Persistence of Vision

If you look at an object fixedly, your eyes and mind will try to blank it out. One of the classic examples is the color-opposites of the US flag. After staring at the yellow, green and black image for 30 seconds or so, then switching to a white field, you'll see the image briefly as Red, White and Blue. Now I'm guessing (and it is only a guess) that this is evolutionarily beneficial in that it draws our attention away from things that are static (unthreatening) and to things that are changing (potentially threatening). Images that move in a repetitive manner can also give rise to this. With color, there might be a chemical basis in the eye; with movement, it seems to me it must be a perceptual (mind) phenomenon, so I'm not sure the two aspects of this are really considered the same.

I first saw this as a cut out from Omni Magazine in the late '70's. You took the image and put it on a turntable, and stared at the spindle for 30 seconds to a minute. Yeah, ancient technology, but it still works even in our electronic era. (When the spirals quit spiraling, look at something that has details, not a blank, uncluttered area) Whooooaaaaa! Far out, Dude!