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.