The term stuttering is most commonly associated with involuntary sound repetition, but it also encompasses the abnormal hesitation or pausing before speech, referred to by stutterers as blocks, and the prolongation of certain sounds, usually vowels. Much of what constitutes "stuttering" cannot be observed by the listener; this includes such things as sound and word fears, situational fears, anxiety, tension, self-pity, stress, shame, and a feeling of "loss of control" during speech. The emotional state of the individual who stutters in response to the stuttering often constitutes the most difficult aspect of the disorder. The term "stuttering", as popularly used, covers a wide spectrum of severity: it may encompass individuals with barely perceptible impediments, for whom the disorder is largely cosmetic, as well as others with extremely severe symptoms, for whom the problem can effectively prevent most oral communication.
Stuttering is generally not a problem with the physical production of speech sounds (see Voice disorders) or putting thoughts into words (see Dyslexia, Cluttering). Despite popular perceptions to the contrary, stuttering does not affect and has no bearing on intelligence. Apart from their speech impairment, people who stutter are normal. Anxiety, low confidence, nervousness, and stress therefore do not cause stuttering, although they are very often the result of living with a highly stigmatized disability.
The disorder is also variable, which means that in certain situations, such as talking on the telephone, the stuttering might be more severe or less, depending on the anxiety level connected with that activity. In other situations, such as singing (as with country music star Mel Tillis or pop singer Gareth Gates) or speaking alone (or reading from a script, as with actor James Earl Jones), fluency improves. (It is thought that speech production in these situations, as opposed to normal spontaneous speech, may involve a different neurological function.) Some very mild stutterers, such as Bob Newhart, have used the disorder to their advantage, although more severe stutterers very often face serious hurdles in their social and professional lives. Although the exact etiology of stuttering is unknown, both genetics and neurophysiology are thought to contribute. Although there are many treatments and speech therapy techniques available that may help increase fluency in some stutterers, there is essentially no "cure" for the disorder at present.
Incidence and prevalence
The prevalence of stuttering in preschool children is about 2.5%, that is, about 1 young child in 40 now stutters. The incidence is about 5%, or 1 in 20 children stutter at some point in childhood.
About 1% of adults stutter. The figure found in a recent study was 0.73%, or about one in 135 adults. About 80% of adult stutterers are men and about 20% are women.
Studies in years past claimed that some countries had higher or lower rates of stuttering, or that some cultures had no stutterers at all. These studies are generally discounted now, although there are likely more adult stutterers in countries with less speech therapy.
Other fluency disorders
This article is about developmental stuttering, that is, stuttering that originates when a child is learning to speak and develops as the child matures into adulthood. Several other speech disorders resemble stuttering:
- Parkinson's speech
- Essential tremor
- Spasmodic dysphonia
- Social anxiety
Head injuries and strokes can cause repetitions, prolongations, and blocks. Rarer still are stutters induced by specific medications. Medications such as antidepressants, antihistamines, tranquilizers and selective serotonin reuptake inhibitors have been known to affect speech in this way. While these afflictions create stutter-like conditions they do not create a stutter in the traditional sense. However, these neurogenic stutterers lack the struggle behavior and fears and anxieties of developmental stuttering. Developmental stutterers can fluently speak certain memorized phrases, such as the "Pledge of Allegiance." Neurogenic stutterers are disfluent on everything. Developmental stutterers can speak fluently in certain (typically low-stress) situations. Neurogenic stutterers are disfluent everywhere.
Rarely, traumatic experiences caused an adult to begin stuttering. Psychogenic stuttering typically involves rapid, effortless repetitions of initial sounds, without struggle behavior.
No single, exclusive cause of stuttering is known. A variety of hypotheses and theories suggest multiple factors contributing to stuttering.
Stuttering has been correlated with certain genes; however, a genetic cause for stuttering has yet to be proven. Many studies have investigated stuttering in families, yet typically have yielded results that could be interpreted as either genetic or social environment ("nature" or "nurture").
Neurology of adult stuttering
Brain scans of adult stutterers have found several neurological abnormalities:
- During speech adult stutterers have more activity in their right hemispheres, which is associated with emotions, than in their left hemispheres, which is associated with speech. Non-stutterers have more left-hemisphere activity during speech. It is unknown whether this abnormal hemispheric dominance results from something wrong with stutterers' left-hemisphere speech areas, with right-hemisphere area unsuited for speech taking over speech tasks; or whether the unusual right-hemisphere activity is related to fears, anxieties, or other emotions stutterers associate with speech.
- During speech, adult stutterers have central auditory processing underactivity. One study suggested that stutterers may have an inability to integrate auditory and somatic processing, i.e., comparing how they hear their voices and how they feel their muscles moving.
- A brain scan study examined the planum temporale (PT), an anatomical feature in the auditory temporal brain region. Typically people have a larger PT on the left side of their brains, and smaller PT the right side (leftward asymmetry). A brain scan study found that stutterers' right PT is larger than their left PT (rightward asymmetry).
- Adult stutterers have overactivity in the left caudate nucleus speech motor control area. Because stuttering is primarily overtense, overstimulated respiration, vocal folds, and articulation (lips, jaw, and tongue) muscles, it should be no surprise that the brain area that controls these muscles is overactive.
No brain scan studies have been done of stuttering children. It is unknown whether stuttering children have neurological abnormalities.
Another prominent view is that stuttering is caused by neural synchronization problems in the brain. Recent research indicates that stuttering may be correlated with disrupted fibers between the speech area and language planning area, both in the left hemisphere of the brain. Such a disruption could potentially be due to early brain damage or to a genetic defect.
The first brain imaging studies in stuttering were done on two subjects using SPECT scanning before and after the administration of haloperidol. The researchers found that the subjects with stuttering had less blood flow in the Broca's and Wernicke's area and associated this with dysfluency. They found that haloperidol not only reduced stuttering but reversed this functional abnormality. Numerous PET and functional MRI studies have presented data that is in agreement with this first study.
Volumetric MRI studies have found that portions of the Broca's and Wernicke's areas are smaller in people who stutter and this corrolates well with the hypometabolism in these two brain regions. New forms of structural MRI have found that there is a disconnection in white matter fiber tracts in the left hemisphere and greater numbers of white matter fiber tracts in the right hemisphere.
In certain situations, such as talking on the telephone, stuttering might increase, or it might decrease, depending on the anxiety level connected with that activity.
