This illusion of the “expanding hole” can trick your brain into thinking you’re entering a cave or tunnel. (Image credit: Frontiers in Human Neuroscience) (opens in a new tab)
A new optical illusion makes most people think that a dark region of “black hole” in the center of a stationary image is rapidly expanding, as if the observer is moving toward it. Researchers now suspect that the image literally fools the brain into thinking that the observer is moving into a darkened space, such as a cave or tunnel.
The illusion consists of a large black ellipse surrounded by a dark halo on a white background full of smaller black ellipses. Normally, when a person looks at the image, the dark elliptical region appears to expand outward for a couple of seconds, which is why the design has been dubbed the “expanding hole.”
In a new study, researchers found that 86% of the 50 participants who looked at the optical illusion reported seeing darkness expand. The team suspects that the illusion plays with the brain’s perception of changes in light levels.
“The expanding hole is a highly dynamic illusion,” said lead researcher Bruno Laeng, a psychologist at the University of Oslo in Norway, in a statement. Illusion deceives the mind into seeing a change in brightness that is not really there, “as if the observer is heading for a hole or a tunnel,” Laeng added.
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Illusion hijacks a natural reaction in the brain that predicts when light is about to change, the researchers said. The dark region in the center of the image mimics the entrance to a cave or tunnel, and the pattern around it gives the viewer the impression that they are moving toward that cave or tunnel. When the brain records a potential change in light intensity, such as entering a cave, it can cause the pupils to contract or dilate to prepare you for the next interruption in advance.
Illusion is so good at fooling the brain that it also causes people’s pupils to dilate as if they were actually moving into a darker space. Researchers used special cameras to track the eye movements of observers as they watched the illusion, and the scientists found that the subjects’ subjects were expanding just as the dark region of the illusion seemed to expand. se in his mind. Those who saw a larger dark hole showed more dilation than those who saw a less marked “black hole,” the researchers said.
“The illusion of the expanding hole causes a corresponding dilation of the pupil, as would happen if it actually increased the darkness,” Laeng said. This shows that “the student reacts to how we perceive light, even if it is imaginary.”
Researchers also exposed observers to versions of illusions where the color of the ellipses had changed. When this happened, the illusion-expanding effect diminished and the dilations of the observer’s pupil became less noticeable. And when the colors were reversed (placing white ellipses on a black background), the pupils of the observers contracted, instead of expanding, as if they were advancing toward a bright light. .
Researchers have no idea why some people looking at the expanding hole cannot see the dark region in motion. The team hopes to test the excitement in other animals and see if they can learn more about how these visual systems differ from humans, to solve this mystery.
The new study was published online May 30 in the journal Frontiers in human neuroscience (opens in a new tab).
Originally published in Live Science.