Bilingualism, Demographics, and Cognitive Control: A Within-Group Approach

Previous work has shown that bilingualism is associated with more effective controlled processing in children; the assumption is that the constant management of 2 competing languages enhances executive functions (E. Bialystok, 2001). The present research attempted to determine whether this bilingual advantage persists for adults and whether bilingualism attenuates the negative effects of aging on cognitive control in older adults. Three studies are reported that compared the performance of monolingual and bilingual middle-aged and older adults on the Simon task. Bilingualism was associated with smaller Simon effect costs for both age groups; bilingual participants also responded more rapidly to conditions that placed greater demands on working memory. In all cases the bilingual advantage was greater for older participants. It appears, therefore, that controlled processing is carried out more effectively by bilinguals and that bilingualism helps to offset age-related losses in certain executive processes. ((c) 2004 APA, all rights reserved)

Ninety-six participants, who were younger (20 years) or older (68 years) adults and either monolingual or bilingual, completed tasks assessing working memory, lexical retrieval, and executive control. Younger participants performed most of the tasks better than older participants, confirming the effect of aging on these processes. The effect of language group was different for each type of task: Monolinguals and bilinguals performed similarly on working memory tasks, monolinguals performed better on lexical retrieval tasks, and bilinguals performed better on executive control tasks, with some evidence for larger language group differences in older participants on the executive control tasks. These results replicate findings from individual studies obtained using only 1 type of task and different participants. The confirmation of this pattern in the same participants is discussed in terms of a suggested explanation of how the need to manage 2 language systems leads to these different outcomes for cognitive and linguistic functions. (c) 2008 APA

The hypothesis that managing two languages enhances general executive functioning is examined. More than 80% of the tests for bilingual advantages conducted after 2011 yield null results and those resulting in significant bilingual advantages tend to have small sample sizes. Some published studies reporting significant bilingual advantages arguably produce no group differences if more appropriate tests of the critical interaction or more appropriate baselines are used. Some positive findings are likely to have been caused by failures to match on demographic factors and others have yielded significant differences only with a questionable use of the analysis-of-covariance to "control" for these factors. Although direct replications are under-utilized, when they are, the results of seminal studies cannot be reproduced. Furthermore, most studies testing for bilingual advantages use measures and tasks that do not have demonstrated convergent validity and any significant differences in performance may reflect task-specific mechanism and not domain-free executive functions (EF) abilities. Brain imaging studies have made only a modest contribution to evaluating the bilingual-advantage hypothesis, principally because the neural differences do not align with the behavioral differences and also because the neural measures are often ambiguous with respect to whether greater magnitudes should cause increases or decreases in performance. The cumulative effect of confirmation biases and common research practices has either created a belief in a phenomenon that does not exist or has inflated the frequency and effect size of a genuine phenomenon that is likely to emerge only infrequently and in restricted and undetermined circumstances.