Expanding Hole Illusion Tricks the Brain and Eyes, Causing Real Pupil Reflexes
A Mind-Bending Illusion That Fools the Eyes — and the Brain
Take a closer look at the image above. Does the central black area seem to expand, almost like you're falling into a tunnel or entering a dark space? If so, you're not alone. According to a groundbreaking study, around 86% of people experience this sensation when viewing what researchers are calling the "expanding hole illusion" — a newly documented optical phenomenon.
The Science Behind the Expanding Hole Illusion
Dr. Bruno Laeng, a professor at the University of Oslo’s Department of Psychology and lead author of the study, explains:
“The expanding hole illusion is highly dynamic. The dark gradient in the center creates a powerful impression of motion — as though you’re moving forward into a tunnel.”
This illusion isn't just a quirky visual trick. It's now the subject of scientific research because of its ability to provoke genuine physiological responses. The study, published in Frontiers in Human Neuroscience, demonstrates that the illusion can trigger a pupil dilation reflex — the same reaction your eyes would have if you were actually entering a darker environment.
How Illusions Impact Our Perception
Unlike mechanical devices like photometers, which measure light in a purely physical way, the human visual system interprets light through complex cognitive processes. Optical illusions like the expanding hole reveal just how much perception — not just reality — shapes how we see the world.
Laeng and his team found that even when no real change in lighting occurs, the perception of increased darkness from the black “hole” can prompt the pupils to dilate, allowing more light into the eyes. This reflex, usually tied to actual light levels, appears to respond to perceived or even imagined darkness.
“The pupil reacts to how we perceive light — not necessarily to the real light entering the eye,” said Laeng. “This shows that perception can override physical reality when it comes to reflexive bodily responses.”
Black Hole vs. Colored Variants
Researchers tested several versions of the illusion, changing the central color to blue, red, green, white, and more. They presented these images to 50 participants with normal vision, measuring their eye movements and changes in pupil diameter.
Key findings included:
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The illusion was most powerful when the central hole was black.
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14% of participants didn't experience the illusion with a black hole, while 20% didn’t with colored holes.
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Black holes triggered noticeable pupil dilation, whereas colored holes often caused the opposite — pupil constriction.
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The stronger someone perceived the illusion, the more significant their pupil reflex was.
Not Everyone Is Affected
A small percentage of people seem immune to the illusion. Scientists still don’t fully understand why. It’s also unclear whether other animals — like vertebrates or octopuses with complex eyes — would perceive the same illusion.
“Our results suggest the eye is not just a passive receptor of light, but an active participant in how we interpret our surroundings,” Laeng noted. “Future research may uncover other physiological responses to illusions that help explain how perception shapes bodily behavior.”
Conclusion:
The expanding hole illusion isn't just a visual oddity — it’s a compelling window into how our brains and bodies respond to imagined experiences as if they were real. As optical illusions continue to reveal the fascinating mechanics of human perception, they remind us that what we see is often as much about the brain as it is about the eyes.
Here you can read whole article :
https://www.frontiersin.org/journals/human-neuroscience/articles/10.3389/fnhum.2022.877249/full?utm_source=fweb&utm_medium=nblog&utm_campaign=ba-sci-nhumn-expanding-hole-illusion-tricks-eye-pupils-into-dilating