Persons representing the extremes of intelligence cannot be included in the same study unless they are approximately equated on mental age, in which case the relative performances of the extreme groups can provide useful information about the nature of intelligence. (Author/RD)

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.…

Recent studies are examined for methodological adequacy in establishing dimensions of individual differences in information-processing abilities, and the theoretical problems involved in inferring psychological processes from individual difference dimensions. Methodological inadequacies include use of small samples, questionable procedures in…

In studies of the relationship between masculinity-femininity and intelligence, data should be analyzed using correlational analysis for the complete distribution, rather than analysis of variance of extreme groups. The earlier work of Baucom and Welsh (EJ 171 822) was used as illustration. (BW)

Humphreys' criticisms (TM 503 269) of the work of Welsh and Baucom (EJ 171 822) are inappropriate since his findings are based upon a different measure of masculinity-femininity and a population which is somewhat different. Also, his insistence on correlational analysis to the exclusion of extreme group design is viewed as inappropriately…

A reply to Plomin's critique and some criticisms of Munsinger's review of adopted child literature are presented. Selective bias in adoptee samples, implicit assumptions in models that lead to heritability estimates, and problems produced by lack of an accepted model of environmental transmission are also discussed. (Author/RD)