A cross-sectional developmental approach to bilingualism: Exploring neurocognitive effects across the lifespan

This article summarises over ten years of research on the effects of multilanguage acquisition on cognitive development (and decline) across the lifespan conducted by our lab. We adopted a developmental approach to research on bilingualism with the aim of building developmental trajectories of components of executive functions and metacognition. We examined the performance of over 900 individuals from the age of 8–80 years, half of them multilinguals. They were all tested individually with a battery of behavioural tasks and a large number of adult participants underwent structural magnetic resonance imaging (MRI). For all participants we collected biographical, linguistic, and socio-economic data. Taken together, our studies show that behavioural performance across multiple cognitive indicators does not differ between multilingual and monolingual groups when they are carefully matched on potential confounding covariates such as socio-economic status and language experience, and that the evidence base against a multilingual advantage is disproportionately robust when sample size is comparatively large. Nevertheless, we have also identified possible differences in the functional architecture of higher-level cognition across these groups, indicating that the process of acquiring a second language may alter the distributed networks underpinning cognitive control. Our findings have contributed to a better understanding of the effects of multilingualism on cognitive and metacognitive processes across the lifespan. They have shown that multilingual acquisition is neither detrimental nor advantageous to domain-general cognitive development but may nevertheless promote functional and structural adaptation in the service of control of linguistic interference.