Feature-specific transition from positive mismatch response to mismatch negativity in early infancy: mismatch responses to vowels and initial consonants.

This study investigated how phonological saliency, deviance size, and maturation affect mismatch responses (MMRs) in early infancy. MMRs to Mandarin vowels and initial consonants were measured using a multi-deviant oddball paradigm in adults, newborns, and 6-month-olds. The vowel condition consisted of Mandarin syllable da as the standard, du as the large deviant and di as small deviant. As for initial consonant condition, we took syllable ba as standard, ga as large deviant, and ba as small deviant. While adults showed typical mismatch negativities (MMNs), newborns demonstrated broad positive MMRs (P-MMRs) to both initial consonants and vowels. For 6-month-olds, deviance size affected the polarity of MMRs to vowels. The large deviant du/da contrast elicited an adult-like MMN, while the small deviant di/da contrast elicited a P-MMR. Initial consonant changes elicited only P-MMRs, regardless of deviance size. In summary, MMRs to vowels switched from P-MMR at birth to MMN at 6 months. However, the polarity transition was not found for MMRs to initial consonants. The developmental trajectories of MMRs to vowels and initial consonants further support the phonological saliency hypothesis.