Funding Source: NIDCD R01DC018279 – The majority of deaf children are at risk for impoverished and/or delayed exposure to language, spoken or signed, because they have limited access to speech sounds and have parents who are not native users of a sign language. Work on the critical period has shown that delayed exposure to a first language has lasting effects on many aspects of development. The goal of this project is to understand how exposure to primarily non-native language input during the critical period affects vocabulary acquisition. We focus on early vocabulary development in deaf children learning American Sign Language (ASL) and we investigate the strategies used by deaf children with native exposure to ASL and by deaf children who are learning ASL from their non-native, signing hearing parents. Here we ask how variations in quality and quantity of language input during the critical period shapes early language learning strategies. This project will provide a detailed view of early ASL vocabulary acquisition, and can help practitioners and researchers develop interventions to mitigate the risks and effects of impoverished language exposure during the critical period.