Effects of working memory capacity on understanding rate-altered speech

Abstract

Age-related declines in language processing have been attributed in part to generalized cognitive slowing. Because of this slowing, it has been suggested that older adults' sentence comprehension might be facilitated by reducing the rate at which sentences are spoken. Research, however, has failed to reliably show that speaking slowly enhances comprehension. the present study explores the hypothesis that declines in working memory (WM) would actually counteract any benefits derived from a reduction in speech rate. That is, at a slower than normal speech rate, more demands are placed on WM since information must be retained over a longer duration. the comprehension of normal and slow speech was examined for three Alzheimer's subjects, each presenting a unique profile of WM capacity. Results suggest that the effect of speech rate on comprehension is determined by the extent of WM capacity: A slow speech rate was beneficial only for the subject with the most preserved WM; speech rate did not affect comprehension for the subject with moderately impaired WM; and a slow speech rate was actually detrimental for the subject with the most severe WM impairment. the findings demonstrate the value of considering the involvement of multiple cognitive domains when assessing language processing abilities.