Linguistic Theory

Linguistic Theory Lecture 2 Phrase Structure

What was there before structure? • Classical studies: • Languages such as Latin • Rich morphology • Not many word order restrictions • Mainly associated with meaning • Words carried meaning • Therefore main emphasis on word form paradigms and meaning, but not much on syntax

Traditional Grammar: • Prescriptive: claimed Latin to be ‘pure’ language and all others were deviations • Application of what was known about classical languages to modern languages • Thus, phenomena that were not similar to Latin (word order restrictions) were ignored or seen as ‘deviant’

1800s • As early as the late 1500s similarities between Indian and European languages had been noted • But the idea of an Indo-European family of languages did not become popular until the start of the 1800s. This was a ‘new era’ for linguistics • Again the concentration was on classical languages (Greek, Latin, Sanskrit) • Most easily accessible data concerned word forms (phonology/morphology) • Once more, syntax was not well studied

In most of these approaches, the main aspects of syntactic description concerned grammatical functions (subject, object, etc.) • In the languages being studied, grammatical functions were mainly indicated morphologically (Case, agreement, etc.) • Grammatical functions were defined semantically • E.g. Subject = the one who performs the action/what the sentence is about • Therefore grammatical functions were associated with words and no phrases were necessary

Subordination of clauses was recognised • So the basis of constituent structure was available (one thing containing other things) • But the need to extend this to non-clausal groups of words (phrases) didn’t seem to arise

Structuralism • Empiricist view + discovery procedures = constituent structure analysis • Positive points: • Could account for distributional patterns • John/poor John left the room • I saw John/poor John • Could account for the FACT of distribution

Negative points: • Was not formalised or made specific in terms of rules which constituted a grammar • Such a grammar would be in the mind, which didn’t exist • Therefore did not consider the issue of restricting grammatical theory to make it more explanatory • Why do phrases distribute the way they do?

Linguistic Relativity • Popular view of the structuralists • Each grammar could only be studied relative to itself – i.e. No commonalities between languages to compare them • Supported by observation of Amerindian languages • Therefore, in principle, languages could be anyhow • They were, more or less, an accident of the environment and culture they were set in

We determine what is a phrase in a language on distributional grounds • But we cannot say why certain groups of words are phrases because in principle any group of words could be a phrase • Description is easy: • The English gerund is an NP because it distributes like an NP • I don’t like [careful plans]/[carefully making plans] • [careful plans] are/[carefully making plans] is difficult • But the gerund, unlike most NPs, contains no obvious noun • [NP [Adv carefully] [V making] [NP plans]] • Explanation is impossible • Why do most NPs contain a noun? • Why is [in the park] not an NP?

Why is a noun phrase a noun phrase? • Partly on distributional grounds • NPs distribute the same as SOME nouns • But pronouns distribute like determiners and NPs distribute like pronouns – so NPs distribute like SOME determiners!!! • From tradition • On the basis of semantic salience, traditional grammars took nouns to be grammatical functions • Even though structuralists eschewed meaning, it seems that they still took the classical position to heart

So why is a PP a PP? • The preposition is hardly the most semantically salient part of a preposition phrase • Distribution shows that they are not NPs • What distinguishes them from NPs is that they contain a preposition, therefore we call them preposition phrases • This is not very consistent • But it doesn’t matter because there is no need for consistency as, in principle, anything is possible

Chomsky and Phrase Structure Grammar • Change to rationalism and the study of language as knowledge • We can only study internal language by hypothesis testing • Therefore we need grammatical hypotheses (= grammar) to be explicit • Requires formalising rules

Phrase Structure Rules • E.g.: VP  V NP • A list of such rules = Phrase Structure Grammar • A PSG produces a set of Phrase Markers (tree diagrams) • Still nothing wrong with: • NP  Adv V NP • So still unconstrained = not explanatory • But ...

Formalising PS rules helped to: • Point out problems with basic Immediate Constituent Analysis to show that more is needed to account for human languages • Further our understanding of rule systems and to suggest what is needed to capture natural language data

Problems for IC analysis: E.g. The passive • We might analyse a passive sentence thus: • S NP VPJohn Verb Aux V was liked • This is easy to do with PS rules • But...

This analysis fails to capture certain facts: • Only transitive verbs can appear in the passive: • He was liked • * he was smiled • Transitive verbs are usually restricted to VPs which contain objects: • They liked John • * they liked • Intransitives are restricted to VPs without an object • He smiled • * he smiled them • So in the passive, things are turned upside down • Why?

Verbs place semantic restrictions on their subjects and objects • John hates insincerity • * insincerity hates John • Insincerity worries John • *John worries insincerity • Hate  animate/sentient subject • Worry  animate/sentient object • In the passive these restrictions are reversed: • Insincerity was hated (by John) • *John was hated (by insincerity) • John was worried (by insincerity) • * insincerity was worried (by John) • A phrase structure analysis cannot account for these observations

Mathematical Linguistics • Formalising rules for phrase structure using re-write rules enabled Chomsky to explore aspects of grammar that had never been thought of before • Rule a) produces structure B): • a) X  Y Z B) X Y Z • But what does rule b) produce? • b) W X  Y Z • Such rules produce structures which cannot be represented by a tree diagram

Phrase Structure Grammar: rules can have only one element to the left of the arrow • Unrestricted Re-write System: rules can have more than one element to the left of the arrow • Note that a PSG is a (restricted) kind of URS • So, any language that a PSG can generate, a URS can too. But not vice versa • URS languages PSG languages

There are grammars which are more restrictive than URSs but less restrictive than simple PSGs: • A X  A Y Z • This rule rewrites X, when it is preceded by A • The rule is ‘context sensitive’ • A context sensitive rule is a kind of unrestricted rewrite rule where only one element on the left of the arrow is rewritten • A context free rule is a kind of context sensitive rule with no context stated • So: unrestricted rewrite grammar context sensitive PS grammar context free PS grammar

The question is: what kind of grammar is human grammar? • This could be a way of restricting linguistic hypotheses and making them more explanatory • Most linguists think that the phrase structure part of human grammar is no more complex than a context free rewrite system • Though all agree that this is not enough to account entirely for all grammatical phenomena

More restrictions • Phrase structure grammars (even context sensitive ones) still allow things that we don’t find in human languages: • PP  Adv V • Phrases have heads • There is no way to represent the notion of the head in a standard rewrite rule because what is on the left of the arrow is not connected to what is on the right • X  Y Z

In 1970 Chomsky proposed a restriction on rewrite rules which addressed this problem • X-bar theory: • Xn ... Xm ... (ignore n and m) • Rules are restricted to the type where there must be an element to the right of the arrow which is the same category as the one on the left • X-bar grammars do not form a subset of any of the types in the Chomsky hierarchy • So perhaps mathematical types are not so useful afterall!

Generalised Phrase Structure Grammar • Some argued that Chomsky was wrong about the limitations of context free PSGs • The problem Chomsky pointed out was that elements often appear in one position when we would expect them to be in another (e.g. Passive)

But we can overcome this problem if we allow a new kind of category: • X/Y • Called a ‘slash’ category • Means an X which lacks a Y • S NP S/NPwho NP VP/NP John V NP/NP met 

Rules needed: • X/X   basic rule • Y/X  ... Z/X .. inheritance rule • Y  X Z/X resolution rule

Linguistic Theory