Development of Voluntary Speech Rate Control in Japanese Young Children

—Comparison with Voice Loudness Control—

Abstract

The purpose of the present study was to investigate 1) the development of voluntary speech rate control, and 2) whether it differs from the development of voice loudness control. The participants were 81 typically developing children aged 3 to 6. They were shown a picture of an animation character and given instructions to say the name of the character. Two types of instruction —“speak slowly” and “speak fast”— were used in the speech rate control task, and two types of instruction —“speak in a loud voice” and “speak in a small voice”— were used in the voice loudness task. In the speech rate control task, the percentages of children who could control their speech rate were 10.0% and 14.3% at ages 3 and 4, and 63.6% and 88.9% at ages 5 and 6, respectively. In the voice loudness control task, the rates were 35.0% and 61.9% at ages 3 and 4, and 77.3% and 94.4% at ages 5 and 6, respectively. These results suggest that voluntary control of speech rate is more difficult than that of voice loudness at ages 3 and 4. They also indicate that the ability to voluntarily control speech rate develops abruptly from age 4 to 5, and almost all children can control both their speech rate and voice loudness at age 6.