Blinking suppression reveals how the brain filters speech in noisy environments

Blinking is a human reflex most often performed without thinking, like breathing. Although research on blinking is usually related to vision, a new Concordia study examines how blinking is connected to cognitive function such as filtering out background noise to focus on what someone is trying to say to us in a crowded room.

Writing in the journal Trends in Hearing, the researchers describe two experiments designed to measure how eye blinking changes in response to stimuli under different conditions.

They found that people naturally blink less when they are working harder to understand speech in noisy environments, suggesting that the act of blinking reflects the mental effort behind everyday listening. The research further showed that blink patterns remained stable across different lighting conditions - meaning people blinked just as much whether lighting was bright, dim or dark.

We wanted to know if blinking was impacted by environmental factors and how it related to executive function. For instance, is there a strategic timing of a person's blinks so they would not miss out on what is being said?"

Pénélope Coupal, lead author, an Honours student at the Laboratory for Hearing and Cognition

They found that this was indeed the case.

"We don't just blink randomly," says Coupal. "In fact, we blink systematically less when salient information is presented."

Linking ocular and auditory activity

In the study involving almost 50 adults, participants sat in a soundproof room, fixated on a cross on a screen. They listened to short sentences played through headphones while background noise levels - the signal-to-noise ratio (SNR) - varied from quiet to loud.

Using eye-tracking glasses, the researchers recorded every blink and its exact timing as participants listened to the sentences. Each trial was then divided into three time windows: before, during and after each sentence.

They found blink rates consistently dropped while participants listened to a sentence compared to the periods immediately before and after. This blink suppression was especially pronounced in the noisiest conditions, when speech was hardest to understand.

In a follow-up experiment, the researchers tested blinking rates at different SNRs in rooms with dark, medium and bright lighting. The same pattern emerged. This indicated that cognitive demands drive the effect, rather than how much light reaches the eye.

While the researchers noted that blink rates varied between individuals - some participant blinked as little as 10 times per minute, while others may have blinked 70 times per minute - the general trend was visible and significant.

Most previous studies linking ocular function to cognitive effort focused on measuring pupil dilation (pupillometry) and treated blinks as nuisances to be removed from the data. This study reanalyzed existing pupillometry data to focus specifically on blink timing and frequency. The researchers say their findings confirm blink rates can be used as a practical, low-burden metric to measure cognitive function in both laboratory and real-world settings.

"Our study suggests that blinking is associated with losing information, both visual and auditory," says co-author Mickael Deroche, an associate professor in the Department of Psychology.

"That is presumably why we suppress blinking when important information is coming. But to be fully convincing, we need to map out the precise timing and pattern of how visual/auditory information is lost during a blink. This is the logical next step, and a study is being led by postdoctoral fellow Charlotte Bigras. But these findings are far from trivial."

Yue Zhang contributed to this research.