Lexical-semantic processing costs are not inherent to intra-sentential code-switching: The role of switching habits.

A bank of past electrophysiological research suggests that code-switching (i.e., the use of multiple languages during a single conversational event) is characterized by increased processing costs. However, the majority of these studies tested bilinguals who did not necessarily code-switch on a regular basis. In order to investigate the impact of switching habits on language processing, two groups of French-English bilinguals (habitual code-switchers and non-habitual code-switchers) read sentences containing unilingual and switched determiner phrases while their EEG was recorded. The findings indicate important processing differences between the groups. Notably, switched trials (particularly those with a French determiner) generated an increased negativity from 300 to 500 ms for non-habitual code-switchers, but not for habitual code-switchers. The veritable impact of switching habits were also supported by a correlation analysis. This finding suggests that code-switching is not inherently effortful to process, but rather, that comprehension costs are related to idiosyncratic factors, such as the extent of prior exposure to code-switched input. An LPC was also observed from 500 to 900 for habitual code-switchers; for non-habitual switchers, this effect may have been attenuated by the long-lasting N400 effect. We advance several possible interpretations for the late positivity. Altogether, the results from the current study support the claim that the code-switching cost observed in previous literature may be linked to the bilingual samples tested in those studies: habitual code-switchers may not find switches effortful to process, but not all bilinguals code-switch. We highlight the importance of experience and individual differences in the study of bilingual cognition.