CEREBRAL LATERALIZATION FOR ASL AND ENGLISH IN DEAF AND HEARING NATIVE AND NON-NATIVE SIGNERS (NEUROLINGUISTICS, AMERICAN SIGN LANGUAGE, BILINGUALISM)

Cerebral lateralization for ASL and English has never been investigated from a bilingual perspective. Researchers have primarily been interested in how the modality difference (signed visual language vs. spoken auditory language) might affect neural organization, or how lack of auditory input might affect normal neurological development. In addition, although recently both Deaf and hearing native signers, and occasionally hearing non-native signers have been included in some studies, Deaf non-native signers have not.; As a group, Deaf non-native signers are very heterogenous due to great differences in education and linguistic background; however, one subset of this group, namely, profoundly, congenitally deaf people who were raised orally with no signing input of any kind until adolescence, provides an opportunity to look at the affect of cerebral lateralization of abnormal early exposure to language.; In this work, cerebral lateralization of ASL and English in Deaf and hearing native and non-native signers is investigated, and set within the context of research done on cerebral lateralization in hearing bilinguals. English words, and static and moving ASL signs were presented tachistiscopically to Deaf and hearing native signers and Deaf and hearing non-native signers. Both the non-native groups had had no exposure to ASL until age 13 or later. In addition, a competency test for ASL and English was administered to all groups.; Results from the ASL competency test clearly differentiate between the native signers and non-native hearing signers on the one hand, and the non-native Deaf signers on the other, indicating that normal acquisition of a first language (regardless of whether it is signed or spoken) is essential for acquiring a second language with native-like fluency. Results from the laterality experiment were inconclusive, but may suggest that native acquisition of ASL has more effect on cerebral lateralization for signed language than does hearing status. These results are discussed within the context of research done with hearing bilinguals.