I was almost envious the first time I sat across from a child who could switch between three languages in the middle of a sentence. She was five years old. She was patiently explaining to her grandmother in Urdu why the cartoon character on her t-shirt was, in French, “very tired today.”
Her hair was still wet from the pool. Then she turned to face me and asked if I wanted juice in English. When a child surpasses you intellectually before she can tie her shoes, it’s difficult to ignore it.
| Field | Detail |
|---|---|
| Lead Researcher | Ellen Bialystok, cognitive psychologist at York University |
| Institution | York University, Toronto, Canada |
| Other Key Researcher | Cathy Price, neuroimaging scientist at University College London |
| Brain Region of Interest | Posterior supramarginal gyrus (left hemisphere) |
| Key Finding | Increased gray-matter density in bilinguals |
| Reported Cognitive Benefit | Up to a four-year delay in onset of dementia symptoms |
| U.S. Bilingual Population | About 21% speak a language other than English at home |
| Most Pronounced Effect In | People fluent before age five |
| Source of Census Data | U.S. Census Bureau language survey |
| Field of Study | Neurobiology of bilingualism, executive function, brain plasticity |
My search for Ellen Bialystok, who has spent decades at York University attempting to comprehend what goes on inside brains like hers, began at that moment. Bialystok is cautious—almost obstinately so—about the assertions she will make. She maintains that bilingual children are not more intelligent. However, those who were raised in a multilingual environment do seem to have sharper cognitive processes—the ones hidden within what we refer to as intelligence. Speaking with her gives me the impression that she has been fighting for years against headlines that either completely ignore or exaggerate her work.
The conventional wisdom was pessimistic for the majority of the twentieth century. Teachers thought that teaching a child two languages would confuse them, slow them down, and possibly harm them. Up until the 1960s, when researchers started observing the opposite, that opinion persisted. It turns out that young brains are much more malleable than previous behavioral research indicated. A child’s mind is not overloaded by bilingualism. It changes its shape.

Working out of University College London, Cathy Price has scanned hundreds of these altered brains. Her team concentrated on the posterior supramarginal gyrus, a part of the left side of the brain that appears to be involved in vocabulary acquisition. The bilingual brains in her pictures are denser, more developed, and have more gray matter, especially in those who acquired their second language before the age of five. You can see the thickening. It is visible from three perspectives and appears on the scan as a tiny, obstinate flame that glows yellow.
Practically speaking, it is more difficult to determine what this means. Preschoolers who are bilingual are more likely than their monolingual peers to concentrate better and ignore distractions. Bilingual adults, particularly early learners, exhibit the same benefit. According to some researchers, the brain’s executive control system is trained similarly to how running trains the legs when two languages are continuously managed, with one language being chosen and the other suppressed. Some are more circumspect. They claim that while the effect is real, it is messier than the headlines portray.
The most startling and hotly debated assertion is that bilingualism can postpone dementia by up to four years. No one knows for sure why. Increased blood flow and stronger nerve connections—the kind of biological housekeeping that appears to prevent cognitive decline—are suggested by one theory. A lifetime of language juggling, according to another, creates a sort of cognitive reserve that protects against the gradual deteriorations of aging. Which mechanism, if any, is carrying out the heavy lifting is still unknown.
From the outside, all of this appears normal, which is strange. People who are bilingual don’t say they feel special. They are unaware of the increased working memory and thickened gyrus. They simply converse, switch, and translate—sometimes in the middle of their thoughts—often without even realizing it. The brain is subtly reorganizing itself somewhere beneath, creating something that the rest of us are still attempting to comprehend.
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