The advantage to being bilingual and how it arises

People often ask whether growing up bilingual can put a child at a disadvantage. Will the child develop slower, and ultimately, know each language less well? Indeed, Ellen Bialystok, a leading researcher on the cognitive effects of bilingualism, points out that bilingual children have been shown to command smaller vocabularies in each of their two languages. In adults, the disadvantage persists, but in the form of a deficit in lexical retrieval - or how quickly you can access vocabulary words.

However, in a recent article entitled The source of enhanced cognitive control in bilinguals (2008), Ellen Bialystok and three other researchers discuss the cognitive advantage to being bilingual: enhanced executive control (as compared to monolinguals). According to Miyake et al. (2000), executive control consists of three frequently-cited functions: shifting mental states, monitoring short term memory representations, and inhibiting practiced responses. In the present article (hereto referred to as Emmorey et al., 2008), the authors specifically focus on inhibiting practiced responses. This simply means that you've been engaging in Task A, and in order to engage in Task B, you must first prevent yourself from engaging in Task A again. Emmorey et al. argue that bilinguals spend much of the time inhibiting one language in order to speak or comprehend the other language, and this is why they show enhanced executive control.

It should be noted that this conclusion is limited to unimodal bilinguals - bilinguals whose two languages use the same modality (namely, speech). Bimodal bilinguals, on the other hand, know both a spoken language and sign language. The interesting part about this distinction is that bimodal bilinguals do not need to inhibit one language in order to communicate with the other. They can technically "speak" both at the same time. Thus, if they (like unimodal bilinguals) display an advantage with regard to inhibiting practiced responses, then it shows that this advantage in bilinguals does not stem from the extra time spent inhibiting one language while using the other.

To restate: unimodal bilingual individuals show enhanced cognitive control compared to monolinguals. However, the cause remains unknown. If it is due to the practiced inhibition of one language in order to communicate with the other, then only unimodal bilinguals will show an advantage. If, however, it is due to something else, both unimodal and bimodal bilinguals will show an advantage. Note that not showing an advantage would mean performing on par with monolinguals on the executive control task.

In order to get at this distinction, Emmorey et al. tested unimodal bilinguals, bimodal bilinguals, and monolinguals on a task known as the "flanker task". In this task, participants must say which direction a particular arrow is pointing within an array of arrows. The diagram below shows an example.


Sometimes, as in the above example, the task is relatively easy. However, as in the diagram below, sometimes it's more difficult. This is because all of the other arrows (the flankers) are facing in the opposite direction, making you want to say that direction (in this case, right).

The former example is called the "congruent" condition and the latter is called the "incongruent" condition. Emmorey et al. added two more conditions to this, known as the "go" and "no-go" conditions. In the go condition (on the left, below), participants were asked to perform the same task as above, but the central red arrow was in the middle of two red diamonds. In the no-go condition (on the right, below), the central red arrow was in the middle of two red Xs, and participants were told that they must inhibit responses to this type of trial. Finally, there was a control condition, which consisted of just one arrow with no flankers.

The graph below summarizes Emmorey et al.'s findings.

The y-axis is the reaction times of the participants. A higher number means that participants were slower to react. A lower number means that they were faster, or more successful, at the task. As you can see, the unimodal bilingual individuals were fastest to react on the go, congruent, and incongruent trial types. (Note that the no-go trials are not displayed in the graph because participants were asked to inhibit a response.) In contrast, the bimodal bilinguals performed at the same speed as the monolinguals. Thus only the unimodal bilinguals showed an advantage. These results provide strong evidence for the claim that the bilingual executive control advantage (or really, the unimodal bilingual advantage) arises from extra practice at inhibiting one language while using the other.

Bialystok, E. (2009). Bilingualism: The good, the bad, and the indifferent. Bilingualism: Language and Cognition, 12(1), 3-11.

Emmorey, K., Luk, G., Pyers, J.E., & Bialystok, E. (2008). The source of enhanced cognitive control in bilinguals. Psychological Science, 19(12), 1201-1206.

Miyake, A., Friedman, N.P., Emerson, M.J., Witzki, A.H., Howerter, A., & Wager, T.D. (2000). The unity and diversity of executive functions and their contributions to complex "frontal lobe" tasks: a latent variable analysis. Cognitive Psychology, 41, 49-100.