chimpanzees group on tree

Weekend Reads | Chimpanzee Chat: Studying the Language of Animals

by Kevin Schofield

This weekend’s read is a fascinating peek into researchers’ attempts to understand the language of animals — or, more precisely, whether some of the complexities of human language might also be present in animals.

We’ve known for some time that animal vocalizations can sometimes convey specific meaning: identifying food, danger, the desire to mate, or other important concepts for species to survive and thrive. There is also evidence that many animals can combine specific vocalizations one after the other, such as announcing a threat and recruiting others to help fight it. But what researchers have been unable to determine is whether animal language has syntax: Does combining vocalizations create a meaning that is unique and distinct from the meanings of the individual vocalizations? 

Human language experts have identified several different kinds of syntactic relationships between the words we use. Those include modification, such as “brown fox”; coordination, such as “human and dog”; and predication, such as “the wolf howled.”

A group of researchers from Switzerland, the Netherlands, and the United Kingdom paired up with a conservation field station in Uganda to look at whether chimpanzees in the wild use syntax in their vocalizations. Previously, researchers have identified several specific meaningful chimp vocalizations, including ”alarm-huus” when they are frightened or surprised, and “waa-barks” when they wish to recruit other chimpanzees to join them for some activity. They had also recorded that chimpanzees will combine alarm-huus and waa-barks in certain situations, most notably when they discover a snake. But the researchers didn’t know whether the combination of alarm-huu and waa-bark meant something different than just the two individual words said one after the other, i.e., whether the chimps were using syntax to communicate additional information. 

To try to resolve this question, the researchers gathered audio recordings of chimpanzees making three different noises: alarm-huus, waa-barks, and the combination of the two. To record the combination, they hid a fake snake in some bushes along a path and pushed it out into sight when a chimpanzee walked by.

With the audio recordings in hand, the researchers played each of them through a loudspeaker in a backpack (so they could move it around to different locations) and observed the behavior of chimpanzees that were close enough to hear the recordings. They noted whether the chimp turned in the direction of the loudspeaker, and whether it got up and moved in that direction. 

They found that playing an alarm-huu or a waa-bark alone generated a fairly low level of reaction, but the combination had a much stronger reaction in which the chimps often not only turned to look in the direction of the call but also got up and moved in that direction — essentially responding to a recruitment request. That led them to conclude that the combination vocalization has a unique meaning beyond just the two individual ones.

By the researchers’ own admission, though, this was a pretty rudimentary finding that left many important questions unanswered. They didn’t learn what kind of syntax might be involved: Was the vocalization communicating a modification, such as “There is an urgent danger”? Or was it perhaps a coordination, such as “There is a danger and I need help”? Or does the combination of vocalizations specifically mean “snake” to these chimps (researchers had noticed that they primarily use it in the presence of snakes)?

And while this research suggests using syntax in language is not unique to humans, it doesn’t tell us whether this is a case of “convergent evolution” where chimpanzees and humans independently evolved the same trait, or whether a common ancestor of chimps and humans used syntax and passed it down along both evolutionary lines. Our most recent common ancestor lived 45 million years ago; discovering that syntax existed in animal language that far back (if it could ever be proven, which is not at all clear) would dramatically change our understanding of brains, intelligence, and animal communication. But even if we can’t figure that out, it feels like the next few years are likely to bring a nearly endless supply of new revelations about animals’ ability to communicate.

Call combinations and compositional processing in wild chimpanzees

Kevin Schofield is a freelance writer and publishes Seattle Paper Trail. Previously he worked for Microsoft, published Seattle City Council Insight, co-hosted the “Seattle News, Views and Brews” podcast, and raised two daughters as a single dad. He serves on the Board of Directors of Woodland Park Zoo, where he also volunteers.

📸 Featured image by YC_Chee/

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