ERPs have also been used to address a number of important issues in the area of bilingual language processing, including questions about critical periods, effects of language proficiency and dominance, relationships between a bilingual’s two languages, and effects of code-switching, among others (reviewed in Kutas et al 2009). N400 semantic priming and sentence congruity effects have been reported for more than a dozen languages in both monolinguals and bilinguals, with no evidence that N400s differ in their timing or topography as a function of specific language characteristics or writing systems. N400 parameters, however, are sensitive to an individual’s proficiency with a language, even if they know only one, making them an excellent tool for investigating competence in adult second language acquisition. McLaughlin et al. (2004), for instance, showed that N400 amplitude reductions could distinguish words from pseudowords with only 14 hours of classroom instruction in a second language, and semantically related words from unrelated ones with as little as 63 hours. These reliable N400 effects were accompanied by chance level overt word and relatedness judgments, highlighting the sensitivity of ERP
