Date of Award

January 2024

Document Type


Degree Name

Medical Doctor (MD)



First Advisor

Albert Powers


Hallucinations, commonly defined as perceptions occurring in the absence of corresponding sensory stimuli, are a core symptom of psychotic disorders, but the term also encompasses a broad range of diverse phenomena occurring in many circumstances. A comprehensive theory explaining hallucinations must thus explain its prevalence within syndromic contexts, but also be generalizable to different conditions. The insight that hallucinations could be induced experimentally and the development of computational modeling has allowed for rigorous research into the neural mechanisms underlying these perceptual experiences. Utilizing classical conditioning, recent studies using the Conditioned Hallucinations task have demonstrated that hallucinations arise from the overweighing of prior beliefs relative to incoming sensory data. We administered this task to a novel cohort composed of Healthy Controls (n=9), individuals at Clinical High Risk for psychosis (n=16), First Episode psychosis patients (n=8), and Chronic psychosis patients (n=8). Results failed to replicate previously shown differences in conditioned hallucination rates or prior weighting, and thus no meaningful trend could be found along the course of illness trajectory. However, perceptual confidence was found to differ significantly between groups based on clinical stage and hallucinatory status. These positive and negative findings highlight the need for further investigation into the perceptual and metacognitive aberrations of psychosis and hallucinations.


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