|Classification and external resources|
Stuttering (//; alalia syllabaris), also known as stammering (//; alalia literalis or anarthria literalis), is a speech disorder in which the flow of speech is disrupted by involuntary repetitions and prolongations of sounds, syllables, words or phrases as well as involuntary silent pauses or blocks in which the person who stutters is unable to produce sounds. 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 people who stutter as blocks, and the prolongation of certain sounds, usually vowels and semivowels. For many people who stutter, repetition is the primary problem. Blocks and prolongations are learned mechanisms to mask repetition, as the fear of repetitive speaking in public is often the main cause of psychological unease. The term "stuttering" covers a wide range of severity, encompassing barely perceptible impediments that are largely cosmetic to severe symptoms that effectively prevent oral communication.
The impact of stuttering on a person's functioning and emotional state can be severe. This may include fears of having to enunciate specific vowels or consonants, fears of being caught stuttering in social situations, self-imposed isolation, anxiety, stress, shame, or a feeling of "loss of control" during speech. Stuttering is sometimes popularly associated with anxiety but there is actually no such correlation (though as mentioned social anxiety may actually develop in individuals as a result of their stuttering). Stuttering is not an indicator of reduced intelligence.
Stuttering is generally not a problem with the physical production of speech sounds or putting thoughts into words. Acute nervousness and stress do not cause stuttering but they can trigger stuttering in people who have the speech disorder, and living with a highly stigmatized disability can result in anxiety and high allostatic stress load (i.e., chronic nervousness and stress) that reduce the amount of acute stress necessary to trigger stuttering in any given person who stutters, exacerbating the problem in the manner of a positive feedback system; the name 'Stuttered Speech Syndrome' has been proposed for this condition. Neither acute nor chronic stress, however, itself creates any predisposition to stuttering.
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. Although the exact etiology or cause of stuttering is unknown, both genetics and neurophysiology are thought to contribute. There are many treatments and speech therapy techniques available that may help increase fluency in some people who stutter to the point where an untrained ear cannot identify a problem; however, there is essentially no cure for the disorder at present.
Developmental stuttering is stuttering that originates when a child is learning to speak and develops as the child matures into adulthood. Other disorders with symptoms resembling stuttering include Asperger's syndrome, cluttering, Parkinson's speech, essential tremor, palilalia, spasmodic dysphonia, selective mutism, and social anxiety.
Primary behaviors 
Primary stuttering behaviors are the overt, observable signs of speech fluency breakdown, including repeating sounds, syllables, words or phrases, silent blocks and prolongation of sounds. These differ from the normal disfluencies found in all speakers in that stuttering disfluencies may last longer, occur more frequently, and are produced with more effort and strain. Stuttering disfluencies also vary in quality: normal disfluencies tend to be a repetition of words, phrases or parts of phrases, while stuttering is characterized by prolongations, blocks and part-word repetitions.
- Repetition occurs when a unit of speech, such as a sound, syllable, word, or phrase is repeated and are typical in children who are beginning to stutter. For example, "to-to-to-tomorrow".
- Prolongations are the unnatural lengthening of continuant sounds, for example,"mmmmmmmmmilk". Prolongations are also common in children beginning to stutter.
- Blocks are inappropriate cessation of sound and air, often associated with freezing of the movement of the tongue, lips and/or vocal folds. Blocks often develop later, and can be associated with muscle tension and effort.
The severity of a stutter is often not constant even for people who severely stutter. People who stutter commonly report dramatically increased fluency when talking in unison with another speaker, copying another's speech, whispering, singing, and acting or when talking to pets, young children, or themselves. Other situations, such as public speaking and speaking on the telephone are often greatly feared by people who stutter, and increased stuttering is reported.
Feelings and attitudes 
Stuttering may have a significant negative cognitive and affective impact on the person who stutters. Joseph Sheehan, a prominent researcher in the field, has described stuttering in terms of the well-known analogy to an iceberg, with the immediately visible and audible symptoms of stuttering above the waterline and a broader set of symptoms such as negative emotions hidden below the surface. Feelings of embarrassment, shame, frustration, fear, anger, and guilt are frequent in people who stutter, and may actually increase tension and effort, leading to increased stuttering. With time, continued exposure to difficult speaking experiences may crystallize into a negative self-concept and self-image. A person who stutters may project his or her attitudes onto others, believing that they think he or she is nervous or stupid. Such negative feelings and attitudes may need to be a major focus of a treatment program.
