physiological investigations had revealed that extroversion was linked with resting states of low cortical arousal, introversion with high cortical arousal; this had sounded backward to Michel at first, but then he remembered that the cortex inhibits the lower centers of the brain, so that low cortical arousal allows the more uninhibited behavior of the extrovert, while high cortical arousal is inhibitory and leads to introversion. This explained why drinking alcohol, a depressant which lowers cortical arousal, could lead to more excited and uninhibited behavior.
