A key feature of psychopathy is the ability to deceive, manipulate, and con the unwary, while seeming to be perfectly sincere. Is this impression of sincerity achieved solely through body gestures and facial expression, or is there also something different about the voice quality of psychopaths? We analyzed the acoustic characteristics of speech in 20 male offenders (10 psychopaths and 10 nonpsychopaths), assessed with the Psychopathy Checklist--Revised (Hare, 1991). We used a computer program developed by Alpert, Merewether, Homel, Martz, and Lomask (1986) to measure variations in amplitude and prosody. Results indicated that psychopaths spoke more quietly than controls and did not differentiate, in voice emphasis, between neutral and affective words. These findings are consistent with the developing view that psychopaths are insensitive to the emotional connotations of language. In addition, their vocal characteristics may be part of a self-presentation mode designed to manipulate and control interpersonal interactions.
Louth, S. M., Williamson, S., Alpert, M., Pouget, E. R., & Hare, R. D. (1998). Acoustic Distinctions in the Speech of Male Psychopaths. Journal of Psycholinguistic Research, 27(3), 375–384. https://doi.org/10.1023/A:1023207821867