Event-related Potentials as Metrics of Foreign Language Learning and Loss

We report here a study of adult first language (L1) English speakers who were enrolled in a university course of second language (L2) Finnish instruction. We investigated the acquisition and retention of the phonotactic Finnish Vowel Harmony rule. Event-Related Potentials (ERPs) were recorded while learners read a list of Finnish words and word-like non-words, some of which violated vowel harmony. ERPs were recorded near the beginning, middle, and end of the instructional period, and during a post-instruction language attrition session. The violations elicited an N400 effect during early stages of learning and a P600 effect after additional instruction. Conversely, violations elicited a P600 after short attrition periods and an N400 after longer periods. Our results support a processing-based version of the regression hypothesis: learners gradually transitioned from a lexical processing mode to a grammatical processing mode during the acquisition phase, with the reverse transition occurring once instruction has ended.