Under stress, people's voices change. They tense their speech-production muscles, increasing their vocal pitch. They try to talk faster. They repeat words or phrases. They add interjections, also known as "filler words", such as "uh." These are normal dysfluencies. A study found that under stress, non-stutterers went from 0% to 4% dysfluencies, for the simple task of saying colors. Stutterers went from 1% to 9%.
Stuttering reduces stress 10%, as measured by systolic blood pressure. But stuttering causes stress in listeners Stuttering appears to reduce stress temporarily, but then cause stress, creating a cyclical pattern in which the stutterer stutters on the first syllable of the first word, then says the rest of the word and several more words fluently, then stutters again, then says a few more words fluently, and so on.
One study found that developmental stuttering and Tourette syndrome may be pathogenetically related. Tics are exacerabated by stress, and when the affected person tries harder to control the undesired movement, the conditions can become more pronounced.
Onset and development
|Development of a stutter|
|Source: Onset and Development (2001). Retrieved March 20, 2005|
Stuttering is a developmental disorder. Children develop capabilities in a certain order, e.g., most children crawl before they walk. An unknown factor or combination of factors causes some children's speech to develop abnormally. As the child grows what appeared as a minor dysfunction can develop into a major disability.
The mean onset of stuttering is 30 months, or two and a half years old. Stuttering rarely begins after age six.
65% of preschoolers who stutter spontaneously recover, in their first two years of stuttering. Only 18% of children who stutter five years recover spontaneously.The peak age of recovery is 3.5 years old. By age six, a child is unlikely to recover without speech therapy.
Among preschoolers, boys who stutter outnumber girls who stutter about two to one, or less.But more girls recover fluent speech, and more boys don't. By fifth grade the ratio is about four boys who stutter to one girl who stutters. This ratio remains into adulthood.
Some pediatricians tell parents to "wait and see" if a child outgrows stuttering on his own. It has been recommended that children who stutter should instead be treated by a speech-language pathologist as soon as possible.
All children experience normal dysfluencies as they learn to talk, which they will outgrow. A current issue is whether stuttering develops progressively from normal childhood dysfluencies, or whether stuttering is something entirely different. Many parents are unsure whether their child's dysfluencies are normal, or whether he or she is beginning to stutter. The Stuttering Foundation of America has written and video materials to help parents differentiate normal dysfluencies from beginning stuttering. Or parents can consult a speech-language pathologist.
To find a speech-language pathologist for your child, start by calling your school. American schools provide free speech therapy to children as young as three years old.
As speech and language are difficult and complex skills to learn, almost all children have some difficulty in developing these skills. This results in normal dysfluencies that tend to be single-syllable, whole-word or phrase repetitions, interjections, brief pauses, or revisions. In the early years, a child will not usually exhibit visible tension, frustration or anxiety when speaking dysfluently and most will be unaware of the interruptions in their speech. With young stutterers, their dysfluency tends to be episodic, and periods of stuttering are followed by periods of relative fluency. This pattern remains through all stages of a stutterer's development, but as the stutter develops, the dysfluencies tend to develop more into repetitions and sound prolongations, often combined together (e.g., "Lllllets g-g-go there").
Usually by the age of 6, a stutter is exacerbated when the child is excited, upset or under some type of pressure. Also around this age, a child will start to become aware of problems in his or her speech. After this age, stuttering includes repetitions, prolongations, and blocks. It also becomes more and more chronic, with longer periods of disfluency. Secondary motor behaviors (eye blinking, lip movements, etc.) may be used during moments of stuttering or frustration. Also, fear and avoidance of sounds, words, people, or speaking situations usually begin at this time, along with feelings of embarrassment and shame. By age 14 , the stutter is usually classified as an "Advanced stutter," characterized by frequent and noticeable interruptions, with poor eye contact and the use of various tricks to disguise the stuttering. Along with a mature stutter come advanced feelings of fear and increasingly frequent avoidance of unfavorable speaking situations. Around this time many become fully aware of their disorder and begin to identify themselves as "stutterers." With this may come deeper frustration, embarrassment and shame.
It is important to note that stuttering does not affect intelligence and that stutterers are sometimes wrongly perceived as being less intelligent than non-stutterers. This is mainly due to the fact that stutterers often resort to a practice called word substitution, where words that are difficult for a stutterer to speak are replaced with less-suitable words with one or two syllables that are easier to pronounce. This often leads to simple, short, and awkward sentences which give an impression of feeble mindedness. A stutter may take longer to answer a question or respond, because it takes them longer to get a word out. They have to think about every word there going to say and how they might modify that word so that a stuttering moment won't occur or won't be as intense. Stutters often feel great frustration because they know what they want to say, but can not translate it into spoken language using the same words they are thinking of or the way they would like to. They may also feel that non-stutters do not have the patience to wait and listen for the prolonged time it could take them to complete what they want to say. Stuttering is a communicative disorder that affects speech; it is not a language disorder—although a person's use of language is often affected or limited by a stutter.
Core and secondary behaviors
Core stuttering behaviors include disordered breathing, phonation (vocal fold vibration), and articulation (lips, jaw, and tongue). Typically these muscles are overtensed, making speech difficult or impossible.
Secondary stuttering behaviors are unrelated to speech production. Such behaviors include physical movements such as eye-blinking or head jerks; avoidance of feared words, such as substitution of another word; interjected "starter" sounds and words, such as "um," "ah," "you know,"; and vocal abnormalities to prevent stuttering, such as speaking in a rapid monotone, or affecting an accent.
Speech fluency consist of three variables: continuity, rate, and ease of speaking. Continuity refers to speech that flows without hesitation or stoppage. Rate refers the speed in which the words are spoken. For English-speaking adults, the mean overall speaking rate is 170 words per minute (w/m), substantially quicker than the approximately 120 w/m that stutterers produce.1 Ease of speaking refers to the amount of effort being expended to produce speech. Fluent speakers put very little muscular or physical effort into the act of speaking, while stutterers exert a relatively large amount of muscular effort to produce the same speech. In addition to the physical effort involved in producing speech, the mental effort is usually much greater in stutterers than non-stutterers.
