Stuttering

Stuttering
Classification and external resources
ICD-10 F98.5
ICD-9 307.0
OMIM 184450 609261
MeSH D013342

Stuttering, also known as stammering in the United Kingdom, is a speech disorder in which the flow of speech is disrupted by involuntary repetitions and prolongations of sounds, syllables, words or phrases, and involuntary silent pauses or blocks in which the stutterer is unable to produce sounds. 'Verbal non-fluency' is the accepted umbrella term for such speech impediments. 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 and semi-vowels. 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. The impact of stuttering on a person's functioning and emotional state can be severe. Much of this goes unnoticed by the listener, and 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 generally not a problem with the physical production of speech sounds or putting thoughts into words. Despite popular perceptions to the contrary[1], stuttering does not affect and has no bearing on intelligence. Apart from their speech impediment, people who stutter may well be 'normal' in the clinical sense of the term. Anxiety, low self-esteem, nervousness, and stress therefore do not cause stuttering per se, although they are very often the result of living with a highly stigmatized disability and, in turn, exacerbate the problem.

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 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.

Contents

Classification

Developmental stuttering is stuttering that originates when a child is learning to speak and develops as the child matures into adulthood. Other speech disorders with symptoms resembling stuttering are cluttering, Parkinson's speech, essential tremor, spasmodic dysphonia, selective mutism and social anxiety.

Characteristics

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 in 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.[2] 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.[3]

Secondary behaviors

Secondary stuttering behaviors are unrelated to speech production and are learned behaviors which become linked to the primary behaviors.

Secondary behaviors include escape behaviors, in which a stutterer attempts to terminate a moment of stuttering. Examples might be physical movements such as sudden loss of eye contact, eye-blinking, head jerks, hand tapping, interjected "starter" sounds and words, such as "um," "ah," "you know".[5][6] In many cases, these devices work at first, and are therefore reinforced, becoming a habit that is subsequently difficult to break.[6]

Secondary behaviors also refer to the use of avoidance strategies such avoiding specific words, people or situations that the person finds difficult. Some stutterers successfully use extensive avoidance of situations and words to maintain fluency and may have little or no evidence of primary stuttering behaviors. Such covert stutterers may have high levels of anxiety, and extreme fear of even the most mild disfluency.[5]

Variability

The severity of a stutter is often not constant even for severe stutterers. Stutterers 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.[7] Other situations, such as public speaking and speaking on the telephone are often greatly feared by stutterers, and increased stuttering is reported.[8]

Feelings and attitudes

Stuttering may have a significant negative cognitive and affective impact on the stutterer. In a famous analogy, Joseph Sheehan, a prominent researcher in the field, compared stuttering to an iceberg, with the overt aspects of stuttering above the waterline, and the larger mass of negative emotions invisible below the surface.[9] Feelings of embarrassment, shame, frustration, fear, anger, and guilt are frequent in stutterers,[10] and may actually increase tension and effort, leading to increased stuttering.[11] With time, continued exposure to difficult speaking experiences may crystallize into a negative self-concept and self-image. A stutterer may project his or her attitudes onto others, believing that they think he is nervous or stupid. Such negative feelings and attitudes may need to be a major focus of a treatment program.[11]

Sub-types

Developmental

Stuttering is typically a developmental disorder beginning in early childhood and continuing into adulthood in at least 20% of affected children.[12][13] The mean onset of stuttering is 30 months.[14] 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.[15] Most young children are unaware of the interruptions in their speech.[15] With early stutterers, disfluency may be episodic, and periods of stuttering are followed by periods of relative fluency.[16] Though the rate of early recovery is very high,[12] with time a young stutterer may transition from easy, relaxed repetition to more tense and effortful stuttering, including blocks and prolongations.[15] 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.[17] With time secondary stuttering including escape behaviours such 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.[18] Other, rarer, patterns of stuttering development have been described, including sudden onset with the child being unable to speak, despite attempts to do so.[19] The child usually blocks silently of 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 do not develop secondary stuttering behaviours.[20]

Acquired

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 abuse/misuse. 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 stutterers with the developmental condition, are not effective with the acquired type.[13][12][21]

