Differential Effects of Stimulus Variability and Learners’ Pre-existing Pitch Perception Ability in Lexical Tone Learning by Native English Speakers

We examined the role of stimulus variability in learning non-native phonetic contrasts (suprasegmentals) for word identification by adults, considering whether all learners benefit from high-variability training. Forty-seven English-speakers were trained to use Mandarin lexical tones to identify 18 English pseudowords with stimuli produced by either four talkers (multitalker training) or only one of the four talkers (single-talker training). Subjects’ pre-training ability to identify the pitch patterns in a non-lexical context was also measured. Subjects with high pitch-identification ability learned more successfully than those with lower pitchidentification ability. Importantly, multi-talker training was beneficial only for learners with high pitch-identification ability, whereas learners with low pitch-identification ability benefited more from single-talker training. These findings provide support for phonetic-phonology continuity in adult sound-to-word learning and suggest that in order for high-variability training to be beneficial, learners first need to be able to successfully encode phonetic details.