Disfluency in speech, including repetitions and prolongations, is normal for all speakers, but stuttering is distinct from normal disfluency in that it occurs with greater frequency and severity—the disfluencies occur much more often and tend to last longer with more strain. The types of disfluencies are also markedly different: normal disfluencies tend to be a repetition of whole words or the interjection of syllables like "um" and "er," while stuttering tends to be repetition and prolongation of sounds and syllables. The various behaviors that can disrupt the smooth flow of speech include repetition, prolongations, and pauses:
- Repetition occurs when a unit of speech, such as a phrase, word, or syllable, is superfluously repeated. (Examples of repetition for a phrase would be, "I want.. I want.. to go.. I want to go to the store," or, "I want to go to the - I want to go to the store." A word repetition would often resemble, "I want to-to-to go to the store," and a syllable or sound repetition being, "I wa-wa-want to go to the store," or, "I w-w-want to g-go to the store.") Repetition occurs in the speech of both stutterers and non-stutterers, but non-stutterers are less likely to repeat shorter units of speech, mainly repeating phrases and sometimes words but rarely syllables. Non-stutterers will also, in the majority of cases, repeat the unit once or twice as opposed to the 6 or so times common from stutterers.
- Prolongations are one of the least typical behavior exhibited by stutterers. Prolongations normally happen with child stutterers and with the sounds /θ/, /ʃ/, /v/, and any other fricative consonant or vowel. With stutterers, prolonging a sound sometimes leads to a pitch and volume increase.
- Pauses are also a common source of disfluency in
both stutterers and non-stutterers. Most pauses can be
divided into two categories: filled pauses and unfilled
- Unfilled pauses are extraneous portions of silence in the ongoing stream of speech. These pauses differ from the pauses that punctuate normal speech, where they reflect common sentence structure or are used to add a particular rhythm or cadence to speech. Unfilled pauses by stutterers are usually unintentional and may cause the larynx to close, restricting the flow of air necessary for speech. Stutterers refer to this as "blocking". (See Blocking.)
- Filled pauses are interjections typical in normal speech like "um", "uh", "er", and so on. In speech these serve as a kind of place-holder—a way a speaker lets listeners know that he or she still has the floor and is not finished speaking. In addition to being used as a way of preempting interruption, they are also used by stutterers as a way of easing into fluency or deflecting embarrassment when they cannot speak fluently.
When stuttering, stutterers will often use nonsense syllables or less-appropriate (but easier to say) words to ease into the flow of speech. Stutterers also may use various personal tricks to overcome stuttering or blocks at the beginning of a sentence, after which their fluency can resume. Finger-tapping or head-scratching are two common examples of tricks, which are usually idiosyncratic and may look unusual to the listener. In addition to word substitution or the use of filled pauses, stutterers may also use starter devices to help them ease into fluency. A common practice is the timing of words with a rhythmic movement or other event. For instance, stutterers might snap their fingers as a starter device at the beginning of speech. These devices usually do work, but only for a short amount of time. Often a person who stutters will do something at some point to avoid, postpone, or disguise a stutter and, by coincidence, will not stutter. The stutterer then makes a cause-effect connection between that new behavior and the release of the stuttering, and the behavior becomes a habit.
As stutterers often resort to word substitution in order to avoid stuttering, some develop an entire vocabulary of easy-to-pronounce words in order to maintain fluent speech—sometimes so well that no one, not even their spouses or friends, know that they have a stutter. Stutterers who successfully use this method are called "covert stutterers" or "closet stutterers". While they do not actually stutter in speech they nevertheless suffer greatly from their speech disorder. The extra effort it takes to scan ahead for feared words or sounds is stressful, and the replacement word is usually not as adequate a choice as the stutterer originally intended. Famously, some stutterers drastically limit their options when dealing with employees at given establishments; only eating cheeseburgers at fast-food restaurants, ordering toppings they do not like on pizzas, or getting a style of haircut they do not want as a by-product of their inability to pronounce certain words. Some stutterers have even changed their own given name because it contains a difficult-to-pronounce sound and frequently leads to embarrassing situations.
Although this action may appear unusual or unreasoned to a fluent speaker, to a stutterer they come as second nature: due to the embarrassment and fear associated with speaking, many stutterers will wish to hide their stutter from listeners. This is the prime reason for avoidance.
When the behaviors of a stutter are infrequent, brief, and are not accompanied by substantial avoidance behavior, the stutter is usually classified as a mild or a non-chronic stutter. Non-chronic stuttering is often called "situational stuttering" because the afflicted person generally has difficulty speaking only in isolated situations—usually during public speaking or other stressful activities—and outside of these situations the person generally does not stutter. When the behaviors are frequent, long in duration, or when there are visible signs of struggle and avoidance behavior, the stutter is classified as a severe or chronic stutter. Unlike mild or situational stuttering, chronic stuttering is present in most situations, but can be either exacerbated or eased depending on different conditions (see Positive conditions). Severe stutters often, but not always, are accompanied by strong feelings and emotions in reaction to the problem such as anxiety, shame, fear, self-hatred, etc. This is usually less present in mild stutterers and serves as another criteria by which to define stutters as mild or severe. Another way of discerning between the two severities is by percentage of disfluency per 100 words. When a speaker experiences disfluencies at a rate around 10%, they usually have a mild stutter, while 15% or more is usually indicative of a severe stutter.In addition to the disfluency, many people who stutter display secondary motor behaviors. Observers often notice muscles tensing up, facial and neck tics, excessive eye blinking, and lip and tongue tremors. In extreme cases entire body movements may accompany stuttering. Most common with stutterers is the inability to maintain eye contact with the listener, which in many cultures may hamper the growth of personal or professional relationships.
It is worth noting that the severity of a stutter is not constant and that stutterers often go through weeks or months of substantially increased or decreased fluency. Stutterers universally report having "good days" and "bad days" and report dramatically increased or decreased fluency in specific situations. Below is an overview of the circumstances that harm and help the fluency of most stutterers:
Subtle changes in mood or attitude often greatly increase or decrease fluency, with many stutterers developing tricks or methods to achieve temporary fluency. Stutterers commonly report dramatically increased fluency when singing, whispering or starting speech from a whisper, speaking extremely slowly, speaking in chorus, speaking without hearing their own voice (e.g., speaking over loud music), speaking with a metronome or other rhythm, speaking with an artificial accent or voice, speaking in a foreign dialect, or when speaking while hearing their own voice with a minuscule delay or pitch change. (See Treatments.) Stutterers also display increased fluency when speaking to nonjudgmental listeners, such as pets, children, or speech pathologists. It is perhaps most interesting to note that most stutterers experience extraordinary levels of fluency when talking to themselves. A rare few even experience increased fluency when they exclusively "have the floor" (public speaking or teaching), when they are intoxicated, or when they are explicitly trying to stutter. There is no universally accepted explanation for these phenomena. Unfortunately, non-stutterers often interpret such instances of fluency as evidence that a stutterer can in fact speak "normally", which may partly explain the popular belief that stuttering is a transient nervous condition. Nevertheless, the appearance of fluency in certain situations in no way indicates that a stutterer can consciously produce similar fluency at other times, or that the disorder is any less "real".
