Facebook Emotional Contagion Experiment (2014)

The Facebook Emotional Contagion Experiment, where researchers at Cornell and Facebook manipulated the news feeds of 689,003 users without explicit consent to study emotional contagion, sparked outrage over research ethics in the digital age. The study found that reducing positive posts by 10% led to a measurable decrease in users' own positive posts, demonstrating the power of tech companies to run covert psychological experiments.