Cluttering research

Today it goes without saying that cluttering is a stand alone speech-language disorder that is different from stuttering in numerous ways. International researchers agree on the importance of differential diagnostics, and since cluttering was accepted into the classification of the World Health Organization (WHO), even more cluttering research has been carried out globally.

That research, however, is made somewhat complicated because no unambiguous and internationally accepted definition of cluttering exists. It appears to remain difficult to reach a consensus on the precise scientific definition of cluttering. An important part of that discussion has to do with the so-called “language component” in cluttering. Most researchers feel that “language” should be included in the cluttering definition, others don’t. It then boils down to what we exactly mean by this: are we defining “language” as (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.

Ken St. Louis

Ken St. Louis is a widely recognized expert on cluttering research and is considered one of the “grounding fathers” of this long neglected fluency disorder. Together with, amongst others, Florence Myers, Klaas Bakker and Larry Raphael he has put cluttering on the map worldwide and contributed a great deal to the scientific research in the field. In this video Ken St. Louis talks about his view on cluttering and 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 and has extensive experience as a lecturer and clinician. According to him there is still some uncertainty as to whether what are core symptoms in cluttering and what is optional. He talks about how the cluttering definition has changed over the years, and that some researchers think problems in language planning are essential to be able to speak of cluttering, while 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?

Kathleen Scaler Scott

Kathleen Scaler Scott is a very well-known name in the world of cluttering and stuttering. She has been working both as lecturer and clinician over the last decades and has seen many cluttering clients since. Kathleen Scaler Scott talks about her view on the definition of cluttering and the question how we could consider the “language” component of cluttering; is it required or optional? And are we talking about a language planning defect or a language disorder? Also, she addresses cluttering research and the work that still needs to be done for SLPs to better understand speech disorder cluttering as opposed to stuttering, that is still dominating the field of fluency disorders.

Nan Bernstein Ratner

Nan Bernstein Ratner, Professor in Hearing and Speech Sciences and President of the International Fluency Association, 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, personal experiences and other data in Fluency Bank. Ultimate goal is to advance the science of speech and language pathology and improve treatment strategies for stuttering or cluttering. Nan Bernstein Ratner calls on researchers in the field of cluttering to internationally co-operate and share their data to bring forward cluttering research.

Cluttering definition

One of the pioneers in scientific research on cluttering has been Professor Ken St. Louis. In the 1990s and later, St. Louis made an effort to better define clutter. He therefore conducted a number of studies comparing individuals with a possible diagnosis of cluttering with stutterers and typical speakers. This comparative study resulted in a working definition that is still widely used to this day.

In addition to 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 

This definition leaves room for, in addition to the above-mentioned symptoms, other characteristics that often occur in cluttering. Cluttering is increasingly regarded as a disorder that occurs together with, for example, other communication disorders, language disorders, learning disabilities and/or attention disorders.

Cluttering prevalence

Because there is no internationally used definition of cluttering, there are no clear figures about the prevalence of cluttering (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.

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