In classical Freudian psychoanalytic theory, a child's identification with the same-sex parent is the successful resolution of the Oedipus complex (sometimes called the Oedipal complex) and of the Electra complex. This is a key psychological experience that is necessary for the development of a mature sexual role and identity. Sigmund Freud further proposed that boys and girls experience the complexes differently: boys in a form of castration anxiety, girls in a form of penis envy; and that unsuccessful resolution of the complexes might lead to neurosis, pedophilia, and homosexuality.