Even multilingual children do not always consciously decide which language to use. During my studies in Budapest, I was given the task of studying a Hungarian-speaking student from Slovenia’s language use. For three hours I asked her to address me in her dialect, but it was not possible for her. She could only answer my standard Hungarian questions in the same register I had used. When the time was up, her mother called her on the phone, and then she switched suddenly to her dialect.
In a previous article I explained why it is useful to use your mother tongue with your own child, but what should we do if we are not at home, but in another linguistic environment? In this case, changing the language you speak with your child does not endanger his learning of your mother tongue. Rather, with this behaviour we teach generosity and tolerance towards others. The child knows exactly which language we usually use amongst ourselves, because if he is learning several languages he distinguishes which language to use with who, and each language is tied to the emotions that represent the relationship with that person.
Due to the learning process that, in the case of multilingual children, is dynamic, people's preferred languages can also undergo changes. That is to say, they can change their common language preference with relatives or siblings to another. This change can be complete or segmented by subject; for example, when discussing school matters they might use one language, and another for family matters.
Multilingual children can change from one language to another in an instant if the situation requires it and they have to talk to two people who speak different languages, but it is difficult for them to change the language they usually speak with a specific person. In the case of a new acquaintance, they quickly find out what will be the most suitable common language. This sounds very democratic, but it can be a source of conflict. For example, when a new student comes to class and finds some students who speak their native language, the teacher might them to use another language in class. The intention of the teacher is good, because he wants the linguistic level of these children to increase. But the children might still choose their common language to explain the task to each other. In this case, it is advisable to use the children's translation skills and ask the student who best dominates the vehicular language of the school to explain their working to the teacher. In this way the children who are still learning will hear the same thing that they have just finished discussing in their common language, discussed in another. This method is very useful, especially early on in language learning. It also means that the child can be integrated into a group of native speakers with whom he will use the school language.
Positive emotions towards language are essential for all children and that is why it is not useful to, for example, prohibit the use of a common language in the playground, even if this language is different from the one used in school. On the other hand, in order to improve competence with the language used at in school, it is useful if in extracurricular activities children receive opportunities to create relationships with children with another mother tongue. In this situation, they will have no other option than to use the new language as their common language.
Don´t forget that children love mischief, and multilinguals have even more opportunities to cause it. Sometimes they change from one language to another just to annoy people, or they choose not to use the one that in a specific situation would be the most convenient.