Last night on facebook, a friend posted an article titled 10 Myths About Introverts. The article begins by summarizing some new research which shows that the tendency to be extroverted or introverted isn't a learned behavior or a strange intangible quality you're born with. It's actually the result of a reaction in your brain to the chemical dopamine. Your body naturally produces dopamine through external stimulation and adrenaline rushes. Extroverts' brains crave dopamine in large doses, while introverts can only comfortably handle small quantities of dopamine at a time. The article itself goes into more technical sciencey-sounding details, before listing off the author's favorite 10 myths about introverts.
Before you go on, click on the link above to read the original article, so we're all on the same page. It's not that long.