Jeffery A. Jones

Correction depends on more than the size of the error Simple models of feedback control assume that the mismatch between predicted and actual feedback is estimated and the controller corrects errors in proportion to their size. The contributions in this volume complicate that account. Sreedhar and Daliri (2026) exposed speakers to formant perturbations that varied in direction, magnitude, and the extent of exposure. They found larger corrective responses when a perturbation moved a vowel towards a neighbouring natural vowel category. Early in the perturbed trials, compensations were proportionally larger for smaller perturbations. Corrective responses to perturbations towards a neighbouring vowel declined over repeated trials. The speech motor control system thus appears to weight errors by their plausibility as self-generated, not simply by their magnitude. Error processing, in short, seems to hinge on what kind of error occurs, how often it recurs, and whether the system treats it as self-caused rather than externally caused. Gaines et al. (2026) challenged a common assumption: that a speaker who adapts to a specific perturbation will adapt the same way the next time they encounter it. When speakers heard the same 100-cent pitch perturbation across three repetitions within a single session, adaptation fell by 67% from the first repetition to the second and was effectively eliminated by the third, with neither differing significantly from baseline. This attenuation, the authors note, parallels implicit learning in visuomotor reaching tasks, reinforcing the characterization of pitch adaptation as primarily implicit and driven by sensory prediction error. This instability also raises practical concerns for studies that treat adaptation as a reliable individual-difference measure.The physical effort of compensation has received little attention in the literature, but Ronayette et al. (2026) demonstrated that it limits sensorimotor adaptation. Speakers compensating for formant perturbations while holding a deformable lip tube that made lip rounding more effortful reached a plateau in lip-muscle activity at only about 56% of their maximum voluntary contraction, well below the physiological limit. This saturation suggests a comfort threshold rather than a biomechanical ceiling. When lip-rounding effort became too costly, some speakers shifted towards tongue backing, inferred from their formant trajectories. Partial adaptation, usually attributed to other factors, may also reflect effort optimization. Past a point, the larger the error, the more of it goes uncorrected, not because it goes undetected, but because correcting it costs more effort than the system deems it worth.Several contributions in Volume III deepen Volume II's case for somatosensory feedback. Cummine et al. (2026) used fNIRS to compare oral stimulation (a lollipop) with oral anaesthesia (lidocaine) during covert speech, and found greater activity for the stimulation condition in the supramarginal and inferior frontal gyri, both speech regions. Because the role of somatosensory feedback during overt production is already established, the sensitivity of these regions to oral sensation during covert speech suggests that somatosensory processing is engaged when speech is merely planned, not only when it is produced. 2026) compared spontaneous production rates across speaking, singing, tapped melody, and silent tapping. Speaking rate followed the rates of singing and tapped melody, the tasks that produced sound, but not silent tapping. Bayesian analyses provided strong evidence that this dissociation is real, not merely undetected. How fast we speak, then, appears to depend not on the vocal tract, nor on the fact that it is speech, but on whether the action is heard.Two contributions examine sensory feedback in second language acquisition. Suemitsu et al. (2026) trained Japanese speakers to produce an American English vowel using real-time visual feedback of tongue position, with no spoken model to imitate. A single 10-15-minute training session improved not only production accuracy but also perceptual discrimination of the trained contrast, tested afterward. Motor learning transferred to perception without exposure to any native auditory model of the sound, a demonstration of the tight coupling between production and perception. Li et al. (2026) found that for a novel second-language vowel, somatosensory acuity, indexed by a phonetic-awareness task (a measure of explicit articulatory awareness), was the only significant predictor of production accuracy, while auditory acuity was not. Together with the somatosensory findings from Volume II, these studies reinforce the view that feedback control in speech relies on multisensory information.The clinical contributions in this volume each probe a different parameter of the feedback control system by investigating what changes when it is compromised. Daliri et al. (2025) found that delayed auditory feedback increased trial-to-trial formant variability in typically fluent speakers but decreased it in adults who stutter. In stuttering, delayed feedback does not merely have a weaker effect; it reverses the effect, lowering variability rather than raising it. The system may respond more strongly to small, naturally occurring errors in these speakers, and more weakly to the large errors introduced by delaying feedback. What differs in stuttering may be how perceived errors are weighted. Basciano et al. (2025) investigated how individuals with aphasia respond to formant perturbations that are introduced either gradually or suddenly. When the perturbation was introduced gradually, their corrective responses differed from those observed in the control group. This difference disappeared, however, when the perturbation was introduced suddenly. This schedule dependence, the authors suggest, reflects how aphasia affects the detection and attribution of speech errors. Among individuals,...

