ABSTRACT
Over past 30 years, linguists and psychologists have extensively studied the communication systems of the deaf (e.g., Klima & Bellugi, 1979; Stokoe, 1960; Stokoe, Casterline, & Croneberg, 1965). This research effort resulted in the description of various sign languages: American Sign Language, French Sign Language, Chinese Sign Language, Swedish Sign Language, to name only a few (see Supalla & Webb, 1995, for a discussion of cross-linguistic comparison). Signed languages are natural languages with phonological, morphological, and syntactic rules that are descriptively and functionally similar to rules found in spoken languages, although they do not correspond to any single spoken language (Klima & Bellugi, 1979). That is, signed languages are not manual translations of spoken languages, but have their own set of linguistic rules that take advantage of the manual-visual modality in which they are produced and transmitted. One of the central findings of signed language research has been to show that human language can exist in either the spoken form or in the gestural form,
