Occluded Wheel Illusion from Interactive Mathematics Miscellany and Puzzles

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Occluded Wheel Illusion

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Copyright © 1996-2010 Alexander Bogomolny

The applet shows a wheel that may rotate and a picket fence that may move horizontally. Depending on several parameters, the eye may indeed see the wheel or a spider like design. This is known as Roget's "Palisade" Illusion. I would think that Poggendorff's illusion lies at the root of the present one. However, the latter does not appear if only the fence or only the fence move. When draw thickly, the spokes seem (to me) to acquire a bluish cue.

Copyright © 1996-2010 Alexander Bogomolny

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