The first one introducing the metaphor of a language switch, i.e. the changing from one language to another during a conversation, was Otto Poetzl, an Austrian neurologist and psychiatrist in the 1920ies, when he noticed that a patient, a Czech native speaker (who learned German at age 14) became stuck in one language and wasn't able to get out of that language, or use it.
Poetzl's idea was that this wasn't damage to the language system per se, but that the patient was having difficulties with his ability to switch out of the language.
Since Poetzl this metaphor that there is some sort of a switch to turn one language on, and turn one language off, is commonly used to describe the alternate use of multiple languages.
This language switch has been studied ever since in the neural science literature with regard to bilingualism and many linguists have analyzed the mechanisms of language-switching, or, more commonly "code-switching"(cfr. code-switching is the term used in linguistics: Code-switching occurs when a speaker alternates between two or more languages, or language varieties, in the context of a single conversation).
One of the most common myths about bilingualism is that if a person does code-switching, she/he is doing something wrong, and surely isn't fluent in either of the languages (yet).
In fact, many people – parents, teachers, medical doctors... – worry when they observe that someone (a child or adult) switches between one language and the other and get irritated.
- Will that person ever really be consistent in one of the languages?
- Is this person having trouble to process language?
- Isn't code switching a sign of lack of fluency?
Interestingly, those who switch from one language to another in a conversation are usually very fluent in both languages. It is a verbal skill that requires a high degree of linguistic competence rather than a defect of having insufficient knowledge of the one or the other language!
Therefore, if you notice that someone switches between languages, give him or her a pat on the back!
Parents often tend to assume that if code-switching happens more or less regularly, it will last forever.
In Intermingling languages in children, Prof. François Grosjean lists up the different factors that can lead to code-switching. – What he observes for children also applies to later bilinguals/multilinguals.
The person who switches is simply in the process of becoming bilingual. We usually are dominant in one of our languages and the more dominant language tends to influence the weaker one.
The language mode a person is in while communicating is also a relevant factor: it is about choosing the right language to communicate with. A multilingual will always assess the situation and try to find out:
- Is the interlocutor monolingual, bilingual?
- Does he/she understand the same languages? (more about it here)
If you share more than one language with your interlocutor, chances are high that you switch between those languages when communicating with him/her. It is a very pragmatic choice to mix, to use the words that first pop into your mind when you express your thoughts. The reason this happens is that you want to get your message across as quickly as possible and thinking about the right word in the language you started the sentence with, can require some time. Time we usually don't think we have in normal paced conversations.
How long is this going to last? – It depends on the person and the situation.
What can be understood as a phase in language acquisition/learning, also depends on how often the person uses the different languages involved.
If I am not so fluent in Spanish and have to communicate in that language, chances are high that I will need words from some of my other languages to fill the gap. The same applies to languages I don't use that often anymore and therefore my active vocabulary needs some time to be fully reactivated.
I switched languages when I was a child and still do it, usually when I'm tired or need to talk very fast in an international setting. – I know from my own experience that I need one or two long conversations to "reactivate" my languages and usually am capable to stick to one language then.
Another important fact is that we do not switch languages when we talk with someone who only understands one language – unless we really struggle to find the right words...
If you or a person you know is still acquiring or learning a new language, don’t make him/her feel guilty about mixing the languages.
If he/she is already proficient in the languages and does code-switching and this really bothers you, don’t correct but model the speech by simply repeating the sentence in the language you want to emphasize.
And for the rest: be proud that he/she has such a great linguistic competence!