Psychotic experiences induced in deluded patients using distorted auditory feedback.

The effect of hearing immediate auditory feedback of their own voice distorted in pitch was examined in 21 patients with a diagnosis of schizophrenia. Patients frequently reported that they heard a voice "speaking when I speak" and often attributed this "other" voice to an external agent: "I think it's an evil spirit speaking when I speak." The frequency of making these ''other''attributions was significantly related to degree of pitch distortion (rho = 0.62, P <.01) and to current severity of delusions (rho = 0.62, P <.01). However, the relationship with hallucinations was not significant (rho = 0.40) and there was no relationship with negative features such as psychomotor retardation. We conclude that the "hallucination-like" reports elicited by our paradigm resulted from an interaction between an unusual perceptual experience (distorted auditory feedback) and an abnormal mechanism for belief formation present in deluded patients. This formulation suggests a close relationship between delusions and hallucinations.