ego

Meaning: In Freud's psychoanalytic theory, the ego is the part of personality that deals with reality. It follows the reality principle: it delays or redirects the id's demands for immediate pleasure until a realistic, acceptable way to meet them exists, while also answering to the superego's internalized moral standards. When these pressures conflict, the ego faces anxiety and may use defense mechanisms such as repression, denial, projection, displacement, and rationalization. It works at conscious, preconscious, and unconscious levels.

On the MCAT: A vignette describes a wish, a moral rule, and a behavior, and you identify the structure. Wanting a coworker's lunch but waiting and buying your own shows the ego; the raw urge is the id; guilt or a rigid rule is the superego. Defense mechanisms are ego functions.

Common confusion: In everyday speech, a "big ego" means conceit, but in Freud's model the ego is the rational mediator, not vanity. It is also not the conscience, which belongs to the superego, and it negotiates with the id rather than eliminating its drives.