The Ethics of Online Experimentation with Unsuspecting Users

In the summer of 2014, the journal Proceedings of the National Academy of Sciences (PNAS) published a study about emotional contagion conducted by a Facebook researcher in collaboration with two academics. 1 The premise of the study was that emotional states can spread through social networks. The data was gathered for one week in January 2012 from 689,003 randomly selected users who interact with Facebook‟s English version. 2 Two parallel experiments were conducted; one for positive and the other for negative emotional content. In both cases, user exposure to friends‟ emotional content displayed via the News Feed was reduced. Both experiments had their own control condition, in which a similar proportion of posts in the News Feed were omitted regardless of their emotional content. The results indicate that users in the reduced-positive condition had a larger percentage of negative words in their own status updates and a smaller percentage of positive words. The opposite pattern was observed in the reduced-negative condition. Although the effect size for the manipulations was very small, the findings provided statistically significant evidence of emotional contagion via social networks.