One hundred eighty one sets of black twins and 223 sets of white twins provided responses to four 12-item subtests of the Raven's Progressive Matrices Test, Standard Version. The children were in elementary school and their item response patterns were analyzed with the use of revised ordering-theoretic methods to search for best-fitting…

Swedish longitudinal studies of twins support Scarr-Salapatek's explanation of nature-nurture influences on intelligence. This model predicts more genetic variance in test results for advantaged than disadvantaged groups. Jensen's work, however, suggests equal amounts of variance among different social classes. (Author/CP)

A case study of a pair of extremely deprived twin boys focuses on their verbal communication. Talkativeness alone was not regarded as a measure of intelligence, but attention was paid to the less talkative twin's greater use of imaginative speech. Speculations are made on the evolutionary role of creative speech. (IS)