Children maintain fluent speech despite dramatic changes to their articulators during development. Auditory feedback aids in the acquisition and maintenance of the sensorimotor mechanisms that underlie vocal motor control. MacDonald, Johnson, Forsythe, Plante, and Munhall (2012) reported that toddlers' speech motor control systems may "suppress" the influence of auditory feedback, since exposure to altered auditory feedback regarding their formant frequencies did not lead to modifications of their speech. This finding is not parsimonious with most theories of motor control. Here, we exposed toddlers to perturbations to the pitch of their auditory feedback as they vocalized. Toddlers compensated for the manipulations, producing significantly different responses to upward and downward perturbations. These data represent the first empirical demonstration that toddlers use auditory feedback for vocal motor control. Furthermore, our findings suggest toddlers are more sensitive to changes to the postural properties of their auditory feedback, such as fundamental frequency, relative to the phonemic properties, such as formant frequencies.

Auditory feedback plays an important role in monitoring and correcting for errors during speech production. Previous research suggests that at vocalization onset, auditory feedback is compared to a sensory prediction generated by the motor system to ensure the desired fundamental frequency (F0) is produced. After vocalization onset, auditory feedback is compared to the most recently perceived F0 in order to stabilize the vocalization. This study aimed to further investigate whether after vocalization onset, auditory feedback is used strictly to stabilize speakers’ F0, or if it is also influenced by the sensory prediction generated by the motor system. Event-related potentials (ERP) were recorded while participants produced vocalizations and heard the F0 of their auditory feedback perturbed suddenly mid-utterance by half a semitone. For half of the vocalizations, at vocalization onset, participants’ F0 was also raised by half a semitone. Thus, half of the perturbations occurred while participants heard their unaltered auditory feedback, and the other half occurred in auditory feedback that had also been perturbed 50 cents at vocalization onset. If after vocalization onset auditory feedback is strictly used to stabilize speakers’ F0, then similarly sized vocal and ERP responses would be expected across all trials, regardless of whether the perturbation occurred while listening to altered or unaltered auditory feedback. Results indicate that the perturbations to the participants’ unaltered auditory feedback resulted in larger vocal and N1 and P2 ERP responses than perturbations to their altered auditory feedback. These results suggest that after vocalization onset auditory feedback is not strictly used to stabilize speakers’ F0, but is also used to ensure the desired F0 is produced.

Hearing one's own voice is important for regulating ongoing speech and for mapping speech sounds onto articulator movements. However, it is currently unknown whether attention mediates changes in the relationship between motor commands and their acoustic output, which are necessary as growth and aging inevitably cause changes to the vocal tract. In this study, participants produced vocalizations while they heard their vocal pitch persistently shifted downward one semitone in both single- and dual-task conditions. During the single-task condition, participants vocalized while passively viewing a visual stream. During the dual-task condition, participants vocalized while also monitoring a visual stream for target letters, forcing participants to divide their attention. Participants' vocal pitch was measured across each vocalization, to index the extent to which their ongoing vocalization was modified as a result of the deviant auditory feedback. Smaller compensatory responses were recorded during the dual-task condition, suggesting that divided attention interfered with the use of auditory feedback for the regulation of ongoing vocalizations. Participants' vocal pitch was also measured at the beginning of each vocalization, before auditory feedback was available, to assess the extent to which the deviant auditory feedback was used to modify subsequent speech motor commands. Smaller changes in vocal pitch at vocalization onset were recorded during the dual-task condition, suggesting that divided attention diminished sensorimotor learning. Together, the results of this study suggest that attention is required for the speech motor control system to make optimal use of auditory feedback for the regulation and planning of speech motor commands.

