The study conducted on the social media outlet focused on the effects of friends on political mobilization. In the experiment, over 60 million people were shown a non-partisan, “Get Out And Vote” banner on Election Day that included a clickable “I Voted” button, links to polling places and a counter. Approximately 600,000 Facebook users were shown an identical message, but with the addition of pictures of friends who had already voted. A separate control group wasn’t given a message.

According to the study, Facebook users who saw the message with their friends’ pictures were far more likely to both search for a polling place and to click the “I Voted” button. The experiment was careful to cross-reference voting records to eliminate the number of people who clicked the button without actually voting.

For researchers, the results suggested that peer pressure is an effective way to bring voters to the polls, and that social media is valuable in influencing real-world behavior. Researchers also determined that the strength of the message’s impact relied significantly on close relationships.

Subjects were far more likely to vote if they saw pictures of friends whom they later described to researchers as “close friends in real life.” The study emphasized that even though the effect per single message was small, the real political tool lies in the reach that Facebook provides.

In a statement on the UCSD News Center website, James Fowler, the UCSD professor of political science who led the study, said, “The main driver of behavior change is not the message — it’s the vast social network. Whether we want to get out the vote or improve public health, we should not only focus on the direct effect of an intervention, but also on the indirect effect as it spreads from person to person to person.”

Further research will try to determine which people are most effective in the mobilization process, and what kind of messages best increase voter participation.