Race Differences in Intelligence

Bootzin, Richard R.; Loehlin, John C.; Lindzey, Gardner; Spuhler, J. N.

doi:10.2307/1421415

Cited by 76 publications

(12 citation statements)

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“…This was again considered as a general parental education factor for the same reasons just mentioned. Again, this result agrees with previous findings relating SES to cognitive performance, and particularly verbal ability [4,35,47,54,81,102]. In addition to this parental influence, the twins' sex (girls performed better) accounted for 2% of the total PPVT variance (Table 19).…”

Section: Environmental Analysessupporting

confidence: 90%

“…Therefore, the intraclass correlational results for the cognitive tests can also be considered generally representative. However, socioeconomic differences have a stronger influence on cognitive performance than on height and weight [47]. Because this sample was not as heterogeneous in socioeconomic status as one would have preferred, it is possible that the variance between families, and therefore the intraclass correlations, may have been less than expected in a random sample.…”

Section: Genetic Influencesmentioning

confidence: 99%

“…Marjoribanks [54] found that socioeconomic status (SES) and other family environment variables were more highly correlated with mathematical achievement than with IQ among British children over 7 years of age. Since parental IQ is known to be correlated with SES, and since it is also correlated with offspring cognitive functioning, the effect of this socioeconomic variable could be confounded with hereditary influences [47,80]. Consequently, although SES is an important aspect of environmental influence on the development of logico-mathematical concepts, environmental measures more independent of genetic influences are needed [54].…”

Section: Environmental Influences On Mathematical Abilitymentioning

confidence: 99%

“…This is consistent with the fact that the WPPSI is more information-and achievement-oriented than these specific ability measures. At the same time, a child's IQ may be more related to parental occupation and education because of the association of parental IQ with these variables [47], and the possible higher assortative marriage for IQ than for specific cognitive abilities [48]. In other words, WPPSITQ may be more related to parental IQ than are performances on the PMCB, PM, and PPVT.…”

Section: Environmental Analysesmentioning

confidence: 99%

“…In other words, WPPSITQ may be more related to parental IQ than are performances on the PMCB, PM, and PPVT. And, of course, parental IQ has its own genetic variance [47]. Thus, the higher correlation between WPPSI IQ and parental occupation and education may indirectly represent a greater genetic influence on IQ and achievement than on these specific cognitive abilities.…”

Section: Environmental Analysesmentioning

confidence: 99%

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Genetic and Environmental Influences on the Development of Piagetian Logico-Mathematical Concepts and Other Specific Cognitive Abilities:A Twin Study

Garfinkle

1982

Acta genet. med. gemellol.: twin res.

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The classical twin study method was used to assess the relative contributions of genetic and environmental components to individual variation in several aspects of cognitive functioning. Tests of logico-mathematical concept formation, as well as vocabulary, nonverbal reasoning, and visual memory, were administered to 137 MZ and 72 DZ, same-sex white twin pairs. These children were individually tested on the Piagetian Mathematical Concepts Battery (PMCB), Peabody Picture Vocabulary Test (PPVT), Raven Coloured Progressive Matrices (PM), and a Visual Memory (VM) test. The Attitudes Toward Education (ATE) questionnaire and the Moos [63] Family Environment Scale (FES) were used to collect additional data from the parents. Twins were 4 to 8 years old, with a mean age of 71 months, and most were from middle- and upper-middle-class families. Zygosity was determined from dermatoglyphic information and responses to a questionnaire asking mothers about twin similarities and confusion between the twins by others. These data were analyzed by a simple pair concordance procedure and by a discriminant function analysis. In addition, blood typing was done on 32 pairs for whom zygosity was not possible to determine by these methods.Previously reported patterns of intercorrelations among the 10 subscales of the FES, as well as the subscale structure, were verified by factor analysis. A factor analysis of the ATE yielded three factors: Basic Academic Education, Parental Participation, and General Utility of Education. These factors correlated significantly (P < 0.01) with various environmental indices (including father's occupation and education, Achievement Orientation, Expressiveness, etc). A factor analysis of the PMCB tasks gave some support for the existence of Piaget's underlying concepts of conservation of number, seriation, and classification.No sex differences were found for any of the specific cognitive abilities or any of the environmental variables. Correlations with age were substantial: 0.75 for PMCB, 0.70 for PPVT, 0.59 for PM, and 0.43 for VM. Because of the high correlations with age, the effect of age on these variables was partialed out in all further analyses. PMCB correlated most highly with PM (r = 0.41), and with PPVT (r = 0.36). Nonverbal reasoning and vocabulary were relatively independent of each other (r = 0.23). Correlations between visual memory and all other tests were low.MZ and DZ intraclass correlations for height and weight were similar to values reported in other studies. After correcting for test reliability, significant genetic variance (P < 0.01) was found for both PMCB and PPVT, and was suggested for VM. Genetic variance for PM was not significant (P > 0.05). Correction for reliability could not be employed in this case because an accurate estimate of the PM test–retest reliability is not available. There was no significant effect of age on the magnitude of the MZ or DZ intraclass correlations.A stepwise multiple regression on the environmental variables was performed for each cognitive test. The environmental variables considered were number of siblings, parental education and occupation, the 10 FES subscales, and the three ATE factors. Age was entered first in the regression equation for each test, and it accounted for 18% to 57% of the total variance in cognitive performance. Parental education accounted for 3% of the total variance in both PMCB and PPVT performance. This was considered as an environmental influence, but the possible confounding with a genetic element in parental IQ was discussed. Achievement Orientation exhibited a significant negative relationship (R2 = 0.02) with PM performance. Cohesion in the Family was positively related to PPVT performance (R2 = 0.02). In addition, Intellectual–Cultural Orientation predicted VM performance (R2 = 0.02). Overall, those environmental variables found to have a small effect suggest the value of a warm, stimulating, supportive (but not “pushy”) family environment for normal cognitive development in young children.Examination of the genetic and environmental results indicated that 49% of the variance in age-corrected PMCB performance was accounted for by the genetic variance (estimated from twin comparisons) and parental education. Similarly, variables identified in this investigation accounted for 60% of the variance in age-corrected PPVT performance, 29% of the age-corrected PM performance, and 32% of age-corrected VM performance.In conclusion, this was the first large twin study to find both genetic and environmental influences on the development of Piagetian logico-mathematical concepts and other specific cognitive abilities. The results illustrate the feasibility of investigating cognitive development in a theoretical framework such as Piaget's.

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