LANGUAGE, MODALITY AND THE BRAIN: LOOKING AT SIGN LANGUAGES

Establishing which neural systems support processing of signed languages informs a number of important neuroscience and linguistic questions. First, what constitutes the ‘core language system ’- what areas of the brain are involved in language processing regardless of the modality? Evidence will be presented from studies of signers with acquired language impairments as a result of stroke and from functional imaging studies of the processing of BSL and English. Second, do sign language sentences encoding spatial concepts differ from more abstract sentences- does sign language recruit non-linguistic conceptual structures? Results of a study on the processing of BSL sentences with topographic and non-topographic structure will be discussed in relation to this question. The conclusion returns to a consideration of the nature of the ‘core language system ’ and spoken language. Following groundbreaking work by linguists and cognitive scientists over the last thirty years, it is now generally accepted that there are two distinct classes of natural human language: spoken language and signed language, this latter group consisting of the various sign languages of the deaf, such as ASL (American Sign Language) or BSL (British Sign Language)1. The most striking difference between these two classes is that signed language operates in a wholly non-auditory, visuo-spatial medium. How does the medium impact on language itself? Meier (2002) lists a number of the ‘non-effects ’ of the modality (p. 2): Conventional vocabularies: learned pairing of form and meaning Duality of patterning: meaningful units build of meaningless sublexical units, whether units of sound or of gesture: Slips of the tongue/slips of the hand demonstrate the importance of sublexical units In adult processing Productivity: new vocabulary may be added to signed and spoken languages: Derivational morpholog