Neural Responses to Code-Switching: An EEG Study

Bilingual language processing is complex, and it is yet to be explored in its full extent. Previous research suggests that bilinguals’ first- and second-language mental lexicons are interconnected, but the nature and extent of this relationship remain a matter of debate. One of the best indicators of this highly dynamic relationship between the two languages is code-switching. Although from the speaker’s perspective, these switches are merely changes in form in order to substitute a word that is momentarily unavailable in the base language, for the listener, such changes can cause significant processing difficulties. This study examines the neural responses of Swedish-English sequential bilinguals to code-switching and compares these responses to those elicited by semantically incongruent words. This comparison provides a deeper understanding of whether code-switching is processed as a mere change in form or as a shift in meaning, and the results also bring us closer to understanding the relationship between the representations of the first and second language mental lexicons. The study is based on EEG/ERP methodology and focuses primarily on the N400 time window. The results clearly reinforce previous findings supporting a dynamic relationship between first and second languages. Furthermore, they highlight that processing code-switching requires greater cognitive effort than processing simple, within-language semantic anomalies. The study also provides evidence for a LAN-like code-switching effect, which appears independently of morphological violations.