Projecting Grammatical Features in Nominals: Cognitive Theory and Computational Model October 2009...

Projecting Grammatical Features in Nominals:

Cognitive Theory and Computational ModelOctober 2009

Jerry BallAir Force Research Laboratory

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Theoretical Alignment

• Cognitive Linguistics

– No autonomous syntax

– Grammatical categories are semantically motivated

• Construction Grammar

– Constructions at multiple levels of idiomaticity

– No sharp distinction between lexicon and syntax

• X-Bar Theory

– Prior to introduction of functional heads

– Functional categories—head, specifier, modifier, complement—explicitly represented

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• Simpler Syntax, Conceptual Semantics; GPSG HPSG SBCG; TGG G & B/P & P Minimalism; TAG; LFG; Role & Reference Grammar; Functional Grammar; OT…Descriptive Grammars…DRT; CCG

• Cross Language & Diachronic research

• Competing Linguistic Theories can inform and constrain each other

– No one theory has all the right answers

– We need all the constraints we can get

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• Computational Linguistic Research can inform and constrain linguistic theory

– Human language is (at least) mildly context sensitive (Joshi et al., 1991)

– Human language processing appears to be nearly deterministic (Marcus, 1980)

• Processing doesn’t slow down with length of input

– Large coverage systems need probabilistic mechanisms to handle rampant ambiguity

• Performance considerations can inform and constrain linguistic Competence

– “Grammars are ‘frozen’ or ‘fixed’ performance preferences” (Hawkins, 2004)

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• Psycholinguistic Research can inform and constrain linguistic theory

– Human language processing is incremental (word by word) (Bever, 1970; Tanenhaus et al. , 1995)

• Garden path sentences

– “The horse raced past the barn fell”

• Visual World Paradigm

– Human language processing is interactive (Tanenhaus et al. 1995)

• Visual World Paradigm

“the green…”

“put the arrow on the paper into the box”

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Representational Commitments

• Localist theory of the representation and projection of grammatical features in nominals

– No access to non-local features

• Specifiers & Modifiers (aka Adjuncts), in addition to Heads, project grammatical features

• At level of nominal (NP), projected features are collected into a set without duplicates

• Redundantly encoded features may occasionally conflict – without the expression being ungrammatical

• Grammatical features may be unspecified – without the expression being ungrammatical

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Grammatical Features (in English)

• Definiteness

– Universal, Definite, Indefinite, Negative (Zero)

• Number

– Singular, Plural, Mass (Singular)

• Animacy

– Animate, Inanimate, Human (Animate)

• Gender

– Male, Female, Neuter

• Person

– First, Second, Third

• Case

– Subjective, Objective, Genitive

• Wh, Distance (Near, Far), Measure (Comparative, Superlative)

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Representational Commitments

• Selective encoding of grammatical features

– Where there is no grammatical distinction, there is no grammatical feature

• Without grammatical evidence, there is no basis for learners of English to learn the distinction

• Important to distinguish grammatical function (head, specifier, modifier, complement) from part of speech (noun, verb) or phrasal form (NP, VP)

– Head of a nominal need not be a noun!

– Modifier may be adjective, numeral, noun or verb participle!

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Processing Commitments

• Incremental (word by word), serial, pseudo-deterministic processing mechanism which builds representation, operating over…

• Interactive (context-sensitive), parallel, probabilistic, constraint-based mechanism which selects from competing alternatives (but does not build structure)

• At each choice point, interactive mechanism selects best alternative based on current local context

• Incremental mechanism uses selection to build linguistic representation

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Processing Commitments

• Non-monotonic mechanism of context accommodation for handling conflicts

– Modest adjustment of representation

– Part and parcel of normal processing – not reanalysis!

