The effects of age-related sensory and cognitive change on speech and language comprehension

This dissertation investigated how age-related changes in hearing and cognitive abilities affect spoken language comprehension. The theoretical framework is drawn from both hearing science and cognitive psychology. The research questions were not framed in terms of whether declines in speech understanding are due to cognitive decline or hearing decrements. Rather, this dissertation explored how each of these may contribute to age-related changes in speech and language comprehension.; Experiment 1 provides support for the effortfulness hypothesis, the idea that hearing loss makes you work harder to achieve perceptual success, at a cost of resources for encoding into memory what has been heard. Experiment 2 describes a divided attention task where older hearing-impaired adults showed a differentially greater drop on secondary (tracking) task performance than the older normal hearing adults. This may reflect the greater difficulty of the primary (or memory) task imposed by the perceptual burden of the hearing loss. Experiment 3 emphasizes the importance of objective hearing measurement for researchers working with older adult participants.; Most of the age-related difficulties with speech and language comprehension occur seen in poor listening situations where the acoustics and/or speech signal are compromised. Experiment 4 shows that hearing loss in older adults produced significant effects in memory for speech heard in background noise. These effects were influenced by the type of background noise (how many speakers in the background) as well as the severity of the hearing loss. It has been hypothesized that difficulty in background noise arises in part from age-related changes in the central auditory system that affect auditory processing abilities. The reliability of auditory processing tests on the elderly has been the topic of some debate arising from the uncertainty of how these tests might be affected by peripheral hearing loss commonly seen in older adults. In Experiment 5, a battery of auditory processing tests were administered to older adults with a range of hearing sensitivity. Results suggest that peripheral hearing loss influenced performance on selected tests.; Older adults have greater difficulty listening to rapid speech. The underlying factors are assumed to include age-related slowing as well as hearing declines. Experiment 6 presents evidence for the effects of aging and hearing on comprehension of time-compressed speech, and the ability to benefit from additional processing time afforded by the restoration of time back into the speech.