In learning a language a child has to learn that certain words agree with certain endings (e.g., he does but not he do). Agreement morphology occupies a central role in language learning, and several language disorders are characterized by problems with agreement morphology (e.g. Specific Language Impairment and Autism). Thus, it is important to understand the mechanisms involved in learning and processing cases of agreement morphology as well as its normal time course of development. Although bilingualism is becoming the norm rather than the exception in the United States, agreement morphology has not been extensively investigated in bilingual populations. Bilingual children are often miscategorized as at risk for language disorders because little is known about bilingual language development compared to monolingual development. Differences in bilingual development are often interpreted as "atypical development". The primary objective of the proposed project is to document the normal time course of grammatical development in monolingual Spanish and bilingual (English/Spanish) infants, and to determine what types of agreement morphology dependencies infants are sensitive to. More specifically, this project examines when monolingual and bilingual infants are sensitive to non-adjacent morphosyntactic dependencies in the Noun Phrase (e.g., "the boys" but not "a boys") in Spanish and English using the Head-turn Preference Procedure technique. This research program is an extension of the PI's previous research on monolingual language development to a bilingual population (English/Spanish). Because this research proposal examines the normal time course of grammatical development in very young children, it contributes information on bilingual syntactic comprehension that could lead to the development of reliable measures of bilingual syntactic development and could also lead to more effective ways to differentiate late talkers from children with Specific Language Impairment (SLI). Thus, this research program is particularly relevant for the areas of Health Sciences and Communication Disorders. The data collected in this project will serve as the foundation for a broader research program that will investigate other types of morphosyntactic dependencies (e.g. he walks but not he walk) in monolingual and bilingual infants with the long-term goal of establishing the normal time course of grammatical development in bilingual and monolingual infants. PUBLIC HEALTH RELEVANCE: The results of this research will contribute information on bilingual language development that could lead to more effective ways to differentiate late talkers from children with Specific Language Impairment (SLI).