Among many revolutionary psychological ideas, Sigmund Freud introduced the idea od the Id, Superego and Ego. The Id is the basic instincts, or what people inherently want to do. This is driven by sex and aggression. The Superego is the morals which keep the Id in check. Finally, the Ego is in charge of everything, personality, decision making and interacting with the real world.
What interests me is the extent to which this idea is modeled in popular culture. Many movies or works of art portray the idea of a person dealing with a a tiny devil on one shoulder and an angel on the other while trying to make a difficult decision.
This idea has been portrayed in many movies and tv shows, including the Simpsons multiple times as a reoccurring theme. In a recent Dexter episode, Dexter battles with inner voices attempting to decide between releasing his raw desire to kill, vs. his desire to not get caught and do things correctly. My personal favorite example is from a Seinfeld episode in which Jerry is very repulsed by a girl mentally, but loves the sex. The episode portrays Jerry's brain playing chess with his penis to determine what the outcome of his relationship will be.
(skip to 3:08 for the chess game)
In this scene, Jerry's penis represents the Id, while the brain represents the Superego.
Freud's idea of the Id, Ego and Superego are so represented in popular culture because of the comedic potential of this idea. People find it very humorous to imagine a battle going on inside their minds. Perhaps people like to imagine that there really is a voice inside that tells them to do the instinct, even if it is wrong. They like the idea that a part of them really wants to what is considered wrong. People also want to imagine that there exists a voice that knows what to do. If there are voices telling people what to do, they can better trust that the right decision will be made in the end.