Studies of interference in working and short-term memory suggest that irrelevant information may overwrite the contents of memory or intrude into memory. W

Recent research has argued that removal of relevant sensory information during the planning and control of simple, self-paced walking can result in increased demand on central processing resources in Parkinson’s disease (PD). However, little is known about more complex gait tasks that require planning of gait adaptations to cross over an obstacle in PD. In order to understand the interaction between availability of visual information relevant for self-motion and cognitive load, the current study evaluated PD participants and healthy controls while walking toward and stepping over an obstacle in three visual feedback conditions: (i) no visual restrictions; (ii) vision of the obstacle and their lower limbs while in complete darkness; (iii) vision of the obstacle only while in complete darkness; as well as two conditions including a cognitive load (with a dual task versus without a dual task). Each walk trial was divided into an early and late phase to examine changes associated with planning of step adjustments when approaching the obstacle. Interactions between visual feedback and dual task conditions during the obstacle approach were not significant. Patients with PD had greater deceleration and step time variability in the late phase of the obstacle approach phase while walking in both dark conditions compared to control participants. Additionally, participants with PD had a greater number of obstacle contacts when vision of their lower limbs was not available specifically during the dual task condition. Dual task performance was worse in PD compared to healthy control participants, but notably only while walking in the dark regardless of visual feedback. These results suggest that reducing visual feedback while approaching an obstacle shifts processing to somatosensory feedback to guide movement which imposes a greater demand on planning resources. These results are key to fully understanding why trips and falls occur in those with PD.

Auditory feedback is required to maintain fluent speech. At present, it is unclear how attention modulates auditory feedback processing during ongoing speech. In this event-related potential (ERP) study, participants vocalized/a/, while they heard their vocal pitch suddenly shifted downward a ½ semitone in both single and dual-task conditions. During the single-task condition participants passively viewed a visual stream for cues to start and stop vocalizing. In the dual-task condition, participants vocalized while they identified target stimuli in a visual stream of letters. The presentation rate of the visual stimuli was manipulated in the dual-task condition in order to produce a low, intermediate, and high attentional load. Visual target identification accuracy was lowest in the high attentional load condition, indicating that attentional load was successfully manipulated. Results further showed that participants who were exposed to the single-task condition, prior to the dual-task condition, produced larger vocal compensations during the single-task condition. Thus, when participants’ attention was divided, less attention was available for the monitoring of their auditory feedback, resulting in smaller compensatory vocal responses. However, P1-N1-P2 ERP responses were not affected by divided attention, suggesting that the effect of attentional load was not on the auditory processing of pitch altered feedback, but instead it interfered with the integration of auditory and motor information, or motor control itself.

Speech production requires the combined effort of a feedback control system driven by sensory feedback, and a feedforward control system driven by internal models. However, the factors that dictate the relative weighting of these feedback and feedforward control systems are unclear. In this event‐related potential (ERP) study, participants produced vocalisations while being exposed to blocks of frequency‐altered feedback (FAF) perturbations that were either predictable in magnitude (consistently either 50 or 100 cents) or unpredictable in magnitude (50‐ and 100‐cent perturbations varying randomly within each vocalisation). Vocal and P1–N1–P2 ERP responses revealed decreases in the magnitude and trial‐to‐trial variability of vocal responses, smaller N1 amplitudes, and shorter vocal, P1 and N1 response latencies following predictable FAF perturbation magnitudes. In addition, vocal response magnitudes correlated with N1 amplitudes, vocal response latencies, and P2 latencies. This pattern of results suggests that after repeated exposure to predictable FAF perturbations, the contribution of the feedforward control system increases. Examination of the presentation order of the FAF perturbations revealed smaller compensatory responses, smaller P1 and P2 amplitudes, and shorter N1 latencies when the block of predictable 100‐cent perturbations occurred prior to the block of predictable 50‐cent perturbations. These results suggest that exposure to large perturbations modulates responses to subsequent perturbations of equal or smaller size. Similarly, exposure to a 100‐cent perturbation prior to a 50‐cent perturbation within a vocalisation decreased the magnitude of vocal and N1 responses, but increased P1 and P2 latencies. Thus, exposure to a single perturbation can affect responses to subsequent perturbations.