How useful are the well-known and hotly contested categories of “male brain” and “female brain”? Among experts, nobody really questions that anatomical sex differences in the brain exist. But since the advent of brain science, the scientific community has been divided over how many differences there are, which ones have been definitively proven, how large or small they are, and what they actually mean.

Humans generally don’t have brains with mostly or exclusively “female-typical” features or “male-typical” features. Instead, what’s most common in both females and males are brains with “mosaics” of features, some of them more common in males and some more common in females.

Testosterone affects our brain, body, and behaviour. But it is neither the king nor the kingmaker—the potent, hormonal essence of competitive, risk-taking masculinity—it’s often assumed to be.