Fluency and disfluency 
Linguistic tasks can invoke speech disfluency. People who stutter may "move along a continuum from fluency to dysfluency." Tasks that trigger disfluency usually require a controlled-language processing, which involves linguistic planning. In stuttering, it is seen that many individuals have fluency when it comes to tasks that allow for automatic processing without substantial planning. For example, singing "Happy Birthday" or other relatively common, repeated linguistic discourses could be fluid in people who stutter. Tasks like this reduce semantic, syntactic, and prosodic planning, whereas spontaneous, "controlled" speech or reading aloud requires thoughts to transform into linguistic material and thereafter syntax and prosody. Some researchers hypothesize that controlled-language activated circuitry consistently does not function properly in people who stutter, whereas people who do not stutter only sometimes display disfluent speech and abnormal circuitry.
Stuttering is typically a developmental disorder beginning in early childhood and continuing into adulthood in at least 20% of affected children. The mean onset of stuttering is 30 months. Although there is variability, early stuttering behaviours usually consist of word or syllable repetitions, and secondary behaviours such as tension, avoidance or escape behaviours are absent. Most young children are unaware of the interruptions in their speech. With early people who stutter, disfluency may be episodic, and periods of stuttering are followed by periods of relative fluency.
Though the rate of early recovery is very high, with time a young person who stutters may transition from easy, relaxed repetition to more tense and effortful stuttering, including blocks and prolongations. Some propose that parental reaction may affect the development of chronic stutter. Recommendations to slow down, take a breath, say it again, etc. may increase the child’s anxiety and fear, leading to more difficulties with speaking and, in the "cycle of stuttering" to ever yet more fear, anxiety and expectation of stuttering. With time secondary stuttering including escape behaviours such as eye blinking, lip movements, etc. may be used, as well as fear and avoidance of sounds, words, people, or speaking situations. Eventually, many become fully aware of their disorder and begin to identify themselves as "stutterers". With this may come deeper frustration, embarrassment and shame. Other, rarer, patterns of stuttering development have been described, including sudden onset with the child being unable to speak, despite attempts to do so. The child usually is unable to utter the first sound of a sentence, and shows high levels of awareness and frustration. Another variety also begins suddenly with frequent word and phrase repetition, and does not develop secondary stuttering behaviours. Another way stuttering comes about is through child development. Many toddlers and preschool age children stutter as they are learning to talk, and although many parents worry about it, most of these children will outgrow the stuttering and will have normal speech as they get older. Since most of these children do not stutter as adults, this normal stage of speech development is usually referred to as pseudo-stuttering or as a normal dysfluency. As children learn to talk, they may repeat certain sounds, stumble on or mispronounce words, hesitate between words, substitute sounds for each other, and be unable to express some sounds. Children with a normal dysfluency usually have brief repetitions of certain sounds, syllables or short words; however, the stuttering usually comes and goes and is most noticeable when a child is excited, stressed or overly tired. Stuttering is also believed to be caused by neurophysiocology. Neurogenic stuttering is a type of fluency disorder in which a person has difficulty in producing speech in a normal, smooth fashion. Individuals with fluency disorders may have speech that sounds fragmented or halting, with frequent interruptions and difficulty producing words without effort or struggle. Neurogenic stuttering typically appears following some sort of injury or disease to the central nervous system. Injuries to the brain and spinal cord, including cortex, subcortex, cerebellar, and even the neural pathway regions.
Acquired stuttering 
In rare cases, stuttering may be acquired in adulthood as the result of a neurological event such as a head injury, tumour, stroke, or drug use. The stuttering has different characteristics from its developmental equivalent: it tends to be limited to part-word or sound repetitions, and is associated with a relative lack of anxiety and secondary stuttering behaviors. Techniques such as altered auditory feedback (see below), which may promote fluency in people who stutter with the developmental condition, are not effective with the acquired type.
Psychogenic stuttering may also arise after a traumatic experience such as a grief, the breakup of a relationship or as the psychological reaction to physical trauma. Its symptoms tend to be homogeneous: the stuttering is of sudden onset and associated with a significant event, it is constant and uninfluenced by different speaking situations, and there is little awareness or concern shown by the speaker.
Causes of developmental stuttering 
No single, exclusive cause of developmental stuttering is known. A variety of hypotheses and theories suggests multiple factors contributing to stuttering. Among these is the strong evidence that stuttering has a genetic basis. Children who have first-degree relatives who stutter are three times as likely to develop a stutter. However, twin and adoption studies suggest that genetic factors interact with environmental factors for stuttering to occur, and many people who stutter have no family history of the disorder. There is evidence that stuttering is more common in children who also have concomitant speech, language, learning or motor difficulties. Robert West, a pioneer of genetic studies in stuttering, has suggested that the presence of stuttering is connected to the fact that articulated speech is the last major acquisition in human evolution. Another view is that a stutter is a complex tic.
