UFC fighter weigh ins used to be a minor part of the show. Now they have grown to the point where thousands clamor for a look at the fighters. Among those looking most carefully are two scientists, who analyzed hundreds of images from dozens of weigh ins, for science.
The pair wanted to see if there was a correlation between facial expression and preformance - is there a game face that shows advantage? There is, and it beats the odds.
Michael Kraus and Teh-Way David Chen recruited four coders to assess the presence of smiles, and smile intensity, in photographs taken before 152 fights. Fighter smiles were mostly "non-Duchenne", with little or no crinkling around the eyes. The researchers wanted to test the idea that in this context, smiles are an involuntary signal of submission and lack of aggression.
Consistent with the researchers' predictions, fighters who smiled more intensely prior to a fight were more likely to be knocked down in the clash, to be hit more times, and to be wrestled to the ground by their opponent). On the other hand, fighters with neutral facial expressions pre-match were more likely to excel and dominate in the fight the next day.
These associations between facial expression and fighting performance held even after controlling for betting behaviour by fans, which suggests a fighter's smile reveals information about their lack of aggression beyond what is known by experts. Incidentally, smaller fighters smiled more often, consistent with the study's main thesis, but smiling was still linked with poorer fight performance after factoring out the role of size.
If fighters' smiles are a sign of weakness, there's a chance opponents may pick up on this cue, which could boost their own performance, possibly through increased confidence or aggression.
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Kraus, M., and Chen, T. (2013). A Winning Smile? Smile Intensity, Physical Dominance, and Fighter Performance. Emotion DOI: 10.1037/a0030745
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