Much of psychoanalytic theory has required modification since Sigmund Freud’s original work. Nonetheless, Freud’s concepts of the ego and the id have held up remarkably well over these past 100 years. The ego is the seat of the reality principle. It helps us adapt our wishes and urges to cold reality. The id, on the other hand, is the seat of our most primitive and animalistic desires. It is the source of our passions. As is suggested by Freud’s famous phrase “Where id was, there shall ego be,” the ego serves to control the id.

Surprisingly, modern neuroscience has completely supported this notion. The id can be equated with the limbic system, the seat of our emotions. The ego can be equated with the frontal lobe, or, more specifically, the pre-frontal cortex, which mediates cognition and behavioral control. Just as the ego serves to control the id, the frontal lobe serves to control the limbic system.