Freud believes that small boys and girls react differently to the discovery of the opposite sex’s genitalia. Freud argues that for many small boys, a girl’s lack of penis is a troubling discovery, leading to the boy worrying that the girl has “lost” her male genitalia, and that the same could happen to him. Freud calls this fear of losing the male genitalia the castration complex.

Freud defines a fetish as an abnormal fixation on a part of the body not usually considered sexual (e.g., feet, hair), or an object connected in some way with the body of the desired person (such as their underwear). Freud suggests that there exists a degree of fetishization even in normal relationships—especially in the early stages of courting, where sexual contact may be limited or forbidden. Like other perversions, fetishization can become an obsessive fixation and may interfere with the pursuit of normal sexual ends.

Since a child’s first strong emotional attachment is to his or her parents, Freud believes that the child’s first sensations of bodily pleasure are connected to the love and care it receives from its primary caregiver, especially the mother figure (through acts such as breastfeeding, for example). In normal sexual development, the child transfers his or desire to persons outside of the family unit.