Delusional Unreality and Predictive Processing

Background: Phenomenological psychopathologists have recently highlighted how people with delusions experience multiple realities (delusional and non-delusional) and have suggested this double bookkeeping cannot be explained via predictive processing. Here, we present data from Kamin blocking and extinction learning that show how predictive processing might, in principle, explain a pervasive sense of dual reality.

Methods: This cross-sectional study involved three participant groups: patients with schizophrenia (SZ; n=42), healthy participants with elevated esoteric beliefs (EEB; clairaudient psychics; n=31), and heathy controls (with neither illness nor significant delusional ideation, n=62). We examined belief formation using a Kamin blocking causal learning task with extinction, and delusions with the 40-item Peters Delusion Inventory, specifically the unreality item: "Do things around you ever feel unreal, as though it was all part of an experiment?" as a proxy for unreality experiences and beliefs. A clinician also assessed symptoms with a structured clinical interview.

Results: Some people with schizophrenia did not report a sense of unreality, and some people with EEB (but no psychotic illness) reported unreality experiences. No HC endorsed them (despite endorsing other delusion-like beliefs). Unreality experiences in clinical delusions and non-clinical delusion-like beliefs were associated with different types of aberrant prediction error processing.

Conclusions: These data suggest how predictive processing might explain the sense of unreality. They indicate that different prediction error dysfunctions are associated with delusions with different contents. In this case we have used predictive processing to address a salient issue raised by phenomenological colleagues, namely the impact of psychosis on experiences of and beliefs about reality.