I thought the reason for this effect was nothing more than our strong tendency to pay attention to the depth perception cues, which in turn draws you to mistakenly (for the "effect" in this particular case) seeing the white portions of the image as figure rather than ground. If you block out the shading on the white figures (which blurring your vision a bit by tugging eyelids or looking at an angle probably does), then you can see the black regions as figure.
Linda Walsh University of Northern Iowa [EMAIL PROTECTED]
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