Stuttering is a speech disorder characterized by interruptions in speech involving the repetition or prolongation of sounds and words, pauses between syllables and blocking — the momentary inability to produce any sound at all. It is sometimes accompanied by extraneous sounds such as grunts, body movements and postural rigidity as an individual tries to communicate. These breaks or disruptions that occur in the flow of speech are labeled “disfluencies.” 

According to the National Institute of Deafness and Other Communication Disorders (DIH), approximately 3 million American stutter. Despite the prevalence of stuttering, it is often difficult to identify people who stutter. Stuttering is variable, as the frequency and severity of a speaker’s disfluencies can differ substantially depending on the situation and time of day. 

A study conducted by researchers from the Haskins Laboratory in New Haven, Connecticut, analyzed the impact of social-cognitive stress on speech variability and speech production in general. It was found that adults who stuttered adopted a more restrictive, less flexible speaking approach when speaking in front of an audience.

However, there exist situations in which virtually all stutterers are fluent. A 1982 research study done at the University of South Wales revealed a 90% reduction in stuttering following 10 minutes of singing. This result was ascribed to an increase in phonation duration, the prolonged sustenance of a vowel sound. Another possible factor is that the time and social pressures present when speaking in front of an audience is absent when singing recreationally. Whereas public speaking can be debilitating for stutterers, singing to oneself can be more familiar. 

“When we sing, we generally know the words of the song by heart,” said Dr. Barry Guitar, Ph.D., CCC-SLP. “Word retrieval or searching for the words may play a role in stuttering.” 

One clinical implication of this variability is that it can be misleading for speech therapists when evaluating a client’s progress. What a clinician may see in the clinic on a given day may not be a true representation of the person’s fluency. The client may experience communicative pressure when talking to an unfamiliar person, causing them to stutter more than usual. However, the client may have already rehearsed their responses to their therapist’s questions beforehand, skipping the word retrieval step and making their fluency seem better than normal.

In addition to situational factors such as the presence of an audience, the time of day has also been shown to affect speech fluency. 

Studies done by the University of Alabama have shown a substantial improvement in speech during the afternoon and evening, compared to the morning. These studies suggest that for someone just beginning fluency treatment, it could be more ideal to have their therapy session in the afternoon, when the individual’s arousal level is higher. Additionally, practicing their speech at the same time everyday could reduce the speech variability that comes with speaking under different conditions. 

However, the clinical implications differ for someone who has already received treatment for an extended period of time. For these clients, it may be beneficial to include therapy sessions in the morning to practice stuttering strategies while their fluency is naturally decreased due to lower arousal levels. 

Though stutterers’ fluency may improve temporarily when they are taught various stuttering strategies, it is important to consider the clinical implications of forcing unnatural speaking methods on the client. 

“We know if we teach a person to speak in certain ways, it will reduce stuttering but it may not feel natural for them,” said Torrey Loucks, the appointed research chair for the Institute for Stuttering Treatment and Research in Canada. “There will be times when they use these therapy skills and other times when they switch back to the way they prefer to speak, which feels more normal to them.”

While the causes of speech variability are beginning to be understood, more research needs to be done on the causes of stuttering itself. Using a mouse model of stuttering, scientists from the Proceedings of the National Academy of Sciences of the United States of America reported that a loss of astrocytes, a supporting cell in the brain, is associated with stuttering. Other possible causes of stuttering include genetics, as studies have shown that 70% of those who stutter have a family member who stutters as well.

Whether the cause of stuttering is genetic or biological, it is important to take individual differences into account when coming up with a treatment plan.

“All kinds of treatments for stuttering can be good,” said Hilda Sønsterud, a certified European Fluency Specialist and international representative for the International Cluttering Association. “But in the future we need to be better at adapting treatment to each individual patient.”

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