Even though none of the volunteers had any idea what they were inhaling, those who were exposed to the fear sweat showed considerably more activity in their brains’ fear-processing zip codes (their amygdalae and hypothalami) than those who’d breathed the exercise sweat. In addition, on an emotion recognition task, volunteers who had inhaled the fear sweat were 43 percent more accurate at judging whether a face bore a threatening or neutral expression than those who’d gotten the workout sweat.
