Karl Berg, a behavioral ecologist and parrot expert at the University of Texas Rio Grande Valley in Brownsville, has published a major study in the prestigious scientific journal Proceedings of the Royal Society B, and it’s getting attention from a number of other scientific journals and media outlets internationally.
The Canadian Broadcasting Corporation, Forbes, Times of London, Psychology Today and Science magazine are among the publications that have interviewed Berg about the study, which contains two important findings from his research into vocal babbling in parrotlet nestlings in Venezuela.
Parrotlets are a tiny, adorable species of parrot.
Human babies normally start babbling — goo-goo-ga-ga and so on — at about six months. Berg has discovered the same thing going on with baby parrotlets: increasingly complex babbling as the nestlings develop toward maturity. The new study is based on his many years of research (plus another 50 years of parrot research in general), which may help shine a light on how human language evolves from babbling, he said.
“The big one was simply finding babbling phase to development that’s been taken pretty seriously in humans but also in songbirds and pygmy marmosets, a small rainforest monkey, bottlenose dolphins, a species of rainforest bat,” Berg said.
“Just identifying another lineage that has this is important because it broadens our evolutionary perspective on why we have this language ability, … what some scientists consider the biggest question in science, because none of science would exist if we didn’t have our language abilities.”
Parrots are considered the most complex of vocal imitators among the other-than-human world, making it all the more important to understand why this particular group of birds comes closer to human language than any other, he said. As anyone who’s ever had a parrot as a pet knows, they’re socially complex and extraordinarily intelligent animals, even if historically that intelligence has been underestimated, Berg said.
A huge scientific mystery is how babbling works as the precursor to language in humans, while the level of complexity in an infant’s babbling seems to be a reliable indicator of later cognitive function, he said. Also, if babbling is significantly delayed — at 10 months rather than 6 for example — there’s a good chance the child will later develop autism, Berg said. These are important things to know since autism normally isn’t diagnosed until around age 2, he said.
“There’s a lot of interest in understanding what’s going on there,” Berg said. “People have switched to animals to try and understand it better.”
Songbirds have been an excellent model for studying the phenomenon due to their sophisticated ability to imitate sounds, and because they can be studied in captivity, he said. But while songbirds, at least male songbirds, start singing only when they reach sexual maturity, to attract a mate, parrotlets begin vocalizing (babbling) in the nest, and it’s the females as well as the males doing it, Berg said.
This is where the second major finding of the study comes in, one he concedes is difficult to explain even to an academic audience. It involves the endocrine system and the hormones that are calling the shots in terms of what the body is doing at any given moment: experiencing a growth spurt, sexually reproducing, responding to injury, being hungry and so on.
Testosterone and estrogen are the commonly known sex hormones, though that’s not all they are, and there are other hormones as well, the so-called stress hormones, which Berg says is an unfortunate name because of the negative connotation of the word “stress.” What they really are is “staying alive” hormones, he said.
The endocrine system is a loop system connected to the brain and other parts of the body. It tells the body what to do in part based on sensory input from outside the body — one’s environment. If you’re being chased by a lion, for instance, stress hormones direct glucose into the bloodstream to allow the muscles to run as fast as possible, Berg said. When you feel hungry, those are stress hormones ordering the body into food-finding mode, he said.
“When you get hunger pangs, that hormone is kicking in, and you either go to the refrigerator or you have another cup of coffee and don’t worry about it, or you go fishing,” Berg said.
The harder-to-explain part of the study deals with how stress hormones function in the development of parrotlet nestlings, which Berg and his research team in Venezuela — including his wife and research associate Soraya Delgado — have been able to observe thanks to artificial nesting tubes outfitted with video cameras.
“When we saw babbling was occurring in the nest, stress hormones came to mind,” he said.
Unlike male songbirds, which sing at maturity because sex hormones tell them to, the evidence appears to show that the male and female baby parrots are babbling because of the influence of stress hormones. Berg also discovered that administering a small dose of stress hormone to the nestlings each day for a week resulted in more sophisticated babbling, he said.
“We found that the stress hormone actually increased the babbling repertoire,” Berg said. “It’s a little soon to say it’s beneficial, but it certainly doesn’t look bad. … I think it shows that according to our predictions we were right, that this part of the endocrine system is playing a potentially beneficial role in language development. It’s suspected in humans, but there’s no hard experimental evidence.”
Injecting human babies with stress hormone to see how it affects babbling and language development is a non-starter ethically speaking, he said. As a result, any evidence that the stress-hormone part of the endocrine system plays a role in human language learning remains strictly circumstantial, Berg said.
At the same time, the study succeeds in highlighting what “appears to be a major difference between parrots and songbirds,” he said. Berg has also observed babbling in baby red-crowned parrots, whose small range includes the Rio Grande Valley. While it doesn’t prove that babbling exists across other parrot species, it seems likely that it does in fact occur, he said.
“To a lot of people in the animal world, that’s pretty important, if you figure something like that out,” Berg said. “We’ve shown the world something about how these two important groups of birds differ. We’ve known for a long time that they do differ. Why? Getting to the early development questions and so forth brings us closer to understanding why the two groups are different, and again, we’ve known that parrots have a lot of similarities with humans that they don’t really share with songbirds.”
