Reassessing the role of sociolinguistic variables in neuroimaging studies of multilingualism

Research on the cognitive advantages of multilingualism has triggered much discussion in the last decade. Most of this research has focused on multilinguals' performance on cognitive conflict tasks in laboratory settings. While some researchers have given repeated proof of the existence of an advantage for multilinguals across the lifespan (Bialystok et al. 2005), others have not been able to find differences between multilinguals and monolingual control groups (Morton & Harper, 2007). Potential reasons for these contradictory results have been found in differences in the tasks employed, and in confounding variables such as the participants' socio-economic status and ethnicity.

These explanations cannot however account for all differences in how multilinguals perform on cognitive control tasks (Costa et al., 2009) Based on research carried out in the multilingual city of Barcelona, Costa et al. (2009) put forward the hypothesis that sociolinguistic variables can explain most of the contradictory results. They predicted that a) the degree of bilingualism in a given society/city and b) the degree of similarity between the two languages involved is proportionate to the existence of a bilingual advantage in a particular population. The fact that Barcelona as a Catalan-Spanish diglossic environment fulfills both these criteria might explain the presence of a cognitive advantage in this city.

In this presentation the relevance of sociolinguistic criteria to explain differences in cognitive performance of multilingual participants will be explored. First, by comparing the results from Barcelona with data collected by other teams in multilingual environments in North America and Europe. Second, by discussing the results of our own research carried out in the context of Brussels. Brussels differs from Barcelona in both aforementioned criteria: a) Dutch and French are two languages belonging to different branches of the Indo-European language family, and b) the degree of informal bilingualism in Brussels is lower than in Barcelona. In this context, we conducted a neuroimaging cognitive conflict study of two groups of simultaneous and sequential Dutch-French bilingual children and one control group with limited or no exposure to the other language. The results seem to confirm the predictions made by Costa at al., although other individual variables within the groups need to be taken into account as well.