Hypotheses about cross-modal language mixing

Bilingual acquisition of sign language and written language in deaf learners not only raises issues regarding developmental trajectories in two languages that differ in their modality of expression and accessibility to deaf learners. It also raises the question about the relation of the two languages in the course of the bilingual development. As we explained previously, the sophisticated combination of two distinct grammars in mixed utterances indicates that bilinguals (tacitly) know, by virtue of their innate language endowment (i.e. UG), that grammars are alike in fundamental ways. This knowledge is the basis for the pooling of resources in the course of the bilingual development. Does this assumption hold equally of bilingual deaf learners acquiring two languages that differ in their modality of expression?

Strict separation. One possible assumption would be that the modality difference leads sign bilingual learners to the assumption that they are dealing with two completely different systems. If the modality difference serves as unambiguous cue for a strict separation of both languages from the beginning learners are not expected to pool their resources. Hence, no contact phenomena are expected to occur in the learner data. Recall that considerations along these lines have been put forward in studies conducted in the tradition of Cummins’ Interdependence hypothesis (cf. section 1.3.2).

Separation and interaction. Alternatively, we may assume that learners of a sign language and a written language have a tacit knowledge about the universal (equivalent) properties of natural human languages at an abstract level. Hence, much like learners in other acquisition situations, they too are expected to develop two separate linguistic systems and to use their linguistic resources creatively in the course of their bilingual development.

(a) Evidence for cross-modal language mixing. Cross-modal (signed/spoken) language mixing in interactions among adult bilingual signers and between deaf parents and their deaf children (Baker & Van den Bogaerde 2008) provides support for the assumption that deaf bimodal bilinguals, too, know about the equivalences of the two languages at a deeper level. Additional support for this hypothesis can be gleaned from the studies undertaken in the context of the research concomitant to the Hamburg bilingual education programme (see Pla- za-Pust 2016 for a discussion). Gunther et al. (2004) found evidence for crossmodal (signed/written) language mixing in written productions of bilingual deaf

students (the issue of whether language mixing also occurred in sign language productions of the students was not addressed). Following Gunther et al. (2004), the bilingual deaf learners investigated compensated temporary gaps in their written language by borrowing sign language structures. Crucially, DGS influence along these lines was found to represent a temporary phenomenon in the written data collected. As the learners’ knowledge of written German increased, the incidence of DGS borrowings decreased (cf. Gunther et al. 2004; Schafke 2005). Further, the longitudinal study revealed that learners differed with respect to whether or not they made use of DGS borrowings.

With respect to the DGS properties mixed, the authors mention borrowings involving word order (cf. example (13) which exhibits the verb-final order characteristic of DGS), subject drop (cf. (14)), and the use of the preposition auf (‘on’) (dubbed by the authors as directional preposition to describe its use to mark the direction of the activity, as it would be the case in DGS directional verbs⁷) (cf. (15)). Other written productions exhibit a more subtle type of influence from DGS. Consider, for example, (16) and (17). For readers unaware of the bilingual background of the children and unfamiliar with the properties of DGS the deviances in these sequences of elements remain unaccounted for. However, from a bilingual perspective, target-deviant constructions such as (13)-(17) (from Gunther & Schafke 2004: 239-242, our transl.) make apparent that learners make use of the linguistic resources available to them in both languages.

Later in this work (section 3.1.3.2) we will explain the use of the DGS sign glossed AUF with some verbs to mark agreement (note that the notion of directional verb is used in some publications on DGS to refer to agreement verbs).

Unfortunately, the Hamburg studies only provide a global picture of language mixing given the focus on narrative development and text levels attained by the participants. However, the hypothesis that DGS borrowings serve the function of a relief strategy is in line with current assumptions in the field of bilingualism research we explained in section 2.3.2.

Evidence for language mixing was also obtained in Leuninger et al.’s (2003) case study of M., a deaf child born to deaf parents and raised in DGS. According to the authors, M.’s DGS knowledge exerts an influence on her written language acquisition. At the level of word order, verb-final structures (cf. examples (18)- (19)) were found to predominate in her written productions. Further, temporal information typically appeared in sentence-initial position (cf. (19)) as it would be the case in DGS. The authors remark that some German words are categorised according to their equivalent in DGS. For example in (20) heifi Sonne (‘hot sun’) is used as a verb (in the sense of burn), and grund (‘reason’) in (19) is attributed the status of a conjunction.

Leuninger et al.’s assumptions (2003: 32f.) about the role of language mixing in deaf learners written productions draw on current hypotheses about (bilingual) language acquisition, including the dynamic approach to second language acquisition we elaborated in earlier work (cf. section 2.2.3 for a summary). Suffice it to mention here that language borrowing (or, in their terms, language transfer) is regarded as a developmentally constrained phenomenon that is bound to the organisation of multilingual knowledge (for further details on the theoretical underpinnings of their analysis see Leuninger et al. 2003: 29f.).

• (b) Modality as an ambiguous cue. Evidence of language mixing does not exclude the possibility that the modality difference serves as an additional cue for the differentiation of the languages involved, as does person differentiation in case the parents choose the so-called partner principle (also one person-one language principle) as the language policy adopted in the family or a domain specific use of the languages. However, the diversity of languages and communication systems used in the bilingual classroom (cf. section 1.3.2.1), including manual systems that are used to represent the oral language in the visual mode, qualifies the use of the modality difference as an unambiguous cue. Rather, learners exposed to a sign language and a signed system are confronted with the task of using more subtle linguistic properties as an indicator for language separation.
• (c) The role of mixing changing over time. Turning to the developmental dimension of language mixing in relation to the organisation of multilingual knowledge, the question arises whether cross-modal language contact phenomena, too, represent developmentally constrained phenomena, affecting specific properties of the developing learner systems. First insights were obtained in the studies conducted on the bilingual deaf learners in Hamburg. As we mentioned previously, in these studies, the role of language mixing was found to decrease as learners advanced in their acquisition of the target L2 written language. However, as the focus of that research was on narrative development, no further details were provided on whether language mixing affected specific language properties at specific points in the development. Neither was the issue addressed of whether the interaction was bidirectional. Recall that language mixing need not occur in one direction only, as different linguistic properties might be acquired first in one language or the other. Another issue that needs to be addressed from a developmental perspective concerns the functions served by language contact phenomena. The assumption that language mixing is a developmentally constrained phenomenon implies that once the target structural properties are established, language mixing may serve other, i.e. pragmatic functions (code-switching).