Many people may not be aware that women have the sex hormone testosterone too. It's not just a man's hormone, though men have far higher levels of testosterone than we women do.
In a study published in the journal Proceedings of the National Academy of Sciences, women were dosed with higher levels of testosterone. The result was that those women in the study who by nature were more "socially naive", became less inclined to be trusting.
"The study also adds support to the idea that testosterone influences human behavior, not necessarily by increasing aggression, but by motivating people to raise their status in the social hierarchy or become more socially dominant."
The researcher speculate that higher levels of the sex hormone testosterone may make a person more watchful and vigilant, and less inclined to be trusting. It may make them more competitive, and to be successful in competition, it pays not to believe everything you hear.