has revealed no sex difference on either a semantically controlled or a phonologically-controlled word fluency test [38]. Another study which investigated the word fluency performance of Hawaiian individuals [48] has also failed to find any difference in the performance of women and men, whether they were of Japanese or Caucasian ancestry. A study which investigated the automatized naming performance of American and Asian children revealed a female advantage among Caucasian-American children, but no such advantage in Japan or Korea, or among American-Chinese children [49]. Standardization of the Japanese WAIS yielded a male advantage on all subtests, including the Vocabulary test [27] and that advantage has recently been replicated in a study of 162 elderly subjects [36]. Yet, it is interesting to note that there is at least one indication that non-Western females perform at higher levels on a "verbal" test. SASANUMA et al. [38] observed a female
SEX DIFFERENCESIN COGNITIVEABILITIES
1065
superiority on a "story recall test" in which subjects retold a short story which had been read aloud by the experimenter. There is also an indication that the male advantage for mental rotation might be present among non-Western individuals. WILSONet al. [48] report that sex differences in mental rotation are equally present among Hawaiians of Japanese and European ancestry. Further indications of a male advantage for visual spatial ability come from SASANUMAet al.'s [38] study of Japanese individuals aged 50 to 80, which revealed a significant male advantage for Judgement of Line Orientation, replicating a previous observation by BENTON et al. [4]. It is difficult to reconcile the literature on sex differences in Japan and other non-Western cultures with research which has been conducted in the West. For one thing, there are profound variations in the ages and educational backgrounds of the subjects. Systematic comparisons with the American and European research are also made difficult by the use of different tests and different test procedures. To facilitate the comparison of sex differences in Western and non-Western cultures, we have compiled a bilingual battery of tests that can be given in either Japanese or English. We have administered this battery to high school juniors attending college-preparatory private schools in Japan and in America so that we may discern whether the "Western" pattern of sex differences will replicate when subjects are drawn from a non-European genetic pool and a non-Western culture. The test battery includes three tests of linguistic skill, two tests of visual spatial skill, a test of arithmetic ability and two tests of visual recognition memory. Two of the language tests, the Word Association test and the Digit-Symbol test, were drawn from the American literature; the third is a story recall prompted by the Japanese findings of SASANUMA et al. [38]. One of the visual spatial tests is a test of mental rotation ability adopted from the Shepard Metzler figures by VANDENBERGand KusE [45], the other is the WISC-R Maze test. The test of arithmetic ability is taken from the WRAT. The two tests of visual recognition memory both assess temporary recognition memory, one employs printed words, the other employs the non-verbal "doodle" drawings of KIMURA [26]. These tests offer a means of determining whether any advantage on the story recall test owes to a general "memory" advantage. METHOD );uhiects
The subjects were high school juniors attending private college prepartory schools in the two countries. The American students attended the Bolles School in Jacksonville, FL, and included 66 males and 51 females; the Japanese students attended the Keio University High School in Tokyo, Japan, and included 85 males and 91 females. The Japanese students happened to be enrolled in classrooms that were segregated by sex, whereas the American students were not. However. boys and girls within each school system were educated with the same textbooks, etc. All of the subjects served as unpaid volunteers with the permission of their principals and teachers. Materials
The materials include two versions an English language version and a Japanese language version of a battery of eight different cognitive tests. Each version was prepared by a native speaker. The tests sampled verbal abilities, visual spatial skills, arithmetic skills and visual recognition memory and included: a Controlled Word Association test. the Digit-Symbol test from the WAIS, a Story-Recall test, VANDENBERGet al.'s Mental Rotation test, the Maze test from the WISC-R, the Arithmetic Level [l subtest from the Wide Range Achievement test (WRAT), a Recognition Memory test for printed nonsense words, and a Recognition Memory test for nonsense designs. A detailed description of each test follows. The ('ontrolled Word Association test
The materials were based on the BENTONand HAMSHER[3] Controlled Word Association test. However, instead of an individually-administered spoken response test, we employed a group-administered pen and pencil test (as was
1066
V.A. MANY et al.
