Speech Perception under Cognitive Load

大多数关于人类语言感知的理论都来自于在安静的环境和集中注意力的条件下执行的任务。然而，在过去的几年里，人们对在更现实的条件下（例如，嘈杂的背景，重音语音）建模语音识别的兴趣激增。然而，在这些现实条件中，由认知负荷引起的条件很少受到关注。在这里，我们将认知负荷（CL）定义为不是由语音信号失真引起的任何听力挑战，而是由于并发的注意或助记需求而引起的处理资源的消耗。例如，监控驾驶舱仪表对飞行员遵循地面控制人员口头指令的能力有什么影响？CL对语音感知的破坏作用早在声音编码的初始阶段就已被注意到。在某些情况下，CL甚至会导致一种称为无意耳聋的暂时性听力障碍。尽管这些结果对理论和临床实践具有明显的意义，但对于CL干扰言语感知的低级机制知之甚少。本提案的目的是解决这一问题在三个相互关联的研究流绘制心理测量和识别范式。第一个问题是CL是否对语音的所有声学维度都有相同的影响。这个问题很重要，因为并非所有的声学维度对通信都同样重要。例如，成功的单词识别对音高扭曲比持续时间扭曲更有弹性。CL对某些维度的影响比其他维度更大，这一观点的动机是CL（例如，并发视觉任务）会导致听者在语音信号和CL任务之间快速地来回转移注意力，从而导致对语音信号持续时间的低估。如果这个假设是正确的，CL应该主要导致听觉时间判断的扭曲，而不影响其他核心维度（响度、音调和频谱结构）。这将与CL导致所有声学维度的听觉精度普遍降低的说法形成对比。第二个流研究的是CL刺激的形式是否会影响CL干扰的严重程度。例如，语音感知是受到需要默念单词（语音格式）的并发任务的影响更大，还是受到需要处理视觉刺激（视觉格式）的任务的影响更大？这些实验将解决在语音感知过程中使用的处理资源的模态和情态观点之间的争论。第三个流旨在区分CL干扰背后的两种潜在机制：编码和维护。编码是将感官输入转化为心理表征的过程。维护是在内存中保存这些表示的过程。语言刺激的编码将被操纵，使其发生在言语刺激期间或之前，因此编码与维持作为潜在干扰的机制。编码假说预测，只有同时对言语和言语刺激进行编码才能导致言语效应。为了探索上述现象在语音领域之外的普遍性，我们将测试CL对语音和非语音的影响。这种比较将把我们的发现置于长期以来关于声音感知的专门语言模式存在的争论中。最后，由于“认知听力”的概念不仅在言语研究中而且在听力实践中都成为中心，我们将与临床听力学家合作，讨论将认知成分纳入标准纯音听力测量（PTA）的方法，并为潜在的ii期临床试验提供建议。

Most theories of human speech perception are derived from tasks performed in a quiet environment and under conditions of undivided attention. However, in the past few years, there has been a surge of interest in modelling speech recognition in more realistic conditions (e.g., noisy background, accented speech). However, among these realistic conditions, those resulting from a cognitive load have received little attention. Here, we define cognitive load (CL) as any listening challenges arising not from a distortion of the speech signal but from the recruitment of processing resources due to concurrent attentional or mnemonic demands. For example, what are the consequences of monitoring cockpit instruments on a pilot's ability to follow spoken instructions from ground control? The disruptive effect of CL on speech perception is noticed as early as in the initial stages of acoustic encoding. Under some circumstances, CL can even lead to a form of transient hearing impairment called inattentional deafness. Despite the obvious implications that these results have for theory and clinical practice, little is known about the low-level mechanisms by which CL interferes with speech perception. The aim of this proposal is to address this issue in three interconnected research streams drawing upon psychometric and identification paradigms.The first stream asks whether CL affects all acoustic dimensions of speech equally. This question is important because not all acoustic dimensions are equally crucial for communication. For example, successful word recognition is more resilient to pitch distortions than duration distortions. The idea that CL affects some dimensions more than others is motivated by the claim that CL (e.g., a concurrent visual task) causes listeners to rapidly shift attention back and forth between the speech signal and the CL task, leading to an underestimation of the duration of the speech signal. If this hypothesis is correct, CL should lead primarily to a distortion of auditory temporal judgements and leave other core dimensions (loudness, pitch, and spectral structure) unaffected. This will be contrasted with the claim that CL leads to a general reduction in auditory precision across all acoustic dimensions.The second stream investigates whether the format of the CL stimuli affects the severity of the CL interference. For example, is speech perception more affected by a concurrent task that requires rehearsing words silently (phonological format) or by a task that requires processing visual stimuli (visual format)? These experiments will address the debate between modal and amodal views of the processing resources used during speech perception. The third stream aims to distinguish two potential mechanisms behind CL interference: Encoding and maintenance. Encoding is the process of converting a sensory input into mental representations. Maintenance is the process of preserving these representations in memory. Encoding of the CL stimuli will be manipulated such that it takes place either during or before the speech stimuli, hence pitting encoding against maintenance as the mechanism underlying interference. An encoding hypothesis predicts that only simultaneous encoding of speech and CL stimuli should lead to CL effects. In order to explore the generalisability of the above phenomena beyond the speech domain, the effect of CL will be tested on both speech and non-speech sounds. This comparison will situate our findings within the long-standing debate on the existence of a specialised speech mode for sound perception.Finally, because the notion of "cognitive listening" is becoming central not only in speech research but also in hearing practice, we will engage with clinical audiologists and discuss ways of including a cognitive component into standard pure-tone audiometric (PTA) and advise on potential phase-II clinical trials.