Investigating Speech Rate Alignment in Individuals with Traumatic Brain Injury

The alignment of verbal and nonverbal behaviors is important for conversation. Research has shown that interactive behavior alignment is commonly impaired following a traumatic brain injury (TBI), and the ability for an individual with TBI to align their speech rate with their conversational partners can be affected. This non-convergence of speech rates can lead to negative social outcomes, including perceptions of decreased social connectedness and decreased willingness of conversational partners to engage in conversation. Despite these negative outcomes, researchers have yet to discover a therapeutic technique to increase speech rate convergence, and in turn, lead to positive social outcomes during conversation. Additionally, research has specifically focused on speech rate convergence in individuals with moderate-to-severe TBI and not individuals with mild TBI (mTBI). It is currently unclear whether speech rate convergence is also affected in individuals mTBI.Speech entrainment (SE) is a therapeutic tool that involves the real time mimicking of an audiovisual (AV) stimulus. Although this task was originally developed to improve the fluency of speech in individuals with non-fluent aphasia, this study trialed SE with individuals with TBI, as it requires repeated alignment of ones speech rate with anothers.For this study, participants with TBI and mTBI engaged in conversations with a familiar partner before and after engaging in 30 minutes of SE. During the task, participants mimicked AV stimuli presented at various speech rates (unmodified at c. 2 syllables/s and accelerated to c. 3.5/syllables/s and c. 5 syllables/s). After the task, observers rated portions of each conversation on degree of perceived rapport between participants and their conversational partners.Results showed that individuals with mTBI entrained to a greater degree to stimuli compared to the moderate-to-severe TBI group at the slow and medium rates. Additionally, all participants, regardless of TBI severity, demonstrated greater entrainment to the slow rate AV stimuli compared to the medium. The degree of speech rate convergence, however, did not appear to change systematically between pre- and post-treatment conversations. Finally, based on observers ratings, conversations with speech rate convergence were unexpectedly perceived as less natural and less favorable compared to conversations with non-convergence of speech rate