Sign bilingualism: a developmental linguistics perspective

Throughout the last decades, bilingual learners have had numerous opportunities to demonstrate the sophisticated and creative nature of their (learner) knowledge in research dedicated to their bilingual development. Utterances like the ones provided in (1) and (2) produced by the German/English bilingual child Hannah constitute vivid examples of how bilingual deaf children express the awareness about their own bilingualism and their knowledge about the two languages quite early in their development (Tracy & Gawlitzek-Maiwald 2000: 514):

Studies have not only shown that bilingual children like Hannah are aware about the differences between the languages they are acquiring. They have also shown that bilingual learners’ language development is similar to that of monolingual children. Monolingual and simultaneous bilingual language learners’ development has also been compared with other types of multilingual development characterised by the acquisition of an additional language after the first has already been attained (in childhood or in adulthood). What is common to this research is that it focuses on the identification of the main milestones in the attainment of the target grammar, and on the comparison of developmental sequences across acquisition situations. In addition, scholars have been concerned with language contact phenomena and what they reveal about the organisation of multilingual knowledge. Unlike monolingual learners, bilingual learners can resort to another language in case they have problems in retrieving a word in one language, or in order to compensate structural gaps in one language. Lexical and structural borrowings, manifested in mixed utterances, provide evidence for a sophisticated pooling of linguistic resources in the course of the development of a multilingual competence.

While the progressive convergence of the different lines of research into language development in different acquisition situations has provided important insights into differences and commonalities across acquisition types, little is known about the bilingual development of deaf learners acquiring a sign language and an oral language. Owing to the sociolinguistic situation of deaf learners described previously (cf. chapter 1), studies into the type of family bilingualism that abound in research on hearing children (Lanza 1997: 10) are virtually non-existent in the case of deaf children (the longitudinal investigation of NGT- Dutch bilingual deaf children represents a remarkable exception, cf. Baker & Van den Bogaerde 2008). Commonly, studies on the acquisition of sign language in native deaf learners of the language have not taken their oral development into consideration despite the circumstance that these learners acquire sign language in a bilingual context. Cross-modal language contact phenomena have been studied in relation to the input bilingual deaf children obtain in the home (van den Bogaerde 2000; Baker & van den Bogaerde 2008), but they have not been investigated in relation to the grammatical development in either language.

The implementation of sign bilingual education programmes in the late 20^th century in several countries opened a new perspective in research on language acquisition of deaf learners, hitherto determined by a pathological view of deafness that regarded language development in this population as an idiosyncratic phenomenon. Bilingually educated deaf learners, unlike their monolingual peers, are exposed to a variety of languages and codes, including sign language, spoken language, written language, signed systems, and fingerspelling. What does their linguistic behaviour reveal about their bilingual language development? Questions that arise with respect to the development of sign bilingualism in deaf learners concern the nature of the developmental trajectories in either language and the role of the potential interaction of the learner systems in the course of the bilingual development. The assessment of deaf learners’ bilingual language acquisition along these lines requires the elaboration of a theoretical framework that seeks to account for what is acquired and how this might be achieved.

We will expand on this framework in the following sections. We begin with a presentation of the main assumptions about the nature of language knowledge proposed within the generative paradigm. We will then turn to current hypotheses about language acquisition elaborated within this framework, and present our dynamic approach to the complex interplay of innate (internal) and environmental (external) factors that determine the development of learner grammars. Subsequently, we will summarise current assumptions about language separation and interaction in bilingual first and second language acquisition, before narrowing the focus on the main research questions that arise in relation to the bilingual acquisition of sign language and oral language in deaf learners.