Human Male Body Size Predicts Increased Knockout Power, Which Is Accurately Tracked by Conspecific Judgments of Male Dominance.

Humans have undergone a long evolutionary history of violent agonistic exchanges, which would have placed selective pressures on greater body size and the psychophysical systems that detect them. The present work showed that greater body size in humans predicted increased knockout power during combative contests (Study 1a-1b: total N = 5,866; Study 2: N = 44 openweight fights). In agonistic exchanges reflective of ancestral size asymmetries, heavier combatants were 200% more likely to win against their lighter counterparts because they were 200% more likely to knock them out (Study 2). Human dominance judgments (total N = 500 MTurkers) accurately tracked the frequency with which men (N = 516) knocked out similar-sized adversaries (Study 3). Humans were able to directly perceive a man's knockout power because they were attending to cues of a man's body size. Human dominance judgments-which are important across numerous psychological domains, including attractiveness, leadership, and legal decision-making-accurately predict the likelihood with which a potential mate, ally, or rival can incapacitate their adversaries.

Human third-party observers accurately track fighting skill and vigour along their unique paths to victory.

Sexual selection via male-male contest competition has shaped the evolution of agonistic displays, weaponry, and fighting styles, and is further argued to have shaped human psychological mechanisms to detect, process, and respond appropriately to cues of fighting ability. Drawing on the largest fight-specific dataset to date across the sports and biological sciences (N = 2765 fights), we examined how different indicators of fighting ability in humans reflect unique paths to victory and indicate different forms of perceived and actual resource-holding power (RHP). Overall, we discovered that: (1) both striking skill and vigour, and grappling skill and vigour, individually and collectively predict RHP; (2) different RHP indicators are distinguished by a unique path to victory (e.g., striking skill is a knockout-typical strategy, whereas grappling vigour is a submission-typical strategy); and (3) third-party observers accurately track fighting skill and vigour along their unique paths to victory. Our argument that different measures of RHP are associated with unique paths to victory, and third-party observers accurately track fighting vigour and skill along their unique paths to victory, advance our understanding not only of human contest competition, but animal contest theory more broadly.

Facial width-to-height ratio predicts fighting success: A direct replication and extension of Zilioli et al. (2014).

Zilioli et al. (2014) were the first to show an association between male facial width-to-height ratio (fWHR) and physical aggression and fighting ability in professional mixed-martial-arts fighters. Here, we re-examined this relationship by replicating (using all original measures) and extending (using 23 new variables related to fighting performance) Zilioli et al. (2014) in a statistically well-powered sample of 520 fighters using automatic and manual measures of the fWHR involving both eyelid and eyebrow landmarks, used interchangeably in previous reports (Studies 1-2). Most importantly, we successfully replicated Zilioli et al.'s (2014) central finding that fighters' fWHR, when manually calculated using the eyebrow landmark, predicted their fighting success (p = .004, controlling for body mass index and total fights). Consistent with past criticisms of using fight rather than fighter data to examine fighting success, which have argued that individual fights can be suddenly and unexpectedly determined and do not capture an individual's overall ability to succeed, Study 3 (N = 1367 fights) found no association between fWHR and singular victories. Studies 1-3 showed continual evidence that larger fWHRs were associated with grappling abilities, even after controlling for demographic and allometric factors. Strikingly, Study 3 discovered associations between all fWHR measures and grappling skill that remained robust before and after controlling for 17 different control variables. We discuss that grappling, or the act of taking down an opponent, involves a more aggressive, close-combat approach than does striking. Combined, these results offer additional support for the argument that fWHR may have been shaped by sexual selection.

Deceptive Affectionate Messages: Mate Retention Deployed Under the Threat of Partner Infidelity.

Deceptive affectionate messages (DAMs) have been proposed to act as relational maintenance techniques and, as such, might be part of a greater repertoire of mate retention behaviors. We analyzed data from 1,993 Mechanical Turk participants to examine the relations between DAMs and mate retention, and whether these relations were mediated by the perceived risk of partner infidelity. In line with predictions, frequency of DAMs positively predicted general mate retention and cost-inflicting mate retention through the perceived risk of partner infidelity. In line with our nondirectional prediction, we also found that frequency of DAMs negatively predicted benefit-provisioning mate retention behaviors. In an exploratory mediation analysis of DAMs on benefit-provisioning mate retention via perceived partner infidelity, we surprisingly found that DAMs negatively predicted benefit-provisioning behavior due to the perceived risk of partner infidelity, suggesting that DAMs-but not benefit-provisioning mate retention-are deployed under the threat of partner infidelity. Overall, these findings suggest that DAMs might belong to a greater repertoire of mate retention (especially cost-inflicting) behaviors to thwart the possibility of partner infidelity.