an illusion of depth that occurs when a swinging pendulum is viewed by one eye normally, but through a dimming filter by the other eye. The difference in the timing of the visual signals created by this situation is interpreted by the brain as binocular disparity, and the pendulum appears to be traveling in an ellipse rather than back and forth. Also called Pulfrich phenomenon. Compare Mach–Dvorak stereoillusion. [Carl Pulfrich (1858–1927), German scientist]