Stuttering, Cluttering, and Fluency

The scope of this page includes stuttering, cluttering, and fluency across the life span. Acquired neurogenic and psychogenic stuttering are not covered.

See the Stuttering/Cluttering/Fluency Evidence Map for summaries of the available research on this topic.

Fluency refers to continuity, smoothness, rate, and effort in speech production. Individuals may hesitate when speaking, use filler words (e.g., “like” or “uh”), or repeat a word or phrase. These behaviors are called typical disfluencies or “stuttering-like disfluencies.” All speakers are disfluent at times.

A fluency disorder is an interruption to the flow of speech that can negatively impact an individual’s communication effectiveness, communication efficiency, and willingness to speak.

People with fluency disorders may experience psychological, emotional, social, and functional impacts (Tichenor & Yaruss, 2019a). Others may be indifferent to or proud of the way they speak.

The two main types of fluency disorders are stuttering and cluttering. Some people consider stuttering to be a neurodivergent communication variation. For further reading please see Campbell et al., 2019.

Definition of Stuttering

Stuttering is an interruption in the flow of speaking due to disfluencies. It is the most common fluency disorder and can affect the rate and rhythm of speech. Stuttering also typically involves

  • inappropriate reactions of others—the negative reactions toward stuttering from typically fluent speakers who do not stutter—or
  • negative internal reactions to speaking—the feelings that a person who stutters has about their stuttering.

Stuttering typically begins in childhood. Approximately 95% of children who stutter start to do so before the age of 4 years, and the average age of onset is approximately 33 months. Onset may be progressive or sudden.

Some children go through a disfluent period of speaking. It is also not unusual for disfluencies to first be apparent and then to seem to go away for a period of weeks or months—only to return thereafter. Yairi and Ambrose (2013) estimated that the recovery rates (with or without intervention) are approximately 88%–91%. Rates may be lower (approximately 60%) when considering child-reported recovery in addition to clinician and parent reports (Einarsdóttir et al., 2020).

Definition of Cluttering

Individuals may experience cluttering—either by itself (i.e., cluttering as its own standalone condition) or as influenced by another condition (e.g., cluttering that occurs during or after the onset of stuttering; van Zaalen-Op’t Hof et al., 2009).

Per St. Louis and Schulte (2011), cluttering is characterized by

  • a rate that is perceived to be abnormally rapid and/or irregular;
  • an excessive number of nonstuttering-like disfluencies;
  • frequent irregular patterns of pausing; and/or
  • frequent over-coarticulated speech.

Data are limited regarding the age of onset of cluttering; however, it appears to be similar to that of stuttering (i.e., approximately 33 months old; Howell & Davis, 2011). Typically, individuals are not diagnosed or do not start treatment until 8 years of age or into adolescence/adulthood—often only when someone else brings attention to their communication challenges (Ward & Scaler Scott, 2011).

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