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In this task, you are given a text of many news articles seperated by special token "|||||". Your task is to summarize them.

According to a new paper in the Proceedings of the National Academy of Science, Facebook altered the News Feeds for hundreds of thousands of users as part of a psychology experiment devised by the company's on-staff data scientist. By scientifically altering News Feeds, the experiment sought to learn about the way positive and negative effect travels through social networks, ultimately concluding that "in-person interaction and nonverbal cues are not strictly necessary for emotional contagion." 
  
 "Each emotional post had between a 10 percent and 90 percent chance...of being omitted." 
  
 To test the hypothesis, the researchers identified 689,003 different English-language Facebook users, and began removing emotionally negative posts for one group and positive posts for another. According to the paper, "when a person loaded their News Feed, posts that contained emotional content of the relevant emotional valence, each emotional post had between a 10 percent and 90 percent chance (based on their User ID) of being omitted from their News Feed for that specific viewing." The posts were still available by visiting a friend's timeline directly or reloading the News Feed. The researchers also state that they did not alter any direct messages sent between users. 
  
 As the researchers point out, this kind of data manipulation is written into Facebook's Terms of Use. When users sign up for Facebook, they agree that their information may be used "for internal operations, including troubleshooting, data analysis, testing, research and service improvement." While there's nothing in the policy about altering products like the News Feed, it's unlikely Facebook stepped outside the bounds of the Terms of Use in conducting the experiment. Still, for users confused by the whims of the News Feed, the experiment stands as a reminder: there may be more than just metrics determining which posts make it onto your feed. ||||| One of the authors of a controversial Facebook study into emotional states published this month has apologized for anxiety caused. 
  
 Facebook tweaked the News Feeds of nearly 700,000 users by displaying disproportionately positive or negative statuses for one week in January 2012, to help its researchers understand how emotional states are transmitted on social media. More than 3 million posts were analyzed in the experiment. 
  
 “My co-authors and I are very sorry for the way the paper described the research and any anxiety it caused. In hindsight, the research benefits of the paper may not have justified all of this anxiety,” wrote Adam Kramer, one of the three authors, in a Facebook post. 
  
 But Kramer also defended the social network’s study. “We felt that it was important to investigate the common worry that seeing friends post positive content leads to people feeling negative or left out,” he wrote. 
  
 Controversy swirled around the social media giant’s ethics because users were not explicitly asked or notified that they were part of the experiment. Instead, Facebook relied on its terms of service that all users agree to when signing up and allows them to conduct studies like this. 
  
 You can read the full post by Kramer here: ||||| It already knows whether you are single or dating, the first school you went to and whether you like or loathe Justin Bieber. But now Facebook, the world's biggest social networking site, is facing a storm of protest after it revealed it had discovered how to make users feel happier or sadder with a few computer key strokes. 
  
 It has published details of a vast experiment in which it manipulated information posted on 689,000 users' home pages and found it could make people feel more positive or negative through a process of "emotional contagion". 
  
 In a study with academics from Cornell and the University of California, Facebook filtered users' news feeds – the flow of comments, videos, pictures and web links posted by other people in their social network. One test reduced users' exposure to their friends' "positive emotional content", resulting in fewer positive posts of their own. Another test reduced exposure to "negative emotional content" and the opposite happened. 
  
 The study concluded: "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." 
  
 Lawyers, internet activists and politicians said this weekend that the mass experiment in emotional manipulation was "scandalous", "spooky" and "disturbing". 
  
 On Sunday evening, a senior British MP called for a parliamentary investigation into how Facebook and other social networks manipulated emotional and psychological responses of users by editing information supplied to them. 
  
 Jim Sheridan, a member of the Commons media select committee, said the experiment was intrusive. "This is extraordinarily powerful stuff and if there is not already legislation on this, then there should be to protect people," he said. "They are manipulating material from people's personal lives and I am worried about the ability of Facebook and others to manipulate people's thoughts in politics or other areas. If people are being thought-controlled in this kind of way there needs to be protection and they at least need to know about it." 
  
