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.