It is somewhat puzzling why this book should garner such favorable reviews. It presents a great deal of evidence, mainly based upon a range of experiments carried out by social psychologists 20 to 30 years ago. These demonstrate that groups do not lead members to moderate their beliefs and attitudes through group discussion. Rather, there is a tendency for people, following discussion, to move to positions that are more extreme than those which they held prior to participation in the group. But there appears to be little that is new or surprising in the material presented. The proneness of people to be led to extremity through group participation has been known for some time. We also have a lot of evidence about the conditions that may obviate this effect and prevent polarization.
It is attractive, perhaps, that commentators are able to understand why the creation of groups of like-minded people, created to make decisions, such as committees of government, or panels of federal court judges, can lead to extremity rather than moderation. It is interesting to see that there are social forces that can lead to extremism and we need not always assume some characteristic of the people, their personality or their pathology, leads to extremity. This is a service performed by this book. But it may be a message that now itself needs moderation.
There is evidence becoming available that suggests that the formation of groups of people who form groups with different compositions, among such differences being variations in the average extremity of the opinions held, can lead not to polarization but rather to moderation. These studies are not done with college students or with ideologically extreme individuals, as has been the case with the bulk of the evidence presented by Sunstein. They are carried out with a range of voters across the political spectrum, everyday people leading everyday lives.
So, we must be wary of the evidence. The message of the book is that like-mindedness can lead to polarization of belief. That, as something which makes us question fundamental beliefs about personality and about the power of groups, is important. But the book also perhaps is speaking to the same kind of audience; we read what we like and already believe and we are reinforced in our beliefs and are led to a greater degree of extremity. We also need to read and to be exposed to evidence that is contrary to what we think or what we want to believe. Challenge can lead to moderation. In these times of increasing extremity of opinions about matters of the causes and effects of climate change, of changes in health care policy, on decisions about troop commitments etc, information that can affect the character of debate that can moderate rather than polarize would be better.