According to Freud, the last of the three structures to develop is the super-ego. The super-ego has two main functions, both based on built-in reinforcement processes: 1) to reward individuals for acceptable moral behavior and 2) to punish actions that are not socially sanctioned by creating guilt. The super-ego thus represents the internalization of moral codes and is often called one's "conscience." The super-ego opposes the expression of unacceptable impulses rather than merely postponing them as does the ego.