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. (shrink)

Across taxa, strength and size are elementary determinants of relative fighting capacity; in species with complex behavioral repertoires, numerous additional factors also contribute. When many factors must be considered simultaneously, decision-making in agonistic contexts can be facilitated through the use of a summary representation. Size and strength may constitute the dimensions used to form such a representation, such that tactical advantages or liabilities influence the conceptualized size and muscularity of an antagonist. If so, and given the continued importance of physical (...) strength in human male-male conflicts, a man’s own strength will influence his conceptualization of the absolute size and strength of an opponent. In the research reported here, male participants’ chest compression strength was compared with their estimates of the size and muscularity of an unfamiliar potential antagonist, presented either as a supporter of a rival sports team (Study 1, conducted in urban California, and Study 2, conducted in rural Fiji) or as a man armed with a handgun (Study 3, conducted in rural Fiji). Consistent with predictions, composite measures of male participants’ estimates of the size/strength of a potential antagonist were inversely correlated with the participant’s own strength. Therefore, consonant with a history wherein violent intrasexual selection has acted on human males, a man’s own physical strength influences his representations of potential antagonists. (shrink)