Experimental investigation of the effects of frequency-altered auditory feedback on the speech of adults who stutter

Event- and interval-based measurement of stuttering: a review

BACKGROUND

Event- and interval-based measurements are two different ways of computing frequency of stuttering. Interval-based methodology emerged as an alternative measure to overcome problems associated with reproducibility in the event-based methodology. No review has been made to study the effect of methodological factors in interval-based absolute reliability data or to compute the agreement between the two methodologies in terms of inter-judge, intra-judge and accuracy (i.e., correspondence between raters' scores and an established criterion).

AIMS

To provide a review related to reproducibility of event-based and time-interval measurement, and to verify the effect of methodological factors (training, experience, interval duration, sample presentation order and judgment conditions) on agreement of time-interval measurement; in addition, to determine if it is possible to quantify the agreement between the two methodologies

METHODS & PROCEDURES

The first two authors searched for articles on ERIC, MEDLINE, PubMed, B-on, CENTRAL and Dissertation Abstracts during January-February 2013 and retrieved 495 articles. Forty-eight articles were selected for review. Content tables were constructed with the main findings.

MAIN CONTRIBUTION

Articles related to event-based measurements revealed values of inter- and intra-judge greater than 0.70 and agreement percentages beyond 80%. The articles related to time-interval measures revealed that, in general, judges with more experience with stuttering presented significantly higher levels of intra- and inter-judge agreement. Inter- and intra-judge values were beyond the references for high reproducibility values for both methodologies. Accuracy (regarding the closeness of raters' judgements with an established criterion), intra- and inter-judge agreement were higher for trained groups when compared with non-trained groups. Sample presentation order and audio/video conditions did not result in differences in inter- or intra-judge results. A duration of 5 s for an interval appears to be an acceptable agreement. Explanation for high reproducibility values as well as parameter choice to report those data are discussed.

CONCLUSIONS & IMPLICATIONS

Both interval- and event-based methodologies used trained or experienced judges for inter- and intra-judge determination and data were beyond the references for good reproducibility values. Inter- and intra-judge values were reported in different metric scales among event- and interval-based methods studies, making it unfeasible to quantify the agreement between the two methods.

The SpeechEasy device in stuttering and nonstuttering adults: fluency effects while speaking and reading

The SpeechEasy is an electronic device designed to alleviate stuttering by manipulating auditory feedback via time delays and frequency shifts. Device settings (control, default, custom), ear-placement (left, right), speaking task, and cognitive variables were examined in people who stutter (PWS) (n=14) compared to controls (n=10). Among the PWS there was a significantly greater reduction in stuttering (compared to baseline) with custom device settings compared to the non-altered feedback (control) condition. Stuttering was reduced the most during reading, followed by narrative and conversation. For the conversation task, stuttering was reduced more when the device was worn in the left ear. Those individuals with a more severe stuttering rate at baseline had a greater benefit from the use of the device compared to individuals with less severe stuttering. Our results support the view that overt stuttering is associated with defective speech-language monitoring that can be influenced by manipulating auditory feedback.

Theory and therapy in stuttering: a complex relationship

There are many treatments currently available for stuttering, for both children and adults. These range from direct interventions intended to reduce the severity and/or frequency of the speech behaviors of stuttering, to those intended to alleviate the anxiety and other mental health issues that can accompany the disorder. However, as there are little supporting data for many of these treatments, there is little consensus about which to use. Another way to evaluate stuttering treatments is to explore the extent to which they address the cause of the disorder. However, the cause of stuttering is not yet known. In this theoretical paper, a 3-factor causal model is presented, to which the mechanisms thought to be driving different treatments are then aligned. The model is innovative, in that it attempts to explain moments of stuttering. It is argued that all causal factors must be operating at each moment of stuttering. The model is intended as a new way of looking at cause, and how treatments may address cause. It is hoped this will stimulate discussion and lead to further lines of inquiry.

EDUCATIONAL OBJECTIVES

The reader will be able to: (a) describe the P&A 3-factor causal model of moments of stuttering; (b) state how indirect direct stuttering treatments relate to cause, according to the P&A model; (c) describe how direct stuttering treatments relate to cause, according to the P&A model; (d) state the purpose of cognitive behavior therapy; and (e) describe at least one suggestion for further research arising from the P&A model.

