Bilingualism enhances cognitive flexibility; Evidence from ERP-pupil size correlations

Kuipers, J. R. & Thierry, G.

Psychology department, Bangor University

A Bilingual upbringing has been shown to enhance executive control, but the neural mechanisms underpinning such effect are essentially unknown. We investigated whether monolingual and bilingual toddlers differ in semantic processing efficiency and their allocation of attention to expected and unexpected visual stimuli. We simultaneously recorded event-related brain potentials (ERPs) and pupil size in monolingual and bilingual toddlers presented with (spoken) word-picture pairs. ERP effects elicited by semantic relatedness were indistinguishable between the two children groups, showing that a bilingual upbringing does not affect the capacity and timing of semantic processing. However, pictures unrelated to the preceding word evoked greater pupil dilation than related pictures in bilinguals, but not in monolinguals. This suggests that the monolingual children seemed to allocate more attention to unrelated, hence unexpected, pictures. Furthermore, time-step correlation analyses between ERP amplitude and pupil dilation showed significant correlations in the time window associated with semantic integration in the unrelated condition only. Importantly however, this correlation was positive in the bilingual children and negative in the monolingual children. Hence, attention to unexpected visual stimuli seems to facilitate semantic integration in bilinguals (smaller N400 amplitude associated with larger pupil dilation) whereas it hampered semantic integration in monolinguals (larger N400 amplitudes associated with larger pupil dilation). These results suggest that bilingual toddlers are more tolerant to variation in word-referent mappings in that they can allocate attention to unexpected stimuli resulting in more efficient semantic integration.