A study of 126,000 rumours and false news stories spread on Twitter over a period of 11 years found that they travelled faster and reached more people than the truth.
The most common subject matter was false political news. Other popular topics included urban legends, business, terrorism, science, entertainment and natural disasters.
Twitter provided its data for the research. The firm told the BBC that it is already engaged with trying to devise a "health check" to measure its contribution to public conversation.
"False news is more novel, and people are more likely to share novel information," said Professor Sinan Aral, one of the study’s co-authors.
While the team did not conclude that novelty on its own caused the re-tweets, they said false news tended to be more surprising than real news, which may make it more likely to be shared.
Prof Aral, Soroush Vosoughi and associate professor Deb Roy began their research in the aftermath of the Boston marathon bombing in 2013.
"Twitter became our main source of news," said Dr Vosoughi. "I realized that … a good chunk of what I was reading on social media was rumours; it was false news."
The team used six independent fact-checking sources, including Snopes and Urbanlegend, to identify whether the stories in the study were genuine.
Their findings, published in the journal Science, included:
False news stories were 70% more likely to be re-tweeted than true stories. It took true stories around six times longer to reach 1,500 people. True stories were rarely shared beyond 1,000 people, but the most popular false news could reach up to 100,000.