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Why Fake News Spreads: A Neurological Explanation

Tatiana Shepeleva/

If efforts by foreign powers to influence American society via disinformation — like the “fake news” that spread during last year’s presidential election — are rising as a national-security concern, then we need to know why such antics work. How does an adversarial government go about persuading an entire population that something is true, or that one truth is more important or relevant than another?  

Recent research into the roots of persuasion in the brain yields some important clues about how people  are convinced to propagate news that is not true or poorly sourced. Bottom line: fake news appeals directly to the portions of the brain associated with social acceptance.  Activity from those regions has a bigger effect on decision-making than logical argument — like some snobby East Coast news outlet trying to tell you “true” things.

If you haven’t heard of the social brain or the role that it may play in deciding what to news to believe, you’re not alone. We associate most high-level decision making with the very front of the brain, the prefrontal cortex. You could be forgiven for thinking that prefrontal cortex would be the part of the brain we would use to evaluate the authenticity or accuracy of a big national news story.

But UCLA neuroscientist Matthew D. Lieberman has discovered a new neural network for social thinking that has an on-and-off relationship with the prefrontal cortex in decision-making.

As Lieberman explained in a 2013 TED talk, “Social thinking is so important that evolution gave us a separate brain system just for this type of thinking.” It runs along the side of the brain and is distinct from the prefrontal cortex. In fact, they seem to activate in a way that takes turns influencing one another.

“It’s as if these two networks are on two sides of a seesaw. When one goes up the other goes down,” he said. “This network also comes on when we’re taking in new information.”

[Skip to around minute 10.]

Lieberman’s lab asked test subjects to watch movie trailers while their brains were monitored via functional magnetic resonance imaging. He found that when the subjects experienced high activation in the social portion of the brain, they were much more likely to spread or share the trailer.

“This network switches us from being information consumers to information DJs,” he says.  

Here’s why this is big news for fake news. It relates directly to persuasion, getting a person to accept information you are giving them and then act on that information. Lieberman’s discovery is an effective hack for persuasion.

You use your social brain to make decisions about how to classify incoming information on the basis of your social network, who you follow online, what other news sites you read — what technologist Eli Pariser sometimes calls your filter bubble.  This analysis is accepted as important by the  prefrontal cortex, the so-called logical and analytical portion of your brain. If you’ve just read a news story, your social brain is shaping your decision to spread it as real or to denounce it as fake.

Lieberman’s work has been validated by Ian McCulloh, an Army veteran and neuroscientist at the Johns Hopkins School Applied Physics Lab. At a recent Global SOF Foundation event in Tampa, Florida, McCulloh discussed his own work with special operations forces personnel.

McCulloh described a recent test he and some colleagues performed in Amman, Jordan. He showed subjects anti-smoking ads that were targeted toward very particular groups (young men and older men with families). Using a much more portable brain measurement kit — one that measures electricity rather than hemoglobin — they found that ads targeted specifically to the subjects’ social group caused more of the prefrontal cortex to light up. The social signal was shaping reactions by the brain’s logic and decision portion. Put into behavioral terms, people are more likely to do something, believe something, or act on something if they are convinced that other people like them are engaging in that behavior.

That’s hardly surprising. But there’s a counter-implication as well: the same brain regions that boost socially accepted messages are also more resistant to information or news reports whose acceptance that might isolate that individual from their social group.

For the military, and Special Operations Forces in particular, that simple fact has direct relevance to the difficult work of persuading a local population not to embrace extremism, or believe bad stories about what the U.S. troops are doing.

“If you’re trying to use logical arguments to convince an ISIS supporter that ISIS is wrong, you’re polarizing them and make them more isolated. I mean, that’s, you know that’s sofa psychology,” McCulloh explained.

Beyond war, the lesson has relevance for how everyone accepts and then spreads ideas.

“If you’re really polarized on a particular issue — you’re on, let’s say, platform A, and I start telling you all the reasons why platform B is really a good, factual, better system, your brain does not systematically evaluate that information,” he said “Instead, what it does is it come up with all of the reasons and rationale as to why you should not believe that factual information, why you should distrust it. The result is that you become polarized in the opposite direction of whatever you want.”  

Back to Lieberman’s lecture. There’s an entire neural region that exists to keep people from accepting ideas or being persuaded by information that might isolate that individual from their social network.

The result: not only is the social brain region more susceptible to fake news that has high social value, it defends itself by shouting “fake news!” at information that runs contrary to already accepted information. Trolls, bots, and less-than-reputable news sites take that individual reaction and spread it across an entire self-selected user group at lightning speed.

This, in part, is why a report suggesting that the CIA hacked the DNC to frame Russia can gain traction both on Russian propaganda sites such as RT and alternative-right news sites like Breitbart. It’s also one reason why people who follow news sites on the basis of whether they are liberal or conservative are more likely to accept and act on bad information.

The FBI is reportedly exploring the role of RT and  Breitbart and similar sites in the spread of disinformation masquerading as news coverage during the 2016 election.  The news comes as a gathering chorus of policy-makers and even members of the intelligence community fret over the effects of fake news on public life.

But actually stopping fake news will likely be more difficult than spotting it.

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