All speech is more difficult when under pressure. Commonly, social pressures, like speaking to a group, speaking to strangers, speaking on the telephone, or speaking to authority figures, will irritate and make worse a stutter. Also, time pressure often exacerbates a stutter. Pressure to speak quickly when answering or conversing is usually very difficult for a stutterer, particularly on the telephone where stutterers do not have body language to aid themselves. This usually leaves dead silence in the place of nonverbal communication, which will indicate to the listener that the stutterer is not there or the line has been disconnected. Other time pressures will also worsen a stutter, such as saying one's own name, which must be done without hesitation to avoid the appearance that one does not know his or her own name, repeating something just said, or speaking when somebody is waiting for a response. Getting hot or sweaty, heart pounding, and butterflies in the stomach are natural - the body responds to strong emotions. The problem is they tend to make things worse by making one even more self-conscious. By 16 years of age, a person who stammers will have had a great deal of experience of stammering and, for many, these experiences have been quite negative. The ever-present threat of being teased, bullied or not accepted takes a tremendous toll on the stutterer's everyday life. A person dealing with this may often feel like he or she has limited opportunities and options since today speaking out in public is almost a necessity, especially when one wants to be successful in one's career.
A wide variety of stuttering treatments are available. No single treatment is effective for every stutterer. This suggests that stuttering doesn't have a single cause, but rather is the result of several interacting factors. If so, then combining several stuttering treatments may be more effective than relying on a single treatment. Many speech-language pathologists favor such an integrated approach to stuttering, and tailor therapy to each individuals' needs.
Fluency shaping therapy
Fluency shaping therapy trains stutterers to speak fluently by relaxing their breathing, vocal folds, and articulation (lips, jaw, and tongue).
Stutterers are usually trained to breathe with their diaphragms, gently increase vocal fold tension at the beginning of words (gentle onsets), slow their speaking rate by stretching vowels, and reduce articulatory pressure. The result is slow, monotonic, but fluent speech. This abnormal-sounding speech is used only in the speech clinic. After the stutterer masters these target speech behaviors, speaking rate and prosody (emotional intonation) are increased, until the stutterer sounds normal. This normal-sounding, fluent speech is then transferred to daily life outside the speech clinic.
A study followed 42 stutterers through the three-week fluency shaping program. The program also included psychological treatment to reduce fears and avoidances, discussing stuttering openly, and changing social habits to increase speaking. The therapy program reduced stuttering from about 15–20% stuttered syllables to 1–2% stuttered syllables. 12 to 24 months after therapy, about 70% of the stutterers had satisfactory fluency. About 5% were marginally successful. About 25% had unsatisfactory fluency.
Stuttering modification therapy
The goal of stuttering modification therapy is not to eliminate stuttering. Instead, the goals are to modify one's moments of stuttering, so that their stuttering is less severe; and reduce their fear of stuttering, while eliminating avoidance behaviors associated with this fear. Unlike fluency shaping therapy, stuttering modification therapy assumes that adult stutterers will never be able to speak fluently, so the goal is to be an effective communicator despite stuttering.
Stuttering modification therapy has four stages:
- In the first stage, called identification, the stutterer and clinician identify the core behaviors, secondary behaviors, and feelings and attitudes that characterize your stuttering.
- In the second stage, called desensitization, the stutterer tells people that he is a stutterer, freezes core behaviors, and intentionally stutters ("voluntary stuttering").
- In the third stage, called modification, the stutterer learns "easy stuttering." This is done by "cancellations" (stopping in a dysfluency, pausing a few moments, and saying the word again); "pull-outs," or pulling out of a dysfluency into fluent speech; and "preparatory sets," or looking ahead for words you're going to stutter on, and using "easy stuttering" on those words.
- In the fourth stage, called stabilization, the stutterer prepares practice assignments, makes preparatory sets and pull-outs automatic, and changes his self-concept from being a person who stutters to being a person who speaks fluently most of the time but who occasionally stutters mildly.
Only one long-term efficacy study of a stuttering modification therapy program has been published in a peer-reviewed journal. This study concluded that the program "appears to be ineffective in producing durable improvements in stuttering behaviors."
Several dopamine antagonist medications reduced stuttering in double-blind, placebo-controlled studies, including Haloperidol (Haldol), risperidone (Risperdal), and olanzapine (Zyprexa). These medications generally reduce stuttering 33–50%. Haldol is rarely, if ever, used by stutterers due to severe side effects. Risperdal and Zyprexa have fewer side effects. None of these drugs are FDA-approved for stuttering.
Clinical trials are underway for what could be the first FDA-approved anti-stuttering medications. Pagoclone is a gamma amino butyric acid (GABA) selective receptor modulator. Dopamine and GABA are both neurotransmitters.
Other medications can increase stuttering, or even cause a person to start stuttering. Such medications include dopamine agonists such as Ritalin and selective serotonin reuptake inhibitors (SSRI) such as Prozac and Zoloft.
Changing how a stutterer hears their voice usually improves their fluency. This altered auditory feedback effect appears to be related to the central auditory processing disorder seen in adult stutterers' brain scans; however, more research is needed in this area.
The altered auditory feedback effect can be produced by speaking in chorus with another person, or hearing one's voice echo in a well. However, this effect is now usually produced with electronic devices. The three most common types of altered auditory feedback are:
- Delayed auditory feedback (DAF), which delays the user's voice to their ear a fraction of a second.
- Frequency-shifted auditory feedback (FAF), which changes the pitch of the user's voice in their ear.
- Masking auditory feedback (MAF), which produces a synthesized sine wave in the user's ear at the frequency at which the user's vocal folds are vibrating.
DAF and FAF immediately reduce stuttering about 70–80%, at normal speaking rates, without training or therapy, and with normal-sounding speech. No study has measured the effects of MAF, but MAF has an advantage over DAF and FAF in that it can pull users out of silent blocks.
Several long-term studies found excellent results when DAF devices were combined with fluency shaping therapy. Two studies investigated long-term effects of anti-stuttering devices without therapy. In the first study, nine adult stutterers used DAF devices thirty minutes per day, for three months.
The immediate result was 70% reduction in stuttered words. Three months later there was no statistically significant "wearing off" of effectiveness when using the devices. When not using the devices the subjects stuttered 55% less. In other words, the subjects developed carryover fluency the rest of the day, when they weren't using the devices, training the subjects to no longer need the devices.
