Simultaneous belief in logically incompatible claims is linked to conspiratorial thinking, according to a study that models belief using a Bayesian framework.
The hypothesis that people who hold multiple logically incompatible beliefs are more likely to endorse conspiracy theories has been debated for over a decade. Alessandro Miani and colleagues use a new method to quantify the incoherence of an individual's beliefs. Rather than using a dichotomous classification system of belief or disbelief, the authors interpret agreement ratings as subjective degrees of belief expressed as probabilities within a Bayesian framework. It is coherent to entertain two incompatible possibilities, giving each a 50% probability of being true, but incoherent to put a 90% probability on both, because the probabilities assigned to incompatible claims cannot sum to more than 100%. The authors use this approach to analyze previously collected data from eight studies with 8,590 participants and to analyze new data from a preregistered online study of 469 Americans.
The results support the link between incoherent beliefs and conspiracism. In the reanalyzed data, the estimated probability of holding incoherent beliefs rose from 3% among the weakest conspiracy believers to 91% among the strongest. In the new survey, participants were presented with16 fictitious scenarios—such as an 8-year-old girl, the daughter of a member of the European Parliament, going missing for three days. Participants who scored higher on a standardized 5-item conspiracy mentality questionnaire were more likely to rate it as highly probable that the girl had been secretly held by her father in order to misuse public funds and, also that she had escaped an environment in which she was secretly forced into child labor, so that the two probabilities summed to more than 100%. However, the relationship between incoherence and conspiracism did not extend to every kind of explanation. When the two explanations offered were mundane accidents that could not both be true—the girl fell from a nearby cliff, or she was caught in an avalanche— conspiracy mentality scores did not predict incoherence. Conspiracism did predict incoherence, however, when one statement was the strict negation of the other and the two probabilities therefore had to sum to exactly 100%, regardless of whether the content was conspiratorial.
According to the authors, incoherence in conspiracism may reflect two components: a general component—reduced logical monitoring—that surfaces with strict-negation pairs, and a content-specific component—the worldview-driven endorsement of stories that counter official or expected narratives—that surfaces when two different conspiratorial explanations are themselves incompatible.
