Leiden Language Blog

‘Bilingual grammar’: on the acquisition of cognate rules

‘Bilingual grammar’: on the acquisition of cognate rules

I was born in Rotterdam and my parents always spoke Dutch to me. When I was five years old we moved to a small village in Fryslân, a bilingual province in the north of the Netherlands. Most people in our village spoke not only Dutch, but also Frisian, which is the officially recognized minority language in Fryslân. I still remember my first day in school: the teacher was reading in Frisian, but translated everything into Dutch for me and my sister. This only happened on the first day. The next day we had to start learning the language.

If I am to believe my father, my sister and I were able to speak Frisian within two months. This may, however, not be true, since parents usually overestimate the capacities of their own children. What I do believe is that we were able to understand Frisian very quickly, because Frisian and Dutch are very closely related languages that share many cognates. These are words that overlap in form and meaning across the two languages. Examples of cognates are the Dutch word poes ‘cat’, which is also poes in Frisian, and the Dutch word emmer ‘bucket’, which is only a little different from its Frisian equivalent amer.

Besides a large list of cognates, Frisian and Dutch share many cognate rules. These are regular correspondences between the two sound systems. An example is the Frisian ending -ân, which corresponds to the Dutch ending -and, as in the cognate pairs hân-hand ‘hand’, strân-strand ‘beach’ and lân-land ‘country’. My colleagues and I investigated whether Frisian-Dutch bilingual children acquire these rules, and if so, how they do it.

We found that bilingual children indeed learn cognate rules as they grow older and that the learning of these rules is easiest for children with high verbal working memory skills. Verbal working memory is the ability to store and manipulate verbal information, and, among other things, it is important for the acquisition of grammar. Our finding that verbal working memory is also important for the acquisition of cognate rules suggests that the acquisition of regularities across languages (cognate rules) is similar to the acquisition of regularities within a language (grammar).

Cognate rules could thus be viewed as a special form of grammar that is only available to bilinguals. Without knowing it, my sister and I not only learned the vocabulary and grammar of Dutch and Frisian, but also a special form of grammar that connects our vocabulary of Dutch to our vocabulary of Frisian.


Bosma, E., Blom, E., Hoekstra, E., & Versloot, A. (2016). A longitudinal study on the gradual cognate facilitation effect in bilingual children’s Frisian receptive vocabulary. International Journal of Bilingual Education and Bilingualism, 1-15.

Bosma, E., Heeringa, W., Hoekstra, E., Versloot, A., & Blom, E. (2017). Verbal working memory is related to the acquisition of cross-linguistic phonological regularities. Frontiers in Psychology, 8, 1487.

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