Early Speech Rate Development: A Longitudinal Study

Purpose: Our knowledge of speech rate development remains inadequate because of limited longitudinal data and lack of data from children under age 3;0 (years;months). The purpose of this longitudinal study was to test the pattern of speech rate development between ages 2;0 and 3;0. Method: Speech rate was assessed at 4 time points between ages 2;0 and 3;0. The analysis employed multilevel models to characterize the development of speech rate (syllables per second), phonemes per second (PPS), length of active declarative sentences, and mean length of utterance. Results: The results indicate a significant linear increase in speech rate, PPS, length of active declarative sentences, and mean length of utterance occurring over the 1-year period. Male and female children differed in speech rate, PPS, and utterance length, suggesting sex is a potential factor in early speech rate development. Conclusions: Our findings indicate that the speech motor system develops rapidly during the period when grammar emerges. Speech rate has the potential to be an important metric for understanding typical speech development and speech disorders.