The Sensitive Period for Speech Perception

描述(申请人提供)：儿童和青春期言语感知变化的可塑性，导致第二语言习得的敏感期。然而，这种变化的发育时间进程以及潜在的认知和神经机制还没有被充分了解。这项拟议的研究调查了一种假设，即母语感知的“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言语类别知觉专长的影响。我们将使用一套实验方法对以日语为母语的成年人进行研究，这些方法包括：a)结合心理物理测量和敏感眼球跟踪测量的视觉世界任务，b)用于fMRI研究语音分类的功能解剖的无任务去适应范式，c)用于脑电的去适应范式，其与行为结果的时间进程相匹配，d)产生任务以评估知觉和产生发展之间的关系。2)将上述研究方法应用于6-18岁的英语母语者，考察儿童和青少年的语音分类发展情况。3)在AIMS 1和AIMS 2的数据中，探讨母语专业知识的出现与第二语言言语类别可塑性下降之间的关系。我们假设敏感期的可塑性下降与感知专业知识的增加有关。对于以日语为母语的成年人、以英语为母语的儿童、青少年和成年人，以相同的范式和刺激收集的数据将成为对这一假设进行强有力检验的基础。这项研究将提供从儿童到成年的典型言语知觉发展时间过程的洞察，为研究基本学习失败背后的认知和神经机制提供了一个模型系统。规范的数据、范例和机械性的洞察最终可能有助于临床人群中非典型发展(即阅读困难、语言障碍和学习障碍)的研究。

DESCRIPTION (provided by applicant): 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 1 and 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).