Facial Cues in Humans Predict Winners and Losers in Mixed Martial Arts

25 In antagonistic encounters the primary decision to be made is to fight or not and so it 26 is predicted that animals may possess adaptations to assess fighting ability in their 27 opponents. Previous studies suggest humans can assess strength and fighting ability 28 based on facial appearance. Here we extend these findings to specific contests by 29 examining the perception of male faces from paired winners and losers of individual 30 fights in mixed martial arts sporting competitions. Observers were presented with 31 image pairs and asked to choose which of the two men was most likely to win if they 32 fought while other observers chose between the faces based on other questions. We 33 found that individuals performed at rates above chance in correctly selecting the 34 winner as more likely to win the fight than the loser. We also found that winners were 35 seen to be more masculine, stronger, and aggressive than losers. Finally, women saw 36 the winners as more attractive than the losers. Together these findings demonstrate 37 that 1. humans can correctly predict the outcome of specific fighting contests, 2. that 38 perceived masculinity/strength/aggression are putative cues to fighting success 39 available from faces, and 3. that facial cues associated with successful male-male 40 competition are attractive to women. 41