Vikram N. Dayalu

Investigations of the impact of altered auditory feedback in‐the‐ear devices on the speech of people who stutter: initial fitting and 4‐month follow‐up

BACKGROUND Self-contained ear-level devices delivering altered auditory feedback (AAF) for the application with those who stutter have only been recently developed. AIMS The paper examines the first therapeutic application of self-contained ear-level devices in three experiments. The effect of the device on the proportion of stuttered syllables and speech naturalness was investigated following initial fitting and at 4 months post-fitting. METHODS & PROCEDURES Three experiments were undertaken: In Experiment 1, the effect of a self-contained in-the-ear device delivering AAF was investigated with those who stutter during reading and monologue. Two adolescents and five adults who stuttered read and produced monologue with and without a device fit monaurally. The device provided a frequency shift of +500 Hz in combination with a delayed auditory feedback of 60 ms. Custom-made ITC and CIC devices were fabricated for four adults and four youths in Experiment 2. The effect of group (i.e. youth versus adult), time (i.e. initial fitting versus 4-month follow-up), speech task (i.e. reading versus monologue), and device (i.e. present versus absent) on stuttering rate was examined. In Experiment 3, 15 naïve listeners rated the speech naturalness of speech produced by the participants in Experiment 2. Speech samples from six conditions were rated: reading and monologue without the device at the initial visit, reading and monologue with the device at the initial visit, and reading and monologue with the device at 4 months. OUTCOMES & RESULTS In Experiment 1, the proportion of stuttered syllables was significantly (p=0.011) reduced by approximately 90% during reading and 67% during monologue with the device relative to no device. Only a significant main effect of device (p=0.0028) was found in Experiment 2. That is, stuttering rate was significantly reduced with the device in place regardless of speech task or group and remained so 4 months later. In Experiment 3, speech samples generated while wearing the device were judged to be more natural sounding than those without the device (p<0.0001) for reading and monologue with both adults and youths. There was no significant difference between the mean naturalness ratings of speech samples generated during the initial fitting with the device relative to that at 4 months with the device (p>0.05) in all cases except with the youths while engaged in monologue. For that condition, raters judged the speech produced at the initial fitting as more natural. CONCLUSIONS These findings support the notion that a self-contained in-the-ear device delivering AAF assists those who stutter. With the device in place, stuttering is reduced and speech produced is judged to be more natural than with out the device.

Pseudofluency in Adults Who Stutter: The Illusory Outcome of Therapy

The majority of therapy programs for people who stutter are aimed at modifying the entire speech output by using techniques that reduce the overt signature events. Use of these techniques for extended time periods are thought to induce true fluency that is automatic, natural, and effortless. It is proposed that the present form of therapeutic intervention induces pseudofluency rather than true fluency. Pseudofluency is the speech posttherapy of persons who stutter, free of the discrete signature events of stuttering, but replaced by cognitively mediated gestures that are embedded as continuous prolongation or masked stuttering events throughout the speech act. This may account for the high rate of relapse and the problems associated with the maintenance, stability, and naturalness of speech after stuttering therapy.

Voluntary stuttering suppresses true stuttering: a window on the speech perception-production link.

In accord with a proposed innate link between speech perception and production (e.g., motor theory), this study provides compelling evidence for the inhibition of stuttering events in people who stutter prior to the initiation of the intended speech act, via both the perception and the production of speech gestures. Stuttering frequency during reading was reduced in 10 adults who stutter by approximately 40% in three of four experimental conditions: (1) following passive audiovisual presentation (i.e., viewing and hearing) of another person producing pseudostuttering (stutter-like syllabic repetitions) and following active shadowing of both (2) pseudostuttered and (3) fluent speech. Stuttering was not inhibited during reading following passive audiovisual presentation of fluent speech. Syllabic repetitions can inhibit stuttering both when produced and when perceived, and we suggest that these elementary stuttering forms may serve as compensatory speech gestures for releasing involuntary stuttering blocks by engaging mirror neuronal systems that are predisposed for fluent gestural imitation.

