Family Configuration and Mental Ability: Two Theories Contrasted with U.S. Data

Recent articles have argued that family size & birth order have important cognitive influence, & may partially explain the different performances of SC & ethnic groups. Support for such claims has often depended on an analytic strategy concentrating on the means of aggregated groups with large numbers. Data are reviewed from the US National Longitudinal Study of Educational Effects (N = 22,000 Ss). When individual variation is explored, the effects of family configuration become relatively trivial, & the confluence theory appears untenable. The apparent effects of family size, far from explaining population differences, seem themselves to be better explained as the result of group admixtures. And the small, residual birth-order effects therefore appear to result from other unexplained phenomena. 4 Tables, 6 Figures. Modified HA.