The development of language and cognition in oral bilingual deaf children

Approximately 50,000 deaf children live in the UK, and between 12 to 28% of these children use two spoken languages (oral bilingual). The newborn hearing screening programme and medical advances in Cochlear Implant (CI) technology have resulted in improved language outcomes for deaf children. Ample research exists on how language and other cognitive skills develop in deaf children who use one spoken language (oral monolingual); however no research conducted in the UK has investigated language development in oral bilingual deaf children. Advantages in some cognitive skills such as Theory of Mind (ToM) and Executive Function (EF) are reported in bilingual hearing children, but disadvantages in the same set of cognitive skills are reported in oral monolingual deaf children. We do not yet know if oral bilingualism might compensate for the disadvantage in cognitive skills in deaf children. This is relevant because it may be related to advice given to parents on raising their child to speak two languages.
The majority of deaf children are born to hearing parents with little or no knowledge of deafness. Therefore, professionals can be highly influential in decisions regarding the child. Research conducted outside the UK reports that parents are often advised to only speak English with their child. However, insufficient proficiency in English to provide rich language models can have significant implications for a child's language development. Despite the influence professionals can have, no identified studies in the UK have explored the advice professionals give to parents regarding a deaf child's ability to acquire two spoken languages.
Objectives: The study will investigate receptive and expressive lexical and grammatical abilities in the English of oral bilingual deaf children compared to age-matched oral monolingual deaf, monolingual hearing and bilingual hearing children. The children's home language will be assessed indirectly via parental questionnaires. The study will also examine ToM and EF skills in oral bilingual deaf children compared to age-matched oral monolingual deaf, monolingual hearing and bilingual hearing peers. By crossing the bilingualism and the deafness dimensions in a 2x2 design we will assess the contribution of each to the children's language and cognitive skills. We currently know that bilingualism may confer an advantage in ToM and EF skills and that deafness has a detrimental effect. An outstanding question is whether bilingualism may have a protective effect in the case of deaf children.
As a complementary strand, the project will provide a comprehensive overview of the advice given by UK professionals to bilingual parents of deaf children on their communication choices, and their professional opinion on whether a deaf child can acquire more than one spoken language. To identify what advice professionals in the UK give on raising a deaf child in a bilingual environment, two surveys will be designed, one for bilingual parents of deaf children and one for professionals who work with deaf children.
This study will crucially inform our understanding of the development of language and cognition in oral bilingual deaf children which could potentially impact the current advice given to parents.