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Faculty of Economics

The prominent role of social media exacerbates the tendency of voters to disregard information contrary to their beliefs, according to two University of Cambridge researchers. They say this behaviour risks shock election outcomes.


Dr Edoardo Gallo & Alastair Langtry

“In recent years we have seen online social networks become increasingly prominent in political campaigns, and this has coincided with shock election outcomes in several countries” says Dr Edoardo Gallo from the Faculty of Economics. “We think this is partly down to how confirmation bias – people’s tendency to ignore information contrary to their beliefs – affects the way we learn from others. This biased information may induce shock election outcomes, and it can also push fringe media organisations to take even more extreme standpoints. The implications for society as a whole are concerning.”

Confirmation bias is a powerful filter on how we process information, and leads us to ignore challenging ideas and opinions we find uncomfortable. “Social media makes it easier than ever to stop listening to someone – you’re never further than one ‘unfollow’ button away from never having to listen to someone again. If an idea makes you uncomfortable, social media will help you filter it out” says Alastair Langtry, a PhD economics researcher at the University of Cambridge.

Their paper, Social networks, confirmation bias and shock elections, explores the effects of confirmation bias on how we learn as a society. It shows that with confirmation bias we will take longer to reach a consensus on any issue, and that who is influential in determining this consensus can change. Additionally, confirmation bias increases polarisation in society during this process – so trying to reach common ground can be more fraught as well as being slower.

In the context of elections, a consequence of these results is that surprise outcomes become more likely. “Swing voters are often crucial in determining an election, and their choices become more unpredictable if they become trapped in an echo chamber” Dr. Gallo says. “Confirmation bias restricts the sources of information they listen to, and can lead them to make the wrong choice. Wrong here means a different choice than they would make if they listened to both sides with an open mind.”

With confirmation bias, it’s easier for some media organisations to take on more extreme standpoints. “Alienating a large number of potential listeners by choosing a very extreme position isn’t so much of a problem if those people would never have been willing to listen to a more moderate position anyway. Fringe media organizations face less competition from more mainstream outlets when confirmation bias is stronger – there are fewer people who might start listening to that fringe organisation if it were a little less extreme” says Alastair.

He adds; “as the US is preparing to vote, one candidate seems to be clearly ahead in the polls. In the world of social media, however, you should never count someone out – confirmation bias could still deliver a shock result.”

The full paper, is available at:



US Election



Social Media