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Social media platforms like Facebook and Twitter permit experiments to be performed at minimal cost on populations of a size that scientists might previously have dreamed about. For instance, one experiment on Facebook involved more than 60 million subjects. Such large-scale experiments introduce new challenges as even small effects when multiplied by a large population can have a significant impact. Recent revelations about the use of social media to manipulate voting behavior compound such concerns. It is believed that the psychometric data used by Cambridge Analytica to target US voters was collected by Dr Aleksandr Kogan from Cambridge University using a personality quiz on Facebook. There is a real risk that researchers wanting to collect data and run experiments on social media platforms in the future will face a public backlash that hinders such studies from being conducted. We suggest that stronger safeguards are put in place to help prevent this, and ensure the public retain confidence in scientists using social media for behavioral and other studies.
A Case Study in Voter Participation
We know in detail about one very large experiment using social media as it has been written up in the scientific literature (Bond et al. 2012). The experiment was designed to improve voter participation. It involved all people aged 18 and over in the USA who used Facebook on November 2, 2010, the day of the midterm elections. The 61 million such users of Facebook that day were divided into three randomly chosen groups: one shown a message that "Today is Election Day," others the same message and some thumbnails of their friends who had voted saying "I voted," and the third group not shown anything.
Analysis of this experiment suggests that these interventions increased turnout by approximately 340,000 additional votes. This is approximately 0.5 percent of the total number of votes cast. The Facebook experiment wasn't designed to change the outcome. It was simply designed to increase voter participation. In particular, there was no bias in the way users were encouraged to vote. Users for the three difference groups were chosen uniformly at random. However, it is very possible that the experiment changed the outcome of some of the elections held that day. We cannot know for sure, as we...