Facebook has responded to criticism it has received for manipulating users’ moods for a psychological experiment by saying the research was undertaken to “improve our service and to make the content people see on Facebook as relevant and engaging as possible.”

The social network has been strongly denounced by users after it published a paper detailing how it was able to affect individuals’ moods by altering the amount of positive or negative content that appeared in their News Feed.

Lawyers and technology experts have also expressed worries that the same methods could be used to manipulate populations for political gain while academics have criticized Facebook failing to acquire the “informed consent” necessary for subjects of human experiments.

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In a statement given to The Independent, a spokesperson for the social network said: “This research was conducted for a single week in 2012 and none of the data used was associated with a specific person’s Facebook account. We carefully consider what research we do and have a strong internal review process. There is no unnecessary collection of people’s data in connection with these research initiatives and all data is stored securely.”

Shape Created with Sketch. Facebook privacy settings you should know about Show all 6 left Created with Sketch. right Created with Sketch. Shape Created with Sketch. Facebook privacy settings you should know about 1/6 Change who sees your posts. Anything you post on Facebook - from a status update to a photo - can be given its own privacy setting. 'Public' means that the information can be found via Google, or you can create custom groups of friends (http://ind.pn/1bVJJ2H) to share info with. Remember: whatever setting you last choose will become default until you change it again. 2/6 Check what your friends are sharing about you. Sometimes it's not you, but your friends that give information away. Follow this link to see the information that your friends might be sharing with third party apps - http://ind.pn/1bVVar6. Click the 'edit' option to the right of 'Apps other use' and un-tick every category of info you don't want to share. There's also an option above labelled 'Apps you use' that lets you select which apps can use your Facebook data elsewhere on the web. Don't trust them? Click the little cross on the right. 3/6 Hide old posts. If you're keen to make your Facebook past more private, limiting who can see your old posts should be your first step. Follow this link - http://ind.pn/1bVK7hv - and click 'Limit The Audience for Old Posts on Your Timeline'. You can make all of these old photos and stats updates vieweable to the public, friends only, or just yourself. From this page you can also change who can send you messages and friend requests. 4/6 Create friend lists. Since September 2011 Facebook has let you create different 'lists' of friends in order to let you separate what your close buddies and your work colleagues see. Facebook can give you a head start by suggesting lists based on who you went to school with and where people live - and you can even choose to browse a News Feed populated only by a certain list. Follow the link below for a full guide: http://ind.pn/1bVPu0d 5/6 Limit adverts. Pages you like will sometimes be used by Facebook to endorse a product to your friends. If you don't wnat these to show up head to this page - http://ind.pn/1j6Mc2b - select "Pair my social actions with adverts for no one" and click Save Changes. 6/6 Check your profile. If you're still worried about which of your photos or posts are visible to people you can check what the public (or any specific individual) sees when they click on your profile. View your profile by clicking on your namem then click the cog in the bottom right hand corner of your cover photo, then select 'View as...' 1/6 Change who sees your posts. Anything you post on Facebook - from a status update to a photo - can be given its own privacy setting. 'Public' means that the information can be found via Google, or you can create custom groups of friends (http://ind.pn/1bVJJ2H) to share info with. Remember: whatever setting you last choose will become default until you change it again. 2/6 Check what your friends are sharing about you. Sometimes it's not you, but your friends that give information away. Follow this link to see the information that your friends might be sharing with third party apps - http://ind.pn/1bVVar6. Click the 'edit' option to the right of 'Apps other use' and un-tick every category of info you don't want to share. There's also an option above labelled 'Apps you use' that lets you select which apps can use your Facebook data elsewhere on the web. Don't trust them? Click the little cross on the right. 3/6 Hide old posts. If you're keen to make your Facebook past more private, limiting who can see your old posts should be your first step. Follow this link - http://ind.pn/1bVK7hv - and click 'Limit The Audience for Old Posts on Your Timeline'. You can make all of these old photos and stats updates vieweable to the public, friends only, or just yourself. From this page you can also change who can send you messages and friend requests. 4/6 Create friend lists. Since September 2011 Facebook has let you create different 'lists' of friends in order to let you separate what your close buddies and your work colleagues see. Facebook can give you a head start by suggesting lists based on who you went to school with and where people live - and you can even choose to browse a News Feed populated only by a certain list. Follow the link below for a full guide: http://ind.pn/1bVPu0d 5/6 Limit adverts. Pages you like will sometimes be used by Facebook to endorse a product to your friends. If you don't wnat these to show up head to this page - http://ind.pn/1j6Mc2b - select "Pair my social actions with adverts for no one" and click Save Changes. 6/6 Check your profile. If you're still worried about which of your photos or posts are visible to people you can check what the public (or any specific individual) sees when they click on your profile. View your profile by clicking on your namem then click the cog in the bottom right hand corner of your cover photo, then select 'View as...'

Writing in a blog post on the site, one of the study’s co-authors Adam Kramer said: “Having written and designed this experiment myself, I can tell you that our goal was never to upset anyone. I can understand why some people have concerns about it, and my co-authors and I are very sorry for the way the paper described the research and any anxiety it caused.”

Some 689,000 users were drafted into the experiment which manipulated a "small percentage" of content. The study concluded that: "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."

On Sunday evening Jim Sheridan MP, a member of the Commons media select committee, described the experiment as ‘thought-control’ and called for an investigation into emotional manipulation by social networks.

“This is extraordinarily powerful stuff and if there is not already legislation on this, then there should be to protect people," Sheridan was reported as saying by The Guardian. “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.”

Clay Johnson, an American technologist best known for helping to manage Barack Obama’s 2008 presidential campaign, commented that the experiment was particularly disturbing in the light of the Snowden revelations and the recently-uncovered US plot to create a ‘Cuban Twitter’ to foment unrest in the communist nation.

“We need to rethink how society relates to these networks,” wrote Johnson on Twitter. “For instance, could Mark Zuckerberg swing an election by promoting Upworthy posts two weeks beforehand? Should that be legal? Could the CIA incite revolution in Sudan by pressuring Facebook to promote discontent? Should that be legal?”

Other commentators have suggested that the study is not completely unprecedented, with technology journalist Christopher Mims tweeting: "I've discovered Facebook is involved in an even more pernicious, multi billion dollar conspiracy to manipulate users: Advertising."