Functional Neuroanatomy of Arithmetic in Bilinguals

Abstract

Despite the prevalence of bilingualism worldwide, the effect of using multiple languages on the cognitive process of math is only just beginning to be understood. Arithmetic in particular draws on linguistic representations of numerical facts and also on executive function skills, and there is evidence that monolinguals and bilinguals differ in these respects: Bilinguals are unique by virtue of having two languages with which they can perform arithmetic and store arithmetic facts, and some have argued that the lifelong experience of navigating two language systems can have consequences for other cognitive abilities. This dissertation examines brain activity during arithmetic processing in a group of English monolinguals and early Spanish-English bilinguals. Because the cognitive processes used to solve arithmetic problems differ for the different types of operations, and because adults and children may solve problems differently, we also examined potential modulatory roles for operation (addition versus subtraction) and age group (adults versus children). We used functional magnetic resonance imaging to measure brain activity while participants solved single-digit addition and subtraction problems. Our first study asked whether monolinguals and bilinguals differ in their brain activation during arithmetic, and our second study asked whether activation differs when solving arithmetic problems in either English or Spanish, within bilinguals. We examined these research questions using voxel-wise frequentist analyses, and also using Bayes factors in order to assess evidence for the null versus alternative hypotheses. Our neuroimaging findings revealed no differences in brain activation between monolinguals and bilinguals, and no differences between English and Spanish within bilinguals. Neither operation nor age group interacted with bilingual language experience or with the language used for carrying out arithmetic, in terms of affecting brain activity. Ultimately, our results show that the experience of early bilingualism results in use of the same brain regions for performing arithmetic in two languages, and in ways that are indistinguishable from a monolingual.