EDIT image deleted; copyright.

spins one way, then if you look to the side and squint a bit she spins the other!

 

Apparently its got something to do with right/left hemisphere stuff, but can anyone explain?

 

(image not working so link http://visualfunhouse.com/animations/spinning-silhouette-optical-illusion.htmlhttp://visualfunhouse.com/animations/spinning-silhouette-optical-illusion.html

Edited December 4, 200916 yr by randomc
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I believe it has to do with an ambiguous horizon line. If she is spinning clockwise her out-reached hand dips down in front. If she is spinning counter-clockwise her hand dips down behind. Both perspectives are accurate enough for the brain to decide it's correctly seeing a spinning woman, but since it can't be both it focus on the first one it matches. Break that focus, it may match on the other.

Edited December 4, 200916 yr by padren

its strange that for me its always spinning clockwise initially. I suppose that would be because pattern recognition is located in one side of the brain? Or maybe its just my astigmatism:D

I seem to be able to make it appear to spin either way at will. Very weird.

Hmm - I see her clearly with her left leg in the air spinning anticlockwise. My wife say's it's her right leg in the air and she is spinning clockwise. She has an astignatism also.

at first, only counter-clockwise, then as my eyes moved vertically it would change back and forth

I dunno. I observe a change in the direction of rotation looking only at her foot.