Friday Illusion: Bend a shape with your mind

Caitlin Stier, video intern

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The shapes in this video seem to get distorted, but it's all in your mind. The illusion, created by Cornelia Ferm?ller of the University of Maryland, is an animated version of a classic effect called the Luckiesh pattern, where a shape can look skewed when surrounded by radiating lines. By making the linear pattern move, the distortion changes position.

According to Ferm?ller, the bending is caused by imperfections in our visual system when we compute the angle between the pairs of lines. Our brain approximates the angle with a systematic error, for example an angle of 45 degrees may be over or underestimated by a degree. "Using this noisy measurement, the visual system computes wrong intersection points between the background lines and the shape, which leads to a perceived distortion," says Ferm?ller.

Ferm?ller is using statistics to better understand the misinterpretation which also occurs in computer processing. The approach could explain illusions that involve basic estimation biases rather than higher level processing in the brain.

You can also play around with an interactive version of the illusion here, by tweaking intersection estimates and controlling the speed and angle of the pattern.

For more brain tricks, see how a shifty shadow can alter an object's path or explore our previous Friday Illusions.?

Journal reference: Vision Research, DOI: 10.1016/j.visres.2003.09.038

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Click here to see our illusion challenge

Last week, we showed you a house that seems to collapse and asked you to identify two illusions we've previously featured that exploit the same effect. Congratulations to Nat R. who was the first person to post two correct links.?Deceptive dice and 3D painting flips perspective are two examples of the same illusion, where our brain confuses concave and convex scenes. The misinterpretation is based on our visual system assuming the most common arrangement of the visual information. The hollow mask illusion is another common example of the effect.? ??

Source: http://feeds.newscientist.com/c/749/f/10897/s/18d1a23b/l/0L0Snewscientist0N0Cblogs0Cnstv0C20A110C0A90Cfriday0Eillusion0Eangled0Epattern0Ebends0Ea0Ediamond0Bhtml0DDCMP0FOTC0Erss0Gnsref0Fonline0Enews/story01.htm

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