You blink every few seconds, meaning your eyes are closed about ten percent of your waking hours. Still, you rarely notice when it happens. With your eyes closing so often, it seems strange that you don’t experience any darkness. After all, you’d certainly notice if someone decided to flicker the lights 20 times a minute.
Blinking has a few different purposes. It clears away particles that land on your eye to keep your peepers clean. Plus, when your eye shuts for that split second, fluids spread over your eyeballs to keep them moist. But those reasons don’t explain why our eyes close so often. After every blink, the brain adjusts our eyes to stay fixed on what we were looking at before, according to a study in Current Biology.
Volunteers in the study stared at a dot on a screen in a dark room. When participants blinked, the dot would shift right about a centimeter. The move was too small for the volunteers to notice, their eyes would realign to center on the dot. After about 35 times, their eyes started predicting the dots’ movements without the participants realizing it. Their brains knew to automatically shift the eyes to the right spot during each blink.
The brain seamlessly combines what we see before and after a blink. If it didn’t, we’d probably see the world as shadowy and jittery, says study co-author David Whitney, a psychology professor at UC Berkley. “We perceive coherence and not transient blindness because the brain connects the dots for us,” he said in a press release.