Racial differences in environmental influences on numerical ability as determined by heritability estimates.

Abstract

172 pairs of MZ twins and 112 pairs of like-sexed DZ twins were given Mukherjee's Simple Arithmetic Test. 242 were boys and 326 girls, of whom 482 were white and 86 Negro. Ages ranged from 13 to 18 yr. Using four different heritability ratios the relative intrapair similarity of MZ and like-sexed DZ twins on a test of numerical ability was determined. Heritability ratios are not significantly lower for Negroes than for whites. Environment cannot be credited with playing a more significant role in the development of numerical ability of Negro than of white children.