Immediate effects of AAF devices on the characteristics of stuttering: a clinical analysis

The present study investigated the immediate effects of altered auditory feedback (AAF) and one Inactive Condition (AAF parameters set to 0) on clinical attributes of stuttering during scripted and spontaneous speech. Two commercially available, portable AAF devices were used to create the combined delayed auditory feedback (DAF) and frequency altered feedback (FAF) effects. Thirty adults, who stutter, aged 18-68 years (M=36.5; SD=15.2), participated in this investigation. Each subject produced four sets of 5-min of oral reading, three sets of 5-min monologs as well as 10-min dialogs. These speech samples were analyzed to detect changes in descriptive features of stuttering (frequency, duration, speech/articulatory rate, core behaviors) across the various speech samples and within two SSI-4 (Riley, 2009) based severity ratings. A statistically significant difference was found in the frequency of stuttered syllables (%SS) during both Active Device conditions (p=.000) for all speech samples. The most sizable reductions in %SS occurred within scripted speech. In the analysis of stuttering type, it was found that blocks were reduced significantly (Device A: p=.017; Device B: p=.049). To evaluate the impact on severe and mild stuttering, participants were grouped into two SSI-4 based categories; mild and moderate-severe. During the Inactive Condition those participants within the moderate-severe group (p=.024) showed a statistically significant reduction in overall disfluencies. This result indicates, that active AAF parameters alone may not be the sole cause of a fluency-enhancement when using a technical speech aid.

EDUCATIONAL OBJECTIVES

The reader will learn and be able to describe: (1) currently available scientific evidence on the use of altered auditory feedback (AAF) during scripted and spontaneous speech, (2) which characteristics of stuttering are impacted by an AAF device (frequency, duration, core behaviors, speech & articulatory rate, stuttering severity), (3) the effects of an Inactive Condition on people who stutter (PWS) falling into two severity groups, and (4) how the examined participants perceived the use of AAF devices.

Análise sistemática da efetividade do uso da alteração do feedback auditivo para a redução da gagueira

OBJETIVO: Realizar uma revisão sistemática de pesquisas relacionadas aos efeitos da alteração do feedback auditivo sobre a fluência da fala em pessoas com gagueira. ESTRATÉGIA DE PESQUISA: Foram seguidos os preceitos do Cochrane Handbook: formulação da pergunta inicial (tema a ser pesquisado), localização e seleção dos estudos (base de dados PubMed) e compatibilização entre os pesquisadores (visando minimizar possíveis perdas de citações). CRITÉRIOS DE SELEÇÃO: Foram excluídas: citações em línguas que não fossem o Inglês, citações que não permitiram o acesso ao texto completo, citações repetidas por sobreposição das palavras-chave utilizadas, pesquisas realizadas exclusivamente com indivíduos fluentes; estudos de caso; revisões de literatura; cartas ao editor e textos que não se relacionavam diretamente ao tema. Desta forma, foram analisados os textos que efetivamente se relacionavam às pesquisas de tratamento com delayed auditory feedback (DAF)e o frequency-altered feedback (FAF). ANÁLISE DOS DADOS: Os dados foram analisados quanto aos indicadores da pesquisa e quanto aos marcadores de qualidade dos estudos. RESULTADOS: Os resultados indicaram que o uso dos dispositivos de alteração do feedback auditivo na redução do número de eventos de gagueira ainda não tem suporte robusto em sua aplicabilidade. A variabilidade de método não permite uma resposta ou uma tendência de resposta que possa ser considerada consistente sobre a eficácia do dispositivo. CONCLUSÃO: Embora as limitações apontadas nos estudos impeçam generalizações sobre a eficácia do uso do dispositivo para a redução da gagueira, essas mesmas limitações são recursos importantes para o planejamento de pesquisas futuras.

An experimental investigation of the effect of altered auditory feedback on the conversational speech of adults who stutter

PURPOSE

To investigate the impact on percentage of syllables stuttered of various durations of delayed auditory feedback (DAF), levels of frequency-altered feedback (FAF), and masking auditory feedback (MAF) during conversational speech.

METHOD

Eleven adults who stuttered produced 10-min conversational speech samples during a control condition and under 4 different combinations of DAF, FAF, and MAF. Participants also read aloud in a control condition with DAF and FAF.

RESULTS

A statistically significant difference was found between the NAF conversation condition and the 4 combined altered auditory feedback (AAF) conditions. No statistically significant differences in percentage of syllables stuttered were found in conversation or reading between the control conditions and the FAF/DAF or MAF conditions. The analysis of individual participants' data showed highly individual responsiveness to different conditions.

