Attention, Task Demands, and Multitalker Processing Costs in Speech Perception

Determining how human listeners achieve phonetic constancy despite a variable mapping between the acoustics of speech and phonemic categories is the longest standing challenge in speech perception. Aclue comes from studies where the talker changes randomly between stimuli, which slows processingcompared with a single-talker baseline. These multitalker processing costs have been observed most oftenin speeded monitoring paradigms, where participants respond whenever a specific item occurs.Notably, the conventional paradigm imposes attentional demands via two forms of varied mapping inmixed-talker conditions. First, target recycling (i.e., allowing items to serve as targets on some trials butas distractors on others) potentially prevents the development of task automaticity. Second, in mixed trials,participants must respond to two unique stimuli (i.e., one target produced by each talker), whereasin blocked conditions, they need respond to only one token (i.e., multiple target tokens). We seek tounderstand how attentional demands influence talker normalization, as measured by multitalker processingcosts. Across four experiments, multitalker processing costs persisted when target recycling was notallowed but diminished when only one stimulus served as the target on mixed trials.