Updated:06/03/2022 19:52h
Save
Look at the image above: do you see the black spot as expanding, as if it were some sort of ‘black hole‘ devouring everything around it? Don’t worry. This is what happens to 86% of the population. This has been confirmed by an experiment published in ‘Frontiers in Human Neuroscience’, where they explain the mechanism behind this optical illusion.
The image consists of a large black ellipse surrounded by a dark halo on a white background filled with more but smaller black ellipses. Typically, when a person stares at the image, the dark elliptical region will appear to expand outward for a couple of seconds, which is why the design has been nicknamed an “expanding hole.”
The authors showed this image to 50 people, of which the 86% observed this curious phenomenon.
“The expanding hole is a highly dynamic illusion,” he explains. Bruno Laeng, psychologist at the University of Oslo in Norway. The illusion tricks the mind into seeing a change in brightness that isn’t really there, “as if the observer were heading into a hole or tunnel,” Laeng added.
The illusion hijacks a natural reaction in the brain that predicts when the 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 moving towards that cave or tunnel. When the brain registers a potential change in light intensity, such as entering a cave, it can cause the pupils to constrict or dilate to prepare it in advance for the disruption to come.
The image is so good at fooling the brain that it also makes people’s pupils dilate as if they were actually moving into a darker space. The researchers used special cameras to track observers’ eye movements as they looked at the illusion, and the scientists found that their subjects’ pupils expanded just as the dark region of the illusion seemed to expand in their minds. 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 the darkness actually increased,” Laeng says. This shows that the pupil reacts to how we perceive light, even if this light is imaginary.”
The researchers also exposed viewers to versions of the illusions in which the color of the ellipses had been changed. When this happened, the expansion effect of the illusion was reduced and the observer’s pupil dilations were less noticeable. And when the colors were inverted (placing white ellipses on a black background), the observers’ pupils contracted, rather than expanded, as if they were moving toward a bright light.
However, the authors do not know why a small percentage of people cannot see movement in this optical illusion. The next step will be to try teaching it to other animals to see their reaction and learn more about how these visual systems differ from humans to solve this mystery.
See them
comments