Cluttering research

It goes without saying that cluttering is a stand alone speech-language disorder. It is different from stuttering. Because of that international researchers agree on the importance of differential diagnostics. Ever since cluttering has been accepted into the classification of the World Health Organization more research on cluttering is carried out globally.

That research, however, deals with a complicating factor: different viewpoints amongst researchers on the exact meaning of cluttering. Because there is no clear and internationally accepted working definition, it is difficult to compare diagnostic material and their results. Part of the disagreement has to do with the so-called “language component” in cluttering. Some researchers feel that “language” must be included in the cluttering definition, some don’t. It then boils down to what we exactly mean by “language”: the executional function of language planning or the more executive function of language organization. At least all researchers do agree that problems in language planning or language organization regularly occur in people who clutter. See what experts in the cluttering community have to say about this.

Kathleen Scaler Scott

Kathleen Scaler Scott is a well-known name in the world of cluttering and stuttering. She works as a lecturer and clinician and meets many cluttering clients. Kathleen elaborates on how she defines cluttering, also addressing the “language” component of cluttering; is it required or optional in the definition of cluttering? And are we talking about a language planning defect or a language disorder? Also, she lays out the work that needs to be done in cluttering research, so that speech-language pathologists will better understand the meaning of cluttering. After all, stuttering is still dominating the field of fluency disorders.

Ken St. Louis

Ken St. Louis is a true expert in cluttering research and one of the “grounding fathers” of this long neglected fluency disorder. Together with Florence Myers, Klaas Bakker and Larry Raphael he has put cluttering on the map. They all contribute immensely to scientific research in the field. In this video Ken St. Louis talks about his view on cluttering. He describes how he and Katrin Schulte came up with the so-called Lowest Common Denominator definition. The LCD excludes a number of symptoms often reported by clinicians that at least seem to be related to cluttering.

David Ward

David Ward is a well-respected figure in the domain of cluttering research. He has extensive experience as a lecturer and clinician. According to David there is still some uncertainty about the core and side symptoms of cluttering. He explains how the cluttering definition has evolved over the years. Some researchers think problems in language planning are essential in cluttering. Others may stick with the Lowest Common Denominator, leaving out language planning from its core definition. An interesting question that researchers are now breeding on! Will cluttering one day be unraveled?

Nan Bernstein Ratner

Nan Bernstein Ratner is Professor in Hearing and Speech Sciences and President of the International Fluency Association. She also co-directs Fluency Bank, the world’s largest data repository of various kinds of speech and language disorders. Researchers and people with fluency disorders can donate their speech samples and other data in Fluency Bank. The ultimate goal is to advance the field of speech-language pathology. And at the same time improve treatment strategies for stuttering or cluttering. Nan Bernstein Ratner invites researchers in the field of cluttering to internationally co-operate and share their data.

Cluttering definition

Professor Ken St. Louis is one of the pioneers in scientific research on cluttering. He has tried to better define cluttering by comparing potential cluttering individuals with stutterers and typical speakers. This comparative study has resulted in a working definition that is still widely used.

Besides an excessively high and/or irregular speech rate, one or more of the following core characteristics must be present:

  • Excessive ‘normal’ disfluencies (like repetitions, sentence revisions)
  • Excessive collapsing or deletion of syllables (telescoping, poor articulation)
  • And/or abnormal pauses (too few, too short, etc.), syllable stress (wrong use of intonation or melody, monotony) or speech rhythm 

In addition to the above-mentioned symptoms, St. Louis’ definition leaves room for other characteristics that are often seen in cluttering. Cluttering is often related to, for example, other communication disorders, language disorders, learning disabilities and/or attention disorders like ADHD.

Cluttering prevalence

Because there is no internationally used definition of cluttering, there are no clear figures about its prevalence (the frequency with which the disorder occurs). In addition, people who clutter are not always aware of their own symptoms. So, they are less likely to seek professional help. Also, cluttering often occurs in combination with stuttering. This makes it difficult to determine the exact prevalence. With our self-test you can easily get an initial idea of whether someone clutters or not. 

In the adult population, 1-2% is a non-fluent speaker. Pure cluttering occurs in 5-16% of non-fluent speakers. And 21-67% of stutterers also exhibit cluttering characteristics. This means that cluttering occurs more often than the literature suggests. There are even indications that cluttering and stuttering are almost equally common. Cluttering is more common in men than in women, in about the same ratio (4:1) as in stuttering. However, we should use these figures with caution since they are not based on the same definition.


Dr. Scott Yaruss talks about a new cluttering research project: the OASEC, a tool developed for speech-language pathologists to feel more comfortable in diagnosing cluttering. The OASEC is different in that it zooms in on the EXPERIENCES of people who clutter and the IMPACT that the cluttering has on their lives. It is a mean to understand from a clinical point of view how we can help to diminish the adverse impact. But also from a personal point of view. This is especially important because cluttering is widely misunderstood. Ultimately the OASEC might be helpful in designing treatment for people who clutter and relieving the burden.

SLP? Display your practice

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