Does it take older adults longer than younger adults to perceptually segregate a speech target from a background masker?

Older adults often find it more difficult than younger adults to attend to a target talker when there are other people talking. One possible reason for this difficulty is that it may take them longer to perceptually segregate the target speech from competing speech. This study investigated age-related differences in the time it takes to segregate target speech from either a speech spectrum noise masker or a babble masker (many people talking simultaneously). Specifically, we employed five different delays (0.1 s-1.1 s) between masker onset and target speech onset. Four signal-to-masker ratios were employed at each delay to determine the 50% thresholds for word recognition accuracy when target words were masked by either speech spectrum noise or multi-talker babble. Thresholds for word recognition decreased exponentially as a function of the masker-word-onset delay, at the same rate for younger and older adults, when the masker was speech spectrum noise. When the masker was babble, thresholds for younger adults decreased exponentially with delay at the same rate as they did when the masker was speech spectrum noise. The word recognition thresholds for older adults, however, did not appear to change over the range of delays explored in this study. In addition, the average difference between word recognition thresholds for younger and older adults (younger adult thresholds < older adult thresholds) was significantly larger when the masker was babble than when it was noise. These results indicate that older adults are as fast as younger adults at separating speech from a steady-state noise masker, but are not as capable as younger adults of taking advantage of the delayed onset of the speech target when the masker is babble. The potential contributions of age-related sensory and cognitive declines to these stream segregation effects are discussed. Finally, we conclude that age-related differences in the timeline for stream segregation contribute to the difficulties older adults experience in listening to speech in a background of babble.