You know that Rihanna song that features what some have called “gibberish” lyrics—the words that critics, apparently unfamiliar with the fact that the vast swath of popular music originated in Jamaica, failed to recognize as patois? It’s a case of people speaking one language and failing to recognize the words and syntax of another.
Turns out we’ve been doing that to birds, too, according to new research: Japanese great tits (Parus minor) have syntax, just like humans do.
What that means, Toshitaka Suzuki, David Wheatcroft, and Michael Griesser write today in Nature Communications, is that birds can form different messages from the same musical notes and phrases, just as humans form different messages from the same words and phrases. To wit: “O, for a Muse of fire, that would ascend the brightest heaven of invention” doesn’t mean the same thing as “O, for fire of a Muse, that would ascend the invention of brightest heaven,” even though the two sentences use exactly the same words. Other sentences using the same words mean nothing at all: “Muse fire of a heaven, would invention the of ascend, O, for that brightest.”
Birds can form different messages from the same musical notes and phrases.
Parus minor, Suzuki, Wheatcroft, and Griesser argue, know such differences, or at least they know the difference between meaningful and nonsensical sequences of notes. The researchers focused on two kinds of calls, a sequence of notes the researchers label ABC (not the musical ABC, to be clear), a fourth, repeated note labeled D, and combinations of the two. Previous research indicated those sequences were distress calls related to predators, but the question remained whether they had syntactical significance. That is, would ABC-D mean the same thing as D-ABC?
To find out, the researchers recorded the Parus minor calls and played them for 21 tits out in a forest near Karuizawa, Japan. Following ABC, the songbirds turned their heads from side to side, apparently scanning for predators. After hearing D calls, Parus minor more or less swarmed the loudspeaker, suggesting that ABC meant “danger” and D meant “help.” The combination ABC-D led to both scanning and mobbing the loudspeaker.
The key, however, would be how they reacted to D-ABC calls, which the researchers had to put together by editing ABC-D audio. If the birds reacted to that and ABC-D the same way, it would mean they didn’t understand syntax. If they reacted differently or didn’t react much at all, it would suggest they did have syntax.
The results: Parus minor basically didn’t do anything after D-ABC. They didn’t turn their heads much, and they flew toward the loudspeaker only about a third as often as when they heard ABC-D—to them, D-ABC was either nonsense or meant something very different.
“[O]ur findings highlight that the ability to recognize the combinations of different meaningful units as compositional calls has evolved in birds,” and not just humans and primates, the team writes—a result that might help uncover the origins of complex human language as well.
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