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.