 According to a delusion formation theory inspired by predictive coding, we form expectations about our experience in line with a general model of how the world is. Greater attention is paid to those events which defy expectations, as they might require a revision of our model of the world, the one we have adopted up to that point. The discrepancy between what we expect and the information we take in is an important part of the way learning occurs. When our expectations are not met, a prediction error is coded, and our model of the world is updated accordingly. A prediction-error signal is disrupted when events invested of special significance (in psychosis this may be due to dopamine dysregulation) cause us to update our current beliefs about reality, which happen to be correct. The woman who sees her father and does not get the usual autonomic response experiences an unexpected event which gives rise to a prediction error. The reaction to the signal is an attempt to explain the unexpected event (‘This is not my father!’). This results in the formation of a delusion (Corlett et al. 2007) where the formation of the delusion is principally an “error of learning” (Fine and Corlett 2016).