LIN 737 - 4. X-bar theory

Topic 4

X-bar theory

Introduction

First, you should probably know that X-bar theory is often written as 'X'-theory'. These are pronounced the same and refer to the very same theory. Recall that we formal, cognitive linguists are in the business of trying to understand how knowledge of language might be represented the mind, and phrase structure is an important part of that knowledge.

A plausible theory of phrase structure should try to make it as general and simple as possible: general, because then the rules and building blocks we propose for one category also apply to other categories and we don't need special stuff for each and every category; simple because, well, simple is always best! We need our theory to be general and simple because then it would help to explain how children can so easily acquire PS rules, and how humans in general manage to do language so effortlessly.

The challenge, though, is that although the goal is to make phrase structure as simple as possible, the theory shouldn't lose any descriptive power. In other words, it should allow us to accurately represent any and all phrases and sentences that actually are possible to say, in all their beautiful diversity, recursivity, and creativity.

So X'-theory attempts to do just that! In a nutshell, X'-theory postulates that all the major categories (N, V, P, and A) always follow the same template structure, namely the X'-schema (pronounced "X bar schema"). In the illustrating diagram to the right, X represents any of these major categories.

The advantage of the X'-schema is that it provides us with room in each and every phrase for modifying material that (i) precedes the head of the phrase and (ii) follows the head of the phrase. Modifying material that precedes the head is called the specifier, and modifying material that follows the head is called the complement. Specifiers and complements are always XPs (phrases belonging to some category) themselves.

Besides specifiers and complements, there is also a unique position in the structure for adjuncts. This is another advantage of X'-theory: we know from constituency tests that adjuncts really do behave differently from specifiers and complements. Having a structural position for adjuncts allows us to formally distinguish them from specifiers and complements.

By the end of this unit, we will also have introduced two new categories, which also follow the X'-schema. These are T ('tense'), and C ('complementiser'), and we argue that the structure of each and every clause follows the same template:

Intro to X' (part 1)

No matter how different phrases of different categories can appear, they all actually follow the same basic pattern. This observation leads us to propose what is called the X'-schema.

In this video, you learn the template for the X'-schema, as well as what motivates us to propose something like the X'-schema. You also and you learn terms like specifier and complement, which refer to parts of the phrase structure in an X'-schema.

Intro X' (part 2)

In this video, you learn how coordination (remember the constituency test?) provides evidence for the X'-schema across various phrase types.

You also learn some new terms for referring to different parts of the X'-structure, namely maximal projection, intermediate projection, and sisters. We also discuss the different natures of complements and specifiers, and get to see how this difference is reflected in the X'-schema.

Auxiliaries (part 1)

How do auxiliaries fit into the X'-theory? And what is their position in the structure of a clause?

In this video, we use the constituency tests, and some other techniques, to gather evidence that auxiliaries are NOT inside the verb phrase.

Auxiliaries (part 2)

In this video, we review some arguments for auxiliary verbs being the heads of a tense category 'T'.

We learn more about the structural properties of T, and argue that TP is present in the structure of every clause, even when there is no auxiliary verb.

Complementiser Phrases (CPs)

We argue that clauses are headed by CP, not S.

You also get to see how to use TreeForm, which is a freely downloadable tree-drawing program (Download it here)

Arguments & adjuncts (part 1)

In this video, we review some evidence for the idea that arguments and adjuncts occupy different structural positions in VPs.

We also work out some formal definitions for argument and adjunct.

Arguments & Adjuncts (part 2)

In this very short video, we unpack the definitions we gave to arguments and adjuncts in part 1. We do this in terms of the X'-schema.

Noun Phrases (NPs)

There can be complements and adjuncts in noun phrases, too. The structural definitions for these are the same as they for arguments and adjuncts in VPs

Breakdown of the clause

In the final video in this unit, we get some perspective of clause structure as consisting three 'layers', namely CP-TP-VP. Each layer, or domain, adds a special kind of meaning: the VP domain determines what kind of event occurs, and who participates; the TP domain anchors the event in time; the CP domains embeds the clause in discourse.

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