In a 2010 article, three genes were found to correlate with stuttering: GNPTAB, GNPTG, and NAGPA. Researchers estimated that alterations in these three genes were present in 9% of people who stutter who have a family history of stuttering.
For some people who stutter, congenital factors may play a role. These may include physical trauma at or around birth, as well as cerebral palsy and mental retardation. For other people who stutter, there could be added impact due to stressful situations such as the birth of a sibling, moving, or a sudden growth in linguistic ability.
There is clear empirical evidence for structural and functional differences in the brains of people who stutter. Research is complicated somewhat by the possibility that such differences could be the consequences of stuttering rather than a cause, but recent research on older children confirm structural differences thereby giving strength to the argument that at least some of the differences are not a consequence of stuttering.
Auditory processing deficits have also been proposed as a cause of stuttering. Stuttering is less prevalent in deaf and hard-of-hearing individuals, and stuttering may be improved when auditory feedback is altered, such as masking, delayed auditory feedback (DAF), or frequency altered feedback. There is some evidence that the functional organization of the auditory cortex may be different in people who stutter.
There is evidence of differences in linguistic processing between people who stutter and people who do not stutter. Brain scans of adult people who stutter have found increased activation of the right hemisphere, which is associated with emotions, than in the left hemisphere, which is associated with speech. In addition reduced activation in the left auditory cortex has been observed.
The capacities and demands model has been proposed to account for the heterogeneity of the disorder. In this approach, speech performance varies depending on the capacity that the individual has for producing fluent speech, and the demands placed upon the person by the speaking situation. Capacity for fluent speech, which may be affected by a predisposition to the disorder, auditory processing or motor speech deficits, and cognitive or affective issues. Demands may be increased by internal factors such as lack of confidence or self esteem or inadequate language skills or external factors such as peer pressure, time pressure, stressful speaking situations, insistence on perfect speech, and the like. In stuttering, the severity of the disorder is seen as likely to increase when demands placed on the person's speech and language system exceed their capacity to deal with these pressures.
Neuroimaging of developmental stuttering in adults 
Several neuroimaging studies have emerged in order to identify areas associated with stuttering. Brain imaging studies have primarily been focused on adults. In general, during stuttering, cerebral activities change dramatically in comparison to silent rest or fluent speech between people who stutter and people who do not stutter.
Studies utilizing positron emission tomography (PET) have found during tasks that invoke disfluent speech, people who stutter show hypoactivity in cortical areas associated with language processing, such as Broca's area, but hyperactivity in areas associated with motor function. One such study that evaluated the stutter period found that there was over activation in the cerebrum and cerebellum, and relative deactivation of the left hemisphere auditory areas and frontal temporal regions.
In non-stuttering, normal speech, PET scans show that both hemispheres are active but that the left hemisphere may be more active. By contrast, people who stutter yield more activity on the right hemisphere, suggesting that it might be interfering with left-hemisphere speech production. Another comparison of scans anterior forebrain regions are disproportionately active in stuttering subjects, while post-rolandic regions are relatively inactive.
Functional magnetic resonance imaging (fMRI) has found abnormal activation in the right frontal operculum (RFO), which is an area associated with time-estimation tasks, occasionally incorporated in complex speech.
Researchers have explored temporal cortical activations by utilizing magnetoencephalography (MEG). In single-word-recognition tasks, people who do not stutter showed cortical activation first in occipital areas, then in left inferior-frontal regions such as Broca’s area, and finally, in motor and premotor cortices. The people who stutter also first had cortical activation in the occipital areas, but, interestingly, the left inferior-frontal regions were activated only after the motor and premotor cortices were activated.
It is important to note that the neurological abnormalities found in adults does not conclude if childhood stuttering caused these abnormalities or if the abnormalities cause stuttering. Future research should address a longitudinal case study to track the development of brain structure in relation to stuttering.
Physiopathology of developmental stuttering 
Much evidence from neuroimaging techniques has supported the theory that the right-hemisphere of people who stutter interferes with left-hemisphere speech production. Additionally, people who stutter seem to activate motor programs before the articulatory or linguistic processing is initiated.
Overactivity and underactivity 
During speech production, people who stutter show overactivity in the anterior insula, cerebellum and bilateral midbrain. They show underactivity in the ventral premotor, Rolandic opercular and sensorimotor cortex bilaterally and Heschl’s gyrus in the left hemisphere. Additionally, speech production in people who stutter yields underactivity in cortical motor and premotor areas.
Anatomical differences 
Though neuroimaging studies have not yet found specific cortical correlates, there is much evidence that there are differences in the brain physiology of adults who stutter in comparison to those who do not.
