The mapping between speech acoustics and phonemic representations is highly variable across talkers, and listeners are slower to recognize words when listening to multiple talkers compared with a single talker. Listeners' speech processing efficiency in mixed-talker settings improves when given time to reorient their attention to each new talker. However, it remains unknown how much time is needed to fully reorient attention to a new talker in mixed-talker settings so that speech processing becomes as efficient as when listening to a single talker. In this study, we examined how speech processing efficiency improves in mixed-talker settings as a function of the duration of continuous speech from a talker. In single-talker and mixed-talker conditions, listeners identified target words either in isolation or preceded by a carrier vowel of parametrically varying durations from 300 to 1,500 ms. Listeners' word identification was significantly slower in every mixed-talker condition compared with the corresponding single-talker condition. The costs associated with processing mixed-talker speech declined significantly as the duration of the speech carrier increased from 0 to 600 ms. However, increasing the carrier duration beyond 600 ms did not achieve further reduction in talker variability-related processing costs. These results suggest that two parallel mechanisms support processing talker variability: A stimulus-driven mechanism that operates on short timescales to reorient attention to new auditory sources, and a top-down mechanism that operates over longer timescales to allocate the cognitive resources needed to accommodate uncertainty in acoustic-phonemic correspondences during contexts where speech may come from multiple talkers.
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http://dx.doi.org/10.3758/s13423-021-02019-3 | DOI Listing |
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