Auditory and cognitive factors in speech perception and category learning

描述(申请人提供)：来自理想观察者理论的概念将被用来研究听觉类别学习和言语感知。理想的观察者为评估人类在知觉任务上的表现提供了一个基准，并可以作为开发实际表现模型的适当起点。在第一组实验中，听者将学会对新奇的非言语刺激进行分类。类别的先验概率和类别重叠程度将不同，以评估听者对刺激的分布特性的敏感性。第二组实验将测试言语和非言语知觉中的选择性适应和对比效应是否可以模拟为听者先验概率和刺激似然分布的变化。第三组实验将扩展我们实验室最近的试点工作，旨在为自然产生的语音开发理想的分类器。这项试点工作的结果表明，听者采用了一种针对其语言中音素的自然分布特性来优化分类性能的策略。这一假设将在这些实验中得到全面检验。第四组实验将考察观察者在进行音素类别判断时如何权衡和整合多种证据来源。其目的是了解当不同的刺激属性以可预测或不可预测的方式退化时，听者在这类任务中接近最佳信息权重的程度。在第五组实验中，自然音素分布将被用来估计一组母语(L1)音素对比和一组第二语言(L2)竞争对比之间的最佳轨迹。第二语言学习者在不同熟练程度阶段的感知数据将与估计的最佳轨迹进行比较。在拟议的研究中开发和测试的技术可以作为重要的工具来研究不同程度听力损失的听者的言语感知，包括那些植入人工耳蜗者。特别是，对其听觉输入被限制为模仿特定听力受损个体的理想分类器的推导可能使研究人员能够区分由于感觉因素造成的表现限制和可归因于非最佳分类策略的限制。

DESCRIPTION (provided by applicant): Concepts from ideal observer theory will be used to study auditory category learning and speech perception. Ideal observers provide a benchmark for assessing human performance on perceptual tasks and may serve as an appropriate starting point for developing models of actual performance. In the first set of experiments, listeners will learn to categorize novel non-speech stimuli. Prior probabilities of the categories and degree of category overlap will be varied to assess listeners' sensitivity to the distributional properties of the stimuli. The second set of experiments will test whether selective adaptation and contrast effects in speech and non- speech perception can be modeled as changes in the listeners' prior probability and stimulus likelihood distributions. The third set of experiments will extend recent pilot work in our laboratory aimed at developing ideal classifiers for naturally produced speech sounds. The results of this pilot work suggest that listeners adopt a strategy of optimizing categorization performance with respect to the natural distributional properties of phonemes in their language. This hypothesis will be comprehensively tested in these experiments. The fourth set of experiments will examine how observers weight and integrate multiple sources of evidence in making phoneme category judgments. The aim is to learn how closely listeners approximate optimal informational weightings in such tasks when different stimulus properties are degraded in either predictable or unpredictable ways. In the fifth set of experiments, natural phoneme distributions will be used to estimate optimal trajectories between a set of native language (L1) phoneme contrasts and a competing set of contrasts in a second language (L2). Perception data of L2 learners at varying stages of proficiency will be compared to the estimated optimal trajectories. The techniques developed and tested in the proposed studies can serve as important tools for the study of speech perception in listeners with varying degrees of hearing loss, including those with cochlear implants. In particular, the derivation of ideal classifiers whose auditory input is restricted to mimic that of particular hearing-impaired individuals may allow investigators to distinguish between limits on performance due to sensory factors and those attributable to non-optimal categorization strategies.