Talker variability has been reported to facilitate generalization and retention of speech learning, but is also shown to place demands on cognitive resources. Our recent study provided evidence that phonetically-irrelevant acoustic variability in single-talker (ST) speech is sufficient to induce equivalent amounts of learning to the use of multiple-talker (MT) training. This study is a follow-up contrasting MT versus ST training with varying degrees of temporal exaggeration to examine how cognitive measures of individual learners may influence the role of input variability in immediate learning and long-term retention. Native Chinese-speaking adults were trained on the English /i/-/ɪ/ contrast. We assessed the trainees’ working memory and selective attention before training. Trained participants showed retention of more native-like cue weighting in both perception and production regardless of talker variability condition. The ST training group showed long-term benefit in word identification, whereas the MT training group did not retain the improvement. The results demonstrate the role of phonetically-irrelevant variability in robust speech learning and modulatory functions of nonlinguistic working memory and selective attention, highlighting the necessity to consider the interaction between input characteristics, task difficulty, and individual differences in cognitive abilities in assessing learning outcomes.

While native English speakers have been found to primarily use vowel spectrum on /i/-/ɪ/ perception, Chinese learners of English dominantly use vowel duration. This study examined training effects on cue reweighting in perceiving /i/-/ɪ/ by Chinese learners. We modified the canonical HVPT paradigm with introducing variability along the secondary dimension for the contrast distinction (i.e., duration). Forty native Chinese-speaking adults were randomly assigned to two groups: the training group and the control group. Pre- and post- training tests used the tasks of natural word identification and synthetic phoneme identification. Synthesized phoneme stimuli were the two-dimensional (spectrum and duration) stimulus continua ranging from English /i/ to /ɪ/, and the natural word stimuli included both trained and untrained words produced by novel talkers. The results demonstrated that the training group showed more reliance on the primary spectral cue and less reliance on the secondary durational cue after training. The corroborating data from the word identification showed the training group improved significantly and generalized learning to new talkers and phonetic contexts. The control group did not show similar changes. These results indicated that high variability phonetic training is effective on helping L2 learners to retune attention to primary cues which facilitate generalization outcomes.

This study aims to examine effects of the disyllabic tonal context on native Chinese speakers' cue weighting for perceiving and producing target Mandarin Tone 2 and Tone 3 that share similar pitch contours. The speech materials were disyllabic Mandarin words, matched by word frequency and familiarity. Acoustic manipulations for the perception test included four key parameters, including fundamental frequency (F0) at tone onset, F0 at turning point, the timing of turning point and F0 at tone offset, which characterized the pitch contours of Tone 2 and Tone 3. Thirty native Chinese speakers participated in this study. These synthetic disyllabic stimuli were used in an identification task. Production of the target tones in the disyllabic context was also recorded from each participant. Cue weights for the key acoustic parameters were assessed with logistic regression analyses and linear discriminant analyses to model the extent to which each acoustic cue predicted category membership in the perception and production data. The results demonstrated strong perceptual weighting sensitivity to the disyllabic context in native Chinese speakers. The results are discussed with respect to the dynamics of tone perception and production in word contexts and potential implications for Chinese as a second language learners.