Second language processing: electrophysiological studies and data analysis methods

To what extent, and under which circumstances, is it possible to reach the same level as a native speaker when learning a second language? This dissertation addresses some aspects of this question, using experiments in which the electrical activity of the brain (EEG) of second language speakers was measured and innovative data analysis methods were applied. Participants in the experiments were second language speakers of Dutch with a Romance language background (e.g., Spanish) and second language speakers of German with a Slavic language background (e.g., Polish). They listened to sentences with incorrect use of grammatical gender (‘de/het’ in Dutch; ‘der/die/das’ in German), after which their brain signal was compared to that of native speakers to reveal unconscious cognitive processing mechanisms. The results argue against the existence of a critical period for learning a second language, and show how the first language can influence the second language. These results are based on so called ‘generalised additive modelling’ (GAM) analyses, which reveal patterns that would have remained hidden with traditional EEG analysis techniques, thus highlighting the importance of using adequate statistical techniques that do not lose information by averaging. In addition, this dissertation introduces a new set of (GAMs-based) measures with which individual differences in the EEG signal of second-language speakers can be studied. The present dissertation therefore does not only aim at advancing our understanding of second language acquisition, but also makes a methodological contribution to analysing the underlying neurocognitive mechanisms.