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Illusions contest: Illusion-defying contours

It's all out in the open, so why do we see what isn't there?
[video_player id=鈥漃GQs4b3L鈥漖Video: Illusory contours
Those contours aren't real
Those contours aren鈥檛 real
(Image: Bart Anderson)

An animation that appears to have illusory contours was awarded second place in the contest. Created by at the University of Sydney, Australia, it鈥檚 made up of four circles and four dots that move back and forth over the outline of a rectangle. Contours connecting the moving dots in the middle seem to appear, creating a diamond that sometimes seems to morph into a more rounded shape as it stretches out.

Contours appear in . They can normally be explained by the way fragments of objects are arranged: a well-known shape without visible contours is inferred because our brains choose the most likely configuration based on the visual information.

But this explanation doesn鈥檛 seem to apply to Anderson鈥檚 illusion. The moving circles and dots are never partially obscured, so the brain shouldn鈥檛 have to infer another shape. 鈥淭his illusion can鈥檛 be understood with any known mechanism that has been proposed to explain the formation of illusory contours,鈥 says Anderson.

See more: Don鈥檛 believe your eyes: This year鈥檚 best illusions

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