Infants' sensitivity to lexical tone and word stress in their first year : a Thai and English cross-language study

Non-tone language infants' native language recognition is based first on supra-segmental then segmental cues, but this trajectory is unknown for tone-language infants. This study investigated non-tone (English) and tone (Thai) language 6- to 10-month-old infants' preference for English vs. Thai one-syllable words (containing segmental and tone cues) and two-syllable words (additionally containing stress cues). A preference for their native one-syllable words was observed in each of the two groups of infants, but this was not the case for two-syllable words where Thai-learning infants showed no native-language preference. These findings indicate that as early as six months of age, infants acquiring tone- and non-tone languages identify their native language by relying solely on lexical tone cues, but tone language infants no longer show successful identification of their native language when two pitch-based cues co-occur in the signal.