Facebook experimented on about 689,003 of its users without their knowledge, manipulating news feeds to see what the impact was on the human psyche.
Slate reported that Facebook wanted to see if reducing the number of positive message a person saw would make them less likely to post something positive. Ditto for negative posts. Facebook used a program to analyze whether a post contained positive or negative words.
A paper on the experiment was published in the Proceedings of the National Academy of Sciences: "The experiment manipulated the extent to which people were exposed to emotional expressions in their News Feed. This tested whether exposure to emotions led people to change their own posting behaviors, in particular whether exposure to emotional content led people to post content that was consistent with the exposure."
The experiments occurred during one week in January in 2012.
What did the experiment find?
"The results show emotional contagion," the paper states. "[P]eople who had positive content reduced in their News Feed, a larger percentage of words in people's status updates were negative and a smaller percentage were positive."
The Wall Street Journal reported that Facebook data scientist Adam Kramer expressed second thoughts about the conducting the study: "In hindsight, the research benefits of the paper may not have justified all of this anxiety." The Wall Street Journal reported that Kramer pointed out that Facebook's review process since 2012 has "come a long way since then."