The science

According to psychotherapist Dr. Marti Olsen Laney, introverts are more responsive to dopamine, a chemical related to human pleasure, than extroverts. Correspondingly, introverts generally use the acetylcholine neurotransmitter, a dopamine-like chemical that is influenced by turning inward. The acetylcholine pathway is the longer thinking path that introverts take; it passes through brain areas linked to reflection, planning, and determining memories.

Many may agree that there’s a preference towards outgoing and social people, and as Cain explained, “Here’s where the bias comes in; our most important institutions—our schools and our workplaces—they are designed mostly for extroverts and the extroverts’ need for lots of stimulation.”