In a recent chapter, Caruso, Max & McClowry (1999) examine the term "motor speech disorders" with particular emphasis on childhood stuttering. Speech-language clinicians and researchers often distinguish among different communication disorders on the basis of the processes underlying those disorders. For example, the group of acquired neurogenic disorders known as the aphasias typically is described in terms of underlying deficits in various linguistic processes (e.g., agrammatism). Dysarthria and apraxia of speech, on the other hand, typically are described in terms of underlying disturbances in peripheral or central aspects of speech motor control. In light of this perspective, dysarthria and apraxia of speech are generally categorized as motor speech disorders (e.g., Duffy, 1995). In fact, these two disorders, in both their developmental and acquired forms, have become so tightly linked to the concept of speech motor disorders that they are often listed as the only examples for this class of speech disorders (e.g., Crary, 1995; Kent, 1990; Strand, 1995). Nevertheless, any speech disorder that is associated with either a nervous system lesion or a dysfunction of the sensorimotor processes underlying speech production could be correctly classified as a motor speech disorder. In this paper, we propose that currently available empirical data suggest that stuttering may be one example of a disorder that is based on a dysfunction, rather than lesion, of the central nervous systems sensorimotor control mechanisms. Viewing stuttering as a motor speech disorder has important theoretical and clinical implications. Theoretically, it provides a framework that can be used to develop testable hypotheses regarding the nature of stuttering in children and adults. Clinically, this viewpoint has several benefits. First, it focuses treatment on the temporal and spatial requisites obligatory for fluent speech production. Second, it empowers clinicians to develop treatment protocols based on their understanding and working knowledge of sensorimotor contributions to speech motor output. Third, treatment planning from this perspective would increase the likelihood that alterations in the course of treatment for a particular client are consistent with what is known about programming and execution of fluent speech.
While relatively few studies have examined processes of speech motor control in children who stutter, there is some evidence that children who stutter exhibit difficulty in the planning or programming of speech movements. In light of the limitation on the length of this paper, we refer the reader to Caruso et al., 1999 for a review of motor speech studies in children who stutter. In light of these findings, it seems reasonable to incorporate methods or strategies to improve multiarticulate serial movement with children who stutter. In the remaining portion of this paper, the utility of applying what is known about human neuromotor movements and factors that influence motor performance will be discussed relative to childhood stuttering.
Clinical Utility of a Motor Speech Perspective on Childhood Stuttering
Viewing childhood stuttering as a motor speech disorder has several benefits for clinicians. Indeed, one major assumption underlying this approach is that young children who stutter unless changes are made in articulatory dynamics as well as the coordination of those dynamics with respiration and phonation will not achieve fluency. Second, it facilitates development of treatment protocols based upon principles of motor learning (Schmidt, 1982). Thus, changes in, for example, oral motor events for speech which are necessary for fluency, can be supported by treatment planning that parallels or is consistent with established theories in neuroscience, motor learning and speech motor control. One question we are often asked by clinicians is "Where and how do I begin getting this child to be fluent?" Clearly, this theoretically based treatment approach provides a framework that can benefit clinicians in their development of a course of treatment for a particular client. Third, fluency treatment that is based upon motor learning theory is advantageous to clinicians--particularly those clinicians who determine that, due to a child's lack of progress, alterations in treatment are warranted. Based on our observations of both professional and student clinicians, often times the difficulty for these clinicians is not a failure to recognize that changes in the course of treatment are warranted. Rather, our observations suggest that the difficulty for many fluency clinicians is how to alter treatment and remain consistent with the goals of therapy and the accepted finding regarding neuromotor processes under fluent speech.
The purpose of this paper is to encourage clinicians to adopt a motor speech perspective on stuttering therapy. We will discuss some general strategies toward childhood fluency therapy that are consistent with the perspectives previously discussed in this paper. Note, however, a thorough discussion of fluency treatment, and techniques to facilitate fluency are beyond the scope of this document. There are several sources available re: stuttering treatment which provide both broad and detailed information in this area (cf., Conture, 1990; Max & Caruso, 1997; Yaruss, 1997). Moreover, several authors have discussed the benefits of applying motor learning theory to clinical management of children with motor speech disorders in a recently published book (see Caruso & Strand, 1999). Specific to fluency disorders, we have discussed our views on motor learning theory in previous publications (Caruso & Max, 1997 ; Max, Caruso & Vandevenne, 1997). Our focus here is to provide information on aspects of fluency therapy that, in our view, are consistent with a motor speech/learning perspective on stuttering in order to encourage others to adopt and implement this perspective in treatment.
Rate of speech: "Slow" is better when learning a new skill.
As individuals learn novel tasks, or refine previously learned tasks, rate of performance has often been observed to be relatively slow in the beginning and speed up as skill level increases (Schmidt, 1988 ). One of the most robust findings in the stuttering treatment is that reduction of the client's speech production is an important variable in facilitating fluency. Although there are differing opinions as to why reduced rate of speech typically has a positive influence on fluency (cf. Ingham, 1990; Kalinowski, Armson & Stuart, 1995), there is general agreement that a slow rate permits more time for the speaker to program and/or execute speech movements and thus facilitates coordination for serial multiarticulate movements, respiration and coordination (e.g., Kent, 1984). It is interesting to note that stuttering, for most children, begins between 3 - 4 years of age, the same time of development that timing for speech typically becomes more refined (Netsell, 1981). It seems reasonable to suggest that children who stutter--i.e., children who are impaired in their abilities for speech timing and whose sensorimotor mechanism is still developing/evolving, would particularly benefit from a reduced rate of speech. The challenge to clinicians is that "slow" and "fast" are abstract concepts that may not be fully understood in young children near the onset of stuttering. Thus, some clinicians (see Conture, 1990) advocate pairing the abstract notion of "time" with concrete examples of "slow" and "fast"' and describe speech to the child as "turtle speech" or "rabbit speech."
