Blinking keeps our eyes moist – but we actually blink way more often than we need to if that was the only reason. Scientists at the University of Rochester have now found that the involuntary action plays a bigger role than we thought, helping us process visual information.
It’s long been thought that the main reason we blink is to clear dust and debris out of our eyes, to prevent infection and injury. That’s obviously important, but our innate response seems a bit excessive: on average humans blink up to 20 times every minute, or almost 20,000 times a day. Although each blink only lasts between 0.1 and 0.4 seconds, that adds up to around 8% of our waking hours spent walking around with our eyes closed. The brain has to work harder to counteract those constant interruptions to visual processing, so it just doesn’t seem like a risk evolution would take without getting some other benefit in return.
So for the new study, the Rochester researchers set out to investigate what that benefit might be. The team tracked eye movements in human observers as they watched various stimuli, like patterns with different levels of detail. The researchers coupled this with computer models and spectral analysis to figure out how blinking affects vision and the way the brain processes it.
The scientists found that the rapid motion of the eyelid during a blink changes the light patterns that stimulate the retina, sending a different type of visual signal to the brain than the kind sent when our eyes are open and focused on something. In practice, blinking helps people take in the “big picture” of a scene, and notice large-scale, slowly changing patterns.
“We show that human observers benefit from blink transients as predicted from the information conveyed by these transients,” said Bin Yang, first author of the study. “Thus, contrary to common assumption, blinks improve – rather than disrupt – visual processing, amply compensating for the loss in stimulus exposure.”
Eye movements are already thought to improve visual processing – now it looks like blinking is another cog in the machine, rather than just an inconvenience.
The research was published in the journal PNAS.
Source: University of Rochester via Eurekalert