The Spinning Dancer
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The Spinning Dancer, also known as the silhouette illusion, is a kinetic, bistable optical illusion resembling a pirouetting female dancer. The illusion involves the apparent direction of motion of the figure. Some observers see the figure as spinning clockwise and some counter-clockwise. The illusion has been falsely considered by many to be a scientific personality test[1] that supposedly reveals which hemisphere of the brain is dominant in the observer. Under this interpretation it has been popularly called the Right Brain–Left Brain test.[2]
An observer who sees only one direction of motion in the image may be able to see the other direction by focusing only on the spinning foot or on the shadow below the dancer or by looking indirectly at the image and turning your neck towards and away from the image. There are non-sillhouette versions of the image in which additional visual cues facilitate the perception of counter-clockwise motion and clockwise motion.
The difference between the 2 view points is, as with many other illusions, c.f. Necker Cube , where the viewer believes he is viewing the action from: When the dancer appears to spin anti-clockwise, the viewer appears to be looking slightly upwards, as though through a glass floor about 2 feet above eye level. When the direction is reversed and the dancer spins clockwise the viewer appears to be slightly above the dancer, as though standing on a very low platform
