Читать книгу The Secret Life of the Mind: How Our Brain Thinks, Feels and Decides - Mariano Sigman - Страница 18

One of the most passionately debated examples of the collision between biological and cultural predispositions is bilingualism. On one hand, a very common intuitive assumption is: ‘Poor child, just learning to talk is difficult, the kid’s gonna get all mixed up having to learn two languages.’ But the risk of confusion is mitigated by the perception that bilingualism implies a certain cognitive virtuosity.

Bilingualism, actually, offers a concrete example of how some social norms are established without the slightest rational reflection. Society usually considers monolingualism to be the norm, so that the performance of bilinguals is perceived as a deficit or an increment in relation to it. That is not merely convention. Bilingual children have an advantage in the executive functions, but this is never perceived as a deficit in monolinguals’ potential development. Curiously, the monolingual norm is not defined by its popularity; in fact, most children in the world grow up being exposed to more than one language. This is especially true in countries with large immigrant populations. In these homes, languages can be combined in all sorts of forms. As a boy, Bernardo Houssay (later awarded the Nobel Prize for Physiology) lived in Buenos Aires, Argentina (where the official language is Spanish) with his Italian grandparents. His parents spoke little of their parents’ language, and he and his brothers spoke none. So he believed that people, as they aged, turned into Italians.

Cognitive neuroscientific research has conclusively proven that, going against popular belief, the most important landmarks in language acquisition – the moment of comprehending the first words, the development of sentences, among others – are very similar in monolinguals and bilinguals. One of the few differences is that, during infancy, monolinguals have a bigger vocabulary. However, this effect disappears – and even reverts – when the words a bilingual can use in both languages are added to that vocabulary.

A second popular myth is that one shouldn’t mix languages and that each person should speak to a child always in the same language. That is not the case. Some studies in bilingualism are conducted with parents who each speak one language exclusively to their children, which is very typical in border regions, such as where Slovenia meets Italy. In other studies, in bilingual regions such as Quebec or Catalonia, both parents speak both languages. The developmental landmarks in these two situations are identical. And the reason why the babies don’t get confused by one person speaking two languages is because, in order to produce the phonemes of each language, they give gesticular indications – the way they move their mouths and face – of which language they are speaking. Let’s say that one makes a French or an Italian facial expression. These are easy clues for a baby to recognize.

On the other hand, another large group of evidence indicates that bilinguals have a better and faster development of the executive functions; more specifically, in their ability to inhibit and control their attention. Since these faculties are critical in a child’s educational and social development, the advantage of bilingualism now seems quite obvious.

In Catalonia, children grow up in a sociolinguistic context in which Spanish and Catalan are often used in the same conversation. As a consequence, Catalan children develop skills to shift rapidly from one language to the other. Will this social learning process extend to task-switching beyond the domain of language?

To answer this question, César Ávila with his colleagues compared brain activity of monolinguals and Catalan bilinguals who switched between non-linguistic tasks. Participants saw a sequence of objects flashing rapidly in the centre of a screen. For a number of trials they were asked to respond with a button if the object was red, and with another button if it was blue. Then, suddenly, participants were asked to forget about colour and respond using the same buttons about the shape of the object (right button for a square and left button for a circle).

As simple as this sounds, when task instructions switch from colour to shape most people respond more slowly and make more errors. This effect is much smaller in Catalonian bilinguals. Ávila also found that the brain networks used by monolinguals and bilinguals to solve this task are very different. It is not that bilinguals are just increasing slightly the amount of activity in one region; it is that the problem in the brain is solved in an altogether different manner.

To switch between tasks, monolinguals use brain regions of the executive system such as the anterior cingulate and some regions in the frontal cortex. Bilinguals instead engage brain regions of the language network, the same regions they engage to switch between Spanish and Catalan in a fluid conversation.

This means that in task-switching, even if the tasks are non-linguistic (in this case switching between colour and shape), bilinguals engage brain networks for language. Which is to say, bilinguals can recycle those brain structures that are highly specialized for language in monolinguals, and use them for cognitive control beyond the domain of language.

Speaking more than one language also changes the brain’s anatomy. Bilinguals have a greater density of white matter – bundles of neuronal projections – in the anterior cingulate than monolinguals do. And this effect doesn’t pertain only to those who learned more than one language during childhood. It is a characteristic that has been seen also in those who became bilingual later in life, and as such it might be particularly useful in old age, because the integrity of the connections is a decisive element in cognitive reserve. This explains why bilinguals, even when we factor in age, socioeconomic level and other relevant factors, are less prone to developing senile dementias.

To sum up, the study of bilingualism allows us to topple two myths: language development doesn’t slow down in bilingual children, and the same person can mix languages with no problem. What’s more, the effects of bilingualism may go above and beyond the domain of language, helping develop cognitive control. Bilingualism helps children to be captains of their own thought, pilots of their existence. This ability is decisive in their social inclusion, health and future. So perhaps we should promote bilingualism. Amidst so many less effective and more costly methods of stimulating cognitive development, this is a much simpler, beautiful and enduring way to do so.