Going To Extremes, By Cass R Sunstein

Why birds of a feather should try flying apart

Some aspects of modern life can make you lose the will to live. Of all the bad trips new tech invites us to take, none feels more hellish than the website "discussion thread" on any hot topic of the day. Who let these rabid dogs out? Why does online "debate" so often leave the browser with a turned stomach and a soiled soul? Because, perhaps, networked shouting-matches that encourage players to cuddle their imaginary friends and demonise their equally disembodied foes bring to a peak the dynamics of "group polarisation" explored in this timely and absorbing book.

Cass Sunstein, professor of law at Harvard, broke through into the transatlantic policy limelight with his book Nudge (co-authored with David Thaler). It caught the imagination of politicians and pundits with its recipes for softly-softly changes to behaviour that went beyond the "stick or carrot?" options. In Going to Extremes, he again expresses a longing for a culture of civility, and an anxiety about tastes and trends that push people violently apart.

This book collates many studies of group behaviour, from juries who set damages for corporate malpractice to the mindset of students experimentally divided into prison "guards" and "inmates". All show that "like-minded enclaves" of folk who think the same way will tend to charge towards ever-more polarised opinions – and ever-more drastic actions. "If birds of a feather are flocking together, extreme movements are to be expected". Internet rage reveals both that people "appear to be hearing more and louder versions of their own views", and that mere exposure to another side of the story will not help to modify beliefs if the setting favours polarisation not dialogue.

Sunstein backs his case by a bulging folder of case studies – from the "interactive echo-chamber" of jihadi websites to the sorry spectacle of George W Bush's cabinet before the Iraq war: a blinkered "like-minded enclave" hobbled by "extremism, confidence and uniformity". The hate-fest currently directed against the NHS in Britain by the group-hugging US right would fill a meaty chapter in any subsequent edition. In contrast, Sunstein fashionably praises Abraham Lincoln's divergent, quarrelling "Team of Rivals".

He argues that dissent and diversity within groups pay dividends. Literally so: a report suggests that "the highest performing companies have extremely contentious boards". Enron, conversely, suffered terminally from the "crippled epistemology" that leads herd-thinking organisations to shut out all unwelcome evidence.

As he well knows, Sunstein's whole thesis rather begs the question of what we mean by "extremism", and why we should try to avoid it. Although no one could dispute that "humility and curiosity help to ensure better decisions", truth and justice do not always lie in middle-ground moderation according to the standards of the time.

Belatedly, he discusses some of the many moments in history when group polarisation has proved to be "highly desirable". From the end of apartheid in South Africa and the downfall of Soviet Communism back to the American Revolution itself, the "extremist" case has often proved correct. Less than two years ago, in snowy Iowa, a "polarised" tilt towards the most "extreme" choice among potential Democratic nominees started the "social cascade" (another key term) that led to the Obama presidency. And, boy, was most the planet grateful that it did.

Going to Extremes acknowledges all that. Yet it also paces around the borders of a "like-minded enclave" itself, unwilling to observe the scenery beyond. A mainstream worshipper of the American constitution and its wisdom, Sunstein ends with a paean to US "checks and balances" that speaks volumes about his own perspective. He appears to bracket climate-change activists and climate-change deniers as equal and opposite "extremists". Bizarrely, he assumes that US network news shows have enough of the "architecture of serendipity" he admires to give TV viewers a broad, balanced picture. Sunstein means well, writes clearly and stands on the side of the reasoning angels. But this amiable voice from the middle of the road of Main Street USA sometimes seems to be speaking from inside a bubble of its own.