Extraversion and introversion

The trait of Extraversion-Introversion is a central dimension of human personality. Extraverts (sometimes called "extroverts") are gregarious, assertive, and generally seek out excitement. Introverts, in contrast, are more reserved, less outgoing, and less sociable. They are not necessarily asocial, but they tend to have smaller circles of friends, and are less likely to thrive on making new social contacts.

The terms introversion and extraversion were popularized by Carl Jung. Virtually all comprehensive models of personality include the trait. Examples include Eysenck's three factor model, the Big Five personality traits, and the Myers Briggs Type Indicator.

Definitions
Extraversion is "the act, state, or habit of being predominantly concerned with and obtaining gratification from what is outside the self". Extraverts tend to enjoy human interactions and to be enthusiastic, talkative, assertive, and gregarious. They take pleasure in activities that involve large social gatherings, such as parties, community activities, public demonstrations, and business or political groups. An extraverted person is likely to enjoy time spent with people and find less reward in time spent alone.

Introversion is "the state of or tendency toward being wholly or predominantly concerned with and interested in one's own mental life". Introverts tend to be quiet, low-key, deliberate, and relatively non-engaged in social situations. They take pleasure in solitary activities such as reading, writing, watching movies, inventing, and designing. An introverted person is likely to enjoy time spent alone and find less reward in time spent with large groups of people (although they may enjoy one-to-one or one-to-few interactions with close friends).

Although many people view being introverted or extraverted as a question with only two possible answers, levels of extraversion in fact fall on a normally distributed bell curve, with most people falling in between the two extremes. Ambiversion is a term used to describe people who fall more or less directly in the middle and exhibit tendencies of both groups. An ambivert is normally comfortable with groups and enjoys social interaction, but also relishes time alone and away from the crowd.

Jungian theory
According to Carl Jung, introversion and extraversion refer to the direction of psychic energy. If a person’s energy usually flows outwards, he or she is an extravert, while if this energy normally flows inwards, this person is an introvert. Extraverts feel an increase of perceived energy when interacting with large group of people, but a decrease of energy when left alone. Conversely, introverts feel an increase of energy when alone, but a decrease of energy when surrounded by large group of people.

Most modern psychologists consider theories of psychic energy to be obsolete. However, the concept is still sometimes used in the more general sense of "feeling energized" in particular situations. Jung’s primary legacy in this area may be the popularizing of the terms introvert and extravert to refer to a particular dimension of personality.

Eysenck's theory
Hans Eysenck described extraversion-introversion as the degree to which a person is outgoing and interactive with other people. These behavioral difference are presumed to be the result of underlying differences in brain physiology. Extraverts seek excitement and social activity in an effort to heighten their arousal level, whereas introverts tend to avoid social situations in an effort to keep such arousal to a minimum (see Causes below). Eysenck designated extraversion as one of three major traits in his P-E-N model of personality, which also includes psychoticism and neuroticism.

Eysenck originally suggested that Extraversion was a combination of two major tendencies, impulsiveness and sociability. He later added several other more specific traits, namely liveliness, activity level, and excitability. These traits are further linked in his personality hierarchy to even more specific habitual responses, such as partying on the weekend.

Measurement
Extraversion-introversion is normally measured by self-report. For example, a questionnaire might ask if you see yourself as someone who is the life of the party or who thinks before you talk (agreeing with the first statement would increase the extraversion score, while agreeing with the latter would push the score towards the introversion end of the scale). Or you may be presented with various sets of adjectives (for example: thoughtful, talkative, energetic, independent) and asked which most describes you and which describes you least.

Self-report questionnaires have obvious limitations in that people may misrepresent themselves either intentionally or through lack of self-knowledge. It is also increasingly common to use peer report or observation.

Causes
The relative importance of nature versus environment in determining the level of extraversion is controversial and the focus of many studies. Twin studies find a genetic component of .39 to .58. In terms of the environmental component, the shared family environment appears to be far less important than individual environmental factors (not shared by siblings).

Eysenck proposed that extraversion was caused by variability in cortical arousal; "introverts are characterized by higher levels of activity than extraverts and so are chronically more cortically aroused than extraverts". Because extraverts are less aroused internally, they require more external stimulation than introverts. This theory may be backed up by evidence that the brains of extraverts are more responsive to dopamine than those of introverts. Other evidence of this “stimulation” hypothesis is that introverts salivate more than extraverts in response to a drop of lemon juice.

One study found that introverts have more blood flow in the frontal lobes of their brain and the anterior or frontal thalamus, which are areas dealing with internal processing, such as planning and problem solving. Extraverts have more blood flow in the anterior cingulate gyrus, temporal lobes, and posterior thalamus, which are involved in sensory and emotional experience. This study and other research indicates that introversion-extraversion is related to individual differences in brain function.

Implications
Acknowledging that introversion and extraversion are normal variants of behaviour can help in self-acceptance and understanding of others. For example, an extravert can accept her introverted partner’s need for space while an introvert can acknowledge her extraverted partner’s need for social interaction.

Social psychologist David Myers found a correlation between extraversion and happiness; that is, more extraverted people reported higher levels of personal happiness. The causality is not clear: it is not known if extraversion leads to greater happiness, happier people become more extraverted, or there is some other factor such as social status that affects both. Possibly, the results reflect biases in the survey itself.

Extraversion, while typically perceived as socially desirable in Western culture, is not always advantageous. For many years, researchers have found that introverts tend to be more successful in academic environments, which extraverts may find boring. Extraverted youths are also more likely to engage in delinquent behavior.

Career counselors often use personality traits, along with other factors such as skill and interest, to advise their clients. Some careers such as computer programming may be more satisfying for an introverted temperament, while other areas such as sales may be more agreeable to the extraverted type.

Although neither introversion nor extraversion is pathological, psychotherapists can take temperament into account when treating clients. Clients may respond better to different types of treatment depending on where they fall on the introversion/extraversion spectrum. Teachers can also consider temperament when dealing with their pupils, for example acknowledging that introverted children need more encouragement to speak in class while extraverted children may grow restless during long periods of quiet study.

However, use of the terms may encourage pigeonholing or stereotyping. As noted above, extraversion is a continuum and most people have a mixture of both orientations in their personalities. A person who acts introverted in one scenario may act extraverted in another, and people can be taught to act “against type” in certain situations.