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For starters, said Colleen Seifert, a professor of psychology at the University of Michigan, “People have a benevolent view of Facebook, for instance, as a curator, but in fact it does have a motive of its own. What it’s actually doing is keeping your eyes on the site. It’s curating news and information that will keep you watching.”
That kind of curating acts as a fertile host for falsehoods by simultaneously engaging two predigital social-science standbys: the urban myth as “meme,” or viral idea; and individual biases, the automatic, subconscious presumptions that color belief.
The first process is largely data-driven, experts said, and built into social media algorithms. The wide circulation of bizarre, easily debunked rumors — so-called Pizzagate, for example, the canard that Hillary Clinton was running a child sex ring from a Washington-area pizza parlor — is not entirely dependent on partisan fever (though that was its origin).
For one, the common wisdom that these rumors gain circulation because most people conduct their digital lives in echo chambers or “information cocoons” is exaggerated, Dr. Nyhan said.