Genetic effects on specific cognitive abilities as distinct from those on general cognitive ability were studied in 302 pairs of twins (some reared together, some apart) from the Swedish Adoption/Twin Study of Aging. Overall, results showed significant genetic influence on specific abilities independent of influence on general ability. (SLD)

Scarr and Weinberg's results (Intelligence, 1977) are compared to those of similar adoption studies and found to be quite similar, despite the transracial adoption patterns in Scarr and Weinberg's sample. The author also suggests that the major contribution of behavioral genetics to psychology may be our increased understanding of the environment.…

The Ramey and Haskins intervention experiment is examined. Narrow transfer of training from cognitive intervention techniques to IQ test performance in early childhood, rather than enhancement of the g factor itself, is hypothesized as a cause of the typical fadeout of early IQ gains in later childhood. (Author/RD)

Ramey and Haskins report two findings of major importance: absence of decline in test scores and absence of mother-child correlation for treated children. Implications of these findings are discussed. (Author)

Extensive data on twins, nontwin siblings, siblings separated by adoption, and parent-child similarity indicate that the heritability of intelligence is closer to .50 than to .70. Differences could be due to environmental or genetic changes in the population, or to methodology. (Author/CP)

Wolff has recently reinterpreted the data of Lee to indicate that Black migration from the south to Philadelphia had been selective in an IQ-relevant manner. However, Wolff's deduction from Lee's data is shown to depend entirely upon an assumption about cumulative IQ deficit in southern Black children. (Author/CTM)

Kamin has contended that arguments presented in Wolff are too weak to justify selective migration. Although Kamin's critique points up the need for closer scrutiny of the cumulative-deficit phenomenon, it fails to refute Wolff's conclusion that selective migration is partly responsible for the North-South Black IQ differential. (Author/CTM)

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)