Stuttering inhibition via visual feedback at normal and fast speech rates

BACKGROUND Immediate and drastic reductions in stuttering are found when speech is produced in conjunction with a variety of second signals (for example, auditory choral speech and its permutations, and delayed auditory feedback). Initially, researchers suggested a decreased speech rate as a plausible explanation for the reduction in stuttering as people who stutter produced speech under second signals. However, this explanation was refuted by research findings that demonstrated reductions in stuttering at both normal and fast speech rates under second signals. Recent studies have also demonstrated significant reductions in stuttering from second signals delivered via the visual modality. However, the question as to whether stuttering can be substantially reduced at normal and fast speech rates under visual speech feedback conditions has yet to be answered. AIMS The current study investigated stuttering frequency reduction at normal and fast speech rates across different visual speech feedback conditions relative to a no-visual feedback condition. METHODS & PROCEDURES Ten adults who stutter recited memorized tokens of eight to 13 syllables under five visual speech feedback conditions at both normal and fast speech rates. Visual speech feedback conditions consisted of participants viewing the lower portion of their face (that is, lips, jaw, and base of the nose) on a monitor as they produced the aforementioned utterances. Conditions consisted of (1) no-visual feedback condition, (2) 0 ms (simultaneous visual speech feedback), (2) a 50-ms delay, (3) a 200-ms delay, and (4) a 400-ms delay. OUTCOMES & RESULTS A significant main effect of visual speech feedback on stuttering frequency was found (p= 0.001) with no significant main effect of speech rate or the interaction between speech rate and visual speech feedback. Relative to the no-visual feedback condition, the feedback conditions produced reductions in stuttering ranging from 27% (0 ms) to 62% (400 ms). Post-hoc comparisons revealed that all of the delay conditions differed significantly from the simultaneous feedback (p= 0.017) and the no-visual feedback conditions (p= 0.0002) while no significant differences between delay conditions (that is, 50, 200, and 400 ms) were observed. CONCLUSIONS & IMPLICATIONS The current findings demonstrate the capabilities of visual speech feedback signals to reduce stuttering frequency that is independent of the speakers rate of speech. Possible strategies are suggested to transfer these findings into naturalistic and clinical settings, though further research is warranted.

Say it with me: Stuttering inhibited

This study examined fluency enhancement in people who stutter via the concomitant presentation of silently mouthed visual speech. Ten adults who stutter recited memorized text while watching another speaker silently mouth linguistically equivalent and linguistically different material. Relative to a control condition, in which no concomitant stimulus was provided, stuttering was reduced by 71% in the linguistically equivalent condition versus only 35% in the linguistically different condition. Despite being an ‘incomplete’ second speech signal, visual speech possesses the capacity to immediately and substantially enhance fluency when it is linguistically equivalent to the intended utterance. It is suggested that fluency enhancement via concomitantly presented external speech is achieved through the extraction of relevant speech gestures from the external speech signal that compliment the intended production, thereby compensating for possible internal inconsistencies in the matching of speech codes in people who stutter. As visual speech perception relies on fewer redundant cues to demarcate the intended gestures, when used as an external stuttering inhibitor, higher degrees of linguistic equivalence seem to be necessary for optimal stuttering inhibition.

Producing the vowel/a/ prior to speaking inhibits stuttering in adults in the English language

This study investigated the effects of producing and listening to the vowel /a/ on the frequency of overt stuttering moments in eight people who stuttered. Stuttering frequency counts were made for the speech produced in the control condition, and after each of these four experimental conditions: (a) producing a vowel /a/ for 4 s; (b) producing a vowel /a/ for 4 s and waiting for 4 s; (c) listening to a recording of the vowel /a/ for 4 s; and (d) listening to a recording of the vowel /a/ for 4 s and waiting for 4 s. A significant reduction in the stuttering frequency was only observed following production of the vowel /a/ without a 4 s delay (P=0.02), suggesting that the vowel production prior to speech, serves as a temporary fluency enhancer. Its similarity to the occurrence of overt stuttering moments (e.g. discrete part-word repetitions and prolongations) and its relationship to the fundamental nature of the pathology are discussed.

