Experiential features used by patients with schizophrenia to differentiate 'voices' from ordinary verbal thought

Determining how patients distinguish auditory verbal hallucinations (AVHs) from their everyday thoughts may shed light on neurocognitive processes leading to these symptoms.

Fifty patients reporting active AVHs ('voices') with a diagnosis of schizophrenia or schizo-affective disorder were surveyed using a structured questionnaire. Data were collected to determine: (a) the degree to which patients distinguished voices from their own thoughts; (b) the degree to which their thoughts had verbal form; and (c) the experiential basis for identifying experiences as voices versus their own verbal thoughts. Six characteristics of acoustic/verbal images were considered: (1) non-self speaking voice, (2) loudness, (3) clarity, (4) verbal content, (5) repetition of verbal content, and (6) sense of control.

Four subjects were eliminated from the analysis because they reported absent verbal thought or a total inability to differentiate their own verbal thoughts from voices. For the remaining 46 patients, verbal content and sense of control were rated as most salient in distinguishing voices from everyday thoughts. With regard to sensory/perceptual features, identification of speaking voice as non-self was more important in differentiating voices from thought than either loudness or clarity of sound images.

Most patients with schizophrenia and persistent AVHs clearly distinguish these experiences from their everyday thoughts. An adequate mechanistic model of AVHs should account for distinctive content, recognizable non-self speaking voices, and diminished sense of control relative to ordinary thought. Loudness and clarity of sound images appear to be of secondary importance in demarcating these hallucination experiences.