Speech Perception and Cognition in Cognitive Aging
This is an advance summary of a forthcoming article in the Oxford Research Encyclopedia of Psychology. Please check back later for the full article.
The comprehension of spoken language is a complex skill that, in any language, requires the listener to map the acoustic input onto the meaningful units of speech (phonemes, syllables, words). At the sentence level, the listener must detect the syntactic structure of the utterance in order to determine the semantic relationships among the spoken words. This culminates in comprehension at the discourse and narrative level. Each higher level of analysis is thus dependent on successful processing at the prior level, beginning with perception at the phoneme and word levels.
Unlike reading, where one can use eye movements to control the rate of input, speech is a transient signal that moves past the ears at an average rate of 140 to 180 words per minute. Whatever processing cannot be completed online, as the speech is arriving, must be accomplished on a fading trace of the speech input in memory. Although seemingly automatic in young adults, comprehension of rapid speech places a heavy burden for older adults, who often exhibit a combination of reduced working memory resources and slower processing rates, as observed across a number of perceptual and cognitive domains. An additional challenge arises from reduced hearing acuity that often occurs in adult aging. A major concern is that, even with only mild hearing loss, the listening effort required for success at the perceptual level may draw resources that would ordinarily be available for encoding what has been heard in memory, or comprehension of syntactically complex speech. On the positive side, older adults have compensatory support from preserved linguistic knowledge, including the procedural rules for its use. Our understanding of speech perception in adult aging thus rests on our understanding of such sensory-cognitive interactions.