News in Science

Toddlers don't listen to themselves talk

Baby talk Toddlers may babble away to themselves for hours, but they may not be able to rely on these sounds to develop their language skills.

A new study published in today's issue of the journal Current Biology has found that toddlers do not listen to their own voice in the same way that adults and older children do.

"[Adults] subconsciously listen to vowel and consonant sounds in our speech to ensure we are producing them correctly," says study lead author Ewen MacDonald from the Technical University of Denmark.

"If the acoustics of our speech are slightly different from what we intended, then … we will adjust the way we speak to correct for these slight errors," MacDonald says.

But unlike adults and older children, two-year-olds don't monitor the sound of their own voice to correct errors, the study found.

This is despite the fact that toddlers can readily detect small deviations in others' pronunciation of familiar words, babble in a manner that is consistent with their native language, and are well on their way to acquiring vocabulary and sound structures.

Bed, bad, bid

MacDonald and colleagues compared the language abilities of adults, four-year-olds and two-year-olds. Each group was asked to say the word 'bed' fifty times. To elicit this word from the younger children and toddlers, the researchers used a virtual game where the children had to help a robot cross a playground by saying the word 'bed'.

After the participants had heard themselves say the word 'bed' twenty times, the researchers tweaked the auditory feedback so that they heard themselves say the word 'bad' instead of 'bed'.

"If they repeat this several times, adults spontaneously compensate, changing the way they say the vowel," says MacDonald. "Instead of saying the word 'bed' they say something more like the word 'bid'."

The research showed that four-year-olds also adjusted their speech, but two-year-olds continued to say the word 'bed'.

So, if toddlers do not automatically monitor their own speech productions for accuracy as adults and young children do, how do they learn to produce the sounds used in their language community?

MacDonald says the results suggest that two-year-olds may depend on their parents or other people to monitor their speech instead of relying on their own voice.

"Caregivers often do repeat or reflect back to young children what they've heard them say," he notes.

Speech perception

While there have been many studies in the past that have looked at an infant's ability to hear, this study offers a new insight into how young children perceive their speech, says speech pathologist Professor Sharynne McLeod, an ARC Future Fellow from Charles Sturt University in Bathurst.

"This study offers interesting insights into the child's ability to perceive [speech] because the four-year-olds were showing quite clear patterns but the two-year-olds were not," says McLeod, who was not involved in the research.

But McLeod says the difference in speech patterns may not only be linked to the two-year-olds' ability to perceive their own production.

"There may be a whole range of reasons why the toddlers are having difficulty, for example, their motor planning skills and their ability to produce speech is still developing at that stage," she says.

She also notes that the vowel sounds 'a' and 'e' tested in the study are very similar and change across dialects.

"I think that you would need more studies to generalise [the findings], but one of the take-home messages is that there is a lot of research that shows that when children say a word it's good to repeat that word back to them in a sentence and help expand their language development."

She says the study also highlights the importance of early intervention by speech pathologists and newborn hearing assessments.

"Children are still developing between two and four so if we can identify markers when they're young, we can facilitate their development because that perception, storage, output linkage is so crucial in children's, and all of our ability, to speak."

Speech Pathology Australia has a fact sheet that outlines speech milestones for toddlers and young children.