Early predictors of Late Talking (LT) in infancy

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Project Summary/Abstract Infant speech learning during the sensitive period for phonetic learning has been shown repeatedly to predict language abilities up to school age, with the potential to also mark atypical language development. One important factor influencing the outcome of the sensitive period and subsequent language development trajectory is the quality and quantity of language input in infancy. As infants develop, a substantial subgroup will start to show delay in language emergence, starting around 18 months of age, even after excluding primary factors such as hearing impairment, ASD and other neurological disorders. Many Late Talkers will have persistent speech and language delays (e.g., Developmental Language Disorder) into school age and beyond. Even those who eventually achieve language scores within the average range still score lower than typically developing children. Late- talkers might thus provide a first clue of DLD, making them an important group to study. Yet, little is known regarding their early predictors. In my current parent Katz ESI R01, we are focusing on investigating whether infants at High Risk of developing DLD (i.e., with first-degree family member who exhibit speech and language disorders) already demonstrate altered neural processing of speech at 6, 12 and 14 months of age, straddling the sensitive period, compared to their Low Risk typically developing counterpart. The parent grant thus offers an optimal infrastructure for this proposed supplement project to start examining research questions related to early predictors of late talkers by adding additional measurements at additional time points. Specifically, we plan to examine two potential early predictors, namely being at High-Risk of DLD and language input in infancy. To characterize infants’ language abilities in toddlerhood, we plan to recruit all infants (i.e., both Low- Risk and High-Risk groups) in the parent grant longitudinal study to further enroll in the MacArthur- Bates Communicative Development Index (CDI) parental reports at 18, 21, 24, 27, 30 months of age. To characterize language input in infancy (e.g., amount of IDS), we plan to recruit all infants at 9 months of age (i.e., in the middle of the sensitive period) for daylong audio recordings of their home environment, using the Language Environment Analysis (LENA) system. Together, these additional measures collected in the supplement project will not only address two important questions regarding the early predictors of Late Talking, but will also help create a valuable multimodal dataset to share with the scientific community at the end of the parent grant. Testing these hypotheses will likely open many opportunities for follow-up questions. For example, in conjunction with the neuroimaging data collected through the parent grant, we can test if combining language input, infant neural processing of speech and risk-level can better predict late language emergence than any single factor.