Using event-related potentials (ERPs), we investigated the impact of a range of individual difference measures related to L2 learning on proficient L1 Spanish – L2 English bilinguals’ brain responses during L2 morphosyntactic processing. Although grand mean ERP analyses revealed a biphasic N400–P600 response to English subject–verb agreement violations, subsequent analyses showed that participants’ brain responses varied along a continuum between N400- and P600-dominance. To investigate this pattern, we introduce two novel ERP measures that independently quantify relative brain response type and overall magnitude. Multivariate analyses revealed that larger overall brain responses were associated with higher L2 proficiency, while relative brain response type (N400 or P600) was predicted by a coalition of variables, most notably learners’ motivation and age of arrival in an L2 environment. Our findings show that aspects of a learner's background can differentially impact a learner's overall sensitivity to L2 morphosyntax and qualitative use of linguistic cues during processing.

Here we report findings from a cross-sectional study of morphosyntactic processing in native German speakers and native English speakers enrolled in college-level German courses. Event-related brain potentials were recorded while participants read sentences that were either well-formed or violated German subject–verb agreement. Results showed that grammatical violations elicited large P600 effects in the native Germans and learners enrolled in third-year courses. Grand mean waveforms for learners enrolled in first-year courses showed a biphasic N400–P600 response. However, subsequent correlation analyses revealed that most individuals showed either an N400 or a P600, but not both, and that brain response type was associated with behavioral measures of grammatical sensitivity. These results support models of second language acquisition which implicate qualitative changes in the neural substrates of second language grammar processing associated with learning. Importantly, we show that new insights into L2 learning result when the cross-subject variability is treated as a source of evidence rather than a source of noise.

Pulvermüller advocates an experimental design in which well-matched tokens from various word categories are presented in list form to subjects making rapid lexical decisions about these stimuli. Implicit in this paradigm are several problematic assumptions. We conclude that such experiments are not likely to tell us much about the biological bases of human language.