Task differences as moderators of aptitude test validity in selection: A red herring.

This article describes results of two studies, based on a total sample size of nearly 400,000, examining the traditional belief that between-job task differences cause aptitude tests to be valid for some jobs but not for others. Results indicate that aptitude tests are valid across jobs. The moderating effect of tasks is negligible even when jobs differ grossly in task makeup and is probably nonexistent when task differences are less extreme. These results have important implications for validity generalization, for the use of task-oriented job analysis in selection research, for criterion construction, for moderator research, and for proper interpretation of the Uniform Guidelines on Employee Selection Procedures. The philosophy of science and methodological assumptions historically underlying belief in the hypothesis that tasks are important moderators of test validities are examined and critiqued. It is concluded that the belief in this hypothesis can be traced to behaviorist assumptions introduced into personnel psychology in the early 1960s and that, in retrospect, these assumptions can be seen to be false.