Perceived Trust of United States Politicians through Prosody

Trust is an essential aspect of interpersonal communication, whereby individuals make instinctive trustworthiness judgments to determine how best to interact with other involved parties. The voice is unique to every individual due to the physiology of both the vocal tract and resonance throughout the rest of the body. When listening to a stranger's voice, humans have developed an innate ability to infer the speaker's trustworthiness. This thesis investigates how individuals determine this perceived trust based on the rhetorical prosodic elements of the speaker. Previous trust literature has focused on three primary contexts for establishing trust: general, mating, and economic. Political trust literature has often used trustworthiness as a means of predicting voter outcomes. This thesis serves to bridge the gap between these areas of knowledge by understanding the level of high-stress situational trustworthiness given to United States politicians based on their prosody.

This thesis includes three experiments: Pilot Study (COVID-19 & U.S. Governors), Experiment I (COVID-19 & U.S. Governors), and Experiment II (Protests on Police Brutality & U.S. Mayors). The pilot study (N=141) confirms correlations between prosodic elements of U.S. Governor's voices and their perceived trustworthiness by listeners in both general and high-stress contexts. Experiment I attempts to replicate this correlation with two distinct participant pools (MTurk N=93 & Snowball N=91) using sound bites from eight U.S. Governor's COVID-19 reopening plans. Experiment II also uses two participant pools (MTurk N=93 & Snowball N=88) and expands on the findings from both the pilot study and Experiment I by having participants answer trust-perception questions about eight U.S. Mayors' speeches regarding protests occurring in their respective city. The mayors were selected based on the eight cities with the highest number of police killings from January 2013 through December 2019.

The results from these three experiments strengthen the argument that rhetorical prosodic elements of speech play a key role in determining the speaker's perceived trustworthiness. Linguistic elements, including articulation rate, average syllable duration, and phonation time, were analyzed; however, results from these studies show that pitch inflections (standard deviation) best explain trust perception. Vocal profiles of prominent historical figures (MLK, JFK, Bill Clinton, and Richard Nixon) were also analyzed and shown to correlate directly with these studies' findings. This thesis demonstrates that rhetorical prosodic elements have a significant influence on trust perception during high-stress situations. These findings can be used by vocal coaches and speech-language pathologists to help clients who are in roles of information dissemination during high-stress situations portray themselves as trustworthy figures.