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Cognitive abilities profiles of Caucasian vs Japanese subjects in the Hawaii Family Study of Cognition
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Person. in&id. Dl# Vol. 8, No. 4, pp. 581-583, 1987 Printedin Great Britain
Cognitive
Pergamon Journals Ltd
abilities profiles of Caucasian vs Japanese Hawaii Family Study of Cognition CRAIG T. NACOSHI
and
subjects in the
RONALD C. JOHNSON’
Institute for Behavioral Genetics, Campus Box 447, Universily of Colorado, Boulder, CO 80309 and ‘Behavioral Biology Lab, 115 Snyder Hall, University of Hawaii, Honolulu, HI 94822, U.S.A. (Received 30 May 1986)
Summary-General intelligence (the unrotated first principal component) was partialled out of the cognitive abilities factors-verbal ability, spatial ability, perceptual speed, and visual memory-obtained for the 15 tests of cognitive abilities used in the Hawaii Family Study of Cognition (HFSC). The resulting cognitive abilities profiles indicated that HFSC subjects of Caucasian ancestry scored higher relative to subjects of Japanese ancestry on the verbal and visual memory factors, but lower on the spatial and perceptual speed factors. This ethnic group difference in the shape of the cognitive abilities profiles was found to be highly consistent across sexes and generations, in spite of the large mean differences across these groups in factor scores.
Several recent, large-scale studies have sought to compare the cognitive abilities of Americans vs Japanese. Although both societies have achieved similar levels of industrialization, technological sophistication, and literacy, their genetic backgrounds, written and spoken languages, cultural traditions, and educational systems differ in a number of fundamental ways. These differences might be expected to produce differences between Americans and Japanese in the overall level, structure, and development of intelligence. It is now well established that cognitive abilities factor structures are virtually identical for American and Japanese samples, i.e. that the same kinds of abilities are apparently measured when diverse batteries of cognitive tests are administered to members of either group. Lynn and Hampson (1986), using data from the American and Japanese standardization samples (children aged 616 yr) for the Wechsler Intelligence Scale for Children-Revised (WISC-R) (Wechsler, 1974) obtained nearly identical loadings on the unrotated first principal component (a measure of general intelligence or g) and for the Varimax-rotated three-factor structure of verbal, perceptual, and memory ability. Stevenson, Stigler, Lee, Lucker, Kitamura and Hsu (1985) using their own measures on large, representative samples of American and Japanese first and fifth graders, also found identical if less differentiated factor structures in the two groups. Loadings on the unrotated first principal component and on the Varimax-rotated four-factor structure-verbal ability, spatial ability, perceptual speed, and visual memory-were also found to be virtually identical for teenaged offspring and their parents of Caucasian [Americans of European ancestry (AEA)] and Japanese [Americans of Japanese ancestry (AJA)] ancestry tested in the Hawaii Family Study of Cognition (HFSC) (DeFries, Johnson, Kuse, McCleam, Polovina, Vandenberg and Wilson, 1979; Nagoshi, Johnson, DeFries, Wilson and Vandenberg, 1984; Wilson, DeFries, McClearn, Vandenberg, Johnson, Mi and Rashad, 1975). Having established the functional equivalence of cognitive abilities measures used in the United States and Japan, studies have then compared the mean scores for general intelligence for representative samples of children from the two countries. While some studies (e.g. Misawa, Motegi, Fujita and Hattori, 1984) have found significantly higher mean IQs for the Japanese compared to the American samples, Stevenson et al. (1985) found no significant differences. Interpretation of these comparisons of mean IQs is difficult, given the lingering doubts about the metric equivalence of the measures used in the two societies. Given the nature of the genetic and cultural differences noted above between the United States and Japan, perhaps a more interesting question is whether different specific cognitive abilities are more highly developed in one society as opposed to the other. Stevenson et al. (1985) found few consistent differences in specific abilities between Americans and Japanese, but their regression analyses suggested that different abilities were associated with reading and mathematics achievement in the two countries. Lynn and Hampson (1986) found that, relative to American children, Japanese children were inferior