How do people agree on when to switch between languages?

Research Digest by Michela Bonfieni

A recent study reveals how bilinguals who speak the same two languages implicitly agree with each other on when to switch between their languages. The study also shows that switching between languages in the middle of a conversation is as natural and systematic as any other aspect of language.

Bilingual speakers often use bits of their two languages in their sentences. For example, speaking about taxes and savings, two Spanish-English speakers may go about like this:

Speaker 1: “qué dinero?” (‘what money?’)

Speaker 2: “el dinero ese que nos van a dar with the taxes.” (‘the money that they’re going to give us with the taxes.’)

This behaviour is very frequent among bilinguals who live in contexts where both their languages are used. Researchers on bilingualism refer to this as ‘code-switching’, and have dedicated a lot of attention to understand the way it works. Some of the questions they are more interested in are: how people agree on when it is OK to go from one language to the other; and how people avoid getting confused when switching between their languages.

Two researchers at the Pennsylvania State University (USA) decided to look at a big data-set of Spanish-English bilinguals to answer these questions. They selected a huge collection of transcribed conversations between Spanish-English bilinguals and analysed what happened in each conversation when the two speakers inserted one or more words from Spanish in an English sentence, or the other way around.

Specifically, they wanted to see if people were more likely to switch between languages if the person who they were talking to had switched between languages in the same conversation. In other words, they wanted to see if bilingual speakers somehow imitate each other when switching between languages. We all imitate each other to some extent when conversing: we choose the same words, or the same type of sentence, sometimes we adopt a similar accent or even intonation. Researchers call this type of linguistic imitation ‘priming’, and suggest that it is a fundamental mechanism to adapt to the environment and understand each other.

In this study, the two researchers showed that bilinguals were indeed more likely to switch between languages not only if it had happened in the previous sentence, but even if words from the other language had been used as far as ten sentences before. This suggests that they did imitate each other in the long run. Interestingly, though, the researchers also found that people would also ‘imitate themselves’, that is to say, that speakers were consistent in their combined used of the two languages, even when speaking to a different person. This first result suggests that choosing to switch between languages is a consistent behaviour. It also shows that people adapt their choices to the context and to the person they are talking to.

Moreover, the researchers were interested in understanding how the speakers in their study were able to keep one of the two languages as a reference point. What they call the “language of reference” is the language in which the majority of grammatical bits are expressed when switching – bits of the language that keep sentences together, such as the words ‘that’ and ‘the’, as well as verbs expressing actions but also time (for example, ‘ran’ as opposed to ‘run’ conveys information about the past). In other words, they wanted to understand whether switching between languages has some consistency grammatically, or whether ultimately speakers get confused as to what language they are using exactly. Their analysis showed that speakers were choosing the reference language consistently not only with respect to the previous sentence, but to up to the last ten sentences, and consistently within and between sentences.

Switching between languages is a frequent and visible phenomenon in bilinguals, and shows that the two languages of bilingual speakers are always active. But this study shows that this behaviour is not different to the way language works in general, and that it is not random but consistent, and probably useful to the mechanism of adaptation both to the environment and other speakers, so as to ultimately achieve successful communication.

This study was published in the Journal of Memory and Language by Melinda Fricke and Gerrit Jan Kootstra. You can read it at:


  1. How do people agree on when to switch between languages.
    its depends upon the which type of people you are surrounded.

  2. Arlene Anderson says:

    I have observed that my Italian friend switches to her mother tongue instantly when she is giving her twins into trouble for something…but speaks to them in English otherwise 😀

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