Scientists found a trippy illusion that triggers pupil dilation (in most people)

Approximately 86% of the people who see the above hero image will experience involuntary pupil dilation.

No, that’s not a GIF and the image isn’t manipulating your monitor’s refresh rate. If you’re among those who perceive the illusion, your brain is actually being tricked into believing you’re entering a darkened space.

Dubbed ‘the expanding hole’ illusion, the image is responsible for a recently-discovered physiological phenomena that has scientists rethinking how the human eye works.

Bruno Laeng, a psychology professor at the Univesity of Oslo, and one of the authors of a research paper studying the illusion discussed the work in a press release:

“Here we show based on the new ‘expanding hole’ illusion that that the pupil reacts to how we perceive light—even if this ‘light’ is imaginary like in the illusion—and not just to the amount of light energy that actually enters the eye. The illusion of the expanding hole prompts a corresponding dilation of the pupil, as it would happen if darkness really increased.”

What’s most interesting here is that it was previously believed that the human eye only reacts to actual changes in light, not perceived ones.

But, according to Laeng, their work demonstrates otherwise:

“Our results show that pupils’ dilation or contraction reflex is not a closed-loop mechanism, like a photocell opening a door, impervious to any other information than the actual amount of light stimulating the photoreceptor. Rather, the eye adjusts to perceived and even imagined light, not simply to physical energy.”

As to what this means? For starters, it signifies that we’re not done learning about how the human brain works. That may seem like a no-brainer (pun fully intended), but it’s nice to be reminded of it in such a delightfully visceral way. Unless you can’t see what I’m talking about, in which case… just imagine that it looks like you’re floating into a dark tunnel.

My wife Nikki and I are definitely in the 86% who perceive the illusion. What about you? Let us know on Twitter.


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