For a motivating and baffling experience, try this investigation of perceptual illusions and their causes. It allows students to observe, analyze, and compare a variety of optical illusions, and also to create their own optical illusions with pencil, paint, and paper. Their results will lead them to make conclusions about visual perception and to generalize about broader aspects of sensory perception. In the process, students will discover that shapes play a major role in illusions and that it can be difficult for one individual to simultaneously maintain two different perspectives.