Does Testosterone Administration Increase Competitiveness, Confidence and Financial Risk-taking in Men?

The sex steroid hormone testosterone regulates male-typical behaviors such as aggression and displays 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 literature documents similar effects of testosterone on economic behaviors related to competition and risk-taking in humans, though findings to date have been mixed. Here, we report two randomized double-blind placebo-controlled testosterone administration experiments, whose combined sample (N = 334) is substantially larger than any previous investigation of the topic (N1 = 91, N2 = 243). The studies were designed independently by research groups in Europe and the US, and both investigated testosterone’s effects on men’s willingness to compete, confidence, and risk-taking—dimensions of economic behavior that are theoretically linked to the Challenge Hypothesis, show robust sex differences, and predict important real-life outcomes such as career choice. We find no evidence for effects of testosterone on any of the behavioral tasks studied across the two experiments, with effect point estimates that are small and inconsistent. The studies had 90% statistical power to detect effects that are larger than d = 0.68 and d = 0.42 respectively, and equivalence tests confidently reject effects that are greater than these magnitudes. Our findings cast doubt on the proposition that testosterone is a meaningful causal driver of the stereotypically “masculine” dimensions of economic behavior studied, and suggest that even if true effects existed, detecting them experimentally would be challenging.