Cognitive Control in Bilingual Children Disentangling the Effects of Second-Language Proficiency and Onset Age of Acquisition

Studies comparing the cognitive control of bilingual and monolingual speakers are inconclusive about the nature and underlying mechanisms of differences in language-related processing. In the present study, in order to disentangle the impact of second-language onset age of acquisition and bilingualism on cognitive control, we compared a group of bilingual Dutch/French children who had started acquisition of both languages at birth (simultaneous bilingual group) to a group of children who had started acquisition of their second language at the age of 3 years (early bilingual group). Both groups had equal proficiency in the two languages. All participants completed an extensive language test battery in Dutch and French and conducted a linguistic (verbal fluency) and a nonlinguistic cognitive control task (the color Simon task). We found higher global accuracy rates for the simultaneous bilingual group on the Simon task. Surprisingly, we did not find any differences in mean reaction time between the two bilingual groups. In conclusion, this study finds no advantage in terms of verbal fluency, but does reveal that acquiring two languages from birth onward gives simultaneous bilingual children an advantage on the Simon task, even over early bilingual children and when second-language proficiency is held constant.