Testosterone eliminates strategic prosocial behavior in healthy males

Humans are strategically more prosocial when their actions are being watched by others than when they act alone. Using a psychopharmacogenetic approach, we investigated the computational and endocrinological mechanisms of such audience-driven prosociality. 187 male participants received either a single dose of testosterone or a placebo and performed a prosocial and self-benefitting reinforcement learning task. Crucially, the task was performed either in private or when being watched. Rival theories suggest that the hormone might either diminish or strengthen audience-depended generosity. We show that exogenous testosterone fully eliminated strategic, i.e., feigned, generosity and thus decreased submission to audience expectations. We performed reinforcement-learning drift-diffusion computational modeling to elucidate which latent aspects of decision-making testosterone acted on. The modeling revealed that testosterone compared to placebo did not deteriorate reinforcement learning per se...