The Spinning Dancer.
If the foot touching the ground is perceived to be the left foot, the dancer appears to be spinning clockwise (if seen from above); if it is taken to be the right foot, then she appears to be spinning counterclockwise.
The Spinning Dancer, also known as the silhouette illusion, is a kinetic, bistable optical illusion resembling a pirouetting female dancer. The illusion, created by web designer Nobuyuki Kayahara,[1][2] involves the apparent direction of motion of the figure. Some observers initially see the figure as spinning clockwise and some counterclockwise. The illusion derives from an inherent ambiguity from the lack of visual cues for depth. There are other optical illusions that originate from the same or similar kind of visual ambiguity. One example is the Necker Cube.
Psychology of visual perception
The illusion has been incorrectly[3] identified as a scientific personality test that supposedly reveals which hemisphere of the brain is dominant in the observer. Under this unproven interpretation, it has been popularly called the Right Brain–Left Brain test,[4] and was widely circulated on the Internet during late 2007 to early 2008.
Bistable perception
Depending on the perception of the observer, the apparent direction of spin may change any number of times, although some observers may have difficulty perceiving a change in motion at all. Some observers may perceive a change in direction more easily by narrowing visual focus to a specific region of the image, such as the spinning foot or the shadow below the dancer and gradually looking upwards. Alternate versions of the image exist in which an additional visual cue facilitates the perception of counterclockwise spin and clockwise spin.
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Versions of the image with an additional visual cue |
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The Spinning Dancer with a visual cue on affixed leg to facilitate the perception of a counterclockwise spin. The visual cue is indicative of the affixed leg being the right leg.
The Spinning Dancer with a visual cue on affixed leg to facilitate the perception of a clockwise spin. The visual cue is indicative of the affixed leg being the left leg.
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Further analysis
A frame-by-frame wide version of the Spinning Dancer, with the purpose of assisting the inquisitive user in analyzing the motion of the dancer. To create this image, the original was split into its 34 constituent frames, and a horizontal panorama was created from those frames.
References
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