The Sensitive Period for Speech Perception

描述（由申请人提供）：在儿童和青少年时期，言语感知的可塑性发生变化，导致第二语言习得的敏感期。然而，这种变化的发展时间过程和潜在的认知和神经机制还没有得到充分的理解。本研究探讨了母语知觉的“巩固”是这种年龄限制学习的一种机制这一假设。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业知识的影响。我们将使用一套实验方法来研究正在学习英语的日语母语成年人，包括：a）结合心理物理测量和敏感的眼动跟踪测量的视觉世界任务，B）一个“任务自由”的disabituation范式的功能磁共振成像研究的功能解剖学的语音分类和c）disabituation范式的脑电图匹配的时间进程的行为结果和d）生产任务，以评估感知和生产发展之间的关系。2)将上述方法应用于6-18岁以英语为母语的儿童和青少年，检查语音分类的发展。3)在目标1和目标2的数据中，探索母语专业知识的出现与第二语言语音类别可塑性下降之间的关系。我们假设，在敏感期的可塑性下降与增加知觉的专业知识。收集的数据与相同的范例和刺激的成人母语为日语，母语为英语的儿童，青少年和成人将是一个强有力的测试这一假设的基础。这项调查将提供从儿童到成年的言语知觉的典型发展时间过程的见解，它提供了一个模型系统，在其中研究的认知和神经机制背后的基本学习失败。规范性数据，范例和机制的见解可能最终有利于临床人群（即阅读障碍，语言障碍和学习障碍）的非典型发展的研究。

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).