CONCLUSIONS

Participants' varying responses to differing AAF settings likely accounted for the failure to find group differences between conditions. These results suggest that studies that use standard DAF and FAF settings for all participants are likely to underestimate any AAF effect. It is not yet possible to predict who will benefit from AAF devices in everyday situations and the extent of those benefits.

Computational neural modeling of speech motor control in childhood apraxia of speech (CAS)

PURPOSE

Childhood apraxia of speech (CAS) has been associated with a wide variety of diagnostic descriptions and has been shown to involve different symptoms during successive stages of development. In the present study, the authors attempted to associate the symptoms of CAS in a particular developmental stage with particular information-processing deficits by using computational modeling with the Directions Into Velocities of Articulators (DIVA) model. The hypothesis was that the speech production system in CAS suffers from poor feed-forward control and, consequently, an increased reliance on the feedback control subsystem.

METHOD

In a series of computer simulations, the authors systematically varied the ratio between feed-forward and feedback control during production attempts in the acquisition of feed-forward motor commands. The simulations were evaluated acoustically on 4 selected key symptoms of CAS.

RESULTS

Results showed that increasing the reliance on feedback control causes increased severity of these 4 symptoms of CAS: deviant coarticulation, speech sound distortion, searching articulation, and increased variability.

CONCLUSIONS

The findings support the idea that the key symptoms found in CAS could result from an increased reliance on feedback control due to poor feed-forward commands. Two possible root causes of degraded feed-forward control in CAS are discussed: reduced somatosensory information and increased levels of neural noise.

A survey of Australian adult users of altered auditory feedback devices for stuttering: Use patterns, perceived effectiveness and satisfaction

PURPOSE

Small portable devices that provide delayed auditory feedback (DAF) and/or frequency altered feedback (FAF) have been developed and marketed to clinicians and people who stutter as fluency enhancing aids for use in everyday speaking situations. The literature contains many laboratory-based reports about the impact of altered auditory feedback (AAF) on the speech of people who stutter but few reports about its use in everyday speaking situations. This paper investigates use patterns and perceptions of the effectiveness and satisfaction with AAF devices.

METHODS

The current study surveys 14 Australian AAF users.

RESULTS

The survey responses revealed varied opinions about AAF devices and their use and effectiveness in everyday speaking situations. Opinions were somewhat related to the type of device used.

CONCLUSIONS

The results of this study provide some important directions for future research. In particular there is need to investigate the effectiveness of AAF devices when used in conjunction with other traditional treatments.

Investigations of the impact of altered auditory feedback in-the-ear devices on the speech of people who stutter: One-year follow-up

PURPOSE

This study examined objective and subjective measures of the effect of a self-contained ear-level device delivering altered auditory feedback (AAF) for those who stutter 12 months following initial fitting with and without the device.

METHOD

Nine individuals with developmental stuttering participated. In Experiment 1, the proportion of stuttering was examined during reading and monologue. A self-report inventory inquiring about behaviour related to struggle, avoidance and expectancy associated with stuttering was examined in Experiment 2. In Experiment 3, naïve listeners rated the speech naturalness of speech produced by the participants during reading and monologue.

RESULTS

The proportions of stuttering events were significantly ( p < 0.05) reduced at initial fitting and remained so 12 months post follow-up. After using the device for 12 months, self-reported perception of struggle, avoidance and expectancy were significantly (p < 0.05) reduced relative to pre-fitting. Naïve listeners rated the speech samples produced by those who stutter while wearing the device significantly more natural sounding than those produced without the device for both reading and monologue (p < 0.0001).

CONCLUSIONS

These findings support the notion that a device delivering AAF is a viable therapeutic alternative in the treatment of stuttering.

Claims of a ‘new’ stuttering treatment using time-out from speaking are exaggerated: A brief review of the literature and commentary on Hewat et al. (2006)

In a recent article, Hewat et al. 1 claimed to have developed novel procedures for treating stuttering. The present article reviews relevant literature, and shows that the Hewat et al. claims of originality are exaggerated. It is concluded that the Hewat et al. study includes conceptual and methodological weaknesses that render their findings predominantly uninterpretable.

Effects of the SpeechEasy on objective and perceived aspects of stuttering: a 6-month, phase I clinical trial in naturalistic environments

PURPOSE

Effects of the SpeechEasy when used under extraclinical conditions over several months were investigated. Primary purposes were to help establish Phase I level information about the therapeutic utility of the SpeechEasy and to compare those results with previous findings obtained in laboratory and clinical settings.

