WASHINGTON: Baby boys are more talkative than girls early on in life, according to a US scientific paper released last week that upends the common belief that females hold a language advantage over males in their early months.
The findings, published in “iScience” after the largest-ever study on the subject, came as a surprise even to the paper’s authors. They believe it might be the result of an important sex difference that emerged during the evolution of humans.
A team led by D Kimbrough Oller of the University of Memphis, Tennessee, used an algorithm to trawl through a data set of more than 450,000 hours of non-stop audio from 5,899 infants, recorded using an iPod-sized device over two years.
While young babies don’t talk, they produce pre-speech vocalisations – squeals, growls, raspberries, and later word-like sounds such as “ba” and “ga” – collectively called “protophones”, which eventually give way to real words and sentences.
The idea that girls acquire language faster than boys has long held sway in scientific circles, and with it the assumption that baby girls vocalise more than baby boys.
However, the results show that boys make 10% more utterances in the first year of life, before the girls catch up and make 7% more sounds by the second year. The differences occurred despite the fact that adult caregivers spoke more to girls than to boys across both years.
Evolutionary theory
One theory for the finding is that male infants are more vocal because they are more active in general. But the data does not support this, since higher male vocalisations gave way to females around the 16-month mark, but higher physical activity did not.
Instead, the team suggests their findings might fit an evolutionary theory which holds that infants make sounds to signal their wellbeing to their caregivers, who in turn invest more energy and attention in them.
Boys have higher mortality rates than girls in their first year of life, according to a broad body of research; as such, it may follow that baby boys in the distant past who were more vocal were more likely to survive and pass on their genes.
But by the second year of life, death rates dropped dramatically for both sexes, and “the pressure on special fitness signalling is lower for both boys and girls”, said Oller.
Next, Oller plans more research on how caregivers respond to baby talk.
“We anticipate that caregivers will show discernible reactions of interest and of being charmed by the speech-like sounds,” he said, “indicators that fitness-signaling by the baby elicits real feelings of fondness and willingness to invest in the wellbeing of infants.”