Sign Language Acquisition
A child acquiring a sign language appears to be faced with a quite different task than a child acquiring a spoken language. A completely different set of articulators is involved and the language is perceived with a different sensory system. Do the properties of sign languages affect the course and timing of language acquisition? For example, do the iconic properties of sign languages aid in their acquisition? Do the spatial properties of sign language present special challenges for the acquisition process? The studies addressing these questions have investigated Deaf and hearing children acquiring ASL as a native language from their Deaf parents. Deaf children who have hearing parents may be exposed to ASL later in childhood, and we examine the effects of such late acquisition on adult language competence and processing in chapter 6.
The general finding of many, many studies is that Deaf children of Deaf parents acquire sign language in the same way that hearing children of hearing parents acquire a spoken language: Both groups of children pass through the same developmental stages at about the same time and make the same sorts of errors (for reviews, see Bellugi, 1988; Lillo-Martin, 1999; Meier, 1991; Newport & Meier, 1985). These results suggest that the capacities that underlie language acquisition are maturationally controlled and that the psychological, linguistic, and neural mechanisms involved in language acquisition are not specific to speech or audition. In this chapter, we review the nature of language milestones and highlight domains where the study of sign language acquisition helps to unveil the mystery of our uniquely human ability to master complex linguistic systems within the first few years of life.