The Changing Weight of Expectation: How Shifting Priors Underpin Variability in Hallucination Frequency.

Abstract

The predictive processing framework encourages us to consider perception as arising from the integration of pre-existing knowledge with current sensory input (1). It formulates hallucinations - percepts without accompanying stimuli - in terms of increased weighting of predicted over actual input and thereby suggests an explanation of the computational mechanisms underlying such experiences. Several studies of individuals with, or prone to, hallucinations have exploited this framework and have suggested ways in which the balance between prediction and input may be altered. In this issue, Kafadar and colleagues (2) elegantly extend this work in three ways: first, they replicate a previous observation (3) that individuals experiencing auditory-verbal hallucinations show a greater influence of prediction on auditory experience; second, they show that this tendency reflects individuals’ current levels of auditory hallucinations rather than a persisting trait. Third, they validate an online version of their task, which may prove convenient in its future use.