“Testosterone has far less to do with aggression than most assume. Within the normal range, individual differences in testosterone levels don’t predict who will be aggressive. Moreover, the more an organism has been aggressive, the less testosterone is needed for further aggression. When testosterone does play a role, it’s facilitatory—testosterone does not 'invent' aggression. It makes us more sensitive to triggers of aggression. Also, rising testosterone levels foster aggression only during challenges to status. Finally, crucially, the rise in testosterone during a status challenge does not necessarily increase aggression; it increases whatever is needed to maintain status. In a world in which status is awarded for the best of our behaviors, testosterone would be the most prosocial hormone in existence.”