METHOD

Eleven adults who stutter participated. A nonrandomized ABA group design was utilized. Speech samples were collected every 2 weeks in extraclinical environments. Qualitative data were collected through weekly written logs and an exit questionnaire.

RESULTS

Group analyses revealed a statistically significant effect of the SpeechEasy immediately postfitting but no treatment effect across 4 months' time. Individual responses varied greatly with regard to stuttering frequency and subjective impressions. Relatively more stuttering reduction occurred during oral reading than during formulated speech.

CONCLUSIONS

Based on this protocol, Phase II trials are not indicated. However, positive individual responses and self-reports suggest some clinical utility for the SpeechEasy. The use of more challenging sampling procedures strengthened external validity and captured more modest altered auditory feedback effects compared with those previously reported in laboratory settings. Device use coincided more so with positive subjective impressions than with measurable fluency improvement, highlighting challenges facing clinicians when implementing principles of evidence-based practice, including client-based preferences.

Effects of altered auditory feedback (AAF) on stuttering frequency during monologue speech production

The present study investigated the immediate effects of eight altered auditory feedback (AAF) parameters on stuttering frequency during monologue speech production on two occasions. One of the modern commercially available portable anti-stuttering devices, "The Pocket Speech Lab" (Casa Futura Technologies) was used in the study to produce the auditory feedback alterations. Six types of combined delayed auditory feedback (DAF) and frequency shifted auditory feedback (FAF) and two types of DAF alone were tested for eight participants aged 16-55 years, with stuttering severity ranging from mild to severe. The present study found that AAF is an effective means to reduce stuttering frequency during monologue speech production. All eight AAF experimental conditions reduced stuttering frequency, however, there was substantial variability in the stuttering reduction effect across experimental conditions and across participants. There was also instability in stuttering reduction across the two testing sessions. On average, a 75 ms time delay on its own and a combination of the 75 ms time delay and a half octave downward frequency shift were found to be more effective than other combinations of AAF parameters that were investigated.

EDUCATIONAL OBJECTIVES

After reading this paper, the reader should be able to (1) summarize the research investigating the effect of altered auditory feedback on stuttering frequency during monologue speech production; (2) describe the stuttering reduction effect of the eight parameters of AAF tested during monologue speech production; and (3) discuss the possible clinical implications of the use of AAF for stuttering treatment.

The effect of frequency altered feedback on stuttering duration and type

PURPOSE

The effect of frequency altered feedback (FAF) on stuttering type (i.e., prolongation, repetition, or silent block) and stuttering duration (i.e., average duration of stuttering event and total stuttering time) was examined.

METHOD

Retrospective analyses of previously collected data from 12 adult persons who stutter who participated in an ABA time-series design while reading orally was undertaken. It was hypothesized that stuttering duration would decrease and there would be a differential reduction in the type of stuttering during FAF, concurrent with previously confirmed reduction of stuttering episodes. A total of 2,971 stuttered syllables were analyzed.

RESULTS

The total stuttering duration (s/min) was significantly reduced by approximately 50% irrespective of stuttering type (p = .0014). Although significant differences in the average duration(s) of the 3 stuttering types (p = .0064) existed, FAF significantly reduced each type of stuttering by approximately 20% (p = .0055). There was no differential effect on the reduction of proportion of stuttering type during FAF (p = .36).

CONCLUSIONS

FAF positively affects the speech of persons who stutter by reducing the proportion of stuttered events with a concomitant decrease in duration of residual stuttering and total stuttering time during oral reading.

Dissecting choral speech: properties of the accompanist critical to stuttering reduction

The effects of choral speech and altered auditory feedback (AAF) on stuttering frequency were compared to identify those properties of choral speech that make it a more effective condition for stuttering reduction. Seventeen adults who stutter (AWS) participated in an experiment consisting of special choral speech conditions that were manipulated to selectively eliminate specific differences between choral speech and AAF. Consistent with previous findings, results showed that both choral speech and AAF reduced stuttering compared to solo reading. Although reductions under AAF were substantial, they were less dramatic than those for choral speech. Stuttering reduction for choral speech was highly robust even when the accompanist's voice temporally lagged that of the AWS, when there was no opportunity for dynamic interplay between the AWS and accompanist, and when the accompanist was replaced by the AWS's own voice, all of which approximate specific features of AAF. Choral speech was also highly effective in reducing stuttering across changes in speech rate and for both familiar and unfamiliar passages. We concluded that differences in properties between choral speech and AAF other than those that were manipulated in this experiment must account for differences in stuttering reduction.

