Posted: Jul 21, 2018 8:53 am
by Hermit
One of my favourite optical trick is the ballerina. Her rotational direction keeps flipping every ten seconds or so, but not for everybody. It's still a trick, though, for there is no objective pointer as to whether she rotates clockwise or counter-clockwise. There is very little we see "objectively". Somewhere along the line the brain interprets the visual input and and often enough it's reduced to guessing - wrongly.

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