Vocal pitch manipulation and credibility in the courtroom: differences between male and female expert witnesses

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University of Alabama Libraries

Nonverbal cues that occur during trial testimony have been shown to make a difference in juror ratings of expert witness credibility. Vocal pitch is an important nonverbal cue that has not been examined within the courtroom context. A limited number of studies have manipulated the vocal pitch variable in settings other than the courtroom. Results from this research provide preliminary evidence for a vocal attractiveness stereotype. Further, other studies found that a lower vocal pitch preference exists among most listener participants. The present study manipulated vocal pitch in order to assess whether the low pitch preference exists for mock jurors' ratings of expert testimony credibility and if this preference is held to the same degree for both male and female experts. A computerized voice transformation program was used to shift pitch frequencies of audiotaped testimony from a male and a female mock expert. Mock jurors were randomly assigned to one of six testimony conditions and asked to rate the credibility of the witnesses using the Witness Credibility Scale (WCS). Gender was not found to significantly moderate the relationship between vocal pitch and credibility; however, a main effect was found for gender on total witness credibility, with males rated as significantly more credible than females. While there was no main effect for vocal pitch on total witness credibility score, pitch was found to make a difference on knowledge and confidence subscales as well as several individual item scores of the WCS. This research adds to a growing body of information available to trial consultants and other coaches preparing experts for the witness stand.

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