Facebook has admitted that it has manipulated the News Feeds of nearly 700,000 users as part of its research study on emotional states.

According to a report by Forbes, the data scientists of the social media giant manipulated the News Feeds of 689,003 users by removing either all of the positive posts or all of the negative posts, with the purpose of seeing how their moods are affected by such changes. It found out that emotions can be contagious, even without “direct interaction between people.”

The results of the study, which ran from January 11–18, 2012, was published in the PNAS, the official journal of the United States National Academy of Sciences (NAS).

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