Sigmund Freud's psychoanalytic theory is centered on the belief that human behavior is influenced by an unconscious mind. Freud believed that every human has a collection of unconscious thoughts and urges, many of which are unpleasant, that influence behaviors and experiences.
Freud proposed that the mind consists of three parts: the id, the ego and the superego. He examined his patients' histories in detail, looking for events that he believed caused certain behavior.
Freud theorized that the id is present at birth and is responsible for a person's instincts; he categorized the id as part of the unconscious mind. The ego develops from the id, and ensures that the id's impulses can be expressed in an acceptable way. The ego is considered to be part of both the conscious and unconscious minds. Finally, the superego develops based on the morals an individual learns from parents and from society. It includes a person's sense of right and wrong and guides people's judgments.
Freud's theories have been criticized as being hard to measure and not being empirically tested. However, his work helped promote the idea that talking to a professional could help with mental issues. His work on personality development remains influential, and discussions of his theories remain popular among psychologists today.