When I started out doing my Ph.D. research on the psychological impact of testosterone in women, I presumed that women with higher testosterone levels would be more aggressive. After all, the literature is full of studies demonstrating that rodents become more aggressive when administered testosterone. However, after measuring naturally occurring levels of testosterone in around 140 women, I found that testosterone did not directly cause an increase in any of a range of self-reported types of aggression (verbal aggression, physical aggression, etc.) or anger. The only finding of this kind was that women with polycystic ovary sydrome (PCOS), a condition in which raised testosterone is often seen, had significantly higher levels of withheld anger than controls. There was little evidence of a linear relationship between testosterone and aggression or anger, and my conclusion was that when testosterone causes unpleasantly masculinising symptoms in women (e.g. facial hair growth), the unpleasant symptoms cause withheld anger (also anxiety and depression), but testosterone does not have a direct impact on anger or other expressions of distress (Barry et al. 2018).