Group psychological roots of conspiracy beliefs in the UK, US, and Turkey

Countries vary greatly in conspiracy beliefs and vaccine hesitancy. Drawing from cultural evolutionary theory, we examined the variation in outgroup mistrust, psychological reactance (a measure of nonconformity), conspiracy beliefs and vaccine hesitancy across three countries with different historical, political, and socio-cultural contexts. We tested the predictive role of outgroup mistrust and reactance in explaining conspiracy beliefs using rich, demographically representative cross-cultural data of over 4500 participants from the UK, US, and Turkey and hierarchical linear models. We used two measures of conspiracy beliefs: conspiracy mentality and belief in health conspiracies. As predicted, outgroup mistrust and psychological reactance had the largest effect sizes for belief in health conspiracies, and reactance had the largest predictive power for conspiracy mentality. Control variables such as belief in science, political orientation, religiosity, and demographic factors had minimal effects. Turkish participants had the highest conspiracy mentality and health conspiracy scores, along with higher levels of outgroup mistrust and reactance, while UK participants had the lowest. Belief in health conspiracies and conspiracy mentality were strongly associated with vaccine hesitancy across all three countries, with the highest hesitancy in Turkey. Moderation analyses revealed that outgroup mistrust was a stronger predictor of health conspiracy beliefs in Turkey, while reactance had a greater impact in the UK and the US. These results suggest that outgroup mistrust and signalling non-conformity play a crucial role in conspiracy beliefs and variations in their levels across cultures. Based on these insights, we propose strategies to address conspiracy beliefs and vaccine hesitancy.