UC San Diego

Bilingual individuals seem to easily speak in just one language, and switch back and forth between languages, suggesting they have powerful mechanisms for controlling activation of their two languages. A prominent theory suggests that cognitive control, and specifically inhibition of the non-target language, enables successful switching. We used behavioral and neuroimaging methods to study Spanish-English bilinguals to determine: 1) if college-aged bilinguals show an advantage in general task-switching ability relative to monolinguals given bilinguals’ extensive practice with language switching; 2) if cognitive control regions are recruited in bilingual language comprehension, and 3) if an aging deficit in inhibitory control affects older bilinguals’ (age 65+) ability to switch languages. In Study 1 (n = 80 per group; Stasenko et al., 2017) bilinguals exhibited more efficient task-switching, but only when participants had longer preparation time, and the advantage dissipated quickly. These findings suggest that although bilingualism improves the efficiency of task switching, this advantage might be more related to preparing to switch than to switching per se. In Study 2 (n = 24; Stasenko et al., 2020), bilinguals recruited fronto-parietal brain regions (i.e., right frontal inferior gyrus, bilateral middle frontal gyrus, and left supramarginal gyrus) when switching relative to not switching languages even in silent reading of mixed language paragraphs (without producing any switches in their speech). These results suggest that although reading comprehension seems to be passive, it recruits brain regions known to support cognitive control, possibly reflecting a modality-general switch mechanism. Study 3 (ns = 48 and 25; Stasenko et al., submitted) revealed a reversal of language dominance in mixed-language testing blocks, and a transfer of inhibition from a repeated set of items to a new set of items (that was introduced halfway through the task). Both effects were found only in younger but not in older bilinguals. Overall, these findings support the role of domain-general cognitive control and inhibition as an important mechanism in bilingual language control that spans across production and comprehension and exhibits decline in healthy aging.