Birds shown to follow grammar

April 27, 2006|By RONALD KOTULAK | RONALD KOTULAK,CHICAGO TRIBUNE

CHICAGO -- Scientists are running out of things they think truly separate humans from other animals. For a long time the reigning difference was thought to be tool-making, but then they discovered that chimpanzees and gorillas use tools.

One of the last bastions of human uniqueness, they surely thought, is language. Although animals can communicate, it was thought to be in only a fixed way - using sequences of sounds with specific meanings that never vary.

Humans supposedly were different because they can follow rules of grammar. For example, people can interrupt a sequence of sounds to add new ones, altering the meaning and allowing an infinite variety of expression. The sentence "my dog has fleas" can change to "my dog, who answers to the name of Murray and has a black, shiny coat, has fleas."

Well, guess what. European starlings can do that, too, according to a report in yesterday's issue of the journal Nature by researchers from the University of Chicago and the University of California, San Diego.

Starlings, of course, don't speak to one another as humans do, although they can mimic human speech. But they can apparently recognize the grammatical concept of adding sounds to produce a more complex song.

Such songs appear to be more compelling to female starlings. The birds also use their complicated songs to identify one another.

"Here's a form of pattern recognition that we all agree has to be there if you're going to recognize human languages, and birds can do it," said lead author Timothy Gentner, a former University of Chicago graduate student who is a psychologist at UC, San Diego.

Linguists such as MIT's Noam Chomsky have held that inserting words into simple sentences - a rule of grammar called center-embedding or recursive syntax pattern learning - is a universal characteristic of languages and defines "the boundaries between humans and other creatures."

But the study persuasively shows that humans are not the only species to exploit the center-embedding rules of grammar, New York University neuroscientist Gary Marcus wrote in an accompanying Nature commentary.

"There's long been a temptation to sum up the differences between humans and other species in a neat turn of phrase, but most posited differences have ultimately proven to be overstated," he said.

Scientists knew birds could remember a straight sequence of sounds that are added on. Using two typical starling sounds, such a sequence might go like this: "warble, rattle, warble, rattle."

The study found that starlings, which were trained to peck a button for a food treat when they made the correct response, were able to distinguish such sequences from more complex center-embedding patterns, such as "warble, warble, warble, rattle, rattle, rattle."

After 10,000 to 50,000 trials, the birds learned to recognize similar patterns in previously unheard strings of sounds, meaning they were using grammatical rules to solve the task.

"We don't claim that starlings are talking to each other the way humans do," said University of Chicago neurobiologist and study co-author Daniel Margoliash. Howard Nusbaum, chief of psychology at the University of Chicago, is the senior author.

"We understand that language is remarkable and unique," Margoliash said. "But we now have a good animal model for the first time to investigate language at a neurophysiological and neurobiological level."

Mark Spreyer, a starling expert and director of the Alexander Stillman Nature Center in South Barrington, Ill., said he is not surprised that starlings can recognize complex rules of grammar.

"Our intelligence tests for birds were from a mammalian point of view," he said. "We were trying to run IBM software on a Mac. Now that we're getting a better handle on how to test for bird intelligence, some of these discoveries won't sound as shocking as they might have 10 years ago."

Spreyer said a starling he had as a pet learned to mimic his voice on the telephone answering machine. "Hello, this is Mark Spreyer," the starling, named Rod, would say. Then he would beep.

Starlings are great mimickers. The story is told of Mozart whistling one of his unpublished tunes in a pet store, only to hear it repeated by a starling, which he happily bought.

Shakespeare, knowing the bird's talent for mimicry, had one of his characters, a disgruntled nobleman who was forbidden to speak the name of a rival in the presence of the king, teach a starling "to speak nothing but `Mortimer,' and give it him [the king] to keep his anger still in motion."

That single reference led to the release of about 100 starlings in New York's Central Park in the 1890s - someone thought it was a good idea to introduce all the bird species mentioned by Shakespeare. An estimated 200 million starlings now live in North America.

Ronald Kotulak writes for the Chicago Tribune.

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