Transcript ecg - UCSD Cognitive Science

Introduction to Embodied
Construction Grammar
March 4, 2003
Ben Bergen
[email protected]
Goals of the talk
• Outline ECG view of language
understanding
• Sketch ECG formalism in some detail
– Schemas (semantic knowledge)
– Lexical constructions
– Phrasal constructions
Basics of ECG
• The basic units of linguistic knowledge are
form-meaning pairings, constructions
– These may include words, morphemes, idioms,
phrasal patterns, etc. - anything that has form
and meaning.
– Consider the ditransitive construction, which
has a transfer-of-possession meaning
• Looking to get an assist, John broomed me the ball.
• With a healthy achoo, I sneezed the napkin off the
table.
Basics of ECG
• Why bring semantics into grammar?
• Whether a sentence is acceptable depends on the
semantic interaction between a sentence pattern
(phrasal construction), a verb, and arguments.
– John broomed me the ball.
– ?John broomed me the Volkswagen.
(acceptable if John and I are dinosaurs)
– ?I sent London the newest edition.
(acceptable if London stands for a person or group of
people in London capable of receiving things.)
– ??John ate me the ball.
(presumably, it’s acceptable some time, but when?)
– ?John sneezed me the ball.
Basics of ECG
• Constructions are learned associatively
– Constructions, like the pairing between /dag/
and the category DOG, or between the
ditransitive phrasal pattern and the concept of a
transfer of possession event must be learned
because they are idiosyncratic.
– The basic mechanism in the brain for learning
strengthens connections between neural
structures that fire together.
Basics of ECG
• Meaning is encoded in ECG using schemas
– Schemas: mental representations of a recurrent
perceptual, motor, or other experience.
– Most theories of the mind include schemas, aka
schemes, frames, scripts, gestalts, ICMs, …
– Schemas have two facets.
• They are encyclopedic, capturing the motor,
perceptual, etc. details of the particular experience
• Some important components of these schemas are
externally accessible, and serve as an interface
Basics of ECG
• Container schema
– We have lots of
experiences of
containers, and
detailed knowledge
about these
– But there are certain
fundamental
components of the
container schema
that are crucial
Schemas
• Source-Path-Goal schema encodes motion
of a trajector along a path
Basics of ECG
• Other schemas include
– Contact
– Transfer
– Commercial transaction
– Child
– Bob
– Jump
– … and thousands more
• We’ll see some more example in a moment
Language Understanding Process
Language Understanding Process
• An utterance is perceived
• This activates the form pole of some constructions
• The analysis process assembles the
constructions, binding together their forms and
their meanings
• The product is a constructional analysis
• This yields a semspec, parameterized schemas
linked together in specified ways
• The understander simulates (imagines) the
content by fleshing out the semspec
• Resulting inferences are propagated through the
conceptual system.
Grammar
• That’s an outline of language understanding
using ECG
• Now: actual representation of constructions
and schemas themselves
• We’ll work through an example sentence
– Mary tossed me a drink.
• One possible constructional analysis of this
sentence (where we’re going):
Constructional analysis
Referring Expressions
• The sentence has three referents in it
• All referring expressions share a Referent
schema
Referring Expressions
• The Referring-Expression construction, or
Ref-Expr is inherited by all constructions
that perform the pervasive function of
referring
Referring Expressions
• The Mary construction inherits Ref-Expr
– Its form pole is specified
– Its meaning pole is bound to the Mary schema
– Its referent has an accessibility status
Referring Expressions
• Me inherits
Ref-Expr
• Constructional
feature case
has the value
object
• Form pole is
“me”
• Its meaning
pole is bound
to speaker
Referring Expressions
• Drink inherits Common-Noun, a type of
Ref-Expr
• Form is “drink”
• Meaning pole is bound to Drink schema
Referring Expressions
• A-CN-Expr
inherits
Ref-Expr
• Takes a
constituent
• Has form and
an ordering
constraint
• Category bound
to meaning of
com-noun
Referring Expressions
• Drink schema evokes
(refers to) Drink-Action
schema
• Inherits Bounded-Mass
• Is the drink-entity of the
Drink-Action
• Has a Boundary an
instance of Container
schema
• Has a Mass, an
instance of Liquid
schema
Referring Expressions
• Bounded Mass schema inherits Bounded-Thing
• Has two roles, which are constrained to be an
instance of the Boundary and the Substance
schema, respectively
Referring Expressions
Ref-Expr
Common-Noun
Drink
Mary
Me
A-CN-Expr
Predicating Expressions
• Predication: another
major function of
language
• Constructions that
predicate have a
Predication schema
– Overall event
– Particular schemas
– Aspect
– Place, time, etc.
Predicating Expressions
• Predicating expressions are all those that
predicate something of a referring
expression, e.g. the ditransitive construction
• All inherit the Pred-Expr construction
Predicating Expressions
• Tossed, a verb, evokes the predication
schema, although it is not a Pred-Expr
• Verbs must have its schemas role filled
Predicating Expressions
• The tossed construction (assumed stored)
• Predication’s schemas role is a Toss schema
• Aspect is perfect; tense is past
The Semantics of Tossed
• Toss schema involves a transfer of energy
from an energy-source to an energy-sink
• Transfer of force results in location change
The Semantics of Tossed
• Tossed is like other verbs that encode forced motion.
• Combine force transfer, SPG, and Cause-effect
The Semantics of Tossed
•
•
•
•
The toss Schema evokes Forced-Motion
Has tosser (causer) & tossed (trajector & Bounded-Thing)
Its meaning is bound to the action of the fm
Involves low force and means of motion is the Fly schema
The Ditransitive Construction
• The Ditransitive
Encodes
something
different from Toss
- a Transfer
• Transfers: causeeffect relationship
between transfer
of force and
receiving schema
The Ditransitive Construction
• Ditransitive Construction
inherits Pred-Expr
• Has 4 constituents and
assigns case features to 3
• Ordering constraints
• Bindings in the semantics
Constructional analysis
Semantic Specification
The Bigger Picture
• We haven’t talked about:
– Morphology
– Learning
– The analysis process
– Simulation
– Construal (metaphor, metonymy, etc.)
– Neuroscientific and psychological evidence
– The connectionist implementation of ECG
– … and many others
The Bigger Picture
• All sorts of constructions, lexical, phrasal,
etc. can be represented in a unified
formalism
• This includes form, meanings, constructional
attributes, and discourse factors
• It is not only a model of human cognitive
functioning, but is also being used for
natural language understanding applications
The Bigger Picture
• If you have a formal theory of human semantic
representations, these can help drive syntactic
behavior
– Mary can fill the agent constituency because it is a RefExpr that occurs before the verb (with unspecified case)
and whose referent can be a transfer agent
– Tossed can fill the action constituency because it is a
verb in the right sequential position whose schema can
be interpreted as a means of transfer
• Incorporating semantics into grammar is inevitable
if we want to capture syntactic patterning, so we
might as well do it in the most cognitively
motivated way possible.