As a species, humans don't think hard about blinking. It's just not the central drama of our days. However, a recent study found that blinks are important non-verbal communication — and that when we're talking to someone, we subtly and subconsciously respond to the length of their blinks.

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In the Blink of an Eye

Blinking is more impressive than you might expect. It's the fastest motion the human body can do, and it happens an average of 13,500 times a day — just shy of 10 times a minute. That makes it the action you do most frequently with your face. It's not for purely utilitarian reasons; you blink far more than you strictly need to for lubricating your eyeballs.

Humans don't blink at a steady rate throughout their lives, either. As infants, we barely blink at all, but as we get older, our blinking accelerates until it levels off at that 13,500-a-day rate. This gels with research that suggests blinking and a complex social life generally go hand in hand. Primates blink more when they live in larger groups; humans specifically blink more when they're mentally stimulated, and they blink most during face-to-face conversation.

Previous research has found that people don't blink at random in conversation, either. Though you blink subconsciously, you nevertheless tend to do it toward the end of a conversation partner's "turn" in a chat. Researchers believe that it's part of an array of gestures, like nodding, that you use to signal you understand what someone is telling you. Blinking is like nonverbal shorthand for "Got it!"

But are all blinks created equal?

The Power of Long Blinks

A new study started with the hypothesis that no, not all blinks are equal. Specifically, the researchers at the Netherlands' Max Planck Institute for Psycholinguistics hypothesized that short blinks meant something slightly different from long blinks.

To test this theory, they asked 35 people to converse with a digital avatar projected on a screen. This female figure would ask subjects open-ended questions — like "How was your weekend, what did you do?" — and then listen as they responded. She signaled her listening with nods paired with either long or short blinks. (When researchers observed organic human conversations, they found that nodding and blinking typically went hand in hand.)

Both of the avatar's blinks lasted for less than a second; the short blink was 208 milliseconds, and the long blink was 607 milliseconds (translated to music, this would be a sixteenth note and an eighth note, respectively, played at around 60 beats per minute). That timing made them read as basically unremarkable; when asked about the avatar's blinking afterward, subjects said they didn't notice anything special about it. Nevertheless, the length of the avatar's blinks had a measurable effect on conversations. Short blinks led to longer, more detailed answers; long blinks prompted subjects to respond much more briefly.

Why? The researchers think that long blinks may signify understanding more strongly than short blinks. So if a short blink means "I'm following what you're saying," a long blink means, "I totally get it." Perhaps this is because long blinks read as more intentional; conscious blinking takes longer than blinking done instinctively.

More broadly, this study shows that we're always subconsciously interpreting each other's body language. Even when we're speaking, we're "listening," too — to our conversation partner's gestures. And when a friend tells you someone "seemed to understand" or "seemed to be losing interest," but can't put their finger on exactly why, they may be talking about blinking without even knowing it.

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For the ultimate how-to guide on human communication, you'll definitely want to check out Dale Carnegie's classic, "How to Win Friends & Influence People." The audiobook is free with an Audible trial. We handpick reading recommendations we think you may like. If you choose to make a purchase, Curiosity will get a share of the sale.

Written by Mae Rice January 22, 2019

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