the case in the Thurston PMA). Our test required the subjects to write as many words as they could that start with a given letter (English version) or kana character (Japanese version), excluding proper nouns, numbers and words that differ only by a suffix. Five different letters/characters were given and the score for each was the total number of responses given. The five items were broken down into two versions of the test which differed in the amount of time that was available for responding to each letter/character, 1 rain or 3 rain. For the testing of the American subjects, we chose the letters "S", "A" and "F" for the 1 min version, and the letters "W'" and "'R" for the 3 rain version. The letters had been selected on the basis of the frequency of English words beginning with each letters, and we sampled comparable frequency levels in constructing our kana materials to arrive at the set "ka","to", "~se'" for the tirst version and "'shi", "'ko" for the second, An English dictionary was used to compute the approximate frequency of occurrence of the English letters: a Japanese dictionary was then used to compute the comparable frequency of occurrence for each of the kana characters. Five scores were computed by counting the number of words given to each letter/kamL. The analysis of the results was focused on the sum of responses to the three 1 rain tests and the sum of the responses to the two 3 min tests. The Digit-Symbol te.st.fi'om the W A I S
Both Japanese [27] and English language versions are available for this subtest of the WAIS {i.e. [47]t, and standardized test forms and instructions were used in each case. The test presents a fixed random sequence of digits with blank squares beneath, subjects fill in the blanks according to a printed key that pairs each digit with a graphic symbol. After a brief practice, subjects are given 90 sec to complete as many blanks as rapidly as possible: the score is the number of correctly-filled squares. Following the methodology of LACHMANet al. we added a control measure to assess individual differences in writing speed. This additional test required subjects to copy a randomized sequence of the graphic symbols that had been used in the WAIS test; the arrangement of symbols was identical to that m the standard test save that the number of trials was doubled to aviod a ceiling effect. Subjects werc given I rain to copy as many symbols as possible, and the score is the number of symbols completed. The Stor) Recall test
The materials for this test consist of a simple short story. (In the American version the event occurs at Niagra Falls in America, keeping all else constant.): "Once there lived a stuntman in Japan. He was very well known throughout the country as a distinguished tightrope walker. One of his best performances was held at Kegon Falls, in the spring of 1896. He walked on a 100 m long tightrope stretched across Kegon falls in front of 2500 spectators. The rope was thin and stretched between the high river banks. Spectators held their breath imagining that he would fall into the surging waters beneath him if he felt even slightly dizzy or trembled. Once more, in the summer of the same year, he walked blindfolded over the falls wearing sandals. Again, in the fall of the same year, he gave a third performance at the falls carrying a person on his back .'" The story was read aloud by a female native speaker: subjects were told to listen and when the story linished to write it down. Thirty minutes later a second "'surprise" recall test was given in which they were again asked to recall the story. The story involves 43 information units and recall is scored in terms of the number of units reported on the first (F) and second (S) retelling, following a protocol developed by Sasanuma et al. [381. Fhe W I S C - R M a z e test
Given that the Porteus test requires up to I hr to administer, we chose to usc the Maze test items from the WISC-R. Although the most difficult item in the WISC-R is a little tess complex than the most difficult Porteus maze items, LEZAK [29] has found it a satisfactory substitute for the Porteus test. Both Japanese and American versions are available for this test, which consists of a sequence of eight mazes; three practices and live lest items. To aw/id ceiling performance we enforced a time limit of 1 min for the practice and 2 rain for the test items. The score is the total number of test mazes that were correctly completed. Fandenher~! and Kuse's Mental Rotation test
This test, developed by VANDENBER¢;and KLSE [45] comprises 4 practice items and 20 test items, taken from the three-dimensional drawings taken from SH•PARD and M~TZLt~R [4(/]. Each item presents five drawings, the lirst drawing is for inspection, and subjects must decide which two of the remaining four drawings depict the same object as the inspection drawing. Items vary in complexity: the two correct responses can include a copy of the inspection drawing, or a drawing viewed from another perspective (i.e. rotated about the vertical axis), one of the foils represents a different object and one represents a mirror image of the inspection object teither or both foils may also be rotated about the vertical axis). Written instructions accompany the practice items and are also read aloud by the examiner. Following completion of the practice items, subjects are given 10 min to complete as many of the lest items as possible. The scoring system suggested by Vandenberg and Kuse (and validated by their research) gives subjects two points for each item on which there have been two correct responses (('C), one point for a single response which is correct (C), and no points when one response is correct but the other is incorrect (('WI as well as
SEX DIFFERENCESIN COGNITIVEABILITIES
1007
when a single response is wrong (W) or when both responses are wrong (WW). Given that this method might bias our sensitivity to sex differences because it does not adequately compensate for "guessing", we subjected the American data /o an alternative form of scoring which more adequately controls for "guessing". [ 2 ( C C ) + C + I 2(CW) 4 1 W W ) - W]. The correlations between the alternative score and the original score were r(124)=0.90.
Arithmetic Ability Jhis test, adapted from the Level II Arithmetic test of the WRAT, contains a series of 42 problems of increasing complexity. In order to make equivalent demands on the two populations, the problems which involved feet and inches, pounds and ounces were omitted. The resulting tests began with multiplication, division, proceeded to fractions and ended with logarithms and quadratic equations. The only geometry problem was a question about the complement of an angle. Subjects were given 10 rain to complete as many problems as possible and the score is the number of correctly solved problems.
