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.
Researchers from the Massachusetts Institute of Technology also found that fake news was more commonly re-tweeted by humans than bots.
They said it could be because fake news tends to be "more novel".
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
Psychology Prof Geoffrey Beattie from Edge Hill University in Lancashire, told the BBC there is a position of power associated with being someone who shares information that others have not heard before - regardless of whether or not it is true.
"People want to share information that is newsworthy - in some sense the truth value is less of a concern," he said.
He compared the spread of fake news with the sharing of gossip.
"The point about gossip is, the best gossip is juicy gossip - the last thing people are worried about is whether it is true or not," he said.
"It's whether it is plausible or not.
"We are saturated with news, so things have to be more and more surprising, or disgusting, to get attention."