Personality psychology studies enduring psychological patterns of behavior, thought and emotion, commonly called an individual's personality. Theories of personality vary between different psychological schools. Trait theories attempts to break personality down into a number of traits, by use of factor analysis. The number of traits have varied between theories. One of the first, and smallest, models was that of Hans Eysenck, which had three dimensions: extroversion introversion, neuroticism emotional stability, and psychoticism. Raymond Cattell proposed a theory of 16 personality factors. The theory that has most empirical evidence behind it today may be the "Big Five" theory, proposed by Lewis Goldberg, and others.

A different, but well known approach to personality is that of Sigmund Freud, whose structural theory of personality divided personality into the ego, superego, and id. He utilized the principles of thermodynamics metaphorically to explain these three distinctive and interacting tripartite divisions. In 1923 Freud published the ground breaking book: "The Ego and the Id" in which he named and identified the functioning psychodynamics of human personality. This theory has been used in modern psychology paradigms such as Transactional Analysis. However, Freud's theory of personality has been criticized by many, including many mainstream psychologists.

Labels: Psychology