Another new optical illusion has emerged that is powerful enough to fool our eyes and brains. Strangely, only 80 percent of people seem to be able to fully experience the illusion, and researchers aren’t entirely sure why.
The optical illusion consists of a white background, black dots with a hazy black hole in the centre. If you look at the black spot, you can see that the shape is enlarged. Psychologists from the University of Oslo in Norway, reporting their work in the journal Frontiers in Human Neuroscience, said that the “expanding hole” illusion is so good at tricking our brains that it makes many people see an enlargement that doesn’t actually exist. Moreover, our pupils dilate, just as when entering a truly dark space. Conversely, when the “hole” is colored rather than black, our pupils shrink as if they are adapting to brighter light.
Professor in the Department of Psychology at the University of Oslo and lead author of the study, Bruno Laeng, said in a statement: “The expanding hole is an extremely dynamic illusion: the circular blot or shadow gradient of the central black hole, as if the observer were moving towards a hole or tunnel. it gives the impression of a distinct optical flow,” he says. Our brain, believing this, causes our pupils to dilate.
Two in 10 are blind
As part of their study, the team showed 50 people with normal vision the “widening hole” image and asked them to rate how strongly they perceived the illusion. Meanwhile, the researchers measured eye movements and the constriction and dilation of the pupils.
Researchers aren’t sure why; but not all participants could perceive the illusion. About 14 percent of respondents did not detect any misleading enlargement when the hole was black. 20 percent did not detect if the hole was colored.
Also, the more strongly individuals rated the intensity of the illusion, the more pupil diameters tended to vary. Those who did not perceive the illusion did not experience any change.
The study sheds light on how the brain and eyes respond to visual stimuli, the researchers say.
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