The Sensitive Period for Speech Perception

在儿童和青少年时期，言语感知的可塑性发生变化，导致敏感的 第二语言习得阶段。然而，发展的时间进程和 这种变化的潜在认知和神经机制尚未得到充分理解。的 拟议的研究调查的假设，“巩固”的母语知觉是 这种年龄限制学习的一种机制。我们的具体目标是： 1)考察到达年龄对第二语言知觉专业知识的影响 演讲分类我们将研究正在学习英语的以日语为母语的成人 使用一套实验方法，包括：a）视觉世界任务， 心理物理测量和敏感的眼动追踪测量，B）“无任务”去适应 fMRI研究语音分类功能解剖学的范例和c）一个disabituation 用于EEG的范例，其匹配行为结果的时间过程，以及d）生产任务， 评估感知与生产发展之间的关系。 2)应用语音分类法考察儿童和青少年语音分类的发展 以上开发的方法适用于6-18岁的母语为英语的人。 3)探讨母语专业知识的出现与 第二语言语音类别的可塑性下降，从目标1和2的数据。 假设在敏感期可塑性的下降与增加 知觉专业知识以相同的范式和刺激为母语的成年人收集的数据 日本，母语为英语的儿童，青少年和成人将是一个强大的基础， 测试这个假设。 本研究将为言语的典型发展时间进程提供一些启示 从童年到成年的感知，它提供了一个模型系统，在其中研究 学习基本失败背后的认知和神经机制。标准数据， 范式和机械的见解可能最终有利于非典型发展的研究， 临床人群（即诵读困难、语言障碍和学习障碍）。

Plasticity for speech perception changes during childhood and adolescence, resulting in a sensitive period for second-language acquisition. However, the developmental time-course and the underlying cognitive and neural mechanisms of this change are not adequately understood. The proposed research investigates the hypothesis that "entrenchment" of native language perception is one mechanism of such age-limited learning. Our specific aims are : 1) Examine the influence of age of arrival on perceptual expertise for second-language speech categories. We will study adult native speakers of Japanese who are learning English using a suite of experimental methods including: a) a visual world task that combines psychophysical measures and sensitive eye-tracking measures, b) a "task free" dishabituation paradigm for fMRI to study the functional anatomy of phonetic categorization and c) a dishabituation paradigm for EEG that matches the timecourse of the behavioral results and d) productions tasks to assess the relationship between perception and production development. 2) Examine the development of phonetic categorization in children and adolescents applying the methods developed above to native English speakers age 6-18. 3) Explore the relationship between the emergence of native-language expertise and the decline in plasticity for second-language speech categories in the data from Aims 1and 2.We hypothesize that the decline in plasticity during the sensitive period is associated with increasing perceptual expertise. Data collected with the same paradigms and stimuli for adult native speakers of Japanese, native English speaking children, adolescents and adults will be the basis for a strong test of this hypothesis. This investigation will provide insights into the typical developmental timecourse of speech perception from childhood to adulthood, which provides a model system in which to study the cognitive and neural mechanisms behind a basic failure of learning. The normative data, paradigms, and mechanistic insights may ultimately benefit studies of atypical development in clinical populations (i.e. dyslexia, language impairments, and learning disabilities).