Task-Specific Oral Diadochokinetic Timing Variability and Articulation Error Counts in Typically Developing Japanese Preschoolers

<ns5:p>Background Oral diadochokinetic tasks using/pa/, /ta/, and/ka/are often summarized as a single rate or timing-variability measure. If the three tasks do not behave coherently, however, a composite may obscure task-specific associations with speech-sound accuracy. Methods This cross-sectional observational analysis included 28 typically developing Japanese-speaking preschool children aged 55 to 78 months. Children completed monosyllabic oral diadochokinetic tasks and a standardized Japanese articulation assessment. Timing variability was quantified as the coefficient of variation (CV) of inter-peak intervals. Participant-level and task-level regression models examined associations with articulation error count, adjusting for age and site. Results The cross-task mean coefficient of variation was not detectably associated with articulation error count (coefficient = −0.001, p = .778). Inter-task correlations were negligible (r = −0.155 to −0.041). In task-specific models, /pa/timing variability showed evidence of a positive association with articulation error count (coefficient = 0.020, p = .009), whereas/ta/and/ka/did not show comparable evidence. A task-level interaction model was consistent with task-specific slopes, although the random-intercept mixed model produced a singular-fit warning. Conclusions In this small cross-sectional sample, aggregating timing variability across/pa/, /ta/, and/ka/may obscure task-specific patterns. The results support reporting oral diadochokinetic timing variability by task alongside rate as a hypothesis-generating measurement consideration, but they should be interpreted as exploratory and require replication in larger independent samples.</ns5:p>