Perceptual identification of voices under normal, stress and disguise speaking conditions

A number of authors have contended that, at present, the human listener constitutes the most accurate “system” for correctly identifying individuals from their speech–especially if tape recorded materials are used. Other investigators have indicated that listeners do not have to know the speakers in order to make highly accurate judgements of this type. The present experiments attempt to (1) estimate listeners’ capabilities in this area and (2) assess the importance of the auditors being acquainted with the talkers. Speakers were 10 adult males who recorded speech samples under three types of speaking conditions: (a) normal, (b) stress and (c) disguise. Three classes of listeners were utilized: (a) a group of individuals who knew the talkers, (b) a group that did not know the talkers but were trained to identify them and (c) a group that neither knew the talkers nor understood the language spoken. The analyses indicate that the performances among the groups were significantly different. Listeners who knew the talkers performed best while the non-English speaking listeners produced the lowest level of correct identification. The “middle” group, i.e. the English speaking listeners who did not know the talkers, was divided into two subgroups by the method of extremes. However, even in this case, the most competent of the subgroups still was significantly less able to identify the talkers than were the listeners who knew them; the least competent subgroup performed at about the same level as the auditors that did not speak English. Finally, analysis of the three types of speech revealed that the normal and stress conditions were not statistically different relative to the identification task whereas the disguised productions produced fewer correct identifications.