Temporal patterns in articulation underlying repetitions, prolongations and blocks

Repetitions, prolongations, and blocks, as canonical categories of stuttering disfluencies, have long been characterized on auditory-perceptual grounds, while the articulatory behaviors giving rise to them remain poorly understood. This study investigates the articulatory basis of these disfluencies, and assesses how the underlying articulatory patterns relate to perceptual disfluency types (i.e., repetitions, prolongations, blocks) and the phonological features of stuttered segments.

Speech production of seven adults who stutter was recorded using real-time MRI. We extracted the time-varying constriction trajectories of the primary oral articulator for stuttered tokens of labial, alveolar, and velar consonants, as well as the constriction trajectories of the velum. K-medoids clustering with dynamic time warping distance was used to identify recurrent patterns.

Two constriction patterns of the primary oral articulator were observed consistently across participants: fixation, characterized by an extended constriction period, and oscillation, characterized by repeated constriction-release cycles. Velic constriction trajectories did not show stuttering-related patterns but simply reflected the nasality of the stuttered segment. The mapping between articulatory constriction patterns and perceptual disfluency types was many-to-one and one-to-many. Crucially, this mapping was influenced by the manner of the stuttered segment.

State stuttering is characterized by two stable articulatory patterns: fixation and oscillation of the primary oral articulator. Their mappings to perceptual disfluency types are not in a simple one-to-one correspondence and also depend on the phonological task being executed. These findings point to a principled organization in the articulation of stuttering, enriching our understanding of the phenomenon beyond its perceptual surface.