Our formulations of internalization are based on a single fundamental assumption: The mechanisms which instigate psychological growth at one level of functioning are precisely those which ensure it at any other level—from birth through senescence. The individual's major existential task throughout the life cycle is one of continued separation-individuation, which is accomplished through progressive internalizations of need-gratifying

aspects of relationships with significant others. We extracted from various theories of normative development what we believe to be the underlying mechanisms of the internalization process: the establishment of a gratifying involvement, the experience of incompatibility in the relationship, and internalization resulting in increased psychological differentiation and individuation. Psychological growth continues as these elemental steps occur, in hierarchical spirality, over and over again throughout the course of the entire life cycle.