The ego, the superego and the id

Freud explained his famous model for brain function in the 1927 publication, The Ego and the Id. Since then, the theory has been explained with reference to a horse and chariot:

The id is the "horse". It is the unevolved instinctive part of our brain, responsible for the urges and desires we try to repress.

The ego is the "driver" of the chariot, and the rational part of our brain. It is able to guide the id, but never has full control - just as the driver is aware that if the horse wants to go in a different direction, he is ultimately powerless to stop it.

The superego is the chariot driver's father, sitting behind him, pointing out his mistakes. It is the part of our brain responsible for criticism and moralising.

Freud believed that, as babies, all our behaviour is ruled by the id, because this is where our basic survival instincts are located, and where our desire for pleasure-seeking comes from. As we get older, our ego develops and is shaped by influences in our environment.

Our concept of the ego has changed since Freud's use: when we talk of someone being egotistic or having ego-damage, we are usually referring to their self-esteem, but Freud's definition simply meant the conscious part of our brain. Similarly, when we describe someone as having a big ego, we might be referring to their self interest, but according to Freud's theory it might be more correct to describe them as having a big id.