Ph.D Gil Greengross wrote an article in Psychology Today of a new study published in the journal ‘Emotion’ that wanted to test whether smiles are a form of submissive behavior by looking at the pre-fight facial expressions of UFC fighters. Here’s a snippet of what they found.

“The idea behind the study is that people who smile more or have more intense smiles, are less aggressive in nature and also tend to have lower testosterone levels, compared to those who smile less or have weaker smiles. Studies show that low status individuals smile more than higher status people, and in general, smiling is seen as a sign of appeasement. Based on these studies, the authors wanted to see if “smile intensity prior to a physical confrontation would unintentionally leak information about the reduced hostility and aggression of expressers, and thereby act as a sign of reduced physical dominance.” In other words, the hypothesis is that those who smile prior to a fight lack the aggression needed to win it, and the non-smiling fighter may conclude that his opponent is weak and submissive, which could motivate him even more and improve his chances of winning.

To test their hypothesis, the researchers coded the smile intensity of 152 UFC fighters one day prior to their fight. The photographs were taken during the traditional face-off between the fighters. Four independent judges, blind to the study hypothesis, coded the smiles for intensity. The researchers also controlled for potential confounding variables, such as the gambling odds of the fight.

The results showed that fighters who displayed a less intense smile won more fights. This was true for all fights, including the ones that were decided by a knockout. Interestingly, smile intensity predicted fight outcomes for the fights on the day after the photograph was taken but not for subsequent fights. This finding suggests that smile intensity does not necessarily reflect an individual personality trait, but rather is a situational cue that that has short-lived consequences. Think of it as the difference between having a humorous outlook that affects your life as a whole, compared to laughing in response to a specific joke that does not necessarily reflect your humor preferences.”

If you want to read more of the study, check it out here.