The aptitude-achievement test distinction: a study of unrelated children reared together.

Unrelated children reared together (N = 156) in 71 different families included in the Texas Adoption Project were compared for similarities on intelligence and achievement tests. The purpose was to see if a distinction between the two types of tests based on their heritabilities could be sustained. Results indicated no substantial differences in correlations for the two types of tests, and hence little or no support for the notion of an aptitude-achievement distinction based on differential heritabilities.