Newborn boys and girls, untouched by the forces of gender socialization, supposedly show stereotypical preferences for looking at hanging mobiles versus faces, respectively. And, we are told, girls with congenital adrenal hyperplasia, who are exposed to unusually high levels of testosterone in the womb, prefer “boy toys.”

But these findings are far less compelling than they appear. For instance, if the preference of female Rhesus monkeys for stuffed animals shows that love of dolls is “innate” in girls, what do we make of the fact that the favorite toy of male vervet monkeys was a stuffed dog, which they played with more than a third longer than a toy car?

Recent experiments, more methodologically rigorous than the much-cited mobiles versus faces newborn study, found no sex differences in the preferences of babies for looking at objects versus faces. Both preferred the latter to an equal extent. And girls with CAH—born with atypical or masculinized genitalia who undergo intensive medical and psychiatric intervention and have physical characteristics inconsistent with cultural ideals of feminine attractiveness—may be more willing to play with “boy toys” because of unconsidered effects of the condition on their psychosexual development, rather than because their brains have been “wired for wheels.”