Concordia Researchers Find Greater Cognitive Benefits in More Proficient Bilingual Toddlers
New research shows that toddlers who are more proficient at switching between two languages display stronger problem-solving and mental control skills.
Around half of the world’s population speaks two or more languages, and a growing body of research suggests that bilingualism provides cognitive advantages. A recent longitudinal study led by Concordia University researchers demonstrates a clear benefit in young children’s executive function: bilingual toddlers outperformed monolingual peers on tasks requiring conflict inhibition, and those bilingual children who practiced switching languages more often showed the greatest gains.
The study, published in the Journal of Experimental Child Psychology, tracked language development and cognitive performance in toddlers across a seven-month span. Diane Poulin-Dubois, a professor in Concordia’s Department of Psychology and the study’s senior author, explains that as children’s vocabularies expand, they increasingly switch between languages. “This switching becomes more frequent as children grow older and as their vocabulary size increases,” she says. “Superior performance on conflict tasks appears to stem from strengthened cognitive flexibility and selective attention that come from repeated practice in switching across languages.”
Study Design and Participants
The longitudinal investigation, led by Poulin-Dubois along with Cristina Crivello of Concordia’s Centre for Research in Human Development (CRDH), compared 39 bilingual toddlers and 43 monolingual toddlers. Researchers measured expressive vocabulary and the number of translation equivalents (pairs of words for the same concept in each language) at 24 months and again at 31 months. At the second assessment, toddlers completed a battery of cognitive tests examining conflict inhibition, delay, and working memory.
Overall performance on many tasks was similar between bilingual and monolingual groups. However, clear differences emerged on conflict inhibition tests. “For the most part, there was no difference between the bilingual and monolingual toddlers,” Poulin-Dubois notes, “but that changed dramatically on conflict inhibition tasks, especially for bilingual toddlers whose vocabulary growth—and thus language switching—had been greatest.”
Conflict Inhibition Tasks
Conflict inhibition refers to the ability to override a dominant or automatic response in favor of a rule that conflicts with that instinct. To evaluate this ability in toddlers, Crivello administered two specific tests:
- Reverse categorization: Children were first instructed to sort small blocks into a small bucket and large blocks into a large bucket. The rule was then reversed, requiring children to place large blocks in the small bucket and small blocks in the large bucket.
- Shape conflict: Children viewed pictures of different-sized pieces of fruit and were asked to identify them. In a later set, a small fruit was embedded inside a larger fruit, and toddlers were asked to point to the small fruit, requiring them to ignore the larger surrounding image.
Bilingual toddlers performed significantly better than monolinguals on these conflict inhibition measures. Within the bilingual group, those with a greater increase in translation equivalents—meaning they had two-known words for many concepts, such as dog/chien—showed the strongest performance. This pattern supports the idea that frequent practice switching between lexical systems enhances selective attention and cognitive flexibility.
Interpretation and Implications
According to Cristina Crivello, language switching provides practice in ignoring competing information—similar to the demands placed on children during conflict tasks. “In conflict inhibition, the child has to ignore certain information—the size relationship of a block to a bucket, or the fact that one fruit is inside another. That mirrors having to switch between languages and use a second-language word even when the first-language word may be more accessible,” she says.
By the end of the third year of life, many bilingual children possess two words for most concepts in their vocabulary, which increases opportunities to switch across languages. The researchers suggest that this repeated switching fosters cognitive control skills, particularly those involved in selective attention and cognitive flexibility.
Funding: The research was supported by a Discovery Grant from the Natural Sciences and Engineering Research Council of Canada (NSERC) and by the National Institute of Child Health and Human Development. Additional co-authors include Olivia Kuzyk and Monyka Rodrigues (Concordia University), Margaret Friend (San Diego State University) and Pascal Zesiger (Université de Genève).
Source: Cléa Desjardins, Concordia University.
Image source: Photo credit to Jose-Luis Olivares/MIT, adapted from a previous press release.
Original research: “The effects of bilingual growth on toddlers’ executive function” by Cristina Crivello, Olivia Kuzyk, Monyka Rodrigues, Margaret Friend, Pascal Zesiger, and Diane Poulin-Dubois. Published online January 2016 in the Journal of Experimental Child Psychology. doi:10.1016/j.jecp.2015.08.004
Abstract (Summary)
The study examined whether growth in bilingual proficiency, measured by an increase in translation equivalents over seven months, was associated with improvements in executive function in toddlers. Expressive vocabulary and translation equivalents were measured at 24 and 31 months. At 31 months, children completed tasks assessing conflict inhibition, delay, and working memory. Results showed a task-specific advantage for bilinguals on inhibitory control. Critically, within the bilingual group, larger increases in translation equivalents predicted better performance on conflict tasks but not on delay tasks. This longitudinal design strengthens the evidence linking early bilingual growth to improved executive function.