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Our closest living relatives could help us better understand how communication evolved in humans and how our own language skills emerge.
New research from our Department of Psychology found that young chimpanzees combine different gestures, vocalisations and facial expressions in a way which echoes the development of communication in human infants.
This ability develops in chimpanzees throughout infancy and adolescence.
Such combined signals included combining playful open-mouth faces with laughing, touching another chimpanzee while whimpering and baring their teeth while squeaking.
Understanding this "multimodal" form of communicating could shed important light on how communication evolved in humans and our closest ape relatives.
Communication signals
Previous studies involving apes have largely looked at different forms of communication signals in isolation.
These new findings looked at how chimpanzees combined these different forms of communication to see how this developed with age and in varying circumstances.
Our researchers observed 28 semi-wild chimpanzees, ranging in age from one to 11 years old, at the Chimfunshi Wildlife Orphanage Trust sanctuary in northern Zambia.
They found that chimpanzees consistently used standalone communication signals – such as grunting, arm movements or facial expressions – across all ages and in different situations.
But they also showed that as the chimpanzees got older, they were more likely to combine different communication signals together.
This was especially the case when the chimpanzees responded to aggression or were playing - two situations where it is important for them to make clear what they're communicating.
Older, adolescent chimpanzees were also more likely to use a combination of different communication signals instead of individual gestures or expressions, especially when showing aggression.
Observing multimodal signals in the wild
Our researchers said more work should be carried out to observe multimodal signals in primates in the wild to further understand how the development of communication is affected by different environments.
They added that studying multimodal communication – instead of observing individual communication signals in isolation – could provide better evidence of how communication develops in apes and potentially help us to understand the evolution of human communication.
