Introversion is a basic personality style characterized by a preference for the inner life of the mind over the outer world of other people. One of the Big Five dimensions that define all personalities, introversion sits on a continuum at the opposite end of which is extroversion. Compared to extroverts, introverts enjoy subdued and solitary experiences.

Introverts do not fear or dislike others, and they are neither shy nor plagued by loneliness. A crowded cocktail party may be torture for introverts, but they enjoy one-on-one engagement in calm environments, which is more suited to the make-up of their nervous system. Evidence suggests that, unlike with extroverts, the brains of introverts do not react strongly to viewing novel human faces; in such situations they produce less dopamine, a neurotransmitter associated with reward.