– Feature overriding

• Replace previous value with new value

– Feature blocking

• Block new value from projecting

• Construal mechanism for handling unspecified features

– Referent of expression may provide (semantic) basis for construal

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Computational Implementation

• Implemented in ACT-R Cognitive Architecture (Anderson, 2007)

– Theory of human cognition based on 30+ years of research

– Computational implementation

– Hundreds of small-scale models implemented in ACT-R

– Few large-scale models…

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Representational Considerations

• Four primary grammatical functions in nominals (adapted from X-Bar Theory before functional heads):

– Specifier

• Deteminers typically function as specifiers

– “the man”

– “those men”

• Quantifiers often function as specifiers

– “some men”

• Possessive nominals/pronouns function as specifiers

– “the man’s book”

– “my book”

Important to distinguish grammatical function from POS or phrasal form!

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– Head

• Nouns typically function as heads

– “the man”

• Verb participles occasionally function as heads

– “the running of the bulls”

• Verbs function as heads in expressions like

– “He gave it a smack” (Dixon, 1991)

• Verbal expressions occasionally function as heads

– “His giving money to the poor is commendable” (Pullum, 1991)


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– Modifier

• Adjectives, Numerals, Nouns and Verb Participles often function as pre-head modifiers

– “the red ball”

– “the two balls”

– “the altitude restriction”

– “the running bull”

• Prepositional Phrases & Relative Clauses typically function as post-head modifiers

– “the book on the table”

– “the book that I gave you”


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– Complement

• Few true complements in nominals

– “The fact that you like me”

• Don’t consider “of” phrases complements of noun

– “The father of John”

– “of” is not optional – noun + “of” licenses complement, not noun (not even relational nouns)

• To the extent that they exist in nominals, complements do not project grammatical features!

– Complements have their own set of grammatical features

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• Specifier provides primary indication of definiteness

– “the man” and “the men”

• “the” projects the definiteness feature definite

• “thedef”

– “a man” but not “a men”

• “a” projects the definiteness feature indefinite

• “a” projects the number feature singular

• “aindef+sing”

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• Head provides primary indication of number

– “the man”

• “man” projects the number feature singular

• “mansing”

– “books” (e.g., “I like to read books”)

• “books” projects the number feature plural

• “books” also projects the definiteness feature indefinite

• “booksplur+indef”

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• Specifier provides primary indication of definiteness; Head provides primary indication of number

– “the books”

• “the” projects the definiteness feature definite

• “books” can project the definiteness feature indefinite, however

– The indefinite feature of “books” conflicts with the definite feature of “the”

– Projection of the indefinite feature by “books” is blocked

• “books” projects the number feature plural

• “thedef booksplur”

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• To be grammatical, nominals typically require an indication of definiteness and number

– “the” alone is ungrammatical because it lacks a number feature

– “book” alone is ungrammatical because it lacks a definiteness feature

– “books” alone is grammatical – indefinite & plural

– “that” alone is grammatical – definite & singular

– “a” alone is ungrammatical – why?

• Blocked by “one” (Pinker, 2000)?

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• To be grammatical, nominals typically require an indication of definiteness and number

– “a books” is ungrammatical because the number feature of “a” and “books” conflict

• Plural feature of “books” cannot override singular feature of “a”

– “a few books” is grammatical – why?

• Plural feature of “few” and “books” overrides singular feature of “a”

• “a few” may be a special construction

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• Is a person feature required for a subject nominal to be grammatical?

• Common view of subject-verb agreement

– 3rd Pers Sing Pres Tense – verb marked with “s”

• 3rd Pers Sing Pres Tense is special

– Non-3rd Pers Sing Pres Tense – verb not marked

• All common and proper nouns treated as third person

Person Number

Singular Plural

First (non-third) I sit we sit

Second (non-third) you sit

Third he sits they sit

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• Alternative viewpoint

– Noun + “s” (plural)

• Verb (unmarked) = plural agreement

– Noun (unmarked singular)

• Verb + “s” = singular agreement

Person Number

Singular Plural

First (ignore for now) we sit

Non-first (second) you sit

Non-first (default) he sits they sit

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• 1st Pers Sing Pres Tense verb agreement is special

– “I” treated as first-person – exceptional agreement for this one pronoun

– All common and proper nouns—tens of thousands—unmarked for person

Person Number

Singular Plural

First I sit we sit

Non-first (second) you sit

Non-first (default) he sits they sit

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• Past-tense of “be” is regular – no first-person exception!

