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Can we prepare to attend to one of two simultaneous voices?

We can selectively attend to one of two simultaneous voices sharing a source location. Can we endogenously select the voice before speech is heard? Participants heard two digit names, spoken simultaneously by a male voice and a female voice, following a visual cue indicating which voice's digit to classify as odd or even. There was a substantial cost in reaction time and errors when the target voice switched from one trial to the next. In Experiment 1, with a highly familiar pair of voices, the switch cost reduced by nearly half as the cue-stimulus interval increased from 50 to 800 ms, indicating (contrary to previous reports) effective endogenous preparation for a change of voice. No further reduction in switch cost occurred with a longer preparation interval-this "residual" switch cost may be attributable to attentional "inertia." In Experiment 2, with previously unfamiliar voices, the pattern of switch costs was very similar, though repeated attention to the same target voice over a run of trials improved performance more. Delaying the onset of one voice by 366 ms improved performance, but the pattern of preparatory tuning effects was similar. Thus, endogenous preparation for a voice is possible, but it is limited in efficacy, as for some other attentional domains. (PsycINFO Database Record (c) 2019 APA, all rights reserved).