People can intuitively recognise small numbers up to four; however, when calculating they depend on the assistance of language. In this respect, the fascinating research question ensues: how do multilingual people solve arithmetical tasks presented to them in different languages of which they have a very good command? The question will gain in importance in the future, as an increasingly globalised job market and accelerated migration will mean that ever more people seek work and study outside of the linguistic area of their home countries.

This question was investigated by a research team led by Dr Amandine Van Rinsveld and Professor Dr Christine Schiltz from the Cognitive Science and Assessment Institute (COSA) at the University of Luxembourg. For the purpose of the study, the researchers recruited subjects with Luxembourgish as their mother tongue, who successfully completed their schooling in the Grand Duchy of Luxembourg and continued their academic studies in francophone universities in Belgium. Thus, the study subjects mastered both the German and French languages perfectly. As Luxembourger students, they took maths classes in primary schools in German and then in secondary schools in French.

In two separate test situations, the study participants had to solve very simple and a bit more complex addition tasks, both in German and French. In the tests it became evident that the subjects were able to solve simple addition tasks equally well in both languages. However, for complex addition in French, they required more time than with an identical task in German. Moreover, they made more errors when attempting to solve tasks in French.

During the tests, functional magnetic resonance imaging (fMRI) was used to measure the brain activity of the subjects. This demonstrated that, depending on the language used, different brain regions were activated. With addition tasks in German, a small speech region in the left temporal lobe was activated. When solving complex calculatory tasks in French, additional parts of the subjects' brains responsible for processing visual information, were involved. However, during the complex calculations in French, the subjects additionally fell back on figurative thinking. The experiments do not provide any evidence that the subjects translated the tasks they were confronted with from French into German, in order to solve the problem. While the test subjects were able to solve German tasks on the basis of the classic, familiar numerical-verbal brain areas, this system proved not to be sufficiently viable in the second language of instruction, in this case French. To solve the arithmetic tasks in French, the test subjects had to systematically fall back on other thought processes, not observed so far in monolingual persons.

The study documents for the first time, with the help of brain activity measurements and imaging techniques, the demonstrable cognitive "extra effort" required for solving arithmetic tasks in the second language of instruction. The research results clearly show that calculatory processes are directly affected by language.

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