Voice identity discrimination in schizophrenia

Voices provide a wealth of socially-relevant information, including cues to a speaker's identity and emotion. Deficits recognising emotion from voice have been extensively described in schizophrenia, and linked specifically to auditory hallucinations (AH), but relatively little attention has been given to examining the ability to analyse speaker identity. Hence, the current study assessed the ability to discriminate between different speakers in people with schizophrenia (including 33 with and 32 without AH) compared to 32 healthy controls. Participants rated the degree of perceived identity similarity of pairs of unfamiliar voices pronouncing three-syllable words. Multidimensional scaling of the dissimilarity matrices was performed and the resulting dimensions were interpreted, a posteriori, via correlations with acoustic measures relevant to voice identity. A two-dimensional perceptual space was found to be appropriate for both schizophrenia patients and controls, with axes corresponding to the average fundamental frequency (F0) and formant dispersion (Df). Patients with schizophrenia did not differ from healthy controls in their reliance on F0 in differentiating voices, suggesting that the ability to use pitch-based cues for discriminating voice identity may be relatively preserved in schizophrenia. On the other hand, patients (both with and without AH) made less use of Df in discriminating voices compared to healthy controls. This distorted pattern of responses suggests some potentially important differences in voice identity processing in schizophrenia. Formant dispersion has been linked to perceptions of dominance, masculinity, size and age in healthy individuals. These findings open some interesting new directions for future research.