The Plastic Revolution

Ideas Roadshow
6 min readDec 9, 2021


A long-running debate in the linguistics community is centered around something called the Sapir-Whorf hypothesis, after Edward Sapir and his erstwhile student Benjamin Lee Whorf, two famous linguists who first formulated it most explicitly in the first half of the 20th century. Loosely put, the question is whether we experience the world around us through whichever language we happen to speak (as Sapir and Whorf believed), or if our mental “world views” are fundamentally language-independent.

In other words, does language shape our thoughts? Or do our thoughts — the product of some underlying cognitive processes common to all — shape our language?

As the battle raged on, Ellen Bialystok, Distinguished Research Professor of Psychology at York University and Associate Scientist at the Rotman Research Institute, has neatly sidestepped the issue by looking at something slightly different. Ellen is one of the world’s most foremost authorities on the measurable effects of bilingualism on our brains: what objective differences, on average, can be detected between those who speak two languages, as opposed to just one?

Somewhat surprisingly, perhaps, it turns out that there are a good deal more differences than we might, at first, have suspected.

The first major distinction that Ellen appreciated concerned something called “metalinguistic awareness”.

“The most important linguistic achievement for young kids is developing what is called metalinguistic awareness: knowledge about language, understanding what language is and that it can be manipulated. If you don’t understand that language is a structured system, you can’t learn to read, because you can’t figure out that the things on the page refer to something in language. So metalinguistic awareness is crucial.

“In the first studies that started in the late 1970s and continued for about a decade, a number of people, including my own group, were looking at the development of metalinguistic awareness and finding that, by and large, bilingual children are ahead. The bilingual kids were developing these metalinguistic insights up to a year earlier.”

Bilingual children, then, through their experience of regularly manipulating two languages from a very early age, develop a faster appreciation of the structure of language itself.

Well, that’s interesting, but perhaps not very surprising. And anyway, does it really matter? After all, just because bilinguals get there faster doesn’t necessarily mean all that much if we all get there eventually.

But then Ellen started noticing other things. It seems that, on average, bilinguals — both children and adults — performed decidedly better on standardized tests involving a large amount “cognitive interference”, when the subject was deliberately subjected to misleading information. These tests can be verbal (like the famous Stroop test, where subjects are asked to identify words like “green” based on the colour of their ink, which is typically changed to a range of different colours) or non-verbal (such as measuring reaction times of dots on different sides of a screen with different hands).

This was progress, then, of a sort: it seemed the bilingual brain really is, objectively, at least a bit different than the monolingual brain. The problem, though, was to determine if this scientifically demonstrated difference was any more societally relevant than simply being able to do better on a few arcane and largely irrelevant psychological tests.

So Ellen and her colleagues starting imagining how these differences might be more generally manifested in the real world. After all, if bilinguals were somehow able to, on average, insulate themselves against misleading or extraneous information, then surely we should be able to see evidence of this in other places than simply the Stroop test.

And yes, indeed, that turns out to be the case. Through a number of cleverly-designed experiments, it was discovered that bilinguals, on average, performed objectively better at a series of diverse tasks — from driving while on a cell phone, to cooking many items simultaneously — all of which involved an ability to successfully multitask, simultaneously filtering in and out different streams of information.

But that was only the beginning. Ellen, who began her scientific career as a developmental psychologist studying language acquisition in young children, then began looking to see if the effects of lifelong bilingualism might somehow manifest themselves in the elderly, specifically examining those who suffered from dementia.

In a series of groundbreaking studies, Ellen and her group demonstrated that the first signs of dementia are typically delayed a whopping 4–5 years for bilinguals compared to monolinguals. Bilingualism is no cure for dementia, it needs to be stressed, but somehow the bilingual brain is able to significantly delay the impact of severely debilitating diseases like Alzheimer’s. Follow-up research using fMRI brain-scanning technology revealed that bilingual brains tend to have a slightly different neurophysiology — more grey matter and white matter — than their monolingual counterparts.

Talk about hugely relevant research. We are, suddenly, a very long way indeed from measuring differences in reading words in different coloured ink.

And yet, puzzles abound. What, for example, is happening in the brains of bilingual people that enable them to more successfully battle against the ravages of Alzheimer’s disease?

Ellen believes the answer lies in a specific region of our brain called the prefrontal lobes. Modern brain scans have shown evidence that bilinguals have a better prefrontal lobe network that, in turn, directly enables higher levels of executive control. And it is this boost in executive control that allows them to mask the effects of dementia better than monolinguals.

“The theory, yet to be confirmed, is that because the front part of the brain, this important area where we find this set of executive processes, is more efficient for bilinguals, it’s better suited to provide compensation. The front part of the brain is kind of domain-general; it’s not used for just one thing. In other words, having a robust front part of the brain can somehow carry you through as deterioration is happening elsewhere. It comes in as a kind of reserve.”

That sounds plausible enough. But how did these enhanced networks get developed in the first place? How can the very act of speaking two languages change the very structure of our brains?

“What we now understand about the brain is that it is massively plastic. The brain is not a fixed framework of rigid connections, but is a dynamic, plastic system. It molds itself on the basis of what you’re asking it to do, and the more you train your brain, or require your brain to do certain kinds of things, the more it will reroute your neural circuitry to reflect those experiences, which means that the brain is a strong reflection of your experiences.

“If you think about it that way, it’s not so surprising that something as pervasive as the language, or languages, that you speak is going to rewire your brain. People are surprised that bilingualism rewires the brain. They think it’s crazy. But it isn’t crazy at all. Everything rewires the brain.”

And suddenly, from a rather unforeseen direction, a bright light shines on our old conundrum of whether language shapes our thoughts or thoughts shape our language.

The solution, neuroplasticity tells us, is quite simply yes to both.

Howard Burton

This is the introduction of the book The Psychology of Bilingualism, which has been developed from an in-depth conversation with Ellen Bialystok, Professor of Psychology at York University, and a world-leading expert on the effects of bilingualism on cognitive processes across our lifespan.

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