X-Bar Theory Of Psg
‘X-bar syntax, as a theory of phrase structure grammar, makes a significant contribution to both the descriptive and the explanatory adequacy of Linguistic Theory.’
The aim of a theory of language is to describe a speaker’s linguistic competence. (Class notes) In order for a grammar to be satisfactory it must satisfy two main conditions: descriptive adequacy and explanatory adequacy. A grammar that satisfies descriptive adequacy “describes the grammatical sentences of a language in such a way as to uncover deeper principles and rules, which capture in a more satisfactory way the intuitions of the native speaker. A grammar which is formulated in accordance with the principles and conventions of a general i.e., universal linguistic theory with explanatory power is said to meet with explanatory adequacy.” (Class notes)
During the first half of the term, we were introduced to a theory of phrase structure grammar (PSG) which includes two levels of categories: word-level (N, V, A, P, etc.) and phrase-level (NP, AP, VP, PP, etc.). However, this is not a satisfactory method of classification because it does not include a description for a string of words that is neither a full phrase nor a word; therefore failing to satisfy descriptive adequacy. Furthermore, it does not satisfy the condition of explanatory adequacy because it does not enable us to state general principles that are valid across different grammatical categories within a language, i.e. category neutral. Moreover, a grammar with two levels of categories is not powerful enough to state principles that hold true universally. In this essay, I will demonstrate how the X-bar theory of phrase structure grammar contributes significantly to both the descriptive adequacy and explanatory adequacy of Linguistic Theory using examples from English and other languages.
Let us first examine why it is necessary to add a third intermediate grammatical category which is neither a full phrase nor a word. Evidence for this is found in the following phrase: the sultan of Brunei. Firstly, we can prove that this phrase is a constituent by performing the following tests: 1) coordination – the sultan of Brunei and ruler of the empire. 2) Substituting the proform one – This sultan of Brunei is more handsome than the last one. Both of these tests prove that the constituent is sultan of Brunei and that it is smaller than a full phrase because in coordination and in substituting the proform one, the Determiner ‘the’ is not included. In other words, it is not correct to substitute the proform one and have, *This sultan of Brunei is more handsome than the last this sultan of Brunei. (Class notes) Thus we see the need for an intermediate category. The best way of representing this category is by using bar notation, i.e. N, N’, and N’’. “The reason for this is that it captures the commonality in the categorial status by the use of the same category symbol and captures the difference in complexity between categories by the number of bars that accompany the symbol.” (Class notes) This is an example of how X-bar theory of grammar is able to capture descriptive adequacy more sufficiently than a two-category level PSG.
Another advantage of X-bar theory is that it enables us to capture formally a distinction between complements and adjuncts. (Class notes) This is advantageous because it can account for certain ambiguities. For example, in PSG there is no satisfactory way of capturing the ambiguity in the following: A teacher of high moral principles. X-bar syntax enables us to capture the ambiguity very clearly in the following way:
A teacher of high moral principles vs.
A teacher of high moral principles
In the first tree structure, the meaning of the sentence is the teacher has teaches high moral principles. In the second one, the teacher is a person who has high moral principles. Thus, the complement is closest to the head noun, i.e. sister of the N, and the adjunct is sister of the N’.
Another reason for which it is advantageous to distinguish between a complement and adjunct is that this distinction enables us to account for the distributional properties of PPs in terms of their status either as complements or as adjuncts. (Class notes) Firstly, it is only possible to have