Speech Tasks and Linguistic Changes in Cognitive Decline

Abstract

This study investigated changes in speech and language associated with cognitive decline in native Korean speakers, focusing on the influence of speech task type. The aim was to find the relationship between speech tasks and the changes in linguistic characteristics that occur during cognitive decline. Fifty-one participants were recruited and classified into three groups (17 per group): normal cognitive health (NC), mild cognitive impairment (MCI), and dementia (De). Participants performed two speech tasks: a controlled picture description task, and a less structured interview task. Subsequently, acoustic (suprasegmental) and linguistic features were analyzed. Results showed that, first, there were more significant differences observed in the picture description task this is potentially due to cultural unfamiliarity with the stimulus; however, these differences primarily appeared in later-stage cognitive decline. Conversely, the interview task, while showing fewer significant variables overall, revealed changes in earlier stages (MCI). Second, articulation rate (suprasegmental) and noun-to-verb ratio (linguistic) showed significant changes in MCI compared to NC. These findings suggest that different speech tasks expose different linguistic changes in different stages of cognitive decline, with articulation rate and noun-to-verb ratio in spontaneous interview speech potentially serving as early indicators. In conclusion, while cognitive decline impacted both acoustic and linguistic features, the picture description task primarily reflected later-stage changes whereas the interview task offered insights into earlier changes, highlighting the importance of task selection in cognitive assessment using speech analysis. Future research with a larger sample size and more culturally homogeneous samples of culturally relevant picture description stimuli is recommended.