Transcript Understanding Sentences - Trinity College, Dublin

Understanding Sentences
Two steps back: What is linguistic
knowledge?
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Phonological
Syntactical
Morphological
Lexical
Semantic
One step back: What is a sentence?
• (part of) an utterance?
• Meaningful unit?
• Grammatical structure containing at least
a subject and a verb?
• Working assumption: A well-formed
structure built from syntactical units.
Syntactical “units”
• XP → (Spec) X’ YP*
• From phrase to sentence:
– Inflection / IP (INFL)
– Complementizer / CP
• Special role of verb arguments
• i.e. Sentence: CP that satisfies the verb
arguments.
Argument structure of verbs
• Pattern of thematic roles - who is doing
what to whom
– Agent
• Entity that instigates an action
– Theme / Patient
• The thing that is being acted on or being moved
– Recipient
understanding
• The dog likes ice cream.
– [det the
– NP[det the Ndog]
– NP[det the Ndog] [Vlikes
– S[NP[detthe Ndog] VP[Vlikes NP[Nicecream]]]
• Basic assumption
– One structure built up at a time
complexity
• The dog the stick the fire burned beat bit
the cat.
• The dog that the stick that the fire burned
beat bit the cat.
vs.
• The cheese that some rats I saw were
trying to eat turned out to be rancid.
Time Flies
• The plastic
– …rose.
– …rose and fell.
• The plastic pencil marks
– …were ugly.
– …very clearly.
• My son has grown another foot.
• Time flies like an arrow.
• Ergo: Human parsing is also based on decision
making skills. The brain is not a computer
(although it does computations all the time)!
Up the garden path
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The horse raced past the barn fell.
The horse raced.
The horse raced past the barn.
The horse race past the barn. fell.
• But:
• The landmine buried in the sand exploded.
Functional Logic
• Minimal attachment
– Prefer the structure with the lower number of
nodes.
• Late closure
– Add to the current structure as long as
possible.
Schematic of Speech Processing
Language and the brain
articulation
Post-lexical
phonological
encoding
Lexeme access
+ 125 ms
monitoring
+ 200 ms
Concept-based
lexical selection
275 ms
Pinker 1994, 308
How to locate language in the brain?
• Brain damages
• EEG – Electro-Encephalogram
– ERPs – Event related brain potentials
• PET – Positron Emission Tomography
• fMRI – functional Magnetic Resonance
Imaging
• MEG – Magneto-Encephalography
Forms of Aphasia
Pinker 1994, 307
Broca’s Aphasia
• Syntactic processing impaired, not always
completely gone
• The car pushes the truck
• The car is pushed by the truck
• Motor-control not affected
• Blowing out candles remains possible
• Writing impaired, but not handling objects
• Visuo-spatial abilities not affected
– Evidence from sign language speakers:
• Left-hemispheric damage resembles Broca’s aphasics
• Right hemispheric damage impairs visuo-spatial tasks as e.g.
copying patterns, recognizing faces
• Lasting aphasia results from deeper injuries!
Pinker 1994, 310
Wernicke’s Aphasia
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Fluent speech
Producing grammatical speech
Problems in naming objects
High proportion of set phrases
(severe) problems in comprehending
speech
Other aphasic syndromes
• Anomia
• Story: “boy falling from a stool as he reaches into a jar on a shelf and hands
a cookie to his sister”
– Lesion in Wernicke’s and adjacent areas
– Close to regions for processing visual, auditory, bodily sensations
– Words and meaning separated by lesion?
• Connection between Broca and Wernicke regions disrupted
(centralised aphasia):
– Sentence repetition impaired
• Broca and Wernicke regions seperated from surrounding area
(transcortical aphasia)
– Sentence repetition without problems
– Hardly any spontaneous speech
– Strong difficulties in speech comprehension