Does a single dose of testosterone increase willingness to compete, confidence, and risk-taking in men? Evidence from two randomised placebo-controlled experiments.

The sex steroid hormone testosterone regulates aggression and display of dominance in non-human animals. According to the Challenge Hypothesis, these effects arise from context-sensitive testosterone increases that facilitate inter-male competitions over resources, status, and mates. A growing body of literature documents similar testosterone effects on behaviors related to competition and risk-taking in humans, though the findings have been mixed.