Race, social class and ability patterns on the WISC-R

The national standardization sample of whites and blacks on the Wechsler Intelligence Scale for Children—Revised (WISC-R) was the basis for a detailed analysis of the psychometric nature of racial and social class differences on the original 13 subscales of the WISC-R. The profiles of subtest scores of whites and blacks were compared directly and also after the racial groups were statistically equated on Full Scale IQ (FSIQ). Under the latter condition, the races differ only very slightly, although significantly, on some of the subtests, in ways generally contrary to popular expectations. The profile of white-black differences on the WISC-R subtests is markedly different, and negatively correlated with, the profiles of social class differences within each racial group, indicating that the pattern of racial differences is not explainable in terms of the difference in the average socio-economic status (SES) of blacks and whites. A Schmid-Leiman orthogonalized hierarchical factor analysis yields virtually identical factor structures and highly congruent factor loadings on the subtests for whites and blacks. Analysis of factor scores shows that by far the largest proportion of the variance between races is attributable to the general factor (g) common to all the subtests, whereas the group factors (verbal, performance and memory) contribute only minutely to the interracial variance. Hence the white-black differences on the diverse subtests of the WISC-R, and in the Full Scale IQ, are interpreted primarily as a difference in Spearman's g, rather than as differences in the more specific factors peculiar to particular content, knowledge, acquired skills or type of test. However, some slight but significant differences in patterns of ability also occur that are independent of g.