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Discourse Coherence in Bilingualism and SLI

Final Report Summary - DISCOURSE BISLI (Discourse Coherence in Bilingualism and SLI)

Aim of the project
Bilingual children grow up with two languages. Therefore, they cannot hear and speak each of their languages as often as monolingual children do. As a result, bilinguals tend to develop their languages slower and are commonly referred to speech language therapists for screening and intervention. Due to the lack of reliable assessment tools for bilinguals, these children are often misdiagnosed for language impairment, which leads to unnecessary treatments and emotional problems. Alternatively, bilingual children can be under-diagnosed, because speech language therapists may think that their language delay is due to bilingualism, rather than language impairment. In this case, children do not receive speech therapy that they really need.

Hence, insights and tools for differentiating between typically developing bilinguals and children with language impairment are urgently needed. This is exactly what our project set out to achieve. In this study, we compared language production and comprehension by bilinguals with typical language development and monolinguals with and without language impairment. Our main goal was to find a way (e.g. tool, method, analysis) to distinguish between typically developing bilingual children (who may just be a bit slower due to dual language exposure) from bilingual children suffering from a language disorder.

Data and analysis
We looked at language development of bilingual children (aged 3 to 9) in two European countries: Germany and the Netherlands. The bilingual participants were native speakers of Russian, also acquiring Dutch or German either from birth or from around age 3. The performance of the bilingual children was compared to that of monolingual peers with and without language impairment.
In order to assess their language production, we asked the children to tell us a picture story, one in each language. We transcribed the children’s narratives and analysed these anonymous transcriptions on a number of dimensions, with particular emphasis on linguistic phenomena responsible for coherent speech (discourse connectives, pronouns, etc.). The narrative database created in this project has been archived in CHILDES, a large database of child speech open to researchers around the globe.

In order to assess online processing of coherent speech, we collected language comprehension data by means of eye-tracking. Children saw two pictures on a computer screen and heard sentences. From the pattern of their looks during sentence processing, we could determine whether they were able to understand grammatical cues and predict discourse continuation from the information already available in the sentence.

Main findings
Our main and most important finding is that there is a way to distinguish between typically developing bilinguals and children with language impairment. The two groups look very similar in language production, but have clearly different profiles in language processing.

When we compare the narratives produced by bilingual children (in their weaker language) to narratives produced by monolinguals with language impairment, we see a lot of similarities. For example, both groups often use the wrong conjunctions to connect clauses (e.g. ‘and’ instead of ‘but’). These errors are numerous until age six, but are also present in the speech of children as old as eight years of age. Sometimes bilingual children make even more errors than children with language impairment; this is particularly evident in the domain of pronominal gender. Hence, based on errors in speech production it is difficult (of not impossible) to say whether a bilingual child suffers from a language disorder or not. This finding is consonant with the observation that bilingual children are often misdiagnosed or under-diagnosed for language impairment.

However, two distinct profiles emerged when we looked at online comprehension measures. Our results reveal that children with language impairment have difficulty understanding discourse connectives and are not able to predict discourse continuation based on connective semantics. As against this, bilingual children perform as well as typically-developing monolinguals: their gaze patterns clearly show that they know subtle semantic differences between complex discourse connectives and use this information to predict how discourse will unfold. The same pattern emerged in the domain of pronominal gender. Bilingual children under age 6 make a lot of errors in pronoun use, for example saying ‘he’ instead of ‘she’. However, bilinguals of this age do show sensitivity to gender cues in receptive tasks and look at the picture congruent with the gender of the pronoun, just like typically developing monolingual children of their age.

Evidence from our eye-tracking studies suggests that the seemingly similar profiles of bilinguals and children with language impairment (in speech production) probably have different underlying causes. Children with language impairment make errors in their speech because they have difficulty learning the semantics and the grammar of discourse connectors. In contrast, typically developing bilinguals make errors under the influence of their dominant language, but they do know the correct word meanings and grammar rules. In other words, bilingual children sometimes have difficulty inhibiting their dominant language when they are speaking. The capacity to inhibit the dominant response improves with age, as a function of cognitive maturation.
Another crucial finding from this project is that bilingualism does not necessarily lead to problems and language delays. When we look at the dominant language of our bilingual participants – German in Germany and Dutch in the Netherlands – we do not see many differences from monolingual German- and Dutch-speaking children (even though there is some evidence of crosslinguistic influence in the bilingual mind). However, this only holds for children growing up with two languages from birth; children acquiring German or Dutch as their second language do feature some delay and/or deviations in their linguistic development. Furthermore, bilingual children have difficulty with their non-dominant language, that is the language that is not spoken or maintained in the country of residence. Since harmonious bilingual development is essential for a child’s well-being, it is very important to support the acquisition of minority languages, for example, by creating more bilingual schools and kindergartens.

An important implication of this research is that speech language therapists should be aware of the fact that language production of typically developing bilinguals (in their non-dominant language) often looks very similar to that of individuals with language impairment and that (online) comprehension measures provide a much better tool for differentiating between the two groups than language production measures (such as narratives).