Effects of late first language acquisition on phonological processing in American Sign Language

Project Summary Only around 5% of deaf children are born to deaf parents and subsequently get exposure to an accessible sign language as their first language from birth (Mitchell & Karchmer, 2004). The other 95% of deaf children are born into hearing families and are at high risk of late first language acquisition that occurs after the critical period for language (Lenneberg, 1967). As adults, this late first language acquisition results in dramatic and lifelong effects on everything from education to job opportunities to mental health (Hall, 2017). Research looking at the effects of late first language acquisition on language in particular shows effects on language outcomes and neurolinguistic processing at the word and sentence levels (e.g., Mayberry & Kluender, 2018). The preliminary data of this project show that late first language acquisition also affects the sub-word level, known as the phonological level (Nielson & Mayberry, in review). When processing the phonology of a sign language, one must visually perceive and manually articulate forms categorized into handshapes, movements, locations, and palm orientations. These categories are referred to as parameters and native signers who acquire ASL from birth exhibit specific patterns of the parameters in their productions and perceptual judgments (e.g., Conlin et al., 2000; Hildebrandt & Corina, 2002). Understanding these parameter patterns provides insight into how native signers process phonology, which is important for fully understanding language processing. Thus, investigating how late L1 signers process phonology is crucial for fully understanding the effects of late first language acquisition on language. The completed first study of this project looked at phonological production and found that late first language signers exhibit a different pattern of parameter errors when compared to native signers. The proposed studies look at phonological perception behaviorally to better understand the systematic effects of late first language acquisition on phonological processing across production and perception (Aim 1), as well as neurolinguistically to identify the impact of late first language acquisition on the loci and time course of phonological processing in the brain (Aim 2). The ultimate goal of this project is to determine the relationship between the behavioral outcomes and the neurolinguistic processing in the brain (Aim 3) to better understand the causes of disordered communication for deaf late L1 signers and prevent them. Identifying the impact of late first language acquisition on phonological processing behaviorally and neurolinguistically is crucial for a greater characterization of the communication of deaf individuals and a deeper understanding of the brain causes associated with normal function and disordered processes of communication. This project will also enhance the applicant’s research training and greatly improve her ability to transition from a graduate student to a productive and independent researcher who is an expert in deaf communication and sign language processing.