ABSTRACT
In the early 1920s the British Journal of Psychology published two articles on the relation between bilingualism on the one hand and mental development (Smith, 1923) and intelligence (Saer, 1923) on the other hand. Since then the questions of whether and how bilingualism and multilingualism impact on cognitive functioning, in the domain of language and beyond, continue to engage policy makers, educators, language and cognition researchers, and parents of children growing up bilingually. It is easy to see why this topic draws the attention of such diverse groups of people. Cognitive functioning obviously affects academic achievement and, related to this, social and economic success in life and well-being in general. A detailed understanding of the relationship between bilingualism and cognitive functioning informs, for instance, policy makers and educators on what language policy to pursue regarding the instruction of immigrants, and parents with a different language background on what language(s) to use in their homes. On the
basis of the insights gained from careful research that addresses these questions, professionals and parents may create the circumstances that foster the beneficial effects of bilingualism and multilingualism, and frustrate their potentially harmful effects.
