They found that while the adults and young children changed their vowel sounds in response to this altered feedback, the toddlers did not.
"We were very surprised to find that the two-year-olds do not monitor their own voice when speaking in the same way as adults do," said Ewen MacDonald, a former Queen's research associate and now associate professor at the Technical University of Denmark.
"As they play music, violinists will listen to the notes they produce to ensure they are in tune. If they aren't, they will adjust the position of their fingers to bring the notes back in tune. When we speak, we do something very similar. We subconsciously listen to vowel and consonant sounds in our speech to ensure we are producing them correctly," he explained.
The researchers have proven that toddlers use a different strategy to control speech than adults.
They still have not pinpointed the exact method children under two use when learning to control speech. Future studies are being developed to determine what strategy toddlers are using.
"Understanding the development of speech is a complex and challenging problem. Using novel techniques, such as the ones used in this experiment, we can isolate and better understand how the different components of speech develop," stated Dr MacDonald.
One possibility is that toddlers rely on the interaction with the person they are talking to in order to judge the accuracy of their speech sounds.
The research was recently published in Current Biology.