Baby talk is an almost universal phenomenon we use to communicate with babies, but researchers don’t understand how this trait evolved. Now, a study published in Science Advances shows that humans are the only species to use baby talk, while other great apes use different forms to teach their young to communicate.
Numerous studies show that baby talk leads to better learning outcomes, including a bigger vocabulary size and better literacy skills. This practice facilitates language acquisition, but how did it evolve?
To answer this question, a team of researchers from the University of Zurich (UZH) and the University of Neuchâtel (UNINE), members of the NCCR Evolving Language, and colleagues from universities in France, Germany and the US, observed the use of “infant-directed vocal communication” among five species of great apes: humans, bonobos, chimpanzees, gorillas and orangutans. The team recorded the vocalizations to which great ape infants were exposed to in the wild.
Their results show that humans are the most frequent “baby-talk” users. “We were surprised by how little of this type of communication we actually observed in our closest living relatives,” explained Franziska Wegdell, a UZH postdoc.
The question now is how non-human great ape infants learn their communication system? The reality is that even human infants use other ways to learn language. “We know that human infants are able to learn new words from overhearing surrounding speech from adults and from other children around them,” said Johanna Schick, another UZH postdoc.
When comparing communication around infants across the five great ape species, all were exposed to similar levels (even though using different methods), except for orangutans. It may be that, like humans, great apes also learn their communication system socially, but in their case, it’s indirectly through hearing surrounding communication rather than through direct baby talk.
For this study, the researchers focused only on infant-directed vocal communication, not other forms of communication. “Since speech is a primary modality of language, we chose to begin our research by focusing on the vocal domain,” said Caroline Fryns from UNINE. “But we know that non-human great apes direct gestures at their infants, and that some of these gestures even exhibit features also found in human infant-directed communication.”
The ideal way to study the evolution of language would be to assess the language capacities of early humans. However, this is impossible. “For this reason, we turned our attention to our closest living relatives – non-human great apes – investigating their infant-directed vocal communication,” explained Franziska Wegdell.
This study seems to suggest that the use of direct vocalizations with infants — baby talk — is just part of the human lineage. Although baby talk is only found in low levels in our great ape relatives, other species – including some monkeys, bats, cats, or dolphins – use direct vocalizations with their young. “To shed further light on the evolution of infant-directed communication, future work could compare how the characteristics and functions of this type of communication vary across species and why,” concluded the researchers.
Franziska Wegdell et al., The evolution of infant-directed communication: Comparing vocal input across all great apes.Sci. Adv.11,eadt7718(2025).DOI:10.1126/sciadv.adt7718