The Consequences of Bilingualism for the Mind and the Brain.

Until recently, research on language processing and its cognitive basis assumed that monolingual speakers were the model subjects of study and that English provided an adequate basis on which universal principles might be generalized. In this view, bilinguals were considered a special group of language users, much like brain-damaged patients, children with language disorders, or deaf individuals who use a signed language to communicate. Each of these special groups held genuine interest for the field, but their performance was not taken to provide primary evidence for the purpose of adjudicating the classic debates about the representation of language in the mind and brain. In the past two decades, this situation has changed with the realization that bilingualism is not an exceptional feature of a small group of language users but a common state of affairs in many places in the world. The rapid increase in research on bilingualism has spawned all of the usual academic conferences and professional journals. But more critically, it has enabled the insight that bilinguals provide a unique lens for cognitive scientists, neuroscientists, and clinicians who seek to understand the trajectory of cognitive and language development, its basis in the brain, and the nature of disorders that may be manifest when more than a single language is engaged. The article by Bialystok, Craik, Green, and Gollan that appears in this issue of Psychological Science in the Public Interest provides an outstanding summary of these recent developments on bilingualism and its consequences. Bialystok et al. demonstrate that, contrary to the earlier view that bilingualism is a special case, the acquisition and use of multiple languages reveal new discoveries about the mind and the brain that would not be possible from studies focused only on monolingual use of the native language. What lessons can we take from Bialystok et al.’s review of this emerging area of research? The message that is perhaps most relevant to the goal of placing psychological science in the public domain is that bilingualism is a good thing. Contrary to the view that young children will be confused by exposure to more than one language and harmed by delays in development, the research to date demonstrates that exposure to two languages from birth enables children to recognize and distinguish speech in both languages. The course of development for bilingual-learning children may differ in subtle ways from that of monolingual children, but bilingual children are not harmed by the multiple exposure. To the contrary, the past 20 years of research suggests that by the time bilingual children are 3 or 4 years old, not only have they acquired the ability to recognize speech in two languages but their cognitive development is also advantaged relative to their monolingual counterparts. Bialystok herself has been a pioneer in demonstrating that bilingualism confers positive consequences to young children in the domain of executive function and attentional control. Bilingualism appears to play a significant role in enhancing young children’s ability to ignore irrelevant information, reducing the competition that is imposed by cognitive conflict, and enabling an understanding of the arbitrariness of the way words are mapped to concepts. More recently, Bialystok and Craik together have extended this research program to show that the bilingual advantage extends into old age. Cognitive aging affects the same executive functions that the earlier research on children had shown were affected by bilingualism. It was therefore a reasonable conjecture that bilingualism might also benefit the elderly at a time in life when cognitive resources decline. These studies provide dramatic evidence that life as a bilingual provides protection against the typical cognitive declines observed in old age. Bilingualism is not an antidote to cognitive aging, so you might read this issue of Psychological Science in the Public Interest fully before you rush off to Spanish class! But in precisely those domains that are vulnerable to aging, bilingualism appears to modulate the rate of cognitive decline. Performance on tasks that are purely cognitive, with little explicit linguistic content, is superior for older bilinguals than it is for older monolinguals. The skeptics among you might wonder if bilinguals are advantaged for some other reason. Perhaps bilingual children