We blink every few seconds, a simple, automatic action. It’s commonly thought of blinking as a way to moisten our eyes, but a new study from researchers at the University of Rochester reveals a more complex role: blinking also helps your brain process visual information more efficiently. Proceedings of the National Academy of SciencesThis study sheds light on how briefly closing your eyes contributes to vision.
Humans spend about 3-8 percent of their waking time blinking with their eyes closed. Given that blinking temporarily blocks vision, you might wonder why we blink so frequently. Traditional explanations emphasize that blinking helps keep the eyes moist and prevents them from drying out.
But blinking frequency suggests that it may have additional functions beyond lubrication. Researchers Bin Yang, Janice Intoy, and Michelle Ruch wanted to explore these potential functions, specifically how blinking affects visual processing in the brain.
The study involved 12 men and women with an average age of 22, all of whom had normal vision. Participants were compensated for their time and were blinded to the specific aims of the study to ensure unbiased results. The researchers conducted the study in a controlled laboratory environment and used advanced eye-tracking technology to precisely monitor participants’ eye movements.
Participants were tasked with viewing visual stimuli consisting of a grid pattern, which is made up of alternating stripes with different spatial frequencies. Spatial frequency refers to the level of detail in the pattern, with higher frequencies representing greater detail. These stimuli were presented on a high-resolution monitor, and participants had to identify whether the grid pattern was tilted clockwise or counterclockwise.
The experimental design included two main conditions to isolate the effect of blinking on visual processing. In the “blink with stimulus” condition, participants were instructed to blink during the presentation of the visual stimulus. In contrast, in the “blink without stimulus” condition, participants were instructed to blink before the stimulus appeared. The researchers controlled for the timing and condition of the blinks to ensure that any observed effects were due to the act of blinking itself and not other variables.
Eye movements were tracked using a dual Purkinje image eye tracker, providing high-resolution data on participants’ eye position and movement. This technology allowed the researchers to ensure that participants were following instructions and that their blinks and eye movements were accurately recorded. Each experimental session consisted of multiple trials, and data was collected and analyzed to compare performance across the two conditions.
The researchers found that when participants blinked during the presentation of a visual stimulus, their ability to identify the orientation of the gratings was significantly improved compared to when they blinked before the stimulus appeared. This improvement was evident in both the accuracy of the participants’ responses and their sensitivity to visual details, as measured by a standard discrimination sensitivity index.
The researchers hypothesized that this improvement was due to a change in luminance caused by blinking. Luminance refers to the brightness of a visual stimulus. When you blink, your eyes temporarily close, causing a sudden change in luminance. This change helps reset the visual information coming into your eyes, which may help your brain process visual input more efficiently.
“Blinking effectively reformats visual information by adjusting the visual input to the retina, producing a luminance signal that is drastically different from what we normally experience when looking at a point in a scene,” explained Lucci, a professor in the Department of Brain and Cognitive Sciences.
To further test this hypothesis, the researchers conducted a control experiment in which they simulated the effect of blinking by briefly darkening the visual stimulus. Participants’ performance improved in a similar way to when they blinked naturally, supporting the idea that it is the change in luminance itself that is responsible for the visual processing improvement, rather than the physical act of blinking.
The study concluded that blinking during visual tasks produces beneficial luminance changes and improves the brain’s ability to process visual information. These findings suggest that blinking plays an important role in visual perception beyond simply moistening the eyes. The results also suggest that the human visual system has evolved to take advantage of these brief interruptions in vision to improve overall vision and processing ability.
“We found that human observers benefit from blink moments, as would be predicted by the information they convey,” said Bin Yang, a graduate student in the Lucci lab and first author of the paper. “Thus, contrary to common belief, blinks improve rather than hinder visual processing, fully compensating for loss of stimulus exposure.”
the study, “Blinking as a stage in visual processing‘ was published on April 2, 2024.
