Social media users are fuming following the release of a study which detailed how Facebook conducted a secret psychology experiment on thousands of its users.
For one week in 2012, researchers affiliated with Facebook, Cornell University, and the University of California at San Francisco, tampered with the algorithm used to place posts into the news feeds of nearly 700,000 users to test whether exposure to emotions led people to change their own posting behaviours.
The researchers found that "emotional states can be transferred to others via emotional contagion, leading people to experience the same emotions without their awareness".
"For people 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. When negativity was reduced, the opposite pattern occurred," the authors of the study wrote.
The study was legal according to Facebook's rules, but questions have been raised about whether it was ethical.
Social media users have labelled it "creepy" and said they felt like they were being treated like "lab rats".
"#Facebook manipulated user feeds for massive psych experiment... Yeah, time to close FB acct!" read one Twitter posting.
Another user posted: "Wow, talk about a privacy violation."
A professor of psychology at Princeton University, Susan Fiske, who edited the study for Proceedings of the National Academy of Sciences of America, told The Atlantic that she was "concerned" when the research first crossed her desk.
"Until I queried the authors and they said their local institutional review board had approved it-and apparently on the grounds that Facebook apparently manipulates people's News Feeds all the time," she said.
"I understand why people have concerns. I think their beef is with Facebook, really, not the research."