by Cass Sunstein

As several commentators have suggested, we can't have much of a handle on ideological amplification without knowing what produces it. And as Steven Pinker has said, ideological amplification is just a special case of the broader phenomenon of group polarization. Here's why ideological amplification occurs. (I draw on decades of work in social science.) First, a group that is inclined in a particular direction will naturally come up with many arguments favoring its antecedent inclination. Arguments the other way will be fewer and weaker. So: If a group thinks that Pres. Bush is bad, it will hear lots of arguments about why he's bad, and few about about he isn't so bad. The same is true for critics of affirmative action, those concerned about abandoned hazardous waste sites, and many others. Second, people tend to go to the middle if they're not confident, and people get more extreme as their confidence increases. Corroboration by others increases confidence. So if people confirm your belief that Barack Obama should be president one day (and incidentally, he should!), you'll end up being firmer in your belief. Third, people care about their reputations and their self- conception. Suppose that you think of yourself as a moderate conservative. If you find yourself in a very conservative group, your usual views might make you seem pretty liberal, in that group. So: You might well shift in the conservative direction. Maybe you doubt that about yourself. But many people do shift in this way. These three mechanisms help explain why like-minded groups go to extremes. They also give us some clues to radicalism of various kinds--and also to the intelligence failures with respect to Iraq, the Enron fiasco, student left-wingism in the 1960s, stupid wars, appeasement, and real problems in the blogosphere. There are many possible solutions. A good start is a broader understanding of the phenomenon. If like-minded judges find themselves going to extremes, they might have some inoculation from an understanding of how and why ideological amplification occurs. Those in the legislative and executive branches, and ordinary citizens, could benefit from that understanding as well.