People are as likely to spend as much time online discussing bogus rumours and conspiracy theories as genuine news, as social media is awash with misinformation, scientists claim.
A team of computational social scientists from Northeastern University in Boston launched the study to establish how conspiracy theories and rumours spread online, and which people are most likely to believe them.
The study follows comments last year by the World Economic Forum that "massive digital misinformation" constituted one of the biggest global threats to security.
The team identified three main sources of information online: mainstream news media, partisan political commentary sites and alternative information sites, including spoof news sites that spread fake stories.
They focused on data from 2.3 million internet users during the Italian election last year, when a fake story alleging that Italian senators had allocated themselves millions to find jobs in case they were voted from office went viral, and was shared more than 35,000 times on Facebook.
It is believed that the rumour fuelled protests in a number of Italian cities.
After counting the number and time of responses to stories on Facebook sites, the researchers found that there was the same level of engagement with information from partisan or fake news sites as from mainstream media sites, and that conspiracy theorists who rejected information from mainstream media were more likely to believe false information.
The desire to avoid "manipulation by mainstream media" makes people "more susceptible to false information", said lead researcher Walter Quattrociocchi.
They also find that those who regulalrly entered into discussions on partisan sites were more likely to believe rumours and false theories.
"We find that the most susceptible users to interact with false information are those that are mostly exposed and interacting with unsubstantiated claims," the authors say.
The researchers say they now want to expand the study to assess how rumours, such as those surrounding missing Malaysian flight MH370 spread globally, influencing public opinion, and how groups filter information to conform to a religious or ideological agenda.
"I'm not saying that all of the rumours are false, but the problem is how people select content in order to form their own belief," Quatrociocchi said. "We want to understand how they interact with individuals affiliated with the opposite faction."