Around 340,000 more Facebook users 'like' voting after friends' messages prompt them to hit the polls, according to a new mass study of online activity.

Facebook friends boost American voters (G)

Facebook messages from close friends influenced voting behaviour during the 2010 US elections, according to a mass online study of 61 million Facebook users.

The study, published in Nature, is the first to demonstrate that the online world can affect real-world behaviour on a large scale, say researchers, but it proves that only close 'real-life' friends have an influence.

The vast majority of users were shown a 'social' banner message on Facebook telling them which of their friends had voted and a counter of Facebook users who had clicked it. Around 1 per cent of the trial, or 600,000 people saw an 'informational' banner with which encouraged them to vote.

Researchers compared the groups' online behaviours with publicly available voting records.

The social message directly increased turnout by about 60,000 votes, but a further 280,000 people were indirectly nudged to the polls by seeing updates from their friends in their news feeds, researchers estimate.

"The online social network helps to quadruple the effect of the message," says James Fowler, political scientist at the University of California, who led the study in collaboration with Facebook's data-science team.

Online networks are powerful...but it is those real-world ties that we have always had that are making a difference. James Fowler, University of California

Nearly all the impact occurred between 'close friends' who were more likely to have a face-to-face relationship, and real-world ties are far more influential than more distant, online-only friend, researchers found.

"Online networks are powerful...but it is those real-world ties that we have always had that are making a difference," added Mr Fowler.

Facebook users have an average of about 150 friends, but they are likely to have close relationships with only 10. "The closest 10 friends on Facebook mattered; the other 140 didn't matter at all," says Fowler.

Nearly every American of voting age who logged into Facebook on Election Day 2010 was part of the experiment, even though they didn't know it.

Sociologists praised the study for tackling online behaviour on such a mass scale, but the researchers emphasised that more needs to be done to determine users' motivations more precisely.