Asymmetry has been found between the left and right planum temporale in comparing people who stutter and people who do not stutter. These studies have also found that there are anatomical differences in the Rolandic operculum and arcuate fasciculus.
Dopamine abnormalities 
Recent studies have found that adults who stutter have elevated levels of the neurotransmitter dopamine, and have thus found dopamine antagonists that reduce stuttering (see anti-stuttering medication below). Overactivity of the midbrain has been found at the level of the substantia nigra extended to the red nucleus and subthalamic nucleus, which all contribute to the production of dopamine.
Fluency shaping therapy 
Fluency shaping therapy, also known as "speak more fluently", "prolonged speech", or "connected speech", trains people who stutter to speak fluently by controlling their breathing, phonation, and articulation (lips, jaw, and tongue). It is based on operant conditioning techniques.
People who stutter are trained to reduce their speaking rate by stretching vowels and consonants, and using other fluency techniques such as continuous airflow and soft speech contacts. The result is very slow, monotonic, but fluent speech, used only in the speech clinic. After the person who stutters masters these fluency skills, the speaking rate and intonation are increased gradually. This more normal-sounding, fluent speech is then transferred to daily life outside the speech clinic, though lack of speech naturalness at the end of treatment remains a frequent criticism. Fluency shaping approaches are often taught in intensive group therapy programs, which may take two to three weeks to complete, but more recently the Camperdown program, using a much shorter schedule, has been shown to be effective.
Stuttering modification therapy 
The goal of stuttering modification therapy is not to eliminate stuttering but to modify it so that stuttering is easier and less effortful. The rationale is that since fear and anxiety causes increased stuttering, using easier stuttering and with less fear and avoidance, stuttering will decrease. The most widely known approach was published by Charles Van Riper in 1973 and is also known as block modification therapy. However, depending on the patient, speech therapy may be ineffective.
Electronic fluency device 
Altered auditory feedback, so that people who stutter hear their voice differently, has been used for over 50 years in the treatment of stuttering. Altered auditory feedback effect can be produced by speaking in chorus with another person, by blocking out the person who stutter's voice while talking (masking), by delaying the person who stutter's voice slightly (delayed auditory feedback) and/or by altering the frequency of the feedback (frequency altered feedback). Studies of these techniques have had mixed results, with some people who stutter showing substantial reductions in stuttering, while others improved only slightly or not at all. In a 2006 review of the efficacy of stuttering treatments, none of the studies on altered auditory feedback met the criteria for experimental quality, such as the presence of control groups.
Anti-stuttering medications 
The effectiveness of pharmacological agents, such as benzodiazepines, anticonvulsants, antidepressants, antipsychotic and antihypertensive medications, and dopamine antagonists in the treatment of stuttering has been evaluated in studies involving both adults and children. A comprehensive review of pharmacological treatments of stuttering in 2006 concluded that few of the drug trials were methodologically sound. Of those that were, only one, not unflawed study, showed a reduction in the frequency of stuttering to less than 5% of words spoken. In addition, potentially serious side effects of pharmacological treatments were noted, such as weight gain and the potential for blood pressure increases. There is one new drug studied especially for stuttering named pagoclone, which was found to be well-tolerated "with only minor side-effects of headache and fatigue reported in a minority of those treated".
Support groups and the self-help movement 
With existing behavioral, prosthetic, and pharmaceutical treatments providing limited relief from the overt symptoms of stuttering, support groups and the self-help movement continue to gain popularity and support by professionals and people who stutter. One of the basic tenets behind the self-help movement is that since a cure does not exist, quality of life can be improved by not thinking about the stammer for prolonged periods. Psychoanalysis has claimed success in the treatment of stuttering. Hypnotherapy has also been explored as a management alternative. Support groups further focus on the fact that stuttering is not a physical impediment but a psychological one.
Diaphragmatic breathing 
Several treatment initiatives advocate diaphragmatic breathing (or costal breathing) as a means by which stuttering can be controlled. Performing vocal artists[clarification needed], who have strengthened their diaphragm, tend to stutter when speaking but not when singing because singing involves voluntary diaphragm usage while speaking involves involuntary diaphragm usage primarily.
Among preschoolers, the prognosis for recovery is good. Based on research, about 65% of preschoolers who stutter recover spontaneously in the first two years of stuttering, and about 74% recover by their early teens. In particular, girls seem to recover well. For others, early intervention is effective in helping the child achieve normal fluency.
Once stuttering has become established, and the child has developed secondary behaviors, the prognosis is more guarded, and only 18% of children who stutter after five years recover spontaneously. However, with treatment young children may be left with little evidence of stuttering.
