Twelve-month-old bilingual and monolingual infants show comparable phonetic discrimination skills for vowels belonging to their native language/s. However, Catalan–Spanish bilingual toddlers, but not Catalan monolinguals, appear insensitive to a vowel mispronunciation in familiar words involving the Catalan–Specific /e/-/ɛ/ contrast. Here bilingual and monolingual toddlers were tested in a challenging minimal-pair word learning task involving that contrast (i.e., [bepi]-[bɛpi]). Both groups succeeded, suggesting that bilinguals can successfully use their phonetic categories to phonologically encode novel words. It is argued that bilinguals’ impoverished vowel representations in familiar words might be the result of experiential input factors (e.g., cognate words and mispronunciations due to accented speech).

Learning to speak a new language requires the formation of recognition patterns for the speech sounds specific to the newly acquired language. The present study demonstrates the dynamic nature of cortical memory representations for phonemes in adults by using the mismatch negativity (MMN) event-related potential. We studied Hungarian and Finnish subjects, dividing the Hungarians into a naive (no knowledge of Finnish) and a fluent (in Finnish) group. We found that the MMN for a contrast between two Finnish phonemes was elicited in the fluent Hungarians but not in the naive Hungarians. This result indicates that the fluent Hungarians developed cortical memory representations for the Finnish phoneme system that enabled them to preattentively categorize phonemes specific to this language.