Social and Statistical Mechanisms of Prelinguistic Vocal Development

婴儿是如何学会发出自己语言的声音的？婴儿的发音能力在出生后的第一年发生了巨大的变化。从最早的、不成熟的发声开始，婴儿进步很快，通常在12个月大的时候会说第一个单词。在这个过程中，他们开始产生类似语音的音节，并根据他们的语言环境的语音模式来组织音节序列。虽然第一年的发声成就被很好地描述，但对推动发声发展的变化机制知之甚少。然而，许多关于鸟类鸣叫学习的研究以及研究者的初步研究表明，社会环境是丰富的结构和反馈的来源，可以指导早期的声乐学习和发展。语言前的婴儿能使用社会反馈来创造新的、更先进的发声吗？研究者假设有两个过程使社会对声乐学习产生影响。在最初的6个月里，婴儿知道他们的咿呀学语确实会影响成年人的行为。从这种早期学习中，婴儿开始适应社会对他们发声的反应。在接下来的6个月里，婴儿利用照顾者对他们咿呀学语的偶然反应来指导他们的发音，以适应语言的语音模式。获取控制多个示例之间关系的潜在模式的知识是一个称为统计学习的过程。为了研究这些声音学习的过程，看护人对婴儿声音的反应的形式和时间将被操纵。首先，研究对象为2- 5个月大的婴儿，研究其咿呀学语和照顾者反应之间的学习关联过程。婴儿的信息处理能力和照顾者对咿呀学语的自然反应将被用来预测学习的个体差异。其次，对9个月大婴儿的语音统计特性和偶然性进行分析，以评估其对语音学习的影响。统计学习在语音感知和产生中的作用将直接进行比较。最后，确定两种学习机制（2 - 5个月的联想学习和9个月的统计学习）之间的关系。这些研究的发现将允许研究者构建一个新的理论框架来研究声音的发展，整合来自社会学习和语言感知的数据。这些实验将受益于数字技术的新应用，它允许在自然互动过程中实时操纵护理人员的行为（通过无线耳机给出的指令）。同时，对婴儿发声的变化进行记录和分析。提出的研究对教育父母为婴儿提供最佳学习环境具有广泛和基本的意义。了解社会引导学习在言语和语言中的作用，可以帮助照顾者以促进发展的方式对婴儿的行为更加敏感。研究社会对语音发展的影响将有助于言语语言病理学的研究以及成功和障碍交际发展背后的过程。这项研究将为理解早期社会学习在沟通和语言缺陷（如自闭症和唐氏综合症）中的作用提供一个框架。通过阐明婴儿向照顾者学习的机制，这些发现将有助于为发育障碍婴儿设计行为干预措施。

How do infants learn to produce the sounds of their language? The vocal abilities of infants change dramatically over the first year of life. Beginning with the earliest, immature vocalizations, infants make rapid progress, typically producing their first words by 12 months of age. Along the way, they begin to produce speech-like syllables and to structure sequences of syllables in accordance with the phonological patterns of their language environment. While the vocal achievements of the first year are well-described, not nearly as much is known about the mechanisms of change that drive vocal development. However, many studies of song learning in birds, as well as the investigators' preliminary studies, indicate that the social environment is a source of rich structure and feedback that can guide early vocal learning and development. Can prelinguistic infants use social feedback to create new, more developmentally advanced vocalizations? The investigators hypothesize that two processes enable social influences on vocal learning. During the first 6 months, infants learn that their babbling reliably affects adults' behavior. From this early learning, infants become attuned to social responses to their vocalizing. Over the next 6 months, infants use the contingent reactions of caregivers to their babbling to guide their vocalizations towards the phonological patterns of their language. Acquiring knowledge of underlying patterns that govern the relations among multiple examples is a process known as statistical learning. To investigate these processes of vocal learning, the form and timing of caregivers' reactions to their infants' sounds will be manipulated. First, the process of learning associations between babbling and caregivers' reactions will be investigated in 2- to 5-month-old infants. Infants' information-processing capacities and caregivers' natural responsiveness to babbling will be used to predict individual differences in learning. Second, the statistical properties and contingency of speech to 9-month-old infants will be manipulated to assess their effects on vocal learning. The role of statistical learning in speech perception and production will be directly compared. Finally, the relation between the two learning mechanisms (associative learning at 2 to 5 months and statistical learning at 9 months) will be determined. Findings from these studies will allow the investigators to construct a new theoretical framework for vocal development, integrating data from social learning and speech perception. The experiments will benefit from new applications of digital technologies that allow caregiver behavior to be manipulated in real-time (via instructions given over wireless headphones) during naturalistic interaction. At the same time, changes in infants' vocalizations will be recorded and analyzed. The proposed research has broad and fundamental implications for educating parents in providing optimal learning environments for their infants. An understanding of the role of socially guided learning in speech and language could be used to help caregivers to be more sensitive to infants' behavior in ways that would facilitate development. Investigating social influences on phonological development will contribute to the study of speech-language pathology and of processes underlying both successful and disordered communicative development. This research will provide a framework for understanding the role of early social learning in communication and language deficits such as those seen in autism and Down's syndrome. By elucidating mechanisms by which infants learn from caregivers, these findings will be useful in designing behavioral interventions for infants with developmental disorders.