The developmental course of lexical tone perception in the first year of life.

Perceptual reorganisation of infants' speech perception has been found from 6 months for consonants and earlier for vowels. Recently, similar reorganisation has been found for lexical tone between 6 and 9 months of age. Given that there is a close relationship between vowels and tones, this study investigates whether the perceptual reorganisation for tone begins earlier than 6 months. Non-tone language English and French infants were tested with the Thai low vs. rising lexical tone contrast, using the stimulus alternating preference procedure. Four- and 6-month-old infants discriminated the lexical tones, and there was no decline in discrimination performance across these ages. However, 9-month-olds failed to discriminate the lexical tones. This particular pattern of decline in nonnative tone discrimination over age indicates that perceptual reorganisation for tone does not parallel the developmentally prior decline observed in vowel perception. The findings converge with previous developmental cross-language findings on tone perception in English-language infants [Mattock, K., & Burnham, D. (2006). Chinese and English infants' tone perception: Evidence for perceptual reorganization. Infancy, 10(3)], and extend them by showing similar perceptual reorganisation for non-tone language infants learning rhythmically different non-tone languages (English and French).