Ego functions
The four ego functions postulated by C.G. Jung in Archetypes of the Collective Unconscious are Sensation, Thinking, Feeling, and Intuition. Jung suggested that people start life developing one of these four ego functions, and at various stages throughout their life may develop others, the undeveloped ones having less effect on their cognition. Typically, the second ego function might become developed during adolescence, and the development of a third accounts for mid life crises.