Autonomic responses to familiar faces without autonomic responses to familiar voices: Evidence for voice-specific Capgras delusion

Introduction: Patients with Capgras delusion believe that certain individuals have been replaced by duplicates. Unlike normal people, these patients also show reduced autonomic responses to familiar faces, indicating the possibility that it is the covert processes of recognition that are impaired (Ellis, et al., 1997). It has been suggested that such patients would show normal autonomic responses to voices. An auditory parallel of this typical delusion, therefore, is theoretically possible. That is, a delusion whereby mis-recognition of the voice produces the delusional belief of duplication. Such a delusion would only occur in situations where the person is recognised by voice only; and so, even where it does exist, it would often escape diagnosis. Method: We present here a case, H.L., of what appears to be the Capgras delusion for voices in a sighted person. This case was investigated using standard skin conductance tests for face and voice recognition. Results: Consistent with this diagnosis, H.L. displays normal autonomic responses for faces but reduced autonomic responses for famous voices. Discussion: H.L. represents a previously unreported form of Capgras delusion and, further, shows dissociation between autonomic responses to faces and voices. Implications for cognitive models of person recognition are discussed.