The First Shift: One to Two
The moment you stop being monolingual, something structural changes in the brain.
Managing two languages requires constantly suppressing the one not in use, exercising the same neural systems responsible for attention, task-switching, and filtering distraction. Research consistently shows bilinguals develop stronger executive function: better working memory, faster task-switching, and greater focus under pressure [1]. Most publications in this field support a delay in clinical dementia symptoms of four to five years in bilinguals compared to monolinguals [2][3].
But the more interesting finding is not cognitive. Bilinguals do not just think differently. They feel differently depending on which language they are in. Research on bilingual personality found that the same individuals rate themselves differently on personality measures depending on which language they are using [4]. The language you are in is not just a vehicle for thought. It is a partial architecture of self.
Two languages gives you two slightly different versions of yourself, and the machinery to move between them. Which raises the question: what happens when you add a third?
The Second Shift: Two to Three and Beyond
Trilinguals show strong performance on inhibitory control tasks, sometimes exceeding bilinguals [5]. A comparison of Filipino-English bilinguals and Chinese-Filipino-English trilinguals found trilinguals outperformed bilinguals on attention tasks requiring suppression of competing information [5].
But some studies complicate the picture. Research in the International Journal of Multilingualism found an overall bilingual and trilingual disadvantage on certain working memory tasks compared to monolinguals [6]. The brain is doing more work. That is both the advantage and the cost.
The most significant threshold, it turns out, is not two or three but five.
The Five-Language Threshold
A 2024 MIT and Harvard study using precision fMRI examined 34 polyglots, individuals who speak five or more languages, including 16 hyperpolyglots who speak ten or more [7]. It found that familiar languages activated stronger responses in the language network than unfamiliar ones, but native languages provoked the least activation of all [8]. Not because the native language is less important. Because it is so deeply encoded the brain processes it with least effort. It has become automatic. Every subsequent language sits in various stages of that journey.
The polyglot brain does not accumulate languages as separate compartments. It integrates them. The language network becomes more efficient, not more crowded. Each new language, above a threshold of proficiency, uses the same underlying infrastructure rather than building parallel systems [7].
In parts of Africa and India, speaking four or five languages is not exceptional. It is circumstantial. Growing up at the intersection of a mother tongue, a regional language, a national language, and a colonial one produces multilingualism as environment. The research confirms the same cognitive benefits apply without deliberate effort [7].
And this is where the love angle gets genuinely strange.
The Language You Say "I Love You" In
Linguist Jean-Marc Dewaele spent years studying emotional processing in bilinguals and found something that reframes intimacy: people express emotions more intensely and authentically in their first language than in any learned later [11]. The phrase "I love you" in English might feel comfortable. But the same words in your mother tongue carry entirely different neural weight.
This is not sentiment. Emotional words learned in childhood are encoded differently from those learned later, processed deeper in the brain's emotional architecture. When you express love in a second language, you are working with less emotionally loaded material, producing the strange experience of feeling fluent and slightly distant from what you are actually saying.
Research on multilingual couples found that partners code-switch in ways they often do not consciously register [12]. One partner slips into their mother tongue when expressing anger. The other switches to a shared second language to smooth things over. Almost half of multilingual couples reported difficulty expressing romantic feelings in a non-native language at the start of a relationship, though most overcame it within months [13].
What the code-switching encodes is telling. Multilingual couples use their native language for emotional depth, vulnerability, and declarations. The shared language handles logistics and negotiation. Language choice is not arbitrary. It is emotional positioning, a signal of how much of yourself you are bringing to the moment.
Which means when someone who speaks four languages tells you something in their mother tongue, they are not just choosing words. They are stepping out of every version of themselves the other languages permit and into the one that formed first.
That is worth paying attention to.
The Honest Caveat
Not all of this is settled. A significant number of studies find no executive function difference between bilinguals and monolinguals, and the debate about how large and replicable the effect is continues [6]. The dementia delay data is epidemiologically consistent but mechanistically unresolved [3].
What is not contested is the structural evidence. Grey matter density increases in language-processing regions with multilingual experience [1]. The brain physically changes. Whether every cognitive task improves depends on the individual, the languages, and the frequency of switching. The effect accrues to those who actively use multiple languages, not those who technically know them.
A Note From Me
If you stayed with this one, thank you.
I grew up switching between languages without thinking about it. I never considered that the switching itself was doing something. That managing two grammars simultaneously was also a kind of training, and that the language I reach for in an unguarded moment says something true about where I actually live.
Reading the research changed how I think about something I had always taken for granted.
Find me here:
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See you in the next one.
Saral
References
Marian, V. & Shook, A. The Cognitive Benefits of Being Bilingual. Cerebrum, Dana Foundation, 2012. researchgate.net
Venugopal, R. et al. Protective Effect of Bilingualism on Aging, MCI, and Dementia: A Community-Based Study. Alzheimer's & Dementia, April 2024. alz-journals.onlinelibrary.wiley.com
Mendez, M.F. Can Speaking More Than One Language Help Prevent Alzheimer's Disease? Journal of Alzheimer's Disease, 2023. journals.sagepub.com
Eriksson, M. et al. The Effect of Language and Cultural Context on the Big-5 Personality Inventory in Bilinguals. Journal of Multilingual and Multicultural Development, 2023. tandfonline.com
Poarch, G.J. et al. The Cognitive Benefits of Speaking Multiple Languages. CARI Journals, Vol. 3, Issue 4, 2024. researchgate.net
Antoniou, M. et al. Does the Bilingual Advantage Extend to Trilingualism? International Journal of Multilingualism, Vol. 16, No. 4, 2019. tandfonline.com
Malik-Moraleda, S. et al. Functional Characterization of the Language Network of Polyglots and Hyperpolyglots with Precision fMRI. Cerebral Cortex, Vol. 34, No. 3, 2024. pubmed.ncbi.nlm.nih.gov
Fedorenko, E. & Malik-Moraleda, S. Your Native Tongue Holds a Special Place in Your Brain. Science/AAAS, February 2023. science.org
Wen, Z. et al. Do Polyglots Have Exceptional Language Aptitudes? Language Teaching Research Quarterly, Vol. 31, 2022. files.eric.ed.gov
Keysar, B., Hayakawa, S.L. & An, S.G. The Foreign-Language Effect: Thinking in a Foreign Tongue Reduces Decision Biases. Psychological Science, Vol. 23, No. 6, 2012.
Dewaele, J.M. Emotions in Multiple Languages. Palgrave Macmillan, 2010. Referenced in: Multilingual Relationships: How Language Shapes Love. FluentCap Blog, February 2026. fluentcap.live
Harvey, J. Baby, Te Amo: Code Switching in Multilingual Romantic Relationships. Journal of Undergraduate Ethnography, Vol. 3, Issue 2, 2013. ojs.library.dal.ca
Dewaele, J.M. Loving a Partner in a Foreign Language. Journal of Pragmatics, Vol. 108, 2017. sciencedirect.com
