Blinking may feel like something that’s done automatically by your body — a simple way to keep your eyes clean and safe — but there may be more to it than that. A new study suggests that eye blinks can serve as nonverbal cues in conversations.

Image credits: Chamaeleon / Wikipedia.

Blinking is the semi-automatic closing of the eyelid. Your body generally takes care of that without a conscious effort, but you can override it if you will. The main function of blinking is to help spread tears across and remove irritants from the surface of the eye. But here’s the thing: on average, humans blink 13,500 times a day, or around 9 times a minute — and that’s much more than is necessary for lubricating the eyeballs

Infants don’t blink at the same rate as adults — they do it much rarer, at an average rate of 1-2 times a minute. While several other explanations are plausible (for instance, infants sleep more than adults do, and their eyes aren’t as fatigued), it’s also possible that the infants just haven’t picked up on the social cues associated with blinking.

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To make matters even more puzzling, previous studies have shown that blinks often occur at natural pauses in conversation. To test the possibility that blinks are social cues, researchers developed a virtual reality environment where participants talk to an avatar called a “virtual listener.” The participants were asked simple questions such as “How was your weekend?”, while the avatar’s non-verbal cues were controlled by the researchers.

“While blinking tends to be subliminal, the significance of mutual gaze in human interaction raises the question whether the interruption of mutual gaze through blinking may also be communicative,” researchers write in the study.

Particularly, the length of the avatar’s blinking was controlled. Longer blinks elicited substantially shorter answers from volunteers, whereas shorter blinks were associated with longer answers. The fun part is, participants didn’t realize what was happening — none of them reported noticing any variation in the avatar’s blinking, which suggests that any potential cues were picked up unconsciously.

“Our findings suggest that, in addition to physiological, perceptual and cognitive functions, listener blinks are also perceived as communicative signals, directly influencing speakers’ communicative behavior in face-to-face communication, the authors continue.”

While this theory is still in its early phases, it’s also another piece of the larger puzzle that is human social communication.

“More generally, these findings may be interpreted as shedding new light on the evolutionary origins of mental-state signaling, which is a crucial ingredient for achieving mutual understanding in everyday social interaction.”

Journal Reference: Hömke P, Holler J, Levinson SC (2018) Eye blinks are perceived as communicative signals in human face-to-face interaction. PLoS ONE 13(12): e0208030.