Nearly every introductory physics or chemistry course includes live lecture demonstrations, which can range from simple illustrations of a pendulum to elaborate productions with specialized apparatus and highly trained demonstrators. Students and instructors often consider "demos" to be among the highlights of these classes. Yet, in some…

Previous research suggests that students; prior knowledge can interfere with how they observe and remember lecture demonstrations. We measured students' prior knowledge in introductory mechanics and electricity and magnetism at two large universities. Students were then asked to predict the outcome of lecture demonstrations. We compare…