On the Causes of IQ Differences between Groups and Implications for Social Policy

This paper presents an analysis, supported by recently published data, which suggests that IQ differences between groups may be explained by environmental factors. Jensen's hypothesis that such differences may be primarily genetic is critically examined and rejected on the basis of his misinterpretation of the meaning of the concept of heritability, the difficulties with the heritability formula, and several studies which indicate that when environmental factors are controlled the correlation between IQ and race vanishes. An alternative approach to the analysis of IQ differences between groups is then presented which emphasizes differential diffusion of the cognitive components measured in IQ tests, and differential nutritional advantages. In conclusion, the implications of this approach for social policy are discussed and suggestions are made concerning the need for a greater emphasis on the analysis of American social and national needs in the training of anthropologists.