Auditive and cognitive factors in speech perception by elderly listeners.

A key issue in research on speech perception in the elderly is whether the difficulties in understanding speech are caused by auditive and/or cognitive factors. Resolving this issue is not only scientific interest but has many practical, i.e. diagnostic and rehabilitative, implications as well. We developed a test battery comprising auditive (sensitivity, frequency selectivity and temporal resolution), cognitive (memory performance, processing speed and intellectual abilities), and speech perception tests (at the phoneme, spondee and sentence level). This test battery was administered to 72 elderly subjects (aged 60 to 93 years). The results show that the deterioration of speech perception in the elderly consists of two statistically independent components (a) a large component mainly representing the progressive high-frequency hearing loss with age which accounts for approximately two-thirds of the systematic variance of the tests of speech perception, and (b) a smaller component (accounting for one-third of the systematic variance of the speech perception tests) mainly representing a general performance decrement due to reduced mental efficiency, which is indicated by a general slowing of performance and a reduced memory capacity. Although both components are correlated with age, it was found that the balance between auditive and cognitive contributions to speech perception performance did not change with age.