Psychogenic stuttering may also arise after a traumatic experience such as a bereavement, 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.[22]

Causes of developmental stuttering

No single, exclusive cause of developmental stuttering is known. A variety of hypotheses and theories suggest multiple factors contributing to stuttering.[12] Among these is the strong evidence that stuttering has a genetic basis.[23] Children who have first-degree relatives who stutter are three times as likely to develop a stutter.[24] However, twin and adoption studies suggest that genetic factors interact with environmental factors for stuttering to occur,[25] and forty to seventy percent of stutterers have no family history of the disorder.[26] There is evidence that stuttering is more common in children who also have concomitant speech, language, learning or motor difficulties.[27]

In some stutterers, congenital factors may play a role. These may include physical trauma at or around birth, including cerebral palsy, retardation, or stressful situations, such as the birth of a sibling, moving, or a sudden growth in linguistic ability.[25][23]

There is clear empirical evidence for structural and functional differences in the brains of stutterers. 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.[28][29]

Auditory processing deficits have also been proposed as a cause of stuttering. Stuttering is less prevalent in deaf and hard of hearing individuals,[30] and stuttering may be improved when auditory feedback is altered, such as masking, delayed auditory feedback (DAF), or frequency altered feedback.[31][12] There is some evidence that the functional organization of the auditory cortex may be different in stutterers.[12]

There is evidence of differences in linguistic processing between stutterers and non-stutterers.[32] Brain scans of adult stutterers 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.[12][25]

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 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 etc. In stuttering, the severity of the disorder is seen as likely to increase when demands placed on the person's speech and language system is exceeded by their capacity to deal with these pressures.[33]

Treatment

Main article: Stuttering therapy

Fluency shaping therapy

Fluency shaping therapy, also known as "speak more fluently", "prolonged speech" or "connected speech", trains stutterers to speak fluently by controlling their breathing, phonation, and articulation (lips, jaw, and tongue). It is based on operant conditioning techniques.[34]

Stutterers 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 stutterer 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.[35]

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.[36] 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.[37]

As proposed by Van Riper, stuttering modification therapy has four overlapping stages:[38]

Electronic fluency devices

See also: Electronic fluency devices

Altered auditory feedback, so that stutterers hear their voice differently, have been used for over 50 years in the treatment of stuttering.[39] Altered auditory feedback effect can be produced by speaking in chorus with another person, by providing blocking out the stutterer's voice while talking (masking), by delaying the stutterer'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 stutterers showing substantial reductions in stuttering, while others improved only slightly or not at all.[39] 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.[40]

Anti-stuttering medications

The effectiveness of pharmacological agents, such as anti-convulsants, anti-depressants, antipsychotic and antihypertensive medications, and dopamine antagonists in the treatment of stuttering has been evaluated in studies involving both adults and children.[41] A comprehensive review of pharmacological treatments of stuttering in 2006 concluded that few of the drug trials were methodologically sound.[41] Of those that were, only one, not unflawed study,[42] showed a reduction in the frequency stuttering to less than 5% of words spoken. In addition, potentially serious side effects of pharmacological treatments were noted.[41]

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 continues 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 living can be improved by improved acceptance of self and stuttering.

Prognosis

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,[14][43] and about 74% recover by their early teens.[44] In particular, girls seem to recover well.[44][45] For others, early intervention is effective in helping the child achieve normal fluency.[46]

Once stuttering has become established, and the child has developed secondary behaviors, the prognosis is more guarded,[46] and only 18% of children who stutter after five years recover spontaneously.[47] However, with treatment young children may be left with little evidence of stuttering.[46]

With adult stutterers, there is no known cure,[44] though they may make partial recovery with intervention. Stutterers often learn to stutter less severely and be less affected emotionally, though others may make no progress with therapy.[46]

Epidemiology

The lifetime prevalence, or the proportion of individuals expected to stutter at one time in their lives, is about 5%,[48] and overall males are affected two to five times more often than females.[49][13][50] Most stuttering begins in early childhood and according studies suggest 2.5% of children under the age of 5 stutter.[51][52] The sex ratio appears to widen as children grow: among preschoolers, boys who stutter outnumber girls who stutter about two to one, or less.[52][50] but widens to three to one at first grade and five to one at fifth grade,[53] due to higher recovery rates in girls.[44] Due to high (approximately 65–75%) rates of early recovery,[49][54] the overall prevalence of stuttering is generally considered to be approximately 1%.[55][13]

Stuttering occurs in all cultures and races,[23] and at similar rates.[13] A US-based study indicated that there were no racial or ethnic differences in the incidence of stuttering in preschool children.[51][52] 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)

Lewis Carroll, the well-known author of Alice in Wonderland, was afflicted with a stammer, as were his siblings.

