Effects of Practice Variability on Second-Language Speech Production Training.
Lindsay Bu, Marisa Nagano, Daphna Harel and 1 others
PMID 33070129WHAT IT FOUND
High-variability practice improved short-term accuracy within sessions, but long-term retention was poor for most participants.
Only one person showed clinically meaningful change after four weeks. Use with caution for lasting speech modification.
Key findings
01Participants in the high-variability group showed significant improvement in acoustic accuracy from the start to the end of training sessions, whereas the low-variability group did not.
02Long-term retention was limited; there was no significant difference in acoustic accuracy between the two groups over the course of the study, and only one participant achieved a functionally relevant effect size.
03The study cannot determine the effectiveness of the tactile feedback device because all participants used it and there was no control group without it.
STILL TO COME
How it was doneWhat they foundWhat it means for SLPs
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What it does not show
The sample size was very small (n=8), limiting the generalizability of the findings. The study lacked a control group that did not use the tactile feedback device, so it is impossible to separate the effect of the variability practice from the effect of the device. Long-term retention was poor for most participants, suggesting the four-week intervention was insufficient to create lasting change. All measurements were acoustic; the study did not assess how native English speakers perceived the clients' speech, which is a key functional outcome. The training dose was low (60 trials per session), which may have been insufficient to drive motor learning and retention.
Declared interests
The authors received complimentary 'R buddy' devices from Speech Buddies, Inc. to support the research. No other conflicts of interest were declared.
The easy way to misread this
Do not conclude that the tactile feedback device caused the improvement. All participants used the device, so its specific contribution cannot be separated from the practice variability manipulation. Additionally, do not assume that short-term gains within a session translate to long-term speech change, as most participants showed no meaningful retention.