An Adaptation Effect in Bilingual Adults Who Stutter Suggests Their Motor Learning is Influenced by Language Factors

Stuttering is progressively reduced when persons who stutter repeatedly read the same text. This reduction has been recently attributed to motor learning with repeated practice of speech-motor sequences. In the present study, we investigated the adaptation effect of 17 bilingual adults who stutter (BAWS). We asked these participants to complete a particular paradigm of reading passages with a 30-minute break between them. Participants were Kannada-English speaking BAWS. We split them into two groups of eight and nine participants, respectively who read in counter-balanced order two passages written in the Kannada and English languages. The averaged data from the two groups resulted in a typical adaptation curve for the five readings when read separately in both languages. When there was a switch from readings in Kannada to readings in English, there was a significant increase in the percentage of syllables stuttered. This increase in dysfluencies reduced the adaptation effect from repeated reading. These findings support the hypothesis that motor learning plays a crucial role in stuttering adaptation when participants read the same passage repeatedly in any language, but the shift in the language read suggests an interference in motor learning. Collectively, our results highlight an interaction effect between motor learning and language proficiency, seen by increased dysfluencies and a reduced adaptation effect in bilingual speakers.