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Background

The motion aftereffect, first discussed by Aristotle, is also known as waterfall illusion (Verstraten, 1996; Wade, 1996). An aftereffect is a sensory experience that occurs after prolonged sensory exposure to one stimulus that alters how we experience other stimuli after the prolonged exposure. Another way to observe this illusion at home is to watch the credits at the end of a movie without taking your eyes off of the television screen. After watching the credits for two minutes, have a friend or family member hit the pause button. You will see an illusion of the movie credits moving up the screen even though you know the video is now stopped. Aristotle observed this by looking at nonmoving surfaces after watching the downward motion of waterfalls.