Do bilinguals create two different sets of vocabulary for two domains?

The central research question is how intensive exposure to the majority language at school affects the development of vocabulary. In a cross-sectional study with a longitudinal subsample follow-up, we investigated the development of vocabulary during the first four years at school, as vocabulary development is considered an important factor regarding bilingual children’s success at school. The sample consisted of 126 bilingual Russian/German-speaking children aged 6;0 to 10;11 years in Germany, who were tested for expressive and receptive vocabulary using a picture naming task.
Our results show that while the majority language is acquired at an expected rate, the heritage language’s extensive vocabulary does not develop further over the course of primary school attendance. The overlap of the vocabularies increases. Additionally, the number of items that are named exclusively in the majority language increases, whereas the number of items that are named exclusively in the heritage language decreases.