For his research, Witkower focused on the so-called Duchenne Smile. This smile, which is known for communicating happiness, involves the specific muscles that raise the corners of the mouth, and that circle the eyes. For his study, Witkower and colleagues had a little over 300 people sit in front of the camera and asked them to smile. 'About half adopted the Duchenne pose,' says Witkower. 'Not everyone smiles the same, but especially people who describe themselves as warm, trustworthy, conscientious, or less aggressive and hubristic naturally demonstrate that specific smile.'

Duchenne smile

'Duchenne smiles can also tell others a lot about your personality,' says Witkower. A second sample of roughly 1000 participants were asked to identify the personality traits of warmth, trustworthiness, conscientiousness, aggression and hubris, from either a smiling or neutral photograph of a person from the original sample. The assessment made by the viewers was compared to what the original participants said about themselves. 'Viewers making assessments based on a smiling face were generally more accurate than those assessing a neutral face. In fact, the accuracy of these judgments was linked directly to observing Duchenne smiles.'

According to Witkower, it’s not easy to fake this smile. 'Someone who attributes colder character traits to themselves cannot easily switch to a smile as favorable as the Duchenne Smile. They may instead show an asymmetrical smile, or only smile with the corners of their mouth but keeping the eye muscles less engaged.'

A revealing smile

The smile thus ‘reveals’ aspects of who we are. And according to Witkower, it raises questions about privacy. 'Our smile is everywhere. On your LinkedIn profile, on a dating site, in a yearbook, on an employee badge—it’s often the first thing people see of you, even before you’ve introduced yourself. 'It’s important to be aware that our smile reveals personality traits to others,' says Witkower. 'And the question is whether that’s fair. You are more or less forced to give away this kind of information about yourself in all kinds of places where you no longer have control over it.'

Publication

Witkower, Z., Tian, L., Tracy, J. L., & Rule, N. (2024). Smile variation leaks personality and increases the accuracy of interpersonal judgments. Proceedings of the National Academy of Sciences: Nexus, 3(9), 343.