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…

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)