Adaptive attunement to the sex of individuals at a competition: the ratio of opposite- to same-sex individuals correlates with changes in competitors' testosterone levels

Evolutionary theories (e.g., the challenge hypothesis) suggest that testosterone plays an important role in intrasexual competition. In addition, those theories suggest that testosterone responses during competition should depend upon the presence of potential, immediate mating opportunities associated with the competition. The current research tested the hypothesis that the sex composition of individuals at a competition (ratio of opposite-sex, potential mates to same-sex individuals) would influence changes in competitors' testosterone levels. Consistent with our hypotheses, higher ratios of opposite- to same-sex individuals at an ultimate frisbee tournament were associated with greater increases in salivary testosterone among competitors. The relationship between sex ratio and increased salivary testosterone was observed for both male and female competitors and occurred regardless of whether competitors won or lost. Findings are consistent with the hypothesis that testosterone responses during competition are influenced by cues of potential, immediate mating opportunities.