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Are birds' tweets grammatical?

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Are humans the only species with enough smarts to craft a language? Most of us believe that we are. Although many animals have their own form of communication, none has the depth or versatility heard in human speech. We are able to express almost anything on our mind by uttering a few sounds in a particular order. Human language has a flexibility and complexity that seems to be universally shared across cultures and, in turn, contributes to the variation and richness we find among human cultures.

But are the rules of grammar unique to human language? Perhaps not, according to a recent study, which showed that songbirds may also communicate using a sophisticated grammar—a feature absent in even our closest relatives, the nonhuman primates.

Kentaro Abe and Dai Watanabe of Kyoto University performed a series of experiments to determine whether Bengalese finches expect the notes of their tunes to follow a certain order. To test this possibility, Abe and Watanabe took advantage of a behavioral response called habituation, where animals zone-out when exposed to the same stimulus over and over again.

In each experiment, the birds were presented with the same songs until they became familiarized with the tune. The researchers then created novel songs by shuffling the notes around. But not every new song caught the birds’ attention; rather, the finches increased response calls only to songs with notes arranged in a particular order, suggesting that the birds used common rules when forming the syntax of that song. When the researchers created novel songs with even more complicated artificial grammar—for example, songs that mimicked a specific feature found in human (Japanese) language—the birds still only responded to songs that followed the rules.

Because the birds responded strongly to tunes ordered with certain structure, even when this structure was artificially constructed, the research team determined that the finches were able to spontaneously learn new grammar. This ability, though, seemed to be dependent upon their social context.

Birds isolated as babies from other birds were still able to learn artificial rules of grammar, but they failed to respond to songs with modified syntax—that is, normal Bengalese finch songs with the notes shuffled. However, after being reintroduced to other birds, it took them only two weeks to learn to respond to the shuffled songs, indicating that the birds needed to hear other birds’ songs to absorb the precise rules of Bengalese finch grammar.

While birdsong has long been known to share similarities with human language, the ability to convey different bits of information by simply rearranging word order was thought to be exclusively human.

This study revealed that Bengalese finches can learn grammar and, furthermore, that their grammatical abilities involve a specific part of the brain region distinct from other brain regions involved in singing. This is similar to what neuroscientists understand about human language processing.

If the tweets of birds can be roughly likened to strings of human words, and if birdbrains process songs in a way similar to how human brains process language, future research may tackle whether these animals possess other cognitive abilities once thought to be singularly characteristic of human intelligence. The next time you hear a bird chirping outside your window, you might think twice about what’s going on inside his little birdbrain.

Images: photos by BS Thurner Hof and Kclama at Wikimedia Commons. Graphic of the brain, provided by the author.

The views expressed are those of the author and are not necessarily those of Scientific American.

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