FUN: Vision Twisters

Science  23 Feb 2001:
Vol. 291, Issue 5508, pp. 1453a
DOI: 10.1126/science.291.5508.1453a

For those who can't resist the weird and unsettling world of optical illusions, a growing Web site developed by cognitive neuroscientist Al Seckel is a must see. Seckel, who works in the lab of Caltech vision scientist Shinsuke Shimojo, has stocked his pages with familiar fare—such as Escher prints and the young girl/old woman picture—and unusual and newly concocted illusions. One is an animation of a ball that appears to roll, bounce, or fall across a grid depending on how its shadow is changed. Another uses a picture of Margaret Thatcher to show how someone can be recognizable even with their head upside-down, as long as facial features are right side up—while recognition is impossible if just the features are upside-down.

A newly completed perceptual twister is the bronze sculpture depicted here, an elaboration of the “impossible fork” concept, which looks completely different depending on the angle from which it is viewed.

P.S. If you go to neuro.caltech.edu/∼lshams/demo.html, you can see a demo of sound-induced illusory flashing produced by Shimojo's lab. It seems that when a single flash is accompanied by two beeps, the single flash is perceived as two flashes.

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