Many aspects of a new language, including grammar rules, can be acquired and accessed within minutes. In the present study, we investigate how initial learners respond when the rules of a novel language are not adhered to. Through spoken word-picture association-learning, tonal and non-tonal speakers were taught artificial words. Along with lexicosemantic content expressed by consonants, the words contained grammatical properties embedded in vowels and tones. Pictures that were mismatched with any of the words’ phonological cues elicited an N400 in tonal learners. Non-tonal learners only produced an N400 when the mismatch was based on a word's vowel or consonants, not the tone. The emergence of the N400 might indicate that error processing in L2 learners (unlike canonical processing) does not initially differentiate between grammar and semantics. Importantly, only errors based on familiar phonological cues evoked a mismatch-related response, highlighting the importance of phonological transfer in initial second language acquisition.
