A study at the Universities of Zurich and Neuchâtel in Switzerland shows that, over the course of evolution, only humans have developed “baby talk” – a precursor to symbolic language (that has set humans apart from all other animal species).
Anyone who has ever spoken to an infant knows what it means to use baby talk – the way adults speak to babies, using simple phrases, a high-pitched voice, long vowel sounds and repeated words. Dubbed infant-directed speech by researchers, it has been the subject of analysis for years for its role in language development in children.
Now, thanks to a new international study coordinated by the Universities of Zurich and Neuchâtel, baby talk is back in the spotlight, making it onto the cover of the journal Science Advances.
Researchers (biologists and linguists), including from French and German universities, observed the use of “infant-directed speech” – to use the technical term – over a long time period in four species of great apes (bonobos, chimpanzees, gorillas and orangutans), as well as in humans. To do this, they meticulously recorded vocalisations that the young of great apes were exposed to in the wild. The researchers wanted to understand whether our “evolutionary cousins” use forms of vocal communication explicitly directed at their young.
The study’s findings show that humans are by far the most habitual users of baby talk. “We were surprised by how little of this type of communication we actually observed in our closest living relatives,” explained Franziska Wegdell, researcher at the University of Zurich and first author of the study. “By observing the adult-infant relationship, even in very short time intervals (2 minutes), we saw that the adult always made child-directed sounds, whereas other primates sometimes remained completely silent.” While this type of communication does also exist in a few other species, including cats, bats and dolphins, it has achieved an unparalleled level of sophistication and frequency in humans.
Learning is also by “osmosis”
So how do the young of great apes (and other animals) “enter” the communication system of adults without the help of baby talk? Language isn’t only learned through infant-directed phrases, write the Swiss researchers in Science Advances. And this applies to humans, too. “Human infants are able to learn new words from overhearing surrounding speech [by “osmosis”] from adults and from other children around them,” said Johanna Schick, co-author of the study. But, as we mentioned earlier, humans are the only ones to have developed a dedicated and consistent form of communication over the course of evolution, which probably had a decisive impact on language development.
Exaggerated vowels in 10 different languages
A second study came out recently, again on the subject of baby talk, but this time published by the scientific journal APA PsycNet. Researchers at the University of Tokyo in Japan, Aarhus University in Denmark and the University of Amsterdam in the Netherlands, conducted a meta-analysis of the results of 20 studies with homogeneous criteria performed in recent years by various international teams. They also looked at a further 35 studies that had, however, used different approaches. Specifically, the scientists measured the frequency of the vowels “a”, “i” and “u” in baby talk (because these sounds are easier to hear and may be vital for language acquisition). They found that mothers exaggerate these vowels in at least 10 different languages. This may well facilitate language acquisition at an early age, although the authors have pointed out that many studies are still too diverse in their methods to allow firm conclusions to be drawn.
However, what appears clear is that infant-directed speech isn’t just about instinctive tenderness: it’s a powerful evolutionary strategy. Not surprisingly, many scientists see baby talk as a crucial precursor to the emergence of symbolic language, which is what sets humans apart from all other animal species.
