The spread of misinformation by social bots

The massive spread of digital misinformation has been identified as a major global risk and has been alleged to influence elections and threaten democracies. Communication, cognitive, social, and computer scientists are engaged in efforts to study the complex causes for the viral diffusion of misinformation online and to develop solutions, while search and social media platforms are beginning to deploy countermeasures. However, to date, these efforts have been mainly informed by anecdotal evidence rather than systematic data. Here we analyze 14 million messages spreading 400 thousand claims on Twitter during and following the 2016 U.S. presidential campaign and election. We find evidence that social bots play a disproportionate role in spreading and repeating misinformation. Automated accounts are particularly active in amplifying misinformation in the very early spreading moments, before a claim goes viral. Bots target users with many followers through replies and mentions, and may disguise their geographic locations. Humans are vulnerable to this manipulation, retweeting bots who post misinformation. Successful sources of false and misleading claims are heavily supported by social bots. These results suggest that curbing social bots may be an effective strategy for mitigating the spread of online misinformation.