Testosterone eliminates strategic prosocial behavior

Humans are strategically more prosocial when their actions are being watched than when they act alone. Using a psychopharmacogenetic approach, we investigated the computational and endocrinological mechanisms of such audience-driven prosociality. 187 participants received either a single dose of testosterone or a placebo and performed a prosocial and self-oriented reinforcement learning task. Crucially, the task was performed either in private or when being watched. Rival theories of testosterone’s role in status-seeking suggest that the hormone might either strengthen or diminish audience-depended generosity. We show that exogenous testosterone strongly decreases submission to audience expectations, full eliminating strategic i.e., feigned generosity. We next performed reinforcement-learning drift-diffusion modeling to elucidate which latent aspects of decision-making testosterone acted on. Computational modeling revealed that testosterone compared to placebo did not deteriorate reinforcement learning per se, rather, in presence of the audience, the hormone impacted the expression of the learned information into behavioral choice. These results indicate that instead of deceptively increasing socially desirable behavior, testosterone boosts honest forms of status-seeking, arguably by impacting the motivational link between learned values and behavior.