In a second study, nine stutterers used a DAF/FAF device about seven hours per day. Their fluency was measured after four months and after twelve months.
The second device reduced stuttered syllables about 80%, when the device was used. This effect was maintained over the twelve months, with no statistically significant "wearing off" of effectiveness. But no carryover effect was seen. In other words, when the subjects removed the device they went right back to stuttering.
About ten American states provide DAF/FAF anti-stuttering telephone devices free to qualified stutterers.
Media publicity about stuttering "cures"
Reports about successful stuttering treatment are not rare in contemporary media, particularly in television news programs and talk shows, since stories about recovery from stuttering have a strong emotional appeal. Media reports have typically focused on dramatic treatments such as the fluency-shaping method of therapy and, more recently, electronic fluency aids. Although such treatments may increase fluency in some stutterers, media reports seldom examine either the long-term efficacy of these treatments or their effect on stutterers of differing severity. As a result, media reports usually imply that such therapies are miracle cures. (Significantly, licensed speech pathologists who provide these treatments routinely emphasize that they are not "cures".) Indeed, anecdotal evidence suggests that media attention to such treatments may actually have a negative effect on the public perception of stutterers: for example, after an uncritical media report creates the myth of a newly available "cure", non-stuttering family members and workplace superiors may penalize or put pressure on a stutterer for not having his or her speech impediment "cured".
Therapies for pre-school children
In the past, stuttering children received indirect therapy, which changed the parents' speech behaviors. Such indirect therapy has been proven ineffective. For example, popular websitesadvise that parents should "speak slowly and in a relaxed manner"; make positive statements such as praise, and refrain from negative statements such as criticism; "pause before responding to your child's questions or comments," etc. Yet more than a dozen studies found that such parental behavior had no effect on children's stuttering—or the effect was the opposite of what the parents intended. For example, when parents spoke slower, their children spoke faster and their stuttering increased.
Speech-language pathologists now recommend direct therapy with young children. The target speech behaviors are similar to fluency shaping therapy, but various toys and games are used. For example, a turtle hand puppet may be used to train the slow speech with stretched syllables goal. When the child speaks slowly, the turtle slowly walks along. But when the child talks too fast, the turtle retreats into his shell.
Therapies for school-age children
A study of 98 children, 9 to 14 years old, compared three types of stuttering therapy.One year after therapy, the percentage of children with disfluency rates under 2% were:
- 48% of the children who were treated by a speech-language pathologist.
- 63% of the children whose parents were trained by a speech-language pathologist to do speech therapy at home (but the children weren't treated by the speech-language pathologists).
- 71% of the children who were treated by a computer-based anti-stuttering program, with minimal interaction from speech-language pathologists.
The results for children with disfluency rates under 1% were even more striking:
- 10% of the children from the clinician-based program.
- 37% of the children from the "parent-based" program.
- 44% of the children from the computer-based program.
In other words, the computers were most effective, the parents next most effective, and the speech-language pathologists were least effective. At the 1% disfluency level, the computers and the parents were about four times more effective than the speech-language pathologists.
Parents should realize that school speech-language pathologists are trained to treat a wide variety of speech and language disorders. Many don't have training or experience with stuttering, and few specialize in stuttering. Many school districts are underfunded and school speech-language pathologists have caseloads of 40 or more children, seeing each child for perhaps twenty minutes twice a week, or even doing group therapy with several children who have different communication disorders. Parents whose child's speech isn't improving may want to consider additional treatments beyond their school's speech-language pathologist:
- Seeing a board-certified Fluency Specialist.
- Asking the school speech-language pathologist to train the parents to do therapy at home, increasing therapy time to perhaps twenty minutes twice a day, every day.
- Buying (or asking the state to provide) a computer-based or electronic speech therapy device, that the school speech-language pathologist can train the parent to do therapy with the child at home.
Therapies for teenagers
One strategy for treating teenagers who stutter is to include peers in therapy. This is usually the teenager's best friend. This can improve the stuttering teenager's motivation in therapy, and also the friend can give reminders outside of therapy for the stuttering teenager to use his speech target behaviors.
Another strategy is to encourage a stuttering teenager to develop a passion for an activity requiring speech. This could be getting involved in the school's drama club, or doing a science project about stuttering.
Stuttering and society
For centuries stuttering has often featured prominently in both popular culture and in society at large. Because of the unusual-sounding speech that is produced, as well as the behaviors and attitudes that accompany a stutter, stuttering has frequently been a subject of scientific interest, curiosity, discrimination, and ridicule. Stuttering was, and essentially still is, a riddle with a long history of interest and speculation into its causes and cures. Stutterers can be traced back centuries to the likes of Demosthenes, Aesop, and Aristotle—some interpret a passage of the Bible to indicate Moses also to have been a stutterer. Misinformation and superstition have influenced society's perceptions of the causes and remedies of a stutter, as well as the intelligence and perceived disposition of people afflicted with the disorder.The well-known author of Alice in Wonderland, Lewis Carroll hoped to become a priest but was not allowed to because of his stuttering. In response, he wrote a poem which mentions stuttering:
Learn well your grammar / And never stammer / Write well and neatly / And sing soft sweetly / Drink tea, not coffee; Never eat toffy / Eat bread with butter / Once more don't stutter.
(Excerpt from Rules & Regulations) Carroll's well-known stuttering trait is subliminally referenced in Alice, which features a Dodo bird in one scene. As Martin Gardner pointed out in The Annotated Alice, the bird is drawn to vaguely resemble Carroll, and Carroll often tended to say his own real last name "Do-Do-Dodgson". (See Dodo (Alice's Adventures in Wonderland)).
Partly due to a perceived lack of intelligence because of his stutter, the man who became the Roman Emperor Claudius was initially shunned from the public eye and excluded from public office. This exclusion from public life suited his inclination towards the academic and gave him time for study. His infirmity is also thought to have saved him from the fate of many other Roman nobles during the purges of Tiberius and Caligula. By studying history, Claudius became very knowledgeable about governmental institutions, which later aided him as an emperor. Isaac Newton, the famous English scientist who developed the law of gravity, also had a stutter. Other famous Englishmen who stammered were King George VI and Prime Minister Winston Churchill, who led the UK through World War II. Although George VI went through years of speech therapy for his stammer, Churchill thought that his own very mild stutter added an interesting element to his voice: "Sometimes a slight and not unpleasing stammer or impediment has been of some assistance in securing the attention of the audience…"
Ancient views of stuttering
For centuries "cures" such as speaking with a pebble in the mouth (as per the legendary orator Demosthenes), consistently drinking water from a snail shell for the rest of one's life, "hitting a stutterer in the face when the weather is cloudy", strengthening the tongue as a muscle, and various herbal remedies were often used6 ; clearly to little effect.
