Effects of early auditory experience on word learning and speech perception in deaf children with cochlear implants: implications for sensitive periods of language development.

HYPOTHESIS: That early word learning and speech perception skills have different sensitive periods and that very early implantation may affect later vocabulary outcomes more than speech perception outcomes.
BACKGROUND: Several studies have found that deaf children who receive cochlear implants before 3 years of age tend to have better speech perception outcomes than children implanted later. Recent studies have not found age-at-implantation effects on speech perception or central auditory processing among children implanted younger than 2 years, suggesting that there may be a sensitive period for speech perception skills that closes by around 3 years of age. There has been very little work investigating possible sensitive periods for other language skills, such as the ability to learn words. Recent work suggests the possibility that the development of word-learning skills may have an earlier sensitive period than the development of speech perception skills.
METHODS: Assess speech perception and vocabulary outcomes in children implanted before 13 months of age and in children implanted between 16 and 23 months of age.
RESULTS: Children implanted during the first year of life had better vocabulary outcomes than children implanted during the second year of life. However, earlier implanted children did not show better speech perception outcomes than later implanted children.
CONCLUSION: There may be an earlier sensitive period for developing the ability to associate the sound patterns of words to their referents than for developing speech perception and central auditory processing skills.