THE INFLUENCE OF PATERNAL SOCIAL CLASS ON INTELLIGENCE AND EDUCATIONAL LEVEL IN MALE ADOPTEES AND NON‐ADOPTEES

Abstract

Summary. Intelligence test scores and educational level of 241 18–26 year‐old male adoptees correlate with the social class of both their biological fathers (r = 0.218, P < 0.01; and r = 0.173, P < 0.05) and their adoptive fathers (r = 0.216, P < 0.01; and r = 0.359, P < 0.001). The correlation between the biological father's social class and the adoptee's educational level may be largely mediated by the inheritance of characteristics more directly measured by the intelligence test. Conversely, the correlation between the adoptive father's social class and the adoptee's intelligence test score may be largely mediated by familial environmental influences on educational level. The multiple correlations of both biological and adoptive fathers' social classes with the adoptees' intelligence test scores (R = 0.292, P < 0.001) and with adoptees' educational level (R = 0.384, P < 0.001) do not differ significantly (z < 0.6, NS) from the simple correlations of fathers' social class with sons' intelligence test scores and educational level in a non‐adoptive control sample of 4,020 father‐son pairs (r = 0.320, P < 0.001; and r = 0.417, P < 0.001). This suggests that familial influences on intelligence test scores and educational level may be adequately accounted for by an additive model including both genetic and familial environmental components.