The mainstream is shrinking. Trust in mainstream media is falling. Mainstream politicians are seeing their majorities eroded by new parties on the left and right. 2016 was a year of unanticipated political decisions: the election of Donald Trump, the decision to leave the EU, even the re-election of Jeremy Corbyn as Labour Party leader. Repeatedly, long odds gave way to disbelief as the mainstream was rejected in favour of something radical and disruptive. Even the very idea of ‘facts’ has been shaken: by December 2016 the words ‘post-truth’ were on the lips of commentators around the world, eventually becoming the Oxford Dictionaries word of the year.

This has been mirrored and reflected in the landscape of political discussion. There has been, over the last decade, a dramatic change in the way political ideas, news and debates occur. When fingers have been pointed in blame, they have almost invariably been pointed at the internet.

The web is almost certainly the primary source of information for people living in the UK in 2017. Yet the idea that the breadth of information we are shown online is being technologically narrowed – filtered by algorithms and tailored by our increasing power to shape the news we see – has become a topic of keen debate in 2016. In the wake of the year’s major political and cultural events, the way we use the internet to inform our news and views has been questioned. The charge levelled at the great online content providers is this: that their platforms are built to over-provide users with information that they agree with, or even to supress the content they do not. With so much of our politics now playing out online, critics have claimed that this kind of confirmation bias is causing the balkanization of political discussion, a strengthening of existing biases and political prejudices, and a narrowing of political, cultural and social awareness. This is the ‘Echo Chamber’.

To do this, we collected Twitter data from 2,000 users who openly publish their support for one of four political parties in the United Kingdom (and 500 who didn’t). We subjected these tweets to a series of analyses, investigating whether there was evidence for an echo chamber effect in the way these users communicated online in relation to their political party affiliations. Each piece of analysis turned on a different piece of metadata – a datapoint attached to a tweet such as the links contained within it or the user it was sent in reply to.

We found:

  1. Political groups in the United Kingdom are reflected in online communities of varying levels of cohesion, and at times the term ‘echo chamber’ is useful in describing how they engage with other users on Twitter.
  2. People with the same party political affiliations tend to share news on Twitter from sites that are ideologically consistent with their party political affiliation.
  3. The degree to which people share news from sites that are consistent with their party political affiliation differs by party.
  4. People with more polarized political affiliations tend to be more inward-facing than people with more moderate political affiliations. In short, the echo chamber effect is more pronounced the further a group is from the centre.
  5. Groups are more likely to interact with other groups who are ideologically aligned with them: our two left parties shared more similar content and interacted with each other more often than they did with the two parties on the right.
  6. Breaking news, and non-party political views, have broad cross-party engagement, while news and views with strong political perspectives are disproportionately shared with those who share those perspectives.
  7. Discussions of issues, when measured by words used or by hashtags used, show that certain topics are much more prevalently discussed by certain political groups than by others, and these topics are consistent with those parties’ key political interests.

The paper suggests that there is a strong connection between a user’s ideology and the users and news sources they interact with, and that offline beliefs play a key role in the way users behave online, a hypothesis that is often assumed but rarely measured.  It also adds evidence that users with published support for political parties in the UK are more likely to share ideologically-aligned media, are more likely to keep within ideologically-aligned communities, and that this tendency increases the further the set of beliefs lies from the mainstream. It underlines the importance of mainstream news as a place where social media users with differing political viewpoints are most likely to encounter one another.