Children born deaf frequently fail to master spoken language and literacy, and often underperform in school. Despite the advent of cochlear implants, which provide auditory input directly to a deaf child's brain, speech and literacy outcomes remain highly variable, and deaf students still lag behind their hearing peers on most educational outcomes. Recent research suggests that this variability is partly due to deficits in deaf children's general cognitive development. Deaf children seem to be impaired on several higher-level cognitive skills including executive function and implicit learning. In order to fix these problems, we must first identify what causes them. Currently, it is impossible to tell whether these deficits are due to auditory deprivation or to language deprivation. We propose to distinguish these hypotheses by contrasting the performance of two groups of congenitally deaf children: those who have been exposed to sign language since birth (and have never received a cochlear implant ("native signers"), and those who have not been exposed to sign language since birth and have received a cochlear implant ("CI users"). Each group will also be compared to typically hearing controls. Auditory deprivation predicts that both native signers and CI users should be impaired relative to hearing controls;language deprivation predicts that only CI users should be impaired, with native signers performing like hearing controls. If both auditory deprivation and language deprivation play a role, the performance of native signers should fall between CI users and hearing controls. The results have clear implications for the clinical management of deaf children. Evidence supporting the auditory deprivation hypothesis would call for expanding the use of assistive hearing devices. Evidence supporting the language deprivation hypothesis would call for expanding the role of sign language in these children's early years, alongside other evidence-based interventions.
Children born deaf frequently fail to master spoken language and literacy, and often underperform in school. These problems may be due to delayed cognitive development, rather than simply hearing loss. Our research asks whether sign language exposure during infancy can protect against these cognitive problems.