Memory lbr Printed Nonsense Wurds ] h e test assessed recognition memory for printed nonsense words, and used materials drawn from MANN [31]. Each item was a two-syllable (two-mora) phonologically plausible nonsense word in either Japanese or English. All items are shown on a projection screen at the rate of 5 sec per item, they were written vertically in Kana (Japanese version) or horizontally in lower-case letters (English version). An inspection set of 20 items is followed by a recognition set in which the inspection items are intermixed with 20 foils. Subjects must decide whether each of the 40 recognition items is "old" (i.e. seen during inspectionl or "'new" (i.e. not seen during inspection). Two scores are computed to distinguish between immediate vs slightly delayed recognition, they are the number of items correct on the first 20 items and the number on the second 20 items.
Memory Ji~r Nonsense Designs ]'his test parallels the test for nonsense words, except that the items are nonsense "'doodle" designs taken from KIMI;RA [26]. as employed in MANN [31].
Procedure All subjects were tested in large groups, during two 45 min sessions conducted within the school in a familiar environmenl. The students were told that the purpose of the research was to compare American and Japanese students: the emphasis on gender differences was not mentioned. The instructions for each test were read aloud by a female native speaker of the student's language, and teachers and research assistants were present to answer questions and ensure quiet co-operation. Testing followed a fixed sequence, in the first session subjects completed the handedness questionnaire designed by ANNETTE [1], followed by the 1 min version of the Controlled Word Association test, the Mental Rotation test, the 3 rain version of the Word Association test and the Maze test. In the second session, they completed the Immediate Story Recall test, followed by the Nonsense Word recognition test. the Digit-Symbol and Symbol Copying tests, the Nonsense Design Recognition test. the Surprise Story recall test and the Arithmetic test.
RESULTS The performance of the American males and females is summarized in Table l, and it will be seen that the present test battery replicates many of the previous observations about sex differences in Western cultures. Table 2 summarizes the performance of the Japanese subjects, and inspection of that table will reveal an almost identical pattern of sex differences. In making a statistical evaluation of the scores on the various tests it is necessary that we determine not only whether there are sex differences in the population as a whole, but also whether the extent of any difference is comparable across the two countries. Both questions can be addressed with an analysis which pools the scores on each test across gender within each country and converts them to culture-specific Z-scores (Zcs-Scores). This analysis has the advantage of standardizing the scores within each country by establishing a mean of zero and variance unity, so that we may turn to the question of sex differences and their comparability across the two cultures. The Zcs-Scores appear in Table 3, which compares the scores of males and females within the American and Japanese populations, giving the average value for each sex on each test. When these Zcs-Scores were used as the dependent variables in a series of A N O V A ' s with
V. A. MAyy et al.
1068
Table 1. Sex differences in cognitive abilities: mean scores of American high school juniors N
Male students Mean SD
N
Female students Mean SD
Handedness quotient
74
1.14
2.4
47
1.45
3.1
Word fluency: F (1 min) A S Total
74 74 74 74
13.14 11.15 14.85 39.14
3.8 3.2 3.3
47 47 47 47
13.00 11.63 15.45 40.08
3.4 3.8 4.0
Word fluency: W (3 min) R Total
74 74 74
24.82 25.10 49.90
5.9 6.9
47 47 47
25.60 25.56 51.16
6.3 6.6
Story Recall: I II
66 66
16.7() 15.67
5.5 6.2
51 51
19.55 18.88
5.7 5.5
Digit-Symbol Symbol Copying Mental Rotation Mazes Arithmetic
66 66 74 74 66
78.92 112.41 24.24 4.65 19.71
13.0 24.8 9.7 0.5 5.1
51 51 47 47 51
83.80 116.24 18.38 4.43 20.18
II.I 7.l 7.9 0.6 4.9
Nonsense Word Recognition First half 66 Second half 66
16.12 15.81
2.0 1.8
51 51
t6.29 15.59
1.9 1.8
Nonsense Design Recognition First half 66 Second half 66
14.88 12.72
2.3 2.4
51 51
15.03 13.33
2.5 2.6
