Emotional Contagion is the idea that emotions spread throughout networks. If you are around happy people, you are more likely to be happy. If you are around gloomy people, you are likely to be glum.
The data scientists at Facebook set out to learn if text-based, nonverbal/non-face-to-face interactions had similar effects. They asked: Do emotions remain contagious within digitally mediated settings? They worked to answer this question experimentally by manipulating the emotional tenor of users’ News Feeds, and recording the results.
Public reaction was such that many expressed dismay that Facebook would 1) collect their data without asking and 2) manipulate their emotions.