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Researchers from the University of Minnesota have figured out the features of a winning smile.

  • It's a balance of the mouth's angle, smile width, how many teeth are visible and symmetry. Best bet: showing just a little bit of teeth.
  • Smiles that form slightly asymmetrically were seen as more "genuine" and "pleasant" — to a point. If it happens relatively slowly (longer than 125 milliseconds), the crooked smile just starts to get "creepy."

Why the findings matter:

  • They guide surgeries to reanimate someone's face after a stroke, says author Sofia Lyford-Pike, a facial plastic and reconstructive surgeon at the University of Minnesota. (People who are unable to smile effectively are at increased risk for depression.)
  • It could inform computer graphics.
  • More broadly, the work may help to understand how individual differences in facial expressions can lead to differences in how people perceive threats, trustworthiness and other socially relevant cues, something researchers have long studied.

What they did: The researchers created 3D computer animated faces with slightly different smiles constructed from combinations of different angles of the mouth, varying extents of the smile, how much teeth were showing and how symmetrically the smile formed on the face. 802 people were then asked to rate 250 millisecond-long video clips of the smiles forming for their effectiveness, how genuine they seemed, whether they were "pleasant" or "creepy," and what emotion they thought the smile conveyed. The best-rated smiles have lips angled between 13 and 17 degrees and extend between 55% and 62% of the distance between the eye's pupils.

Two smiles with a combination of (a) smaller and (b) larger mouth angle-smile width combination. Increasing how much teeth are visible led to a more favorable rating of the smile in (b) and a worse rating for (a).Helwig et al. University of Minnesota

Limitation: The study only modeled the mouth. Previous work has found the eyes influence people's perceptions but the study shows the mouth can transmit a lot of information on its own, says Lyford-Pike.

What's next: Determining whether the results translate to spontaneous smiles of different, real people, is a key question, says Aleix Martinez, a cognitive scientist and professor of electrical and computer engineering at Ohio State University. Martinez asks: "Can you predict a person's success (personal, profession) on the "niceness" of their smiles?"

Go deeper

Bryan Walsh, author of Future
1 hour ago - Health

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Illustration: Aïda Amer/Axios

President Biden's plan to accelerate the reopening of K-8 schools faces major challenges from a still out-of-control pandemic and more contagious coronavirus variants.

Why it matters: The longer American kids miss in-person schooling, the further they fall behind. But the uncertain state of the science on the role young children play in the pandemic continues to complicate efforts to reopen schools.

Focus group: Former Trump voters say he should never hold office again

Illustration: Sarah Grillo/Axios

"Relief" is the top emotion some swing voters who used to support Donald Trump say they felt as they watched President Biden's swearing-in, followed by "hope."

Why it matters: For voters on the bubble between parties, this moment is less about excitement for Biden or liberal politics than exhaustion and disgust with Trump and a craving for national healing. Most said Trump should be prohibited from ever holding office again.

Updated 15 hours ago - Politics & Policy

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