Modelling bottom-up and top-down linguistic knowledge across different contexts of bilingual development – BILDEV

Although there are far more people in the world capable of using more than one language than there are monolinguals, idealized monolingual speakers remain the main source of evidence for our understanding of language knowledge, use, processing and acquisition. We move bilingualism into the centre of linguistic inquiry because the ability to acquire, maintain and use more than one language is a key component of the human language faculty. This project systematically models how environmental and cognitive factors shape language development across different populations of bilingual speakers.
Using the acquisition and maintenance of grammatical gender in bilingual adults as a lens into linguistic knowledge and processing, this project assesses how input frequency and age of second-language (L2) acquisition affect item-specific and rule-based aspects of lexical and grammatical development among French-German and English-German (i) simultaneous bilinguals (ii) early (child) L2 learners (iii) late (adult) L2 learners as well as (iv) child immigrants (early attriters) and (v) adult immigrants (late attriters).
We focus on German as the target language among speakers with French or English as the other language, collecting data from a total of 480 participants in France, the UK and Germany. In a range of production and comprehension experiments (e.g. eye-tracking), we test for differences in how these bilinguals rely on phonological rules versus item frequency in identifying the lexical gender of words and how they recruit grammatical rules versus non-grammatical cues in the construction of syntactic gender agreement. Using a large data set collected in different linguistic environments, the project systematically delineates the scope of cross-linguistic influence and it models the contributions of age of acquisition, frequency of use and language dominance as continuous variables. We hypothesize that age of acquisition and cross-linguistic influence categorically constrain the relative weighting of rule-sensitivity versus reliance of input frequency in the grammatical development, while input frequency and cross-linguistic influence have linear and additive effects in lexical learning. The analyses use mixed-effects regression models as well as structural equation modelling to model the relative contributions and interactions of frequency, age as well as social and environmental factors in lexical and grammatical acquisition and attrition.
This project yields a better understanding of how language development is guided by top-down and bottom-up factors at the intersection of the lexicon and the grammar at different stages throughout the human lifespan. By charting how bilingual experience shapes language knowledge and processing, it provides novel insights into the key theoretical question of the degree and scope to which language learning is subserved by domain-general or domain-specific skills.