The Neurophysiological Modality Effect in Native and Second Language Processing: An ERP Study

Experimental psychology has long discussed the modality effect, whereby the stimulus modality significantly affects retention of the information presented. In neurolinguistics, however, the effect of stimulus modality on language processing has gained little attention. We conducted a multi-modal event-related potential (ERP) experiment on both native and non-native Spanish speakers to investigate the possibility of a neurophysiological modality effect in language processing. Using morphosyntactically violated and orthographically/phonologically violated stimuli, we elicited a robust N400 and P600 in native speakers. We showed that the N400 has consistent features across modalities, while the P600 has modality-specific features. Specifically, the auditory evoked P600 was characterized by a more gradual slope and a later peak than the visual evoked P600. We discuss this in detail along with other modality effects observed post sensory perception. Among second language (L2) learner groups, those with higher proficiency exhibited more nativelike neurophysiological responses in both modalities when compared to those with lower proficiency. We additionally observed fewer modality-specific differences in low proficiency learners than in higher proficiency learners suggesting that modality-specific specialization in language processing comes with increased proficiency. We further discuss the question of modality-specific differences in the process of neurophysiological nativization, whereby L2 learners ERPs become increasingly on nativelike.