APA Dictionary of Psychology

in the psychoanalytic theory of Melanie Klein, the internalized representation (see introjection) of the mother’s breast as nourishing and satisfying. According to Klein, the infant first experiences the mother and the nourishing breast as part-objects with positive qualities—the good breast—and negative qualities—the bad breast. Klein thought that the development of these internalized representations of the breast was the first manifestation of splitting.