This is not fringe science: One of Hibbing's pioneering papers on the physiology of ideology was published in none other than the top-tier journal Science in 2008. It found that political partisans on the left and the right differ significantly in their bodily responses to threatening stimuli. For example, startle reflexes after hearing a loud noise were stronger in conservatives. And after being shown a variety of threatening images ("a very large spider on the face of a frightened person, a dazed individual with a bloody face, and an open wound with maggots in it," according to the study), conservatives also exhibited greater skin conductance—a moistening of the sweat glands that indicates arousal of the sympathetic nervous system, which manages the body's fight-or-flight response.

It all adds up, according to Hibbing, to what he calls a "negativity bias" on the right. Conservatives, Hibbing's research suggests, go through the world more attentive to negative, threatening, and disgusting stimuli—and then they adopt tough, defensive and aversive ideologies to match that perceived reality.