A single Facebook message on Election Day 2010 brought about one third of a million more people to the ballot box in the United States, a study estimates. Researchers at the University of California, San Diego, said their study shows peer pressure can help get out the vote, and online social networks can affect important real-world behavior. In the massive-scale study experiment, more than 60 million people on Facebook saw a social, non-partisan \"get out the vote\" social message at the top of their news feeds on Nov. 2, 2010. The message included a reminder that \"Today is Election Day;\" a clickable \"I Voted\" button; a link to local polling places; a counter displaying how many Facebook users had already reported voting; and up to six profile pictures of users\' own Facebook friends who had reported voting. About 600,000 people, or 1 percent, were randomly chosen to see a modified \"informational message,\" identical in all respects to the social message except for pictures of friends. An additional 600,000 served as the control group and received no Election Day message from Facebook at all. An analysis of publicly available voting records showed rates of actual voting were highest for the group that got the social message, the researchers said. Users who got the informational message, without photos of friends, voted at the same rates as those who saw no message at all while those who saw photos of friends were indeed more likely to vote, they said. \"Social influence made all the difference in political mobilization,\" UC San Diego political science Professor James Fowler said. \"It\'s not the \'I Voted\' button, or the lapel sticker we\'ve all seen, that gets out the vote. It\'s the person attached to it.\" \"Behaviors changed not only because people were directly affected, but also because their friends (and friends of friends) were affected.\"