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cafe wall bird in a cage changing illusions disappearing act

  • Move the bricks back and forth and notice the strange distortions in the rectangular brick pattern. If the bricks are aligned as they are in the beginning or if they are organized in a checkerboard pattern, the effect disappears.

  • Change the brightness of the mortar by clicking on the top or bottom of the brightness arrow (you can click and hold to change continuously). Notice when the effect goes away.
The Cafe Wall Illusion was first described by Dr. Richard Gregory. Dr. Gregory is a good friend of the Exploratorium and director of The Exploratory Hands On Science Museum in Bristol, England. Dr. Gregory observed this curious effect in a pattern of tiles on a cafe wall in Bristol and has kindly granted us permission to display his picture of this cafe below. Note that the effect is not visible in the picture due to the small scale of the tiles.

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