Dysrhythmic Speech Is a Characteristic of Developmental Stuttering in Adults: A Quantitative Analysis Using Duration- and Interval-Based Rhythm Metrics.

Purpose: Aberrant speech rhythm has previously been identified as a hallmark of stuttering. However, evidence of dysrhythmic speech in adults who stutter (AWS) has largely been limited to qualitative research. Here, we conduct a quantitative analysis of speech rhythm in AWS and adults who do not stutter (AWNS). We also investigate potential differences in speech rhythm as a likely marker of articulatory stability in speech preceding moments of stuttering-like disfluency versus not preceding moments of stuttering-like disfluency. We hope to establish rhythm of speech as a supplementary diagnostic criterion for the assessment of stuttering.

Method: Rhythm metrics were computed for speech produced by 16 self-identified AWS and 16 AWNS. Speech was recorded in reading and spontaneous speaking tasks. Following previous literature, we hypothesized that the nonstuttered utterances of AWS would be less rhythmic than those of AWNS. Furthermore, it was expected that speech rhythm would be disrupted immediately preceding the production of stuttering-like disfluency in AWS. We conducted statistical tests to determine differences in speech rhythm metrics between participant groups (i.e., AWS and AWNS) and utterance types (i.e., preceding stuttering-like disfluency and not preceding stuttering-like disfluency).

Results: Multiple metrics revealed reduced speech rhythmicity in AWS compared to AWNS for both nonstuttered oral reading and spontaneous speech tasks. Furthermore, speech rhythmicity in AWS was significantly reduced immediately preceding stuttering-like disfluency compared to not preceding stuttering-like disfluency in both the reading and spontaneous speech tasks.

Conclusions: We present quantitative evidence of reduced speech rhythm as a characteristic of developmental stuttering. AWS exhibited relatively less rhythmic speech overall and particularly immediately preceding a stuttering-like disfluency. This reduction in the temporal stability of speech may be interpreted as a sign of imminent breakdown in articulatory coordination. The potential significance of rhythm metrics to speech science and clinical diagnostics is discussed.