Relationship between the linguistic environments and early bilingual language development of hearing children in deaf-parented families.

We explored variation in the linguistic environments of hearing children of Deaf parents and how it was associated with their early bilingual language development. For that purpose we followed up the children's productive vocabulary (measured with the MCDI; MacArthur Communicative Development Inventory) and syntactic complexity (measured with the MLU10; mean length of the 10 longest utterances the child produced during videorecorded play sessions) in both Finnish Sign Language and spoken Finnish between the ages of 12 and 30 months. Additionally, we developed new methodology for describing the linguistic environments of the children (N = 10). Large variation was uncovered in both the amount and type of language input and language acquisition among the children. Language exposure and increases in productive vocabulary and syntactic complexity were interconnected. Language acquisition was found to be more dependent on the amount of exposure in sign language than in spoken language. This was judged to be related to the status of sign language as a minority language. The results are discussed in terms of parents' language choices, family dynamics in Deaf-parented families and optimal conditions for bilingual development.