Can infant-directed speech facilitate lexical tone identification by L2 non-tonal language learners of Mandarin Chinese?

Abstract

This study explores whether infant-directed speech (IDS) facilitates Mandarin lexical tone identification by L2 learners who are native in non-tonal language. Experiment is conducted to test three hypotheses: (1) Mandarin lexical tones in IDS are undistorted and phonetically enhanced; (2) IDS can facilitate tone identification by adult Mandarin learners whose native language is non-tonal; (3) Certain Mandarin lexical tone(s) can be more difficult for learners to identify. A native Mandarin mother participated in the recording to provide IDS and adult-directed speech (ADS) stimuli for the experiment. Then, a Mandarin tone identification task was conducted to examine the performance of L2 Mandarin learners as well as native speakers on IDS stimuli and ADS stimuli respectively. To test the first hypothesis, acoustic analysis was made to compare critical acoustic features of Mandarin tones in IDS and ADS. For second and third hypotheses, accuracy rate and reaction time (RT) of participants from the experiment was analyzed. The results indicate that critical acoustic cues for Mandarin lexical tone perception were preserved and phonetically exaggerated in IDS, which contributes to higher accuracy and shorter processing time of tone identification for native Mandarin speakers. For Mandarin L2 learners, though no overall significant facilitation of IDS was found, IDS did help them to perform better on certain tone (i.e. Tone 3). Significant difference between tone patterns was also found. Tone 3 identification was overwhelmingly harder for all participants, comparing to other three tones.