Go ahead, give the video below a spin—pun fully intended. Focus on the white dot in the middle.
Did the dots appear to stop changing color when they began to rotate? If so, give the animation another look: the dots change color throughout, but their spinning motion somehow suppresses the viewer's ability to detect those changes.
The illusion, titled "Silencing awareness of change by background motion," won top honors May 9 at the 2011 Best Illusion of the Year contest in Naples, Fla. The event, which is in its seventh year, is an offshoot of the annual Vision Sciences Society meeting, also in Naples. Jordan Suchow, a Harvard University graduate student, and George Alvarez, an assistant professor in Harvard's psychology department, created the winning entry.
The contest draws all manner of illusory entries. The 2011 first and second runners-up were also animations, one an illusion of contrast and one an illusion of visual aftereffects induced by motion, respectively. (See all 10 finalists here.) Last year's winner, on the other hand, was a video of an actual physical object that seemed to defy gravity—balls rolled right up inclined ramps as if pulled by magnets.