gender and culture as between-subjects factors, the results revealed that the male students had a v e r a g e d higher scores on the M e n t a l R o t a t i o n test, F ( 1 , 2 9 5 ) = 4 4 . 5 5 , P < 0 . 0 0 0 and that this difference r e m a i n e d equivalent across the two countries, as indicated by a lack of interaction between gender and country.* T he female students had averaged higher scores than the male students on the Story Recall test, F (1, 2 8 9 ) = 39.78, P < 0 . 0 0 0 , the Digit S y m b o l test, F ( I , 2 6 9 ) = 1 2 . 1 0 , P < 0 . 0 0 0 and the W o r d Fluency test, F ( 1 , 2 9 0 ) = 14.01, P < 0 . 0 0 0 . O n both the Story Recall test and the Digit S y m b o l test, the extent of a d v a n t a g e was relatively c o n s t a n t across the two countries, there was no interaction between sex and country. H o w e v e r , for the W o r d F l u e n c y test there was a significant interaction between gender and country, F ( 1 , 2 9 0 ) = 6 . 2 6 . N e u m a n - K e u l s tests revealed that, a l t h o u g h the females in both countries had a v e r a g e d higher scores than the males, the sex difference was only significant in the case of the J a p a n e s e subjects, q (4, 2 9 0 ) = 5.85, P < 0.001. Th er e were no o t h er main effects n o r interactions in the analysis of the verbal tests. (In the analysis of the story recall test, the i m m e d i a t e and delayed scores were treated as a repeated measure. In the W o r d Fluency test, the time allowed for r e s p o n d i n g was treated as a repeated measure using the average of the three 1 min scores vs the average of the two 3 min scores.) All of the r e m a i n i n g tests the A r i t h m e t i c test, the M a z e test and the S y m b o l C o p y i n g test indicated no significant effect of gender and no interaction bctwecn gender and country. The M e m o r y test indicated no main effect of gender and no interaction bctwccn *A separate analysis of the American data which considered the alternative system mentioned in the M e t h o d s section reveals that the male advantage obtained equally for that systcm F (1,22)= 14.642, P 10 S.D. Mean
Handedness quotient Incidence: male female
66 33 33
0.00 0.38 0.38
0.0
5 2 3
1 t.00 0.02 0.03
0.2
Word fluency: KA {I min) TO SE Total
66 66 66
11.81 9.89 9.70 31.40
3.7 3.7 3.9
5 5 5
13.20 10.40 11.40 35.00
2.2
Word fluency: SHI (3 mini KO Total
66 66
26.11 23.77 49.88
8.6 10.2
5 5
28.20 26.40 54.40
5.8 6.9
Story Recall: 1 II
66 66
26.12 26.71
7.9 7.8
5 5
27.60 29.40
5.0 5.0
Digit-Symbol Symbol Copying
63 62
74.03 122.83
8.6 14.4
5 5
85.00 124.40
3.7 10.2
Mental Rotation Mazes Arithmetic
66 66 61
28.83 4.21 25.64
6.7 0.6 3.8
5 5 5
29.40 4.40 23.40
4.2 0.5 7.3
Nonsense Word Recognition First half 63 Second half 63
18.21 17.26
1.9 2.0
5 5
18.00 17.00
1.2 1.0
Nonsense Design Recognition First half 63 Second half 63
16.73 14.11
2.5 2.9
5 5
16.80 13.40
2.5 3.8
2.3 3.9
i n d i v i d u a l d i f f e r e n c e s in c o g n i t i v e skill. H o w e v e r , it s h o u l d b e k e p t in m i n d t h a t t h e differences between the average male and female scores are relatively small when compared w i t h t h e r a n g e of d i f f e r e n c e s t h a t o c c u r w i t h i n e a c h sex. It s h o u l d a l s o b e n o t e d t h a t we o b s e r v e r e l a t i v e , n o t a b s o l u t e s u p e r i o r i t y . G i v e n t h a t t h e l a r g e s t s i g n i f i c a n t d i f f e r e n c e we o b t a i n is less t h a n o n e s t a n d a r d d e v i a t i o n , a n d m o s t a r e less t h a n a h a l f o f a s t a n d a r d d e v i a t i o n , o u r r e s u l t s d o n o t w a r r a n t d i f f e r e n t e d u c a t i o n a l g o a l s for m e n a n d w o m e n , o r d i f f e r e n t c a r e e r a s p i r a t i o n s . G i v e n t h a t t h e girls a v e r a g e d " s u p e r i o r " s c o r e s o n c e r t a i n p o r t i o n s o f t h e test b a t t e r y a n d t h e b o y s a v e r a g e d s u p e r i o r s c o r e s o n a n o t h e r , we a l s o c a n n o t g o v e r y far t o w a r d s e x p l a i n i n g w h y m a l e h i g h s c h o o l s t u d e n t s a c h i e v e h i g h e r S c h o l a s t i c A c h i e v e m e n t test ( S A T ) s c o r e s , c o m p l e t e m o r e y e a r s o f e d u c a t i o n , etc. B u t t h e s e c o n s i d e r a t i o n s s h o u l d n o t d e t e r us f r o m p u r s u i t o f " b i o l o g i c a l l y - b a s e d " a c c o u n t s of i n d i v i d u a l d i f f e r e n c e s , j u s t as t h e p u r s u i t o f " b i o l o g i c a l - a c c o u n t s " s h o u l d n o t p r e c l u d e t h e p o s s i b i l i t y t h a t s o m e , as yet u n i d e n t i f i e d s o c i o l o g i c a l f a c t o r s a l s o p l a y a n i m p o r t a n t role.
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