Linguistic Theory Lecture 2 Phrase Structure

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

Traditional Grammar: 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 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 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.) In the languages being studied, grammatical functions were mainly indicated morphologically (Case, agreement, etc.) Grammatical functions were defined semantically 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 Therefore grammatical functions were associated with words and no phrases were necessary

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

Negative points: 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 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? Why do phrases distribute the way they do?

–Linguistic Relativity Popular view of the structuralists Popular view of the structuralists Each grammar could only be studied relative to itself – i.e. No commonalities between languages to compare them 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 Therefore, in principle, languages could be anyhow They were, more or less, an accident of the environment and culture they were set in 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 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 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 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 do most NPs contain a noun? Why is [in the park] not an NP? Why is [in the park] not an NP?

Why is a noun phrase a noun phrase? Why is a noun phrase a noun phrase? –Partly on distributional grounds NPs distribute the same as SOME nouns NPs distribute the same as SOME nouns But pronouns distribute like determiners and NPs distribute like pronouns – so NPs distribute like SOME determiners!!! 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 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 Even though structuralists eschewed meaning, it seems that they still took the classical position to heart

So why is a PP a PP? 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 Change to rationalism and the study of language as knowledge We can only study internal language by hypothesis testing We can only study internal language by hypothesis testing Therefore we need grammatical hypotheses (= grammar) to be explicit Therefore we need grammatical hypotheses (= grammar) to be explicit –Requires formalising rules

Phrase Structure 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 NP  Adv V NP So still unconstrained = not explanatory So still unconstrained = not explanatory –But...

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

This analysis fails to capture certain facts: 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: Transitive verbs are usually restricted to VPs which contain objects: –They liked John –* they liked Intransitives are restricted to VPs without an object Intransitives are restricted to VPs without an object –He smiled –* he smiled them So in the passive, things are turned upside down So in the passive, things are turned upside down Why? 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: 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 A phrase structure analysis cannot account for these observations

Mathematical Linguistics 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 ZB) X Y Z a)X  Y ZB) X Y Z –But what does rule b) produce? b)W X  Y Z 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: 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 This rule rewrites X, when it is preceded by A The rule is ‘context sensitive’ 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 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 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 So: unrestricted rewrite grammar context sensitive PS grammar context free PS grammar

The question is: what kind of grammar is human 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: Phrase structure grammars (even context sensitive ones) still allow things that we don’t find in human languages: –PP  Adv V Phrases have heads 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 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 In 1970 Chomsky proposed a restriction on rewrite rules which addressed this problem X-bar theory: X-bar theory: –X n ... X m... (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! 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 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) 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: But we can overcome this problem if we allow a new kind of category: –X/Y Called a ‘slash’ category Called a ‘slash’ category Means an X which lacks a Y Means an X which lacks a Y S NP S/NP who NP VP/NP John V NP/NP met  S NP S/NP who NP VP/NP John V NP/NP met 

Rules needed: Rules needed: –X/X   basic rule –Y/X ... Z/X..inheritance rule –Y  X Z/Xresolution rule