Katharine M. Graf Estes, Ph.D. - US grants

This award is funded under the American Recovery and Reinvestment Act of 2009 (Public Law 111-5).

During the first years of life, infants learn a remarkable amount about the structure of their native language. The precocious nature of early language acquisition has motivated the exploration of the forces driving these amazing feats of learning. One promising mechanism is statistical learning, the process of detecting structure in the environment by tracking patterns present in the input. Recent investigations have revealed that infants possess powerful statistical learning capabilities that allow them to track patterns in the sounds and words of linguistic input. However, the manner in which infants use statistical learning to solve real challenges in language acquisition is not yet clear. This project investigates how infants use statistical learning to perform two fundamental tasks in early language development: detecting words in fluent speech and linking the sounds of words with meanings. The experiments incorporate several infant testing methodologies, including measures of word segmentation, object label learning tasks, and online measures of word learning and recognition. The experiments also integrate the use of carefully controlled artificial languages and natural native language statistical regularities to probe the robustness of statistical learning to inconsistency and acoustic variation, two hallmarks of natural speech that present significant challenges to the detection of statistical regularities.

The findings from this project will shed light on how infants track the statistical regularities of their native language and how those regularities shape early language development. More broadly, this investigation will contribute to the understanding of the bases of language acquisition. Furthermore, revealing the nature of fundamental language acquisition mechanisms has significant implications for understanding the developmental course of language impairments. Characterizing the processes that drive early language acquisition in typically developing infants will inform the search for the bases of language deficits. In addition, this project integrates educational opportunities for students with the research program, specifically focusing on the recruitment of research assistants from promising high school students and undergraduates who belong to groups underrepresented in higher education and in research. Students will participate throughout the research process, from recruiting and testing participants to disseminating the results to the public and scientific communities. Involvement in a research group provides students with unique opportunities to develop strong academic ties and academic skills, to participate in mentoring relationships, and to develop new ways of thinking.

DESCRIPTION (provided by applicant): The research proposed in this application will investigate the connection between statistical learning and vocabulary development. Statistical learning refers to the process of detecting structure in the environment by tracking patterns present in the input. Recent experiments have revealed that infants possess remarkable statistical learning capabilities. Statistical learning may play a significant role in the precocious development of native language sound structure that occurs during the first year of life. During the second year, vocabulary development accelerates. The proposed experiments are motivated by the hypothesis that statistical learning about sounds lays a foundation for word learning. Thus, infants'ability to track statistical regularities may affect the ability to build a vocabulary. This research will examine the relation between individual differences in infants'vocabulary development and individual differences in statistical learning. The experiments will use measures of listening time and looking time to test infants'detection of novel statistical regularities, and to test their knowledge of native-language statistical regularities. Infants will participate speech, non-speech auditory, and visual statistical learning tasks in order to evaluate the coherence of statistical learning across domains. A label-learning task will also tap infants'ability to use native language statistical regularities to acquire new lexical items. In each experiment, infants'performance on experimental tasks will be integrated with measures of their real-world vocabulary development. This findings of this research promise to inform understanding of the underlying mechanism that contribute to individual differences in language acquisition. PUBLIC HEALTH RELEVANCE: The proposed research investigates the relation between individual differences in vocabulary development and how they relate to individual differences in statistical learning, a fundamental language acquisition mechanism. The findings from this project will influence understanding of typical language development and have potential to affect understanding of language delays and disorders. By focusing research on a mechanism that is thought to play a significant role in language acquisition, we may help to reveal potential deficits and means to identify infants who are at risk of developing lasting language problems.

? DESCRIPTION (provided by applicant): A majority of children worldwide learn more than one language (Grosjean, 2010), yet theories of language acquisition treat monolingualism as the standard learning model. Bilingualism is highly common, but the mechanisms that drive bilingual learning are not yet well understood. In order to develop rich theories of language acquisition, it is necessary to include a full consideration of the demands of bilingual learning environments and how learners cope with these demands. The proposed research project seeks to fill this theoretical gap by investigating bilingual statistical learning at the very early stages of languag acquisition. Statistical learning entails discovering structure by tracking patterns that are preset in the input. Statistical learning is a popular framework that has received a great deal of attention for its potential to explain how infants and children acquire many dimensions of linguistic structure. Infants are remarkably skilled at tracking regularities. However, the literatre has not yet addressed how bilingualism affects the ability to extract statistical regularities in linguistic input. The demands are substantially greater for bilinguals than for monolinguals. They must track two separate sets of regularities for every aspect of linguistic structure, from sounds to words to grammar. This research will examine two processes that are fundamental for early language acquisition, the ability to detect words in fluent speech and the ability to associate word forms with meanings. The experiments will address how dual language input affects infants' ability to perform these tasks. In addition, both monolingual and bilingual infants will participate, providing a window on how bilingual experience affects infants' tracking of regularities in dual languages. The project will also explore what cognitive processes support bilingual infants' ability to learn effectively in two immensely complex linguistic systems, focusig on how cognitive control and vocabulary composition relate to statistical learning skills in the laboratory. In addressing a theoretical gap, the proposed research also has substantial significance for public health. This work will reveal mechanisms that infants use to learn and the conditions that support or hinder bilingual learning. These contributions have potential to affect the design and implementation of early bilingual education programs. In addition, this work will elucidate the mechanisms that typically developing infants use to acquire language, which has applied value for the study of language impairments. Understanding the underlying processes of typical development is crucial for understanding the development of populations who are not acquiring language on a typical course. It is important to know how learning typically proceeds in order to identify potential underlying deficits in learning impairments.