Watch this circle jump to life as soon as you tilt your head, and move your eyes across 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 or even move? So what is going on around here? Well, Ouchi Illusion is not well understood. In one interpretation the vertical lines can be perceived as being on the same depth plane as the horizontal ones – a strictly two-dimensional image. Your visual sytem can interpret this image as 3D, where the vertical lines lie on a different depth plane than the horizontal ones. 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. Thanks goes to Brian for discovering and submitting this optical illusion by prof. Akiyoshi Kitaoka.