Specific Language Impairment in Deaf and Hard-of-Hearing Children Who Use a Signed Language

The issue


Around 7% of hearing children of school-starting age have a language learning impairment when there are no concerns about other areas of their development. Several terms are used in the clinical, educational and research literature, but “specific language impairment,” often abbreviated to SLI, is the term that we will use here. SLI is of concern because children who are affected by it can continue to have language difficulties into adulthood, and their difficulties are likely to impact negatively on their educational and career attainments.

Deaf and hard-of-hearing children are traditionally excluded from a diagnosis of SLI by Speech-Language Pathologists because their deafness is very likely to impact on their acquisition of spoken language. Yet SLI logically should exist in deaf children who are learning a signed language. Research from our lab in the United Kingdom over the past decade, involving deaf children who are learning British Sign Language (BSL), suggests that this is indeed the case.

What we know

We now know that SLI does exist in signing children. We are beginning to characterize SLI in BSL using existing BSL assessments and experimental tasks adapted from spoken English. In some ways,  SLI in signed languages looks very similar to SLI in spoken languages. Children with sign SLI have difficulties comprehending and producing grammatical structures and have difficulties producing narratives compared to deaf signers whose language development is not causing concern. Their difficulties with producing individual signs and learning new signs, however, seem less severe. This is the pattern found in spoken language SLI too.

One of the challenges is to separate SLI from the considerable variation that exists in sign language development due to the fact that the majority of deaf children are not exposed to sign language from birth, and are therefore learning through delayed and often sub-optimal input. A language delay that results from late exposure to sign language is not the same as having a language-learning impairment, although of course both can be at play in the same child. Our research tells us that Teachers of the Deaf and Speech-Language Pathologists who are experienced in working with deaf signers are quite accurate in identifying children whose sign language development is not proceeding as well as would be expected relative to their deaf peers, even when the children concerned are not native signers.

What we don’t know

There are still many things that we don’t know about SLI in signed languages. Firstly, children have not been studied over a period of time, so we have no idea what happens as they get older: we do not know whether their language difficulties get more severe or whether they catch up with their typically-developing deaf peers. We know from the research literature on spoken SLI that there is likely to be wide variation in outcomes. But what that variation looks like for sign SLI and what factors predict that variation are things we currently do not understand. Indeed, we need more research on the variability in the pace of language learning across all signers, including those whose language development is not causing concern.

Secondly, the vast majority of research on sign SLI has been carried out in BSL. Although research groups in other countries are beginning to identify SLI in their signed languages, we don’t know whether it will have the same characteristics in those languages, although we predict that it will look very similar. And thirdly, we don’t yet know what interventions can successfully support sign language learning in children with sign SLI.


Parents, educators and clinicians should be alert to the possibility that if a deaf child is not making as much progress in their sign language development as would be expected, they might have SLI. This underlying difficulty might also impair their acquisition of spoken languages above and beyond their deafness.

It might be suggested that a deaf child who does not sign well would be best placed in a rich signing environment, in other words, given more sign language input. However, if the child has SLI, he or she is also likely to require specialist sign language therapy, since clinical experience suggests that language enrichment interventions alone are not sufficient.

We need reliable and valid sign language assessments in order to diagnose SLI in sign language learners and in order to characterise their profile of language strengths and weaknesses. We also need interventions to support sign language learning in those children. Much remains to be accomplished.

Posted on April 1, 2016 by
Chloë Marshall
UCL Institute of Education
University College London, United Kingdom
chloe.marshall {at} ucl.ac.uk

Gary Morgan
City University London, United Kingdom
g.morgan {at} city.ac.uk

Further reading