Person Number

Singular Plural

First I was we were

Non-first (second) you were

Non-first (default) he was they were

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• Subjective and Objective Case – comp markers

– Only a few pronouns are marked for case in English

• I, We, He, She, They (subjective)

• Me, Us, Him, Her, Them (objective)

• What about You? Ambiguous or unmarked?

– Common and Proper Nouns are not marked for Case in English

• No evidence of case agreement for common and proper nouns

– “The tall man likes the short man”

• Genitive – a spec marker, not a comp marker

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• No grammatical evidence for neuter gender in English distinct from inanimate

• Only animate (or human) nouns have gender in English (exceptions for names of ships, construal of inanimates as animate, etc.)

– “man” – male vs. “woman” – female

– “child” – unspecified

• Evidence that animacy is a grammatical feature

– The mani I gave ti the book

– The bookj I gave the man tj

• Primary difference is animacy!

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project

project

definite

predicted

the man

“the” projects an object specifier which projects an object referring expression

“the” functions as the specifier of the object referring expression

object referring expression ~ nominal

bind index

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the man

“man” projects an object head which is integrated as

head of the object referring expression projected by “the”

singular human male

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his book

“his” projects a possessive object specifier

which projects an object referring expression

“his” functions as specifier of the object referring expression

distinct bind indexes

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his book

“book” projects an object head which is integrated as

head of the object referring expression projected by “his”

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hers

hers is nice

hers are nice

“hers” projects a pronoun object referring expression

which projects a higher level pronoun object referring expression

“hers” functions as specifier of the higher object referring expression

head of higher object referring expression is implied

number of higher referring expression is unspecified!

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Conclusions

• Grammatical features are projected from heads, specifiers and modifiers within nominals

• Grammatical features may be redundant and may conflict without the nominal being ungrammatical

– “aindef+sing fewindef+plur booksindef+plur”

– “thedef booksindef+plur”

• Grammatical features may be unspecified without the nominal being ungrammatical

– “yoursdef issing-agree nice” vs. “yoursdef areplur-agree nice”

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Conclusions

• Language is processed incrementally (serial, pseudo-deterministic) and interactively (parallel, context sensitive)

• Grammatical feature conflicts are accommodated via non-monotonic mechanisms of overriding and blocking

– Monotonic unification mechanisms (e.g. HPSG) are inconsistent with overriding and blocking!

• Grammatical feature underspecification is accommodated via (semantic) construal processes

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Questions?

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• Only posit grammatical features for which there is grammatical evidence

– No solid grammatical evidence for third-person grammatical feature in English

– No grammatical evidence that “the” is marked for number

• If “the” is functional head, how does number feature get projected to DP?

– Extended projections a la Grimshaw (2000)

– Dual heads a la Cann (2001)

– “the” marked for number (Radford, 1997)

– “the” checks number of complement (Radford, 2004)

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negative

“no” projects an object specifier which projects an object referring expression

“no” functions as the specifier of the object referring expression

no airspeed or altitude restrictions

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“airspeed” projects an object head which is integrated as

head of the object referring expression projected by “no”

singular inanimate


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The processing of “or” is delayed until the word after “or” is processed.

“altitude” projects an object head. In the context of “or” and “airspeed”,

“altitude” is conjoined with “airspeed” into a conjoined object head.

The conjoined object-head overrides the previous object head.

function overriding


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function shifting

“restrictions” projects an object head. In the context of an object head,

the previous object-head is shifted into a modifier function so that

“restrictions” can function as the head of the object referring expression

plural

(feature overriding)


Projecting Grammatical Features in Nominals: Cognitive Theory and Computational Model October 2009...

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