Use of context by young and aged adults with normal hearing.

Abstract

Word recognition in sentences with and without context was measured in young and aged subjects with normal but not identical audiograms. Benefit derived from context by older adults has been obscured, in part, by the confounding effect of even mildly elevated thresholds, especially as listening conditions vary in difficulty. This problem was addressed here by precisely controlling signal-to-noise ratio across conditions and by accounting for individual differences in signal-to-noise ratio. Pure-tone thresholds and word recognition were measured in quiet and threshold-shaped maskers that shifted quiet thresholds by 20 and 40 dB. Word recognition was measured at several speech levels in each condition. Threshold was defined as the speech level (or signal-to-noise ratio) corresponding to the 50 rau point on the psychometric function. As expected, thresholds and slopes of psychometric functions were different for sentences with context compared to those for sentences without context. These differences were equivalent for young and aged subjects. Individual differences in word recognition among all subjects, young and aged, were accounted for by individual differences in signal-to-noise ratio. With signal-to-noise ratio held constant, word recognition for all subjects remained constant or decreased only slightly as speech and noise levels increased. These results suggest that, given equivalent speech audibility, older and younger listeners derive equivalent benefit from context.