Friday Illusion: Spot the spinning stingray

Sandrine Ceurstemont, video producer

If you're familiar with the spinning dancer illusion, you'll know that it can be hard to perceive which way an object is rotating. But now a new animation by psychophysiologist Marcel de Heer shows that a single moving image can appear to move in three different ways.

Watch the animation above. How do the stingrays seem to move? According to de Heer, most people will see them swimming up and down, with their tail always away from us. But in the middle of the animation, as the stingrays turn sideways, their true motion is revealed. The one on the left was actually rotating clockwise while the one on the right was turning counterclockwise. Did you see them spinning or swimming?

When we look around us, our visual system assesses the angle of objects to infer the perspective of the scene. But because of the stingrays' shape and two-dimensional striped pattern, it's hard to determine the point of view. This leads to ambiguous motion perception with several plausible alternatives. If you watch this animation for long enough, the stingrays' motion may even flip between the different possibilities.

If you enjoyed this post, check out a turning wheel that seems to jump backwards or take a look at our previous Friday illusions.

Source: http://feeds.newscientist.com/c/749/f/10897/s/17b5c841/l/0L0Snewscientist0N0Cblogs0Cnstv0C20A110C0A80Cfriday0Eillusion0Espot0Ethe0Espinning0Estingray0Bhtml0DDCMP0FOTC0Erss0Gnsref0Fonline0Enews/story01.htm

tribune miley cyrus miley cyrus giant bahamas fop natascha kampusch