Despite feminists’ best efforts, many people today believe that inequality between the sexes is natural, not cultural. They will often point to the behavior, clothing, or play of girls and boys to prove this; or they will point to hormones, like testosterone, as evidence that men are inherently violent, sexually aggressive, or more adventurous than women. Cordelia Fine’s work throws a wrench into all of that. In her new book, Testosterone Rex: Unmaking the Myths of Our Gendered Minds, Fine paints a far more complex picture of brains and the impacts of hormones on human beings.

Fine is a psychologist and is also the author of Delusions of Gender: How Our Minds, Society, and Neurosexism Create Difference. I spoke with her over the phone last week.