Dehaene-Lambertz, G., Dupoux, E., & Gout, A. (2000). Electrophysiological correlates of phonological processing: a cross-linguistic study. Journal of Cognitive Neuroscience, 12, 635-647. It is well-known that speech perception is deeply affected by the phoneme categories of the native language. Recent studies have found that phonotactic rules, that is, constraints on the co-occurrence of phonemes within words, also have a considerable impact on speech perception routines. For example, syllabic structures in Japanese do not allow (non-nasal) coda consonants. When presented with stimuli that violate this constraint, as in /ebzo/, Japanese adults report that they hear a /u/ between consonants, that is, /ebuzo/. We examine this phenomenon using event-related potentials (ERPs) on French and Japanese participants in order to study how and when the phonotactic properties of the native language affect speech perception routines. Trials using four similar precursor stimuli were presented followed by a test stimulus that was either identical or different depending on the presence or absence of an epenthetic vowel /u/ between two consonants (for example, "ebuzo ebuzo ebuzo - ebzo"). Behavioral results confirm that Japanese, unlike French participants, are not able to discriminate between identical and deviant trials. In ERPs, three mismatch responses were recorded in French participants. These responses were either absent or significantly weaker for Japanese. In particular a component similar in latency and topography to the mismatch negativity (MMN) was recorded for French, but not for Japanese participants. Our results suggest that the impact of phonotactics takes place early in speech processing and support models of speech perception that postulate that the input signal is directly parsed into the native language phonological format. We speculate that such a fast computation of a phonological representation should facilitate lexical access, especially in degraded conditions.