"In other words, it's clear that people love moms. But why? "The classic take is the Freudian one," says Peter Kanaris, a clinical psychologist and sex therapist who has been practicing for 35 years. "The child seeks to connect sexually with the opposite-sex parent—so the male child [seeks to connect] with the mother. What prevents us from seeking the mother is the fear of castration by the father. The [MILF] fantasy could be looked at, in a way, as conquering the castration anxiety—saying, 'I'm really going for the mother figure.

Another theory, Kanaris says, comes from the sex therapist Jack Morin, whose book The Erotic Mind established the concept of an individual's "core erotic themes." This is the idea that "for unknown reasons we develop a primary core sexual theme that will really act as a substantial turn-on throughout much of our lives," Kanaris says. An interest in moms might be a "primordial" core erotic theme for some people."