For Cass Sunstein, a challenge that social media poses to democracy was clarified by a social-science experiment that he conducted in two different communities in Colorado: left-leaning Boulder and right-leaning Colorado Springs. Residents in each place were gathered into small groups to discuss their views on controversial topics, like climate change and same-sex marriage. Afterward, they were asked to report on the opinions of their groups as well as their own views on the subjects.

The results were the same in both communities.

The effect of gathering into groups composed of mostly like-minded people to discuss controversial subjects was to make participants more set and extreme in their views:

(1) Liberals, in Boulder, became distinctly more liberal on all three issues. Conservatives, in Colorado Springs, become distinctly more conservative on all three issues. The result of deliberation was to produce extremism -- even though deliberation consisted of a brief (15 minute) exchange of facts and opinions! (2) The division between liberals and conservatives became much more pronounced. Before deliberation, the median view, among Boulder groups, was not always so far apart from the median view among Colorado City groups. After deliberation, the division increased significantly. (3) Deliberation much decreased diversity among liberals; it also much decreased diversity among conservatives. After deliberation, members of nearly all groups showed, in their post-deliberation statements, far more uniformity than they did before deliberation.

Sunstein, a Harvard faculty member, and Reid Hastie, a professor at the University of Chicago, wrote about their findings in “Wiser: Getting Beyond Groupthink to Make Groups Smarter.” And Sunstein returned to them Monday in a talk on social media and democracy at the Aspen Ideas Festival, which is co-hosted by The Aspen Institute and The Atlantic, where he ran through some of the explanations for group polarization.