Individual Differences in Belief Updating and Phasic Arousal Are Related to Psychosis Proneness

Many decisions entail the updating of beliefs about the state of the environment, a process that may go awry in psychosis. When environments are subject to hidden changes in their state, optimal belief updating requires non-linear modulation of sensory evidence, which may be subserved by pupil-linked, phasic arousal. Here, we analyzed behavior and pupil responses during evidence accumulation in a changing environment in a community sample of human participants and assessed their subclinical psychotic experiences (psychosis proneness). Subjects most prone to psychosis showed overall less flexible belief updating profiles, with diminished weighting of late evidence. These same subjects also exhibited overall smaller pupil responses and less reliable pupil encoding of computational variables governing the adaptive belief updating. The observed changes in belief updating and arousal dynamics may account for the emergence of cognitive biases in psychotic psychopathology. Our results open a new window on the pathophysiology of mental disorders. ### Competing Interest Statement The authors have declared no competing interest.