The Perfect Smile Hits the Smile Sweet Spot, Study Says

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While there’s no one smile that is perfect, there are ways you can help your smile be at its best.

Researchers from the University of Minnesota investigated what exactly makes a successful smile by presenting computer-animated facial expressions to people at the Minnesota State Fair. Those who studied the smiles rated the smiles based on effectiveness, genuineness, pleasantness and perceived emotional intent.

Credit: Luciane Lazzaris/Flickr, CC BY-ND 2.0

“Decades of psychological research has revealed that different facial expressions can communicate different emotional intents,” said study author Nathaniel Helwig to ResearchGate. “Smiles are arguably the most important facial expression, given their frequent use in day-to-day interpersonal interactions.”

The importance of smiles was on the mind of Sofia Lyford-Pike, a facial plastic and reconstructive surgeon at the University of Minnesota. Lyford-Pike was curious about what it would take to help her patients recreate the perfect smile and step back into society after suffering from a stroke, disease or injury.

“Partial facial paralysis robs an individual of their ability to smile, which can have significant psychological and social consequences,” Helwig said. “To improve outcomes for these individuals, it is imperative to have a detailed understanding of what exactly constitutes a ‘successful smile.’”

Helwig said the study intentionally stayed away from any mention of a concrete definition for a successful smile, hoping that the fairgoers would make their own evaluations. Instead of having a clinical definition, the researchers wanted to field the colloquial opinions of others on what a successful smile really is.

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The researchers presented the computer-animated faces at the fair, all with tweaked smiles in one way or another. More than 800 people rated the smiles.

“We created a collection of 27 computer-animated facial expressions by systematically manipulating three features that are commonly assessed in facial reconstructive surgery: the angle of the smile, the extent of the smile and the amount of teeth displayed during the smile,” Helwig said.

The study found that there’s no one way to smile successfully, but that a handful of subtle factors can make or break a smile. The brain rapidly comprehends a smile and the “smile sweet spot” has a few crucial aspects.

“We observed somewhat of a Goldilocks Phenomenon, such that successful smiles needed just the right amount of teeth for the given smile angle and extent. Also, we found that too much smile angle and extent produced fake and creepy smiles, which contradicts the idea that ‘more is always better,’” Helwig said. “Interestingly, we discovered that smiles with slight timing asymmetries are more successful than perfectly symmetric smiles, but asymmetries larger than 125 milliseconds were detrimental.”

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Helwig and his team only focused on the mouth for their study and didn’t expand their research to the rest of the face. The study supports the idea that the mouth is prominent in figuring out someone’s emotional intent, he said.

“Our study looked at just the mouth for two reasons. One, smiling impairment due to restricted mouth motion increases depressive symptoms for patients with partial facial paralysis,” Helwig said. “Two, existing surgical interventions have shown particular success in restoring mouth movement.”

Helwig said a goal for the future is to provide personalized feedback on how someone can retrain their smile to be more successful. The study will help to improve facial reanimation surgeries and therapies as well.

“Beyond these applications, our research can help animators create more believable animation for virtual humans in movies and virtual reality,” Helwig said. “Digital animations of facial expressions can be used to develop personalized biofeedback applications (e.g., for a smart phone or tablet) to help people better display and recognize different facial expressions of emotions, which could be useful for treating disorders such as autism.”