Download Projecting Grammatical Features in Nominals

Projecting Grammatical
Features in Nominals:
Cognitive Theory and Computational Model
October 2009
Jerry Ball
Air Force Research Laboratory
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
2
Theoretical Alignment
•
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
3
Theoretical Alignment
•
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)
4
Theoretical Alignment
•
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
“the green…”
– Human language processing is interactive (Tanenhaus et al.
1995)
• Visual World Paradigm
“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
6
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!
8
Processing Commitments
•
Incremental (word by word), serial, pseudodeterministic 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
10
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…
11
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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Representational Considerations
– 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)
Important to distinguish grammatical function from POS or phrasal form!
13
Representational Considerations
– 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”
Important to distinguish grammatical function from POS or phrasal form!
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Representational Considerations
– 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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Representational Considerations
•
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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Representational Considerations
•
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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Representational Considerations
•
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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Representational Considerations
•
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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Representational Considerations
•
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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Representational Considerations
•
Is a person feature required for a subject nominal to
be grammatical?
Person
First (non-third)
Number
Singular
Plural
I sit
we sit
Second (non-third)
Third
•
you sit
he sits
they sit
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
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Representational Considerations
•
Alternative viewpoint
– Noun + “s” (plural) 
• Verb (unmarked) = plural agreement
– Noun (unmarked singular) 
• Verb + “s” = singular agreement
Person
First
Number
Singular
Plural
(ignore for now)
we sit
Non-first (second)
Non-first (default)
you sit
he sits
they sit
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Representational Considerations
•
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
First
Number
Singular
Plural
I sit
we sit
Non-first (second)
Non-first (default)
you sit
he sits
they sit
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Representational Considerations
•
Past-tense of “be” is regular – no first-person
exception!
Person
First
Number
Singular
Plural
I was
we were
Non-first (second)
Non-first (default)
you were
he was
they were
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Representational Considerations
• 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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Representational Considerations
•
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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Computational Implementation
object referring expression ~ nominal
the man 
project
project
definite
bind index
predicted
“the” projects an object specifier which projects an object referring expression
“the” functions as the specifier of the object referring expression
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Computational Implementation
the man 
singular
human
male
“man” projects an object head which is integrated as
head of the object referring expression projected by “the”
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Computational Implementation
his book 
distinct bind indexes
“his” projects a possessive object specifier
which projects an object referring expression
“his” functions as specifier of the object referring expression
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Computational Implementation
his book 
“book” projects an object head which is integrated as
head of the object referring expression projected by “his”
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Computational Implementation
hers 
head of higher object referring expression is implied
number of higher referring expression is unspecified!
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
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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
“yoursdef
issing-agree nice” vs.
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
33
Questions?
34
Representational Considerations
•
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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Computational Implementation
no airspeed or altitude restrictions 
negative
“no” projects an object specifier which projects an object referring expression
“no” functions as the specifier of the object referring expression
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Computational Implementation
no airspeed or altitude restrictions 
singular
inanimate
“airspeed” projects an object head which is integrated as
head of the object referring expression projected by “no”
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Computational Implementation
no airspeed or altitude restrictions 
function overriding
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.
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Computational Implementation
no airspeed or altitude restrictions 
plural
(feature overriding)
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
39