LEARNING OUTCOMES

The reader will be able to (1) describe differences in stuttering reduction associated with altered auditory feedback compared to choral speech conditions and (2) describe differences between delivery of a second voice signal as an altered rendition of the speakers own voice (altered auditory feedback) and alterations in the voice of an accompanist (choral speech).

On the importance of scientific rhetoric in stuttering: a reply to Finn, Bothe, and Bramlett (2005)

PURPOSE

To refute the alleged practice of "pseudoscience" by P. Finn, A. K. Bothe, and R. E. Bramlett (2005) and to illustrate their experimental and systematic bias when evaluating the SpeechEasy, an altered auditory feedback device used in the management of stuttering.

METHOD

We challenged the experimental design that led to the seemingly predetermined outcome of pseudoscience rather than science: Limited preselected literature was submitted to a purposely sampled panel of judges (i.e., their own students). Each criterion deemed pseudoscientific was contested with published peer-reviewed data illustrating the importance of good rhetoric, testability, and logical outcomes from decades of scientific research.

CONCLUSIONS

Stuttering is an involuntary disorder that is highly resistant to therapy. Altered auditory feedback is a derivation of choral speech (nature's most powerful stuttering "inhibitor") that can be synergistically combined with other methods for optimal stuttering inhibition. This approach is logical considering that in stuttering no single treatment is universally helpful. Also, caution is suggested when attempting to differentiate science from pseudoscience in stuttering treatments using the criteria employed by Finn et al. For example, evaluating behavioral therapy outcomes implements a post hoc or untestable system. Speech outcome (i.e., stuttered or fluent speech) determines success or failure of technique use, placing responsibility for failure on those who stutter.

A new antistuttering device: treatment of stuttering using bone conduction stimulation with delayed temporal feedback

OBJECTIVES

Stuttering is a communication disorder affecting approximately 1% of the adult population, some with severe manifestations. Speech therapy improves stuttering, but many do not receive enough benefit to communicate fluently. Antistuttering devices have been available for several years, but available technology has been limited in long-term success and reliability. The current study evaluates the effects of a prototype device using a modification of a currently used bone conduction hearing device with delayed auditory feedback on adult patients with significant stuttering problems.

STUDY DESIGN

A prospective nonrandomized study evaluating effects of a prototype device on stuttering in adult subjects.

METHODS

Ten stutterers > or=18 years of age were fit with a bone conduction device on a headband with temporal feedback delayed according to patient preference between 5 and 130 msec. Patients were asked to wear the device at least 4 hours per day for 4 weeks. Stuttering Severity Index-3 (SSI-3) tests were completed at prefit, immediate postfit, and at 2-week, 4-week, and 6-week intervals. Questionnaires were also completed at each visit.

RESULTS

: Nine patients completed the entire study. A statistically significant decline in SSI-3 scores was documented from prefit compared with immediate postfit and 4 weeks follow up (P < .001) using the Tukey test method. Statistical significance was approached but not reached at 2 weeks. There was no significant difference between prefit and the 6-week follow up when patients had returned the device. Patients subjectively noted improvement in their speech and confidence using the device.

CONCLUSIONS

A new antistuttering prototype using a modification of a bone conduction device with delayed temporal feedback is effective in decreasing stuttering in patients over a short time course. Further studies need to be completed to evaluate the long-term effects of the device.

The effect of SpeechEasy on stuttering frequency in laboratory conditions

The effect of SpeechEasy on stuttering frequency during speech produced in a laboratory setting was examined. Thirteen adults who stutter participated. Stuttering frequencies in two baseline conditions were compared to stuttering frequencies with the device fitted according to the manufacturer's protocol. The fitting protocol includes instructions for deliberate use of vowel prolongation. Relative to the initial baseline condition, stuttering was reduced by 74%, 36%, and 49% for reading, monologue, and conversation, respectively. In comparison, stuttering was reduced by 42%, 30%, and 36%, respectively with the device in place, but before participants were instructed to deliberately prolong vowels. Examination of individual response profiles revealed that although stuttering reduced in the device compared to the baseline conditions during at least one of three speech tasks for most participants, degree and pattern of benefit varied greatly across participants.

EDUCATIONAL OBJECTIVES

The reader will be able to: (1) discuss recent research in altered auditory feedback that led to the development of SpeechEasy, (2) analyze and describe issues related to evaluating the treatment benefits of fluency aids, and (3) summarize the range of outcomes that were observed with SpeechEasy in this study.

