"In a fascinating study, Karen Stenner shows in The Authoritarian Dynamic that while some individuals have “predispositions” towards intolerance, these predispositions require an external stimulus to be transformed into actions. Or, as another scholar puts it: “It’s as though some people have a button on their foreheads, and when the button is pushed, they suddenly become intensely focused on defending their in-group … But when they perceive no such threat, their behavior is not unusually intolerant. So the key is to understand what pushes that button.”What pushes that button, Stenner and others find, is group-based threats. In experiments researchers easily shift individuals from indifference, even modest tolerance, to aggressive defenses of their own group by exposing them to such threats."