Scientists have come up with a new optical illusion that makes you think that a dark 'black hole' is rapidly expanding, or that you are entering a tunnel. Researchers believe the image literally tricks the brain into thinking that the observer is moving into a darkened space, like a cave or tunnel.
Stare at the illusion, above, and most people will see the dark elliptical region expanding outward for a couple of seconds, which is why the design has been nicknamed the 'expanding hole'. In a new study, researchers found 86% of the 50 participants who looked at the optical illusion reported seeing the expanding darkness. The team suspects that the illusion plays on the brain's perception of changing light levels.
Lead researcher Bruno Laeng, a psychologist at the University of Oslo in Norway, said: "The expanding hole is a highly dynamic illusion. The illusion tricks the mind into seeing a change in brightness that isn't really there, as if the observer were heading forward into a hole or tunnel."
"The illusion of the expanding hole prompts a corresponding dilation of the pupil, as it would happen if darkness really increased," Mr Laeng said. "This shows that the pupil reacts to how we perceive light, even if this light is imaginary."
The researchers also tried versions of the illusions where the color of the ellipses had been changed. When this happened, the illusion's expanding effect was reduced and so was the observer's pupil dilations. When the colors were inverted (placing white ellipses on a black background), the observers' pupils contracted, instead of expanding, as if they were moving toward a bright light.
