stuttering stuttering stuttering, also known as stammering, 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 or semivowels. according to watkins et al., stuttering is a disorder of "selection, initiation, and execution of motor sequences necessary for fluent speech production". for many people who stutter, repetition is the main concern. the term "stuttering" covers a wide range of severity, from barely perceptible impediments that are largely cosmetic to severe symptoms that effectively prevent oral communication. almost 70 million people worldwide stutter, about 1% of the world's population. stutteringother namesstammering, alalia syllabaris, alalia literalis, anarthria literalis, dysphemia.specialtyspeech–language pathologysymptomsinvoluntary sound repetition and disruption or blocking of speechcomplicationsshame, bullying, social anxiety, fear of public speakingusual onset2–5 yearsdurationlong termcausesunknowndifferential diagnosisdysphoniatreatmentspeech therapymedicationdopamine antagonistsprognosisusually resolves by late childhood; 20% of cases last into adulthoodfrequencyabout 1% 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, low self-esteem, being a possible target of bullying (especially in children), having to use word substitution and rearrange words in a sentence to hide stuttering, or a feeling of "loss of control" during speech. stuttering is sometimes popularly seen as a symptom of anxiety, but there is no direct correlation in that direction. stuttering is generally not a problem with the physical production of speech sounds or putting thoughts into words. acute nervousness and stress are not thought to cause stuttering, but they can trigger stuttering in people who have the speech disorder, and living with a stigmatized disability can result in anxiety and high allostatic stress load (chronic nervousness and stress) that increase the amount of acute stress necessary to trigger stuttering in any given person who stutters, worsening the situation 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 or in a large group, the stuttering might be more severe or less, depending on whether or not the person who stutters is self-conscious about their stuttering. people who stutter often find that their stuttering fluctuates and that they have "good" days, "bad" days and "stutter-free" days. the times in which their stuttering fluctuates can be random. 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 decrease speech disfluency 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. the severity of the person's stuttering would correspond to the amount of speech therapy needed to decrease disfluency. for severe stuttering, long-term therapy and hard work is required to decrease disfluency. characteristics common behaviors common stuttering behaviors are observable signs of speech disfluencies, for example: 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: common disfluencies tend to be repeated movements, fixed postures, or superfluous behaviors. each of these three categories is composed of subgroups of stutters and disfluencies. repeated movements syllable repetition—a single syllable word is repeated (for example: on—on—on a chair) or a part of a word which is still a full syllable such as "un—un—under the ..." and "o—o—open". incomplete syllable repetition—an incomplete syllable is repeated, such as a consonant without a vowel, for example, "c—c—c—cold". multi-syllable repetition—more than one syllable such as a whole word, or more than one word is repeated, such as "i know—i know—i know a lot of information." fixed postures with audible airflow—prolongation of a sound occurs such as "mmmmmmmmmom". without audible airflow—such as a block of speech or a tense pause where nothing is said despite efforts. superfluous behaviors verbal—this includes an interjection such as an unnecessary uh or um as well as revisions, such as going back and correcting one's initial statements such as "i—my girlfriend ...", where the i has been corrected to the word my. nonverbal—these are visible or audible speech behaviors, such as lip smacking, throat clearing, head thrusting, etc., usually representing an effort to break through or circumvent a block or stuttering loop. variability the severity of a stutter is often not constant even for people who severely stutter. 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. other situations, such as public speaking and speaking on the telephone, are often greatly feared, and increased stuttering is reported. feelings and attitudes stuttering could have a significant negative cognitive and affective impact on the person who stutters. it has been described in terms of the 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. many perceive stutterers as less intelligent due to their disfluency; however, as a group, individuals who stutter tend to be of above average intelligence. people who stutter may project their attitudes onto others, believing that the others think them nervous or stupid. such negative feelings and attitudes may need to be a major focus of a treatment program. many people who stutter report a high emotional cost, including jobs or promotions not received, as well as relationships broken or not pursued. fluency and disfluency linguistic tasks can invoke speech disfluency. people who stutter may experience varying disfluency. tasks that trigger disfluency usually require a controlled-language processing, which involves linguistic planning. in stuttering, it is seen that many individuals do not demonstrate disfluencies 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. associated conditions stuttering can co-occur with other learning disorders. these associated disabilities include: attention deficit hyperactivity disorder (adhd): a disorder characterized by problems sustaining attention, hyperactivity, or acting impulsively. the prevalence of adhd in school-aged children who stutter is around 4-50%. dyslexia: a disorder involving difficulties with reading and spelling. the prevalence rate of childhood stuttering in dyslexia is around 30-40%, while in adults the prevalence of dyslexia in adults who stutter is around 30-50%. autism spectrum disorder intellectual disability language or learning disability seizure disorders social anxiety disorder speech sound disorders other developmental disorders causes no single, exclusive cause of developmental stuttering is known. a variety of hypotheses and theories suggest 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 stutterers have no family history of the disorder. there is evidence that stuttering is more common in children who also have concurrent 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 or stammer is a complex tic. this view is held for the following reasons. it always arises from repetition of sounds or words. young children like repetition and the more tense they are feeling, the more they like this outlet for their tension – an understandable and quite normal reaction. they are capable of repeating all types of behaviour. the more tension that is felt, the less one likes change. the more change, the greater can be the repetition. so, when a three-year-old finds he has a new baby brother or sister he may start repeating sounds. the repetitions can become conditioned and automatic and ensuing struggles against the repetitions result in prolongations and blocks in his speech. more boys stammer than girls, in the ratio of 3–4 boys : 1 girl. this is because the male hypothalamic-pituitary-adrenal (hpa) axis is more active. as males produce more cortisol than females under the same provocation, they can be tense or anxious and become repetitive. in a 2010 article, three genes were found by dennis drayna and team to correlate with stuttering: gnptab, gnptg, and nagpa. researchers estimated that alterations in these three genes were present in 9% of those 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, learning disabilities, and cerebral palsy. in others, 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 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 confirms 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 reduced when auditory feedback is altered, such as by 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. brain scans of adult stutterers have found greater activation of the right hemisphere, which is associated with emotions, than of 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 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. however, the precise nature of the capacity or incapacity has not been delineated. mechanism physiology though neuroimaging studies have not yet found specific neural correlates, there is much evidence that the brains of adults who stutter differ