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The Cognitive Benefits of Being Bilingual
By Viorica Marian, Ph.D., and Anthony Shook
Editor’s note: Today, more of the world’s population is bilingual or multilingual than
monolingual. In addition to facilitating cross-cultural communication, this trend also positively
affects cognitive abilities. Researchers have shown that the bilingual brain can have better
attention and task-switching capacities than the monolingual brain, thanks to its developed
ability to inhibit one language while using another. In addition, bilingualism has positive effects
at both ends of the age spectrum: Bilingual children as young as seven months can better adjust
to environmental changes, while bilingual seniors can experience less cognitive decline.
We are surrounded by language during nearly every waking moment of our lives. We use
language to communicate our thoughts and feelings, to connect with others and identify with our
culture, and to understand the world around us. And for many people, this rich linguistic
environment involves not just one language but two or more. In fact, the majority of the world’s
population is bilingual or multilingual. In a survey conducted by the European Commission in
2006, 56 percent of respondents reported being able to speak in a language other than their
mother tongue. In many countries that percentage is even higher—for instance, 99 percent of
Luxembourgers and 95 percent of Latvians speak more than one language.1 Even in the United
States, which is widely considered to be monolingual, one-fifth of those over the age of five
reported speaking a language other than English at home in 2007, an increase of 140 percent
since 1980.2 Millions of Americans use a language other than English in their everyday lives
outside of the home, when they are at work or in the classroom. Europe and the United States are
not alone, either. The Associated Press reports that up to 66 percent of the world’s children are
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raised bilingual.3 Over the past few decades, technological advances have allowed researchers to
peer deeper into the brain to investigate how bilingualism interacts with and changes the
cognitive and neurological systems.
Cognitive Consequences of Bilingualism
Research has overwhelmingly shown that when a bilingual person uses one language, the
other is active at the same time. When a person hears a word, he or she doesn’t hear the entire
word all at once: the sounds arrive in sequential order. Long before the word is finished, the
brain’s language system begins to guess what that word might be by activating lots of words that
match the signal. If you hear “can,” you will likely activate words like “candy” and “candle” as
well, at least during the earlier stages of word recognition. For bilingual people, this activation is
not limited to a single language; auditory input activates corresponding words regardless of the
language to which they belong.4
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Some of the most compelling evidence for language co-activation comes from studying
eye movements. We tend to look at things that we are thinking, talking, or hearing about.5 A
Russian-English bilingual person asked to “pick up a marker” from a set of objects would look
more at a stamp than someone who doesn’t know Russian, because the Russian word for
“stamp,” “marka,” sounds like the English word he or she heard, “marker.”4 In cases like this,
language co-activation occurs because what the listener hears could map onto words in either
language. Furthermore, language co-activation is so automatic that people consider words in both
languages even without overt similarity. For example, when Chinese-English bilingual people
judge how alike two English words are in meaning, their brain responses are affected by whether
or not the Chinese translations of those words are written similarly.6 Even though the task does
not require the bilingual people to engage their Chinese, they do so anyway.
Having to deal with this persistent linguistic competition can result in language
difficulties. For instance, knowing more than one language can cause speakers to name pictures
more slowly7 and can increase tip-of-the-tongue states (where you’re unable to fully conjure a
word, but can remember specific details about it, like what letter it starts with).8 As a result, the
constant juggling of two languages creates a need to control how much a person accesses a
language at any given time. From a communicative standpoint, this is an important skill—
understanding a message in one language can be difficult if your other language always
interferes. Likewise, if a bilingual person frequently switches between languages when speaking,
it can confuse the listener, especially if that listener knows only one of the speaker’s languages.