Altered auditory feedback and the treatment of stuttering: a review

Several authors have suggested that devices delivering altered auditory feedback (AAF) may be a viable treatment for adults and children who stutter. This paper reviews published, peer reviewed journal papers from the past 10 years that investigate the effect of AAF during different speaking conditions, tasks and situations. A review of that literature indicates that considerable experimental evidence and limited Phase 1 treatment outcome evidence has been accumulated about the effect of AAF on the speech of people who stutter. However, critical knowledge about the effect of AAF during conversational speech and in everyday speaking situations is missing. Knowledge about how to determine the correct levels of AAF for individuals, and the characteristics of those likely to benefit from AAF, also needs to be established. At present there is no reason to accept a recent suggestion that AAF devices would be a defensible clinical option for children. In general device development and availability has occurred at a faster pace than clinical trials research.

EDUCATIONAL OBJECTIVES

After reading this paper readers should be able to: (1) describe what altered auditory feedback is and common ways the speech signal is altered in stuttering; (2) describe the effects of AAF on the speech of adults who stutter; (3) provide a critical analysis of the literature in the area of AAF and stuttering.

Science and pseudoscience in communication disorders: criteria and applications

PURPOSE

The purpose of this tutorial is to describe 10 criteria that may help clinicians distinguish between scientific and pseudoscientific treatment claims. The criteria are illustrated, first for considering whether to use a newly developed treatment and second for attempting to understand arguments about controversial treatments.

METHOD

Pseudoscience refers to claims that appear to be based on the scientific method but are not. Ten criteria for distinguishing between scientific and pseudoscientific treatment claims are described. These criteria are illustrated by using them to assess a current treatment for stuttering, the SpeechEasy device. The authors read the available literature about the device and developed a consensus set of decisions about the 10 criteria. To minimize any bias, a second set of independent judges evaluated a sample of the same literature. The criteria are also illustrated by using them to assess controversies surrounding 2 treatment approaches: Fast ForWord and facilitated communication.

CONCLUSIONS

Clinicians are increasingly being held responsible for the evidence base that supports their practice. The power of these 10 criteria lies in their ability to help clinicians focus their attention on the credibility of that base and to guide their decisions for recommending or using a treatment.

The Perception of Speech Naturalness of Post-Therapeutic and Altered Auditory Feedback Speech of Adults with Mild and Severe Stuttering

The effect of therapy and altered auditory feedback (AAF) on the perception of speech naturalness of people who stutter was examined. Thirty-five naive young adult listeners rated speech samples from fluent speakers and individuals who stutter. Samples came from normal adults who spoke Standard American English; adults with mild or severe stuttering who spoke under conditions of non-altered feedback (NAF), delayed auditory feedback (DAF), and frequency-altered feedback (FAF); and adults with mild or severe stuttering prior to and following successful completion of a Precision Fluency Shaping Program. Speech produced under AAF was rated as significantly more natural sounding than speech from the same individuals under NAF (p < 0.0001). Speech produced during FAF was judged to be more natural sounding than that produced during DAF for those with mild (p = 0.003) and severe (p < 0.0001) stuttering. Mild stuttered speech was judged to have more natural-sounding speech than severe stuttered speech during AAF (p < 0.0001). Speech from individuals following therapy was rated significantly less natural sounding than that from individuals during AAF for both mild and severe stuttering (p < 0.0001). The speech of individuals prior to therapy was rated significantly more natural than their speech produced after therapy (p < 0.0001). Speech from normal fluent speakers was rated as significantly more natural sounding than all samples produced from the individuals who stutter (p < 0.0001). These findings support the contention that AAF benefits those who stutter through a reduction of stuttering with a gain in perceived speech naturalness.

Gestural recovery and the role of forward and reversed syllabic repetitions as stuttering inhibitors in adults

