Introducing the Opinion-Overconfidence Effect: How Publicly Expressing Opinions on Social Media Increases Confidence Without Knowledge

Social media platforms are gamified to promote opinion sharing on any topic, irrespective of users’ subject knowledge. Potential effects of uninformed opinion-sharing have yet to be fully explored. We propose that one such effect is an opinion-overconfidence effect: an increase in topic-specific confidence after posting an opinion on that topic. Here, we present the first empirical evidence for the opinion-overconfidence, in the form of three pre-registered studies. Our findings support the existence of an effect, driven by the act of writing one’s opinion rather than of posting one’s opinion publicly. However, we do find linguistic differences between opinions written privately and those for a public audience, which could be interpreted as evidence for a message-release component to the effect. As overconfidence is predictive of extremist political ideologies and conspiracy theory belief, a population-wide increase in overconfidence due to social media use could have devastating effects on democratic societies.