Attentional modulation of external speech attribution in patients with hallucinations and delusions

A range of psychological theories have been proposed to account for the experience of auditory hallucinations and delusions in schizophrenic patients. Most influential theories are those implicating the defective self-monitoring of inner speech. Some recent studies measured response bias independently of self-monitoring and found the results inconsistent with the defective self-monitoring model, but explained by an externalizing response bias. We aimed to investigate the role of attentional bias in external misattribution of source by modulating participant's endogenous expectancies. Comparisons were made between patients with paranoid schizophrenia (N=23) and matched healthy controls (N=23) who participated in two different versions of an audio-visual task, which differed based upon level of the cue predictiveness. The acoustic characteristic of voice was altered in half of the trials by shifting the pitch (distortion). Participants passively listened to recordings of single adjectives spoken in their own and another person's voice (alien) preceded by their own or another person's (alien) face and made self/non self judgments about the source. The patients showed increased error rates comparing to controls, when listening to the distorted self spoken words, misidentifying their own speech as produced by others. Importantly, patients made significantly more errors across all the invalid cue conditions. This suggests not only the presence of pathological misattribution bias, but also an inadequate balance between top-down and bottom-up attentional processes in the patients, which could be responsible for misattribution of the ambiguous sensory material.