Classification, relative thinking, and transitivity performance by retarded individuals.

Thirteen retarded adults at each of three MA levels (5 to 6, 7 to 8, 9 to 12) were assessed on classification relatively, and transitivity performance. Analyses of covariance, with IQ effects factored out, showed significant MA effects for all three tasks (ps less than .01), and analyses of variance across tasks at each MA level also showed significant task effects at each level (ps less than .01). Binomial test analyses of the proportions of subjects performing discrepantly in both directions on each pair of tests were also conducted. The results indicated a sequential order of development of classification, relatively, and transitivity operations, in that order.