Today I learned that scientists study optical illusions. I always thought they were just for fun. A team of psychologists studied variations of this “expanding hole” illusion to determine what effects it has on the human body. It turns out that more than just our minds are tricked.
I am one of the 86% of people that can see this illusion. The black oval at the center seems to gape and the white background rolls into the hole as it expands. As with other optical illusions, sometimes it stops moving. But shifting my eyes or looking away and then back starts the process all over again.
The scientists tested the black center on various colored backgrounds, as seen below. They measured the pupil size of their test subjects as they looked at each illusion. Pupils dilated (got larger) when viewing these illusions with a black center. The researchers think it’s part of the body’s response to our brains thinking we’re entering a dark place as the black hole expands.
In order to test this theory, the scientists also measured the eye’s response to versions of the illusion where the center oval was either colorful or white, as shown below. Our minds are still tricked into thinking that the center is widening. But instead of a dark hole, we’re entering a bright area. Sure enough, most people’s pupils constricted instead of widened.
The colorful or white centers in the above graphic trick my mind to various degrees. Especially when looking at them all lined up, it’s more of a pulsing sensation than the black-centered versions. I didn’t measure my pupil size, no need to get scientific. But since people are studying this topic, when will science get to the important questions like: can otters see optical illusions? And what about cats?
Melissa is Nerdist’s science & technology staff writer. She also moderates “science of” panels at conventions and co-hosts Star Warsologies, a podcast about science and Star Wars. Follow her on Twitter @melissatruth.