SPEAKING two languages rather than just one has
obvious practical benefits in an increasingly globalized world. But in recent
years, scientists have begun to show that the advantages of bilingualism are
even more fundamental than being able to converse with a wider range of people.
Being bilingual, it turns out, makes you smarter. It can have a profound effect
on your brain, improving cognitive skills not related to language and even
shielding against dementia in old age.
This view of bilingualism is remarkably
different from the understanding of bilingualism through much of the 20th
century. Researchers, educators and policy makers long considered a second
language to be an interference, cognitively speaking, that hindered a child’s
academic and intellectual development.
They were not wrong about the
interference: there is ample evidence that in a bilingual’s brain both language
systems are active even when he is using only one language, thus creating
situations in which one system obstructs the other. But this interference,
researchers are finding out, isn’t so much a handicap as a blessing in
disguise. It forces the brain to resolve internal conflict, giving the mind a
workout that strengthens its cognitive muscles.
Bilinguals, for instance, seem to be more
adept than monolinguals at solving certain kinds of mental puzzles. In a 2004 study by the psychologists Ellen Bialystok and
Michelle Martin-Rhee, bilingual and monolingual preschoolers were asked to sort
blue circles and red squares presented on a computer screen into two digital
bins — one marked with a blue square and the other marked with a red circle.
In the first task, the children had to
sort the shapes by color, placing blue circles in the bin marked with the blue
square and red squares in the bin marked with the red circle. Both groups did
this with comparable ease. Next, the children were asked to sort by shape,
which was more challenging because it required placing the images in a bin
marked with a conflicting color. The bilinguals were quicker at performing this
task.
The collective evidence from a number of
such studies suggests that the bilingual experience improves the brain’s
so-called executive function — a command system that directs the attention
processes that we use for planning, solving problems and performing various
other mentally demanding tasks. These processes include ignoring distractions
to stay focused, switching attention willfully from one thing to another and
holding information in mind — like remembering a sequence of directions while
driving.
Why does the tussle between two
simultaneously active language systems improve these aspects of cognition?
Until recently, researchers thought the bilingual advantage stemmed primarily
from an ability for inhibition that was honed by the exercise
of suppressing one language system: this suppression, it was thought, would
help train the bilingual mind to ignore distractions in other contexts. But
that explanation increasingly appears to be inadequate, since studies have
shown that bilinguals perform better than monolinguals even at tasks that do
not require inhibition, like threading a line through an ascending series of
numbers scattered randomly on a page.
The key difference between bilinguals and
monolinguals may be more basic: a heightened ability to monitor the
environment. “Bilinguals have to switch languages quite often — you may talk to
your father in one language and to your mother in another language,” says
Albert Costa, a researcher at the University of Pompeu Fabra in Spain. “It
requires keeping track of changes around you in the same way that we monitor
our surroundings when driving.” In a study comparing German-Italian bilinguals
with Italian monolinguals on monitoring tasks, Mr. Costa and his colleagues
found that the bilingual subjects not only performed better, but they also did
so with less activity in parts of the brain involved in monitoring, indicating
that they were more efficient at it.
The bilingual experience appears to
influence the brain from infancy to old age (and there is reason to believe
that it may also apply to those who learn a second language later in life).
In a 2009 study led by Agnes Kovacs of the International School for Advanced
Studies in Trieste, Italy, 7-month-old babies exposed to two languages from
birth were compared with peers raised with one language. In an initial set of
trials, the infants were presented with an audio cue and then shown a puppet on
one side of a screen. Both infant groups learned to look at that side of the
screen in anticipation of the puppet. But in a later set of trials, when the
puppet began appearing on the opposite side of the screen, the babies exposed
to a bilingual environment quickly learned to switch their anticipatory gaze in
the new direction while the other babies did not.
Bilingualism’s effects also extend into
the twilight years. In a recent study of 44 elderly Spanish-English bilinguals,
scientists led by the neuropsychologist Tamar Gollan of the University of
California, San Diego, found that individuals with a higher degree of
bilingualism — measured through a comparative evaluation of proficiency in each
language — were more resistant than others to the onset of dementia and other
symptoms of Alzheimer’s disease: the higher the degree of bilingualism, the
later the age of onset.
Nobody ever doubted the power of language.
But who would have imagined that the words we hear and the sentences we speak
might be leaving such a deep imprint?
Yudhijit Bhattacharjee is a staff writer
at Science.
This article has been revised to reflect
the following correction:
Correction: March 25, 2012
The Gray Matter column on bilingualism last Sunday
misspelled the name of a university in Spain. It is
Pompeu Fabra, not Pompea Fabra.
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