A study published in the journal Cerebral Cortex suggests that bilingual people have more grey matter in the ‘executive control’ region of the brain.
Scientists used to believe that the ability to speak two languages could delay a child’s development. But studies have shown that bilingual people are better able to carry out tasks which rely on short-term recall and attention – that is, executive control functions.
The results of these studies aren’t entirely consistent, and so it is still a contentious subject. The study’s lead author, Guinevere Eden, director of the Center for the Study of Learning at Georgetown University Medical Centre, explains why:
‘Inconsistencies in the reports about the bilingual advantage stem primarily from the variety of tasks that are used in attempts to elicit the advantage.’
Her research aimed to eliminate this problem.
‘Given this concern, we took a different approach and instead compared grey matter volume between adult bilinguals and monolinguals. We reasoned that the experience with two languages and the increased need for cognitive control to use them appropriately would result in brain changes in Spanish-English bilinguals when compared with English-speaking monolinguals. And in fact greater grey matter for bilinguals was observed in frontal and parietal brain regions that are involved in executive control.’
It is known that the volume of grey matter – which processes information in the brain – changes as a result of a person’s experiences. This study looked at the reasons behind this change. The researchers compared grey matter in people who can speak English and Spanish with people who can speak English and use American Sign Language (ASL). Because English and ASL can be used simultaneously, this allowed the researchers to test whether the need to inhibit the other language could account for the ‘bilingual advantage’.
The study’s lead author, Olumide Olulade, explains the results.
‘Unlike the findings for the Spanish-English bilinguals, we found no evidence for greater grey matter in the ASL-English bilinguals. Thus we conclude that the management of two spoken languages in the same modality, rather than simply a larger vocabulary, leads to the differences we observed in the Spanish-English bilinguals.’
The researchers say that this finding will help scientists to better understand how our experiences change the make-up of our brains.