Speech Development Between 30 and 119 Months in Typical Children III: Interaction Between Speaking Rate and Intelligibility.

Purpose: Earlier work has established developmental benchmarks for intelligibility and articulation rate, but the intersection of these two variables, especially within individual children, has received limited attention. This study examines the interaction between intelligibility and speaking rate in typically developing children between the ages 2;6 and 9;11 (years;months) and evaluates whether children show a speed-accuracy trade-off in their habitual speech production.

Method: Speech samples of varying lengths were collected from 538 typically developing children. Intelligibility was measured as the number of words correctly transcribed by untrained adult listeners, and speaking rate was calculated in number of syllables per second. Regression models estimated the effects of age, utterance length, and speaking rate on intelligibility.

Results: Intelligibility and speaking rate were positively correlated overall but weakly correlated after adjusting for age. In regression analyses, intelligibility increased with age and decreased with utterance length, and there was a trend for intelligibility to decrease with increased speaking rate, especially in longer utterances. At the individual level, for most children, there was a negative effect of speaking rate on intelligibility.

Conclusions: Our findings provide evidence from a large-scale sample for the hypothesis that children's speech is subject to a speed-accuracy trade-off where increased speaking rate leads to reduced articulatory accuracy and hence reduced intelligibility. Further research is needed on how to apply this trade-off in a clinical setting.

Supplemental material: https://doi.org/10.23641/asha.27964125.