What makes someone bilingual? There's no easy answer

It's estimated that half the world's population is bilingual, and two-thirds of the world's children grow up in an environment where several languages intersect. But while bilingualism is common, its definitions are varied. They are often based on people's experiences or feelings about language—what they convey and what they represent.

The question also divides linguists. While some emphasize cultural integration as the most important factor, others say that only an individual with equivalent mastery of both languages can truly be considered bilingual.

In 1930, linguist Leonard Bloomfield defined bilingualism as the complete control of two languages, as if each were a mother tongue. This is an idealized vision of a perfect, balanced bilingualism, assuming equivalent written and oral skills in both languages. According to this definition, a bilingual speaker is the sum of two monolinguals. However, this type of bilingualism is extremely rare, and in reality, bilingual people have varied language profiles. Each is unique in their relationship to language.

Lire cet article en français: À partir de quand devient-on bilingue?

There are other theories of bilingualism. The Canadian linguist William F Mackey defines it as the alternating use of two or more languages, while Swiss scholar François Grosjean argues that people who are bilingual use two or more languages in their everyday activities. Vivian Cook, from the UK, defines a bilingual person as a multi-skilled individual who develops language skills consistent with the context of acquisition and use of the second language. Thus, an individual may be considered bilingual even if he or she has only a partial command of the second language.

Where does that leave us? Today, a working definition of bilingualism would correspond to the regular and alternating use of at least two languages by an individual—a category that applies to several million speakers.

Measuring proficiency

Of course, levels of language proficiency can vary widely. According to French linguist, Ranka Bijeljac-Babić, two criteria should be considered when talking about bilingualism: the age at which a second language is acquired and the level of proficiency in the acquired language and mother tongue.

When languages are learned in early childhood, before the age of three or four, this is called "early simultaneous bilingualism" because the two languages develop at more or less the same time. Before puberty, it is called "early consecutive bilingualism," because the second language is added after the first language is already established. When a second language is learned after adolescence, it is called "late bilingualism."

The level of proficiency is more difficult to establish: the same individual may have very different skills in terms of their ability to speak, write and understand. Some people speak a language very well but cannot write it, others have good written skills but very poor oral skills. And of course, it is quite possible to have a good level of both skills in several languages.

Even when both languages are learned simultaneously, the contexts of use will lead to one of the languages being dominant over the other. It is the language that will be activated more spontaneously, will cause the speaker to make fewer pauses and will give rise to the richest, most complex sentences.

The dominant language is not necessarily the first one. An immigrant to a country with a different language will gradually develop a lexicon in that second language. If the second language is used on a daily basis, and the native one is no longer used at all, then the second language will become dominant.

The mental lexicon

In psycholinguistics, the term "mental lexicon" refers to all the information we know about words and their characteristics. Every individual has a mental lexicon that allows them to access linguistic information.

For a monolingual speaker, the mental lexicon is considered to be made up of 40,000 to 60,000 entries, from which they will retrieve information while speaking, reading, listening or writing. In bilingual speakers, the process is similar, but logically there are more entries, because the mental lexicon groups together information from different known languages.

How this happens is a matter of debate. There are two main hypotheses concerning the way bilinguals access information stored in the mental lexicon.

The "language-selective access" hypothesis assumes that when a bilingual person speaks one language, the other is suppressed. Changing from one language to the other would be made by passing through a kind of switch, allowing one language to be "switched off" in order to "switch on" the one being used. This hypothesis assumes that there is no interference between the languages.

The "language-nonselective access" hypothesis assumes that the languages interact within the mental lexicon and influence each other. In identifying a word, the candidates from all known languages would be activated.

When we acquire a second language, the mother tongue serves as a basis for learning concepts in the second language, if it is already in place. The greater the frequency of exposure to the second language, the more the learner will be able to access the meaning of words directly in that language, without mediation through the first.

Losing a native language

Some may remember the scene in the film, L'Auberge Espagnole, in which the main character, played by Romain Duris, dreams he is no longer able to communicate in his native language, French, and can only communicate in the language he has come to learn, Spanish. The phenomenon of attrition described here is quite real—it is possible to "lose" your native language.

According to the work of French linguist Barbara Köpke and her colleagues, language loss like this is mostly observed in people from a migrant background. For an immigrant who has lost contact with their native language, attrition manifests in difficulties in accessing the original mental lexicon. The good news is that, even if contact with the native language is largely cut off, a small amount of contact with other speakers is sufficient to keep the first language functioning well in adults.

Total language attrition can take place in young children—neuroimaging studies of Korean-born French adults who were adopted between the ages of three and six show no persistent trace of the Korean language, even for something as simple as the numbers 1 to 10. There was no difference in brain activation between adoptees and participants in the control group, who had never learned Korean, during a listening task.

These changes are not observed in late bilinguals. Native competence in a language thus becomes "invulnerable" if it is used continuously until puberty.

There are many different paths to bilingualism. While it is not an easy concept to define—and doing so can sometimes be stigmatizing—it is important to value all languages and their various uses.

There is no such thing as a "good" or "bad" bilingual, but studies show that it is important to encourage early language learning, and that regular daily practice will help develop language skills more effectively.

This article is republished from The Conversation under a Creative Commons license. Read the original article.