Echo chamber.

Photographer: Jeff Swensen/Getty Images

Sanders Writes a Chapter in the Behavioral Science Textbook

Cass R. Sunstein is a Bloomberg View columnist. He is the author of “The World According to Star Wars” and a co-author of “Nudge: Improving Decisions About Health, Wealth and Happiness.”
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Bernie Sanders won't be the Democratic presidential nominee, yet so far he refuses to concede to Hillary Clinton, pledging to "continue to fight for every vote and every delegate we can get.” This is more than just stubbornness: Even if he bows out soon, Sanders and his supporters appear to believe more strongly than ever that the system is rigged against him and that Clinton is a captive of the banks -- and that Democratic voters have been rising up in support of his “political revolution, ” regardless of the actual vote count.

What happened? The Sanders campaign has become a classic example of the phenomenon of “group polarization,” arguably more so than any campaign in recent memory -- even Donald Trump's, which has greatly benefited from the same phenomenon.

Research on group polarization finds that when like-minded people get together, they will tend to go to extremes. If group members favor Britain leaving the European Union, or an increase in the minimum wage, or stricter sentences for drug offenses, their conversations with one another will lead them to greater extremism. Echo chambers are a breeding ground for polarization -- and political campaigns often end up as echo chambers, especially in their late stages.

Part of what drives group polarization is that people care about their reputations: If people in your group think that climate change isn’t occurring, or that Clinton is a captive of the banks, you risk their good will if you disagree. And if people hide their private misgivings, and don’t tell others what they think, the group as a whole is likely to end up in a more extreme position.

That promotes another dynamic behind group polarization: lopsided information. If most people in your group think that the minimum wage should be increased, you’ll hear a lot of arguments in favor of increasing it, and you won’t hear many arguments the other way. And if people are listening to one another, they are likely to be moved in the direction of increasing the minimum wage, simply because those are the dominant arguments within the group.

Which brings us to Sanders. Many of his supporters are intensely committed to him, and they listen mostly to one another. At this point in time, it’s not exactly comfortable for them to say, to one another or to the candidate, that Clinton could be a fine president, even a great one, or that she is animated by many of the same values as Sanders. From his closest friends and advisers, Sanders is probably hearing a lot less of that than he should.

Even more important, the pressures of group polarization suggest that within the Sanders campaign, people have been spreading information that puts Clinton in the least favorable light, one that most sharpens the contrast with Sanders. Instead of seeing the two as representing different strands of the party, Sanders supporters have increasingly argued that their own candidate is on the side of the American people while Clinton isn’t. In those circumstances, is it any wonder that Sanders has been reluctant to terminate his campaign?

It’s true, of course, that after investing heart and soul, many presidential candidates are reluctant to bring things to a halt. It’s also true that Sanders is not exactly famous for his willingness to yield or to take a step back. But his improbably successful campaign has been spurred and energized by group polarization -- and you can’t explain his otherwise baffling persistence without reference to the potentially destructive effects of the political echo chamber.

This column does not necessarily reflect the opinion of the editorial board or Bloomberg LP and its owners.

To contact the author of this story:
Cass R Sunstein at csunstein1@bloomberg.net

To contact the editor responsible for this story:
Christopher Flavelle at cflavelle@bloomberg.net