Testosterone Found To Decrease Women’s Trust of Men

We like to believe that we trust people based on objective evidence, but at the very least when sizing up someone new, the brain has to make split-second determinations about how trustworthy someone is. It turns out that hormones play an important role in encouraging both trust and distrust. A new study from Dutch researchers concludes that testosterone makes women less likely to trust men.

Researchers asked women to judge the trustworthiness of a set of photographs of men’s faces both before and after being given a drop of liquid testosterone. The overall level of trust went down substantially after the women received the testosterone.

Most significantly, the effect of the testosterone was greatest in those women who were most trusting to begin with.  Women who were more cautious about trusting the men had little change in their level of trust after receiving the testosterone.

Although men are known for having higher levels of testosterone, the hormone is naturally present in women as well and is known to increase women’s sex drive. In fact, women’s testosterone levels normally spike just before they ovulate.  Scientists speculate that the pre-ovulation surge of testosterone might serve an evolutionary purpose, since by decreasing trust, it would allow women to more carefully evaluate a sexual partner at the time when she is most fertile–and, presumably, lead her to make better choices.

Before concluding that anyone who doesn’t trust you must have too much testosterone, keep in mind that the research did not investigate the effects of surges of testosterone on men’s levels of trust or the role hormones play in trust in ongoing relationships. Trusting someone you know only from a picture is a different matter from trust in the context of a long history of friendship, romance, or family.

Earlier research showed that a hormone called oxytocin plays an important role in making people willing to trust strangers. For the average person, the take-home message might be that trusting our “gut instinct” about strangers might not be a great idea after all, since hormones play such a large role in the initial reaction of trust or distrust.

The testosterone study was reported in the Proceedings of the National Academy of Sciences.