Effects of talker continuity and speech rate on auditory working memory.

Speech processing is slower and less accurate when listeners encounter speech from multiple talkers compared to one continuous talker. However, interference from multiple talkers has been investigated only using immediate speech recognition or long-term memory recognition tasks. These tasks reveal opposite effects of speech processing time on speech recognition - while fast processing of multi-talker speech impedes immediate recognition, it also results in more abstract and less talker-specific long-term memories for speech. Here, we investigated whether and how processing multi-talker speech disrupts working memory maintenance, an intermediate stage between perceptual recognition and long-term memory. In a digit sequence recall task, listeners encoded seven-digit sequences and recalled them after a 5-s delay. Sequences were spoken by either a single talker or multiple talkers at one of three presentation rates (0-, 200-, and 500-ms inter-digit intervals). Listeners' recall was slower and less accurate for sequences spoken by multiple talkers than a single talker. Especially for the fastest presentation rate, listeners were less efficient when recalling sequences spoken by multiple talkers. Our results reveal that talker-specificity effects for speech working memory are most prominent when listeners must rapidly encode speech. These results suggest that, like immediate speech recognition, working memory for speech is susceptible to interference from variability across talkers. While many studies ascribe effects of talker variability to the need to calibrate perception to talker-specific acoustics, these results are also consistent with the idea that a sudden change of talkers disrupts attentional focus, interfering with efficient working-memory processing.