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Celebrities are generally an attractive bunch — that is, unless you view their faces paired side by side and cycled through in quick succession. In a new optical illusion unveiled May 14 at a meeting of the Vision Sciences Society in Florida, celebrities' faces appear grotesquely distorted — though their photographs aren't altered at all — when viewed in a particular manner.

The optical illusion , which works on non-celebs' faces, too, was discovered by accident by Jason Tangen, Sean Murphy and Matthew Thompson of the University of Queensland in Australia. Dubbed the "flashed face distortion effect," it won second prize in the eighth annual Best Illusions of the Year contest, held each year at the Vision Sciences Society meeting.

In the researchers' video, pairs of different faces are flashed in sequence, with empty space separating the left and right slideshows of faces. If you stare at the individual faces, they appear normal, but if you fix your eyes on the space between the faces, they suddenly become hideously deformed.

Cognitive scientists can't yet fully explain the newly discovered distortion effect, though it may result from the way our vision becomes normalized to the features of a face, causing the face that immediately follows it to appear abnormal by contrast.

"By aligning the faces at the eyes and presenting them quickly, it becomes much easier to compare them, so the differences between the faces are more extreme," the researchers explain on their lab website. "If someone has a large jaw, [the effect makes it appear] almost ogre-like. If they have an especially large forehead, then it looks particularly bulbous. We're conducting several experiments right now to figure out exactly what's causing this effect."

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