on WISC-R subsets measuring verbal ability and perceptual speed, but were superior on memory span, number ability, and spatial ability. A number of plausible genetic and/or cultural hypotheses may be suggested to account for this pattern of results, Data from the Hawaii Family Study of Cognition not only provide an opportunity for replicating Lynn and Hampson’s findings, but also for narrowing down the number of hypotheses that could possibly account for obtained differences in cognitive abilities profiles of Japanese and Americans. Nearly all of the AJA parents in the HFSC grew up and were educated in Hawaii, although most of their parents were from Japan and usually spoke Japanese in the home. The educational and occupational attainments of this Japanese grandparent generation were considerbly less than the comparable Caucasian grandparent generation, but the AEA and AJA parents tested in the HFSC were highly comparable in education and occupational status (Johnson, Nagoshi, Ahern, Wilson, DeFries, McClearn and Vandenberg, 1983). HFSC parents of Japanese ancestry thus experienced considerably more environmental change and social mobility than those of Caucasian ancestry. AEA and AJA offspring in the HFSC, on the other hand, all grew up and were educated in very similar American environments. This differential environmental change- _ probablv accounts for the substantial increase in coenitive abilities scores of offspring over the parent generation for the AJA families in the HFSC (DeFries, Corley, Johnson, Vandenberg and Wilson, 1982; Nagoshi and Johnson, 1985). This differential environmental change might also be expected to produce a change in the cognitive abilities profiles of AJA offspring compared to their parents. 581
582
NOTES
AND
SHORTER
COMMUNICATIONS
METHOD
Subjects A total of 1816 families (both biological parents and one or more of their teenaged or older offspring, for a total of 6581 individuals) took part in the HFSC [see DeFries et al. (1979) and Wilson et al. (1975) for descriptions of the HFSC]. Americans of European ancestry (AEA; 926 families) and Americans of Japanese ancestry (AJA: 368 families) were the two largest racial/ethnic groups tested in Hawaii. Measures The 15 tests that make up the HFSC cognition battery, as well as the alpha reliabilities of the tests and their loadings on the four Varimax-rotated factors verbal ability, spatial ability, perceptual speed, and visual memory. are presented in DeFries et al. (1979) and Wilson et al. (1975). As noted above, both the loadings on the unrotated first principal component and the loadings on the four-factor structure have been found to be virtually identical across racial/ethnic groups. as well as across sexes and generations. For the present report, only the four cognitive abilities factor scores calculated for the entire HFSC sample are used to define the cognitive abilities profiles for each group. Since the interest here is the magnitude of an ability relative to the other abilities, within each ethnic group, the unrotated first principal component score was first partialled out of each of the factor scores, and these adjusted factor scores were then standardized (mean = 0. SD = I) around the mean first principal component score for each ethnic group. Sex and generational differences are thus maintained within each ethnic group, while allowing for standardized comparisons across ethnic groups. RESULTS AND DISCUSSION
the adjusted cognition factor means by generation (parent vs offspring), sex, and ethnic group (AEA factor, the AEA-AJA mean difference is remarkably consistent across the four generation x sex combinations, with AEA subjects scoring between 0.43 and 0.62 SD units higher than AJA subjects on verbal ability. 0.1&0.20 SD units lower on spatial ability, 0.624.83 SD units lower on perceptual speed, and 0.05 0.25 SD units higher on visual memory. The above results could be due to differential sampling of AEA and AJA subjects in Hawaii, but the higher verbal and lower spatial abilities of AEA subjects compared to AJA subjects do agree with the findings of Lynn and Hampson (1986) using subjects born and raised in Japan vs those born and raised in the United States, It is possible that the discrepancies on the perceptual speed and memory factors are due to differences between the WISC-R and the HFSC test batteries in the tests that define those factors. Table
1 presents
vs AJA). For each cognition
Table
I. HFSC
cognition
factor
means
controlhng
for first prmctpal ethnicitv
component*
Parents Males AEAt AJA: Verbal factor Spatial factor Perceptual speed factor Visual memory factor N
-0.113 0.278 PO.548 -0.207 998
-0.647 0.442 0.112 PO.255 358
by generatmn.
