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Practical Thoughts Blog

What percentage of stuttering behavior is normal?

What percentage of stuttering behavior is normal?

A recent Facebook post asked what percent of disfluency was considered to be in the normal range.

Like so many questions surrounding stuttering, the answer turns out to be somewhat complicated! Historically, people have used various set values, such as 3% syllables stuttered or a 10% overall disfluency rate to indicate that a person’s speech fluency was above or below normal limits.

While these metrics may have their place, I want to highlight some of the (many) concerns with using frequency counts for identifying people who stutter and of using average numbers of disfluencies for diagnostic or treatment purposes. Most important among these concerns is the fact that  frequency of stuttering a person exhibits doesn't tell us much about whether the person needs therapy (or even how he's doing in therapy). Beyond that, what we do with frequency information also depends a lot upon the person’s age.

For a preschool child, it is far more important to consider other factors than the frequency or severity of stuttering behavior, for research has shown that the amount of stuttering a child exhibits doesn't relate to whether or not the child needs therapy. A child may be well above the 2% or 3% syllables stuttered or even the 10% overall figures cited above yet still not need intervention. Another child may be below those numbers but still need help. The real factor in determining whether or not a preschool child needs therapy is whether he is at risk for continuing to stutter. If he is at risk, then therapy is indicated; if he is not, then you will probably still want to do some work to educate the parents and others about the child's fluency development, but it may not be as necessary to enroll the child in formal intervention immediately. (Several of our other blog posts address these questions in more detail.)

For a school-age child, adolescent, or adult, the amount of stuttering (frequency or severity) really isn't a factor in determining whether the person needs treatment. In the schools, we are supposed to qualify children for intervention based on whether they are experiencing adverse impact as a result of the communication difficulty. For adults, the same issue holds: the need for therapy is based on impact rather than on the amount of stuttering. Some people may exhibit a lot of stuttering and have minimal adverse impact (and therefore not need intervention); others may exhibit minimal observable stuttering behavior but need help because they are avoiding talking or changing words and not saying what they want to say. Therefore, other measures, such as the Overall Assessment of the Speaker's Experience of Stuttering (OASES; Yaruss & Quesal, 2016), are far more important for determining whether a person needs therapy. 

All of these concerns about the observable frequency of stuttering are in addition to the fact that stuttering is highly variable. The frequency count or severity rating that you get in one situation isn’t necessarily the same as the frequency count that you’ll get in another situation. This means that we need to collect data in multiple settings to understand the range of stuttering behaviors a person exhibits. (Even then, this doesn’t tell us about impact, but at least we’ll get a better measure of the observable features.)

There are also difficulties with the reliability of measurement of stuttering behaviors. Ample literature has shown that without training, clinicians are not terribly reliable and making stuttering frequency count judgments. Fortunately, research also shows that training can help! If you find that you do need to make frequency counts, you can improve your ability to do that by taking courses on stuttering measurement. (For example, I have a series of courses on stuttering measurement at MedBridge Education. Using this link, you can save $175 on your annual MedBridge subscription! www.MedBridgeEducation.com/scott-yaruss).

There’s so much more to be said on the topic of stuttering measurement, but the most important piece to remember is this: there really is NO predetermined or set frequency of stuttering or disfluency behavior that tells us whether a speaker needs therapy. We need to consider factors other than just the observable frequency of stuttering when determining whether a person who stutters needs therapy, making decisions about the nature of that therapy, and examining their progress in therapy.

“Stuttering is more than just stuttering,” so our assessment and treatment should examine more than just the observable speech behaviors.