Beeldmerk 2in1project
Beeldmerk 2in1project


Bilingualism in children

How does one child acquire and use two different languages? Children who are raised bilingually usually know which language they should speak to a person and it is not always obvious that these children are bilingual.

However, there are noticeable differences between bilingual children and their monolingual peers. For example, ‘de beker van Sharon’ is a common Dutch expression, which could be literally translated as ‘the cup of Sharon’. Although this is not wrong, English native speakers would hardly ever use this expression. They would say ‘Sharon’s cup’. This is an example of the structure of one language being incorporated into another.

Influence of one language on the other

The aim of the 2in1 project was to examine how a bilingual child’s languages affect each other and the circumstances under which this occurs. Until now, this issue was primarily examined in bilingual adults. The project also investigated whether the effect between languages is the same for all language combinations. And asked whether this depends on which two languages the child learns, which language is dominant in his/her environment, or how proficient the child is in both languages.

The project focussed on children between three and ten years of age, who are growing up in families where German, English, Greek or Turkish is spoken. The researchers also focussed on what happens after this age, specifically in adolescents and adults aged between 15 to 40 who have grown up speaking Dutch and German or Dutch and English.

The 2in1 project tried to provide answers to various questions, including:

  • How and when do a bilingual child’s two languages influence each other?
  • What does this tell us about the way in which two languages are acquired and used in the same head?
  • Is the way in which the languages influence each other the same for all language combinations, for example, Dutch-German and Dutch-Turkish, or are there differences?
  • Does it matter which language is dominant in the child’s environment?
  • Does a language need to be particularly active in the child’s mind for it to influence the other language?

What have we discovered so far?

Listen to 2in1 researchers Chantal van Dijk and Elly Koutamanis in the Kletsheads podcast where they talk about their research. Chantal talks about the results of her thesis in the episode How bilingual children's languages influence each other. Elly discusses how bilingual children deal with learning words in two language in How the bilingual mind handles words from two languages.

Kletsheads Podcast

Kletsheads is a podcast created by 2in1 project lead, Sharon Unsworth. The podcast focuses on multilingual children and is meant for parents, teachers and therapists. Some of our own researchers share their knowledge about multilingualism in Kletsheads! You can find the podcast in your favourite podcast app.


  • Dr Sharon Unsworth, project leader
  • Dr Gerrit Jan Kootstra, postdoc in the 2in1 project
  • Chantal van Dijk, PhD candidate in the 2in1 project
  • Figen Karaca, PhD candidate in the 2in1 project
  • Elly Koutamanis, PhD candidate in the 2in1 project
  • Jasmijn van Bosch, in 2017 intern bij het 2in1 project
  • Elise van Wonderen, in 2017 intern bij het 2in1 project
  • Joyce van Zwet, in 2021-2022 intern bij het 2in1 project


We’ve presented our research at various academic conferences in the Netherlands, Germany, the UK, the US, Canada and Norway.  Our scientific publications so far:

van Dijk, C.N., van Wonderen, E., *Koutamanis, E., Kootstra, G.J., Dijkstra, T.D. & Unsworth, S. (2021). Cross-linguistic influence in simultaneous and early sequential bilingual children: a meta-analysis. Journal of Child Language. DOI: [Open Access]

van Dijk, C.N., van Wonderen, E., Koutamanis, E., Kootstra, G.J., Dijkstra, T.D. & Unsworth, S. (2022). Cross-linguistic influence in simultaneous and early sequential bilingual children: a meta-analysis. Journal of Child Language. doi:10.1017/S030500092100033 [Open Access]

Koutamanis, E.K.A., Koostra, G.J., Dijkstra, A.F.J. & Unsworth, S. (2021). Lexical priming as evidence for languag-nonselective access in the simultaneous bilingual child’s lexicon. In D. Dionne * L.-A. Vidal Covas (Eds.), BUCLD 45: Proceedings of the 45th annual Boston University Conference on Language Development (pp. 413-430). Somerville, MA: Cascadilla Press.

van Wonderen, & Unsworth, S. (2020). Testing the validity of the Cross-Linguistic Lexical Task as a measure of language proficiency in bilingual children. Journal of Child Language. DOI: [Open Access]

Bosch, J. & Unsworth, S. (2020). Cross-linguistic influence in word order: Effects of age, dominance and surface overlap. Linguistic Approaches to Bilingualism 



Contact information

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