Toddlers understand sound they make influences others, research shows

The findings are published in the Journal of Cognition and Development.

There has been limited research on what children understand about what others hear, with previous studies focusing only on whether a sound could be heard. This study takes a new approach to learning what children understand about sound by introducing a new variable -- the loudness of a sound. The study examined whether toddlers understand that the type of sound they produce may influence a social situation, such as waking and sleeping.

There were 48 children, ages 2 to 3 years old, in the study. They had a chance to play with two toys, a quiet toy and a loud toy. A researcher then introduced a doll and gave the children one of two goals, either to wake up the doll or let the doll sleep. Then, the children got to play with the original toys again. They were not given direct instructions on how to behave, such as whether to be quiet or make noise.

The researchers wanted to know if children would change their play based on what they knew. For instance, if children understand that noise affects others, they should make loud noises for the waking goal and purposely make quieter noises for the sleeping goal. The research team also wanted to know if having siblings influenced children's performance on these tasks.

They found that children, particularly those with siblings, understand the behavioral and psychological effects of different types of sound.

"We were excited to see that young children tried to wake the baby with loud sounds. They also played quietly to let the baby sleep," said Dr. Rebecca Williamson, assistant professor of psychology at Georgia State.

Children who were told to wake the doll produced louder sounds, while children who were told not to wake the doll produced quieter sounds. In addition, children who were told to wake the doll significantly more often chose to play with the loud toy first.