HESP Seminar: Avery Vess

Honors Thesis Defense: Following the Conversation: Impacts of Set-Shifting and Topic-Shifting in Healthy Adults and Individuals with Traumatic Brain Injury

Abstract: Conversational discourse difficulties, including issues with processing topic structure, are common in individuals with traumatic brain injury (TBI), even after receiving speech therapy interventions targeting word and sentence-level skills. This persistence suggests a gap in understanding how non-linguistic cognitive processes influence conversation. This study investigates whether cognitive mechanisms, specifically set-shifting, contribute to processing topic shifts in conversation. Experiment 1 examines if topic switches exhibit behavioral signatures of set-shifting, such as longer response onset latencies and decreased information content efficiency. Results show no differences between responses to new and same topics. This raised questions about the impact of experimental design, for example, whether other linguistic levels such as syntactic complexity or motor-speech planning, are impacted by being on the receiving end of a topic shift.  Experiment 2 evaluates the impacts of topic shifts in natural conversation on language production in healthy adults and TBI patients, measuring productivity, semantic complexity, syntactic complexity, and fluency. Both groups exhibit costs in word and verb usage, revisions/rephrasing, and pauses per syllable when shifting topics. I will suggest that the reduced complexity and increased planning difficulty of responses when encountering topic shifts in conversation reflect behavioral costs in non-linguistic tasks that require set-shifting.