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Is There a Bilingual Advantage to Ward off Dementia? | As the Alzheimer's community heralds bilingual brains as mitigating dementia, some researchers suggest otherwise. By Ann Leslie Davis

Knowing another language is a lovely thing. It opens new worlds, helps you navigate them, and leads you, explorer-like, to new discoveries. You find words like zeitgeist, the spirit of the times, that are much catchier in another tongue. You uncover words for which no English equivalents exist — déjà vu, for instance, or schadenfreude, that guilty pleasure we take in someone else's misfortune. Languages expand our humanity by allowing us to see the world as others see it. "To speak another language," the Holy Roman emperor Charlemagne once observed, "is to have another soul."

But does bilinguality do something for our bodies as well as our spirits? Could a second language help make our brains more resilient to the effects of aging?

Eve Higby, Ph.D., assistant professor of neurolinguistics at Cal State East Bay, is one of a growing number of researchers to suggest it may. Their research supports the notion that the extra wiring necessary to house two sets of words, along with the mental control involved in choosing between them, may buffer the older brain and help delay the onset of dementia symptoms.

Understanding why our brains function as they do is notoriously difficult. Researchers have traditionally used stimulus-response tests as a measure of cognition (such as pushing different-colored buttons in response to words or images shown rapidly on a screen). But a 2017 study used PET scans to look inside the brains of monolingual and bilingual patients suffering from dementia. The study, conducted on 85 older adults in northern Italy, revealed that bilinguals had consistently higher levels of activity in brain areas involved in executive control. But the real surprise was the age difference of the subjects. All 85 people were at the same stage of dementia, according to the brain scans. But the bilinguals were an average of four years older. As Higby notes, this indicates not that bilingualism prevents Alzheimer's, but that the bilingual brain is able to function despite the presence of Alzheimer's.

"It suggests that they're able to compensate, that there's a protective mechanism that works for awhile," she said. "That's four more years of quality life for that person."

Higby's own research may help point to the reason why. If we think of neural pathways as roads, the monolingual brain only needs one road to reach a word — say apple. But in the bilingual brain, each road forks; one way leads to apple, the other to manzana. People who live in bilingual environments are constantly monitoring the scene for clues on which language to use, then adjusting — or "code-switching" — between the two.

This back-and-forth has traditionally been thought to cause mental confusion. But Higby's work, published this year, indicates that using a second language seems to provide "an indirect frequency boost." This boost appears to strengthen rather than blur connections to our mother tongue — something every senior needs when they're fumbling to name that red delicious something-or-other at the supermarket.

Higby first became interested in the subject of bilinguality while teaching English as a Second Language. She noticed that some of her students picked up the new language quickly, on first exposure, while others struggled. She wondered why, and how best to help slower learners. That curiosity led her to graduate school, and eventually a Ph.D. in neurolinguistics at the City University of New York.

"I wanted to find out how the brain learns a second language in adulthood," Higby said. "But I found out that we didn't know anything about it."

The theory of a bilingual advantage is already being heralded by some in the Alzheimer's community. But a group of researchers, including San Francisco State University professor Kenneth Paap, has provided strong pushback. They argue that the field suffers from problems in study methodology and a bias in professional journals toward publishing positive results.

According to Paap, the study showing a delay in dementia symptoms is "interesting, but puzzling."

He said that studies of bilinguals and cognitive ability tend to show different results depending on whether they're prospective or retrospective — whether they follow people over time or look back at patient histories. "[P]atients who show up at memory clinics do show a bilingual advantage some of the time, but in many of those instances, the comparison is 'confounded' because the group differences could be due to another variable." Size of study group also matters, Paap said. For some reason, smaller studies tend to show a bilingual advantage, while larger studies show none.

The debate has gotten testy at times. Higby supports vigorous dialogue, but hopes for civility in the search for truth. "Scientific debate is healthy when you have different findings and try to understand the source of those differences, rather than saying what's right and wrong."

But just in case you're wondering if you should run to the closet and dig out your old high school Spanish textbook, be aware that the age at which you learn a new language may influence its potential cognitive value. While benefits have been reported in both young and old bilinguals, Higby says, no evidence yet exists that a crash diet of foreign words will have the same effect as a lifetime's slow, steady accretion.

Then again, why not learn another language, no matter your age? If it doesn't boost your brain, it will certainly stretch your soul.

 


Bilingual capabilities may delay dementia onset. Photo by XiXinXing.