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Stuttering Research - Device Research


March 2010

An experimental investigation of the effect of AAF on the conversational speech of adults who stutter.

Lincoln M, Packman A, Onslow M, Jones M.

Australian Stuttering Research Centre, The University of Sydney.


PURPOSE: This study investigates the impact on percent syllables stuttered (%SS) 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-minute conversational speech samples during a control condition and under four 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 four combined altered auditory feedback (AAF) conditions. No statistically significant differences in %SS 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 is likely to have 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.


December 2008 

Delayed auditory feedback effects during reading and conversation tasks: gender differences in fluent adults.

Corey DM, Cuddapah VA.

Tulane University, Department of Psychology, New Orleans, LA 07118, USA.

Delayed auditory feedback (DAF) impacts the speech fluency of normally fluent males more than that of normally fluent females. Understanding this gender difference may contribute to our understanding of gender differences in the prevalence of developmental stuttering. To characterize this gender difference in fluent people, DAF-induced dysfluency was measured in 20 male and 21 female young adults during oral reading and conversation tasks. Stutter-like dysfluencies (SLDs), articulation errors, interjections, reading errors, and speech rate were measured for both speech tasks as the participant spoke without feedback, with non-delayed feedback, and with DAF presented with 5 delay intervals (14 conditions total). DAF induced SLDs (but not other dysfluencies) more frequently during conversation than reading, and this effect was significantly greater for males than females (Gender x Task x Feedback interaction). Males also produced significantly more reading errors than females. DAF reduced speaking rate significantly more while reading than conversing (Task x Feedback interaction). DAF significantly decreased the frequency of interjections and increased the frequency of articulation errors; however, no Gender effects on these variables were observed. Although significant order effects indicated improved fluency across trials, covariance analysis suggested that order effects could not explain other results. EDUCATIONAL OBJECTIVES: After reading this article, the reader will be able to (1) Discuss developmental stuttering (DS) and gender differences in DS prevalence. (2) Define delayed auditory feedback (DAF). (3) Evaluate the evidence that gender is linked to DAF effects on fluent people. (4) Summarize the results of new research designed to assess sex differences in DAF effects on speech fluency in normally fluent adults. (5) Evaluate the degree to which evidence from the literature indicating that individual differences in attentional control may help us understand gender difference in DAF effects and possibly in DS prevalence as well.


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

Antipova EA, Purdy SC, Blakeley M, Williams S.

Discipline of Speech Science, Department of Psychology, Tamaki Campus, 261 Morrin Road, Glen Innes, The University of Auckland, Private Bag 92019, Auckland, New Zealand.

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.


Comparisons of stuttering frequency during and after speech initiation in unaltered feedback, altered auditory feedback and choral speech conditions.

Saltuklaroglu T, Kalinowski J, Robbins M, Crawcour S, Bowers A.

Audiology and Speech Pathology, University of Tennessee, Knoxville, TN, USA.

Background: Stuttering is prone to strike during speech initiation more so than at any other point in an utterance. The use of auditory feedback (AAF) has been found to produce robust decreases in the stuttering frequency by creating an electronic rendition of choral speech (i.e., speaking in unison). However, AAF requires users to self-initiate speech before it can go into effect and, therefore, it might not be as helpful as true choral speech during speech initiation. Aims: To examine how AAF and choral speech differentially enhance fluency during speech initiation and in subsequent portions of utterances. Methods & Procedures: Ten participants who stuttered read passages without altered feedback (NAF), under four AAF conditions and under a true choral speech condition. Each condition was blocked into ten 10 s trials separated by 5 s intervals so each trial required 'cold' speech initiation. In the first analysis, comparisons of stuttering frequencies were made across conditions. A second, finer grain analysis involved examining stuttering frequencies on the initial syllable, the subsequent four syllables produced and the five syllables produced immediately after the midpoint of each trial. Outcomes & Results: On average, AAF reduced stuttering by approximately 68% relative to the NAF condition. Stuttering frequencies on the initial syllables were considerably higher than on the other syllables analysed (0.45 and 0.34 for NAF and AAF conditions, respectively). After the first syllable was produced, stuttering frequencies dropped precipitously and remained stable. However, this drop in stuttering frequency was significantly greater (approximately 84%) in the AAF conditions than in the NAF condition (approximately 66%) with frequencies on the last nine syllables analysed averaging 0.15 and 0.05 for NAF and AAF conditions, respectively. In the true choral speech condition, stuttering was virtually (approximately 98%) eliminated across all utterances and all syllable positions. Conclusions & Implications: Altered auditory feedback effectively inhibits stuttering immediately after speech has been initiated. However, unlike a true choral signal, which is exogenously initiated and offers the most complete fluency enhancement, AAF requires speech to be initiated by the user and 'fed back' before it can directly inhibit stuttering. It is suggested that AAF can be a viable clinical option for those who stutter and should often be used in combination with therapeutic techniques, particularly those that aid speech initiation. The substantially higher rate of stuttering occurring on initiation supports a hypothesis that overt stuttering events help 'release' and 'inhibit' central stuttering blocks. This perspective is examined in the context of internal models and mirror neurons.