sex, and
Offspring Females AEA AJA
0.342 -0.725 -0.153 0. I55 963
-0.281 PO.527 0.672 0.001 409
Males AEA
AJA
-0.103 0.378 PO.731 -0.113 747
-0.481 0.576 -0.100 PO.266 269
Females AEA AJA 0.208 - 0.65 I 0.010 0.145 716
-0.227 -0.457 0.627 ~0.100 262
*Factor score after partialling out the first principal component score wthin each ethnic group separately: expressed m terms of SD umts from the respective ethnic group first principal component mean. tAmericans of European ancestry. fAmericans of Japanese ancestry.
The remarkable consistency of the AEA-AJA difference in cognitive spite of the considerable sex differences in profiles (see Table 1) and the generations, suggests that these ethnic group profile differences are due influences independent of the type of education and language acquisition that historical aspects of Japanese social organization and/or the use of individuals for certain cognitive abilities.
abilities profiles across sexes and generations, in effects of differential environmental changes across to genetic factors and/or pervasive environmental these Hawaii subjects received. One could speculate an ideographic written language may have selected
Acknowledgements-The results reported here are made possible by a collaboration of a Ashton, R. C. Johnson, M. P. Mi, and M. N. Rashad at the University of Hawaii and J. S. G. Vandenberg, and J. R. Wilson at the University of Colorado) supported by NSF HD-06669 from the National Institute of Child Health and Human Development. We suggesting the analyses reported herein and for other helpful comments.
group of investigators (G. C. C. DeFries, G. E. McClearn, Grant GB-34720 and Grant thank Dr Richard Lynn for
REFERENCES
DeFries J. C., Corley R. P., Johnson R. C., Vandenberg S. G. and Wilson J. R. (1982) Sex-by-generation and ethnic group-by-generation interactions in the Hawaii Family Study of Cognition. Eehav. Genet. 12, 2233230. DeFries J. C., Johnson R. C., Kuse A. R., McClearn G. E., Polovina J., Vandenberg S. G. and Wilson J. R. (1979) Family resemblance for specific cognitive abilities, Behav. Genet. 9, 2343. Johnson R. C., Nagoshi C. T., Ahern F. M., Wilson J. R., DeFries J. C., McClearn G. E. and Vandenberg S. G. (1983) Family background, cognitive ability, and personality as predictors of educational and occupational attainment. Sot. Biol. 30, 86100. Lynn R. and Hampson S. (1986) The structure of Japanese abilities: an analysis in terms of the hierarchical model of intelligence. Curr. Psychol. Res. Rev. In press.
NOTES AND
SHORTER COMMUNICATIONS
583
Misawa G., Motegi M., Fujita K. and Hattori K. (1984) A comparative study of intellectual abilities of Japanese and American children on the Columbia Mental Maturity Scale. Person. indioid. D# 5, 1733182. Nagoshi C. T. and Johnson R. C. (1985) Ethnic group-by-generation interactions in WAIS scores in the Hawaii Family Study of Cognition. Intelligence 9, 259-264. Nagoshi C. T., Johnson R. C., DeFries J. C., Wilson J. R. and Vandenberg S. G. (1984) Group differences and first principal component loadings in the Hawaii Family Study of Cognition: a test of the generality of ‘Spearman’s hypothesis’. Person. individ. D$ 5, 751-753. Stevenson H. W., Stigler J. W., Lee S., Lucker G. W., Kitamura S. and Hsu C. (1985) Cognitive performance and academic achievement of Japanese, Chinese, and American children. Child Deu. 56, 718-734. Wechsler D. (1974) Manual for the Wechsler Intelligence Scale for Children-Revised. The Psychological Corporation, New York. Wilson J. R., DeFries J. C., McCleam G. E., Vandenberg S. G., Johnson R. C., Mi M. P. and Rashad M. N. (1975) Use of family data as a control to assess sex and age differences in two ethnic groups. Inr J. Aging Hum. Da. 6, 261-276.