 A Facebook spokeswoman said the research, published this month in the journal of the Proceedings of the National Academy of Sciences in the US, was carried out "to improve our services and to make the content people see on Facebook as relevant and engaging as possible". 
  
 She said: "A big part of this is understanding how people respond to different types of content, whether it's positive or negative in tone, news from friends, or information from pages they follow." 
  
 But other commentators voiced fears that the process could be used for political purposes in the runup to elections or to encourage people to stay on the site by feeding them happy thoughts and so boosting advertising revenues. 
  
 In a series of Twitter posts, Clay Johnson, the co-founder of Blue State Digital, the firm that built and managed Barack Obama's online campaign for the presidency in 2008, said: "The Facebook 'transmission of anger' experiment is terrifying." 
  
 He asked: "Could the CIA incite revolution in Sudan by pressuring Facebook to promote discontent? Should that be legal? Could Mark Zuckerberg swing an election by promoting Upworthy [a website aggregating viral content] posts two weeks beforehand? Should that be legal?" 
  
 It was claimed that Facebook may have breached ethical and legal guidelines by not informing its users they were being manipulated in the experiment, which was carried out in 2012. 
  
 The study said altering the news feeds 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". 
  
 But Susan Fiske, the Princeton academic who edited the study, said she was concerned. "People are supposed to be told they are going to be participants in research and then agree to it and have the option not to agree to it without penalty." 
  
 James Grimmelmann, professor of law at Maryland University, said Facebook had failed to gain "informed consent" as defined by the US federal policy for the protection of human subjects, which demands explanation of the purposes of the research and the expected duration of the subject's participation, a description of any reasonably foreseeable risks and a statement that participation is voluntary. "This study is a scandal because it brought Facebook's troubling practices into a realm – academia – where we still have standards of treating people with dignity and serving the common good," he said on his blog. 
  
 It is not new for internet firms to use algorithms to select content to show to users and Jacob Silverman, author of Terms of Service: Social Media, Surveillance, and the Price of Constant Connection, told Wire magazine on Sunday the internet was already "a vast collection of market research studies; we're the subjects". 
  
 "What's disturbing about how Facebook went about this, though, is that they essentially manipulated the sentiments of hundreds of thousands of users without asking permission," he said. "Facebook cares most about two things: engagement and advertising. If Facebook, say, decides that filtering out negative posts helps keep people happy and clicking, there's little reason to think that they won't do just that. As long as the platform remains such an important gatekeeper – and their algorithms utterly opaque – we should be wary about the amount of power and trust we delegate to it." 
  
 Robert Blackie, director of digital at Ogilvy One marketing agency, said the way internet companies filtered information they showed users was fundamental to their business models, which made them reluctant to be open about it. 
  
 "To guarantee continued public acceptance they will have to discuss this more openly in the future," he said. "There will have to be either independent reviewers of what they do or government regulation. If they don't get the value exchange right then people will be reluctant to use their services, which is potentially a big business problem." |||||
Output:
A co-author of a controversial study that involved secretly altering the News Feeds of some Facebook users back in 2012 has apologized, on Facebook, naturally. "I can understand why some people have concerns about it, and my coauthors and I are very sorry for the way the paper described the research and any anxiety it caused," wrote Facebook data scientist Adam Kramer, per Time. "In hindsight, the research benefits of the paper may not have justified all of this anxiety." The study altered News Feeds so that some users saw more positive status updates while others saw more negative status updates. "We felt that it was important to investigate the common worry that seeing friends post positive content leads to people feeling negative or left out," Kramer explains. "At the same time, we were concerned that exposure to friends’ negativity might lead people to avoid visiting Facebook." They ended up finding the opposite—those who saw more positive updates were more likely to be positive in their own updates, and vice versa. Kramer goes on to explain that only about 0.04% of users saw their feeds impacted, that the experiment lasted only a week, and that no one had any posts actually "hidden." Still, as The Verge points out, 0.04% of Facebook users amounts to hundreds of thousands of people (689,003, specifically). Facebook provided its own statement to the Guardian, saying the study was meant to help Facebook understand "how people respond to different types of content" so that the social network can provide the most "relevant and engaging" content.