Introverts are people who are over-sensitive to dopamine, so too much external stimulation overdoses and exhausts them. Conversely, extroverts can’t get enough dopamine, and they require adrenaline for their brains to create it. Extroverts also have a shorter pathway and less blood-flow to the brain. The messages of an extrovert’s nervous system mostly bypass the Broca’s area in the frontal lobe, which is where a large portion of contemplation takes place.