Stuttering is “a disruption in the fluency of verbal expression characterized by involuntary, audible or silent, repetitions or prolongations of sounds or syllables.” Such disruptions are largely uncontrollable and may be accompanied by other physical movements such as jerking or twitching, as well as negative emotions like fear and embarrassment. Technically, “stuttering is a symptom, not a disease, but the term stuttering usually refers to both the disorder and symptom.” While language development in generally is not particularly well understood, even less is known about speech disorders like stuttering.
Persistent developmental stuttering (PDS) usually displays between two and five years of age, and does not have a known cause (e.g., apparent brain damage). Acquired stuttering is rare and occurs after a definable brain damage (e.g., stroke, hemorrhage, or head trauma).
Approximately 1% of the adult population presents this condition, which may severely impair communication, and may have devastating socioeconomic consequences. Famous stutterers include Winston Churchill, Charles Darwin, and actor Bruce Willis. Darwin’s grandfather Erasmus Darwin also stuttered, which illustrates the fact that “stuttering runs in families and is likely to have a genetic basis.” Studies show that if one monozygotic twin stutters, there is a 70% chance the other one will.
In children, the incidence of PDS is about 5%, and its recovery rate is up to about 80%, Girls more likely to recover than in boys, so by adulthood, men are 3-4 times more likely to stutter than women. There is no way to predict who will recover. “Stuttering occurs in all cultures and ethnic groups, although prevalence might differ.”
For most of the century, stuttering was largely thought to be a psychogenic disorder; however, studies of personality traits and child–parent interactions have not revealed any correlations or patterns related to stuttering. As neurological understanding improves, a two-factor model emerges. Stuttering is thought to derive from a structural or functional central nervous system (CNS) abnormality, accompanied by reinforcing psychological factors such as avoidance learning. The physiological model is supported by that fact that other physical symptoms often occur. For example, stutterers often experience delays in tasks requiring a vocal response, and may have difficulty with bimanual tasks such as threading a needle. Various forms of auditory stimulation (e.g., chorus reading), and alteration of speech rhythm (e.g., syllable-timed speech) can cause dramatic reduction in stuttering frequency, suggesting probable abnormalities in a stuttering child’s auditory feedback mechanism.
Researchers use tools like EEG, positron emission tomography (PET), and functional magnetic resonance imaging (fMRI) to analyze brain activity. In fluent speakers, the left hemisphere of the brain is largely dominant during speech; stutterers display increased activity in their right hemisphere, which may or may not be compensating for dysfunction in the left hemisphere, as sometimes occurs after stroke. FMRI studies “have revealed two important facts: (i) in stutterers, the right hemisphere seems to be hyperactive, and (ii) a timing problem seems to exist between the left frontal and the left central cortex.”
I see the primary implication for teachers is that they must not exacerbate stuttering problems by focusing on them in a dramatic way. Such focus can cause increased anxiety, which could make the symptoms worse and discourage speech in general. If possible, teachers should have a speech professional observe the child in a natural setting, and then follow his or her recommendations for more formal assessment and possible treatment.
Büchel, C. and Martin Sommer, M. What Causes Stuttering? PLoS Biology. Volume 2(2). February 17, 2004. pp. 0159-0163.
Added by Bob Jarvis.