According to a recent study of military personnel conducted through the Walter Reed Army Institute of Research, introverts function better than extroverts when sleep deprived, which is a cortically de-arousing condition (because losing sleep makes us less alert, active, and energetic). Drowsy extroverts behind the wheel should be especially careful—at least until they increase their arousal levels by chugging coffee or cranking up the radio. Conversely, introverts driving in loud, overly arousing traffic noise should work to stay focused, since the noise may impair their thinking.
