It’s a common experience. You log on to Facebook for your lunchtime fix of friends’ baby photos and links to fascinating online content from trusted sites like Slate, when you come across an intriguing headline such as “Stephen Hawking’s Blunder on Black Holes Shows Danger of Listening to Scientists, Says Bachmann” or “Sochi Hotel Guests Complain About Topless Portraits of Putin in Rooms”.

These stories aren’t real. They’re the work of the New Yorker’s not-particularly-funny online satirist Andy Borowitz, but many people, not just your gullible Facebook friends, invariably believe them. Sometimes the official state news agencies of global superpowers believe them.

Most of us—though unfortunately not all of us—are now aware that Onion articles aren’t real, but the proliferation of online parody and fake news has created an environment where many people are simply accepting fake news as fact. The bizarrely humorless Daily Currant and the often-pretty-funny military satire site Duffel Blog have been particularly adept at duping the news reading masses.

So why do people believe this crap? A recently published paper by physicist Delia Mocanu and four colleagues at Northeastern University’s Laboratory for the Modeling of Biological and Socio-Technical Systems looks at the phenomenon of “Collective Attention in the Age of (Mis)information,” concluding that Facebook users’ willingness to believe false information is rooted in mistrust of mainstream media sources.

The researchers examined Italian Facebook activity in the run-up to the election of 2013, looking at how users interacted with “troll” posts—those that present a “caricatural version of political activism and alternative news stories, with the peculiarity to include always false information.”

One example was a story reporting that the “Italian Senate voted and accepted (257 in favor and 165 abstentions) a law proposed by Senator Cirenga aimed at funding with 134 billion Euros the policy-makers to find a job in case of defeat in the political competition.”

There are a number of obvious red flags in this story. There is no Sen. Cirenga, Italy doesn’t have that many senators, and that amount of money would be 10 percent of the country’s GDP. Nonetheless, it went viral during the election, was reposted credulously by several mainstream political organizations, and according to the authors, was “among the arguments used by protesters manifesting in several Italian cities” during the election.

The authors also divided users into groups who get their news primarily from from political organizing sites, those who mainly share content mainstream news outlets, and those who prefer “alternative” news sources: “pages which disseminate controversial information, most often lacking supporting evidence and sometimes contradictory of the official news.”

They found that regular consumers of “alternative” news are far more likely to share false content. “We find that, out of the 1279 labeled users interacting with the troll memes, a dominant percentage (56% , as opposed to 26% and 18% for other groups) is constituted of users preeminently interacting with alternative information sources and thus more exposed to unsubstantiated claims.”

I quibble a bit with the authors’ use of the term “troll,” which implies malicious intent on the part of the creator. The “Senator Cirenga” item included in the paper seems more like an Onion-style attempt at mocking the self-interest of politicians than a deliberate effort to misinform the public.

Clearly, people took this particularly story a bit too far, but this type of misunderstanding is less dangerous than the type of content spread by sites like superviral sites Natural News, which as Brian Palmer recently explained, “has an uncanny ability to move unsophisticated readers from harmless dietary balderdash to medical quackery to anti-government zealotry.”

Also, Italy—a country where the former prime minister owned three of the country’s most popular TV networks and a major new political party is led by a Colbert-style comedian—might not be the most typical environment in which to study this phenomenon. The line between news, entertainment, and propaganda in Italian politics is a bit blurrier than in other countries.

And none of this is to imply that information in even the most established news sources should be trusted uncritically, but there is something to the idea that those most inclined to be critical of the mainstream media are often the least critical consumers of information from alternative sources.

Andy Borowitz isn’t really helping either.