Women who are open and trusting become more shrewd and less trusting when given testosterone

A study asked adult women to rate the trustworthiness of photos of strangers' faces. The hormone testosterone, normally linked to competition and dominance, made the most socially naive women more vigilant. But it had no effect on women naturally less trusting. Trust plays an important role in the formation and maintenance of human social relationships. Previous research has shown that the peptide hormone oxytocin increases trust in humans. Testosterone reduced interpersonal trust but only in subjects who were generally trusting, and therefore more at risk for deceit. Whereas in some mammals, testosterone is confined to motivating aggression in competition for status and resources, in humans the hormone seems to motivate for rational decision-making, social scrutiny, and cleverness, the apparent tools for success in a modern society. These findings are broadly consistent with previous research which showed that testosterone injections in men influenced aspects of their spatial and verbal abilities. There is growing evidence to suggest that testosterone has activational as well as organizational effects in men and women. It is possible that testosterone can activate changes in the way people perceive and think about aspects of the world.