The effects of distributed study, self-pacing, a criterion of mastery, and individualized testing were examined by assigning 422 students in an introductory psychology course to one of four different teaching/learning systems. The first encompassed a traditional lecture/discussion group format. The second employed the personalized system of instruction (PSI) method, consisting of programmed instructional materials, individualized unit-testing and a criterion of mastery. The third required the student to write a weekly test covering the assigned chapter in the text; students were tested in groups and there was no criterion of mastery. The fourth group wrote weekly tests with a mastery criterion. They received credit only if they passed the unit tests on one of three trials. The means of the scores on a common final exam differed significantly for all four groups. The PSI group achieved the highest mean scores, followed by the weekly testing groups, with and without mastery. The group exposed to the traditional lecture/seminar format had the lowest mean score. Six references and one table are included. (Author/CHC)