Random-Dot Motion Displaces Ehrenstein Illusion

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Abstract
When a random-dot screen is used as a background for Ehrenstein figures, brightness enhancement is replaced by a change of grain and structure. Dots in the illusory area appear less densely packed and may be perceived as concentrically organized. When the screen is moved with respect to the Ehrenstein figures, the illusory patches seem to move in the same direction and out of the inducing area while maintaining their characteristic organization. It is proposed that neurophysiological mechanisms with different persistencies are involved in producing the observed phenomenon. It is also suggested that random dots moving along the same open path are combined into a figure, whereas dots crossing the lines of the pattern remain unstructured and serve as a ground against which the displacement is seen.