Psychology? It's all in the mind.
Basic personality types, according to the theories of Carl Gustav Jung. The introvert, who directs thoughts and feelings inward, is often shy, contemplative, and reserved. The extravert, who directs attention toward other people and the outside world, is usually outgoing, responsive, and aggressive. This typology is now regarded as simplistic because almost no one can be described as wholly introverted or extraverted.
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