libido

Meaning: In Freud's psychoanalytic theory, libido is the psychic energy behind the life instincts (Eros). It is broadly pleasure-seeking, with "sexual" used in a wide sense, not only sexual desire. It originates in the id, which seeks immediate gratification. The ego and superego regulate how it is expressed, and conflict among the three can be handled with defense mechanisms. Libido is focused on different erogenous zones as a child develops: oral, anal, phallic, latency, genital. If needs at a stage are frustrated or overindulged, some libido may stay tied to that stage, called fixation, which the theory links to later personality traits.

On the MCAT: A passage or question stem describes an adult behavior (nail biting, smoking, extreme neatness or messiness) and asks which stage the person is fixated at. Other questions ask which part of the personality is the source of libido (the id), or ask you to contrast Eros and libido with Thanatos, the death instinct linked to aggression.

Common confusion: Students equate libido with the everyday sense of sex drive. In Freud's account it is the general energy of pleasure-seeking, and it is the id's energy, not the ego's; the ego only manages it. Jung used the word differently, for general psychic energy.