Comparing ERPs between native speakers and second language learners: Dealing with individual variability

Event-related potentials (ERPs) are of great interest in second language acquisition research, as they allow us to examine online language processing and to compare themechanisms that are engaged to process a first and second language. A long history of research into native language processing has taught us to expect a biphasic pattern in response to syntactic violations, reflecting mechanisms involved first in the automatic and implicit detection of the incongruity and then in the reanalysis and repair of the ungrammatical sentence. However, recent studies show that there is a large degree of individual variability even among native speakers: Instead of this biphasic pattern, most people exhibit one or the other of the two components. This raises an interesting question for second-language research: How do we compare learners and native speakers if there is no unique native-speaker model to compare learners to? In this chapter, I explore two measures that have been put forward to characterise individual variability among native speakers and language learners, the Response Magnitude Index and the Response Dominance Index (Tanner et al. 2014), and I show an example of their application to a study comparing native-speaker and non-native-speaker processing of morphosyntactic violations using auditory stimuli instead of visual stimuli.