Evolution of a target-based behavioral therapy for stuttering☆

Speech rate convergence has been reported previously as a phenomenon in which one's speech rate is influenced by his/her partner's speech rate. This phenomenon has been demonstrated in artificial settings, and to some extent, in mother-child interactions. The purpose of this study was to explore speech rate adjustment in a quasi-natural adult-adult conversation.

An A-B-A-B paradigm was used, in which ten adults conversed on a given topic with two experimenters. Speech rates of both communication partners were measured.

Participants significantly reduced their speech rate, in response to the experimenters’ reduction in speech rate. However, the participants' reduction in speech rate was significantly smaller than the experimenters’ reduction in speech rate. In addition, during the controlled slow speech rate, the participants’ speech rate correlated negatively with that of the experimenters’.

Results suggest that speech rate convergence is a non-linear phenomenon, and may be affected by various linguistic as well as communicational factors. From a clinical perspective, the results support the use of the modeling strategy in speech therapy, as a means to facilitate a reduction in clients' speech rate.

General vulnerability to stuttering is the broad awareness of stuttering and the ever-present, experiential sense of a person who stutters (PWS). It is defined by stuttering in all its forms and the awareness of its presence, both in moments of stuttering and moments of perceivably fluent speech. Under the heading of general vulnerability to stuttering is specific vulnerability to stuttering, which includes the actual events of stuttering (i.e., overt symptoms, covert symptoms, subperceptual stuttering, and anticipation of stuttering). The differentiation between the two is that specific vulnerability requires a specific moment of stuttering where general vulnerability does not.

Extreme prolongations, which can be generated via extreme delayed auditory feedback (DAF) (e.g., 250–500 ms) or mediated cognitively with timing applications (e.g., analog stopwatch) at 2 s per syllable, have long been behavioral techniques used to inhibit stuttering. Some therapies have used this rate solely to establish initial fluency, while others use extremely slowed speech to establish fluency and add other strategic techniques such as easy onsets and diaphragmatic breathing. Extreme prolongations generate effective, efficient, and immediate forward flowing fluent speech, removing the signature behaviors of discrete stuttering (i.e., syllable repetitions and audible and inaudible postural fixations). Prolonged use of extreme prolongations establishes carry-over fluency, which is spontaneous, effortless speech absent of most, if not all, overt and covert manifestations of stuttering. The creation of this immediate fluency and the immense potential of extreme prolongations to generate long periods of carry-over fluency have been overlooked by researchers and clinicians alike.

Clinicians depart from these longer prolongation durations as they attempt to achieve the same fluent results at a near normal rate of speech. Clinicians assume they are re-teaching fluency and slow rates will give rise to more normal rates with less control, but without carry-over fluency, controls and cognitive mediation are always needed for the inherently unstable speech systems of persons who stutter to experience fluent speech. The assumption being that the speech system is untenable without some level of cognitive and motoric monitoring that is always necessary. The goal is omnipresent “near normal rate sounding fluency” with continuous mediation via cognitive and motoric processes. This pursuit of “normal sounding fluency” continues despite ever-present relapse. Relapse has become so common that acceptance of stuttering is the new therapy modality because relapse has come to be understood as somewhat inevitable. Researchers and clinicians fail to recognize that immediate amelioration of stuttering and its attendant carry-over fluency are signs of a different pathway to fluency. In this path, clinicians focus on extreme prolongations and the extent of their carry-over. While fluency is automatically generated under these extreme prolongations, the realization is that communication at this rate in routine speaking tasks is not feasible. The perceived solution is a systematic reduction in the duration of these prolongations, which attempts to approximate “normal speech.” Typically, the reintroduction of speech at a normalized rate precipitates a laborious style that is undesirable to the person who stutters (PWS) and is discontinued, once departed from the comforts of the clinical setting. The inevitable typically occurs; the well-intentioned therapist instructs the PWS to focus on the techniques while speaking at a rate that is nearest normal speech, but the overlooked extreme prolongations are unlikely to ever be revisited.

The foundation of this hypothesis is that the departure from fluency generators (e.g. extreme prolongations) is the cause of regression to the stuttering set point. In turn, we postulate that the continued use of extreme prolongations, as a solitary practice method, will establish and nurture different neural pathways that will create a modality of fluent speech, able to be experienced without cognitive or motoric mediation. This would therefore result in fewer occurrences of stuttering due to a phenomenon called carry-over fluency. Thus, we hypothesize that the use of extreme prolongations fosters neural pathways for fluent speech, which will result in carry-over fluency that does not require mediation by the speaker.

