The day before mixed martial artists compete in the Ultimate Fighting Championships (UFC), they pose with each other in a staged face-off. A new study has analysed photographs taken at dozens of these pre-fight encounters and found that competitors who smile are more likely to lose the match the next day (pdf via author website).
Michael Kraus and Teh-Way David Chen recruited four coders (blind to the aims of the study) to assess the presence of smiles, and smile intensity, in photographs taken of 152 fighters in 76 face-offs. Fighter smiles were mostly "non-Duchenne", with little or no crinkling around the eyes. Data on the fights was then obtained from official UFC statistics. The researchers wanted to test the idea that in this context, smiles are an involuntary signal of submission and lack of aggression, just as teeth baring is in the animal kingdom.
Consistent with the researchers' predictions, fighters who smiled more intensely prior to a fight were more likely to lose, to be knocked down in the clash, to be hit more times, and to be wrestled to the ground by their opponent (statistically speaking, the effect sizes here were small to medium). On the other hand, fighters with neutral facial expressions pre-match were more likely to excel and dominate in the fight the next day, including being more likely to win by knock-out or submission.link full research report here