Bilingualism and brain lateralization of attentional networks

Different sides of the brain specialize in different tasks. For example, language processing usually takes place in the left side of the brain, whereas attention is thought to take place mostly in the right side of the brain. This division of labour between the different brain hemispheres is called lateralization. Some researchers have suggested that if people practice a particular skill until they become very good at it, then that skill may become less lateralized (i.e., it will be more spread out between the two sides of the brain, rather than concentrated in a single side).

One area where bilinguals have been shown to outperform monolinguals is attention – for example, someone who speaks Spanish and English has had a lot of practice of attention-sapping tasks, such as switching between two languages, or ignoring Spanish words when speaking English. [Read more…]

Understanding the enhanced cognitive control in bilinguals

From previous studies, we have seen that bilinguals tend to outperform monolinguals in some tasks requiring subjects to switch between two stimuli; these are known as Cognitive Control tasks. The bilinguals that have taken part in many of these studies are people who speak two languages under the same modality for instance, two spoken languages (unimodal bilinguals). But what happens when a person knows two languages in different modalities, like in the case of bimodal bilinguals, who know a spoken language and a sign language? On this study, there were three groups of participants: unimodal bilinguals, bimodal bilinguals, and people who only knew one language (monolinguals).  Interestingly, all three groups performed equally well in tasks involving ignoring one stimulus in order to respond to another, but the only difference was that unimodal bilinguals were faster than both bimodal bilinguals and even monolinguals. As the authors point out,  bimodal bilinguals can, in fact, produce words simultaneously (one signed, one spoken), whereas unimodal bilinguals have to suppress one language when speaking the other one, because it is impossible to say two words at the same time. Therefore, the faster responses for the unimodal bilinguals could be accounted for by the fact that they are better ‘trained’ at suppressing one language when speaking the other one.

This is a summary of the following published article:

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