Processing semantic anomalies in two languages: an electrophysiological exploration in both languages of Spanish-English bilinguals

The latency of the brain response to semantic anomalies (N400 effect) has been found to be longer in a bilingual's second language (L2) than in their first language (L1) and/or to that seen in monolinguals. This has been explained in terms of late exposure to L2, although age of exposure and language proficiency are often highly correlated. We thus examined the relative contributions of these factors not only in L2 but also in L1 in a group of Spanish-English bilinguals for whom age of exposure and language proficiency were not highly correlated by recording event-related brain potentials (ERPs) to semantically congruous/incongruous words completing written sentences. We also divided our bilinguals into a Spanish-dominant subset who had late exposure and reduced vocabulary proficiency [as measured by Boston Naming Test (BNT) and Verbal Fluency Scores] in L2 (English) relative to L1 (Spanish) and an English-dominant group who had early exposure to both their languages although greater proficiency in English than in Spanish. In both groups, the N400 effect was significantly later in the nondominant than the dominant language. Although this slowing could be due to late exposure to English in the Spanish-dominant group, late exposure cannot explain the slowing in Spanish in the English-dominant group. Overall, we found that vocabulary proficiency and age of exposure are both important in determining the timing of semantic integration effects during written sentence processing--with vocabulary proficiency predicting the timing of semantic analysis in L1 and both age of exposure and language proficiency, although highly correlated, making additional small but uncorrelated contributions to the speed of semantic analysis/integration in L2.