The traits of extraversion (also spelled extroversion) and introversion are a central dimension in some human personality theories. The terms introversion and extraversion were introduced into psychology by Carl Jung, although both the popular understanding and current psychological usage vary. Extraversion tends to be manifested in outgoing, talkative, energetic behavior, whereas introversion is manifested in more reflective and reserved behavior. Jung defined introversion as an "attitude-type characterised by orientation in life through subjective psychic contents", and extraversion as "an attitude-type characterised by concentration of interest on the external object".
Extraversion and introversion are typically viewed as a single continuum, so to be higher in one necessitates being lower in the other. Jung provides a different perspective and suggests that everyone has both an extraverted side and an introverted side, with one being more dominant than the other.