To maintain the relative balance between two languages, the bilingual brain relies on
executive functions, a regulatory system of general cognitive abilities that includes processes
such as attention and inhibition. Because both of a bilingual person’s language systems are
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always active and competing, that person uses these control mechanisms every time she or he
speaks or listens. This constant practice strengthens the control mechanisms and changes the
associated brain regions.9-12
Bilingual people often perform better on tasks that require conflict management. In the
classic Stroop task, people see a word and are asked to name the color of the word’s font. When
the color and the word match (i.e., the word “red” printed in red), people correctly name the
color more quickly than when the color and the word don’t match (i.e., the word “red” printed in
blue). This occurs because the word itself (“red”) and its font color (blue) conflict. The cognitive
system must employ additional resources to ignore the irrelevant word and focus on the relevant
color. The ability to ignore competing perceptual information and focus on the relevant aspects
of the input is called inhibitory control. Bilingual people often perform better than monolingual
people at tasks that tap into inhibitory control ability. Bilingual people are also better than
monolingual people at switching between two tasks; for example, when bilinguals have to switch
from categorizing objects by color (red or green) to categorizing them by shape (circle or
triangle), they do so more rapidly than monolingual people,13 reflecting better cognitive control
when changing strategies on the fly.
Changes in Neurological Processing and Structure
Studies suggest that bilingual advantages in executive function are not limited to the
brain’s language networks.9 Researchers have used brain imaging techniques like functional
magnetic resonance imaging (fMRI) to investigate which brain regions are active when bilingual
people perform tasks in which they are forced to alternate between their two languages. For
instance, when bilingual people have to switch between naming pictures in Spanish and naming
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them in English, they show increased activation in the dorsolateral prefrontal cortex (DLPFC), a
brain region associated with cognitive skills like attention and inhibition.14 Along with the
DLPFC, language switching has been found to involve such structures as the anterior cingulate
cortex (ACC), bilateral supermarginal gyri, and left inferior frontal gyrus (left-IFG), regions that
are also involved in cognitive control.9 The left-IFG in particular, often considered the language
production center of the brain, appears to be involved in both linguistic15 and non-linguistic
cognitive control.16
The neurological roots of the bilingual advantage extend to subcortical brain areas more
traditionally associated with sensory processing. When monolingual and bilingual adolescents
listen to simple speech sounds (e.g., the syllable “da”) without any intervening background
noise, they show highly similar brain stem responses to the auditory information. When
researchers play the same sound to both groups in the presence of background noise, the
bilingual listeners’ neural
response is considerably larger,
reflecting better encoding of
the sound’s fundamental
frequency,17 a feature of sound
closely related to pitch
perception. To put it another
way, in bilingual people, blood
flow (a marker for neuronal activity) is greater in the brain stem in response to the sound.
Intriguingly, this boost in sound encoding appears to be related to advantages in auditory
attention. The cognitive control required to manage multiple languages appears to have broad
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effects on neurological function, fine-tuning both cognitive control mechanisms and sensory
processes.
Beyond differences in neuronal activation, bilingualism seems to affect the brain’s
structure as well. Higher proficiency in a second language, as well as earlier acquisition of that
language, correlates with higher gray matter volume in the left inferior parietal cortex.18
Researchers have associated damage to this area with uncontrolled language switching,19
suggesting that it may play an important role in managing the balance between two languages.
Likewise, researchers have found white matter volume changes in bilingual children20 and older
adults.21 It appears that bilingual experience not only changes the way neurological structures
process information, but also may alter the neurological structures themselves.
Improvements in Learning
Being bilingual can have tangible practical benefits. The improvements in cognitive and
sensory processing driven by bilingual experience may help a bilingual person to better process
information in the environment, leading to a clearer signal for learning. This kind of improved
attention to detail may help explain why bilingual adults learn a third language better than
monolingual adults learn a second language.22 The bilingual language-learning advantage may be
rooted in the ability to focus on information about the new language while reducing interference
from the languages they already know.23 This ability would allow bilingual people to more easily
access newly learned words, leading to larger gains in vocabulary than those experienced by
monolingual people who aren’t as skilled at inhibiting competing information.
Furthermore, the benefits associated with bilingual experience seem to start quite early—
researchers have shown bilingualism to positively influence attention and conflict management
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in infants as young as seven months. In one study, researchers taught babies growing up in
monolingual or bilingual homes that when they heard a tinkling sound, a puppet appeared on one
side of a screen. Halfway through the study, the puppet began appearing on the opposite side of
the screen. In order to get a reward, the infants had to adjust the rule they’d learned; only the
bilingual babies were able to successfully learn the new rule.24 This suggests that even for very
young children, navigating a multilingual environment imparts advantages that transfer beyond
language.