With adult people who stutter, there is no known cure, though they may make partial recovery or even complete recovery with intervention. People who stutter often learn to stutter less severely and be less affected emotionally, though others may make no progress with therapy.
The lifetime prevalence, or the proportion of individuals expected to stutter at one time in their lives, is about 5%, and overall males are affected two to five times more often than females. Most stuttering begins in early childhood, and studies suggest that 2.5% of children under the age of 5 stutter. The sex ratio appears to widen as children grow: among preschoolers, boys who stutter outnumber girls who stutter about two to one, or less. but widens to three to one at first grade and five to one at fifth grade, due to higher recovery rates in girls. Due to high (approximately 65–75%) rates of early recovery, the overall prevalence of stuttering is generally considered to be approximately 1%.
Cross-cultural studies of the stuttering prevalence were very active in early and middle of the 20th century, particularly under the influence of the works of Wendell Johnson, who claimed that the onset of stuttering was connected to the cultural expectations and the pressure put on young children by anxious parents. Johnson claimed there were cultures where stuttering, and even the word "stutterer", were absent (for example, among some tribes of American Indians). Later studies found that this claim was not supported by the facts, so the influence of cultural factors in stuttering research declined. It is generally accepted by contemporary scholars that stuttering is present in every culture and in every race, although the attitude towards the actual prevalence differs. Some believe stuttering occurs in all cultures and races at similar rates, about 1% of general population (and is about 5% among young children) all around the world. A US-based study indicated that there were no racial or ethnic differences in the incidence of stuttering in preschool children. At the same time, there are cross-cultural studies indicating that the difference between cultures may exist. For example, summarizing prevalence studies, E. Cooper and C. Cooper conclude: "On the basis of the data currently available, it appears the prevalence of fluency disorders varies among the cultures of the world, with some indications that the prevalence of fluency disorders labeled as stuttering is higher among black populations than white or Asian populations" (Cooper & Cooper, 1993:197).
Different regions of the world are researched very unevenly. The largest number of studies had been conducted in European countries and in North America, where the experts agree on the mean estimate to be about 1% of the general population (Bloodtein, 1995. A Handbook on Stuttering). African populations, particularly from West Africa, might have the highest stuttering prevalence in the world—reaching in some populations 5%, 6% and even over 9%. Many regions of the world are not researched sufficiently, and for some major regions there are no prevalence studies at all (for example, in China). Some claim the reason for this might be a lower incidence in general population in China.
Because of the unusual-sounding speech that is produced and the behaviors and attitudes that accompany a stutter, it has long been a subject of scientific interest and speculation as well as discrimination and ridicule. People who stutter can be traced back centuries to the likes of Demosthenes, who tried to control his disfluency by speaking with pebbles in his mouth. The Talmud interprets Bible passages to indicate Moses was also a person who stuttered, and that placing a burning coal in his mouth had caused him to be "slow and hesitant of speech" (Exodus 4, v.10)
Galen's humoral theories were influential in Europe in the Middle Ages for centuries afterward. In this theory, stuttering was attributed to imbalances of the four bodily humors—yellow bile, blood, black bile, and phlegm. Hieronymus Mercurialis, writing in the sixteenth century, proposed methods to redress the imbalance including changes in diet, reduced lovemaking (in men only), and purging. Believing that fear aggravated stuttering, he suggested techniques to overcome this. Humoral manipulation continued to be a dominant treatment for stuttering until the eighteenth century. 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.
In and around eighteenth and nineteenth century Europe, surgical interventions for stuttering were recommended, including cutting the tongue with scissors, removing a triangular wedge from the posterior tongue, and cutting nerves, or neck and lip muscles. Others recommended shortening the uvula or removing the tonsils. All were abandoned due to the high danger of bleeding to death and their failure to stop stuttering. Less drastically, Jean Marc Gaspard Itard placed a small forked golden plate under the tongue in order to support "weak" muscles.
Italian pathologist Giovanni Morgagni attributed stuttering to deviations in the hyoid bone, a conclusion he came to via autopsy. 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.
George VI went through years of speech therapy, most successfully under Australian speech therapist Lionel Logue, for his stammer. This is dealt with in the Academy Award-winning film The King's Speech (2010) in which Colin Firth plays George VI. The film is based on an original screenplay by David Seidler who also used to stutter as a child until age 16.
