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From: Ken St. Louis
Date: 06 Oct 2011
Time: 11:17:10 -0500
Remote Name: 157.182.15.31
Richard, These are good questions. Let me take a stab at them. As for the distribution of severity, it all depends on the group of stutterers you look at. Most studies have looked at clinical and research populations, that is individuals who come for evaluations and therapy or are recruited to participate in research projects. These are included in--but are not the same as--those in the 1% prevalence figure you cite. Only a tiny fraction of those ever see the inside of a clinic or a laboratory. So, if we take the clinical/research population, Soderberg (1962) summarized stuttering frequency in oral reading of 105 adult stutterers from four master's theses at Western Michigan University and Ohio State University. I wish I could paste in his histogram, but I can't. Here are the figures. With 200-word passages and therefore 200 possible stutters per individual, 51 (or about half) had 0-16 stutters, 18 had 16-32 stutters, 13 had 32-48 stutters, 13 had 48-64 stutters, 3 had 64-80 stutters, 3 had 80-96 stutters, 3 had 96-112 stutters, 0 had 112-128 stutters, 0 had 128-144 stutters, and 1 had 144-160 stutters. What this set of numbers virtually screams out is that, during reading, adults who stutter don't stutter very much. The histogram is highly negatively skewed toward the mild side. In the clinical/research population, the large majority of stutterers are likely mild, moderates account maybe for the majority of the rest of them, while severe stutterers are rare. In a different vein, I have been having my students interview people who stutter (or used to stutter) for years, and I have kept a summary impression sheet for each of them. These individuals were usually found through queries from family and close friends "back home." As such, they are mixture of clinical/research AND the "other" population of stutterers. Here's a "quick and dirty" snapshot of those (nonverified!) impressions of severity for 256 adults who stuttered at some time in their lives: No stuttering--14%, very mild--37%, mild/moderate--9%, moderate--9%, moderate/severe--7%, severe--4%, very severe--1%. It gives the same impression as Soderberg's report, but even showing much less moderate and severe stuttering. As for prevalence, probably the best study around was the National Speech and Hearing Survey done in 1968-69 by Colorado State University. I worked on that study as an examiner for one year. Six teams went to 100 randomly selected school districts around the country testing 39,000 randomly selected children from grades 1-12. There were no questions about whether or not one stuttered. Subjects were scored as stuttering if they actually stuttered during a 10-minute speech/voice/language sample. There were many more stutterers in the early grades than in later grades, but the overall prevalence rate was 0.8%. Since we did not ask about stuttering, and since many stutterers can speak in a screening situation like that without stuttering, it is likely that the estimate is lower than the actual prevalence rate. The conventional wisdom is that, of the TOTAL population of stutterers (clinical/research/other), 5% will stutter sometime in their lives (known as "lifetime incidence'), usually during preschool years and early elementary years. About 80% of them will recover spontaneously, leaving about 1% who will stutter chronically. That is the figure that most prevalence studies will approximate. I hope this figure-filled answer deals with what you wanted to know. Best, Ken