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One of the big things that seems to separate us from other animals is language. We humans will combine and rearrange a limited number of sounds to create a whole dictionary of new meanings. And then, when we make those sounds, other people who speak the same language get what we mean. Look at me. I'm talking to you right now. We're incredible! Incredible, but maybe not as special as we used to think, because apparently, birds can do all of that, too.

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We know that birds can say stuff, but it turns out they're doing way more than parroting the sounds they hear from each other. There are rules to bird babble. To explain, let's start with a rule in human language called "syntax." When we say the words "soap dish," we combine two unique words with their own meanings to create a new meaning. All of a sudden, we've transformed a bar of soap and a dish that you might eat off of into a saucer that you put your soap in to keep it from sliding all over the sink. And when we reorder those words from "soap dish" to "dish soap," it means something totally different again. Even though they're the same sounds coming out of our mouths, combining and putting them in a new order can change their meaning. And that's "compositional syntax" in a nutshell.

That kind of grammar allows us to communicate pretty much anything we'd need to without stretching our memories and vocal capabilities beyond their limits. In fact, it's such a useful tool, that we're not the only ones to use it.

Several studies published in 2016 concluded that pied babblers and Japanese great tits do the same thing; basically, they can say "chirp tweet" and derive a different meaning from "tweet chirp." And while that may seem sweet, these calls are more like urgent communication of a potentially dangerous situation. These birds spend a good chunk of their time looking for food with their heads down, so the calls help communicate danger to others who might not notice a predator off to the side. Using compositional syntax to send this message gives them the same benefits that it gives us; they can communicate more ideas with fewer unique sounds.

The Japanese great tits have specific calls to alert each other of danger, which researchers refer to as "ABC," and other calls that they use to recruit backup and get a buddy to come over, which researchers refer to as "D." When they combine those two calls to make "ABC-D," other birds will look around for danger, and then approach to fight off the threat. That's the "soap dish" of bird calls. The words the birds use can still have their own meanings when used alone. But when used together, they have more precise significance. And that's only the beginning.

Researchers also wanted to see if these birds could tell the difference between "soap dish" and "dish soap" like we can, so they played recordings of the bird's songs that were mixed up or altered to see what they'd do in response. And after hearing the messed-up versions of their songs, the birds didn't respond the way they would to the unaltered versions, which tells us that rearranged sound orders don't really have the same impact on birds as they do in the right order.

Birds take action based on these vocalizations, but since it depends on whether they're discreet or combined and what order they're combined in, scientists say they're using compositional syntax. That's the first time a non-primate has been recorded doing that. Now we know that other animals use complex language and grammar, and keep in mind these are animals with literal bird brains. The plot twist is just how powerful a bird's brain can be.

Lots of neuroscientists study zebra finches because of their incredible song learning capabilities. And while they haven't been found to use the same level of syntax, they do something kind of like a precursor to it. So by recording individual brain cell responses to other birds' songs, they've discovered that cells can recognize syllables and the order they appear in.

If the sounds A, A, A, B are played, these neurons should increase their response to the B, indicating that they detect a difference. But these brain cells also respond to multi-node syllables in unique ways compared to the individual syllables alone. When combinations of ABAB are played over and over again, the neurons gradually respond less over time until AABB is played and they perk back up to the new combo. Basically, when a song used the same syllables in a new order, zebra finch brain cells responded more, indicating that the bird recognizes them as different.

So, their brains are set up to pay attention to the order in which they hear sounds, not just the fact that they hear A and B together. And that all goes back to the "soap dish" versus "dish soap" conversation, which means that bird brains are capable of encoding complex grammar. The jury's still out on whether this means they talk like us, but it definitely means they talk in more complex ways that we previously thought. In the end, at least that aspect of language was never just a human thing.

The tackle these giant questions like, "What makes us different from other animals," we need to ask smaller, empirical questions like, "Can birds tell the difference between 'chirp tweet' and 'tweet chirp.'" Then, the answers to those questions come together like puzzle pieces to help us understand our place in the world more broadly. That's a basic principle of scientific thinking.

But you can learn way more by taking the Brilliant course on "Scientific Thinking." Brilliant is an online learning platform with thousands of lessons filled with science puzzles. This specific course covers the rules of science without getting into nitty-gritty math. Trust me, when you want math, Brilliant has courses for that, too. To get started, visit brilliant.org/scishow or the link in the description down below. That link also give you a free 30-day trial and 20% off an annual premium Brilliant subscription. Thanks for watching this SciShow video, and thanks to Brilliant for supporting it.

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