همراه با افزایش سن این میزان به حدود یک درصد و در بزرگسالی این آمار به حدود 0.1 درصد می رسد.
میزان شیوع لکنت در جنس مذکر و مونث نیز متفاوت است. این نسبت در افراد مذکر نسبت به افراد مونث سه یا چهار به یک می باشد، یعنی پسران سه تا چهار برابر دختران به لکنت مبتلا می گردند.
دلایل استفاده از لکنت شکن دیجیتال توسط درمانگردر سایر کشورها
یک- داشتن دانش استفاده از آن توسط درمانگر ، زیرا اطلاعات پایه ای از آکوستیک ، الکترونیک ، کامپیوتر ، روانشناسی به انضمام آسیب شناسی گفتار و زبان را می طلبد
دو- داشتن فرهنگ استفاده از آن توسط درمانجو، زیرا بکار بردن دستگاه در طول مدت شش ماه تا یکسال هر روز و هرروز بدور از تحت تاثیر قرار گرفتن توسط اطرافیان و دوستانی که توان مالی تهیه آنرا ندارند ، تا حصول نیجه نهایی الزامیست
لازم به ذکر است که قیمت لکنت شکن در حال حاضربین دوازده تا شانزده میلیون تومان است ، لذا به دلیل محدودیت مالی شرکت تهیه کننده ، این دستگاه به صورت استیجاری و امانت در طول مدت درمان ، پس از ارزیابی اولیه دراختیار فرد متقاضی قرار داده خواهد شد
سه- داشتن صرفه اقتصادی، نسبت به حضور در جلسات درمانی هفتگی
چهار – دنبال کردن پروتکل درمانی هفتگی توسط درمانجو، بنا به صلاحدید درمانگر در طول دوره درمان
پنجم – الزام به ارسال روزمره نتایج درمان توسط درمانجو به صورت فایل صوتی از طریق پیام رسانهای جمعی ، حتی پس از بهبود کامل به مدت یکسال به منظور جلوگیری از پدیده بازگشت لکنت زبان
the model speaker, rather than providing a nondistorted motor template for the person who stutters to match, instead provides a pacing or rhythmic one (Johnson & Rosen, 1937); a perspective that would appear consistent with Kalinowski et al’s findings. It is worth noting that all of those mentioned above have also been levelled at the fluency enhancing properties of delayed auditory feedback (DAF), which we discuss below. (The relationship between choral speech and DAF is an important one, and we return to this with regard to therapy in chapter 14.)
This is a type of cued speech which is very closely related to choral and unison versions. Technically, shadowed speech occurs where there is a slight delay between the speech of the model speaker and the person who stutters, as opposed to the simultaneous output produced during unison and choral speech. The difference is that while with choral speech the speaker knows exactly what the model speaker is going to say, shadowed speech can be used to follow the novel speech of the model speaker. Like choral/unison speech, shadowing can produce dramatic results (Cherry & Sayers, 1956; Kelham & McHale, 1966), but like them the gains in fluency tend to be lost once the stimulus of the model speaker has ended. Because of this, the use of choral or shadowed speech is now rare, and usually confined only to moments in therapy or assessment, where it is considered important to have the client experience a moment of fluency, albeit in the knowledge that this method of producing it will not provide any basis for sustainable improvement. What is interesting from our present perspective, however, is the potential relationship between shadowed speech and delayed auditory feedback. As we will see in chapter 16, the fluency enhancing effect of shadowed and choral speech has been put to use in devices which use DAF and frequency auditory feedback (FAF) to approximate the effects of speaking alongside other speakers.
Delayed auditory feedback
It is now over 40 years since Goldiamond and colleagues first stumbled on the potential fluency enhancing effects of delayed auditory feedback (Flanagan, Goldiamond, & Azrin, 1958, 1959; Goldiamond, 1965). Findings from the earliest experiments centred around the vicarious discovery that some people who stuttered experienced improved fluency when they put on headphones and heard their speech played back to them with a slight time delay. (Some readers may already have experienced DAF as an echo effect when speaking on a poor transcontinental telephone line.) Commonly, DAF also results in reduced fluency in nonstuttering speakers (Fukawa, Yoshioka, Ozawa, & Yoshida, 1988; Stuart, Kalinowski, Rastatter, & Lynch, 2002), although
Fukawa et al. observed that people who stutter were significantly more likely to be affected by DAF than nonstutterers, and that male nonstutterers were more susceptible to the effect than females. Most noticeably, Goldiamond (1965) found a tendency for speakers to slow their rate of speech in an effort to counteract the disruptive influences of the delayed feedback. Particularly, at around 250 ms delay (0.25 of a second) a prolonged speech pattern was produced, where vowels became disproportionately more stretched than consonants. The further finding that the extent of the prolonged speech could be controlled by altering the delay times lead to the development of a number of “prolonged speech” programs which used DAF in a systematic way to elicit fluent speech. (See chapter 12 as to how prolonged speech programs have developed.) During the early stages of therapy, DAF was set to encourage excessive prolongation, usually around 250 ms. When clients were able to demonstrate 100 percent fluency in their speech at this delay setting, the next stepwise decrease in DAF (usually in 50 ms increments) was introduced to encourage a slightly faster rate of speech. Again, the client learned to control fluency using decreased prolongation associated with the reduced DAF. The procedure was then repeated at incrementally reduced delay levels, with clients having to demonstrate completely fluent speech at each one before progressing to the next decreased DAF setting. Eventually, the client reached the point where he was able to maintain fluency without any delay in auditory feedback (e.g., Curlee & Perkins, 1969, 1973). At this time it was thought that the fluency enhancing effects of DAF could be explained simply as byproducts of the slower rate speech that it produced. During the mid-1970s and through the 1980s there was a lull in DAF research as clinicians looked to alternative ways of slowing speech for therapy. It was not until the early 1990s when a resurgence of interest occurred, largely driven by findings that increased fluency could indeed result under DAF at normal and even fast rates of speech (e.g., Stuart & Kalinowski, 1996). This finding has led to a new generation of clinicians and researchers becoming interested in DAF as a treatment option for stuttering. We examine the more recent applications in relation to therapy elsewhere (see chapter 14).
