Untitled

Abstract

A theory has been proposed recently that asserts that the problem that people who stutter have arises when these speakers attempt to execute speech at a faster rate than planning processes allow. This leads speakers to complete words before the following one is ready. Plan unavailability usually happens on the more complex content words rather than the relatively simple function words. There are two ways of dealing with this situation when it arises. Speakers can (1) delay production of a content word by repeating prior function words or (2) carry on and attempt to produce the following content word and gamble that the remainder of the plan arrives while it is being executed. The former strategy does not lead speakers to persist in their dysfluency, while the latter does. It is proposed that the pressure on speech rate that leads speakers to adopt the latter strategy is particularly acute around adolescence. In this article two experiments are reported which test the effects of rate on fluency. In Experiment 1, fluent speakers are induced to produce stuttering-like dysfluencies on content words using a commentary task. A prediction of the theory is that procedures known to induce fluency have to produce local slowing of speech so that planning and execution can get back in synchrony. This prediction is confirmed for frequency-shifted feedback and when speakers who stutter have to sing in Experiment 2. Results are discussed in terms of the model for the etiology of stuttering based on plan unavailability. The implications of the results are also discussed with respect to the diagnosis of the disorder and how it can be treated.

Strength of German accent under altered auditory feedback

“…It is proposed that speakers operate at some point on a speed-accuracy continuum. In taxing circumstances (e.g., under AAF when the number of stimuli increase or when an extra response—dual task—is required), if speakers attempt to speak too rapidly, errors will ensue (Blackmer & Mitton, 1991; Howell & Sackin, 2000). Alternatively, they can avoid making errors by regulating speed to a slower rate; hence, the term tradeoff .…”

“…Up to this point, fluency failure could be avoided by slowing speech, but no further rate adjustment will be possible. If a higher rate than this is maintained, it will lead to fluency breakdown in the regions where linguistic demand is high (Au-Yeung, Howell, & Pilgrim, 1998), since there is evidence that speakers attempt to produce speech before planning is complete in these circumstances (Blackmer & Mitton, 1991; Howell & Sackin, 2000). If this strategy is maintained, it would also be expected that there would be a high chance of errors persisting into later life (i.e., a heightened chance of longterm stuttering).…”

“…Speech rate may need to be regulated independent of linguistic processes (Howell, Au-Yeung, & Rustin, 1997; Howell et al, 2000; Howell & Sackin, 2000). Ivry (1997) has identified the lateral part of the cerebellum as a structure that does this.…”

“…Howell, Powell, and Khan (1983) accounted for the effects of DAF as being due to poorer performance when speech takes place along with an asynchronous rhythm (the delayed version of the voice in the DAF situation). Howell and Sackin (2000) and Howell, Rosen, Hannigan, and Rustin (2000) explained the effects of DAF and frequency-shifted feedback (FSF) as being due to degradation in performance when speaking along with concurrent separate perceptual streams. DAF would be one way of producing a second sound “stream” that is separated from the voice because of the temporal asynchrony.…”

Signs of developmental stuttering up to age eight and at 12 plus

“…For this reason, recent attention has shifted to variability in speech timing control (Howell, Au-Yeung & Pilgrim, 1999; Howell & Sackin, 2000; Smith & Kleinow, 2000). The results show that stuttering is associated with local increases in speech rate (Howell et al, 1999; Howell & Sackin, 2000) and increased timing variation (Smith & Kleinow, 2000). No studies have been done to establish whether these effects occur specifically with persistent speakers.…”