Human perception of fighting ability: facial cues predict winners in Mixed Martial Arts fights

In antagonistic encounters, the primary decision to be made is to fight or not. Animals may then possess adaptations to assess fighting ability in their opponents. Previous studies suggest that humans can assess strength and fighting ability based on facial appearance. Here we extend these findings to specific contests by examining the perception of male faces from paired winners and losers of individual fights in mixed martial arts sporting competitions. Observers, unfamiliar with the outcome, were presented with image pairs and asked to choose which of the 2 men was more likely to win if they fought while other observers chose between the faces based on masculinity, strength, aggressiveness, and attractiveness. We found that individuals performed at rates above chance in correctly selecting the winner as more likely to win the fight than the loser. We also found that winners were seen to be more masculine, stronger, and more aggressive than losers. Finally, women saw the winners as more attractive than the losers. Together these findings demonstrate that 1) humans can predict the outcome of specific fighting contests based on facial cues, 2) perceived masculinity and strength are putative cues to fighting success available from faces, and 3) facial cues associated with successful male–male competition are attractive to women

Men’s preferences for women’s breast size and shape in four cultures

The morphology of human female breasts typical for their permanent fat deposits appears to be unique among primates. It has been previously suggested that female breast morphology arose as a result of sexual selection. This is supported by evidence showing that women with larger breasts tend to have higher estrogen levels; breast size may therefore serve as an indicator of potential fertility. However, breasts become less firm with age and parity, and breast shape could thus also serve as a marker of residual fertility. Therefore, cross-culturally, males are hypothesized to prefer breast morphology that indicates both high potential and residual fertility. To test this, we performed a survey on men´s preferences for breast morphology in four different cultures (Brazil, Cameroon, the Czech Republic, Namibia). As stimuli, we used two sets of images varying in breast size (marker of potential fertility) and level of breast firmness (marker of residual fertility). Individual preferences for breast size were variable, but the majority of raters preferred medium sized, followed by large sized breasts. In contrast, we found systematic directional preferences for firm breasts across all four samples. This pattern supports the idea that breast morphology may serve as a residual fertility indicator, but offers more limited support for the potential fertility indicator hypothesis. Future studies should focus on a potential interaction between the two parameters, breast size and firmness, which, taken together, may help to explain the relatively large variation in women's breast sizes

Gonadal suppression alters axillary steroid secretions in men, but does that affect olfactory social signaling?

Background and objective: Luteinizing hormone-releasing hormone agonists (LHRHa) suppress gonadal hormone production and are commonly used to treat prostate cancer (PC) in men and conditions ranging from uterine fibroids to estrogen-sensitive cancers in women. They are also used to delay sexual development in children considering gender reassignment or experiencing premature puberty. As chemically castrating agents, LHRHa may affect cutaneous steroid secretions, which, in turn, could alter body odor and influence the psycho-sexual dynamics between individuals. The objectives of the present study were to determine (1) if LHRHa indeed alter cutaneous skin secretions, and (2) whether this leads to perceivable changes in body odor. Material and methods: Axillary skin secretions were collected on new cotton T-shirts worn by men undergoing androgen deprivation therapy with an LHRHa to treat PC (n = 10), both before starting the LHRHa and 3 months later. Healthy heterosexual university students (50 males, 50 females) were recruited to smell and rate the shirts for their masculinity, attractiveness, and intensity of odor. Liquid chromatography-mass spectrometry (LC-MS) was also used to analyze steroids extracted from the shirt samples. Results: LC-MS showed a statistically significant decline in the concentration of the androgenic metabolites, androsterone and 5α-androstane-3,17-dione. This confirms that LHRHa drugs that suppress gonadal hormone production markedly reduce cutaneous secretion of androgenic metabolic intermediates in adult males. However, no differences in odor were detected in the ratings of the shirts by male, female, nor male and female raters combined for any of the three variables assessed. Possible reasons why the human sniffers failed to perceive a change in odor are explored. Conclusion: Our data document that LHRHa alter steroid skin secretions in older men, but whether such changes alter the olfactory signals that might influence psychosocial interactions remains unresolved

Perceived aggressiveness predicts fighting performance in Mixed-Martial-Arts fighters

Accurate assessment of competitive ability is a critical component of contest behavior in animals, and it could be just as important in human competition, particularly in human ancestral populations. Here, we tested the role that facial perception plays in this assessment by investigating the association between both perceived aggressiveness and perceived fighting ability in fighters' faces and their actual fighting success. Perceived aggressiveness was positively associated with the proportion of fights won, after we controlled for the effect of weight, which also independently predicted perceived aggression. In contrast, perception of fighting ability was confounded by weight, and an association between perceived fighting ability and actual fighting success was restricted to heavyweight fighters. Shape regressions revealed that aggressive-looking faces are generally wider and have a broader chin, more prominent eyebrows, and a larger nose than less aggressive-looking faces. Our results indicate that perception of aggressiveness and fighting ability might cue different aspects of success in male-male physical confrontation