Stuttering Frequency on Meaningful and Nonmeaningful Words in Adults Who Stutter

Previous research has suggested that word meaning can influence the loci and frequency of stuttering moments. Based on this proposition, it was hypothesized that people who stutter will exhibit a larger proportion of stuttering moments on meaningful words when compared to nonmeaningful or nonsense words. In order to test this hypothesis, stuttering frequency was examined among 9 English-speaking adults who stutter as they read a total of 126 words that were either meaningful or nonmeaningful in nature. The results indicated that approximately 117% more stuttering moments were recorded on nonmeaningful words when compared to meaningful words and this difference was statistically significant (p = 0.01). These findings challenge the notion that word meaning can be considered as a reliable predictor of stuttering frequency.

Autonomic and emotional responses of graduate student clinicians in speech–language pathology to stuttered speech

BACKGROUND Fluent speakers and people who stutter manifest alterations in autonomic and emotional responses as they view stuttered relative to fluent speech samples. These reactions are indicative of an aroused autonomic state and are hypothesized to be triggered by the abrupt breakdown in fluency exemplified in stuttered speech. Furthermore, these reactions are assumed to be the basis for the stereotypes held by different communicative partners towards people who stutter. AIMS To examine the autonomic and emotional reactions of graduate student clinicians in speech-language pathology as they viewed fluent and severe stuttered speech samples. METHODS & PROCEDURES Twenty-one female graduate student clinicians in speech-language pathology participated in this study. Each participant viewed four 30-s video samples (two fluent and two stuttered speech samples) while their autonomic responses (skin conductance response (SCR) and heart rate (HR)) were concurrently captured. Furthermore, emotional responses to stuttered and fluent speech samples were captured using the self-assessment manikin (SAM) and a rating scale with nine bipolar adjectives reflecting ones feelings. OUTCOMES & RESULTS An increase in SCR and deceleration in HR was observed as graduate clinicians viewed stuttered speech samples versus fluent speech samples and the differences were statistically significant. In addition, results from the self-rating scales showed that participants had negative feelings (e.g., emotionally aroused, unpleasant, embarrassed, uncomfortable, etc.) while viewing stuttered speech. CONCLUSIONS & IMPLICATIONS Findings suggest that graduate student clinicians in speech-language pathology demonstrated altered autonomic and emotional responses similar to those manifested by fluent and stuttered speakers as they viewed stuttered speech samples. Collectively, these findings support the contention that the inherent nature of stuttered speech triggers a visceral reaction in a listener, irrespective of their background and knowledge about the disorder.

The effect of static and dynamic visual gestures on stuttering inhibition.

The aim of the study was to evaluate the role of steady-state and dynamic visual gestures of vowels in stuttering inhibition. Eight adults who stuttered recited sentences from memory while watching video presentations of the following visual speech gestures: (a) a steady-state /u/, (b) dynamic production of /a-i-u/, (c) steady-state /u/ with an accompanying audible 1 kHz pure tone, and (d) dynamic production of /a-i-u/ with an accompanying audible 1 kHz pure tone. A 1 kHz pure tone and a no-external signal condition served as control conditions. Results revealed a significant main effect of auditory condition on stuttering frequency. Relative to the no-external signal condition, the combined visual plus pure tone conditions resulted in a statistically significant reduction in stuttering frequency. In addition, a significant difference in stuttering frequency was also observed when the visual plus pure tone conditions were compared to the visual only conditions. However, no significant differences were observed between the no-external signal condition and visual only conditions, or the no-external signal condition and pure tone condition. These findings are in contrast to previous findings demonstrated by similar vowel gestures presented via the auditory modality that resulted in high levels of stuttering inhibition. The differential role of sensory modalities in speech perception and production as well as their individual capacities to transfer gestural information for the purposes of stuttering inhibition is discussed.

Effect of continuous speech and non-speech signals on stuttering frequency in adults who stutter.

Abstract The inhibitory effects of continuously presented audio signals (/a/, /s/, 1,000 Hz pure-tone) on stuttering were examined. Eleven adults who stutter participated. Participants read four 300-syllable passages (i.e. in the presence and absence of the audio signals). All of the audio signals induced a significant reduction in stuttering frequency relative to the control condition (P = 0.005). A significantly greater reduction in stuttering occurred in the /a/ condition (P < 0.05), while there was no significant difference between the /s/ and 1,000 Hz pure-tone conditions (P > 0.05). These findings are consistent with the notion that the percept of a second signal as speech or non-speech can respectively augment or attenuate the potency for reducing stuttering frequency.