In the current issue of Psychological Science in the Public Interest, a journal of the Association for Psychological Science, Ellen Bialystok (York University), Fergus I.M. Craik (Rotman Research Institute), David W. Green (University College London), and Tamar H. Gollan (University of California, San Diego) review the latest research on bilingualism and ways in which knowing two languages can change brain function, even affecting brain areas not directly involved in communication.
Children learning two languages from birth achieve the same basic milestones (e.g., their first word) as monolinguals do, but they may use different strategies for language acquisition. Although bilinguals tend to have smaller vocabularies in each language than do children who know one language, bilinguals may have an advantage when it comes to certain nonverbal cognitive tasks. Bilinguals tend to perform better than monolinguals on exercises that require blocking out distractions and switching between two or more different tasks.
The authors note that “when a bilingual speaks two languages regularly, speaking in just one of these languages requires use of the control network to limit interference from the other language and to ensure the continued dominance of the intended language.” The bilingual advantage in attention and cognitive control may have important, long-term benefits. Preliminary evidence even suggests that their increased use of these systems may protect bilinguals against Alzheimer’s.
The differences between monolinguals and bilinguals have important clinical implications. For example, vocabulary tests are commonly used in psychologists’ offices and bilinguals’ scores may not accurately reflect their language ability. According to the authors, “Bilinguals who score below average may be inaccurately diagnosed with impairment when none is present, or could be diagnosed as ‘normal for a bilingual’ even though impairment is in fact present and treatment is needed.” Clinicians need to be aware of the potential to misinterpret bilinguals’ test scores. Developing tests that specifically target bilingual populations may result in better outcomes for these patients.