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A brand new optical illusion tricks most people into believing that a dark “black hole” region in the center of a stationary image is rapidly expanding, as if the observer is heading towards it. Researchers now suspect that the image literally tricks the brain into thinking the viewer is moving through a dark space, such as a cave or tunnel.
The illusion consists of a large black ellipse surrounded by a dark halo on a white background filled with smaller black ellipses. Typically, when a person looks at the image, the dark elliptical region appears to expand outward for a few seconds, which is why the design has been dubbed the “expanding hole”.
In a new study, researchers found that 86% of 50 participants who watched the optical illusion said they saw the darkness spreading. The team suspects that the illusion plays on the brain’s perception of changing light levels.
“The expanding hole is a highly dynamic illusion,” lead researcher Bruno Laeng, a psychologist at the University of Oslo in Norway, said in a statement. The illusion tricks the mind into seeing a change in brightness that isn’t really there, “as if the viewer is heading toward a hole or a tunnel,” Laeng added.
Related: A new kind of optical illusion tricks the brain into seeing dazzling rays
The 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 surrounding pattern gives the viewer the impression that they are heading towards that cave or tunnel. When the brain registers a potential change in light intensity, such as entering a cave, it can trigger the pupils to constrict or dilate to prepare you in advance for the upcoming disturbance.
The illusion is so good at tricking the brain that it also causes people’s pupils to dilate as if they were actually moving through a darker space. The researchers used special cameras to track the observers’ eye movements as they looked at the illusion, and the scientists found that their subjects’ pupils dilated just as the dark region of the illusion seemed to dilate in their eyes. spirit. Those who saw a larger black hole showed more dilation than those who saw a less austere “black hole,” the researchers said.
“The expanding hole illusion causes a corresponding dilation of the pupil, as would occur if the darkness really increased,” Laeng said. This shows that “the pupil reacts to the way we perceive light, even if this light is imaginary”.
The researchers also exposed the observers to versions of the illusions where the color of the ellipses had been altered. When this happened, the expansion effect of the illusion was reduced and dilations of the observer’s pupil were less noticeable. And when the colors were inverted (by placing white ellipses on a black background), the observers’ pupils contracted, instead of widening, as if pointing at a bright light.
Researchers don’t know why some people looking at the expanding hole are unable to see the dark region move. The team hopes to test the illusion on other animals and see if they can learn more about how these visual systems differ from that of humans, to solve this mystery.
The new study was published online May 30 in the journal Frontiers of Human Neuroscience (opens in a new tab).
Originally posted on Live Science.