[PS-1.4] Deviant Size Effect on Developmental Trajectory of Mismatch Responses to Mandarin Lexical Tones in Infancy

Cheng, Y. 1 & Lee, C. 2

1 Aim for the Top University Project, National Taiwan Normal University, Taiwan
2 Institute of Linguistics, Academia Sinica, Taiwan

Mismatch negativity (MMN) is an auditory even-related potential (ERP) component indexing automatic change detection. MMN could be elicited without attending to stimuli, therefore is an excellent tool for studying infants? speech perception. However, some literatures have reported positive mismatch responses (P-MMR) rather than MMN, especially for younger infants or smaller deviances. This study explored how deviant size modulates developmental trajectories of mismatch responses (MMRs) to Mandarin lexical tone in early infancy. MMRs to large deviant Tone1/Tone 3 (T1/T3) and small deviant Tone2/Tone3 (T2/T3) contrasts were measured by multi-deviant oddball paradigm at newborns, 6-, 12-, 18- and 24-month-olds. Results showed T1/T3 contrast elicited P-MMR in newborns and elicited adult-like MMN in 6-, 18- and 24-month-olds. T2/T3 contrast elicited P-MMR in 6-, 12- and 18-month-olds, but no P-MMR was found in 24-month-olds. Our findings showed MMRs switch from P-MMR to MMN with age, while the switching occurs later for smaller deviance. It suggested detection of large lexical tone change achieved automaticity as young as 6 months, whereas processing of small lexical tone change could require a distinct neural mechanism in infancy. The phonological representation of lexical tone is in progress of refining at 2 years of age.