Different combinations of perceptual, emotional, and cognitive factors predict three different types of delusional ideation during adolescence.

Although adolescence is a particularly sensitive period for the development of schizotypy (Walker and Bollini [Schizophr Res 54:17-23, 2002]), there has been relatively limited research on the psychological factors that specifically predict delusional beliefs during adolescence. We studied 392 school students aged 11 to 16 years with a battery of behavioral and psychometric measures. Anxiety and negative-other schemas mediated the relationship between hallucinatory experiences and paranoid beliefs; anxiety mediated the relationship between hallucinatory experiences and grandiose beliefs; anxiety and self-negative schemas mediated the relationship between hallucinatory experiences and "other delusions" (Schneiderian/reference/misidentification). Furthermore, a jump-to-conclusions (JTC) bias moderated the relation between anxiety and other delusions: scores in the other delusions category were highest in adolescents who had both high anxiety and a JTC bias. Sex and age had only weak effects upon delusional belief. Our findings provide novel data by highlighting the different factors that underpin three delusional subtypes during the vulnerable period of adolescence.

Subclinical delusional ideation and appreciation of sample size and heterogeneity in statistical judgment.

Previous studies demonstrate that people high in delusional ideation exhibit a data-gathering bias on inductive reasoning tasks. The current study set out to investigate the factors that may underpin such a bias by examining healthy individuals, classified as either high or low scorers on the Peters et al. Delusions Inventory (PDI). More specifically, whether high PDI scorers have a relatively poor appreciation of sample size and heterogeneity when making statistical judgments. In Expt 1, high PDI scorers made higher probability estimates when generalizing from a sample of 1 with regard to the heterogeneous human property of obesity. In Expt 2, this effect was replicated and was also observed in relation to the heterogeneous property of aggression. The findings suggest that delusion-prone individuals are less appreciative of the importance of sample size when making statistical judgments about heterogeneous properties; this may underpin the data gathering bias observed in previous studies. There was some support for the hypothesis that threatening material would exacerbate high PDI scorers' indifference to sample size.