Speech perception is challenged by indexical variability. A litany of studies on talker normalization have demonstrated that hearing multiple talkers incurs processing costs (e.g., lower accuracy, increased response time) compared to hearing a single talker. However, when reframing these studies in terms of stimulus structure, it is evident that past tests of multiple-talker (i.e., low structure) and single-talker (i.e., high structure) conditions are not representative of the graded nature of indexical variation in the environment. Here we tested the hypothesis that processing costs incurred by multiple-talker conditions would abate given increased stimulus structure. We tested this hypothesis by manipulating the degree to which talkers’ voices differed acoustically (Experiment 1) and also the frequency with which talkers’ voices changed (Experiment 2) in multiple-talker conditions. Listeners performed a speeded classification task for words containing vowels that varied in acoustic-phonemic ambiguity. In Experiment 1, response times progressively decreased as acoustic variability among talkers’ voices decreased. In Experiment 2, blocking talkers within mixed-talker conditions led to more similar response times among single-talker and multiple-talker conditions. Neither result interacted with acoustic-phonemic ambiguity of the target vowels. Thus, the results showed that indexical structure mediated the processing costs incurred by hearing different talkers. This is consistent with the Efficient Coding Hypothesis, which proposes that sensory and perceptual processing are facilitated by stimulus structure. Defining the roles and limits of stimulus structure on speech perception is an important direction for future research.

中文翻译：

---

说话者规范化是由结构化索引信息介导的。

言语感知受到索引变异性的挑战。一系列有关说话人正常化的研究表明，与听到单个说话人相比，听到多个说话人会产生处理成本（例如，较低的准确性，增加的响应时间）。但是，当从刺激结构的角度重新研究这些研究时，很明显，过去对多说话者（即低结构）和单说话者（即高结构）条件的测试并不能代表指标变化的分级性质。环境。在这里，我们测试了这样一种假设：在刺激因素增加的情况下，多方对话条件引起的处理成本将减少。我们通过操纵说话者的声音在声学上的差异程度（实验1）以及在多说话者条件下说话者的声音变化的频率（实验2）来检验该假设。侦听器对包含元音在发音歧义上有所不同的单词执行了快速分类任务。在实验1中，响应时间随着讲话者语音中声音变异性的降低而逐渐降低。在实验2中，在混合通话者条件下阻止通话者会导致单通话者和多通话者条件之间的响应时间更加相似。这两个结果都与目标元音的语音歧义无关。因此，结果表明，索引结构介导了聆听不同讲话者所产生的处理成本。这与有效编码假说是一致的，该假说提出通过刺激结构促进感觉和知觉处理。定义刺激结构在言语感知中的作用和局限性是未来研究的重要方向。