Instead of being the core stuttering 'problem', syllabic repetitions may be a biological mechanism, or 'solution', to the central involuntary stuttering block. Simply put, stuttering is an endogenous transitory state of 'shadowed speech', a choral speech derivative that allows for a neural release of the central block. To investigate this possibility, 14 adults who stutter read while listening to forward fluent speech, reversed fluent speech, forward stuttered speech, and reversed stuttered speech. All conditions induced significant degrees of stuttering inhibition when compared to a control condition. However, the reversed fluent condition was less powerful than the other three conditions ( approximately 42% vs. approximately 65%) for inhibiting stuttering. Stuttering inhibition appears to proceed by 'gestural recovery', made possible by the presence of an exogenous or 'second' set of speech gestures and engagement of mirror neurons. When reversed fluent speech was used, violations in normal gesture-time relationships (i.e., normal speech entropy) resulted in gestural configurations that apparently were inadequately recovered, and therefore, were not as conducive to high levels of stuttering inhibition. In contrast, high levels of encoding found in the simple syllabic structures of stuttered speech allowed its forward and reversed forms to be equally effective for gestural recovery and stuttering inhibition. The reversal of repeated syllables did not appear to significantly degrade the natural gesture-time relationships (i.e., they were perceptually recognizable). Thus, exogenous speech gestures that displayed near normal gestural relationships allowed for easy recovery and fluent productions via mirror systems, suggesting a more choral-like nature. The importance of syllabic repetitions is highlighted: both their perceived (exogenous) and produced (endogenous) forms appear to be fundamental, surface acoustic manifestations for central stuttering inhibition via the engagement of mirror neurons.

Acquired stuttering following right frontal and bilateral pontine lesion: A case study

We report neurological information and experimental data regarding acquired neurogenic stuttering in a 57-year-old male following ischemic lesion to the orbital surface of the right frontal lobe and the pons. The experimental data consist of stuttering frequency measures under various conditions that are well known to enhance fluency in most individuals with developmental stuttering. Specifically, we report data for adaptation, unison reading, delayed auditory feedback (DAF), and frequency altered feedback (FAF). This work is the first published report of such a comprehensive examination of a variety of fluency-enhancing conditions in acquired stuttering. The patient read six 200-word texts under different conditions: Six solo readings (Text 1), five unison readings followed by five solo readings (Text 2), five readings with non-altered auditory feedback (Text 3), five readings with 50 ms delayed auditory feedback (Text 4), five readings with increased FAF (Text 5), and five readings with decreased FAF (Text 6). Results indicate that, unlike the typical situation for developmental stuttering, this individual with acquired neurogenic stuttering did not show increased fluency during an adaptation paradigm or under unison, DAF, and FAF conditions. We discuss possible implications of these findings and emphasize the need for further research on acquired neurogenic stuttering.

The modification of speech naturalness during rhythmic stimulation treatment of stuttering

This study investigated the modification of speech naturalness during stuttering treatment. It systematically replicated an earlier study (Ingham & Onslow, 1985) that demonstrated that unnatural-sounding stutter-free speech could be shaped into more natural-sounding stutter-free speech by using regular feedback of speech-naturalness ratings during speaking tasks. In the present study, the some procedure was used with three persons who stutter-2 adolescent girls and 1 adult man-during rhythmic stimulation conditions. The two adolescent participants spoke only English, but Spanish was the first and English the second language (ESL) of the adult participant. For the 2 adolescents, it was demonstrated that their unnatural-sounding rhythmic speech could be shaped to levels found among normally fluent speakers without losing the fluency-inducing benefits of rhythmic speech. The findings indicate that speech-naturalness feedback may be a powerful procedure for overcoming a problematic aspect of rhythmic speech treatments of stuttering. However, it was not possible to deliver reliable speech-naturalness feedback to the adult ESL speaker, who also displayed a strong dialect. The study highlights the need to find strategies to improve interjudge agreement when using speech naturalness ratings with speakers who display a strong dialect.

Assessing Efficacy of Stuttering Treatments

Efficacy has been defined as the extent to which a specific intervention, procedure, regimen or service produces a beneficial result under ideally controlled conditions when administered or monitored by experts. Studies on efficacy can be divided into those that study methods of conducting treatment (treatment process research) and those that are concerned with the effects of treatments (treatment outcome research). This reviews both of these areas, emphasizes the former and considers such key determinants of efficacy as measurement, treatment integrity and design issues. A set of criteria is given and a meta-analysis of whether studies published since 1993 meet these criteria is reported (incorporating some pragmatic and ethical considerations). The review ends by considering future directions that warrant further investigation.

