Bilingualism and executive functions: Behavioural evidence of inhibition and code switching in a colour Stroop task

Heidlmayr, K. 1, 2 , Moutier, S. 1 , Hemforth, B. 1 , Courtin, C. 1 & Isel, F. 1

1 Paris Descartes University, Institute of Psychology, Paris, France
2 University of Vienna, Institute for Romance studies, Vienna, Austria

Inhibition of inappropriate processing strategies is a crucial issue in psycholinguistic studies of bilingualism. Previous behavioural studies suggest that ability for selection-inhibition, which enables to activate less automatic strategies and to rule out overlearned strategies, might be higher in bilinguals. The present study investigates whether the increased capacity of bilinguals to resist interferences between competing strategies of grammatical processing has an effect on conflict detection and resolution. To approach this question, the classic colour Stroop test (Stroop, 1935) constitutes a critical test as two competing components, i.e. a linguistic and a non-linguistic component, are simultaneously involved. This test consists of naming as quickly as possible the print colour of the target words presented on the computer screen. In order to perform this task, participants have to inhibit a highly automatic linguistic process (reading) to permit the activation of a less automatic process (colour naming). Two behavioural experiments were designed. In Experiment 1, twenty highly proficient late French-German bilingual adults, all native speakers of French and right-handed, were selected. Participants were matched with respect to (1) Age of Acquisition of the second language (L2, German), (2) Proficiency Level in L2, and (3) Degree of Exposure to L2. All bilinguals have started formal training in German in French secondary school. In Experiment 2, twenty right-handed monolingual adults, all native speakers of French were recruited. Participants of both groups were asked to perform a manual version of the Stroop task, i.e. they have to indicate the print colour of the target words. Preliminary data indicate that the size of the Stroop interference effect is smaller in bilinguals than in monolinguals. This finding reinforces the idea that a mechanism ‘trained’ to control language use may have an impact on the realisation of a cognitive task involving executive functions.