When Facebook Experimented on Your Emotions: The Secret Study That Manipulated 689,000 Users

In January 2012, Facebook conducted one of the most controversial experiments in the history of technology companies. Without informed consent, the company manipulated the News Feeds of approximately 689,003 users over one week, systematically altering the emotional content they saw to test whether emotional states could be transferred through social media. The study, published in the Proceedings of the National Academy of Sciences in 2014, found that they could — and ignited a firestorm over corporate experimentation on unsuspecting users.

The experiment, officially titled "Experimental Evidence of Massive-Scale Emotional Contagion Through Social Networks," divided users into two groups. One group had positive content reduced in their News Feed; the other had negative content reduced.