Trust Modulates Speech Entrainment: Enhanced Cortical Tracking for Low-trust Speakers

Trust is a critical component of human communication, providing a foundation for understanding, information exchange, and social coordination. Much of the research on trust in speech communication has focused on how vocal characteristics impact perceived trustworthiness. However, little is known about how trust in a speaker affects the neural processing of speech. Here, we demonstrate a two-stage experimental framework to study that question using noninvasive EEG. First, participants engage in a trust-building stage, where they play an investment game with fictional characters, each paired with a distinctive voice and trustworthiness level (i.e., frequency and magnitude of lies). Next, participants engage in a story-listening stage, in which they are presented with stories from the same characters. Data acquired from 20 young adults confirm a statistically significant correlation between the perceived and actual trustworthiness of the fictional characters. Cortical speech tracking was quantified using a temporal response function analysis on the EEG data. We found that the trustworthiness established during the trust-building stage influenced the cortical tracking of speech in the subsequent story-listening stage, with lower trustworthiness corresponding to a stronger cortical tracking of speech. Interestingly, trustworthiness selectively modulated tracking strength, with no statistically significant changes in the spatial and temporal temporal response function dynamics.