Are bilinguals better than monolinguals at controlling their mental processes? Do bilinguals get some protection from dementia symptoms because they know more than one language? Is there really a “bilingual advantage”?

Scientists have spent recent decades exploring questions like these about how knowing more than one language affects a person. Research on these topics has led to new insights into how language affects the brain and behavior, but some of these questions have proven difficult to answer. For example, research on a potential bilingual advantage has found mixed results (e.g., Lehtonen et al., 2018), in part because of the approach required to address this question.  This type of question relies on comparing groups of bilinguals to groups of monolinguals, which comes with some serious limitations.

For one, grouping all bilinguals together into one category to compare to all monolinguals simplifies bilingualism into a single category when it is actually a continuum. Leaving aside the statistical issues with splitting a continuum into two strict categories (MacCallum et al., 2002), this classification system assumes that all bilinguals and all monolinguals will have similar language experiences that will affect their performance on a given experimental task. However, monolinguals who speak two dialects may experience many of the same daily pressures to monitor and switch their language as bilinguals who speak two languages. If we think that type of language monitoring and switching impacts cognition, then we might expect bidialectal monolinguals to perform more like bilinguals than like other monolinguals (Oschwald et al., 2018).

Furthermore, not all bilinguals are the same. Some bilinguals use one language at work and another at home, strictly separating their use. Other bilinguals use both their languages in the same contexts, but only use one language with each specific person they interact with, requiring them to switch between their languages in a controlled way. And still other bilinguals may freely switch between their languages without careful monitoring because they interact with other bilinguals who know the same languages (Green and Abutalebi, 2013). If we think that bilinguals’ language experience might affect other aspects of their brain or behavior, we should expect that different language experiences might have different effects, suggesting that all bilinguals should not be clumped together as one group.

Additionally, when comparing bilinguals to monolinguals, we cannot make cause-and-effect claims because we cannot assign a person to be bilingual or monolingual. Instead, these studies tend to correlate people’s performance on one task with their performance on another task to determine whether bilinguals or monolinguals had an advantage over the other. This approach often measures performance at one point in time to determine if each person was “good” or “bad” at the experimental tasks. Summarizing performance in this way can simplify the reality of it: Even someone who is typically “good” at the task may perform poorly on a particular day or in a particular context.

While we can use results from these approaches to learn more and to shape our theories, this correlational approach can only answer questions about how one group of people differs from another group. It cannot make cause-and-effect claims or speak to how one individual might perform differently under different circumstances. To answer those questions, we need to complement existing between-group comparisons with a newer within-participant comparison approach that compares bilinguals to themselves under different contexts.

By comparing bilinguals to themselves, we can ask questions like: Under what conditions do bilinguals perform best on certain tasks? Does a bilingual’s performance on a cognitive task change when they are in different language contexts (Adler et al., 2020; Wu & Thierry, 2013)? How does being in a particular cognitive state affect a bilingual’s language processing (Liu et al., 2019)?

Recent work has already begun to show that a bilingual’s language environment can affect their performance on cognitive tasks (and vice versa: a bilingual’s cognitive state can affect their linguistic performance). For instance, one study found that when bilinguals were in a context that used both of their languages instead of just one language, they did better on a cognitive task that required them to ignore distracting information (Wu & Thierry, 2013). That is, having to activate both of their languages in the same context improved their performance on an unrelated cognitive task. This variation in performance based on language context is undetectable when comparing bilinguals to monolinguals but can lead to new understandings of how bilinguals’ linguistic and non-linguistic processes interact.

Using a within-participant comparison approach allows us to move beyond looking at bilingualism as a static, unchanging language experience and instead ask new questions about how bilingualism affects the brain and behavior from moment-to-moment.

Works Cited

Adler, R. M., Valdés Kroff, J. R., & Novick, J. M. (2020). Does integrating a code-switch during comprehension engage cognitive control?. Journal of Experimental Psychology: Learning, Memory, and Cognition, 46(4), 741-759.

Green, D. W., & Abutalebi, J. (2013). Language control in bilinguals: The adaptive control hypothesis. Journal of Cognitive Psychology, 25(5), 515-530.

Lehtonen, M., Soveri, A., Laine, A., Järvenpää, J., De Bruin, A., & Antfolk, J. (2018). Is bilingualism associated with enhanced executive functioning in adults? A meta-analytic review. Psychological Bulletin, 144(4), 394-425.

Liu, C., Jiao, L., Wang, Z., Wang, M., Wang, R., & Wu, Y. J. (2019). Symmetries of bilingual language switch costs in conflicting versus non-conflicting contexts. Bilingualism: Language and Cognition, 22(3), 624-636. DOI:10.1017/S1366728918000494

MacCallum, R. C., Zhang, S., Preacher, K. J., & Rucker, D. D. (2002). On the practice of dichotomization of quantitative variables. Psychological Methods, 7(1), 19–40.

Oschwald, J., Schättin, A., Von Bastian, C. C., & Souza, A. S. (2018). Bidialectalism and bilingualism: Exploring the role of language similarity as a link between linguistic ability and executive control. Frontiers in Psychology, 9, 1997.

Wu, Y. J., & Thierry, G. (2013). Fast modulation of executive function by language context in bilinguals. Journal of Neuroscience, 33(33), 13533–13537.

About the Author

Lauren Salig is a graduate student in the Neuroscience and Cognitive Science program at the University of Maryland. She is interested in studying bilingual language processing and how it interacts with other cognitive processes.

Expenses related to this research were funded by the MCM Fund for Student Research Excellence. This award is designed to support independent student research projects, and is made possible by an anonymous donation to the Department and by other donations by faculty, alumni, and friends. Please consider donating to the fund through the following link: