Ageing, Cognitive Deterioration, and Verbal Disfluency: A Case Study in Thailand.

Studies on the effects of ageing on cognitive functioning and verbal performance were often conducted in western population with mixed results. More recent research suggested roles of socio-individual factors in modulating the age effects. The present study employed different tasks including a working memory test, a picture naming task, and a storytelling task to investigate the ageing effects in Thai population, the underrepresented group. Socio-individual factors including education, stress, and sleep hours were also included, and age was treated as continuous variable in the analyses. From a working memory test, it was found that with every increase in age, there was a decline in working memory capacity. To test whether cognitive deterioration resulting from age affects verbal performance, and whether each socio-individual factor could directly affect verbal performance, a picture naming task and a storytelling task were conducted. It was found that age was inversely related to disfluency in terms of pause filler production, self-monitoring, and self-repair. None of socio-individual factors was significant. The study calls for more careful analyses on speech-disfluency variables.