Rest and sleep effects on speech motor learning (van Zelst & Earle, 2024)

Purpose: Here, we examine the possibility that memory consolidation during a period of postpractice rest or nocturnal sleep can bolster speech motor learning in the absence of additional practice or effort.

Method: Using web-administered experiments, 74 typical, American English talkers trained in a nonnative vowel contrast then had a 12-hr delay with (SLEEP) or without nocturnal sleep (REST) or proceeded immediately (IMMEDIATE) to a posttraining production assessment. For ecological validity, 51 native Danish talkers perceptually identified the American English talkers’ productions.

Results: We observed that practice resulted in productions that were more acoustically similar to the Danish target. In addition, we found that rest in the absence of further practice reduced the token-to-token variability of the productions. Last, for vowels produced immediately following training, listeners more accurately identified vowels in the trained context, whereas in the untrained context, listener accuracy improved only for vowels produced by talkers who slept.

Conclusions: A single session of speech motor training promotes observable change to speech production behavior. Specifically, practice facilitates acoustic similarity to the target. Moreover, although a 12-hr postpractice period of rest appears to promote productions that are less variable, only the productions of those who slept are perceived as more accurate by listeners. This may point to sleep’s role in contextualizing the acoustic goal of the production to the learner’s own vocal tract and its role as a protective mechanism during learning. These results are unaccounted for under existing models and offer potential for future educational and clinical applications to maximize speech motor learning.

Supplemental Material S1. Perceptual tasks and the discrimination and identification of the nonnative Danish vowel targets at baseline and posttraining time points.

Supplemental Material S2. Experiment 1 and 2 data analyses utilizing a subset of only cisgender women participants.

van Zelst, A. L., & Earle, F. S. (2024). A matter of time: A web-based investigation of rest and sleep effects on speech motor learning. Journal of Speech, Language, and Hearing Research, 67(1), 59–71. https://doi.org/10.1044/2023_JSLHR-22-00309