Churchill claimed, perhaps not directly discussing himself, that "[s]ometimes a slight and not unpleasing stammer or impediment has been of some assistance in securing the attention of the audience..." However, those who knew Churchill and commented on his stutter believed that it was or had been a significant problem for him. His secretary Phyllis Moir commented that "Winston Churchill was born and grew up with a stutter" in her 1941 book I was Winston Churchill's Private Secretary. She also noted that about one incident 'It’s s s simply s s splendid" he stuttered, as he always did when excited.’ Louis J. Alber, who helped to arrange a lecture tour of the United States wrote in Volume 55 of The American Mercury (1942) that "Churchill struggled to express his feelings but his stutter caught him in the throat and his face turned purple" and that "born with a stutter and a lisp, both caused in large measure by a defect in his palate, Churchill was at first seriously hampered in his public speaking. It is characteristic of the man’s perseverance that, despite his staggering handicap, he made himself one of the greatest orators of our time."
For centuries "cures" such as 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 used. Similarly, in the past people have subscribed to theories about the causes of stuttering which today are considered 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."
Popular culture 
Jazz and Eurodance musician Scatman John wrote the song "Scatman (Ski Ba Bop Ba Dop Bop)" to help children who stutter overcome adversity. Born John Paul Larkin, Scatman spoke with a stutter himself and won the American Speech-Language-Hearing Association's Annie Glenn Award for outstanding service to the stuttering community.
Fiction character Albert Arkwright from British sitcom Open All Hours, stammered and much of the series' humour revolved around this. Recurring character Reginald Barclay from the Star Trek television franchise and the Emperor Claudius from the I, Claudius series by Robert Graves and acted by Derek Jacobi are portrayed as suffering from and overcoming their stuttering.
Cartoon character Porky Pig has a notable stutter. This arose because his original voice artist, Joe Dougherty, had an authentic stammer. However, Dougherty's stutter caused recording sessions to take longer than otherwise necessary, and so Warner Bros. replaced him with Mel Blanc, who provided Porky's voice for the rest of his life. Porky's stutter is probably most pronounced when he says "Th-th-th-that's all, folks!" Also a person who stutters is the cartoon character Keswick from T.U.F.F. Puppy.
See also 
- American Institute for Stuttering
- Basal ganglia
- British Stammering Association
- European League of Stuttering Associations
- Israel Stuttering Association
- List of stutterers
- Malcolm Fraser (philanthropist)
- Michael Palin Centre for Stammering Children
- National Stuttering Association, United States
- Speech processing
- Stuttering Foundation of America
- The Indian Stammering Association
- The King's Speech
- Monster Study
- World Health Organization ICD-10 F95.8 - Stuttering.
- Myths about stuttering, on Stuttering Foundation's website.
- Irwin, M (2006). Au-Yeung, J; Leahy, MM, eds. Terminology – How Should Stuttering be Defined? and Why? Research, Treatment, and Self-Help in Fluency Disorders: New Horizons. The International Fluency Association. pp. 41–45. ISBN 978-0-9555700-1-8.
- Ashurst, JV; Wasson, MN (October 2011). "Developmental and persistent developmental stuttering: an overview for primary care physicians.". The Journal of the American Osteopathic Association 111 (10): 576–580. PMID 22065298.
- Ward 2006, pp. 5–6
- Kalinowski 2006, pp. 31–37
- Guitar 2005, pp. 14–15
- Ward 2006, pp. 13–14
- Ward 2006, p. 14
- Kalinowski 2006, p. 17
- Ward 2006, p. 179
- Guitar 2005, pp. 16–7
- Pollack, Andrew. "To Fight Stuttering, Doctors Look at the Brain", New York Times, September 12, 2006.
- Sandak, R. "Stuttering: a view from neuroimaging". Lancet. 2000.
- Gordon, N. (2002). "Stuttering: incidence and causes". Developmental medicine and child neurology 44 (4): 278–81. doi:10.1017/S0012162201002067. PMID 11995897.
- Craig, A.; Tran, Y. (2005). "The epidemiology of stuttering: The need for reliable estimates of prevalence and anxiety levels over the lifespan". Advances in Speech–Language Pathology 7 (1): 41–46. doi:10.1080/14417040500055060.
- Yairi, E.; Ambrose, N. (1992). "Onset of stuttering in preschool children: selected factors". Journal of speech and hearing research 35 (4): 782–8. PMID 1405533.
- Ward 2006, p. 13
- Ward 2006, pp. 114–5
- Ward 2006, pp. 13, 115
- Ward 2006, pp. 115–116
- Ward 2006, pp. 117–119
- Ward 2006, pp. 4, 332–335
- Ward 2006, pp. 4, 332, 335–337
- Guitar 2005, pp. 5–6
- Ward 2006, p. 11
- Guitar 2005, p. 66
- Guitar 2005, p. 39
- Ward 2006, p. 12
- West, R.; Nelson. S, Berry, M. (1939). "The heredity of stuttering". Quarterly Journal of Speech 25 (25): 23–30. doi:10.1080/00335633909380434.