History and cultural aspects

See also: Cultural references to stuttering

For centuries stuttering has featured prominently 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 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, who tried to control his disfluency by speaking with pebbles in his mouth.[56] The Talmud interprets Bible passages to indicate Moses was also a stutterer, and that placing a burning coal in his mouth had caused him to be "slow and hesitant of speech" (Exodus 4, v.10)[56]

Galen's humoral theories remained influential in Europe into the Middle Ages and beyond. 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.[57] 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.[56]

In 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, cutting nerves, and 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.[56]

Notker Balbulus, from a medieval manuscript.

Italian pathologist Giovanni Morgagni attributed stuttering to deviations in the hyoid bone, a conclusion he came to via autopsy.[57] 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.

Other famous Englishmen who stammered were King George VI and Prime Minister Winston Churchill, who led the UK through World War II. George VI went through years of speech therapy for his stammer. Churchill claimed, perhaps not directly discussing himself, "Sometimes a slight and not unpleasing stammer or impediment has been of some assistance in securing the attention of the audience...".[58] 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 in her 1941 book 'I was Winston Churchill's Private Secretary' commented that 'Winston Churchill was born and grew up with a stutter'. Moir writes also 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) ‘Churchill struggled to express his feelings but his stutter caught him in the throat and his face turned purple' and ‘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.’ (More on Churchill at [1])

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.[59] 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."[59]

Jazz and Euro Dance 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. [2]

