Forty-one middle school students in two eighth-grade classes were taught half of their science chapters in the conventional manner with homework assignments, and half of their chapters by having short classroom quizzes on each unit. Quizzes were expected to stimulate incentive motivation as a mediator between a goal object, mastery, and the responses necessary to attain that objective, effective studying. Quizzes had already proven effective with college students. Chapter mastery was measured by multiple-choice tests accompanying the textbook. Students completed the first five chapters doing homework and the second five doing quizzes, with chapter pairs matched for difficulty across condition in an equivalent time samples design. Results indicated that on the first pair of chapters, students given homework outperformed students given quizzes; on the second and third pairs, there were no differences between conditions; on the fourth and fifth pairs, quizzed students significantly outperformed homework students, the final difference reaching an effect size of almost .50. Based on the findings, it was concluded that regularly-occurring quizzes can become a motivator to study or a stimulator of self-regulatory behavior, even though initially they may not have that effect. (Contains 20 references.) (Author/SD)