Content Warning: This section of the guide discusses self-harm.

Leila, a toddler, happily plays with other girls, but when her cousin Joseph arrives with his friends, they ruin her experience. Another unnamed female toddler treats a firetruck like a doll. Brizendine declares such play behavior is not caused by socialization, but results from neurological sex differences. She assumes the differences in female and male biology result in differences in their experiences of reality, citing the sex roles of non-human animals as support for her claim. Female fetuses usually have two X chromosomes, and they usually do not experience the prenatal surge in testosterone that typically occurs with male fetuses. These differences, Brizendine asserts, result in gendered behavior.

Brizendine bonded with Leila during Leila’s infancy and early childhood. She noticed that Leila, unlike Brizendine’s own son, made frequent eye contact. Initially worried, she later concluded that the difference was rooted in neurological sex differences. Female children, she states, will do anything to elicit an emotional response, just as an adult women will strive to win the approval of an “emotionally unavailable man” (38). Female children also comprehend social approval better than male ones, as seen in Leila’s good behavior while at a restaurant.