Move your eyes around the image. Does the circular middle section appear to separate from the rest of the figure? Does it appear to be at a different depth and even move?
What's Going On?
The Ouchi Illusion is not well understood. The illusionary motion and perceived depth may arise from the ambiguity formed at the circular contour with the adjoining vertical edges. In one interpretation the vertical bars can be perceived as being on the same depth plane as the horizontal bars -- a strictly two-dimensional image. Your visual sytem can also interpret this image as three-dimensional, where the vertical bars lie on a different depth plane than the horizontal bars. The circular contour therefore acts as an aperture. If the two differently orientated bars are perceived as being on different depth planes, then eye movements can cause induced motion.
The illusionary motion that appears may be due to the circular contour, which causes an ambiguity as far as the terminations of the vertical bars adjoining the contour. When you make eye movements, you may induce motion at the edges of the contour.
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