Personality, perhaps more so than IQ, is what makes us unique; however, it is just as hard to pin down and define scientifically. Plato believed that personalities could be categorized into four temperaments, a concept that has some similarities to the modern view of personality traits.
Psychodynamic theories of personality emerged from Freud’s attempt to explain why we behave in certain ways as a struggle between the conscious and unconscious. They developed into mainstream theories of psychology in the second half of the 20th century. Personality studies differ on whether it is a stable characteristic or a dynamic process, but they agree that it is distinct from moods or emotions. Some believe personality traits are largely innate, others think environment and experience play an important role in shaping them. Different schools of thought also disagree about how far personality is genetically determined and how much is shaped through interaction with our environment.