Syntactic Trees and X’ Theory

Syntactic Trees and X’ Theory


So let’s talk about trees. But not the kind
with flowers or fruit or leaves. No, I mean the trees that underlie our sentences, the
ones that build up the structure that our words slot into and let us build bigger meanings.
Every time you build a sentence, every time someone talks to you, you’re growing
one of these trees. All I’ve just been saying has planted a little grove of language in your
mind. So let’s do some climbing! I’m Moti Lieberman, and this is The Ling Space. There’s a whole branch of linguistics that’s
devoted to looking at the structure of sentences, known as syntax. But why do we even bother? Can’t we just stack our
words one on top of another like pancakes to build some delicious meanings? Well, there has to be some structure, or else
we’d be able to work back from a smashed-up wreck of a sentence like “a threatening hand is
who Angel missing lawyer the is,” and have it get the same meaning as the original, “The
lawyer who is missing a hand is threatening Angel.” Clearly, one of those is a good
sentence of English, and the other one is just gibberish that happens to be made up of English words.
So structure must matter. But what kind of structure do we need? Well,
whatever hypothesis we come up with, it’s got to be really flexible. That’s because it has
to capture all the variation in how all the different languages in the world put together
all their different sentences. We don’t want to say Icelandic speakers have one basic way of making
sentences, but Telugu speakers have a second one, and Cree speakers a third. Building sentences
with their own internal structures is something common to every language of the world, and so
an Icelandic baby dropped off in southeastern India will learn Telugu syntax just fine.
That’s because the basic framework of syntax is universal. In fact, it’s part of Universal Grammar,
the linguistic knowledge all people share. But with all the surface differences, finding
something that can branch its way through every human language isn’t obvious.
Not only does it have to be flexible, it also has to be abstract. So, here are a lot of hypotheses out there,
but one of the most commonly talked about ones, is called X’ theory, first proposed
in the early 70s. The X in X’ doesn’t stand for anything; it’s a
variable, like in algebra. We can use that variable to make a basic structure, a template,
like this: X can stand for any noun or verb or adjective or any category you want to build
a phrase around. You end up with chunks of syntax that can be stacked and connected together,
and you do it in a way that’s flexible enough to communicate anything that you want, in any language that you want. This gets a lot clearer when you start looking
at some examples. Let’s start with something really simple: a name, like “Cordelia.”
Okay, so in your mental lexicon, where you store all your words, each term belongs to
a syntactic category – which is like a part of speech, so a noun, an adverb, etc. “Cordelia”
is a noun, so when we want to put “Cordelia” in our X’ tree we replace the Xs
with Ns for nouns. In this phrase, Cordelia is the “head”, which is the part of the phrase with
the most content and meaning. Because Cordelia’s the head of the phrase,
and because it’s a noun, the whole thing will become a noun phrase, or NP. Great! Done.
Except, not really. This might work if we never said anything more than bare nouns and
verbs and things, but natural language is a lot more involved than that. So sometimes
all you want to say is Cordelia, but sometimes you might want to say nice things about Cordelia.
Maybe you want to say, “The amazing Cordelia.” Where did those other words fit in? Well, that’s where the “bar” part of
X’ theory comes to the rescue. So between the head and phrase level, we introduce one more
layer of complexity: that’s the bar level, which is written with an apostrophe next to the letter that
represents the head. The bar level is an intermediate, repeatable stage in the template that allows us all the
flexibility we need to build bigger phrases and sentences. Let’s
see how this works. Since they’re still all still associated with
the noun – they’re all to do with Cordelia – you need to have extra room for those extra words in your noun phrase. So they need to get nestled into the NP, and that’s where the N’ comes
in. Now your sentence is shaping up. But wait. Why bother having these intermediate
stages at all? Even if we know all these words come together to make a noun phrase, why put
in all these extra levels of structure? Why not just put in an NP at the top, and then different labels for all the words below – so an N for the noun, an A for the adjective, etc. That’d be easier, right? Well… here’s the thing. The reason we
needed syntax in the first place was to give structure to how come sentences mean what
they do, and have the word order that they do. All the information about what a sentence
means, that is the syntax, and it has to be visible in our diagrams, why bother drawing trees in the first place, right? So we end up needing to branch things off
two by two with bar levels, otherwise we wouldn’t know what parts
go with other parts. We can even put as many bar levels into the structure as we want,
so it’ll work for any kind of sentence. For example, if we said “the quirky, supremely
intelligent Fred,” and there was no internal structure, so everything was just flat, we
wouldn’t know that supremely was supposed to go with intelligent, and not with quirky.
We wouldn’t be able to come up with any rules to stop these things. All the
rules, everything that’s okay and not okay, has to be seen in the structure.The bar levels
give us a hierarchy that allows us to make sense of things like this. Now, we know “supremely”
goes with “intelligent”, and that you can’t just pull words out willy-nilly to
make nonsense sentences. What X’ theory shows us is the way that we can build structure in order to capture all the facts of language,
along with the flexibility to add whatever we like. They let us add potentially infinite
parts before the head, like “The bespectacled bookish Brit Wesley,” or after it, as
in “the vampire with a soul and a big black coat.” And this sort of syntax also lets
us capture facts about how we form larger sentences, as questions, find ambiguity, and
all sorts of other things, which we’ll talk about in the future. Linguists today have a lot of other hypotheses
about syntax, too, but X’ is a great place to start because it shows all of the hallmarks
of why syntax is real and useful. It can be applied to any type of word, in any type
of sentence, in any type of language. It’s just a template: a head with a phrase and
as many intermediate stages as you’d like. But by using that one little template, and
putting it in every time you make a phrase, you can shape a whole world of language. Shaping
those little trees can tell you what language is. And that’s worth the
climb. So we’ve reached the end of the Ling Space
for this week, but if you were making your own happy little trees, you learned that sentences
must have an internal structure to them if we’re going to capture the facts we know about them;
that the basic template of that structure needs to be flexible and universal; that the
template in X’ theory consists of a head, a phrase, and as many bar levels as you need
to fit all the words you have; and that the structure should branch off two-by-two to
fit the facts about hierarchy that we feel are true. The Ling Space is written and produced by
me, Moti Lieberman. It’s directed by Adèle-Élise Prévost, our production assistant is Georges
Coulombe, our music and sound design is by Shane Turner, and our graphics team is atelierMUSE.
We’re down in the comments below, or you can take the discussion back over to our website,
where we have more information on this topic. Check us out on Tumblr, Twitter, and
Facebook, and if you want to keep expanding your own personal Ling Space, please subscribe.
And we’ll see you next Wednesday. /seləvu/!

