Reasoning biases in paranoid ideation and conspiracy beliefs: evidence within the general population

Paranoid ideation – that is ideas of reference or persecution (Freeman, 2016) – is not merely seen in persecutory delusions but can also be observed, although to a lesser degree, within the general population. Reasoning biases in information collection and integration have been proposed as one set of risk factors for paranoid ideation, but longitudinal evidence on this relationship in the general population is scarce. To address this shortcoming, the current thesis investigates how different reasoning biases are associated with paranoid ideation in various temporal distances. This thesis extends this line of research to the study of conspiracy beliefs by examining specific biases as concomitants of coronavirus conspiracy beliefs. I present two studies examining individuals from the general population (n = 1,184, n = 75), which demonstrated that a higher jumping-to-conclusions bias was associated with increases in paranoid ideation over several months and that a higher belief inflexibility bias predicted increases in paranoid ideation over the next few hours. Regarding conspiracy beliefs, a third study (n = 1,684) showed that endorsement of conspiracy beliefs was accompanied by a higher jumping-to-conclusion bias, a higher bias against integrating disconfirmatory evidence, a more liberal acceptance of unplausible hypotheses, and a higher stated possibility of being mistaken. In some associations, a quadratic relationship described the examined association better. The results presented in this thesis suggest that different reasoning biases may serve as long-term or short-term predictors of paranoid ideation and as concomitants of conspiracy beliefs in the general population. These findings provide a fruitful starting point for subsequent investigations, which may eventually call for amendments to paranoia and conspiracy belief models. Future studies should further elucidate the role of reasoning biases in paranoid ideation in different temporal intervals, specifically in individuals burdened by their beliefs. If supported by further longitudinal and experimental research, theoretical models of conspiracy beliefs may be complemented to account for reasoning biases as risk factors.