Similarly, in the past people have subscribed to various theories about the causes of stuttering which today one might consider odd. Proposed causes of stuttering have included tickling an infant too much, eating improperly during breastfeeding, allowing an infant to look in the mirror, cutting a child's hair before the child spoke his or her first words, having too small a tongue, or the "work of the devil."
Roman physicians attributed stuttering to an imbalance of the four bodily humors: yellow bile, blood, black bile, and phlegm. Humoral manipulation continued to be a dominant treatment for stuttering until the eighteenth century. Italian pathologist Giovanni Morgagni attributed stuttering to deviations in the hyoid bone, a conclusion he came to via autopsy. Later in the century, surgical intervention, via resection of a triangular wedge from the posterior tongue to prevent spasms of the tongue, was also tried.
Blessed Notker of St. Gall (ca. 840–912), called Balbulus (“The Stutterer”) and described by his biographer as being "delicate of body but not of mind, stuttering of tongue but not of intellect, pushing boldly forward in things Divine," was invoked against stammering.
Stuttering in the media
In more recent times, movies such as A Fish Called Wanda (1988) and A Family Thing (1996) have dealt with contemporary reactions to and portrayals of stuttering. In A Fish Called Wanda, a lead character, played by Michael Palin, has a severe stutter and low self-esteem. His character—who is socially awkward, nervous, an animal lover, and reclusive—portrays a prevalent stereotypical image of stutterers. The three other characters in the movie generally make up the spectrum of reactions to stuttering: Jamie Lee Curtis's character is sympathetic and sees past it, John Cleese's character is polite but indifferent, and Kevin Kline's is malicious and sadistic. Upon release the film caused controversy among some stutterers who disliked the film for its portrayal of Palin's character as a pushover amid the bullying his character receives, and received favor from others who valued the film for showing the difficulties stutterers commonly face. Palin, whose father was a stutterer, stated that in playing the role he intended to show how difficult and painful stuttering can be. He also donated to various stuttering-related causes and later founded the Michael Palin Centre for Stammering Children in London.
The 1983 movie The Right Stuff referenced the real-life stuttering problem of John Glenn's wife Annie, and how it rendered her fearful and unwilling to do a news conference during his initial space flight. As he reported in his autobiography, John Glenn: A Memoir, and as shown on-screen in The Right Stuff, her stuttering was never a problem between the two of them, he "just thought of it as something Annie did". But she grew frustrated with it, and some years later put herself through intense speech therapy and was largely successful in masking the outward symptoms of stuttering. A proud moment for the both of them was the first public speech she gave on her experiences as a stutterer.
In M. Night Shyamalan's 2006 film Lady in the Water, Paul Giamatti's character has a pronounced stutter that selectively disappears when he interacts with Bryce Dallas Howard's character.
The book (and film) One Flew Over the Cuckoo's Nest has a major character named Billy Bibbit who suffers from a pronounced stutter. Through the story it is revealed that it has very negatively impacted his self-esteem (even leading to a suicide attempt when he stuttered through a marriage proposal and the woman laughed at him). The stutter abruptly disappears after he has sex with a prostitute that another patient smuggles on the ward.
An episode of the hit TV Show M*A*S*H involved a stuttering soldier who was convinced he was unintelligent and constantly harassed by his fellow soldiers. The usually pompous Maj. Winchester (David Ogden Stiers) takes it upon himself to prove the soldier is just as intelligent (if not more, since Winchester discovers the young man has a very high IQ) as the rest of his unit, even giving him a treasured copy of Moby-Dick to read. At the end of the episode, Winchester retires to his tent and listens happily to a tape-recorded letter from his sister, who is revealed to have a pronounced stutter. Also, Ronnie Barker's character in Open All Hours has a stutter, which sometimes gets him into trouble. His nephew mocks him for it.
- See also: Songs with stuttering
"K-K-K-Katy" was published in 1918 by Geoffrey O'Hara and became a huge hit in wartime America, referred to as "The Sensational Stammering Song Success Sung by the Soldiers and Sailors". Anyone who had either a stutter or a lisp was covered. The song uses stuttered lyrics in every line of the chorus, and refers to the stuttering of a stereotypically bashful suitor.
A stylized form of stuttering has frequently appeared in popular music over the past few decades. Buddy Holly was a notable user of this technique in many of his songs, as well as supplementing the stutters with other verbal 'tics' and 'hiccups'. In some songs from the 1960s and 1970s the vocalist would rapidly repeat the first syllable of a word. An early example is The Who's 1965 song "My Generation", in which Roger Daltrey sings the line "Just talkin' 'bout my G-g-g-generation". In that particular case, the song's stuttering style provides a framework leading up to the sly lyric, "Why don't you just ff-ff-fffffffffade away!"
Another example was the affected stuttering by Canada's Bachman-Turner Overdrive in their 1974 hit song "You Ain't Seen Nothing Yet". The stutter was not intended to be part of the final release, it was originally done as a joke about Randy Bachman's brother George, who stuttered.
By the early 1980s producers were creating the same effect synthetically using tape editing and sampling of lyrics. Paul Hardcastle's 1985 song "19" features it throughout in both the spoken word and vocal segments. Remixes of songs very frequently employed the effect. Starting in the 1990s stuttering effects fell out of popular use in music.
In 1995, stutterer Scatman John turned his problem into his asset and wrote the hit song "Scatman". Stuttering assisted him to scat sing and create incredible sounds. The lyrics are inspirational and directed at stutterers:
- Everybody stutters one way or the other so check out my message to you
- As a matter of fact, don't let nothin' hold you back
- If the Scatman can do it, so can you.
In 2001, "Stutter" by American R&B singer Joe featuring Mystikal, held the number-one spot for four weeks on the Billboard Hot 100.
Placebo used a stammering man's voice on their song "Swallow" featured on their 1996 debut album, Placebo.
The song For You I Will (Confidence) by American pop singer Teddy Geiger features the line "forgive me if i stutter from all of the clutter in my head"
Lead singer of hit rock/punk band, Kele Okereke, has a very pronounced stutter when speaking, but not identifiable whilst singing.
