The role of motor learning in stuttering adaptation: Repeated versus novel utterances in a practice–retention paradigm

Abstract

Most individuals who stutter become more fluent during repeated oral readings of the same material. This adaptation effect may reflect motor learning associated with repeated practice of speech motor sequences. We tested this hypothesis with a paradigm that used two integrated approaches to identify the role of motor learning in stuttering adaptation: to distinguish practice effects from situation effects, the texts contained both repeated and novel sentences; to differentiate learning effects from temporary performance effects, stuttering frequency was determined for both the initial adaptation readings and retention tests after 2 h and 24 h. Average group data for 7 stuttering individuals who showed adaptation indicate that (a) both repeated and novel sentences resulted in decreased stuttering frequency across five readings in the initial session, but the decrease was larger for repeated than for novel sentences; (b) after 2 h, stuttering frequency for both types of sentences was again similar, but with additional readings the repeated sentences once again showed larger improvements in fluency; (c) after 24 h, prior fluency improvements for the novel sentences had dissipated whereas retention was observed for the repeated sentences. These findings – supporting the hypothesis that motor learning plays a role in stuttering adaptation – were representative for most, but not all, individual subjects. Subjects whose data did not follow the group trend and showed comparable retention for repeated and novel sentences may adapt primarily on the basis of non-motor mechanisms. Alternatively, those subjects may in fact show more substantial generalization of motor learning effects to previously unpracticed movement sequences. Educational objectives: After reading this article, the reader will be able to: (1) summarize previous research on stuttering adaptation; (2) define motor learning and describe its essential characteristics; and (3) discuss why the results from this and previous studies suggest that stuttering adaptation may be a result of motor learning.