Aside from the therapeutic implications, the early findings that DAF could enhance fluency for at least some people who stutter led to a number of theories of stuttering, based on the assumption that timing perception is disturbed.
There is a range of evidence that points to the notion that stuttering is associated with disrupted auditory processing, although the exact nature of this disruption remains obscure. Shadowed speech can produce high levels of fluency, but this may have little to do with any timing misperception induced by a faulty processing system; we know that unison speech similarly produces high levels of fluency with no delay. We also know that DAF and FAF can have dramatic fluency enhancing effects for some people who stutter, yet others remain DAF and FAF negative, for reasons which are currently unknown. Also, and as we see in chapter 14, there are reports from some people who stutter that the effects of altered feedback can wear off over time. Perhaps these findings suggest that distraction may play as big a part in inducing fluency as correcting any misperception of a disrupted auditory timing processing system? As we see in chapter 2, brain studies have shown differences in functioning between people who stutter and control group
speakers across linguistic and motor areas. The dichotic listening procedure provides one testable method of determining hemispheric dominance for linguistic decoding, and findings from such studies, though far from definitive, lend tentative support to the idea that auditory processing too might be a product of the right hemisphere, at least in some people who stutter. One of the biggest issues faced is that auditory processing is just one part of the communication chain and does not occur in a vacuum. Both production and perception theories must allow for the fact that one is affected by the other. This can lead to a chicken and egg situation, as brought into sharp focus in the criticism of Harrington’s theory of linguistic rhythm and auditory feedback: it can be almost impossible to determine what is cause and what is effect.
The deaf population is the only one in which stuttering is underrepresented.
Stuttered speech may be improved under a number of conditions which serve to disrupt or alter auditory feedback, such as masking, delayed auditory feedback (DAF), frequency altered feedback (FAF), choral and unison speech.
People who stutter may be more reliant on auditory feedback than those who do not stutter.
The Buency enhancing effects of altered feedback devices may work by convincing the brain that the speaker© speech is actually the product of an external speech source.
There is evidence that, like processing for speech production, auditory processing for speech may be a product of right hemisphere processing amongst older children and adults who stutter.
It has been argued that stuttering might result due to misperception of the timing of stressed vowels in speech (Harrington, 1988).
It is possible that auditory processing anomalies may in fact merely represent Cknock-onCeffects of a dehcit that are in essence production based.
Harrington, J. (1988). Stuttering, delayed auditory feedback and linguistic rhythm.
Journal of Speech and Hearing Research, 31, 36-47.
Aside from the theoretical implications, this thought-provoking paper provides a well- explained introduction into the links between perception and production aspects of speech processing in stuttering.
Kalinowski, J., Armson, J., Roland-Mieszowski, M., & Stuart, A. (1993). Effects of alterations in auditory feedback and speech rate on stuttering frequency. Language and Speech, 36, 1-16.
As with the selected reading list from chapter 14 which discusses auditory feedback from a therapeutic perspective, there is a wide range of Kalinowski and colleagues’ work that could have been included here. This one is an early but influential article on the discovery that altered feedback could reduce stuttering, without invoking a slowed speech rate.
Rosenfield, D.B., & Jerger, J. (1984). Stuttering and auditory function. In R. Curlee and W. H. Perkins (Eds.), The nature and treatment of stuttering: New directions (pp. 73-88). San Diego, CA: College Hill Press.
Much of the work on stuttering and auditory function was undertaken in the 1970s and early 1980s. Despite its age, this is still a very good source for earlier material on the subject of auditory processing and covers a lot of ground. There is currently no similar but more recent publication on the subject