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How Facebook spreads falsehoods

| Thursday, Jan. 14, 2016, 8:55 p.m.

Why does misinformation spread so quickly on social media? When the truth is so easy to find, why do people accept falsehoods?

A new study focusing on Facebook users provides strong evidence that the explanation is confirmation bias: people's tendency to seek out information that confirms their beliefs — and to ignore contrary information.

Confirmation bias turns out to play a pivotal role in the creation of online echo chambers. This finding bears on a wide range of issues, including the current presidential campaign, the acceptance of conspiracy theories and competing positions in international disputes.

The new study, led by Michela Del Vicario of Italy's Laboratory of Computational Social Science, explores the behavior of Facebook users from 2010 to 2014. One of the study's goals was to test a question that continues to be sharply disputed: When people are online, do they encounter opposing views, or do they create the virtual equivalent of gated communities?

Del Vicario and her co-authors explored how Facebook users spread conspiracy theories (using 32 public Web pages); science news (using 35 such pages); and “trolls,” which intentionally spread false information (using two Web pages).

In sum, the researchers find a lot of communities of like-minded people. Even if they are baseless, conspiracy theories spread rapidly within such communities.

More generally, Facebook users tended to choose and share stories containing messages they accept and to neglect those they reject.

As Del Vicario and her co-authors put it, “users mostly tend to select and share content according to a specific narrative and to ignore the rest.” On Facebook, the result is the formation of a lot of “homogeneous, polarized clusters.” Within those clusters, new information moves quickly among friends (often in just a few hours).

Once people discover that others agree with them, they become more confident — and then more extreme.

In that sense, confirmation bias is self-reinforcing, producing a vicious spiral.

Suppose, for example, that you think an increase in the minimum wage is a sensational idea, that the nuclear deal with Iran is a mistake, that ObamaCare is working well, that Donald Trump would be a fine president or that the problem of climate change is greatly overstated. Arriving at these judgments on your own, you might well hold them tentatively and with a fair degree of humility. But after you learn that a lot of people agree with you, you are likely to end up with much greater certainty — and perhaps real disdain for people who do not see things as you do.

The best solution is to promote a culture of humility and openness. Some people — and some communities — hold their own views tentatively; they are interested in refutation, not just confirmation.

Users of social media are certainly exercising their liberty. But there is a real risk that when they fall prey to confirmation bias, they end up compromising liberty's spirit — and are dead wrong to boot.

Cass R. Sunstein, a Bloomberg View columnist, is a Harvard University professor who was the administrator of the White House Officer of Information and Regulatory Affairs (2009-12).

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