Are they really listening? Watch their blinks

The findings were published in the journal Trends in Hearing. In the paper, researchers outline two experiments designed to observe how blinking behavior changes when people are exposed to different listening conditions.

Fewer Blinks Signal Greater Mental Effort

The researchers discovered that people tend to blink less when they are working harder to understand speech in noisy settings. This reduction in blinking appears to reflect the mental effort involved in listening closely during everyday conversations. Importantly, the pattern stayed the same regardless of lighting conditions -- participants blinked at similar rates whether the room was bright, dim, or dark.

"We wanted to know if blinking was impacted by environmental factors and how it related to executive function," says lead author Pénélope Coupal, an Honours student at the Laboratory for Hearing and Cognition. "For instance, is there a strategic timing of a person's blinks so they would not miss out on what is being said?"

The results showed that blinking does appear to be timed in a purposeful way.

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

Measuring Blinks During Challenging Listening Tasks

The study included nearly 50 adult participants. Each person sat in a soundproof room and focused on a fixed cross displayed on a screen. They listened to short spoken sentences through headphones while the level of background noise changed. The signal-to-noise ratio (SNR) ranged from very quiet to highly distracting.

Participants wore eye-tracking glasses that captured every blink and recorded exactly when each blink occurred. Researchers divided each listening session into three phases: before the sentence played, while it was playing, and immediately afterward.

Blink rates dropped most noticeably during the sentences themselves, compared to the moments before and after. The decrease was strongest when background noise was loudest and speech was hardest to understand.

Lighting Does Not Explain the Effect

In a second experiment, the team tested blinking behavior again while changing the lighting conditions. Participants completed the listening tasks in dark, medium, and brightly lit rooms, across different SNR levels. The same blink suppression pattern appeared each time.

This consistency showed that the effect was driven by cognitive demands rather than changes in how much light entered the eyes.

Although individuals differed widely in how often they blinked overall -- some participant blinked as little as 10 times per minute, while others may have blinked 70 times per minute -- the overall trend was clear and statistically meaningful.

Blinks as a Tool for Studying Brain Function

Earlier research linking eye behavior to mental effort mostly relied on pupil dilation (pupillometry). In many cases, blinks were treated as unwanted interruptions and removed from the data. In contrast, this study revisited existing pupillometry data and focused directly on blink timing and frequency.

The researchers say the results support using blink rate as a simple and low-effort way to measure cognitive function, both in controlled laboratory experiments and in real-world situations.

"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.