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What Is Different in the Bilingual Brain? Part II

The second part of an interview with Ping Li

Interview conducted by François Grosjean

A short while back, Dr. Ping Li, Professor of Psychology and Linguistics at Pennsylvania State University, answered a first series of questions on the bilingual brain (see here). We can now continue the interview, and are grateful to him for the time he has devoted to our questions.

Could we go back to the bilingual experience and the impact it has on neuroplasticity, that is how it can lead to functional and physical changes in the brain?

Yes, another unique aspect of how the bilingual experience impacts the brain is related to the fact that bilingual speakers often have to change the language they are using and have to monitor this, not to mention intertwining their languages in the form of code-switches and borrowings. These processes, it has been suggested, result in positive brain changes in the frontal and subcortical brain regions (due to inhibition of the unwanted language(s)) and in the anterior cingulate cortex (due to monitoring).

Although the specific brain mechanisms underlying these processes are still being debated, it is safe to say, given the available evidence from recent neuroimaging studies, that learning a new language and becoming a bilingual is a good choice for neuroplasticity, particularly in light of the uncertainties associated with the question of which type of cognitive experience is better for the brain.

It should be noted also that the language learning experience impacts many areas in the brain, in both the left and the right hemispheres–as we previously alluded to regarding how complex language is–whereas other types of cognitive experience (like juggling, doing jigsaw puzzles, etc.) may be beneficial to limited brain regions, such as the occipital cortex for vision, the motor cortex for movement, and the hippocampus for memory.

So what can be concluded concerning the bilingual experience?

It helps to shape the brain, even if such brain changes may not be revolutionary when evaluated against the grand spectrum of the evolution of the human brain (see Part 1 of the interview here). Such changes come about precisely because of the frequency, intensity, and duration of the bilingual experience. Scientific studies have shown that the extent of brain change is positively correlated with the level of proficiency gained in a second language.

Generally speaking, for all cognitive experiences–learning and using a language being one of them–the more often you perform the task, the more you will see brain changes; and the longer you work on it, the stronger will be the effects. Indeed, there has been work showing that if one stops learning a language or performing a cognitive task, the gained brain changes, such as increases in gray matter volume, will return to pre-learning or pre-training levels. So, “use it or lose it” and “no pain no gain” are all true when it comes to the positive effects of neuroplasticity.

Since there are many types of bilinguals, do some bilinguals resemble monolinguals in neural structures and/or connections whilst others are very different? If so, what factors are behind this?

This is a hugely important issue at the core of psychology: how do we identify the factors underlying individual differences in the learning and representation of knowledge? This question is also related to my earlier point that we cannot categorically describe ‘the bilingual brain’ versus ‘the monolingual brain’: rather, there is a continuum from being monolingual to being bilingual.

As you yourself have pointed out elsewhere, bilinguals use their two languages to a different extent, in different contexts, for different purposes, and with different people (see here). Underlying these volatile experiences of bilingualism are the different behavioral and brain patterns, such as which area of the brain becomes activated and which areas are better connected with one another. The many different shades of the term ‘bilingualism’ also make it exceedingly difficult to find two bilinguals who are exactly the same in every aspect of their language history or behavior. We may also need better tools and methods to study individual differences in bilingual learning and representations.

Can you be a bit more specific as concerns your own area of expertise?

I can see at least three dimensions along which we identify individual differences when we compare bilingual and monolingual brains. The most obvious factor is the age at which a second language is learned. If you learn a new language late in your life, your brain patterns are more likely to be similar to a monolingual’s in your native language, whereas they will be more different from those of native speakers of your second language. Work from my lab and that of many others has demonstrated this, and a great deal of theoretical thinking has gone into this in the past (see here).

There are also the linguistic features of languages that differ vastly from one another (phonology, orthography, syntax, etc.), and researchers are only beginning to understand the impacts of these differences on the bilingual as well as the monolingual brains. There is recent evidence that distant languages, such as English and Chinese, are more likely to engage distinct neural representations in the bilingual individual, as compared with languages that are more similar to one another.

Finally, individuals have very different cognitive abilities before any new language is acquired, including their working memory and cognitive control abilities. How these kinds of individual differences impact the monolingual versus the bilingual brain is largely unknown. Only a few recent studies have started to investigate this. The hope is to identify individual differences and predict how such differences may underlie the monolingual and bilingual brains.

Where do you see the bilingual brain sciences going in the next few years? Your colleague, Professor Arturo Hernandez in an earlier post (see here) thinks we should examine how age of acquisition, language proficiency, and language control help shape the bilingual brain. What do you think?

While I share Arturo Hernandez’s view that these are significant aspects, my own perspective is that the neuroscience of bilingualism should move beyond just looking at these factors. New emerging methods in behavioral studies, computational modeling, and brain imaging are helping us to address new and exciting interdisciplinary questions.

I predict, for example, significant progress in the understanding of individual differences and bilingual language representation and learning. I also see emerging new work in identifying cross-language similarities and differences using computational and neuroimaging techniques, and these could certainly impact bilingualism research. Finally, what brain effects are attributable to language learning versus to other cognitive experiences will be yet another very fruitful direction of research in the near future.

We will also need a better understanding of the issue of domain-general vs. domain-specific cognitive capacity and effects of transfer across domains. Work along these lines is actively pursued by many labs including our own.

On a more practical level, what does work on the bilingual brain bring us? I'm thinking here of the assessment and treatment of aphasic patients, bilinguals who suffer from dementia, etc.

I see translational work being done in the sciences of learning that may be relevant to your question. In particular, I think that over the next few years, new research will emerge to link the lab with the classroom, to bridge basic research with pedagogical practice, and to connect virtual- and real-world learning experiences.

In the same spirit, researchers need to address the questions you raise and connect bilingual brain studies with the practical applications of treating bilinguals who suffer from cognitive and linguistic disorders. Integrating neuroscience with learning and cognition is a task for all those interested in the brain-behavior-cognition relationship. Hence, jumping on this bandwagon is not a luxury but a necessity for researchers in our field.

For a full list of "Life as a bilingual" blog posts by content area, see here.

Photo of the profile of a head from Shutterstock.


Green, D.W. (2003). Neural basis of lexicon and grammar in L2 acquisition: The convergence hypothesis. In R. van Hout, A. Hulk, F. Kuiken & R. Towell (eds.), The interface between syntax and the lexicon in second language acquisition (pp. 197–208). Amsterdam: John Benjamins.

Grosjean, F., & Li, P. (2013). The Psycholinguistics of Bilingualism. New York, NY: John Wiley & Sons, Inc.

Li, P., Legault, J., & Litcofsky, K.A. (2014). Neuroplasticity as a function of second language learning: Anatomical changes in the human brain. Cortex, 58, 301-324. DOI: 10.1016/j.cortex.2014.05.001

Li, P. (2015). Bilingualism as a dynamic process. In B. MacWhinney & W. O’Grady (eds.), Handbook of language emergence (pp. 511-536). Malden, MA: John Wiley & Sons, Inc.

François Grosjean's website.

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