The voice of deception: Vocal strategies of naive and able liars

The aim of this research was to analyze the main vocal cues and strategies used by a liar. 31 male university students were asked to raise doubts in an expert in law about a picture. The subjects were required to describe the picture in three experimental conditions: telling the truth (T) and lying to a speaker when acquiescent (L1) and when suspicious (L2). The utterances were then subjected to a digitized acoustic analysis in order to measure nonverbal vocal variables. Verbal variables were also analyzed (number of words, eloquency and disfluency index). Results showed that deception provoked an increment in F-0, a greater number of pauses and words, and higher eloquency and fluency indexes. The F-0 related to the two types of lie-prepared and unprepared-identified three classes of liars: good liars, tense liars (more numerous in L1), and overcontrolled liars (more numerous in L2). It is argued that these differences are correlated to the complex task of lying and the need to control one's emotions during deception. The liar's effort to control his/her voice, however, can lead to his/her tone being overcontrolled or totally lacking in control (leakage). Finally, the research forwards an explanation on the strategies used by the good liar and in particular treats the self-deception hypothesis.