Effects of monitoring condition and frequency-altered feedback on stuttering frequency

The purpose of the study was to examine stuttering frequency during speaking conditions that are believed to mitigate stuttering frequency both with normal nonaltered auditory feedback (NAF) and a known fluency-enhancing feedback. Specifically, stuttering frequency was examined as a function of three monitoring conditions under NAF and frequency-altered feedback (FAF): no monitoring (i.e., speaking alone, in the absence of audio and visual recording), audiovisual monitoring (i.e., speaking alone with audiovisual recording), and audiovisual monitoring with observers (i.e., speaking with audiovisual recording in the presence of two observers). Seven adults and one adolescent who stutter served as participants. Stuttering frequency was differentially affected across monitoring conditions under each auditory feedback condition (p = .027). Post hoc analyses revealed no significant difference in stuttering frequency between the two conditions in the absence of the observers (i.e., no monitoring vs. audiovisual monitoring) under NAF (p = .45). There was, however, a significant difference in stuttering frequency for the no-monitoring and audiovisual-monitoring conditions relative to the audiovisual-monitoring-with-observers condition (p = .0002). There was no statistically significant difference in stuttering frequency across monitoring conditions under FAF (p > .05). The findings are consistent with the notion that during NAF stuttering frequency varies as a function of hierarchical socio-environmental conditions in which inanimate monitoring conditions constitute one entity. Such a relationship does not exist during FAF.

Differential effects of frequency shifted feedback between child and adult stutterers

It has been reported previously that presentation of an altered form of the voice enhances the fluency of people who stutter. One of these forms of alteration is frequency shifted feedback. The effects of frequency shifted feedback was compared between two speaker groups that differed in age. The fluency enhancing effects of frequency shifted feedback was greater for adult speakers (mean age 21;3) than for children (mean age 9;11). The results are discussed in terms of their implications for theory and treatment.

Methods of interval selection, presence of noise and their effects on detectability of repetitions and prolongations

Accurate methods for locating specific types of stuttering events are necessary for diagnosis, treatment, and prognosis. A factor that could add variability to assessment of stuttering is noise on recordings. The effects of noise were assessed by adding noise to intervals of speech containing all fluent material, fluent material with a repetition, or fluent material with a prolongation. These intervals allow a unique dysfluency response to be made. A statistical analysis of the occurrence of such intervals in spontaneous speech showed that only a limited number of intervals met these criteria. This demonstrated that selecting intervals at random from spontaneous speech (as in time interval analysis procedure) will infrequently lead to a unique and unambiguous dysfluency specification for the interval. Intervals were selected for testing from the intervals that met the stipulated criteria. These were presented for dysfluency judgment when the position of the stuttering within an interval was varied and with different amounts of added noise (no added noise, 3 dB, and 6 dB of noise relative to mean speech amplitude). Accuracy in detecting stuttering type depended on noise level and the stuttering's position in the interval, both of which also depended on the type of stuttering: Noise level affected detection of repetitions more than prolongations: Repetitions were more difficult to detect when they occurred at the end of an interval whereas prolongations were more difficult to detect when they were at the beginning of an interval. The findings underline the importance of adopting rigorous recording standards when speech is to be employed to make stuttering assessments.

Effect of extended exposure to frequency-altered feedback on stuttering during reading and monologue

An ABA time series design was used to examine the effect of extended, continuous exposure to frequency-altered auditory feedback (FAF) during an oral reading and monologue task on stuttering frequency and speech rate. Twelve adults who stutter participated. A statistically significant decrease in number of stuttering events, an increase in number of syllables produced, and a decrease in percent stuttering was observed during the experimental segment relative to baseline segments for the oral reading task. In the monologue task, there were no statistically significant differences for the number of stuttering events, number of syllables produced, or percent stuttering between the experimental and baseline segments. Varying individual patterns of response to FAF were evident during the experimental segment of the reading task: a large consistent reduction in stuttering, an initial reduction followed by fluctuations in amount of stuttering, and essentially no change in stuttering frequency. Ten of 12 participants showed no reduction in stuttering frequency during the experimental segment of the monologue task. These findings have ramifications both for the clinical utilization of FAF and for theoretical explanations of fluency-enhancement.

Effect of monaural and binaural altered auditory feedback on stuttering frequency

The effect of monaural and binaural alterations in auditory feedback on stuttering frequency was investigated. Eleven participants who stutter read aloud under nonaltered auditory feedback (NAF) and monaural and binaural conditions of frequency altered feedback [(FAF), on-quarter octave shift upward] and delayed auditory feedback [(DAF), 50-ms delay] at a normal speech rate. Relative to the NAF condition, reductions in stuttering frequency of approximately 60%-75% were found with the altered auditory feedback conditions. Post hoc single-df comparisons revealed a reduction in stuttering frequency with altered auditory feedback versus NAF (p < 0.0001), a greater reduction in stuttering frequency for binaural compared to monaural altered auditory feedback (p = 0.028), and nonsignificant differences in stuttering frequencies for right versus left monaural conditions (p = 0.54) and DAF versus FAF (p = 0.70).