If you are exposed to negative person, then that negativity might bleed over to infect you. If you are exposed to a positive person, then those positive emotions might put you in a more positive frame of mind as well. Since you likely have experienced that in real life, then you probably don't need research to back that up. Facebook's data scientists were out to prove if emotions expressed digitally would also be contagious.
If you signed up for Facebook, then you accepted Facebook's Data Use Policy even if you didn't bother to read it. Yet that policy allowed researchers to conduct a sketchy science experiment that manipulated the News Feed of 689,003 people and supposedly provided "evidence of massive-scale emotional contagion through social networks." The researchers said it was all perfectly legal because machines and not humans analyzed the posts. "As such, it was consistent with Facebook's Data Use Policy, to which all users agree prior to creating an account on Facebook, constituting informed consent for this research."
The experiments happened during one week in 2012, January 11--18, and "participants were randomly selected based on their User ID... In total, over 3 million posts were analyzed, containing over 122 million words, 4 million of which were positive (3.6%) and 1.8 million negative (1.6%). Emotional content was determined by LIWC software that defines negative emotion words like hurt, ugly and nasty and positive emotion words like love, nice and sweet.
Overall, the researchers found that people post more positive than negative posts, 22.4% negative to 46.8% positive. According to a report published at the Proceedings of the National Academy of Sciences (PNAS), the "results show emotion contagion."
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. These results suggest that the emotions expressed by friends, via online social networks, influence our own moods, constituting, to our knowledge, the first experimental evidence for massive-scale emotional contagion via social networks, and providing support for previously contested claims that emotions spread via contagion through a network.
This social network experiment toying with emotions might be considered messing with a person's mind. If such manipulation was taken to the next level, aka weaponized, might it be dubbed psychological warfare? Basically, if the data scientists' social media experiments seem invasive to you then stop using Facebook.
In another bit of Facebook news that happened over a year ago, but just became public knowledge, Facebook announced it has been fighting a bulk search warrant since last summer. Shortly after NSA's PRISM program was leaked, a New York district attorney decided he wanted a piece of that bulk surveillance action. He used "secret orders" to demand that Facebook "turn over nearly all data from the accounts of 381 people who use our service, including photos, private messages and other information. This unprecedented request is by far the largest we've ever received--by a magnitude of more than ten--and we have argued that it was unconstitutional from the start."
The people targeted, according to Facebook's appeal brief, included a cross-section of America "from high schoolers to grandparents, ... electricians, school teachers, and members of our armed services." 62 users were later charged in a disability fraud case, but a gag order prohibited Facebook from notifying 319 innocent users about the government scooping up their data too. Fast forward a year during which Facebook filed an appellate brief and the government finally unsealed the records. But the government didn't return or destroy the data for the 319 innocent users. Instead, as the EFF said, the "DA continues to hold a digital dossier of the lives of over 300 people never charged with a crime."
Facebook said it will continue the legal fight to retrieve that data.