Being bilingual increased the size of the part of the brain responsible for processing thoughts than those that speak their mother tongue, researchers found. In the past it had been thought children who spoke two languages at home did less well at school. But recent research found bilingual children perform better on tasks that require attention, inhibition and short-term memory, collectively termed “executive control” than their monolingual peers. A study by Georgetown University Medical Centre found adults who are polyglots do have more grey matter but those who used sign language did not. It adds to a growing understanding of how long-term experience with a particular skill – in this case fluency in two languages – changes the brain. Dr Guinevere Eden, from the university, said: “Inconsistencies in the reports about the bilingual advantage stem primarily from the variety of tasks that are used in attempts to elicit the advantage. “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.” The study published in the journal Cerebral Cortex explored why differences in grey matter in people was based on experiences. Dr Olumide Olulade, a co-author of the study, said: “Our aim was to address whether the constant management of two spoken languages leads to cognitive advantages and the larger grey matter we observed in Spanish-English bilinguals, or whether other aspects of being bilingual, such as the large vocabulary associated with having two languages, could account for this.” It compared the grey matter in bilinguals of American Sign Language (ASL) and spoken English with monolingual users of English. Both ASL-English and Spanish-English bilinguals share qualities associated with bilingualism, such as vocabulary size. Unlike bilinguals of two spoken languages, ASL-English bilinguals can sign and speak simultaneously, allowing the researchers to test whether the need to inhibit the other language might explain the bilingual advantage.