Person. in&id. Dl# Vol. 8, No. 4, pp. 581-583, 1987 Printedin Great Britain
Cognitive
Pergamon Journals Ltd
abilities profiles of Caucasian vs Japanese Hawaii Family Study of Cognition CRAIG T. NACOSHI
and
subjects in the
RONALD C. JOHNSON’
Institute for Behavioral Genetics, Campus Box 447, Universily of Colorado, Boulder, CO 80309 and ‘Behavioral Biology Lab, 115 Snyder Hall, University of Hawaii, Honolulu, HI 94822, U.S.A. (Received 30 May 1986)
Summary-General intelligence (the unrotated first principal component) was partialled out of the cognitive abilities factors-verbal ability, spatial ability, perceptual speed, and visual memory-obtained for the 15 tests of cognitive abilities used in the Hawaii Family Study of Cognition (HFSC). The resulting cognitive abilities profiles indicated that HFSC subjects of Caucasian ancestry scored higher relative to subjects of Japanese ancestry on the verbal and visual memory factors, but lower on the spatial and perceptual speed factors. This ethnic group difference in the shape of the cognitive abilities profiles was found to be highly consistent across sexes and generations, in spite of the large mean differences across these groups in factor scores.
Several recent, large-scale studies have sought to compare the cognitive abilities of Americans vs Japanese. Although both societies have achieved similar levels of industrialization, technological sophistication, and literacy, their genetic backgrounds, written and spoken languages, cultural traditions, and educational systems differ in a number of fundamental ways. These differences might be expected to produce differences between Americans and Japanese in the overall level, structure, and development of intelligence. It is now well established that cognitive abilities factor structures are virtually identical for American and Japanese samples, i.e. that the same kinds of abilities are apparently measured when diverse batteries of cognitive tests are administered to members of either group. Lynn and Hampson (1986), using data from the American and Japanese standardization samples (children aged 616 yr) for the Wechsler Intelligence Scale for Children-Revised (WISC-R) (Wechsler, 1974) obtained nearly identical loadings on the unrotated first principal component (a measure of general intelligence or g) and for the Varimax-rotated three-factor structure of verbal, perceptual, and memory ability. Stevenson, Stigler, Lee, Lucker, Kitamura and Hsu (1985) using their own measures on large, representative samples of American and Japanese first and fifth graders, also found identical if less differentiated factor structures in the two groups. Loadings on the unrotated first principal component and on the Varimax-rotated four-factor structure-verbal ability, spatial ability, perceptual speed, and visual memory-were also found to be virtually identical for teenaged offspring and their parents of Caucasian [Americans of European ancestry (AEA)] and Japanese [Americans of Japanese ancestry (AJA)] ancestry tested in the Hawaii Family Study of Cognition (HFSC) (DeFries, Johnson, Kuse, McCleam, Polovina, Vandenberg and Wilson, 1979; Nagoshi, Johnson, DeFries, Wilson and Vandenberg, 1984; Wilson, DeFries, McClearn, Vandenberg, Johnson, Mi and Rashad, 1975). Having established the functional equivalence of cognitive abilities measures used in the United States and Japan, studies have then compared the mean scores for general intelligence for representative samples of children from the two countries. While some studies (e.g. Misawa, Motegi, Fujita and Hattori, 1984) have found significantly higher mean IQs for the Japanese compared to the American samples, Stevenson et al. (1985) found no significant differences. Interpretation of these comparisons of mean IQs is difficult, given the lingering doubts about the metric equivalence of the measures used in the two societies. Given the nature of the genetic and cultural differences noted above between the United States and Japan, perhaps a more interesting question is whether different specific cognitive abilities are more highly developed in one society as opposed to the other. Stevenson et al. (1985) found few consistent differences in specific abilities between Americans and Japanese, but their regression analyses suggested that different abilities were associated with reading and mathematics achievement in the two countries. Lynn and Hampson (1986) found that, relative to American children, Japanese children were inferior on WISC-R subsets measuring verbal ability and perceptual speed, but were superior on memory span, number