- Sixth Oxford Dysfluency Conference
- "Genetic Mutations Linked to Stuttering". Children.webmd.com. 2010-02-10. Retrieved 2012-08-13.
- Kate, Watkins; Smith, SM; Davis, S; Howell, P (2007). "Structural and functional abnormalities of the motor system in developmental stuttering". Brain 131 (Pt 1): 50–9. doi:10.1093/brain/awm241. PMC 2492392. PMID 17928317.
- Soo-Eun, Chang (2007). "Brain anatomy differences in childhood stuttering". NeuroImage.
- Ward 2006, pp. 46–7
- Ward 2006, p. 58
- Ward 2006, p. 43
- Ward 2006, pp. 16–21
- Bloodstein, Oliver. "Handbook on Stuttering". p.142. 2007.
- Braun. "Altered patterns of cerebral activity during speech and language production in developmental stuttering. An H2(15)O positron emission tomography study.".
- Watkins, Katie. "Structural and functional abnormalities of the motor system in developmental stuttering.".
- Ward 2006, p. 257
- Ward 2006, pp. 257–67
- Ward 2006, p. 253
- Ward 2006, p. 245
- Stuttering, Stammering
- Bothe, A. K.; Finn, P.; Bramlett, R. E. (2007). "Pseudoscience and the SpeechEasy: Reply to Kalinowski, Saltuklaroglu, Stuart, and Guntupalli (2007)". American Journal of Speech-Language Pathology 16: 77–83. doi:10.1044/1058-0360(2007/010). PMID 17329678.
- Bothe, AK; Davidow, JH; Bramlett, RE; Ingham, RJ (2006). "Stuttering Treatment Research 1970-2005: I. Systematic Review Incorporating Trial Quality Assessment of Behavioral, Cognitive, and Related Approaches". American Journal of Speech-Language Pathology 15 (4): 321–341. doi:10.1044/1058-0360(2006/031). PMID 17102144.
- Bothe, A. K.; Davidow, J. H.; Bramlett, R. E.; Franic, D. M.; Ingham, R. J. (2006). "Stuttering Treatment Research 1970-2005: II. Systematic Review Incorporating Trial Quality Assessment of Pharmacological Approaches". American Journal of Speech-Language Pathology 15 (4): 342–352. doi:10.1044/1058-0360(2006/032). PMID 17102145.
- Maguire, G. A.; Riley, G. D.; Franklin, D. L.; Gottschalk, L. A. (2000). "Risperidone for the treatment of stuttering". Journal of Clinical Psychopharmacology 20 (4): 479–82. doi:10.1097/00004714-200008000-00013. PMID 10917410.
- New drugs for stuttering may be on the horizon (Stuttering Foundation's summer 2007 newsletter. Maguire, Gerald A., University of California, Irvine School of Medicine).
- Messer, Stanley B. (June 1983). "Integrating psychoanalytic and behaviour therapy: Limitations, possibilities and trade-offs". British Journal of Clinical Psychology 22 (2): 131–132.
- McCord, Hallack (1955). "Hypnotherapy and stuttering". Journal of Clinical and Experimental Hypnosis 3 (4): 210–214.
- Oakley, D.; Moss, G. (Spring 1996). "Stuttering modification using hypnosis: A case study". Speaking Out. British Stammering Association.
- Moore, Wilbur E. (June 1946). "Hypnosis in a system of therapy for stutterers". Journal of Speech and Hearing Disorders 11: 117–122.
- Fisher, Martin N. (Winter 1970). "Stuttering: A psychoanalytic view". Journal of Contemporary Psychotherapy 2 (2). pp. 124–127. Retrieved 13 August 2012.
-  British Stammering Association page on costal breathing.
-  American Institute for Stuttering
- Yairi, E. (1993). "Epidemiologic and other considerations in treatment efficacy research with preschool-age children who stutter". Journal of Fluency Disorders 18 (2–3): 197–220. doi:10.1016/0094-730X(93)90007-Q.
- Ward 2006, p. 16
- Yairi, E (Fall 2005). "On the Gender Factor in Stuttering". Stuttering Foundation of America newsletter: 5.
- Guitar 2005, p. 7
- Andrews, G; Craig, A.; Feyer, A. M.; Hoddinott, S.; Howie, P.; Neilson, M. (1983). "Stuttering: a review of research findings and theories circa 1982". The Journal of speech and hearing disorders 48 (3): 226–46. PMID 6353066.
