Over 600,000 Facebook users have taken part in a psychological experiment organized by the social media company, without their knowledge.
Facebook altered the tone of the users' news feed to highlight either positive or negative posts from their friends, which were seen on their news feed. Facebook then monitored the users' responses, to see whether their friends' attitude had an impact on their own. The results indicated that emotions expressed by others on Facebook influenced users' emotions, constituting experimental evidence for mass-scale contagion via social networks.
Facebook was able to carry out the experiment because all users must check a box agreeing to their terms and conditions in order to use Facebook. The mandatory terms allow Facebook to conduct "internal operations, including troubleshooting, data analysis, testing, research and service improvement."
The lead scientist on the project, Adam Kramer, admitted in an interview when he joined Facebook that he took the job because "Facebook . . . constitutes the largest field study in the history of the world."