ability, and spatial ability. A number of plausible genetic and/or cultural hypotheses may be suggested to account for this pattern of results, Data from the Hawaii Family Study of Cognition not only provide an opportunity for replicating Lynn and Hampson’s findings, but also for narrowing down the number of hypotheses that could possibly account for obtained differences in cognitive abilities profiles of Japanese and Americans. Nearly all of the AJA parents in the HFSC grew up and were educated in Hawaii, although most of their parents were from Japan and usually spoke Japanese in the home. The educational and occupational attainments of this Japanese grandparent generation were considerbly less than the comparable Caucasian grandparent generation, but the AEA and AJA parents tested in the HFSC were highly comparable in education and occupational status (Johnson, Nagoshi, Ahern, Wilson, DeFries, McClearn and Vandenberg, 1983). HFSC parents of Japanese ancestry thus experienced considerably more environmental change and social mobility than those of Caucasian ancestry. AEA and AJA offspring in the HFSC, on the other hand, all grew up and were educated in very similar American environments. This differential environmental change- _ probablv accounts for the substantial increase in coenitive abilities scores of offspring over the parent generation for the AJA families in the HFSC (DeFries, Corley, Johnson, Vandenberg and Wilson, 1982; Nagoshi and Johnson, 1985). This differential environmental change might also be expected to produce a change in the cognitive abilities profiles of AJA offspring compared to their parents. 581
582
NOTES
AND
SHORTER
COMMUNICATIONS
METHOD
Subjects A total of 1816 families (both biological parents and one or more of their teenaged or older offspring, for a total of 6581 individuals) took part in the HFSC [see DeFries et al. (1979) and Wilson et al. (1975) for descriptions of the HFSC]. Americans of European ancestry (AEA; 926 families) and Americans of Japanese ancestry (AJA: 368 families) were the two largest racial/ethnic groups tested in Hawaii. Measures The 15 tests that make up the HFSC cognition battery, as well as the alpha reliabilities of the tests and their loadings on the four Varimax-rotated factors verbal ability, spatial ability, perceptual speed, and visual memory. are presented in DeFries et al. (1979) and Wilson et al. (1975). As noted above, both the loadings on the unrotated first principal component and the loadings on the four-factor structure have been found to be virtually identical across racial/ethnic groups. as well as across sexes and generations. For the present report, only the four cognitive abilities factor scores calculated for the entire HFSC sample are used to define the cognitive abilities profiles for each group. Since the interest here is the magnitude of an ability relative to the other abilities, within each ethnic group, the unrotated first principal component score was first partialled out of each of the factor scores, and these adjusted factor scores were then standardized (mean = 0. SD = I) around the mean first principal component score for each ethnic group. Sex and generational differences are thus maintained within each ethnic group, while allowing for standardized comparisons across ethnic groups. RESULTS AND DISCUSSION
the adjusted cognition factor means by generation (parent vs offspring), sex, and ethnic group (AEA factor, the AEA-AJA mean difference is remarkably consistent across the four generation x sex combinations, with AEA subjects scoring between 0.43 and 0.62 SD units higher than AJA subjects on verbal ability. 0.1&0.20 SD units lower on spatial ability, 0.624.83 SD units lower on perceptual speed, and 0.05 0.25 SD units higher on visual memory. The above results could be due to differential sampling of AEA and AJA subjects in Hawaii, but the higher verbal and lower spatial abilities of AEA subjects compared to AJA subjects do agree with the findings of Lynn and Hampson (1986) using subjects born and raised in Japan vs those born and raised in the United States, It is possible that the discrepancies on the perceptual speed and memory factors are due to differences between the WISC-R and the HFSC test batteries in the tests that define those factors. Table
1 presents
vs AJA). For each cognition
Table
I. HFSC
cognition
factor
means
controlhng
for first prmctpal ethnicitv
component*
Parents Males AEAt AJA: Verbal factor Spatial factor Perceptual speed factor Visual memory factor N
-0.113 0.278 PO.548 -0.207 998
-0.647 0.442 0.112 PO.255 358
by generatmn.
