By Anne Smith, Ph.D.,Purdue University
Speaking is many things — it is thinking of what one wishes to say, choosing the right words from our vocabulary, putting the words in the proper grammatical framework, communicating the feelings we have, and so on.
At one level though, speaking is producing movements: movements of the rib cage, the vocal cords, and the mouth. To make these movements, we must control the activity of about 100 muscles. One thing about stuttering is very clear: when disfluency occurs, the individual who stutters is not able to appropriately control the activity of the many muscles involved in speech. Why is it that some children do not develop the ability to control the activity of speech muscles, and this becomes a lifelong problem for the chronic stutterer?
At Purdue, we have been working on the answer to that question. Clearly we want to know what happens when the individual is disfluent. Many of our studies in adults who stutter have shown that muscle activity during stuttering is highly variable among different individuals, but highly consistent within a single individual over many different types of disfluencies. The only truly abnormal sign of muscle activity we have found during stuttering is tremor. This is an exaggerated rhythmic activity of muscles happening around 5 to 15 times per second. Sometimes you can see this tremor as a trembling of the lips when the individual is trying to speak.
Another important way to start to address the question we posed above is to look at young children when they are just starting to stutter. We now have a large project under way to do just that.
We will be studying speech coordination processes in groups of 4- to 5- year old children who are developing typically and children who are stuttering. We hope to follow them over a five-year period (at present we only have three years of funding for the project!) to see if early speech motor control characteristics during fluent and stuttered speech predict who will and will not develop a chronic stuttering problem. We look forward to keeping you informed about our progress!