During the mental flexibility task (which evaluated their ability to switch their attention from one target to another), a blue and a green dragon appeared randomly on the screen, either on the left or the right side of the screen. The children had reaction keys on the left and right sides of the keyboard. During the first trial they were asked to press the reaction key on the side where the green dragon appeared, and during the next trial they were asked to press the reaction key on the side where the blue dragon appeared (which could be the same side where the green dragon had appeared in the previous trial). And so on. In other words, mental flexibility was measured by the ability to inhibit their intention - expressed by the hand movement - to push one of the two buttons if the intention was inappropriate.

And what did the researchers discover? In all three tasks, children who were in linguistic immersion programmes for 3 years had, on average, a similar number of errors to their monolingual peers, but their response time was faster. Even though the advantage was slight, it was significant. "This means that they had better control of the situation on a cognitive level, which was manifested by a quicker response to the stimulus," explains Martine Poncelet.

"We subsequently obtained similar results in children who we ensured had the same average cognitive performance levels before they entered either a bilingual immersion or monolingual programme(6)."  

Contrary to what Ellen Bialystok's studies suggested, the observed advantage seems to fade over time. The ULg psychologists tested 6th grade students and the first adults that were placed in second-language immersion in Léonie de Waha school (in 1989) for selective auditory attention, divided attention, and mental flexibility. They found no difference between these two sample groups and control populations of same-age monolingual subjects. Is the advantage of bilingualism thus only temporary? And if so, why? "For adults, one of the hypotheses is that people reach the height of their attentional and executive skills around the age of 25, and by definition, they cannot go beyond this limit," says Martine Poncelet. “Another hypothesis suggests that the advantage of bilingualism comes from going back and forth frequently between both languages, but a number of adults don't have regular opportunities to practice their second language.”

However this doesn't explain why the cognitive advantage of bilingualism seems to have already disappeared from children in the sixth year of primary school. "In any case,” says the researcher, “we need to confirm our result by replicating the study on a larger scale - our study was limited to 30 children. We would also like to determine when the cognitive advantage emerges. This is why we intend to conduct evaluations after a year and a half of immersion." 

(6)Nicolay, A.-C., & Poncelet, M. (submitted). Cognitive benefits in children enrolled in an early bilingual immersion school: A follow-up study.