The Assessment of Possible Cluttering in Japanese Adults Who Stutter: Analyzing the Ratio of Disfluencies

Abstract

Purpose In this study, we investigated the classification of cluttering by assessing speech based on the ratio of disfluencies (RDF) and attempted to identify cluttering and cluttering–stuttering by classifying disfluencies according to previous studies and the Japanese Standardized Test for Stuttering. We further investigated the factors that contribute to the occurrence of disfluency by comparing the disfluencies of three tasks (spontaneous speech, oral reading, and retelling a memorized story) and examining the relationship between RDF and speech rate. Method The participants comprised 20 Japanese adults who stutter. Participants were required to perform an oral reading task, retelling a memorized story task, and a spontaneous speech task. We subsequently classified their disfluencies and calculated the RDF (normal disfluencies that are often observed in cluttering/stuttering-like disfluencies). Results About half of the participants met the cluttering criteria, that is, an RDF of above 3. Analyzing speech disfluencies revealed that a high RDF is associated with fewer stuttering-like disfluencies that increase the denominator of the RDF formula or many “interjections” that make its numerator smaller. Conclusions These tendencies of speech disfluencies could influence cluttering identification. We should further utilize the RDF considering the findings of this study.