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In our search for what makes humans unique, we often compare ourselves to our closest relatives: the great apes. But when it comes to understanding the essential human language ability, scientists are discovering that the most tantalizing clues lie further afield.
Human language is made possible by an impressive aptitude for vocal learning. Babies hear sounds and words, form memories of them and try to produce those sounds later, improving with age. Most animals cannot learn to imitate sounds at all. While non-human primates can learn how to use innate vocalizations in new ways, they don’t show a comparable ability to learn new calls. Interestingly, a small number of more distant mammal species, including dolphins and bats, have this capacity. But under the scattering of non-human vocal pupils over the branches of the bush of life, the most impressive birds – hands (wings?) are down.
Parrots, songbirds, and hummingbirds all learn new vocalizations. The calls and songs of some species in these groups seem to have even more in common with human language, such as the deliberate transmission of information and the use of simple forms of some elements of human language, such as phonology, semantics and syntax. And the similarities run deeper, including analogous brain structures not shared by species without vocal learning.
These parallels have sparked an explosion of research in recent decades, says Columbia University ethologist Julia Hyland Bruno, who studies the social aspects of song learning in zebra finches. “A lot of people have made analogies between language and birdsong,” she says.
Hyland Bruno studies zebra finches because they are more sociable than most migratory birds – they like to travel in small groups that occasionally gather in larger groups. “I’m interested in why they learn their culturally transmitted vocalizations in these groups,” said Hyland Bruno, co-author of an article in the 2021 Annual Review of Linguistics comparing bird and culture learning to human language. .
Both birdsong and language are culturally passed on to later generations through vocal learning. Geographically distant populations of the same bird species can make minor adjustments to their songs over time, ultimately resulting in a new dialect — a process that is in some ways similar to how humans develop different accents, dialects, and languages.
With all these similarities in mind, it’s reasonable to ask whether birds themselves have language. It may depend on how you define it.
“I wouldn’t say they have language as linguistic experts define it,” says neuroscientist Erich Jarvis of Rockefeller University in New York City and a co-author of Hyland Bruno’s paper on birdsong and language. But for scientists like Jarvis who study the neurobiology of vocal communication in birds, “I’d say they’re a remnant or rudimentary form of what we might call spoken language.
“It’s like the word ‘love’. You ask a lot of people what it means, and you get a lot of different meanings. Which means it’s partly a mystery.”
There are multiple components in spoken language, Jarvis says, and some are shared by more species than others. A fairly common part is auditory learning, such as a dog figuring out how to respond to the spoken command “sit.” The vocal learning that humans and some birds do is one of the most specialized components, but they’re all shared to some degree by other animals, he says.
The grammar of bird sounds
An important element of human language is semantics, the connection of words with meanings. Scientists long believed that, contrary to our words, the sound of animals was involuntary and reflected the emotional state of the animal without conveying any other information. But over the past four decades, numerous studies have shown that different animals have different call signs with specific meanings.
Many bird species use different alarm calls for different predators. Japanese tits, which nest in tree hollows, have one call that causes their chicks to crouch to avoid being pulled from the nest by crows, and another call for tree snakes that causes the chicks to jump completely out of the nest. Siberian jays vary in their calls depending on whether a predatory hawk is seen looking for prey or actively attacking – and each call elicits a different response from other nearby jays. And black-hooded tits change the number of “dees” in their characteristic call to indicate relative size and threat from predators.