Stuttering is a common, highly heritable neurodevelopmental disorder characterized by deficits in the volitional control of speech. Whole-exome sequencing identified two heterozygous AP4E1 coding variants, c.1549G>A (p.Val517Ile) and c.2401G>A (p.Glu801Lys), that co-segregate with persistent developmental stuttering in a large Cameroonian family, and we observed the same two variants in unrelated Cameroonians with persistent stuttering. We found 23 other rare variants, including predicted loss-of-function variants, in AP4E1 in unrelated stuttering individuals in Cameroon, Pakistan, and North America. The rate of rare variants in AP4E1 was significantly higher in unrelated Pakistani and Cameroonian stuttering individuals than in population-matched control individuals, and coding variants in this gene are exceptionally rare in the general sub-Saharan West African, South Asian, and North American populations. Clinical examination of the Cameroonian family members failed to identify any symptoms previously reported in rare individuals carrying homozygous loss-of-function mutations in this gene. AP4E1 encodes the ε subunit of the heterotetrameric (ε-β4-μ4-σ4) AP-4 complex, involved in protein sorting at the trans-Golgi network. We found that the μ4 subunit of AP-4 interacts with NAGPA, an enzyme involved in the synthesis of the mannose 6-phosphate signal that targets acid hydrolases to the lysosome and the product of a gene previously associated with stuttering. These findings implicate deficits in intracellular trafficking in persistent stuttering.

Stuttering can affect many aspects of a person's life. People who stutter report that they experience negative reactions to stuttering, difficulty communicating in key situations, diminished satisfaction with life, and a reduced ability to achieve their goals in life. Unfortunately, most treatment outcomes studies have focused on changes in the observable characteristics of stuttering, with significantly fewer studies examining the broader consequences of stuttering. This paper proposes that evaluation of stuttering treatment outcomes can be enhanced through assessment of impact of stuttering on a speaker's quality of life. A means of assessing quality of life is described, based on the Overall Assessment of the Speaker's Experience of Stuttering (OASES; Yaruss and Quesal, 2006, Yaruss and Quesal, 2008). The OASES is a multi-dimensional assessment instrument built upon the World Health Organization's International Classification of Functioning, Disability, and Health (ICF; WHO, 2001; see also Yaruss & Quesal, 2004). One section of the OASES is designed to assess specific aspects of quality of life in individuals who stutter. Preliminary data from two ongoing studies involving the OASES are briefly summarized in order to demonstrate: (a) that individuals who stutter do report an adverse impact on their quality of life as a result of stuttering and (b) that quality of life can improve following treatment for stuttering. It is recommended that future stuttering treatment outcomes studies directly examine the broader consequence of stuttering by focusing, in part, on quality of life.
Educational objectives: After reading this article, the participant will be able to: (1) describe some of the adverse consequences of stuttering reported by individuals who stutter; (2) define quality of life as it relates to the study of the stuttering disorder; (3) explain the value of assessing quality of life in stuttering treatment outcomes research.

Data on disfluencies in the speech of non-stuttering adults are relevant to several aspects of the assessment and treatment of adults who stutter. Currently, very few sources provide relevant data. In the existing literature on normally fluent speakers, there is no consistency in sample length or topic or in which types of disfluency are counted. Many studies report incomplete data, making it difficult to compare new results to previous ones. The purpose of this study was to assess the effect of sample length and topic on fluency levels in the speech of non-stuttering adult men. Monologues produced by 25 English-speaking men with no reported communication disorder were analyzed for the presence of disfluencies. The group means for total disfluencies were between 6 and 8 per 100 syllables for all samples. A within-subjects Length (3) by Topic (3) ANOVA found a significant interaction (Length by Topic), however, the clinical importance of this result is minimal. The mean number of within-word disfluencies (also called stuttering-like disfluencies or SLDs) was below 1.5 per 100 syllables for all samples, although there was some variation across individual speakers. The data presented will be useful to clinicians and to researchers interested in disfluencies in spontaneous speech.

Learning outcomes: Readers will be able to (1) identify several methodological problems in studies of disfluency including counting methods and descriptions of participants; (2) identify the range of within-word disfluencies (also called SLDs) and other disfluencies in this study and other similar ones; (3) know whether topic/type of speech or sample length is more likely to affect disfluency levels in non-stuttering adults.