Deficit or Difference? Effects of Altered Auditory Feedback on Speech Fluency and Kinematic Variability in Adults Who Stutter

Subtle Patterns of Altered Responsiveness to Delayed Auditory Feedback during Finger Tapping in People Who Stutter

Differences in sensorimotor integration mechanisms have been observed between people who stutter (PWS) and controls who do not. Delayed auditory feedback (DAF) introduces timing discrepancies between perception and action, disrupting sequence production in verbal and non-verbal domains. While DAF consistently enhances speech fluency in PWS, its impact on non-verbal sensorimotor synchronization abilities remains unexplored. A total of 11 PWS and 13 matched controls completed five tasks: (1) unpaced tapping; (2) synchronization-continuation task (SCT) without auditory feedback; (3) SCT with DAF, with instruction either to align the sound in time with the metronome; or (4) to ignore the sound and align their physical tap to the metronome. Additionally, we measured participants' sensitivity to detecting delayed feedback using a (5) delay discrimination task. Results showed that DAF significantly affected performance in controls as a function of delay duration, despite being irrelevant to the task. Conversely, PWS performance remained stable across delays. When auditory feedback was absent, no differences were found between PWS and controls. Moreover, PWS were less able to detect delays in speech and tapping tasks. These findings show subtle differences in non-verbal sensorimotor performance between PWS and controls, specifically when action-perception loops are disrupted by delays, contributing to models of sensorimotor integration in stuttering.

A Comprehensive Analysis of Speech Disfluencies in Autistic Young Adults and Control Young Adults: Group Differences in Typical, Stuttering-Like, and Atypical Disfluencies

PURPOSE

The purpose of this study was to examine the nature of speech disfluencies in autistic young adults and controls by using a wide-range disfluency classification of typical disfluencies (TD; i.e., filled pauses, revisions, abandoned utterances, and multisyllable word and phrase repetitions), stuttering-like disfluencies (SLD; i.e., sound and syllable repetitions, monosyllable word repetitions, prolongations, blocks, and broken words), and atypical disfluencies (AD; i.e., word-final prolongations and repetitions and atypical insertions).

METHOD

Thirty-two autistic young adults and 35 controls completed a narrative telling task based on socially complex events. Frequencies of total disfluencies, TD, SLD, AD and stuttering severity were compared between groups.

RESULTS

The overall frequency of disfluencies was significantly higher in the autistic group and significant between-group differences were found for all disfluency categories. The autistic group produced significantly more revisions, filled pauses, and abandoned utterances, and each subtype of SLD and AD than the control group. In total, approximately every fourth autistic participants scored at least a very mild severity of stuttering, and every fifth produced more than three SLD per 100 syllables.

CONCLUSIONS

Disfluent speech can be challenging for effective communication. This study revealed that the speech of autistic young adults was highly more disfluent than that of the controls. The findings provide information on speech disfluency characteristics in autistic young adults and highlight the importance of evaluating speech disfluency with a wide-range disfluency classification in autistic persons in order to understand their role in overall communication. The results of this study offer tools for SLPs to evaluate and understand the nature of disfluencies in autistic persons.

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

PURPOSE

Prior work has shown that Adults who stutter (AWS) have reduced and delayed responses to auditory feedback perturbations. This study aimed to determine whether external timing cues, which increase fluency, resolve auditory feedback processing disruptions.

METHODS

Fifteen AWS and sixteen adults who do not stutter (ANS) read aloud a multisyllabic sentence either with natural stress and timing or with each syllable paced at the rate of a metronome. On random trials, an auditory feedback formant perturbation was applied, and formant responses were compared between groups and pacing conditions.

RESULTS

During normally paced speech, ANS showed a significant compensatory response to the perturbation by the end of the perturbed vowel, while AWS did not. In the metronome-paced condition, which significantly reduced the disfluency rate, the opposite was true: AWS showed a significant response by the end of the vowel, while ANS did not.

CONCLUSION

These findings indicate a potential link between the reduction in stuttering found during metronome-paced speech and changes in auditory motor integration in AWS.

Speech kinematic variability in adults who stutter is influenced by treatment and speaking style

AIM

We tested whether completion of the Comprehensive Stuttering Program (CSP) is associated with a reduction in speech kinematic variability relative to pre-treatment when adults who stutter (AWS) use a casual speaking manner or fluency skills.

RATIONAL

Kinematic variability is higher in AWS suggesting a sensorimotor vulnerability; however, it is not clear whether high variability is a trait related to the underlying disorder or reflects the mutable state of stuttering. Speech restructuring intervention such as the CSP could support more consistent articulatory control and stable movement patterns.

METHODOLOGY

Thirteen AWS were tested before and after completing the CSP while 11 adults who do not stutter (AWNS) completed a single session. Participants were instructed to use a casual manner of speaking in the first post-treatment session. In the second post-treatment condition, the AWS employed their fluency skills at a control speaking rate. An optical tracking system captured lower lip movements while participants spoke two English phrases and a complex nonword. Across-utterance kinematic variability was measured using the spatiotemporal index (STI) and within-utterance variability was measured with recurrence quantification analysis (RQA).

RESULTS

There was a positive treatment outcome based on significant reductions in percentage syllables stuttered (%SS) during speaking and reading, decreases in stuttering severity and improved perceptions of stuttering and communication confidence. The STI of the AWS decreased significantly after treatment for both speaking styles. The RQA variables indicated that AWS used a less stereotyped and more flexible manner of speaking in the casual condition after treatment, but speech movement regularity increased when using fluency skills.

CONCLUSIONS

The AWS showed a significant decrease in labial kinematic variability alongside a successful treatment outcome involving speech restructuring and cognitive behavioral techniques. These changes in across-utterance and within-utterance kinematic indices demonstrate that effective stuttering treatment can promote speech motor stability along with fluent speech.

Contemporary Theories of Stuttering Development

The article presents a theoretical analysis of contemporary models of persistent stuttering development in children and adults at the current period of development of science. The accumulated amount of scientific knowledge suggests that stuttering has a neurological basis: it is associated with disorders in the structure and function of the brain. On this basis, there have been emerged models of stuttering that link the cause of a speech disorder with an unstable speech motor system. Theories and models of stuttering based on cognitive and language processing are likely to be useful in that they have explanatory power in relation to the mechanisms that play an important role in the production of key symptoms of stuttering. Considering that stuttering is a complex disorder, the logical result of this was the proposal of multifactorial models of impaired speech fluency. The presented overview may be useful to psychiatrists, clinical psychologists, speech therapists, teachers, and practitioners interacting with children and adults with stuttering and other speech fluency disorders.