by: Lauren Berger, Naomi Caselli, Jennie Pyers, & Amy Lieberman

This is a post about a longer article:

Caselli, N., Pyers, J., & Lieberman, A. (2021). Deaf children of hearing parents have age-level vocabulary growth when exposed to ASL by six-months. The Journal of Pediatrics.

Many deaf and hard-of-hearing (DHH) children born to hearing parents experience language delays because they have limited or no access to speech, and their parents often do not know a sign language at the time of birth. Language delays can negatively impact many aspects of development. Some hearing parents expose their DHH child exclusively to spoken language, and are often discouraged from exposing their children to a sign language because it is thought to be difficult or impossible for hearing parents to learn enough ASL to be a language model for their child. This is true despite evidence that even with the most advanced hearing technology and speech interventions, many DHH children will not develop age-expected spoken language skills. In this study, we wanted to explore how well DHH children with hearing parents can learn ASL, and asked if early exposure to sign language can result in age-appropriate vocabulary growth among DHH children with hearing parents.

We compared vocabulary growth patterns of DHH children with hearing parents to DHH children with deaf parents. We grouped children with hearing parents into those with early (<6 months old) exposure and slightly later (6–36 months old) exposure to ASL. DHH children whose hearing parents exposed them to ASL by six months of age showed similar vocabulary growth as that of DHH children with deaf parents. DHH children who were exposed between 6–36 months were slightly delayed but were still able to make rapid gains in their receptive vocabulary skills.

Correlation ≠ causation:

It is not feasible to control all possible factors so that the only difference between groups is that DHH infants were exposed to ASL before or after 6 months. The strong vocabulary growth of DHH children exposed early to ASL may be driven by that early exposure to language or by another factor that correlates with early access to language. For example, the hearing parents who joined this study might be more motivated to learn ASL with their DHH children, or have increased access to ASL learning resources. We also can’t pinpoint here whether children are primarily learning from their parents, or from a combination of parents, early intervention teachers, and peers. More research is needed to nail down exactly what made the language learning environments so effective for the children in this study. Nevertheless, this study provides evidence that DHH children of hearing parents can learn ASL, that hearing parents can support healthy ASL development in their DHH children, and that learning ASL is perhaps a less risky option than spoken language-only approaches.

Main points:

• DHH infants generally do not have age-level spoken language vocabularies
• Some people have argued that hearing parents should not teach ASL to their DHH children if they are not fluent in ASL themselves
• We found that hearing parents who learned ASL at the same time as their DHH infants supported their infants’ ASL vocabulary acquisition just as well as deaf parents, even if hearing parents were not fluent yet
• We found that DHH children with hearing parents who are exposed to ASL by 6 months have age-appropriate ASL vocabulary growth

Implications & future directions:

• Introducing ASL to DHH children may be an important tool for mitigating the risks associated with language deprivation; learning ASL and spoken English are not necessarily mutually exclusive
• Early age-appropriate vocabulary acquisition is a great predictor of later cognitive development, but in many cases of severe language delays, rapid gains in vocabulary growth is possible while lagging in other areas of language acquisition. More work is needed to determine whether ASL vocabulary growth is a good predictor of later cognitive development in the case of delayed access to a first language
• Further work is needed to determine what level of ASL proficiency hearing parents need in order to support healthy ASL vocabulary acquisition in DHH children