As the introverts have a naturally high level of activity in the anterior part of the brain, they are therefore not in need of significant extraneous stimuli. You could say that introverts are by nature is more or less chronically preoccupied by their own cognitive processes. Extroverts, by contrast, live in a form of chronic “activity deficit” and must therefore seek external stimuli to maintain a certain level of activity and function in their brains. – You can say that extroverts need stronger influences before the brain understands the message (e.g. more lemon juice to produce the same response), and so a room without stimulants provokes the extrovert to produce his own entertainment.