It may be just as important to model a slow rate of speech for children who stutter as it is to have them reduce there own rate of speech. There is some evidence that disfluencies decrease when the communication partner's speech is slow (Guitar, Schaefer, Donahue-Kilburg & Bond , 1992). Moreover, this increase in fluency has occurred in conjunction with and increase in both the number of words per conversational turn and the number of conversational turns during the dyad (Caruso & Rolwing, in progress). Thus, it seems that children become more fluent as well as more verbal when speaking with a partner with a reduced speaking rate. One hypothesis regarding these results states that the partners model may provide a temporal model that the child who stutters utilizes in programming or planning speech movements (Caruso & Rolwing, in progress). For further information regarding different methods of rate reduction and the influence of the communication partner, see Logan & Caruso, 1997 and Max & Caruso, 1997).
Number of Movements
It is generally acknowledged in the nonspeech literature, that practicing a single novel movement facilitates motor learning for complex (e.g., multiple movements) tasks (Schmidt, 1988). Relative to speech, individuals who stutter appear to have an easier time producing, e.g., single word utterances versus multi-word phrases and sentences. Many therapies advocate starting at a single word or short phrase level and gradually increasing length and complexity of the utterance. Although it has its roots in operant conditioning, the fluency treatment by Ryan is consistent with this factor in motor learning (Ryan, 1974). Another way to manipulate the number of speech movements by the child who stutters involves the use of different question types by the communication partner. Use of different questions (asked by a communication partner) is one way to manipulate the number or words spoken by a child. Thus, to facilitate motor learning, a communication partner to provide an opportunity for the child to practice speech movements during fluency could utilize "low level demand" question (e.g., questions that can be answered with a single word response). Clinicians should assess this relationship between length of response (i.e., number of movements) and disfluency (Conture & Caruso, 1987) to determine when fluent ("typical") movements breakdown as the demand for an increase in number of speech movements increases by asking more open-ended questions. Communication partners can be trained to modify their question types to facilitate fluency when talking with children who stutter (Logan & Caruso,1997).
Other Variables Affecting Motor Learning: Implications for Fluency
Motor learning in general is known to be influenced by several factors: (1) the amount of repetitive practice; (2) feedback in the form of knowledge of results vs. knowledge of performance; (3) the schedule under which practice trials are performed, and, (4) motivation of the subject (see Caruso & Strand, 1999). Rarely have these variables been studied in stuttering. One notable exception is a study by Brutten and Dancer (1980) on the effect of two different types of practice on stuttering frequency. Their findings demonstrate that a greater reduction of stuttering occurred during blocked practice (each word repeated 5 times before proceeding to the next word on a list) than during random practice (the list was read in its entirety five times in succession). Unfortunately, however, this is one of the few studies on the principles of motor learning and stuttering. Needed are studies of the effects of any practice schedule on stuttering frequency during a retention task (designed to determine if a new skill was in fact learned vs. a temporary improvement in motor performance). Another important variable that needs to be addressed is the effect of speech rate during practice as well as retention tasks. Such studies are timely, particularly with children, as changes in health care bring increased demands to document effectiveness of treatment. Evidence that certain types of practice are effective with children near the onset of stuttering would have a valuable impact on clinical management of children who stutter.
Summary and Conclusions
We believe that effective treatment for children who stutter can only be provided if clinicians understand what is known as well as hypothesized regarding the programming/planning and execution of speech movements in this population. Clearly, while there is much that is unknown, there is evidence that a motor speech perspective provides a framework that will increase our understanding of this disorder. Moreover, the potential benefits of motor learning to fluency disorders in children is compelling and could be an important application in fluency treatment. We believe that increased understanding of the disorder of stuttering, sensorimotor processes underlying (dis)fluent speech and motor learning theory will help clinicians become more confident in there abilities to treat children who stutter (Sommers & Caruso, 1995). While no one approach is likely to be appropriate for all children who stutter, the strategies discussed in this paper are likely to facilitate change in articulatory kinematics (see Caruso & Strand, 1999). Of course, there is more to stuttering treatment than kinematics. The nature of the communication environment and the attitude of the child who stutters are only 2 of several other variables. However, the "bottom line" of stuttering treatment is increased fluency--which can only be achieved if the child who stutters learns to move the vocal tract structures in ways that are associated with or contribute to the production of fluent speech. In that light, a motor speech perspective on stuttering can provide a framework to enhance clinicians understanding of this disorder as well as ways to manage it.
Note: Readers of previous versions of this paper suggested that I include additional readings in stuttering, speech motor control and motor in light of the diverse audience attending this online conference. I hope you will find the below additional readings (which include the references cited in the body of this paper) to be helpful.. --AJC
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