What can be done to promote student-instructor interaction in a large lecture class? One approach is to use a personal response system (or "clickers") in which students press a button on a hand-held remote control device corresponding to their answer to a multiple choice question projected on a screen, then see the class distribution of answers on a screen, and discuss the thinking that leads to the correct answer. Students scored significantly higher on the course exams in a college-level educational psychology class when they used clickers to answer 2 to 4 questions per lecture (clicker group), as compared to an identical class with in-class questions presented without clickers (no-clicker group, d=0.38) or with no in-class questions (control group, d=0.40). The clicker treatment produced a gain of approximately 1/3 of a grade point over the no-clicker and control groups, which did not differ significantly from each other. Results are consistent with the generative theory of learning, which predicts students in the clicker group are more cognitively engaged during learning. (Contains 2 tables.)