In the illusion , a small pink object can be seen moving back and forth in front of three types of background. When observers track the pink target moving back and forth in front of a background consisting of dynamic noise, they report the percept of a drifting background. The direction of this drift is opposite to that of the small pink object, even though the background in fact does not move into a particular direction. This illusory motion arises for a static gray Gaussian background, but is actually much stronger when the background is dynamic random noise. However, the illusion does not occur when the background consists of static random noise.
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(© 2007 Masaharu Kato)