Signal discrimination in the psychotic phenotype: increased sensory precision and reduced decision threshold associated with psychotic-like experiences.

Abstract

Psychotic-like experiences may reflect disrupted signal discrimination, whereby individuals overinterpret noisy sensory input as meaningful. Drawing on predictive coding accounts, we investigated whether increased sensory precision and reduced data-gathering relate to psychotic-like experiences in a signal discrimination task. We fitted drift-diffusion models to Random Dot Motion (RDM) task data completed by 191 participants. We estimated drift rate and decision threshold: (1) across groups differing in psychotic phenotypes, and (2) as outcomes in regression models with psychotic-like experiences as predictors. Drift rate measures evidence gain and, in this task, can be considered an approximate measure of sensory precision. We also tested whether reduced data-gathering on the beads task replicated prior associations with psychotic phenotypes. Hallucination- and delusion-like experiences were associated with increased drift rates. Hallucination-like experiences also predicted lower decision thresholds. In the beads task, psychotic-like experiences correlated with higher confidence ratings but not with reduced data-gathering. Our findings indicate that psychotic-like phenomenology is linked to increased precision of signal discrimination and reduced decision thresholds. Overprecise signal discrimination and lower decision thresholds may bias perceptual inference toward false positive detections, potentially leading to anomalous experiences.