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Reasoning biases have been identified in deluded patients, delusion-prone individuals, and believers in the paranormal. This study examined content-specific reasoning and delusional ideation in believers in the paranormal. A total of 174 members of the Society for Psychical Research completed a delusional ideation questionnaire and a deductive reasoning task. The reasoning statements were manipulated for congruency with paranormal beliefs. As predicted, individuals who reported a strong belief in the paranormal made more errors and displayed more delusional ideation than skeptical individuals. However, no differences were found with statements that were congruent with their belief system, confirming the domain-specificity of reasoning. This reasoning bias was limited to people who reported a belief in, rather than experience of, paranormal phenomena. These results suggest that reasoning abnormalities may have a causal role in the formation of unusual beliefs. The dissociation between experiences and beliefs implies that such abnormalities operate at the evaluative, rather than the perceptual, stage of processing.
Lawrence et al. (Mon,) studied this question.