ABSTRACT
In the last two decades, there has been an upsurge of research on the cognitive and neural basis of bilingualism. The initial discovery that the bilingual’s two languages are active regardless of the intention to use one language alone, now replicated in hundreds of studies, has shaped the research agenda. The subsequent research has investigated the consequences of parallel activation of the two languages and considered the circumstances that might constrain language non-selectivity. At the same time, there has been emerging recognition that not all bilinguals are the same. Bilingualism takes different forms across languages and across unique interactional contexts. Understanding variation in language experience becomes a means to identify those linguistic, cognitive, and neural consequences of bilingualism that are universal and those that are language and situation specific. From this perspective, individuals who sign one language and speak or read the other become a critical source of information. The distinct features of sign, and the differences between sign and speech, become a tool that can be exploited to examine the mechanisms that enable dual language use and the consequences that bilingualism imposes on domain general cognition. In this chapter, we review the recent evidence on bilingualism for both deaf and hearing signers. Our review suggests that many of the same principles that characterize spoken bilingualism can be seen in bilinguals who sign one language and speak or read the other. That conclusion does not imply that deaf vs. hearing language users are identical or that languages in different modalities are the same. Instead, the evidence suggests that the co-activation of a bilingual’s two languages comes to shape the functional signatures of bilingualism in ways that are universal and profound.
