The dynamics of (bilingual) language acquisition

The investigation of bilingual language acquisition in deaf learners requires the elaboration of a theoretical framework that accounts for what is acquired (language knowledge) and how this is achieved (learning mechanisms). We have argued that the model that accounts best for the nature of the knowledge acquired is the one developed in the framework of the generative paradigm (section 2.1). This model seeks to provide an adequate description of possible human grammars by fulfilling the dual requirement of accounting for all possible human languages (universal principles) and by complying with the learnability criterion (limited range of variation across languages).

As for the developmental process and the question of how to account for the transition of one developmental stage to the next (developmental problem) (cf. section 2.2) we have maintained that language development is characterised by structure-building processes, that is, elementary structures are progressively expanded, in accordance with the input and the available language knowledge. Furthermore, we have argued, based on a dynamic understanding of the organisation of language we elaborated in earlier work (Plaza-Pust 2000), that changes in grammars do not occur instantaneously but are bound to reorganisa?tion phases. These are typically reflected in the alternate production of target-like and target-deviant properties prior to the eventual implementation of the former (cf. section 2.2.3). On this view, learner errors provide important insights into the dynamics of language development.

Research on bilingual hearing learners has shown that language development in this acquisition scenario does not differ qualitatively from language development in a monolingual language acquisition situation. While there is a general consensus that bilingual learners develop two distinct language systems early on, evidence of language contact phenomena indicates that bilingual learners might pool their resources temporarily (section 2.3.2). The sophisticated combinations of two distinct grammars in mixed utterances is commonly taken as an indication that bilinguals (tacitly) know, by virtue of their innate language endowment (i.e. UG), that grammars are alike in fundamental ways. Furthermore, language mixing has been found to involve specific properties of the languages involved and to occur during specific phases in the bilingual development, in particular, during reorganisation phases. As learners acquire the properties of the target languages, language mixing may take over other (pragmatic) functions.

While these observations have been found to hold of bilingual language acquisition in hearing learners of diverse language pairs, including learners of a sign language and an oral language, the question of whether they would equally hold of bilingual language acquisition in deaf learners remains virtually unexplored. Studies on sign bilingual deaf learners have been primarily conducted from an educational linguistics’ perspective. Scholars have been concerned with the potential impact of sign language competence on literacy development with a view to determine whether bilingual education is of benefit to deaf students. Because of the continuing campaigning against sign bilingual education, the focus on demonstrating a positive link between the two languages comes as no surprise. However, as we remarked, the assumption of a facilitating effect of sign language based on statistical measures revealing correlations between skills in the two languages remains tentative. Without a theoretical model that would explain the links identified, the nature of the interaction (elements linked, direction of the relation) remains unaccounted for.

To date, only little is known about language development in bilingual deaf learners, the scope of the developmental asynchrony in the bilingual acquisition of a sign language and an oral language, and the role of language contact phenomena. Studies have been concerned with the acquisition of sign language or oral language but have not considered the parallel development in both languages. Evidence of language mixing in learner productions has been addressed in relation to the input bilingual deaf children are exposed to, however, without taking their grammatical development in either language into consideration.

The research concomitant to the bilingual programme established in Hamburg provided evidence of cross-modal language contact phenomena in the written productions of the bilingual students investigated. Language mixing was found to represent a temporary phenomenon. Learners were assumed to benefit from their more advanced knowledge of sign language by temporarily filling remaining structural gaps in their written language. However, as the development of grammar was not at the focus of that research it did not delve into establishing whether language mixing involves specific language properties at specific points in the development, or whether the interaction is bidirectional.

Our longitudinal study represents a first attempt at contributing to a better understanding of the dynamics of bilingual language acquisition in deaf learners. Based on quantitative and qualitative analyses of the signed and written data produced by bilingually educated deaf students in Berlin we established individual developmental profiles that provided information on the participants’ competences at the onset of the investigation and the progress they made in the time span covered by the study. The developmental profiles established allowed us to capture the scope of individual variation regarding the progress made in the attainment of the languages. It also allowed us to determine the range of variation at the level of individual learner grammars, in particular, during reorganisation phases. Furthermore, the diagnostic criteria elaborated allowed us to discern the learners’ progress in their attainment of multiple dimensions of complex grammatical phenomena in DGS, some of which go beyond syntax proper. This is in line with a view of grammar as a modularly organised complex system that interacts with various other domains through multiple interfaces.