Abstract
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. Here, we report two randomised double-blind placebo-controlled testosterone administration experiments (N1 = 91, N2 = 242) designed independently by researchers in Europe and the US. Both experiments investigated the effect of a single dose of testosterone (at 4 h and 21–24 h post administration) on men's willingness to compete, confidence, and risk-taking in economic tasks. We estimate weak treatment effects that are statistically indistinguishable from zero for all behavioral outcomes across the two experiments. Our findings cast doubt on the proposition that there is an overall effect of a single dose of testosterone administration on the dimensions of economic behavior studied. If such effects existed, detecting them experimentally via pharmacological studies would require very large samples. We discuss different explanations for our results, including the possibility that context and individual difference factors moderate the effects.
•Two studies tested testosterone administration’s effects on willingness to compete, confidence, and risk-taking in men.•One of the studies feature the largest sample size to date on this topic, enhancing statistical power and reliability.•The two experiments employ different administration protocols and draw samples from distinct populations, improving the generalizability of our findings.•We find weak and statistically insignificant effects of testosterone administration on any of the behavioral tasks.