Why do we blink more than we need to?

Human blinking is somewhat of a mystery to scientists. While it's well known that eye-blinking is done to lubricate the cornea, these seemingly spontaneous flashes happen at a rate that's greater than what's needed. But now, as new research from Japan suggests, our blinking patterns may serve an unexpected purpose — one that works to release our attention and mentally prepare us for the next task.

Indeed, we blink a lot — about 15 to 20 times every minute. And it all adds up. Studies show that 400 milliseconds of visual time is lost every time we blink, which amounts to a surprising 10 percent of our total viewing time. Given that these blinking rates happen at a level several times higher than what's required for adequate ocular lubrication, scientists have had good reason to suspect that something else is going on — something that's clearly important.

Why do we blink more than we need to?S

A recent study published in the Proceedings of the National Academy of Sciences offers some potential answers. Researchers Tamami Nakano, Shigeru Kitazawa, and colleagues now theorize that eye-blinks are actively involved in the resetting and delivery of attention. But to reach this conclusion, the researchers had to rely on two very important tools: An fMRI scanner and a Mr. Bean video.

For the experiment, Nakano et al recruited several volunteers who were asked to watch Mr. Bean episodes while hooked up to an fMRI scanner. Previous studies by the same researchers showed that human eye-blinks become synchronized while watching these videos (i.e. eyeblinks tend to occur at implicit breakpoints) — so they had good reason to continue their research; it was clear that something was happening from a neurological perspective.

During the Mr. Bean episodes, the scientists observed that the participants were spontaneously blinking an average of 17.4 times per minute. But while the blinking was happening, there was observable activity occurring in two competing anatomical brain networks responsible for attention.

Specifically, they noticed spikes of mental activity in areas related to the default network — an area of the brain that allows us to enter into a kind of 'idling' mode when we're in a state of wakeful rest (as opposed to focused attention). And at the same time, they noticed decreased cortical activity in the dorsal attention network (a sensory orienting system that helps us know where we should focus our attention).

Consequently, the researchers hypothesize that eye-blinks — because they activate the default network — are a way for us to take a super-quick mental break before renewing our attention on a new task or activity — and they tend to occur at logical transition points (e.g. the end of a scene, or the end of a sentence...like right now).

They speculate that this serves an important cognitive function, what gives us an increased capacity for focused attention after the cognitive reset.

The entire study can be read at Proceedings of the National Academy of Sciences.

H/t: Smithsonian.

Image: Nejron Photo/Shutterstock.