The Sensitive Period for Speech Perception

儿童和青春期言语知觉的可塑性变化，导致敏感 第二语言习得期。然而，发展的时间进程和 这种变化的潜在认知和神经机制还没有被充分了解。这个 拟议的研究调查了母语感知的“根深蒂固”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特长的影响 语音类别。我们将研究正在学习英语的以日语为母语的成年人 使用一套实验方法，包括：a)视觉世界任务 心理物理措施和敏感的眼球跟踪措施，b)“无任务”的去适应 FMRI研究语音分类和c)去习惯的功能解剖学范式 与行为结果和d)产生任务的时间进程相匹配的EEG范例 评估感知和生产发展之间的关系。 2)考察儿童和青少年语音分类的发展状况 上述方法适用于6-18岁以英语为母语的人。 3)探索母语专业知识的出现与 目标1和目标2的数据中第二语言言语类别的可塑性下降 假设敏感期的可塑性下降与 感性的专业知识。以同样的范式和刺激对成年母语人士收集的数据 对日语、以英语为母语的儿童、青少年和成年人来说，将是强大的基础 对这一假设的检验。 这项研究将对言语的典型发展时间进程提供深入的见解 从童年到成年的感知，这提供了一个模型系统来研究 学习基本失败背后的认知和神经机制。规范数据， 范式和机械论的洞察力最终可能有助于对非典型发育的研究 临床人群(即阅读困难、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).