Vertommen studies the choice of matrix language in two bilingual varieties spoken by second-generation immigrants in the Netherlands: Dutch-Turkish and Dutch-Moroccan Arabic. He finds consistent alternations between grammatical structures defined by Dutch as a matric language versus Turkish or Moroccan Arabic as matrix. He argues that the choice of matric language for sentences and their argument structures is based on cognitive operations underlying the information expressed by these sentences. He sets up a fine-grained theoretical framework to describe these operations (starting from the distinction between categorical and thetic judgments, somehow related to the cognitive distinction between semantic and episodic memory). And he shows that the alternations in question can be seen as an integral part of the grammar of the mixed varieties.