Psychologist Steven Pinker on the Decline of Violence

Steven Pinker, celebrated for his books on language and the workings of the mind, ventures into big history with his latest volume, "The Better Angels of Our Nature: Why Violence Has Declined." He unloads a truckload of evidence to argue that humans have been getting more peaceful, more cooperative and less murderous, on scales large and small, for quite some time. Among the reasons: civilization really has made us more civil. That might seem a surprising conclusion for a card-carrying evolutionary psychologist, but Pinker hasn't gone all liberal artsy on us. Historicity has a role to play, he says, but so do biology and game theory.