August 2008

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

Pollard R, Ellis JB, Finan D, Ramig PR.

University of Colorado at Boulder.

PURPOSE: Effects of the SpeechEasy when used under extra-clinical conditions over several months were investigated. Primary purposes were to help establish Phase I level information about the therapeutic utility of the SpeechEasy and compare those results to 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 two weeks in extra-clinical environments. Qualitative data was collected through weekly written logs and an exit questionnaire. RESULTS: Group analyses revealed a statistically significant effect of the SpeechEasy immediately post-fitting, but no treatment effect across four months' time. Individual responses varied greatly with regard to stuttering frequency and subjective impressions. Relatively more stuttering reduction occurred during oral reading than 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 to those previously reported in laboratory settings. Device use coincided more so with positive subjective impressions than measurable fluency improvement, highlighting challenges facing clinicians when implementing principles of evidence-based practice, including client-based preferences.


The effect of frequency altered feedback on stuttering duration and type.

Stuart A, Frazier CL, Kalinowski J, Vos PW.

Department of Communication Sciences and Disorders, East Carolina University, Greenville, NC 27858-4353, USA.

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.


January 2008

The effect of SpeechEasy on stuttering frequency, speech rate, and speech naturalness.

Armson J, Kiefte M.

School of Human Communication Disorders, Dalhousie University, 5599 Fenwick Street, Halifax, Nova Scotia B3H 1R2, Canada.

The effects of SpeechEasy on stuttering frequency, stuttering severity self-ratings, speech rate, and speech naturalness for 31 adults who stutter were examined. Speech measures were compared for samples obtained with and without the device in place in a dispensing setting. Mean stuttering frequencies were reduced by 79% and 61% for the device compared to the control conditions on reading and monologue tasks, respectively. Mean severity self-ratings decreased by 3.5 points for oral reading and 2.7 for monologue on a 9-point scale. Despite dramatic reductions in stuttering frequency, mean global speech rates in the device condition increased by only 8% in the reading task and 15% for the monologue task, and were well below normal. Further, complete elimination of stuttering was not associated with normalized speech rates. Nevertheless, mean ratings of speech naturalness improved markedly in the device compared to the control condition and, at 3.3 and 3.2 for reading and monologue, respectively, were only slightly outside the normal range. These results show that SpeechEasy produced improved speech outcomes in an assessment setting. However, findings raise the issue of a possible contribution of slowed speech rate to the stuttering reduction effect, especially given participants' instructions to speak chorally with the delayed signal as part of the active listening instructions of the device protocol. Study of device effects in situations of daily living over the long term is necessary to fully explore its treatment potential, especially with respect to long-term stability. Educational objectives: The reader will be able to discuss and evaluate: (1) issues pertinent to evaluating treatment benefits of fluency aids and (2) the effects of SpeechEasy on stuttering frequency, speech rate, and speech naturalness during testing in a dispensing setting for a relatively large sample of adults who stutter.


The effectiveness of SpeechEasy during situations of daily living.

O'Donnell JJ, Armson J, Kiefte M.

School of Human Communication Disorders, Dalhousie University, 5599 Fenwick Street, Halifax, Nova Scotia B3H 1R2, Canada.

A multiple single-subject design was used to examine the effects of SpeechEasy on stuttering frequency in the laboratory and in longitudinal samples of speech produced in situations of daily living (SDL). Seven adults who stutter participated, all of whom had exhibited at least 30% reduction in stuttering frequency while using SpeechEasy during previous laboratory assessments. For each participant, speech samples recorded in the laboratory and SDL during device use were compared to samples obtained in those settings without the device. In SDL, stuttering frequencies were recorded weekly for 9-16 weeks during face-to-face and phone conversations. Participants also provided data regarding device tolerance and perceived benefits. Laboratory assessments were conducted at the beginning and the end of the longitudinal data collection in SDL. All seven participants exhibited reduced stuttering in self-formulated speech in the Device compared to No-device condition during the first laboratory assessment. In the second laboratory assessment, four participants exhibited less stuttering and three exhibited more stuttering with the device than without. In SDL, five of seven participants exhibited some instances of reduced stuttering when wearing the device and three of these exhibited relatively stable amounts of stuttering reduction during long-term use. Five participants reported positive changes in speaking-related attitudes and perceptions of stuttering. Further investigation into the short- and long-term effectiveness of SpeechEasy in SDL is warranted. Educational objectives: The reader will be able to summarize: (1) issues pertinent to evaluating treatment benefits of wearable fluency aids and evaluate (2) the effect of SpeechEasy on stuttering frequency and the perceived benefits of device use in situations of daily living, as assessed weekly over the course of 9-16 weeks of wear, for seven adults who stutter.




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