People who speak two languages may have brains that are more efficient at language processing and other tasks, new research suggests.

Scientists have long assumed that the “bilingualism advantage” — the enhanced ability to filter out important information from unimportant material — stems from how bilingual people process language. The new study confirms that assumption and goes on to suggest that bilingual people are more efficient at higher-level brain functions such as ignoring irrelevant information, said Ellen Bialystok, a psychologist at York University in Toronto, who was not involved in the research.

Working harder

In the study, published last week in the journal Brain and Language, brain scans showed that people who spoke only one language had to work harder to focus on a single word.

People who are bilingual are constantly activating both languages in their brain, choosing which to use and which to ignore, said the study’s leader, Viorica Marian, a linguistic psychologist at Northwestern University.

Compared with people who speak only a single tongue, “bilinguals are much better at ignoring irrelevant words,” Marian said.

Brain bodybuilders

In previous studies of people’s eye movements, Marian and her colleagues found that when bilingual people heard a word in one language, they often looked at objects whose names sounded similar to that word in their second language. In the new study, the researchers looked at how the ability to filter information manifests itself in the brain.

The researchers used functional magnetic resonance imaging (fMRI) to scan the brains of 17 people who were fluent in both Spanish and English and 18 who spoke only English.

During the experiment, volunteers heard the name of an object and simultaneously were shown a picture of that object, as well as an object with a similar-sounding name, and two unrelated objects. For example, they might hear the word “cloud” and see pictures of a cloud, a clown and two other things. As fast as they could, the volunteers had to pick the picture that showed the word they heard.

Bilingual people were no faster at performing the task than monolinguals. However, their brain activity was markedly different, the scans revealed.

The brains of people who spoke only one language lit up much more than those of their bilingual counterparts in regions involved in controlling higher-level functions, including suppressing competing word meanings. In other words, monolinguals’ brains had to work much harder to perform the task, the researchers said.

The researchers compared the task with lifting weights at a gym. “The bilingual has to lift more weight than the monolingual, because bilinguals experience competition within and between both their languages while listening to speech,” the researchers said in an e-mail. “But the bilingual is also stronger, because they’ve been mentally ‘working out’ like this for their whole life.”

Bilingual benefits

Other scientists praised the research team for its approach to studying the brain activity of bilingual people. “This study fills in one of the important missing pieces in our understanding of how bilingualism leads to cognitive benefits,” Bialystok said.

Most of the previous research on the benefits of bilingualism has focused solely on behavior, which has drawn criticism from some scientists.

“There is actually a big discussion about whether the bilingual advantage exists or not,” said Jubin Abutalebi, a cognitive neurologist at the University San Raffaele in Milan, Italy.

The new study added to the field by showing that the task of filtering information activates different brain areas in bilinguals and monolinguals, Abutalebi said.

Knowing multiple languages may have other benefits, too. In a previous study, Marian and her colleagues found that bilingual children were able to ignore classroom noise more easily than monolingual children.

Some research suggests that being bilingual may also help stave off Alzheimer’s disease and dementia for a few years by keeping the brain nimble and increasing the amount of gray matter, though other studies have had conflicting results. More research on that issue is needed, according to the Mayo Clinic.

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