'Paraphilic infantilism' is usually shortened to 'infantilism.' This can lead to some misunderstandings, since 'infantilism' can also mean 'lacking development.' Mental retardation involves never having achieved an average maturity, in contrast to adult babies, who actively set their maturity aside. In turn, psychosexual infantilism, a term coined by Freud, referred to those who haven't "matured" through the psychosexual stages into heterosexuality. Psychosexual infantilism includes paraphilic infantilism as well as other paraphilias and sexual orientations. Finally, regression is a broad term with many meanings. Adult babies regress, but those who regress aren't necessarily adult babies.