The antidote for terrorism and other extremes?

... In his textbook on social psychology, David Myers writes, "Terrorism does not erupt suddenly. Rather, it arises among people whose shared grievances bring them together. As they interact in isolation from moderating influences, they become progressively more extreme. The social amplifier brings the signal in stronger. The result is violent acts that the individuals, apart from the group, would never have committed."

It's not just groups on the right that polarize, nor are Republicans the only people to gather in like-minded groups. For the past 30 years, Americans have been sorting themselves into politically like-minded neighborhoods, churches, and clubs. Matching like with like has been often been entirely intentional. Ministers have been taught to attract new members according to the "homogenous unit principle" of church growth. (One book in the church growth literature is titled Our Kind of People.) Subdivisions have designed for certain cultural types—a Christian school in one section, a Montessori school in another.

The antidote to group polarization is mixed company. Cass Sunstein and David Schkade reviewed the rulings from three panels from the U.S. Court of Appeals. They found that when the panels consisted of all Republican or all Democratic appointees, the rulings were more extreme than when the panels had members of both parties. Mixed panels produced more moderate judgments.

The lesson is pretty clear. Mixed company moderates; like-minded company polarizes. Heterogeneous communities restrain individual excesses. Homogeneous communities march toward the extremes. - slate