In his 1920s work Psychological Types, Swiss psychiatrist Carl Jung popularized the terms "introverted" and "extroverted" when describing personality types. Introverts recharge by spending time alone and lose energy if they’re around people for long periods. Extroverts, on the other hand, gain strength from social interactions and actually exhaust themselves if they’re alone. Both types have their good and less-perfect qualities, so there’s no point in arguing which side would win in the Introvert VS. Extrovert battle.