From the article: New research provides evidence that narcissism moderates the relationship between testosterone and generosity in men. The study, published in Hormones and Behavior, found that the most generous men tended to be low in endogenous testosterone and simultaneously low in narcissism. Unexpectedly, however, the researchers also found that heightened testosterone levels in combination with heightened narcissism was a significant positive predictor of generosity.

“Physiological changes constantly occurring in living organisms are interconnected with behavioral outcomes in many intricate and fascinating ways,” said co-author Magdalena Ziemiańska, a PhD student at the Polish Academy of Sciences. “We were curious to examine how a normal (i.e. baseline) level of testosterone is linked to social behavior.”

“A simple economic game was applied, in which the participants’ task was to divide points between themselves and a stranger,” Ziemiańska explained. “We wanted to check if a popular belief, derived from animal studies, that high testosterone level is connected with competitive, antisocial behaviors is true in humans.”