WASHINGTON -- Facebook had deliberately manipulated its users' emotions by rolling out either positive or negative news feeds to them, says a new study unveiled Saturday. 

The study, titled "Experimental Evidence Of Massive-Scale Emotional contagion Through Social Networks," explained how the social media giant tampered with its algorithm to manipulate the news feeds of its 689,003 users.

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Called "emotional contagion," Facebook used an automated system that lessened emotional reactions. The study employed the same procedures and manipulated user timelines to lessen users' positive reactions. Results showed that people using Facebook at the time posted more negative responses. The reverse results take place when the opposite patterns were used resulted in less negative reactions.

In 2012, a similar incident occurred when Facebook manipulated news feeds for a week and placed well-crafted posts. Reseachers from Cornell University and the University of California at San Francisco showed that the overall mood of Facebook users was affected. In its defense, Facebook argued that the 2012 incident was within legal bounds and cited the company's Data Use Policy that allowed it to experiment on users's emotions.

In the present study, it highlighted that emotional states transferred through emotional contagion can lead to people feeling the same thing without being aware of it.

"The emotions expressed by friends, via online social networks, influence our own moods," the study stated. "[This first experiment] is evidence for massive-scale emotional contagion and supports claims that emotions can spread through a network."

The findings of the study was published on June 17 and appeared in the Proceedings of the National Academy of Sciences.

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