Language, brain and representation

1
Language, brain and representation

• Aspects of linguistic competence

2
Language

• The most complex of human artifacts?

3
Three ways of viewing a language

• An internalized body of tacit knowledge (the
  I language Chomsky)
• A social construction or set of conventions
  shared by a language community.
• A natural object out there in the real world.
• Which of these three perspectives on language is
  most relevant for our purposes?

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Objectives of this module

• To specify the contents of an I-grammar.
• To specify what linguistics expressions are
  composed of
• The nature of word classes and phrase structure
• The recursive nature of grammatical rules that
  underlie the generative power of human languages
• The levels of organization that are found in
  natural languages?
• To give a hint of how linguistic forms map onto
  meanings.

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From the I-Language perspective

• The personal knowledge base that each speaker of
  the language carries around in his/her head.
• How can we access this knowledge?
• Introspection?
• Grammatical judgement?
• A grammar should generate all and only the
  grammatical sentences of a language Chomsky.
• The problem of subjectivity.
• The structuralist alternative to the
  Internalist view 19th 20th century
  Linguistic Science

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From a structural linguists standpoint

• Linguistic structures are objects out there in
  the real world of language usage.
• The structures that linguists discover are
  revealed in patterns of language usage habitual
  collocations of phrases, words and sounds that
  form nested patterns of sequential statistical
  dependencies. (Bybee, 2002)
• Our brains are sensitive analyzers of sequential
  patterns of language input and output.
• We react quickly very to departures from expected
  sequences in the stream of spoken or written
  language.
• quickly very !
• This is the basis for syntactic anomaly
  detection, a technique that may be used to assess
  grammatical disorders or non-native competency.

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Linguistic structures are only indirectly related
to meaning.

• Major word classes (noun, verb, etc.) cannot be
  satisfactorily defined notionally, but only in
  terms of their formal (distributional)
  properties.
• Some grammatical morphemes bear an obvious (but
  imperfect) relationship to meaning categories
• He looked unwell.
• but others, e.g. agreement do not
• He looks unwell. vs. They look unwell.
• Is there a reason for this degree of independence
  of structure from meaning in natural language?

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Independence of form and meaning in natural
language.

• Guarantees that syntactic structures may be
  retrieved from distributional analysis of
  language input by stochastic algorithm by
  sequential learning mechanisms.
• An important insight from Structural Linguistics
  (Zellig Harris et al. 1940s-60), rejected by
  Chomsky (1957), revived in the 1980s by
  Connectionists (Rumelhart McClelland, PDP 1987,
  Elman, 1986).

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Is the meaning of a sentence fully determined by
its (syntactic) form and (lexical) content?

• Consider how the reference of he changes in 1.
  and 2.
• The teacher refused the pupils request because
  he was naughty.
• The teacher refused the pupils request because
  he was busy.
• What determines who he refers to?

10
Pragmatics knowledge of the world.

• Plays an important role in assigning meaning to
  linguistic expressions.
• In the previous example
• naughty applies only to subordinates. Hence,
  the reading hepupil is favoured. A lexically
  mandated reading.
• busy pragmatically more likely a property of
  teacher than pupil, but not lexically mandated.

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How to define word classes

• What is a noun, verb, adjective?
• Notional vs distributional definitions of word
  classes.

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The advantage of a distributional approach to the
definition of word classes

• Provides a secure foundation for discovering or
  inductively learning the syntactic structures of
  any given language.
• The downside of the distributional over the
  notional approach to defining word classes is
  that it complicates the mapping from sounds and
  words to sentence meanings in linguistic
  expressions.

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Two exceptions to the indirect mapping between
sound and meaning

• Heuristic sentence processing,
• Direct mapping of form to meaning.

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Heuristic sentence processing strategies

• May be used by the less than fully competent
  speaker/listeners to map sentence form to
  meaning.
• The agent first strategy
• The cat chased the mouse.
• The mouse was chased by the cat.
• agent patient

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Heuristics

• Over-simplified parsing strategies.
• Fail on many complex sentences.
• A kind of coping strategy?
• Jakobsons theory of aphasia.

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Direct mapping from form to meaning the lexical
route.

• Used for word meaning and idioms.
• John kicked the bucket.
• This sentence is ambiguous
• ltJohn died.gt
• ltJohn kicked the bucketgt
• Which reading do you access first?

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The lexicon

• An encyclopaedic store of form-meaning pairings.
• ...break the ice
• ...let the cat out of the bag
• Thats the way the cookie crumbles.
• May be smaller than a word
• ... unwanted ...

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Minimal design features of a language

• A vocabulary (a lexicon) and a set of combinatory
  rules for combining words into well-formed
  expressions (sentences).
• natural (human) languages require us to recognize
  multiple levels of units.
• How many levels?

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Charles Hockett

• Double articulation of sound and meaning.
• Requires 4 levels of representation in human
  languages
• Phonemes, morphemes, words, sentences.

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Linguistic expressions
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Phonological representationat the segmental
level
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Phonological representationat the word level
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Phonological representationat the phrase level
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Components of meaning categories of grammar
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Thematic roles