A Way Beyond Fact-Checking? Social Norms, Credibility, and the Limits of Containing Conspiracy Theories

Conspiracy theories that delegitimize democratic institutions pose a great challenge for European democracies, yet the effectiveness of different interventions (particularly those addressing the social and normative dimensions of conspiratorial belief) remain insufficiently understood. While a wealth of research shows that factual corrections tend to improve belief accuracy, their effects are sometimes short-lived and weak in regard to behavioral outcomes. Moreover, conspiratorial beliefs are usually more deeply cemented than other types of misperceptions. Building on recent work emphasizing credibility signals and social norms in belief formation and diffusion, this paper investigates how various interventions shape conspiracy belief and political behavior across diverse contexts. We present a randomized survey experiment in eight European countries focusing on a widely circulated conspiracy narrative that questions the legitimacy of European integration and migration policies. Participants are randomly assigned to one of various conditions: a control group, a factual correction, a descriptive social norm, an injunctive social norm, and an epistemic penalty treatment highlighting the reputational costs associated with endorsing conspiratorial claims. The design allows us to isolate the effects of accuracy-based corrections from norm-based and social-signalling interventions, while holding the conspiratorial content constant. Primary outcomes include post-treatment conspiracy belief, perceived credibility of the message, and other variables related to political behavior. Analytically, we estimate intention-to-treat effects of the different interventions and then turn to assess the mediating role of perceived credibility of the different treatments on the outcomes of interest (e.g., belief in the conspiracy after each treatment) to distinguish between changes in responses driven by Bayesian-consistent information updating and changes driven by other considerations. Moreover, by comparing treatment effects across various countries and political predispositions, this paper evaluates the external validity and contextual robustness of different strategies aimed at keeping conspiracy theories at bay. More broadly, our work contributes to democratic resilience research by clarifying how norm-based reputational interventions may weaken the incentives to endorse and disseminate political conspiracy theories.