It may sound like a stream of jolly nonsense, but the peculiar sounds babies produce may be an attempt to practice the vocal control necessary for speech, researchers have suggested.
A study that analyzed the sounds babies make during their first year of life found that screams and grunts tend to occur in groups.
Dr. Hyunjoo Yoo, the first author of the research from the University of Alabama, said the work could have important implications. “One of the primary reasons for our pursuit of the issue of clustering is that it may be a useful marker in screening for communication disorders,” she said.
Dr Ed Donnellan of the University of Warwick, who was not involved in the research, said the study confirmed that babies deliberately play with the vocal sounds they can make, producing certain types of vocalizations in groups at will.
“Even if the sounds looked at – squeals and grunts – are not necessarily the ones we use in language, this play may allow babies to develop their control over the sounds they make, which is essential for later spoken language,” he added.
Write in the journal Plos OneYoo and colleagues report how they studied 130 infants through surveys taken at home by their caregivers every month from birth.
The team randomly selected 21 five-minute segments from each recording and analyzed them for the presence of screams, grunts and vocal sounds known as vocants.
After excluding cases where, for example, the baby was sleeping, the team was left with 15,774 segments from 1,104 recordings, with more than 60% of the recordings showing clustering of either screams or grunts in relation to vocants.
“There was not a single infant that, after evaluating all the available recordings for the infant, did not show a significant case of squeal clustering or of growl clustering,” the team adds.
Clustering was seen across all six age groups, from birth to 13 months, which they suggest suggests that some mechanism of vocal exploration is present from the beginning of life. However, the age range of 3 to 4 months showed the lowest mean values for pee and grunt grouping, an unexpected finding given this period is traditionally associated with the onset of vocal play.
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The team say it was also surprising that, in contrast to the grouping of grunts, higher proportions of squeal grouping were found after the age of five months – something the researchers suggest may be due to the development of control over the vocal cords.
Yoo added that previous reports have suggested that by imitating such sounds, caregivers can help expand infants’ vocal repertoires and proto-conversations.
“So it seems logical that it would be beneficial for babies if caregivers try to respond casually and interact more with their babies by imitating screams, voices and grunts,” she said.
