Multilingualism, The Brain, and Preventing Dementia

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We already know that learning another language has many benefits but perhaps one of the most fascinating of these benefits is the ability to have a healthier brain. We have long known that bilinguals show signs of dementia 3-5 years later than monolinguals even when they are both at the same stage of Alzheimer’s. This means that the average monolingual who develops Alzheimer’s will show cognitive impairment earlier than those who are bilingual. Furthermore, research has shown that countries where more than one language is spoken have 50% less cases of dementia. (Like, seriously, United States, when are we giving up our English-only stance?) Let’s look at why our brains prefer to be bi/multilingual.

Cognitive Reserve

Speaking more than one language increases cognitive reserve. Cognitive reserve is the brain’s ability to find alternate modes of functioning even when it encounters structural and physiological challenges. People with a large cognitive reserve can continue functioning asymptomatically for longer (or recover faster) even when they encounter impediments to normal brain function such as stress, trauma, and Alzheimer’s. Cognitive reserve occurs through a concept known as brain plasticity. Brain plasticity is the flexibility of the brain to change. The brain is made up of neurons that “wire” together. When the brain encounters experiences such as new learning and problem solving, it creates new connections between neurons. Sometimes, it even creates new neurons. As new connections are made, the brain becomes more “plastic,” and the brain builds cognitive reserve.

Cognitive reserve can be built up by learning new things and engaging your mind in challenging activities. Therefore, people who are highly educated or who have careers that require greater problem solving are likely to have more cognitive reserve. Greater degrees of socialization (at or outside of work) is also known for building cognitive growth because your brain has to constantly listen and process what the other person has to say and respond accordingly. And of course, multilingualism is one of the most powerful ways to build cognitive reserve.

Passive vs. Active Bilingualism

Not all bilingualism is equal in its ability to build cognitive reserve and delay dementia. According to Dr. Marco Calabria, a professor at the Universitat Oberta de Catalunya Faculty of Health Sciences, the impact of bilingualism depends on where the individual falls on the passive versus active bilingualism continuum. Absolute passive bilingualism is when the individual functions more like a monolingual but may hear another language often. Absolute active bilingualism is when the individual uses both their languages daily and can do so in any context. Most people who consider themselves bilingual fall somewhere between these two extremes. Dr. Calabria’s team found that the more active a person is in their bilingualism, the more they would delay the onset of dementia. The upshot? Knowing two languages is not enough. It is the active use of those languages that contributes to improving cognitive reserve.

How Bilingual Brains Function

That active bilingualism protects the brain more than passive bilingualism is not surprising when one understands how the bilingual brain functions. Bilinguals are always exercising the part of the brain responsible for executive function skills and therefore, strengthening these connections. Brain studies have shown that bilinguals constantly use all of their linguistic resources even when speaking in only one language. Therefore, they have to constantly work at managing these resources. For instance, when bilinguals speak to monolinguals, bilinguals must actively suppress the language that they are not using. Furthermore, bilinguals have to actively switch languages as soon as a new conversation begins with a monolingual who speaks a different language. These skills are executive function skills. On the other hand, passive bilinguals do not exercise their brains the same way.

Furthermore, passive bilinguals may actually be losing previously built cognitive reserve. Brain plasticity not only means that the brain can make new connections. It also means that it can destroy connections that no longer serve it well, a process known as synaptic pruning. Think about subjects you might have studied as a kid that are no longer relevant to your field or life activities. Whether these subjects are biology, math, history, or an entirely different subject, it is more than likely that you have forgotten much of it. This is because the brain, to be efficient, prunes these connections away. Therefore, one might posit that by no longer using a language once spoken, the brain is in a condition of losing rather than building cognitive reserve.

Multilingualism and Dementia

If bilingualism delays the onset of dementia, the power of multilingualism is even greater. Researchers from the University of Waterloo found that among nuns at Notre Dame, speaking four or more languages nearly eliminated the risk of developing dementia. This conclusion should hardly come as a surprise considering what we know about brain plasticity. If the part of the brain that controls executive function is constantly exercised and thus, strengthened for bilinguals when suppressing one language or switching between two, how much harder must the multilingual brain work when suppressing three languages or switching among four? This constant exercise must strengthen the connections and rewire the brain far beyond what happens for bilinguals, thus, building a larger cognitive reserve.


An added and fun brain benefit of multilingualism is the ability to enhance travel, a brain-boosting activity in itself. According to Dr. Nussbaum at the University of Pittsburgh, travel to new places “stimulates the brain” and thus, increases the creation of connections in the brain. This is due to a variety of reasons including having to problem solve when the inevitable glitches occur and having to encounter and learn new things. It also gives you the opportunity to socialize with new people and learn about new cultures and perspectives, activities that push the brain out of its comfort zone.

All of these brain-boosting opportunities are further enhanced when you speak the language of the place to where you are traveling. For instance, exploring on your own rather than with a tour guide gives you greater opportunities to problem solve; however, most travelers are more likely to forgo the tour guide when they speak the language than when they know that they will likely encounter language barriers. Furthermore, it is easier to engage in deep conversations when you speak the language. This depth in socialization allows you to really delve into perspectives of people of the new culture which in turn, stimulates the brain more deeply. Finally, when you travel abroad, you will oft use your language skills in ways that you are unable to at home, giving you all the benefits of exercising the part of the brain that controls executive function, as described earlier in this post. For instance, you may bargain more with storekeepers, a skill in itself that is rarely used in the United States. Hence, traveling to new places where you get to use your multilingualism helps build cognitive reserve and thus, at least, theoretically, delays the onset of dementia.

Learn those languages

Overall, the research demonstrates without a shadow of a doubt that to protect our brains, we need to learn and use as many languages as we can. Next week, we’ll talk about five specific ways we can use this research to build our own cognitive reserve.

  • Reviewed by Shantanu S. Kidambi, MD, University of Massachusetts


  1. […] It looks good on college applications.  And it helps develop the brain in a way that delays the symptoms of diseases such as Alzheimer’s.  However, for students who identify the Language Other Than English (LOTE) as a home language, […]


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