Beginning in the late nineteenth, and continuing through the twentieth century, Austrian physician Sigmund Freud outlined the first empirical theory of personality. The theory was based on observation of individuals and self-report of their childhood. The theoretical model was built on a three-part structure that included the id, ego and super-ego.
Freud described the id, ego and super-ego as divisions of an iceberg floating in water. The tip of the iceberg, above the water, is the ego, which is Latin for "I." The ego is fully above the water, in the conscious. This is the aspect of the self that people are aware of.
At the bottom of the iceberg, far beneath the water surface, is the id, which is Latin for "thing." The id is fully in the depths of the unconscious, the area of the self that is unknown. This is the majority of who individuals are, and it is concealed to them.
The super-ego, or "over-self," is the part that has developed through social culture. The super-ego is in the unconscious and conscious and includes the moral sense of good and evil.
Freud described a preconscious that exists just below the surface of the water. This includes aspects of individuals that they can be aware of but typically do not think about.
Psychodynamic personality tests are called projective tests. A projective test reveals the unconscious parts of an individual's personality. By projecting the unconscious into the conscious through words, the psychoanalyst interprets the words to gain an insightful picture of the patient's unconscious self.
Common projective tests include the Rorschach Inkblot, the Thematic Apperception Test, dream analysis and the free-association method.
Trait theory was pioneered by American psychologist Gordon Allport in the 1930s. Allport scanned the English dictionary and established a list of 4,500 descriptive words of personality that he called traits. These traits were later reduced to 32 dichotomous traits by Raymond Cattell. These 32 traits, known as the 16 Personality Factors, include warmth, reasoning, emotional stability, dominance, liveliness, rule-consciousness, social boldness, sensitivity, vigilance, abstractedness, privateness, apprehension, openness to change, self-reliance, perfectionism and tension.
In the 1990s, Costa and McCrae revised the list into the "Big-Five Personality Traits." These include openness, conscientiousness, extroversion, agreeableness and neuroticism.
The 16PF and the Big Five Personality Inventory are the two most widely used psychometric personality tests. The subject answers a 200- to 400-question test that is either fixed response, "yes" or "no," or a Likert scale response, "strongly agree" through "strongly disagree." The subject is then scored as high, middle or low for each of the traits, resulting in a personality profile.