Do bilinguals have a cognitive advantage?


By Angela de Bruin (Staff Writer)


If we were to believe newspaper headlines, teaching your children to speak two languages would make them mini Einsteins – a so-called bilingual advantage. There are endless lists of press releases covering the idea of a bilingual advantage, of which, my favourites are: 

‘Why it’s smart to be bilingual’ [1],

‘Bilingual people are like brain bodybuilders’ [2], 

‘Being bilingual really does boost brain power’ [3], 

‘Bilingual brains are more healthy’ [4], and 

‘Why bilinguals are smarter’ [5].

These phrases seem to suggest that bilinguals are smarter and healthier than monolinguals. And although slightly exaggerated, they appear to be based on scientific evidence. But if we examine the evidence, is this actually true?

As a bilingual, you have to control two languages constantly. Speaking Dutch and English myself, I have to suppress Dutch words when I am speaking English and English words while using Dutch. Although this may sound effortful, for the most part bilinguals do not realise they are doing it. In some situations, bilinguals have the opportunity to use two languages at the same time, which requires them to switch between words in different languages. The hypothesis is that this daily practice of inhibiting and switching could lead to a bilingual advantage. Research suggests that bilinguals are faster than monolinguals when suppressing task-irrelevant information [6] or when asked to switch between two non-language based tasks [7]. The most popular described advantage, however, regards the onset of dementia – it has been argued that bilingualism delays the onset of dementia by approximately five years [8].

There are many studies suggesting that bilinguals have this cognitive advantage. And it all sounds like great news – at least, for those who speak more than one language. The problem, however, is that people tend to rely on studies published in academic journals. But why might this be problematic? Unfortunately, researchers do not publish every single study they conduct. Sometimes researchers feel it is best not to publish a study. Their design could have been flawed, or perhaps they did not quite test enough participants to draw scientifically sound conclusions. But in other cases researchers do not publish results purely because their data do not fit their story, or reviewers reject data which are unclear or inconsistent with dominant theories. This is called publication bias: Positive results are more likely to be submitted and published than studies with no effect or a negative effect. A publication bias is unfortunately something that affects many research fields including clinical research [9] and it can lead to a very biased representation of the actual effects of a phenomenon. 

In my research, we wanted to find out whether this publication bias also affects findings regarding the well-known idea of a bilingual advantage. During conferences, I noticed that a large number of posters presented results showing no effect of bilingualism, in other words, that there was no notable advantage to speaking two languages. When I looked at the literature, however, the vast majority of studies seemed to have found a bilingual advantage. I therefore decided to look at the matter more systematically. I searched for conference abstracts on the topic of bilingualism and executive control in 169 conferences and found 104 abstracts that met the criteria. Approximately half of the results showed a bilingual advantage; the other half showed no differences between bilinguals and monolinguals (and occasionally even a bilingual disadvantage). Then I checked which results had actually been published in a scientific journal. About half of the conference abstracts had made their way into an academic journal. But while 63% of the studies supporting a bilingual advantage had been published, only 36% of the results challenging this idea made it into a journal. Importantly, the different study types did not differ in the number of participants, the power to detect an effect, or the type of tasks that they used. The only difference appeared to be whether the results were consistent with a bilingual advantage or not [10]. 

Publication bias is highly problematic for the interpretation of data in any field. If we only read about studies which show a positive effect, we are - of course - very likely to conclude that such a positive effect is representative of reality. What we don’t know is how many unpublished studies failed to show this effect. In the case of bilingualism, this problem not only affects the scientific community, but also the wider, public community. As demonstrated by the headlines discussed above, the idea of a bilingual advantage is extremely popular and presented as common wisdom. It is often used as a ‘bonus’ to encourage people to study a second language or as an argument to convince parents to send their children to a school that teaches them another language. 

Now, I absolutely do not want to argue against a bilingualism advantage. It is an advantage by definition, because it allows you to move to new countries, to learn more about other cultures, and to communicate with more people. Over and above this, language learning is simply fun (or very frustrating at times). We also cannot say that there is no cognitive advantage to bilingualism, at all. After all, there are many available studies which suggest that bilingualism may have such a positive impact. But the pendulum has swung too far. About seventy years ago, there was a very strong belief that bilingualism was harmful. Parents were discouraged from teaching their children a second language, as they were told it would damage their brains [11]. Now the pendulum has swung too far in the opposite direction because bilingual advantages are described as clear and accepted. Whilst this may appear to be the case in published literature, we cannot forget the plethora of drawers filled with unpublished materials. Researchers should aim to publish all studies of good quality rather than selecting only those data that fit their story and journals should aid them in this pursuit. Only by addressing apparent publication bias’ can we truly learn about the exact nature of a phenomenon. At the same time, we should remain critical when we read about scientific results. The story is usually far more complicated than just yes or no.  


Angela de Bruin is presently pursuing a Ph.D. in Psychology at the University of Edinburgh.


If you enjoyed this article and want to read more about the uncertainty of science, check out Chris Crockford’s blog post here 

[1] Schwartz, C. (2011, August 7). Why it’s smart to be bilingual. Newsweek. Retrieved from:

[2] Lewis, T. (2014, November 12). Bilingual people are like brain ‘bodybuilders’. Livescience. Retrieved from:

[3] Zolfagharifard, E. (2015, January 13). Being bilingual really does boost brain power: Learning a language after 10 years of age changed the mind’s ‘white matter’. Daily Mail. Retrieved from:

[4] Fox, K. (2011, June 12). Ellen Bialystok: Bilingual brains are more healthy. The Guardian. Retrieved from

[5] Bhattacharjee, Y. (2012, March 17). Why bilinguals are smarter. The New York Times. Retrieved from

[6] Bialystok, E., Craik, F. I., Klein, R., & Viswanathan, M. (2004). Bilingualism, aging, and cognitive control: evidence from the Simon task. Psychology and aging, 19(2), 290-303.

[7] Prior, A., & MacWhinney, B. (2010). A bilingual advantage in task switching. Bilingualism: Language and Cognition, 13(02), 253-262.

[8] Bialystok, E., Craik, F. I., & Freedman, M. (2007). Bilingualism as a protection against the onset of symptoms of dementia. Neuropsychologia, 45(2), 459-464.

[9] Easterbrook, P. J., Gopalan, R., Berlin, J. A., & Matthews, D. R. (1991). Publication bias in clinical research. The Lancet, 337(8746), 867-872.

[10] de Bruin, A., Treccani, B., & Della Sala, S. (2015). Cognitive Advantage in Bilingualism An Example of Publication Bias?. Psychological Science, 26(1), 99-107.

[11] Peal, E., & Lambert, W. E. (1962). The relation of bilingualism to intelligence. Psychological Monographs: general and applied, 76(27), 1-23.