This time the experimenters “manipulated the extent to which people (N = 689,003) were exposed to emotional expressions in their News Feed.” The experiment was structured like one of those allegedly benign A/B tests. In this case one group was exposed to mostly positive messages in their news feed and the other to predominantly negative messages. The idea was to test whether even subliminal exposure to specific emotional content would cause people to change their own posting behavior to reflect that content. It did. Whether or not users felt happier or sadder, the tone of their expression changed to reflect their news feed.

Shoshana Zuboff, The Age of Surveillance Cap…, loc. 943