Friday Illusion: Frozen hearts seem to beat

The hearts in this animation appear to have a pulse but that's only because of the changing background. Created by psychophysiologist Marcel de Heer, the shapes enlarge when a dark area is behind them and compress when a lighter shade moves in.

To investigate the effect, researcher Stuart Anstis of the University of California, San Diego, made his own heart animations. In one variation, where a heart's interior changes in brightness, the shape also appears to beat (see second animation in video).
"The changing gradient across the heart converts the lightening and darkening into apparent expansion and contracting," explains Anstis.

The illusion is caused by the response of retinal cells in our eyes as the boundary changes in brightness. But processing in the visual cortex is also likely to play a role. Simone Gori of the University of Padua previously discovered a similar effect where a gradient affects how we perceive brightness. The smooth pulse induced by a gradual background change is also illustrated in an award-winning illusion where a pattern made up of brains appears to shift.
Were you able to see this illusion? Let us know in the comments section below.

If you enjoyed this effect, watch a similar brain trick where a blurry heart image seems to pulse, or see how a change in contrast can fool your brain.

 http://www.newscientist.com/blogs/nstv/