- Mansson, H. (2000). "Childhood stuttering: Incidence and development". Journal of Fluency Disorders 25 (1): 47–57. doi:10.1016/S0094-730X(99)00023-6.
- Yairi, E; Ambrose, N; Cox, N (1996). "Genetics of stuttering: a critical review". Journal of Speech Language Hearing Research 39: 771–784.
- Kloth, S; Janssen, P; Kraaimaat, F; Brutten, G (1995). "Speech-motor and linguistic skills of young people who stutter prior to onset". Journal of Fluency Disorders 20 (20): 157–70. doi:10.1016/0094-730X(94)00022-L.
- Proctor, A.; Duff, M.; Yairi, E. (2002). "Early childhood stuttering: African Americans and European Americans". ASHA Leader 4 (15): 102.
- Yairi, E.; Ambrose, N. (2005). "Early childhood stuttering". Pro-Ed (Austin, Texas).
- Guitar 2005, p. 22
- Yairi, E.; Ambrose, N. G. (1999). "Early childhood stuttering I: persistency and recovery rates". Journal of Speech, Language, and Hearing Research 42 (5): 1097–112. PMID 10515508.
- Craig, A.; Hancock, K.; Tran, Y.; Craig, M.; Peters, K. (2002). "Epidemiology of stuttering in the community across the entire life span". Journal of Speech, Language, and Hearing Research 45 (6): 1097–105. doi:10.1044/1092-4388(2002/088). PMID 12546480.
- Nwokah, E (1988). "The imbalance of stuttering behavior in bilingual speakers". Journal of Fluency Disorders 13 (5): 357–373. doi:10.1016/0094-730X(88)90004-6.
- Sheree Reese, Joseph Jordania (2001). "Stuttering in the Chinese population in some Southeast Asian countries: A preliminary investigation on attitude and incidence". "Stuttering Awareness Day"; Minnesota State University, Mankato,.
- Brosch, S; Pirsig, W. (2001). "Stuttering in history and culture". Int. J. Pediatr. Otorhinolaryngol. 59 (2): 81–7. doi:10.1016/S0165-5876(01)00474-8. PMID 11378182.
- Rieber, RW; Wollock, J (1977). "The historical roots of the theory and therapy of stuttering". Journal of communication disorders 10 (1–2): 3–24. doi:10.1016/0021-9924(77)90009-0. PMID 325028.
- David Seidler (20 December 2010). "How the 'naughty word' cured the King's stutter (and mine)". Daily Mail.
- "Churchill: A Study in Oratory". The Churchill Centre. Retrieved 2005-04-05.
- Kuster, Judith Maginnis (2005-04-01). "Folk Myths About Stuttering". Minnesota State University. Retrieved 2005-04-03.
- Awards and Recognition. Retrieved 2009-12-10.
- Guitar, Barry (2005). Stuttering: An Integrated Approach to Its Nature and Treatment. San Diego: Lippincott Williams & Wilkins. ISBN 0-7817-3920-9.
- Kalinowski, JS; Saltuklaroglu, T (2006). Stuttering. San Diego: Plural Publishing. ISBN 978-1-59756-011-5.
- Ward, David (2006). Stuttering and Cluttering: Frameworks for understanding treatment. Hove and New York City: Psychology Press. ISBN 978-1-84169-334-7.
Further reading 
- Alm, Per A (2004). "Stuttering and the basal ganglia circuits: a critical review of possible relations" (PDF). Journal of communication disorders 37 (4): 325–69. doi:10.1016/j.jcomdis.2004.03.001. PMID 15159193.
- Alm, Per A. (2005). On the Causal Mechanisms of Stuttering. Doctoral dissertation, Dept. of Clinical Neuroscience, Lund University, Sweden.
- Compton DG (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.
- Fraser, Jane (2005). If Your Child Stutters: A Guide for Parents. Stuttering Foundation of America. ISBN 0-933388-44-6.
- Mondlin, M., How My Stuttering Ended [Case Study, Judith M. Kuster, Minnesota State University, Mankato] http://www.mnsu.edu/comdis/kuster/casestudy/path/mondlin.html
- Rockey, D., Speech Disorder in Nineteenth Century Britain: The History of Stuttering, Croom Helm, (London), 1980. ISBN 0-85664-809-4
- Goldmark, Daniel. "Stuttering in American Popular Song, 1890-1930." In Lerner, Neil (2006). Sounding Off: Theorizing Disability in Music. New York, London: Routledge. pp. 91–105. ISBN 0-415-97906-4.
|Look up stammering or stuttering in Wiktionary, the free dictionary.|
- A journey of Stuttering boy to public figure
- Stuttering at the Open Directory Project
- Stuttering at the Open Directory Project (Organizations)