The neuronal networks responsible for executive control are centered in the frontal lobes, with connections to other brain regions as necessary for specific tasks. Executive control emerges late in development and declines early in aging, and supports such activities as high level thought, multi-tasking, and sustained attention. Executive control is the set of cognitive skills based on limited cognitive resources for such functions as inhibition, switching attention, and working memory. In contrast to this pattern, bilinguals at all ages demonstrate better executive control than monolinguals matched in age and other background factors. Thus, the simple act of retrieving a common word is more effortful for bilinguals. Performance on these tasks reveals systematic deficits for bilingual participants, particularly in semantic fluency conditions, even if responses can be provided in either language. Finally, verbal fluency tasks are a common neuropsychological measure of brain functioning in which participants are asked to generate as many words as they can in 60 seconds that conform to a phonological or semantic cue. Slower responses for bilinguals are also found for both comprehending and producing words, even when bilinguals respond in their first and dominant language. On picture-naming tasks, bilingual participants are slower and less accurate than monolinguals.

Considering simply receptive vocabulary size, bilingual children and adults control a smaller vocabulary in the language of the community than do their monolingual counterparts. First, a large body of evidence now demonstrates that the verbal skills of bilinguals in each language are generally weaker than are those for monolingual speakers of each language. Research with adult bilinguals built on these studies with children and reported two major trends. This unexpected difference between monolingual and bilingual children was later explored in studies showing a significant advantage for bilingual children in their ability to solve linguistic problems based on understanding such concepts as the difference between form and meaning, that is, metalinguistic awareness and nonverbal problems that required participants to ignore misleading information. The authors had expected to find lower scores in the bilingual group on language tasks but equivalent scores in nonverbal spatial tasks, but instead found that the bilingual children were superior on most tests, especially those requiring symbol manipulation and reorganization. A study by Peal and Lambert cast doubt on this belief by reporting that children in Montreal who were either French-speaking monolinguals or English-French bilinguals performed differently on a battery of tests. It has long been assumed that childhood bilingualism affected developing minds but the belief was that the consequences for children were negative: learning two languages would be confusing. Rather, the circumstances of their family, place of birth, or immigration history simply required that they learn more than one language.

Although bilinguals undoubtedly differ from monolinguals in certain ways, they generally did not choose bilingualism. Bilingualism is different from all of these: like juggling and playing video games it is intense, and like architecture and driving taxis in London it is sustained, but unlike these experiences, bilinguals are not typically pre-selected for talent or interest.

Such modifications have been found following experiences as diverse as juggling, video-game playing, careers in architecture taxi-driving, and musical training. The context for examining how bilingualism affects cognitive ability is functional neuroplasticity, the study of how experience modifies brain structure and brain function. What are these cognitive differences and how does bilingualism lead to these changes? Importantly, accumulating research shows that the development, efficiency, and decline of crucial cognitive abilities are different for bilinguals than for monolinguals. Bilinguals, therefore, make up a significant portion of the population. In Europe, bilingualism is even more prevalent: In a recent survey, 56% of the population across all European Union countries reported being functionally bilingual, with some countries recording particularly high rates, such as Luxembourg at 99%. These figures are higher in urban areas, rising to about 60% in Los Angeles and 50% in Toronto. and Canada, approximately 20% of the population speaks a language at home other than English.

It is generally believed that more than half of the world’s population is bilingual.

Monolingual big sur