New research has proven what many parents have always suspected about their children. Research from both Georgia State University and the University of Washington have concluded that toddlers understand the sounds they make affect people around them.

The study had 48 children aged 2 to 3 years-old play with two toys, one loud and one quiet. Researchers then introduced each child to a doll and told the child they were to either “wake up” the doll or “let the doll sleep.” The children were then able to play with their original toys, but were not instructed on how to behave.

Toddlers that were told to wake the doll made louder noises while children told to let the doll sleep made quieter sounds. Those with siblings especially understood the differences between loud and quiet.