Taking testosterone makes women less trusting, according to a new study. Researchers took a group of 24 women, showed them images of strangers' faces, and asked them to rate their trustworthiness from -100 to +100. Half were then given testosterone, which made their rankings fall an average 10 points, while the other half, given a placebo, remained constant.
Researchers theorize that since historically women have relied on being cooperative and sociable for their survival, they evolved to be more trusting than men, who have more often had to fight, physically and socially. “In the same way that we have evolved capacities to help others, we have also evolved capacities to deceive and cheat,” one psychologist explains to the Daily Telegraph. “Testosterone increased social vigilance in trusting humans, presumably to better prepare them for hard-edged competition.”