Ouchi Apparent Motion Illusion

You will have noticed that the pattern in the center is similar to that in the surround but rotated 90 degrees. At first one might think that the important difference is the horizontal spatial frequency. That is to say the width and repetition of the elements in the center and the surround. However, Hine, Cook, and Rogers (1995) reported an experiment where two gratings of identical but rotated spatial frequencies also produced relative movement. They concluded from their experiments that "The illusion arises because there is a failure to integrate two motion signals into a single motion vector which characterizes rigid motion. (p. 3093)

What this means, I think, is that the visual mechanism responsible for rigid motion may be specific to the orientation of the spatial pattern. It would be interesting to see if the illusion still works when the red and green rectangles are equal in luminance. It is almost impossible to demonstrate that here, although I tried. The problem is I don't have a good way to measure luminance on my monitor. Further, I have no way of insuring that the luminances on your monitor will be equal even if I am able to make them equal on my monitor. If the illusion did disappear when the colors are at equal luminance this would have significance for what visual channels are involved to produce the illusion. Hine et al. Vision Research, 35, 3093-3102 (1995)

Ouchi Demo
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