The Swiss psychiatrist Carl Gustave Jung (1875-1961) was one of Freud's closest collaborators until he broke off to form his own school of analytical psychology.

While clearly grounded in Freudian psychoanalysis, Jungian analytical psychology moves away from the dominance of libido and toward a mystical understanding of the human unconscious.

Interestingly, Jung came from a long line of clergymen. His father was a minister in the Swiss Reformed Church.

Unlike Freud Jung divided the unconscious into the personal unconscious and the collective unconscious. The personal unconscious contained personal experience that had slipped out of consciousness, due eiter to simple forgetting or repressing. The collective conscious, however, held the entire, evolutionary heritage of humanity. It contained the entire library of our typical reactions to universal human situations. It was not limited to the individual's life but encompassed the great, impersonal truth of existence.

The Meyers-Briggs test is a well known personality test that is often use in the workplace to identify employees' different personality styles. This test uses all three polarities mentioned above:

1. Extroversion - Introversion
2. Thinking - Feeling
3. Intuition - Sensation

Extroversion is also measured on scales associated with the Five Factor Model of personality, such as the NEO personality inventory. This test, formulated to identify dimensions of personality in non-pathological adults, uses 40 items to quantify five areas:

1. Neuroticism
2. Extroversion
3. Openness to Experience
4. Agreeableness
5. Conscientiousness