Optical Illusion Spinning Dancer - Ambiguous Image

Thursday, September 18, 2008

If you see the dancer spinning clockwise, the story goes, you are using more of your right brain, and if you see it moving counterclockwise, you are more of a left-brained person.

Clockwise or counterclockwise?But while the dancer does indeed reflect the brain savvy of its creator, Japanese Web designer Nobuyuki Kayahara, it is not a brain test. Instead, it is simply an optical illusion called a reversible, or ambiguous, image. Images like this one have been long studied by scientists to learn more about how vision works.





The silhouette image of the spinning dancer doesn’t have any depth cues. As a result, your eyes will sometimes see the dancer standing on her left leg and spinning to the right. And sometimes they will perceive her as standing on her right leg and spinning to the left. Most people, if they stare at the image long enough, will eventually see her turn both ways.

Perhaps the most-studied reversible image is the Necker cube, which looks like the wire-frame of a cube. The picture also lacks depth cues, so sometimes the face of the cube appears on the lower left, but sometimes it jumps to the back and the face of the cube shifts. A moving rotating Necker cube can be seen here.

“What’s happening here to cause the flip is something happening entirely within the visual system,’’ said Thomas C. Toppino, chair of the department of psychology at Villanova University. “If we can understand why it is these figures reverse then we’re in a position to understand something pretty fundamental to how the visual system contributes to the conscious experience.’’

Sometimes, a person will stare at an image and it will never reverse. Dr. Toppino advises staring at one part of the image, such as the foot, and most of the time it will eventually flip. I tried this several times, but it never flipped. Dr. Toppino says in people who can’t see the reversal, it may be that one underlying neural structure is more dominant, but once someone finally manages to see the flip, it will start to happen more often.

I did finally see the dancer flip, but it was only after using a sort of cheat sheet that draws a line on the dancer’s standing leg. To see the lined image moving clockwise, click here. To see it move counterclockwise, click here.