Role of talker variability in L2 learning (Zhang et al., 2021)

Purpose: High-variability phonetic training (HVPT) has been found to be effective on adult second language (L2) learning, but results are mixed in regards to the benefit of multiple talkers over single talker. This study provides a systematic review with meta-analysis to investigate the talker variability effect in nonnative phonetic learning and the factors moderating the effect.

Method: We collected studies with keyword search in major academic databases including EBSCO, ERIC, MEDLINE, ProQuest Dissertations & Theses, Elsevier, Scopus, Wiley Online Library, and Web of Science. We identified potential participant-, training-, and study-related moderators and conducted a random-effects model meta-analysis for each individual variable.

Results: On the basis of 18 studies with a total of 549 participants, we obtained a small-level summary effect size (Hedges’ g = 0.46, 95% confidence interval [CI; 0.08, 0.84]) for the immediate training outcomes, which was greatly reduced (g = −0.04, 95% CI [−0.46, 0.37]) after removal of outliers and correction for publication bias, whereas the effect size for immediate perceptual gains was nearly medium (g = 0.56, 95% CI [0.13, 1.00]) compared with the nonsignificant production gains. Critically, the summary effect sizes for generalizations to new talkers (g = 0.72, 95% CI [0.15, 1.29]) and for long-term retention (g = 1.09, 95% CI [0.39, 1.78]) were large. Moreover, the training program length and the talker presentation format were found to potentially moderate the immediate perceptual gains and generalization outcomes.

Conclusions: Our study presents the first meta-analysis on the role of talker variability in nonnative phonetic training, which demonstrates the heterogeneity and limitations of research on this topic. The results highlight the need for further investigation of the influential factors and underlying mechanisms for the presence or absence of talker variability effects.

Supplemental Table S1. PRISMA checklist.

Supplemental Table S2. Characteristics of studies included in quantitative synthesis.

Supplemental Table S3. Overall benefit of talker variability.

Supplemental Table S4. Effects of talker variability on generalization and retention.

Supplemental Table S5. Results of the meta-regression analyses on immediate perceptual gains.

Supplemental Table S6. Results of the meta-regression analyses on generalization outcomes.

Zhang, X., Cheng, B., & Zhang, Y. (2021). The role of talker variability in nonnative phonetic learning: A systematic review and meta-analysis. Journal of Speech, Language, and Hearing Research. Advance online publication. https://doi.org/10.1044/2021_JSLHR-21-00181