Research (2025): Rhythms of speech: exploring timing mechanisms in stuttering

Research (2025): Rhythms of speech: exploring timing mechanisms in stuttering Chapter 4 explores **consonant-vowel (CV)** timing and predictive timing in adult PWS and adult PWNS via EMA. CV-timing was assessed using both static and dynamic articulatory measures. PWS generally showed greater overlap between CV gestures. Analyses based on the dynamic approach revealed group differences in the unpaced but not rhythmic conditions (Tapping, Metronome, Metronome+Tapping). Moreover, tapping behavior in the Metronome+Tapping condition diverged between groups: PWS tapped closer to speech onset, while PWNS shifted taps toward the metronome beat. **Conclusion:** These findings support the idea that PWS rely more on internal motor cues (e.g., tapping) than external auditory cues (e.g., metronome) and that their CV-timing aligns more closely with that of PWNS when speaking in rhythmic contexts. In sum, this dissertation reveals developmental and rhythmic-context-dependent differences in speech motor control between PWS and PWNS. While rhythmic pacing improves CV-timing in adults who stutter, it does not normalize timing in children, pointing to developmental constraints. Furthermore, PWS exhibit altered auditory-motor integration and predictive timing, with a tendency to rely on internally generated cues. These results offer novel insights into articulatory timing in stuttering and contribute to broader models of speech motor control. **Interpretations** * **Children & adolescents:** those who stutter (PWS) showed *greater consonant compression* (different onset–vowel timing) than controls; metronome pacing improved stability somewhat but **did not normalize** onset–vowel timing in the developing group * **Adults:** PWS exhibited **closer CV coupling** (more overlap of consonant and vowel gestures) in unpaced speech; under rhythmic conditions (tapping or metronome) CV-timing of PWS and controls became similar. * **Predictive timing & auditory–motor integration** * PWS showed altered **predictive timing**: when synchronising to a metronome they aligned speech onsets closer to the beat than controls (consistent with delayed/initiation differences). PWS were *more variable* when aligning to an external auditory beat but not when aligning to their own finger tapping. This pattern supports **auditory–motor integration** difficulties and altered predictive timing in PWS. * **Role of internal vs external cues** * The data suggest PWS rely relatively more on **internally generated cues** (e.g., finger taps / somatosensory signals) while PWNS rely more on external auditory cues (metronome). Finger tapping can stabilize internal timing for PWS (i.e., tapping helps couple speech timing), whereas the metronome drives PWNS more strongly. * **Theoretical implications** * Findings are interpreted as consistent with **impaired/less reliable feedforward (predictive) timing** and altered sensorimotor integration in PWS. * **Rhythm & development** * Rhythm (external pacing) **improves** articulatory timing for adults who stutter but **does not fully normalize** articulatory timing in children — suggesting developmental constraints on how rhythmic cues are used by the speech motor system. **Rhythm may act as an external pacemaker that partially compensates for unreliable internal timing in adults.** * **Bottom-line (author’s conclusion on these pages)**