What Is the Context for Contextual Vocabulary Acquisition

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What Is the Context forContextual Vocabulary
Acquisition?

• William J. Rapaport
• Department of Computer Science Engineering
• Department of Philosophy
• Center for Cognitive Science
• NSF ROLE Grant REC-0106338

2
Outline

• People can figure out a meaning for a word from
  context
• What does context mean in this context?

3
Definition of CVA

• Contextual Vocabulary Acquisition def
• the acquisition of word meanings from text
• incidental
• deliberate
• by reasoning about
• contextual cues
• background knowledge
• Including prior word-meaning hypotheses, language
  knowledge
• without external sources of help
• no dictionaries
• no people

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CVA From Algorithm to Curriculum

• Computational theory of CVA
• Based on
• algorithms developed by Karen Ehrlich (1995)
• verbal protocols (case studies)
• Implemented in a semantic-network-based
• knowledge-representation reasoning system
• SNePS (Stuart C. Shapiro colleagues)
• Educational curriculum to teach CVA
• Based on our algorithms protocols
• To improve vocabulary reading comprehension
• Joint work with Michael Kibby
• Center for Literacy Reading
  Instruction

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People Do Incidental CVA

• We know more words than explicitly taught
• Average high-school grad knows 45K words
• ? learned 2.5K words/year (over 18 yrs.)
• But only taught 400/school-year
• 4800 in 12 years of school ( 10 of total)
• ? Most word meanings learned from context
• incidentally (unconsciously)
• How?

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People Also Do Deliberate CVA

• Youre reading
• You understand everything you read, until
• You come across a new word
• Not in dictionary
• No one to ask
• So, you try to figure out its meaning from
  context
• How?
• guess? derive? infer? deduce? educe? construct?
  predict?
• our answer Compute it! Via inferential search
  of context/KB
• But what KB?

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CVA as Cognitive Science

• Studied in
• AI / computational linguistics
• Psychology
• Child-language development (L1 acquisition)
• L2 acquisition (e.g., ESL)
• Reading education (vocabulary development)
• Thus far multi-disciplinary
• Not yet inter-disciplinary!

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What does brachet mean?

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(From Malorys 15th century Morte dArthur page
in brackets)

• There came a white hart running into the hall
  with a white brachet next to him, and thirty
  couples of black hounds came running after them.
  66
• People brachet animal? inanimate object?
  dont know.
• Computer brachet physical object
• (because only physical objects have color)
• As the hart went by the sideboard, the white
  brachet bit him. 66
• People brachet animal
• Computer brachet animal
• (because only animals bite)

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Malory, continued

• 3. The knight arose, took up the brachet and
  rode away with the brachet. 66
• People brachet animal / small animal
• Computer brachet small animal
• (because picked up and carried)
• 4. A lady came in and cried aloud to King
  Arthur, Sire, the brachet is mine. 66
• People brachet pet / small, valuable animal
• Computer brachet small, valuable animal
• (because whats wanted is valuable)

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Malory, continued

• There was the white brachet which bayed at him
  fast. 72
• People brachet dog
• Computer brachet hound (i.e., dog that hunts)
• (because only hounds, which are hunting dogs,
  bay)
• The hart lay dead a brachet was biting on his
  throat, and other hounds came behind. 86
• People brachet hound
• Computer brachet hound (i.e., dog that hunts)
• (because x and other y ? x is a y)

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How (Not) to Teach CVAVague Strategies

• Clarke Nation 1980 a strategy (algorithm)
• Look at word context determine POS
• Look at grammatical context
• E.g., who does what to whom?
• Look at wider context
• E.g., for clues re causal, temporal,
  class-membership, etc.
• Guess the word check your guess

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Vague strategies

• guess the word
• then a miracle occurs
• Surely,
• we computer scientists
• can be more explicit!

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A More Precise, Teachable Algorithm

• Treat guess as a procedure call
• Fill in the details with our algorithm
• Convert the algorithm into a curriculum
• To enhance students abilities to use deliberate
• CVA strategies

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Figure out meaning of word from what?

• context (i.e., the text)?
• Werner Kaplan 52, McKeown 85, Schatz Baldwin
  86
• context and readers background knowledge?
• Granger 77, Sternberg 83, Hastings 94
• context including background knowledge?
• Nation Coady 88, Graesser Bower 90
• Note
• context text ? context is external to
  readers mind
• Could also be spoken/visual/situative (still
  external)
• background knowledge internal to readers
  mind
• What is (or should be) the context for CVA?

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Some Proposed Preliminary Definitions(to extract
order out of confusion)

• Unknown word for a reader def
• Word or phrase that reader has never seen before
• Or only has vague idea of its meaning
• Different levels of knowing meaning of word
• Notation X

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Proposed preliminary definitions

• Text def
• (written) passage
• containing X
• single phrase or sentence several paragraphs

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Proposed preliminary definitions

• Co-text of X in some text def
• The entire text minus X i.e., entire text
  surrounding X
• E.g., if X brachet, and text
• There came a white hart running into the hall
  with a white brachet next to him, and thirty
  couples of black hounds came running after them.
• Then Xs co-text in this text
• There came a white hart running into the hall
  with a white ______ next to him, and thirty
  couples of black hounds came running after them.
• Cf. cloze tests in psychology
• But, in CVA, reader seeks meaning or definition
• NOT a missing word or synonym Theres no
  correct answer!
• Co-text is what many mean by context
• BUT they shouldnt!

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Proposed preliminary definitions

• The readers prior knowledge def
• the knowledge that the reader has when s/he
  begins to read the text
• and is able to recall as needed while reading
• knight picks up carries brachet ?? small
• Warnings
• knowledge ? truth
• so, prior beliefs is better
• prior vs. background vs. world, etc.
• See next slide!

