Analytical psychology distinguishes several psychological types or temperaments.
The attitude type could be thought of as the flow of libido (psychic energy). The Introvert's flow is directed inward toward concepts and ideas and the Extravert's is directed outward towards people and objects. There are several contrasting characteristics between Extraverts and Introverts: Extraverts desire breadth and are action-oriented, while introverts seek depth and are self-oriented.
Research has shown that there may be a positive correlation between the Introversion/Extraversion types and health deterioration. Introverts may be more inclined to catatonic type schizophrenia and extraverts towards manic depression.
The often misunderstood terms extravert and introvert derive from this work. In Jung's original usage, the extraversion "is an outward-turning of libido",, whereas introversion is an inward-turning of libido. Everyone has both the intraversion and the extraversion mechanisms, and the collectively dominant type determines whether an individual is introvert or extravert.
According to Jung, the conscious psyche is an apparatus for adaptation and orientation, and consists of a number of different psychic functions. Among these he distinguishes four basic functions:
Thinking and feeling functions are rational, while sensing and intuition are nonrational. According to Jung, rationality consists of figurative thoughts, feelings or actions with reason—a point of view based on objective value, which is set by practical experience. Nonrationality is not based in reason. Jung notes that elementary facts are also nonrational, not because they are illogical but because, as thoughts, they are not judgments.
In any person, the degree of introversion/extraversion of one function can be quite different from that of another function.
Generally, we tend to favor our most developed, superior function, while we can broaden our personality by developing the others. Related to this, Jung noted that the unconscious often tends to reveal itself most easily through a person's least developed, inferior function. The encounter with the unconscious and development of the underdeveloped function(s) thus tend to progress together.
Early in Jung's career he coined the term and described the concept of the "complex". Jung claims to have discovered the concept during his free association and galvanic skin response experiments. Freud obviously took up this concept in his Oedipus complex amongst others. Jung seemed to see complexes as quite autonomous parts of psychological life. It is almost as if Jung were describing separate personalities within what is considered a single individual, but to equate Jung's use of complexes with something along the lines of multiple personality disorder would be a step out of bounds.
Jung saw an archetype as always being the central organizing structure of a complex. For instance, in a "negative mother complex," the archetype of the "negative mother" would be seen to be central to the identity of that complex. This is to say, our psychological lives are patterned on common human experiences. Interestingly, Jung saw the Ego (which Freud wrote about in German literally as the "I", one's conscious experience of oneself) as a complex. If the "I" is a complex, what might be the archetype that structures it? Jung, and many Jungians, might say "the hero," one who separates from the community to ultimately carry the community further.