Research on the acquisition of DGS (and other sign languages)

The child’s job does not look easy. (Bellugi et al. 1990:17)

Following our sketch of the main characteristics of DGS with a view to identifying what is acquired in sign language acquisition we turn now to the available research on sign language acquisition, with a focus on the main developmental milestones in the acquisition of DGS. Before, however, some notes are due regarding the research available.

Acquisition scenarios. One major difference between research into spoken language acquisition and sign language acquisition concerns the type of acquisitions situations that have been examined in the research. Thus, for example, the acquisition of German is well documented for different acquisition situations (child monolingual and bilingual, as well as adult bilingual), whereas the only available study on DGS acquisition concerns two children of native DGS signers. Comparative data of different types of learners (with respect to their age of exposure) are available for ASL; however, these studies are largely cross-sectional, with a focus on a quantitative account of the skills measured. Qualitative studies are available, but they concern individual aspects of the language. Thus far the available evidence has not been interpreted in terms of a developmental sequence, although some attempts have been made to summarise the characteristics of different developmental phases (cf. Baker et al. 2005 and Chen-Pichler 2012 for overviews). Finally, developmental studies are available for children who attained sign language as a first language at home. Based on what we know about the sociolinguistic situation of deaf individuals (cf. chapter 1.2) we need to acknowledge that these children, too, are growing up in a bilingual environment although this aspect is seldom considered. Although sign language is most probably their preferred and dominant language, the acquisition situation is not monolingual in a strict sense, because the language of the environment (the oral language) is present to a greater or lesser extent in their everyday lives. Van den Bogaerde and Baker’s findings (2008) concerning NGT-Dutch language mixing in the input to and output from deaf children provide intriguing evidence of how parents and children combine the two languages in their productions.

Theoretical approaches. There is a general lack of a uniform approach to sign language acquisition that would be based on a common theoretical framework and seek to systematically account for the phenomena observed (see Hanel 2005: 146 for a similar critique along these lines). Typically, studies on sign language acquisition contain descriptive accounts of children’s productions at different ages, including the documentation of error types. As outlined previously, however, a comprehensive understanding of sign language development will only be possible if the findings are analysed in the light of linguistic theory and current models of language acquisition. Without a theoretical foundation, whether or not different error types are related, and whether this is the consequence of unspecified or unavailable structures, cannot be decided. Hence, some of the developmental sequences proposed in the literature contain numerous developmental phases which seem to be distinguished by error type or grammatical property that becomes productive. In addition, a systematic comparison of these findings reveals that they do not always coincide in the timing of when grammatical phenomena become productive, which is related to individual variation, on the one hand, and on the criteria used to establish “productivity” on the other hand. Finally, there is also considerable variation concerning the phenomena taken into consideration, with different definitions of what is counted as agreement, for example.

With these issues in mind, we turn next to a critical appraisal of the major findings documented in the literature about the main developmental patterns in the acquisition of sign languages. In our discussion, we will focus on three main areas of language knowledge, namely, word order, morpho-syntax, and the syntax-discourse interface. Based on our descriptive framework of DGS, the acquisition task involves the mastery of several phenomena pertaining to these areas (cf. Table 3.9 for an overview of the phenomena considered in this study).

Table 3.9: Acquisition of DGS: linguistic areas and related structures, processes, and properties.