See also

Notes

  1. ↑ Myths about stuttering
  2. ↑ Ward 2006, pp. 5–6
  3. ↑ Kalinowski 2006, pp. 31–37
  4. ↑ Guitar 2005, pp. 14–15
  5. ↑ 5.0 5.1 Ward 2006, pp. 6–7
  6. ↑ 6.0 6.1 Guitar 2005, p. 16
  7. ↑ Ward 2006, pp. 13–14
  8. ↑ Ward 2006, p. 14
  9. ↑ Kalinowski 2006, p. 17
  10. ↑ Ward 2006, p. 179
  11. ↑ 11.0 11.1 Guitar 2005, pp. 16–7
  12. ↑ 12.0 12.1 12.2 12.3 12.4 12.5 12.6 Gordon, N (2002). "Stuttering: incidence and causes". Developmental medicine and child neurology 44 (4): 278–81. doi:10.1017/S0012162201002067. PMID 11995897. 
  13. ↑ 13.0 13.1 13.2 13.3 13.4 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. PMID 17429528. 
  14. ↑ 14.0 14.1 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. 
  15. ↑ 15.0 15.1 15.2 Ward 2006, p. 13
  16. ↑ Ward 2006, pp. 114–5
  17. ↑ Ward 2006, pp. 13, 115
  18. ↑ Ward 2006, pp. 115–116
  19. ↑ Ward 2006, pp. 117–119
  20. ↑ Ward 2006, pp. 117–119
  21. ↑ Ward 2006, pp. 4, 332–335
  22. ↑ Ward 2006, pp. 4, 332, 335–337
  23. ↑ 23.0 23.1 23.2 Guitar 2005, pp. 5–6
  24. ↑ Ward 2006, p. 11
  25. ↑ 25.0 25.1 25.2 Guitar 2005, p. 66
  26. ↑ Guitar 2005, p. 39
  27. ↑ Ward 2006, p. 12
  28. ↑ Kate, Watkins (2007). "Structural and functional abnormalities of the motor system in developmental stuttering.". Brain 131: 50. doi:10.1093/brain/awm241. PMID 17928317. 
  29. ↑ Soo-Eun, Chang (2007). "Brain anatomy differences in childhood stuttering.". NeuroImage. 
  30. ↑ Ward 2006, pp. 46–7
  31. ↑ Ward 2006, p. 58
  32. ↑ Ward 2006, p. 43
  33. ↑ Ward 2006, pp. 16–21
  34. ↑ Ward 2006, p. 257
  35. ↑ Ward 2006, pp. 257–67
  36. ↑ Ward 2006, p. 253
  37. ↑ Ward 2006, p. 245
  38. ↑ Ward 2006, pp. 247–53
  39. ↑ 39.0 39.1 Bothe, AK; Finn, P; Bramlett, RE (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 (inactive 2008-06-25). PMID 17329678. 
  40. ↑ 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: 321–341. doi:10.1044/1058-0360(2006/031). PMID 17102144. 
  41. ↑ 41.0 41.1 41.2 Bothe, AK; Davidow, JH; Bramlett, RE; Franic, DM; Ingham, RJ (2006). "Stuttering Treatment Research 1970-2005: II. Systematic Review Incorporating Trial Quality Assessment of Pharmacological Approaches". American Journal of Speech-Language Pathology 15: 342–352. doi:10.1044/1058-0360(2006/032). PMID 17102145. 
  42. ↑ Maguire, GA; Riley, GD; Franklin, DL; Gottschalk, LA (2000). "Risperidone for the treatment of stuttering". Journal of clinical psychopharmacology 20 (4): 479–82. doi:10.1097/00004714-200008000-00013. PMID 10917410. 
  43. ↑ Yairi, E (1993). "Epidemiologic and other considerations in treatment efficacy research with preschool-age children who stutter". Journal of Fluency Disorders 18: 197–220. doi:10.1016/0094-730X(93)90007-Q. 
  44. ↑ 44.0 44.1 44.2 44.3 Ward 2006, p. 16
  45. ↑ Yairi, E (Fall 2005). "On the Gender Factor in Stuttering". Stuttering Foundation of America newsletter: 5. 
  46. ↑ 46.0 46.1 46.2 46.3 Guitar 2005, p. 7
  47. ↑ Andrews, G; Craig, A; Feyer, AM; 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. 
  48. ↑ Mansson, H (2000). "Childhood stuttering: Incidence and development". Journal of Fluency Disorders 25 (1): 47–57. doi:10.1016/S0094-730X(99)00023-6. 
  49. ↑ 49.0 49.1 Yairi, E; Ambrose, N; Cox, N (1996). "Genetics of stuttering: a critical review". Journal of Speech Language Hearing Research 39: 771–784. 
  50. ↑ 50.0 50.1 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 (20): 157–70. doi:10.1016/0094-730X(94)00022-L. 
  51. ↑ 51.0 51.1 Proctor, A; Duff, M; Yairi, E (2002). "Early childhood stuttering: African Americans and European Americans". ASHA Leader 4 (15): 102. 
  52. ↑ 52.0 52.1 52.2 Yairi, E; Ambrose, N (2005). "Early childhood stuttering". Pro-Ed (Austin, Texas). 
  53. ↑ Guitar 2005, p. 22
  54. ↑ Yairi, E; Ambrose, NG (1999). "Early childhood stuttering I: persistency and recovery rates". J. Speech Lang. Hear. Res. 42 (5): 1097–112. PMID 10515508. 
  55. ↑ Craig, A; Hancock, K; Tran, Y; Craig, M; Peters, K (2002). "Epidemiology of stuttering in the community across the entire life span". J. Speech Lang. Hear. Res. 45 (6): 1097–105. doi:10.1044/1092-4388(2002/088 (inactive 2008-06-25). PMID 12546480. 
  56. ↑ 56.0 56.1 56.2 56.3 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. 
  57. ↑ 57.0 57.1 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. 
  58. ↑ "Churchill: A Study in Oratory". The Churchill Centre. Retrieved on 2005-04-05.
  59. ↑ 59.0 59.1 Kuster, Judith Maginnis (2005-04-01). "Folk Myths About Stuttering". Minnesota State University. Retrieved on 2005-04-03.

References

Further reading

External links