For the 48th World Communications Day, Pope Francis produced a remarkable (and mostly enthusiastic) message about the effects of social media. He contended that the Internet is “something truly good, a gift from God.”

At the same time, he warned that the “variety of opinions being aired can be seen as helpful, but it also enables people to barricade themselves behind sources of information which only confirm their own wishes and ideas, or political and economic interests.” For that reason, Pope Francis observed, the new world of communications “can help us either to expand our knowledge or to lose our bearings.”

In what sense can the variety of opinions make us “lose our bearings”? The pope was referring to the use of new technologies to create echo chambers, in which people take advantage of the countless options to confirm their pre-existing convictions. Thus he warned of a situation in which we become “closed in on ourselves.”

With respect to the harmful effects of barricades, the pope’s concern has strong empirical justifications. When people listen only to views that confirm their own ideas, they don’t merely maintain those ideas; they tend to get more extreme.

If, for example, people are opposed to same-sex relationships, or believe that affirmative action is a good idea, they become more confident, more unified and more extreme as a result of listening and talking to one another.

In recent years, there has been a lot of debate about whether self-segregation is occurring. Seth Flaxman and his coauthors at Microsoft Research recently offered the most comprehensive evidence to date, and they demonstrate that Pope Francis’ warning is warranted. They find that many people who read partisan articles regularly “are almost exclusively exposed to only one side of the political spectrum,” and to that extent tend to exist in something very much like an echo chamber.

The study involved the Web-browsing histories of 1.2 million U.S.-located users over three months in 2013, with a total of 2.3 billion page views. One finding is that there is a high degree of ideological segregation when users share opinion pieces on social media (perhaps because of ideological similarity among people’s social contacts). When such sharing occurs, people show a tendency to restrict themselves to points of view that fit with their existing beliefs.

Flaxman and his co-authors also found that when people come across opinion pieces through Web searches, the level of segregation is pronounced; they tend to read pieces with which they already agree. One reason may be that people click on the news sources they trust.

Another may be that Web algorithms are personalizing what they show (and thus creating “filter bubbles”). In either case, the result supports Pope Francis’ concern: For opinion stories, increased choice amplifies ideological segregation.

Flaxman and his co-authors also found that most people who visit left-leaning news outlets rarely read substantive articles from the conservative side, and right-leaning readers show the same insulation, at least for opinion articles. The disturbing result is that many people end up “unaware of the other side of the political debate.”

But there are major qualifications to this basic story. Most Americans have centrist rather than extreme preferences, and our centrism is reflected in our browsing habits. Moreover, most of us don’t get our information from either opinion pieces or highly polarized sources. Even if we exclude apolitical categories (such as entertainment and sports), a mere 6 percent of news consumption comes from opinion.

In addition, social media and Web searches are hardly the source of most information we find on the Internet. Within the categories of both opinion and purely descriptive news, direct browsing, in which people go straight to their preferred websites, remains by far the dominant channel of consumption.

When people encounter opinion pieces on the home pages of their preferred news outlets, they are less likely to restrict their reading along ideological lines. It follows that while a lot of ideological self-segregation can be found if we focus only on social media and Web searches, the total amount is much smaller.

Notwithstanding these qualifications, there is no question that for many users, social media are increasing the creation of echo chambers.

As the importance of those media grows over time, the risk of ideological barricades is likely to grow as well. Drawing attention to that risk, Pope Francis emphasized the importance of “the ability to be silent and to listen,” which can help us “learn to look at the world with different eyes and come to appreciate the richness of human experience as manifested in different cultures and traditions.”

Social media offer an unprecedented opportunity to appreciate that richness — or instead to run away from it.

Cass R. Sunstein, the Robert Walmsley University professor at Harvard Law School, is a Bloomberg View columnist. He is a former administrator of the White House Office of Information and Regulatory Affairs, the co-author of “Nudge” and author of “Conspiracy Theories and Other Dangerous Ideas,” forthcoming in March. Email: csunstei@law.harvard.edu.

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