Protecting Against Age-Related Decline
The cognitive and neurological benefits of bilingualism also extend into older adulthood.
Bilingualism appears to provide a means of fending off a natural decline of cognitive function
and maintaining what is called “cognitive reserve.”9, 25 Cognitive reserve refers to the efficient
utilization of brain networks to enhance brain function during aging. Bilingual experience may
contribute to this reserve by keeping the cognitive mechanisms sharp and helping to recruit
alternate brain networks to compensate for those that become damaged during aging. Older
bilingual people enjoy improved memory26 and executive control9 relative to older monolingual
people, which can lead to real-world health benefits.
In addition to staving off the decline that often comes with aging, bilingualism can also
protect against illnesses that hasten this decline, like Alzheimer’s disease. In a study of more
than 200 bilingual and monolingual patients with Alzheimer’s disease, bilingual patients reported
showing initial symptoms of the disease at about 77.7 years of age—5.1 years later than the
monolingual average of 72.6. Likewise, bilingual patients were diagnosed 4.3 years later than the
monolingual patients (80.8 years of age and 76.5 years of age, respectively).25 In a follow-up
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study, researchers compared the brains of bilingual and monolingual patients matched on the
severity of Alzheimer’s symptoms. Surprisingly, the brains of bilingual people showed a
significantly higher degree of physical atrophy in regions commonly associated with
Alzheimer’s disease.27 In other words, the bilingual people had more physical signs of disease
than their monolingual counterparts, yet performed on par behaviorally, even though their degree
of brain atrophy suggested that their symptoms should be much worse. If the brain is an engine,
bilingualism may help to improve its mileage, allowing it to go farther on the same amount of
fuel.
Conclusion
The cognitive and neurological benefits of bilingualism extend from early childhood to
old age as the brain more efficiently processes information and staves off cognitive decline.
What’s more, the attention and aging benefits discussed above aren’t exclusive to people who
were raised bilingual; they are also seen in people who learn a second language later in life.25, 28
The enriched cognitive control that comes along with bilingual experience represents just one of
the advantages that bilingual people enjoy. Despite certain linguistic limitations that have been
observed in bilinguals (e.g., increased naming difficulty7), bilingualism has been associated with
improved metalinguistic awareness (the ability to recognize language as a system that can be
manipulated and explored), as well as with better memory, visual-spatial skills, and even
creativity.29 Furthermore, beyond these cognitive and neurological advantages, there are also
valuable social benefits that come from being bilingual, among them the ability to explore a
culture through its native tongue or talk to someone with whom you might otherwise never be
able to communicate. The cognitive, neural, and social advantages observed in bilingual people
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highlight the need to consider how bilingualism shapes the activity and the architecture of the
brain, and ultimately how language is represented in the human mind, especially since the
majority of speakers in the world experience life through more than one language.
Viorica Marian, Ph.D., is chair of the department of
communication sciences and disorders at Northwestern
University and associate professor of communication
sciences and disorders, psychology, and cognitive
science. Dr. Marian received a Ph.D. from Cornell
University and a master’s degree from Emory
University. Her research focuses on
bilingualism/multilingualism and the brain's ability to
accommodate multiple languages at the same time, with
a specific emphasis on language processing, language
and memory, and language learning. Dr. Marian directs the Bilingualism and Psycholinguistics
Laboratory and uses cognitive, behavioral, and neurological measures to study human language
capacity and the consequences of bilingualism for linguistic, cognitive, and neural function.
Anthony Shook is a doctoral candidate in the department of
communication sciences and disorders at Northwestern
University. His research investigates bilingualism and what
it can reveal about language, with a focus on how two or
more languages interact at multiple levels of processing and
the effect of this interaction on the language system. Mr.
Shook uses behavioral and neurological methods, as well as
computational modeling, to explore the form and
architecture of the bilingual language comprehension
system.
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