This book reports on a study of 850 pairs of twins who were tested to determine the influence of heredity and environment on individual differences in personality, academic ability, and interests. It presents the background, research design, and procedure of the study, tabulations of the test results, and extensive analyses of the findings.…

This book is considered to provide a sober, balanced, and scholarly examination of the evidence that bears on the role of genetic and environmental factors in the determination of group differences in ability in the United States. The first chapter provides something of the background and recent history of the concern with racial-ethnic…