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Proposed preliminary definitions

• Possible synonyms for prior knowledge,
• each with different connotation
• Background knowledge
• Can use for information that author assumes
  reader to have
• World knowledge
• General factual knowledge about things other than
  the texts topic
• Domain knowledge
• Specialized, subject-specific knowledge about the
  texts topic
• Commonsense knowledge
• Knowledge everyone has
• E.g., CYC, cultural literacy (Hirsch)
• These overlap
• PK should include some CSK, might include some DK
• BK might include much DK

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Steps towards aProper Definition of Context

• Step 1
• The context of X for a reader def
• The co-text of X
• the readers prior knowledge
• Both are needed!
• After reading
• the white brachet bit the hart in the buttock
• most subjects infer that brachets are (probably)
  animals, from
• That text, plus
• Available PK premise If x bites y, then x is
  (probably) an animal.
• Inference is not an enthymeme! (because )

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Proper definition of context

• But (inference not an enthymeme because)
• When you read, you internalize the text
• You bring it into your mind
• Gärdenfors 1997, 1999 Jackendoff 2002
• This internalized text is more important than
  the actual words on paper
• Text Im going to put the cat out
• Misread as Im going to put the car out
• leads to different understanding of the text
• What matters is what the reader thinks the text
  is,
• Not what the text actually is
• Therefore

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Proper definition of context

• Step 2
• The context of X for a reader def
• A single KB, consisting of
• The readers internalized co-text of X
• the readers prior knowledge

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Proper definition of context

• But What is ?
• Not mere conjunction or union!
• Active readers make inferences while reading.
• From text a white brachet
• prior commonsense knowledge only physical
  objects have color,
• reader might infer that brachets are physical
  objects
• From The knight took up the brachet and rode
  away with the brachet.
• prior commonsense knowledge about size,
• reader might infer that brachet is small enough
  to be carried
• Whole gt S parts
• inference from internalized text PK ? new
  info not in text or in PK
• I.e., you can learn from reading!

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Proper definition of context

• But Whole lt S parts!
• Reader can learn that some prior beliefs were
  mistaken
• Or reader can decide that text is mistaken
  (less likely)
• Reading CVA need belief revision!
• operation
• input PK internalized co-text
• output belief-revised integration of input,
  via
• Expansion
• addition of new beliefs from ICT into PK, plus
  new inferences
• Revision
• retraction of inconsistent prior beliefs together
  with inferences from them
• Consolidation
• eliminate further inconsistencies

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Prior Knowledge
Text
PK1 PK2 PK3 PK4
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Prior Knowledge
Text
T1
PK1 PK2 PK3 PK4
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Integrated KB
Text
T1
internalization
PK1 PK2 PK3 PK4
I(T1)
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B-R Integrated KB
Text
T1
internalization
PK1 PK2 PK3 PK4
I(T1)
inference
P5
30
B-R Integrated KB
Text
T1
internalization
PK1 PK2 PK3 PK4
I(T1)
T2
inference
P5
I(T2)
P6
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B-R Integrated KB
Text
T1
internalization
PK1 PK2 PK3 PK4
I(T1)
T2
inference
T3
P5
I(T2)
P6
I(T3)
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B-R Integrated KB
Text
T1
internalization
PK1 PK2 PK3 PK4
I(T1)
T2
inference
T3
P5
I(T2)
P6
I(T3)
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Note All contextual reasoning is done in this
context
B-R Integrated KB
Text
T1
internalization
PK1 PK2 PK3 PK4
P7
I(T1)
T2
inference
T3
P5
I(T2)
P6
I(T3)
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Proper definition of context

• One more detail X needs to be internalized
• Context is a 3-place relation among
• Reader, word, and text
• Final(?) def.
• Let T be a text
• Let R be a reader of T
• Let X be a word in T (that is unknown to R)
• Let T-X be Xs co-text in T.
• Then
• The context that R should use to hypothesize a
  meaning for Rs internalization of X as it occurs
  in T def
• The belief-revised integration of Rs prior
  knowledge with Rs internalization of T-X.

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This definition agrees with

• Cognitive-science reading-theoretic views of
  text understanding
• Schank 1982, Rumelhart 1985, etc.
• KRR techniques for text understanding
• Readers mind modeled by KB of prior knowledge
• Expressed in KR language (for us SNePS)
• Computational cognitive agent reads the text,
• integrating text info into its KB, and
• making inferences performing belief revision
  along the way
• When asked to define a word,
• Agent deductively searches this single,
  integrated KB for information to fill slots of a
  definition frame
• Agents context for CVA this single,
  integrated KB

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Distinguishing Prior Knowledge from Integrated
Co-Text

• So KB can be disentangled as needed for belief
  revision or to control inference
• Each proposition in the single, integrated KB is
  marked with its source
• Originally from PK
• Originally from text
• Inferred
• Sources of premises

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Some Open Questions

• Roles of spoken/visual/situative contexts
• Relation of CVA context to formal theories of
  context (e.g., McCarthy, Guha)
• Relation of I(T) to prior-KB e.g.
• Is I(Ti) true in prior-KB?
• It is accepted pro tem.
• Is I(T) a subcontext of pKB or B-R KB?
• How to activate relevant prior knowledge.
• Etc.

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Summary

• People can figure out a meaning for a word from
  context, where
• Context belief-revised integration of
• readers prior knowledge, with
• internalized information from the text
• This clearer concept of relevant notion of
  context will help us
• evaluate other research
• develop our curriculum