"Given the modest treatment, it is surprising that they found any effect at all," said Gerald Kane, an associate professor of information systems at Boston College, who was not involved with the study.
The scientists concluded that the informational message was ineffective. The social message, on the other hand, was powerful because it probably provided social pressure on the users to vote by showing them that friends had reported voting, Fowler said.
The scientists found that for every recipient persuaded by the message to vote, four close Facebook friends — relationships identified by a high number of Facebook interactions — ended up voting as a result.
"We don't know how this works; it could be that on Facebook, you see that a friend has voted or that he simply takes you with him to vote," Fowler said.
The scientists could not find a difference between Republicans or Democrats who were activated by the message. But Fowler said the methods for discriminating between the two groups were primitive in this study — it involved reading the political preference written by users on their profiles, and only 1 percent of the users provided one. But for future studies, the team is developing more intricate analyses, inferring political orientation from what comments users write and where they place their "likes".
Many social scientists are eager to use Facebook's data for their experiments. "This is the most exciting research of my lifetime," Fowler said.
"This kind of approach should revolutionize our understanding of human behavior," said David Lazer of Northeastern University, a social network expert who is not associated with the study but is pursuing similar work.
In a conference call with reporters, Facebook's Marlow said that he could not comment directly on whether Facebook is planning something similar for this year's election but added that Facebook is committed to supporting the democratic process.