“We are born too soon to understand how the intermorphemic breaks in fluency we call stuttering are really produced, but it seems highly plausible that distortion in the total feedback signal system may be responsible for them.” (Van Riper, 1971, p. 395). Trying to answer the question of how stuttering is produced – that’s my objective on this website. I propose a theory of developmental stuttering, and distortion in the feedback signal system plays a crucial role in this theory.
Stuttering has been a subject of research for a long time, and many theories of its nature and origin were proposed. Today, thanks to new technical capabilities in brain research, we know much more about what is different in the brain of people who stutter, compared to normal fluent speakers. Additionally, some specific mutations have been detected in the genome of families in which stuttering frequently occurres. However, up to now we don’t know how such deviations in the brain or in the genome make people, against their will, repeat words or parts of words, prolong speech sounds, or get totally stuck.
A lot of empirical data about stuttering and about people who stutter was collected in the last decades without leading to a convincing, generally accepted theory. It is, however, impossible to logically derive theories from empirical data – data can, at most, falsify a given theory. Theories are the result of thinking and modeling. Empirical data, on one hand, can serve as suggestions giving thoughts a direction, and, on the other hand, they are bottom-up constraints confining the number of possible and plausible assumptions.
The theory presented on this website tries to explain the pathomechanism of developmental stuttering. It is a product of thinking and modeling, and it can be false. However, many features of the disorder are well known, thus we can formulate many questions of how these features come about. A theory of stuttering has to answer those questions in a coherent and consistent manner. If a theory is able to do this, then we should consider it a good candidate for the true theory.
Feb 19: On the paper by Chesters et al. (in press) (blog entry)
Jan 26; Persistence versus recovery (blog entry)
Jan 2: On the paper by Neef et al. (in press) (blog entry)
The role of auditory feedback and the role of breathing in stuttering have been controversially discussed for some time. Alterations of auditory feedback often reduce stuttering, and certain breathing exercises seem to be helpful in the treatment of stuttering. However, the mechanisms underlying those effects are still poorly understood. On this website, a theory is proposed in which persistent developmental stuttering is regarded to be mainly caused by disruptions of the auditory feedback of speech, but also by a deficit in the proprioceptive or kinesthetic feedback of breathing. The feedback deficits are ascribed to a misallocation of attention during speech. It is assumed that, due to these feedback deficits, the ends of words, syllables, or phrases, but also the ends of breathing-in phases are not detected by a monitor in the control system, with the consequence that the subsequent speech unit gets blocked. The theory allows to account for the emergence of childhood stuttering, for the way stuttering becomes persistent, for the typical positions of stuttering events in sentences, and for the variability of stuttering depending on syntactic complexity, anticipation, and environmental factors.
The figure shows the core idea of the proposed theory: The detection of a speech error (left) and stuttering (right) are based on the same mechanism; the internal monitoring system (in the circle) behaves equally in both cases. The disruption of auditory feedback (at the right side) is thought to be caused by too little attention to the auditory channel during speech, i.e., by too little perceptual- or processing capacity for auditory feedback.
The main theses of the theory are:
The figure shows the causal chain underlying a primary stuttering symptom. The causal chain closes to a vicious cycle if the experience of stuttering results in the expectation (or fear) of stuttering such that the speaker’s attention is focused on the disorder during speech (see figures below)
The figures show the vicious cycle of persistent stuttering. Above: with some secondary behaviors that reinforce the vicious cycle. Below: with factors (perhaps genetically caused) that may contribute to a predisposition for stuttering, and factors that influence the frequency and severity of the symptoms (the cycle was rotated here only for reasons of depiction). The crucial part of the vicious cycle and the main interface to all influencing factors is the misallocation of attention.
Not without reason, a labyrinth is the logo of this website. The theory consists of many parts connected with each other. I had to anyway put them in a succession, but the reader has not to follow this order. The theory of stuttering is contained in Chapter 2. Chapter 1 deals with normal fluent speech and especially with the role of auditory feedback. The chapter contains some assumptions that are basic for the proposed theory. In Chapter 3 and 4, some special issues are discussed in the light of the proposed theory.
The main text is distributed over several pages. You can go from the list of contents to every page, but also flip from page to page. Footnotes are linked with the main text; references are linked with resources in the web if possible (some of them are linked with PDF documents, download may need some time). The search function is not ideal because it displays the pages only on which a term occurs – but look at the index page where you find many important terms linked with the relevant paragraphs in the text.
The German version of this website has been online since March 2014. The English version contains all chapters of the German version. but I have put the German Chapters 2 and 3 into one chapter, it is the Chapter 2 here. I’m going to improve the text with time and to keep it topical by including new empirical findings. I’m always grateful for criticism and suggestion, including pointers to typos, grammatic or idiomatic mistakes.