Sentence Comprehension 1
Bottom-up versus top-down models
Bottom-up models
Bottom up models - analyse sentence structure based on information from word classes. Do not take into account contextual factors (e.g. plausibility)
Top-down models
Top-down models - allow for a role of contextual factors (e.g. plausibility) at an early processing stage
Evidence for bottom up processing
The garden path model
Garden path sentences involve temporary mis-analysis of the structure of a sentence.
We are relatively slow to recover.
They are easy to generate and near universal.
(1) Since Jay always jogs a mile and a half seems very short to him.
A mile and a half is misanalysed as the object of jog
(2) The criminal confessed his sins harmed many people
His sins is misanalysed as the object of confessed
Garden paths allow us to see the inbuilt biases of the parser
(parse = analyse a sentence and tag each word according to its word class)
Ambiguity
Arises where there are two possible analyses. Can be local (ambiguity resolved before the end of the sentence), or global (ambiguity remains even after we have read/hear entire sentence)
Where is the ambiguity in these sentences?
The vampires loaned money at low interest rates were told to record their expenses
XXX pleaded guilty to running the brothel at Newcastle Crown Court.
The young athlete realised her potential might one day make her a world class athlete
A bicycle was reported stolen by an old lady
They’re cooking apples.
The following are some tips to protect women from the police department
How do we explain parsing biases?
Biases/heuristics reflect a general drive towards simplicity. Some have suggested that these reflect the innate behaviour of the parser (Frazier, 1987). However, they could also emerge due to processing constraints.
a. Assume local relationships
A bicycle was reported stolen by an old lady = misanalysis involves linking by-phrase to the local verb (stolen)
Vlad figured that Boris wanted to take the pet rat out = particle out linked to local verb take, and not distant verb out.
The horse that chased the boy is big = Here the subject of is is non-local (the horse). However, language-impaired children are overly dependent on this local bias.
b. Assume simple structures (e.g. few nodes and branches)
Since Jay always jogs a mile and a half seems a very short distance to him = A mile and a half is part of a new clause. We resist opening a new clause because it involves a more complex structure
The criminal confessed his sins harmed many people = His sins is part of a new clause. Again, we resist opening a new clause because it involves a more complex structure
The man saw the woman with a telescope = we are more likely to see the telescope as the instrument of seeing ("high-attachment", rather an an object in possession of the woman ("low-attachment"). This instrument reading involves the fewest nodes.
Biases reflect statistical patterns in the input
Vampires loaned money at low interest rates = structure where vampires is object of loan is rare in the input. Therefore we are unlikely to initially assign this structure
The daughter of the colonel [who had an accident] was beautiful = Spanish speakers prefer "high-attachment", where the relative clause (who had an accident) modifies the daughter, and not the colonel. English speakers do not have this bias. This is likely to reflect statistica properties of the language
Evidence for top-down processing
What factors can be classified as "top down"
When referring to top-down processing we are typically referring to
Lexical factors
Contextual factors
Role of lexical content
Words clearly bias structural interpretation:
The man hit the woman with the _
The boy tempted the mouse with the _
The protestor splattered the policeman with __
The boy likes the girl with _
The young athlete realised/thought her potential might one day make her a world class athlete
Trueswell et al. (1983) - measured reading via a self-paced reading paradigm. Found that
(a) Participants used the verb to predict the structure of the sentence. Where the structure was less predictable, processing slowed down
(b) Participants used subordinator that to disambiguate structure. This led to shorter reading times.
Discourse context
Can you understand this sentence?
The horse raced past the barn fell.
Now let's put it in context...
Lord Chumley-Worthington wanted to map out a race course around his estate. He therefore wanted to find out if the ground was more slippery next to the barn or next to the pond. So he instructed his servants to race two horses along these different routes. The horse raced past the barn fell, while the horse raced past the pond managed to stay on its feet. He therefore conluded that the ground next to the barn was more slippery.
Referential processing
According to theories of referential processing, set-restriction is a costly process. We therefore avoid where possible
The vampires loaned money at low interest rates were told to record their expenses = correct interpretation involves set restriction (we imagine a large group of vampires, and then restrict this set to those who were loaned money)
The man saw the woman with the binoculars = low-attachment (dispreferred) reading involves set-restriction (we imagine a group of women and restrict this set to the woman who had the binoculars)
I've grouped this under "top down" theories because it is related to semantic interpretation.
So which account is correct?
Garden paths are easy to generate under laboratory conditions, suggesting that we rapidly make decisions about sentence structure. However, top down effects have been repeatedly demonstrated. Possible positions
Both bottom-up and top-down factors are operative at once.
Bottom-up processing slightly precedes top-down processing.
Sentence processing in clinical populations
There is some evidence that language-impaired children may prioritise top-down factors, e.g. animacy.
The rock that the boy dropped was heavy
Children know that it is more likely for a boy to drop a rock than for a rock to drop a boy.
MORE ON THIS NEXT WEEK
Homework
Read the following sentence
"No head injury is too trivial to ignore"
Does it make sense to you? Can you paraphrase is? Is there anythin weird about it?
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