Though a stutterer might seem to be an unlikely radio star, Howard Stern hired a mild stutterer sight unseen ("He stutters? Hire him.") to conduct celebrity interviews. Known on the Stern show as Stuttering John, John Melendez worked for Stern for 15 years before taking a position as the announcer on The Tonight Show. Howard Stern also has a collection of frequent guests, many of whom have speech impediments of some type; while their afflictions are exploited for comedic purposes, members of The Wack Pack are well-loved by Howard Stern and his fans.
In addition to personal feelings of shame or anxiety, outside discrimination is still a significant problem for stutterers. The vast majority of stutterers experience or have experienced bullying, harassment, or ridicule to some degree during their school years from both peers and teachers who do not understand the condition.It can be especially difficult for stutterers to form friendships or romantic relationships, both because stutterers may avoid social exposure and because non-stutterers may find the disorder unattractive. The stigma of stuttering carries over into the workplace, often resulting in severe employment discrimination against stutterers. Consequently, stuttering has been legally classified as a disability in many parts of the world, affording stutterers the same protection from wrongful discrimination as for people with other disabilities. The UK Disability Discrimination Act 1995 and the Americans with Disabilities Act of 1990 both expressly protect stutterers from wrongful dismissal or discrimination.Along with disability legislation, many stutterer rights groups have formed to address these issues. One interesting example is the Turkish Association of Disabled Persons, which successfully appealed to the major Turkish telephone company Telsim, resulting in reduced rates for people with stutters or other speech disabilities because of the additional time it takes them to converse on the telephone. Also, the U.S. Congress passed a resolution in May 1988 designating the second week of May as Stuttering Awareness Week, while International Stuttering Awareness Day, or ISAD, is held internationally on October 22. In September 2005, ISAD was recognised and supported by over 30 Members of the European Parliament (MEPS) at a reception given by the European League of Stuttering Associations.
Even though public awareness of stuttering has improved markedly over the years, misconceptions are still very common, usually reinforced by inaccurate media portrayals of stuttering and by various folk myths. A 2002 study focusing on college-age students and conducted by University of Minnesota Duluth found that a large majority viewed the cause of stuttering as either nervousness or low self-confidence, and many recommended simply "slowing down" as the best course of action for recovery.7 While these misconceptions are damaging and may actually worsen the symptoms of stuttering, groups and organizations are making significant progress towards a greater public awareness.
- Note 1: Starkweather, C. Woodruff (1997). Stuttering. PRO-ED. ISBN 0890796998.
- Note 2: The Stuttering Home Page. The University of Minnesota Duluth Stuttering Home Page. Retrieved on March 28, 2005.
- Note 3: Stuttering Homepage. Minnesota State University Stuttering Homepage. Retrieved on March 23, 2005.
- Note 4: Conture, Edward G. (1990). Stuttering. Prentice Hall. ISBN 0138536317.
- Note 5: - This interpretation is on the Biblical passage "Lord, open my breast, and do Thou ease for me my task, Unloose the knot upon my tongue, that they may understand my words." Traditional Hebrew midrashim (commentaries) give stuttering as the reason for Moses' reluctance to speak. He had Aaron as his public speaker.
- Note 6: Folk Myths About Stuttering. Folk Myths About Stuttering. Retrieved on April 3, 2005.
- Note 7: Public Perceptions 2002. Public Perceptions of stuttering. Retrieved on April 3, 2005.
- Note 8: Stuttering FAQ. Stuttering Foundation of America. Retrieved on April 4, 2005.
- Note 9: Susan Chollar (December, 1988). "Stuttering: the parental influence". Psychology Today.
- Note 10: Churchill: A Study in Oratory. The Churchill Centre. Retrieved on April 5, 2005.
- Note 11: Carvel, John (June 4, 1999). Stammerers targeted by school bullies. Guardian Unlimited
- Note 12: Maguire, G., Riley, G.D., Wu, J.C., Franklin, D.L., Potkin, S. "Effects of risperidone in the treatment of stuttering," in Speech Production: Motor Control, Brain Research and Fluency Disorders, edited by W. Hulstijn, H.F.M. Peters, and P.H.H.M. Van Lieshout, Amsterdam: Elsevier, 1997.
- Note 13: Olanzapine for Developmental Stuttering. Clinical Psychiatry News, Volume 30, Issue 7, (July 2002). Retrieved on June 11, 2006.
- Note 14: Pagoclone. Indeveus Pharmaceuticals. Retrieved on June 11, 2006.
- Note 15: Kalinowski, J., Armson, J., Stuart, A., Graco, V., and Roland-Mieskowski, M. "Effects of alterations in auditory feedback and speech rate on stuttering frequency," Language and Speech, 1993, 36, 1–16; Sark, S., Kalinowski, J., Stuart, A., Armson, J. "Stuttering amelioration at various auditory feedback delays and speech rates," European Journal of Disorders of Communication, 31, 259–269, 1996; Brenaut, L., Morrison, S., Kainowski, J., Armson, J., Stuart, A. "Effect of Altered Auditory Feedback on Stuttering During Telephone Use," Dalhousie University, Halifax, Nova Scotia, Canada, 1995; Stager, S., Denman, D., Ludlow, C. "Modifications in Aerodynamic Variables by Persons Who Stutter Under Fluency-Evoking Conditions." Journal of Speech, Language, and Hearing Research, 40, 832–847, August 1997. Zimmerman, S., Kalinowski, J., Stuart, A., Rastatter, M. "Effect of Altered Auditory Feedback on People Who Stutter During Scripted Telephone Conversations." Journal of Speech, Language, and Hearing Research, 40, 1130–1134, October 1997.
- Note 16: Ryan, B.P., Van Kirk, B. "The Establishment, Transfer and Maintenance of Fluent Speech in 50 Stutterers Using Delayed Auditory Feedback and Operant Procedures." Journal of Speech and Hearing Disorders, 39:1, February, 1974. Ryan, Bruce and Barbara Van Kirk Ryan. "Programmed Stuttering Treatment for Children: Comparison of Two Establishment Programs Through Transfer, Maintenance, and Follow-Up," Journal of Speech and Hearing Research, 38:1, February 1995. Radford, N., Tanguma, J., Gonzalez, M., Nericcio, M.A., Newman, D. "A Case Study of Mediated Learning, Delayed Auditory Feedback, and Motor Repatterning to Reduce Stuttering," Perceptual and Motor Skills, 2005, 101, 63–71.
