NOTA: Le definizioni qui riportate provengono da diverse fonti non tutte coerenti e a volte contraddittorie. Alcune rivelano pregiudizi e associazioni di idee che nulla hanno di scientifico e che andrebbero demistificate.
La psicologia ha identificato numerose tipologie di personalità, ma l'unico dato su cui convergono gli psicologi è l'universalità del tratto dualistico estroversione/introversione.
La coscienza estroversa si interfaccia con il mondo esterno, su cui è affacciata attraverso i sensi, mentre la coscienza introversa si interfaccia con il mondo interno, che viene recepito come 'sede' della propria identità, e filtra quindi attraverso il mondo interno i dati esterni, e dà loro significati soggettivi.
Questa distinzione è stata operata inizialmente dal psichiatra e psicoanalista Carl Jung nella sua famosa opera Tipi psicologici (Psychologische Typen, anno di pubblicazione 1921), anche se oggi l'introversione si è venuta a configurare comunemente come un tratto negativo della personalità, mentre l'estroversione viene vista come un tratto positivo. In particolare nell'introverso viene vista una persona chiusa, solitaria, poco comunicativa, timida ed insicura. Giudizio spesso condiviso anche dagli stessi introversi, che vivono con una dolorosa consapevolezza la propria diversità rispetto agli altri.
The trait of extraversion-introversion is a central dimension of human personality. Extraverts (also spelled extroverts) tend to be gregarious, assertive, and interested in seeking out excitement. Introverts, in contrast, tend to be more reserved, less outgoing, and less sociable. They are not necessarily loners but they tend to have smaller circles of friends and are less likely to thrive on making new social contacts. Introverts are less likely to seek stimulation from others because their own thoughts and imagination are stimulating enough.
The terms introversion and extraversion were first popularized by Carl Jung. Virtually all comprehensive models of personality include these concepts. Examples include Jung's Analytical psychology, Eysenck's three-factor model, Cattell's 16 personality factors, the Big Five personality traits, the four temperaments, the Minnesota Multiphasic Personality Inventory, the Myers Briggs Type Indicator, and Socionics.
Extraversion and introversion are generally understood as a single continuum. Thus, to be high on one is necessarily to be low on the other. That said, people fluctuate in their behavior all the time, and even extreme introverts and extraverts do not always act consistently.
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 more reserved and less assertive in social situations. They often take pleasure in solitary activities such as reading, writing, drawing, and using computers. The archetypal artist, writer, sculptor, composer, and inventor are all highly introverted. An introvert is likely to enjoy time spent alone and find less reward in time spent with large groups of people, though they tend to enjoy interactions with close friends. They prefer to concentrate on a single activity at a time and like to observe situations before they participate. Introverts are easily overwhelmed by too much stimulation from social gatherings and engagement. They are more analytical before speaking.
Introversion is not the same as shyness. Introverts choose solitary over social activities by preference, whereas shy people avoid social encounters out of fear.
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. Politics, teaching, sales, managing, and brokering are fields that favor extraversion. An extraverted person is likely to enjoy time spent with people and find less reward in time spent alone. They tend to be energized when around other people, and they are more prone to boredom when they are by themselves.
Although many people view being introverted or extraverted as a question with only two possible answers, most contemporary trait theories (e.g. the Big Five) measure levels of extraversion-introversion as part of a single, continuous dimension of personality, with some scores near one end, and others near the half-way mark. 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.