Mind & Body

Scientists Have Identified 3 Types of Smiles

Smiles can carry a lot of messages, not all of them positive. As the great sage Dwight Schrute from "The Office" once noted, "When someone smiles at me, all I see is a chimpanzee begging for its life." According to a new study, a smile alone can be enough to cause a sudden feeling of stress — if it's not the right kind.

Related Video: The Future of Facial Recognition

Grin and Bear It

Have you ever met someone who smiles like a shark? It's as if they're looking at you like you're unbelievably beneath them, or worse — like you're a light snack. According to a new study published in Nature, there's a distinct category of smiles that convey malice or condescension, and our brains are wired to instantly respond accordingly.

Here's how the study worked. First, the 90 participants (all of them male) were instructed to make a short speech to a video camera. Then, the scientists showed them a live feed of a judge (also male) reacting to their performance. There's just one thing — it wasn't a live feed at all. Instead, the researchers played a prerecorded clip of the judge reacting with one of three different smiles. One was what they deemed a "rewarding smile," which is meant to signal approval and encouragement. The second was an "affiliation smile," meant to send a message of relatability and understanding. And the last one was the bad one: the "dominant smile." That's the grin that says, "I know so much more than you," "It's cute how hard you're trying," and "I can't wait to tell the whole office about this yutz." And believe it or not, the smile the speech-givers saw had a major effect on their mental state.

No matter what smile flashed across the screen, the participants demonstrated a spike in the stress hormone cortisol when they saw their judge's face. But the ones who saw the dominant smile experienced a surge three times greater than any of the other participants. It's proof that humans naturally react to the facial expressions of others, even if nothing is said.

High-Anxiety Heartbeats

There was one group that didn't experience these large stress spikes in reaction to the dominant smiles, however: participants whose heart rates have less variation. They didn't seem to react much differently to a dominant smile than they did to a friendly one. Interestingly, a less varied heart rate has been linked to depression and anxiety disorders, and some of the researchers make the case that these disorders could correlate with a lack of responsiveness to social cues. But there's a lot more work to be done before this can be said with any certainty — and especially before they can say whether the primary cause is the heart rate, the depression, the social engagement, or something else.

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Did you know that smiling didn't come into vogue in western Europe until well into the 18th century? It seems impossible, but it's true. Read all about it in Colin Jones' "The Smile Revolution," a cultural history connecting art, literature, and dentistry. We handpick reading recommendations we think you may like. If you choose to make a purchase through that link, Curiosity will get a share of the sale.

Written by Reuben Westmaas April 12, 2018

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