Introduction

Most people around the world have an idea what stuttering is all about, but are not familiar with the fluency disorder cluttering. Cluttering is a disorder of speech fluency, in which a person is not capable enough to adjust his/her speech rate to the syntactical (grammar) or phonological (word structure) demands of the moment. (Van Zaalen, 2009). People with cluttering (PWC) often say: "I think I stutter, but actually it is not real stuttering". Or, they say: "Others always complain that I am not intelligible and speak to fast, and I want to get rid of these responses". The language production difficulties in PWC manifest itself, when language development is in an advanced state and a person has a strong inner urge to speak. Therefore, cluttering can be diagnosed in persons of ten years and older. Difficulty in expressing relatively complex messages seems to play a role in the severity of cluttering.

This paper aims to answer the question of whether language planning disturbances are a causal factor in cluttering. To do so, we use a picture of the mental machinery underlying spoken language production, provided by Levelt's (1989) and discuss how this model can contribute to a better understanding of cluttering. We also want to give an answer to the question why some people with cluttering express disfluencies and others are less intelligible. Finally the question why cluttering is present in some moments and absent in others will be answered.

To explain the basis of the disfluencies and intelligibility problems in cluttering it is important to understand the processes of language formulation before the moment of language production. According to Levelt (1989) the expression of ideas happens in three steps. The first step concerns compiling the idea or message and monitor if this is an accurate moment to express this message. Everyone will recognize that when you are too careless you can tell stories that you later regret. In those cases this monitor is not functioning well enough. The second step is formulation of the message in correct grammatical sentence structures. The sentences are build with words that are gathered from the lexicon. Every word within the sentence has to be build up itself as well. Words are build with syllables. Syllables have to be pronounced in the right order (so 'bi-bli- o-gra-phy' and not 'bli-bi-gra-phy-o') and in the right way (not: 'bli-bli-o-gra-phy'). When the sentences and words are planned, a person can express his thoughts, the third step.

A PWC speaks in a fast speech rate. That means that the speed in which all three steps of language production have to be finished, is limited. And sometimes too little. It is a well known fact that a PWC can be fluent and intelligible when concentrated on speech rate. Reading out loud is also fluent and intelligible in most PWC. Furthermore, the cluttering behaviour seems to increase in those circumstances were the person is relaxed (i.e. within the family, or with friends). What is the explanation for these differences in performance? I refer to three concepts: language automatization, attention and speech rate. In the next part of this paper I will highlight the most important facts on all three concepts.

Language automatization

Firstly, correct sentences can be produced at a fast speech rate if the process of language formulation is automatized. Sentences are build up, using accurate words and words are planned and produced as wanted. Language formulation processes in cluttering are insufficiently automatized. Either planning the sentence or the word structure is not ready within the available time. When language formulation is insufficiently automatized, errors in language production can be expected. Errors in language production can be disfluencies or speech errors.

Two different categories of speech disfluencies exist: normal disfluencies and stutter-like disfluencies. Normal disfluencies are those disfluencies that any person experiences in running speech, like word repetitions ("But, but, I can"), interjections ("uh" or extra pauses), part sentence repetitions ("I will, I will go") and revisions ("I go, I went home"). Stutter-like disfluencies are those disfluencies that are characterised by a feeling of loss of control, for instance sound repetitions ("b-b-b-barbie"), prolongations ("aaaaaaaanimal") or blocks ("I..Interesting") and can be accompanied with physical or emotional tension. Speech errors in cluttering are usually expressed by telescoping the syllables ("disaur" instead of "dinosaurs") or mixing up the syllables ("bli-bi-gra-phy-o") and make a persons speech unintelligible.

The appearance of normal disfluencies can be best explained by a time gaining effect. A person repeats that part of the message that has already been planned or adds a pause, and by doing so gains time to plan the rest of the sentence. It is as if we can hear the person think and formulate. Speech errors occur because the errors are not detected in the fast speech rate. When the error was detected the speaker would have repaired the error. Although PWC are able to recognize speech errors in their recorded speech, they are unaware of the speech errors in running speech. In running speech they do not seem to pay attention to it enough. Or, they can not pay enough attention to it.

In summary, in cluttering defective language formulation automatization is present. The extent of language production automatization in PWC, determines if speech result in either a higher than normal frequency of normal disfluencies or unintelligible speech.

Attention

If, due to a lack of automatization, much attention is needed to complete the sentence or word plan, fewer resources remain for other processes, particularly monitoring and articulation. Consequently, many language production difficulties remain. Therefore, PWC do not detect and repair all errors. In order to detect and repair an error, an appropriate monitoring system is needed.

A lack of responses to speech errors or disfluencies can be a sign of weak monitoring (control and repair) skills. PWC are able to monitor their speech, when attentional resources are not needed so much for language formulation (sentence and word structure), as, for instance, in producing nonsense syllables, retelling a memorized story or naming their daily activities.

PWC are usually more disfluent and less intelligible while talking in a home environment, compared to, for instance a classroom situation. The same child can be mostly fluent in a classroom and mostly disfluent at home or with friends. Besides the speech and communication rate, attention plays it role as well. When a person is tired or at home his or her attention to speech production is often less compared to speaking at work.

When attentional resources are fully involved in language formulation, as is the case in complex speech formulation tasks, no capacity is left for recognizing and repairing speech errors. Thus, it is hypothesized that a "double deficit" exists in cluttering: a deficit in language formulation due to inadequate automatization, and as a result of that, weak monitoring, because the processing capacity is used for the formulation processes. Or in other words, formulating the sentence and articulate the words in running speech is difficult enough, and controlling speech production is sometimes just out of the question for PWC.

Speech rate

Language formulation problems in PWC disappear in a slow speech rate and are detected by the PWC when listening to their recorded speech. These are indications of a problem in language production automatization. Persons without cluttering adjust their speech rate to the difficulty of the message. They speak slower when the story, sentences or words are more complex and faster when language production is relatively easy. PWC are not able to adjust their speech rate to the language complexity for a long while.

Cluttering has a strong genetic base. 85% of PWC have a family member with speech language problems. Family of PWC often clutter themselves. Speech rate in these families can be fast and be a (negatively) stabilising factor in the communication of the adolescent or adult. It is very difficult for one member of a group to change his or her behaviour when the others in the group continue the behavior.

PWC seem to monitor insufficiently in fast speech rate, but are able to monitor their speech for a while when they slow down speech rate. To remain talking in a slow rate much attention is needed. In running speech a PWC is not able to remain the slower speech rate for a long time, because all attention capacity is needed for language formulation.

Summarizing

Cluttering is a language based fluency disorder. When language production is relatively easy a person with cluttering is capable to produce fluent and intelligible speech. When language production is more difficult, speech rate should be adjusted to the language complexity. Because PWC need their attention to formulate sentences and words, no attention capacity is left to control speech rate. Depending on the level of language automatization, this results in either a higher than normal number speech disfluencies or unintelligible speech.

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