Cognitive control in bilingual children: disentangling effects of second language proficiency and onset age of acquisition

Studies comparing bilingual to monolingual speakers on cognitive control are
inconclusive about the nature and underlying mechanisms of language-related
processing differences. In the present study, we therefore compared a group of
bilingual Dutch/French children that had started acquisition of both languages at birth
(the simultaneous bilingual group) to a group of children that had started acquisition of
their second language at the age of three (the early bilingual group), in order to
disentangle the impact of second language onset age of acquisition and bilingualism
on cognitive control. 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 non-linguistic cognitive control task (the
color Simon task). The results of our study show higher global accuracy rates for the
simultaneous bilinguals on the Simon task. Surprisingly, no differences in mean
reaction times between the two bilingual groups were found. To conclude, this study
finds no advantage on verbal fluency, but does reveal that acquiring two languages
from birth onwards gives simultaneous bilingual children an advantage on the Simon
task, even over early bilingual children and when the second language proficiency is
kept equal.