Yesterday, in embarrassing news for Facebook, The Guardian reported on leaked documents that reveal the site’s “trending” sidebar is heavily based on pesky human intuition, rather than cold objective algorithms. Funnily enough, the Facebook page explaining trending topics admits no such thing, saying, “The topics you see are based on a number of factors including engagement, timeliness, Pages you’ve liked and your location.”

See related Facebook criticised over online harassment project Facebook shows that certain jobs run in the family Psychology and the courtroom: the scientific issues with our justice system The leaked documents revealed that editors can inject topics that aren’t generating enough interest on their own, as well as blacklist topics that are considered inappropriate. On top of that, the site is said to consider ten sites as having particular editorial authority: BBC News, CNN, Fox News, The Guardian, NBC News, The New York Times, USA Today, The Wall Street Journal, Washington Post and Yahoo.

Human intervention isn’t necessarily a bad thing, but the leak comes at an awkward time for Facebook, as Gizmodo posted a confession from a former news editor at the social network who reported an institutional bias against conservative news sites, writing, “I’d come on shift and I’d discover that CPAC or Mitt Romney or Glenn Beck or popular conservative topics wouldn’t be trending because either the curator didn’t recognise the news topic or it was like they had a bias against Ted Cruz.”

“I believe it had a chilling effect on conservative news.”

Unsurprisingly, Republicans aren’t happy about this revelation, and Senator John Thune has demanded an explanation from Zuckerberg.

Well, he’s got one. In a public post, Zuckerberg announced a full investigation into accusations of a liberal bias on the site, writing: “We have found no evidence that this report is true. If we find anything against our principles, you have my commitment that we will take additional steps to address it.”

He added that the company would invite “leading conservatives and people from across the political spectrum” to discuss the issue soon, to ensure that “our platform stays as open as possible”.

While the accusations are certainly damaging – Zuckerberg would have been unlikely to respond if they weren’t – bias is one of the easiest accusations to throw around, and the internet is littered with them. An algorithm could remove that, depending on how it’s programmed, but a purely algorithmic solution can’t guarantee a selection that users will actually be interested in.

As someone who has been accused of being a Conservative Party cheerleader more times than someone with my voting and writing record should have, I personally think people scream bias whenever their views aren’t parroted back at them, but hey, that’s probably just my bias talking.

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Images: Alessio Jacona and Find Your Search used under Creative Commons