Characteristics of Fluency and Speech in Two Families With High Incidences of Stuttering

This study presents data from 2 families with high incidence of stuttering, comparing methods of phenotype assignment and exploring the presence of other fluency disorders and corresponding speech characteristics.

Three methods for assigning phenotype of stuttering were used: self-identification, family identification, and expert identification. Agreement on which individuals were assigned by each of these methods was studied. Multiple measures of fluency and speech production were obtained.

Self-reports and descriptions of blocking rather than self-identification as a person who stutters demonstrated the best agreement with expert identification of stuttering. Family identification showed poor agreement with both expert and self-identification of stuttering. Using binary categories of fluent or stuttering, 90% of individuals in 1 family were classified by expert consensus. Only 70% of the other family could be similarly categorized. Experts required 2 other categories, cluttering and other fluency disorders, to fully characterize dysfluency within this family. These 2 families also demonstrated differences in speech production.

Some families with high incidence of stuttering may also have high incidence of other fluency disorders and other speech-production difficulties. This finding may have ramifications for genetic studies, including criteria for defining phenotype and collapsing data across multiple families.