Hallucination- and delusion-like experiences are associated with increased precision of sensory evidence in perceptual inference

Abstract

BACKGROUND AND HYPOTHESIS. Predictive coding proposes that psychotic phenomenology stems from alterations in precision encoding of neural signals. Previous studies indicate links between psychotic-like experiences, increased sensory evidence precision, and reduced data-gathering in probabilistic reasoning. If sensory precison is increased in bottom-up signalling, we would expect it to be present in perceptual inference. Here, we investigated whether increased sensory precision and reduced data-gathering relate to subclinical psychotic-like experiences in perceptual inference. STUDY DESIGN. We fitted drift-diffusion models to performance on the Random Dot Motion task (RDM) of 191 participants from the general population. Drift rate (a proxy for precision of sensory evidence) and decision threshold parameters could vary: 1) between groups with higher vs. lower levels of psychotic phenotypes; 2) as dependent variables in a regression model having psychotic phenotypes as predictors. Using the beads task, we also attempted to replicate the finding that reduced data-gathering is associated with delusional ideation. STUDY RESULTS. Both delusion- and hallucination-like experiences were associated with higher precision of sensory evidence (higher drift rates) in RDM. Hallucination-like experiences were also associated with lower decision thresholds. In probabilistic reasoning, we did not find reduced data-gathering associated with any psychotic-like experiences. CONCLUSIONS. Our findings suggest that psychotic-like experiences are associated with increased precision of sensory evidence when discriminating motion direction. A higher hallucinatory phenotype was also linked to reduced gathering of information. These specificities of information processing might represent underlying decision-making mechanisms contributing to the formation of psychotic phenomenology in the general population.