sex, and
Offspring Females AEA AJA
0.342 -0.725 -0.153 0. I55 963
-0.281 PO.527 0.672 0.001 409
Males AEA
AJA
-0.103 0.378 PO.731 -0.113 747
-0.481 0.576 -0.100 PO.266 269
Females AEA AJA 0.208 - 0.65 I 0.010 0.145 716
-0.227 -0.457 0.627 ~0.100 262
*Factor score after partialling out the first principal component score wthin each ethnic group separately: expressed m terms of SD umts from the respective ethnic group first principal component mean. tAmericans of European ancestry. fAmericans of Japanese ancestry.
The remarkable consistency of the AEA-AJA difference in cognitive spite of the considerable sex differences in profiles (see Table 1) and the generations, suggests that these ethnic group profile differences are due influences independent of the type of education and language acquisition that historical aspects of Japanese social organization and/or the use of individuals for certain cognitive abilities.
abilities profiles across sexes and generations, in effects of differential environmental changes across to genetic factors and/or pervasive environmental these Hawaii subjects received. One could speculate an ideographic written language may have selected
Acknowledgements-The results reported here are made possible by a collaboration of a Ashton, R. C. Johnson, M. P. Mi, and M. N. Rashad at the University of Hawaii and J. S. G. Vandenberg, and J. R. Wilson at the University of Colorado) supported by NSF HD-06669 from the National Institute of Child Health and Human Development. We suggesting the analyses reported herein and for other helpful comments.
group of investigators (G. C. C. DeFries, G. E. McClearn, Grant GB-34720 and Grant thank Dr Richard Lynn for
REFERENCES
DeFries J. C., Corley R. P., Johnson R. C., Vandenberg S. G. and Wilson J. R. (1982) Sex-by-generation and ethnic group-by-generation interactions in the Hawaii Family Study of Cognition. Eehav. Genet. 12, 2233230. DeFries J. C., Johnson R. C., Kuse A. R., McClearn G. E., Polovina J., Vandenberg S. G. and Wilson J. R. (1979) Family resemblance for specific cognitive abilities, Behav. Genet. 9, 2343. Johnson R. C., Nagoshi C. T., Ahern F. M., Wilson J. R., DeFries J. C., McClearn G. E. and Vandenberg S. G. (1983) Family background, cognitive ability, and personality as predictors of educational and occupational attainment. Sot. Biol. 30, 86100. Lynn R. and Hampson S. (1986) The structure of Japanese abilities: an analysis in terms of the hierarchical model of intelligence. Curr. Psychol. Res. Rev. In press.
NOTES AND
SHORTER COMMUNICATIONS
583
Misawa G., Motegi M., Fujita K. and Hattori K. (1984) A comparative study of intellectual abilities of Japanese and American children on the Columbia Mental Maturity Scale. Person. indioid. D# 5, 1733182. Nagoshi C. T. and Johnson R. C. (1985) Ethnic group-by-generation interactions in WAIS scores in the Hawaii Family Study of Cognition. Intelligence 9, 259-264. Nagoshi C. T., Johnson R. C., DeFries J. C., Wilson J. R. and Vandenberg S. G. (1984) Group differences and first principal component loadings in the Hawaii Family Study of Cognition: a test of the generality of ‘Spearman’s hypothesis’. Person. individ. D$ 5, 751-753. Stevenson H. W., Stigler J. W., Lee S., Lucker G. W., Kitamura S. and Hsu C. (1985) Cognitive performance and academic achievement of Japanese, Chinese, and American children. Child Deu. 56, 718-734. Wechsler D. (1974) Manual for the Wechsler Intelligence Scale for Children-Revised. The Psychological Corporation, New York. Wilson J. R., DeFries J. C., McCleam G. E., Vandenberg S. G., Johnson R. C., Mi M. P. and Rashad M. N. (1975) Use of family data as a control to assess sex and age differences in two ethnic groups. Inr J. Aging Hum. Da. 6, 261-276.