Mismatch responses to lexical tone, initial consonant, and vowel in Mandarin-speaking preschoolers.

The present study investigates how age, phonological saliency, and deviance size affect the presence of mismatch negativity (MMN) and positive mismatch response (P-MMR). This work measured the auditory mismatch responses to Mandarin lexical tones, initial consonants, and vowels in 4- to 6-year-old preschoolers using the multiple-deviant oddball paradigm. The data showed the coexistence of MMN and P-MMR in the same age group when responding to the three types of syllabic features in Mandarin. The transition from a predominantly positive response to a predominantly negative response supported the multiple MMN mechanisms. Congruent with the phonological saliency hypothesis and the phonetic acquisition order of Mandarin in behavioral studies, for the compulsory elements of Mandarin syllables, lexical tones, and vowels, the larger deviants elicited adult-like MMNs, whereas the smaller deviants elicited P-MMRs. The optional elements of the Mandarin syllables, the initial consonant, only elicited P-MMR in preschoolers. These findings suggest that MMN and P-MMR index different functional characteristics and may provide information on when and how children's speech perception becomes automatic at different developmental stages.