- Note 17: Delayed auditory feedback in the treatment of stuttering: clients as consumers. 'International Journal of Language and Communication Disorders, 2003, Vol. 38, No. 2, 119–129.. Retrieved on June 11, 2006.
- Note 18: Stuart, A., Kalinowski, J., Rastatter, M., Saltuklaroglu, T., Dayalu, V. "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," International Journal of Language and Communication Disorders, 2004, 39:1, 93–113. Stuart, A., Kalinowski, J., Saltuklaroglu, T., Guntupalli, V. "Investigations of the impact of altered auditory feedback in-the-ear devices on the speech of people who stutter: One-year follow-up," Disability and Rehabilitation, 2006. 1–9.
- Note 19: Boberg, E., & Kully, D. (1994). "Long-term results of an intensive treatment program for adults and adolescents who stutter." Journal of Speech and Hearing Research, 37, 1050–1059.
- Note 20: Blomgren, M., Roy, N., Callister, T., Merrill, R. "Intensive Stuttering Modification Therapy: A Multidimensional Assessment of Treatment Outcomes," Journal of Speech and Hearing Research, 48:509–523, June 2005.
- Note 21: Stuttering. National Institute on Deafness and other Communication Disorders. Retrieved on June 11, 2006.
- Note 22: Stuttering. KidsHealth. Retrieved on June 11, 2006.
- Note 23: Nippold, M., Rudzinski, M. "Parents' Speech and Children's Stuttering: A Critique of the Literature," Journal of Speech and Hearing Research, 38:5, October 1995.
- Note 24: Blomgren, M., Roy, N., Callister, T., Merrill, R. "Intensive Stuttering Modification Therapy: A Multidimensional Assessment of Treatment Outcomes," Journal of Speech and Hearing Research, 48:509–523, June 2005.
- Note 25: Craig, A., et al. "A Controlled Clinical Trial for Stuttering in Persons Aged 9 to 14 Years" Journal of Speech and Hearing Research, 39:4, 808–826, August 1996. See also Hancock, et al. "Two- to Six-Year Controlled-Trial Stuttering Outcomes for Children and Adolescents," Journal of Speech and Hearing Research, 41:1242–1252, December 1998.
- Note 26: Proctor A., Duff, M.. and Yairi, E. (2002). "Early childhood stuttering: African Americans and European Americans." ASHA Leader, 4:15, p.102.
- Note 27: Craig. A, Hancock K, Tran. Y, Craig. M, & Peters, K. (2002). "Epidemiology of stuttering in the communication across the entire life span." Journal of Speech Language Hearing Research, 45:1097–1105.
- Note 28: Yairi, E, & Ambrose, N. (2005). Early childhood stuttering. Austin, TX: Pro-Ed, Inc. Kloth, S., Janssen, P., Kraaimaat, F. & Brutten, G. (1995). "Speech-motor and linguistic skills of young stutterers prior to onset." Journal of Fluency Disorders, 20, 157–170. Yairi, 2005; “On the Gender Factor in Stuttering,” Stuttering Foundation of America newsletter, Fall 2005, page 5.
- Note 29: Comings, D., et al., "Polygenic Inheritance of Tourette Syndrome, Stuttering, Attention Deficit Hyperactivity, Conduct, and Oppositional Defiant Disorder," American Journal of Medical Genetics 67:264–288 (1996).
- Note 30: Yairi, E., Ambrose, N. "Onset of stuttering in preschool children: Selected factors," Journal of Speech and Hearing Research, 35, 1992, 782–788.
- Note 31: Yairi, E. (1993) "Epidemiologic and other considerations in treatment efficacy research with preschool-age children who stutter," Journal of Fluency Disorders, 18, 197–220. Yairi, E., Ambrose, N. "Onset of stuttering in preschool children: Selected factors," Journal of Speech and Hearing Research, 35, 1992, 782–788.
- Note 32: Andrews, et al., "Stuttering: a review of research findings and theories," Journal of Speech and Hearing Disorders, 48, 226–246, 1983.
- Note 33: Yairi, E, & Ambrose, N. (2005). Early childhood stuttering. Austin, TX: Pro-Ed, Inc. Kloth, S., Janssen, P., Kraaimaat, F. & Brutten, G. (1995). "Speech-motor and linguistic skills of young stutterers prior to onset. Journal of Fluency Disorders, 20, 157–170.
- Note 34: Yairi, 2005; "On the Gender Factor in Stuttering," Stuttering Foundation of America newsletter, Fall 2005, page 5.
- Note 35: Craig, et al., 2002; Craig, A. Tran, Y., Craig, M., & Peters, K. (2002). "Epidemiology of stuttering in the communication across the entire life span." Journal of Speech, Language, and Hearing Research, 45, 1097–1105.
- Note 36: Braun, A.R., Varga, M., Stager, S., Schulz, G., Selbie, S., Maisog, J.M., Carsom, R.E., Ludlow, C.L. "Atypical Lateralization of Hemispehral Activity in Developmental Stuttering: An H215O Positron Emission Tomography Study," in Speech Production: Motor Control, Brain Research and Fluency Disorders, edited by W. Hulstijn, H.F.M. Peters, and P.H.H.M. Van Lieshout, Amsterdam: Elsevier, 1997.
- Note 37: A. L. Foundas, MD, A. M. Bollich, PhD, J. Feldman, MD, D. M. Corey, PhD, M. Hurley, PhD, L. C. Lemen, PhD and K. M. Heilman, MD. "Aberrant auditory processing and atypical planum temporale in developmental stuttering," Neurology, 2004;63:1640–1646.
- Note 38: Caruso, A., et al. "Adults Who Stutter: Responses to Cognitive Stress." Journal of Speech and Hearing Research, 37, 746–754, August 1994.
- Note 39: Perkins, W., Dabul, B. "The Effects of Stuttering on Systolic Blood Pressure." Journal of Speech & Hearing Research, Vol. 16, No. 4, December 1973.
- Note 40: Schwartz, Martin. Personal correspondence.
- Note 41: Abwender DA, Trinidad KS, et al. "Features resembling Tourette's syndrome in developmental stutterers." Brain Lang. 1998 May;62(3):455-64. PMID 9593619
- Note 42: State Special Telephone Equipment Distribution Programs. Electronic Anti-Stuttering Devices. Retrieved on February 4, 2007.
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- Compton, D. G. (1993). Stammering : its nature, history, causes and cures. Hodder & Stoughton. ISBN 0-340-56274-9.
- Conture, Edward G. (1990). Stuttering. Prentice Hall. ISBN 0-13-853631-7.
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