Danny Hutson

51 thoughts on “Syntactic Trees and X’ Theory

  1. So, I'm a little confused about how this X bar is a theory and not just a labeling device, like old-fashioned diagramming sentences, which is tool or nomenclature to analyze the sentence. When I hear theory, I think rules with predictive power. How is X bar that? 😄

  2. @Patricia Schneider-Zioga Thanks! Glad you got them. We really like doing that kind of thing. ^_^

  3. Ok, now that the video has progressed I can tell we are both Angel fans! I liked Lindsey by the way. Christian Kane is awesome.

  4. I just trumbled over your great channel! Reminds me so much of my study of empirical linguistics. I just wondered why you left S/S'. Or did you get it in another video?

  5. At the moment Iḿ writing my bachelor thesis about clitics in czech sentences. Nearly every author uses the government-binding-theory and I was so confused by all these C' and CP and Topicalization….and they nowhere explained those shortcuts. Thx for explaining and simplifying! So now I can try to understand Topicalization, because the X'- Theory I know ^^

  6. thanks for the video but i have a question if i have a sentence and it had at the end 'to look after them'
    how would i draw a tree for it i know that look after is a phrasal verb and them is a pronoun so it would be a complement
    right? would do i write in its branch and also to what would it class as
    i would appreciate it if you can help me

  7. new to your channel, and IT IS AMAZNING. (I am a LING student). THIS IS THE YOUTUBE SERIES I NEED IN MY LIFE. Maybe linguistics resources are far and few between, but your videos help explain so much

    Thank you, thank you so, so much sir

  8. I sort of get why we'd go from NP—N—Cordelia, but I really don't get why we need the intermediate steps of N' (NP–N'–N'-N-Cordelia). It just seems like it unnecessarily complicates the process.

  9. i just started to take a linguistics course at my university because it was the only thing that could fit my schedule. tossed myself head first into a world of confusion. I'm supremely happy that I was able to find this channel.

    And now im thinking about just how big and complicated looking syntactic tree could get….. and im afraid

  10. Links to your videos are in our lecture slides. It's been very helpful and interesting. I like the way you format your videos as well. -speech pathology student

  11. Why do you only need eight minutes to make me understand tree structures whilst my teacher gives tons of lectures on this topic to an audience that has no clue what's going on?

  12. Your video makes a lot of sense and I definitely understand the way you do it but every single one of the examples in my textbook is entirely different. Not every word has a ' and I am very confused ._.

  13. Any purely tree structure contradicts with complements, which depend on two constituents at the same time.

  14. So the reason we make syntax trees is to make a visual note about how languages can say
    The amazing Cordelia
    Codelia amazing the
    The Cordelia amazing

    But not amazing the Cordelia or Cordelia the amazing. But we can have Cordelia the Amazing in English…

    I still don't get syntax trees 😅

  15. This video was very useful! I was struggling, trying to understand what trees are and you just saved me. Your way of explaining these complex structures is so easy to understand. You're a great teacher! Thank you! ^^

  16. As a linguistics student who struggled with syntax in every seminar without having a clue what was going on, this was very helpful! Amazing how an explanation in such a short time can be the key to understand the topic and not be lost anymore. Great preparation for an upcoming test!

  17. I need to say how much I loved that you taught me tree structures by using characters from one of my favorite shows! The shirt caught my eye first and then you just made it all better with all the amazing references. Thank you!!

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