Word Identification With Temporally Interleaved Competing Sounds by Younger and Older Adult Listeners.

OBJECTIVES: The purpose of this experiment was to contribute to our understanding of the nature of age-related changes in competing speech perception using a temporally interleaved task.
DESIGN: Younger and older adults (n = 16/group) participated in this study. The target was a five-word sentence. The masker was one of the following: another five-word sentence; five brief samples of modulated noise; or five brief samples of environmental sounds. The stimuli were presented in a temporally interleaved manner, where the target and masker alternated in time, always beginning with the target. Word order was manipulated in the target (and in the masker during trials with interleaved words) to compare performance when the five words in each stream did versus did not create a syntactically correct sentence. Talker voice consistency also was examined by contrasting performance when each word in the target was spoken by the same talker or by different talkers; a similar manipulation was used for the masker when it consisted of words. Participants were instructed to repeat back the target words and ignore the intervening words or sounds. Participants also completed a subset of tests from the NIH Cognitive Toolbox.
RESULTS: Performance on this interleaved task was significantly associated with listener age and with a metric of cognitive flexibility, but it was not related to the degree of high-frequency hearing loss. Younger adults' performance on this task was better than that of older adults, especially for words located toward the end of the sentence. Both groups of participants were able to take advantage of correct word order in the target, and both were negatively affected, to a modest extent, when the masker words were in correct syntactic order. The two groups did not differ in how phonetic similarity between target and masker words influenced performance, and interleaved environmental sounds or noise had only a minimal effect for all listeners. The most robust difference between listener groups was found for the use of voice consistency: older adults, as compared with younger adults, were less able to take advantage of a consistent target talker within a trial.
CONCLUSIONS: Younger adults outperformed older adults when masker words were interleaved with target words. Results suggest that this difference was unlikely to be related to energetic masking and/or peripheral hearing loss. Rather, age-related changes in cognitive flexibility and problems encoding voice information appeared to underlie group differences. These results support the contention that, in real-life competing speech situations that produce both energetic and informational masking, older adults' problems are due to both peripheral and nonperipheral changes.