A new study has said that kids who learn to speak two languages are better at switching between tasks than children who learn to speak only one language.
But researchers also found that bilinguals are slower to acquire vocabulary than are monolinguals, because bilinguals must divide their time between two languages while monolinguals focus on only one.
In the study funded in part by the National Institutes of Health, bilingual and monolingual children were asked to press a computer key as they viewed a series of images-either of animals or of depictions of colours.
Researchers often use this switching task to gauge a set of mental processes known as executive functioning-generally defined as the ability to pay attention, plan, organize, and strategize. The task engages three mental processes: the ability to keep a rule or principle in mind (working memory), inhibition (the ability to refrain from carrying out one rule), and shifting (the ability to make the change and act on another rule).
"In simplest terms, the switching task is an indicator of the ability to multi-task," said Peggy McCardle, Ph.D., chief of the Child Development and Behaviour Branch at the NIH's Eunice Kennedy Shriver National Institute of Child Health and Human Development.
"Bilinguals have two sets of language rules in mind, and their brains apparently are wired to toggle back and forth between them depending on the circumstances," McCardle explained.
The study was conducted by Raluca Barac and Ellen Bialystok at York University in Toronto, Canada.
In the study, the researchers tested verbal and nonverbal cognitive abilities of 104 6-year-old children from the Toronto area. All were public school students, and from similar economic and social backgrounds.
In addition to English monolinguals and English-French bilinguals, the study also included English-Spanish and English-Chinese bilinguals. Along with the switching task, the test battery consisted of three English language tests of verbal ability. The verbal tests measured vocabulary and children's understanding of such linguistic tasks as forming plurals, conjugating verbs, grammatical structure, and English pronunciation rules.
For the switching task, accuracy scores were similar for all the groups, with the groups choosing the correct option approximately the same proportion of times. However, all of the bilinguals could switch from one task to another more rapidly than could the monolinguals.
In tests of verbal ability, the English language monolinguals scored highest on a measure of English receptive vocabulary-the body of words a person recognizes well enough to comprehend when hearing them or listening to them.
Because they have to learn only English, the monolinguals were able to acquire a larger vocabulary than could any of the bilingual groups, who need to divide their time between acquiring two vocabularies.
The monolinguals also scored higher than did the other groups on a test measuring knowledge of English grammar and word meaning.
The study has been published online in Child Development.