The neural and cognitive mechanisms of infants' word representations: The role of variability

加拿大人生活在一个越来越多样化和多口音的环境中，这无疑会影响婴儿的语言习得。这项工作将确定儿童的文字处理如何受到这种多样性的影响，并将开始描述和理解婴儿新兴的单词表征的本质。在这些实验中，我将把重点放在11到14个月大的婴儿身上，并使用眼球追踪和功能性近红外光谱（fNIRS）来检测大脑中血红蛋白的变化。在本提案的三个目标中，我将讨论说话者的语言特性（如口音）和社会特性（如说话者种族）的可变性如何支持语言习得，并捕捉早期单词表征的细微差别。目的1：为了理解婴儿的词汇习得，描述他们不断变化的大脑如何支持单词处理是至关重要的。在Aim 1中，我将比较婴儿使用眼动追踪和fNIRS对熟悉单词和新单词的熟悉发音的处理。通过这个目标，我将深入了解婴儿基本单词表征的潜在结构，这将作为其他目标的基线。目标2：通常情况下，年轻的单语语言学习者在不熟悉的口音下很难识别单词（例如，Van Heugten & Johnson, 2017）。他们尤其难以应对与母语口音进一步偏离的口音（例如，White & Morgan, 2008），以及包含导致语音变化的元音移位（即，听起来完全像一个不同的元音）（例如，Newman等人，2018）。在目标2中，我将评估婴儿如何通过操纵变化的幅度和他们对特定变体的暴露来处理已知单词的变体发音。从这些实验中，我将能够确定婴儿时期单词表征的灵活性，并将确定支持口音调节的机制。目标3：我之前的工作表明，种族对婴儿的文字处理有深远的影响（例如，Weatherhead & White, 2018； Weatherhead等人，邀请重新提交）。在Aim 3中，我将确定非语言信息如何通过使用眼动追踪和fNIRS操纵说话者来影响对已知单词的熟悉和变体发音的识别。在这些最后的实验中，婴儿将听到与前几个目标相同的听觉刺激，但伴随着一张脸。这些实验的结果是文献中缺失的一个重要环节，因为它们将直接说明婴儿时期的单词表征是否包含非语言上下文信息。这项工作采用了一种独特的方法来研究语言习得，通过观察不同的说话者如何在单词表征的发展中发挥不可或缺的作用。在加拿大这样一个多元文化的国家，这样的工作对于人类发展的生态模式是必要的。

Canadians live in an increasingly diverse and multi-accented context, which undoubtedly impacts infants' language acquisition. The proposed work will determine how children's word processing is influenced by this diversity, and will begin to characterize and understand the nature of infants' emerging word representations. In these experiments, I will focus on 11-to-14-month-olds and use eye-tracking and functional Near-Infrared Spectroscopy (fNIRS), which detects haemoglobin changes in the brain. In the three aims of this proposal, I will address how variability in speakers' linguistic properties (like accent) and social properties (like speaker race) supports language acquisition, and capture the nuances of early word representations. Aim 1: To understand infants' vocabulary acquisition, it is critical to delineate how word processing is supported by their changing brains. In Aim 1, I will compare infants processing of familiar pronunciations of known words and novel words using eye-tracking and fNIRS. Through this aim, I will gain insight into the underlying structure of infants' basic word representations, which will serve as a baseline for the remaining aims. Aim 2: Typically, young monolingual language learners struggle to recognize words when they are produced with an unfamiliar accent (e.g., Van Heugten & Johnson, 2017). They particularly struggle with accents that deviate further from their native accent (e.g., White & Morgan, 2008), and contain vowel shifts that induce phonological change (i.e., sound like a different vowel entirely) (e.g., Newman et al., 2018). In Aim 2, I will assess how infants process variant pronunciations of known words by manipulating the magnitude of variation and their exposure to the specific variants. From these experiments, I will be able to determine how flexible word representations are in infancy, and will identify the mechanisms that support accent accommodation. Aim 3: My previous work has shown that race has a profound influence on infants' word processing (e.g., Weatherhead & White, 2018; Weatherhead et al., Invited Resubmit). In Aim 3, I will determine how non-linguistic information impacts the recognition of familiar and variant pronunciations of known words by manipulating speaker using eye-tracking and fNIRS. In these final experiments, infants will hear the same auditory stimuli as in in the previous aims, but with an accompanying face. The results of these experiments are an essential missing link in the literature, as they will speak directly to whether word representations in infancy incorporate non-linguistic contextual information. This work takes a unique approach to studying language acquisition by looking at how diverse speakers play an integral role in the development of word representations. In a country as multicultural as Canada, work such as this is necessary for ecological models of human development.