Comparing Phonetic Complexity between Fluent and Disfluent Eojeols in Adults Who Stutter

Purpose: The purpose of this study was to investigate the characteristics of phonetic complexity in disfluent eojeols of adults who stutter. Therefore, phonetic complexity between fluent and disfluent [including stuttering-like disfluency (SLD) or other disfluency (OD)] eojeols was compared using two speaking tasks. Methods: Twenty-one adults who stutter performed a picture description task and a conversation task. Those speech samples were divided into eojeols, and each eojeol was classified as a “fluent eojeol” if it was perceptually fluent, an “OD eojeol” if it was produced with ODs, or an “SLD eojeol” if it was produced with SLDs. The index of phonetic complexity (IPC) and the phonological mean length of utterance (PMLU) were measured to compare phonetic complexity between the tasks and the types of eojeols. Results: The IPC was significantly the greatest in the SLD eojeol regardless of task. The IPC of the fluent eojeol was significantly greater than that of the OD eojeol. The SLD eojeol also showed significantly the greatest PMLU among the types of eojeols, and the fluent eojeol showed significantly greater PMLU than the OD eojeol. Significant positive correlations were found between IPCs and PMLUs for each eojeol no matter the task. Conclusion: When producing eojeols, greater phonetic complexity can trigger SLDs in adults who stutter, supporting the psycholinguistic aspects of stuttering.