Auditory feedback control in adults who stutter during metronome-paced speech II. Formant Perturbation.

Only 31 adults participated, and the study used one target sentence plus filler sentences, so it may not reflect everyday speech. The stuttering group included adults only, and the authors note that results may reflect long-standing adaptive behaviours rather than core stuttering mechanisms. Trials with unambiguous stutters were removed from the perturbation analysis, and the overall stutter rate was low, so the feedback responses were measured in relatively fluent speech. The earphone feedback had a delay of 24 to 32 ms, and delayed auditory feedback itself can improve fluency, so the metronome effect may be partly a feedback delay effect. There was a latency difference between perturbed trials (24 ms) and unperturbed trials (32 ms), although the authors say it was consistent across groups and speaking conditions. The formant response was not a simple main effect of pacing or group; only an interaction was significant, and exploratory timepoint tests were uncorrected. One participant completed 200 trials instead of 240 because of a technical error. One adult who stutter had a severity score below the manual threshold but was included because they identified as a person who stutters.

All authors declare no competing interests. The article is listed as supported by N.I.H. Extramural research support.

Do not conclude that metronome pacing is an effective stuttering therapy or that it fixes auditory feedback control. The study used one sentence with artificial formant shifts in a lab, and the response pattern was a group by condition interaction, not a straightforward improvement in adults who stutter.