A neural network simulation of event-related potentials in response to syntactic violations in second-language learning

Event-related potentials (ERPs) are used to study how language is processed in the brain, including differences between native (L1) and second-language (L2) comprehension. In low proficiency L2 learners, syntactic violations give rise to an N400, but this changes into a P600 as their L2 proficiency increases. The precise functional interpretation of ERPs, however, remains a matter of debate. Fitz and Chang (2019) proposed a theory where ERPs reflect learning signals that arise from mismatches in predictive processing. These signals are propagated across the language system to make future predictions more accurate. We test if this theory can account for the N400-to-P600 switch in late bilinguals, by implementing a model capable of simulating the N400 and P600. We perform an experiment designed to elicit a P600 effect in simulated L2 learners progressing through learning stages. Simulated Spanish-English participants showed similar ERP effects in their L2 (English) as human participants did in ERP studies. Over the course of L2 learning, simulated N400 size decreased while P600 size increased, as it does in humans. Our findings support the viability of error propagation as an account of ERP effects, and specifically of how these can change over L2 learning.