• Updated
02 February 2022

"Best illusion of the year" contest: Dawei Bai and Brent Strickland's "Double ring illusion" won 3rd place

A visual illusion recently discovered by Dawei Bai, PhD student at the Institut Jean Nicod (IJN) and Brent Strickland, CNRS researcher at the IJN, came in 3rd place in the ‘Best illusion of the year competition created by the Neural Correlate Society

A contest to promote illusion and perception science, as well as research discoveries throughout the world

best illusion

The Best Illusion of the Year Contest was created by the Neural Correlate Society (NCS). The NCS  promotes scientific research into the neural correlates of perception and cognition and seeks to communicate these discoveries to the public, in order to contribute to the advancement of medicine and general awareness.

This online event celebrates the ingenuity and creativity of the world's leading illusion research community. Contestants from around the world submit unpublished illusions (unpublished or published no earlier than 2015), and an international panel of judges evaluates and ranks them in a TOP TEN. Internet users around the world vote for their favorite illusions from the ten finalists. The top three winners receive a prize.

The « Double ring illusion »

When two bistable rings are presented separately, they appear to move in unstable 360° rotations. However, if the same rings partially overlap, they now appear to move in stable 180° rotations, bouncing back and forth – as if they avoid passing through each other. Remarkably, when one ring is holed, in a way that the other ring can pass through the holes, the unstable 360° percept is restored. In all three cases, the rings undergo the exact same motion, but our visual system interprets the stimuli differently depending on whether the rings can traverse each other.

This illusion shows that the visual system would be sensitive to the physical constraint of "solidity": solid objects cannot pass through each other. More precisely, when looking at ambiguous stimuli - that is, compatible with several interpretations - our visual system would use solidity to compute motion, rejecting interpretations where the solidity constraint is transgressed. 

The "Best illusion of the year" award is well known in the field of visual perception and on social networks. The visual illusion "Double ring illusion" has already obtained 74K views on youtube.