Deaf Children of Hearing Parents Have Age-Level Vocabulary Growth When Exposed to American Sign Language by 6 Months of Age

Objective To examine whether children who are deaf or hard of hearing who have hearing parents can develop age-level vocabulary skills when they have early exposure to a sign language. Study design This cross-sectional study of vocabulary size included 78 children who are deaf or hard of hearing between 8 and 68 months of age who were learning American Sign Language (ASL) and had hearing parents. Children who were exposed to ASL before 6 months of age or between 6 and 36 months of age were compared with a reference sample of 104 deaf and hard of hearing children who have parents who are deaf and sign. Results Deaf and hard of hearing children with hearing parents who were exposed to ASL in the first 6 months of life had age-expected receptive and expressive vocabulary growth. Children who had a short delay in ASL exposure had relatively smaller expressive but not receptive vocabulary sizes, and made rapid gains. Conclusions Although hearing parents generally learn ASL alongside their children who are deaf, their children can develop age-expected vocabulary skills when exposed to ASL during infancy. Children who are deaf with hearing parents can predictably and consistently develop age-level vocabularies at rates similar to native signers; early vocabulary skills are robust predictors of development across domains.