Sentence Processing 2

08/03/2016

LCSD56 Psycholinguistics Sentence Processing 2

Processes | Nature of a Sentence | Methods | SP happens at once or gradually unfolds? | Is it Modular or Interactive? Now, qn.2: How do the processes interact in sentence comprehension? • Is the process of comprehension modular? – i.e. separate sub‐processors analyse lexical, syntactic and semantic information. This semantic information cannot influence lexical and syntactic analysis of sentence even if word or syntax is ambiguous

– Harley: “two‐stage/autonomous” model (see next)

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– Harley: “two‐stage/autonomous” model • First stage: only syntactic information to construct syntactic representation of sentence • Second stage: semantic information allowed to help • Hence question about number of stages in sentence processing is same question as whether or not parsing is modular (autonomous) or interactive

Processes | Nature of a Sentence | Methods | SP happens at once or gradually unfolds? | Is it Modular or Interactive? Now, qn.2: How do the processes interact in sentence comprehension? • OR is it interactive? – i.e. resolution of lexical or syntactic ambiguity is achieved with all processors/information working together – semantic (and contextual – linguistic or non‐ linguistic) information can be used to guide lexical access and syntactic analysis – Harley: “one‐stage/interactive” model

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Addressing the question of modularity

• Ambiguity is one way to address this question.

• Remember there are 2 types of ambiguity – Lexical ambiguity – Syntactic ambiguity

• We will explore the question of modularity and its relationship to each type of ambiguity

David Swinney experiment: Stimuli

Context Ambiguity Condition

Ambiguous Unambiguous

No context Rumor had it that for years the Rumor had it that for years the government building had been government building had been plagued with problems. The plagued with problems. The man man was not surprised when was not surprised when he found he found several bugs in the several insects in the corner of his corner of his room. room.

Biasing context Rumor had it that for years the Rumor had it that for years the government building had been government building had been plagued with problems. The plagued with problems. The man man was not surprised when was not surprised when he found he found several spiders, several spiders, roaches, and roaches, and other bugs in the other insects in the corner of his corner of his room. room.

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Is initial lexical access modular? Swinney experiment (ambiguous condition)  task: listen to spoken sentences, watch for “. . Theword/nonword strings (presented visually). man was not surprised when he found several or or or bugs | ~200 msec in SPY ANT PEN WID the corner | ~700 msec of his room“ at 200 msec (just after word presented), both SPY and ANT faster than PEN at 700 msec (three syllables after ambiguous word), only ANT is faster than PEN

Logic of the Swinney experiment

• Remember that semantic priming effect = oFaster lexical decision times when word is related to something that came before (nurse is faster after doctor than after pen)

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Logic of the Swinney experiment

• Swinney used this effect to test which meanings of the word "bugs" are active oIf the insect meaning is active then responses to "ant" should be faster than for "spy" or “pen" oIf both meanings are active then "ant" and "spy" should be faster than “pen" o Found that both meanings were active (at 200 msec) even in the presence of biasing context.

Logic of the Swinney experiment (cont.)

• But how long does this effect last? – at 200 msec, both SPY and ANT faster than PEN (so: both meanings of homophone “bug” accessed) – at 700 msec, only ANT is faster than PEN (so: even if both meanings accessed, there is rapid selection of appropriate meaning)

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Logic of the Swinney experiment (cont.)

• Conclusion? – Strong evidence for initial lexical access as independent of (sentence) semantic context (modular)

So is initial lexical access strictly modular? • Other studies have shown that this may not be necessarily so • Actually, two factors determine if initial lexical access for ambiguous words is selective or multiple – Strength of context (which Swinney looked at) – Meaning dominance (which S didn’t look at directly)

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Strength of Context

• = How strongly does the sentence context suggest a particular meaning of the ambiguous word? –See Swinney experiment for example on how to test this

Meaning Dominance

• = Relative frequency of each meaning of an ambiguous word – Equibiased word: an ambiguous word whose different meanings are equally frequent (e.g. pitcher – neither meaning used a great deal more than the other) – Non‐equibiased word: an ambiguous word which has one meaning that is more frequent than its others (e.g. bank – ‘financial inst.’ meaning more frequent)

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Initial lexical access can be both modular and interactive? Duffy study

EXPERIMENTAL CONDITIONS (AND SAMPLE STIMULI)

Context occurs before ambiguous word (strength of context: √) Equibiased condition Because it was kept on the back of a high shelf, the pitcher was often forgotten. Control (unambiguous word) Because it was kept on the back of a high shelf, the whiskey was often forgotten.

Non-equibiased condition When she finally served it to her guests, the port was a great success. (Less frequent meaning always intended in non-equibiased condition) Control When she finally served it to her guests, the soup was a great success.

Context occurs after ambiguous word (strength of context: X) Equibiased condition Of course the pitcher was often forgotten because it was kept on the back of a high shelf. Control Of course the whiskey was often forgotten because it was kept on the back of a high shelf.

Non-equibiased condition Last night the port was a great success when she finally served it to her guests. Control Last night the soup was a great success when she finally served it to her guests.

Initial lexical access can be both modular and interactive? Duffy study EXPERIMENTAL CONDITIONS (AND SAMPLE STIMULI)

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Initial lexical access can be both modular and interactive? Duffy study EXPERIMENTAL CONDITIONS (AND SAMPLE STIMULI)

Non-equibiased condition Last night the port was a great success when she finally served it to her guests. Control Last night the soup was a great success when she finally served it to her guests.

Duffy study: results

• Method: Eye movement tracking (assumption: the longer you look at something, the more meanings you are processing/the more difficult the processing

Context before Context after ambiguous ambiguous word word (i.e. no context)

Equibiased Time spent on ambiguous Time spent on ambiguous word word (‘pitcher’) relative to relative to control: significantly more. control: no difference. Suggests both meanings activated Suggests context allowed subject to activate only relevant meaning Non- Time spent on ambiguous Time spent on ambiguous word equibiased word (‘port’) relative to relative to control: no difference. control: significantly more. Suggests only more frequent Suggests context could not meaning activated. (but note that suppress most frequent more time spent on words after meaning. ambiguous word, i.e. when reader got to ‘served it to her guests’)

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So is initial lexical access modular?

• Swinney found that semantic context cannot influence initial lexical access but can play a role a short time after. – However, Swinney used equibiased words only, and therefore not possible to tell if relative frequency of the different meanings could play a role in determining level of interactivity. • Duffy compared equibiased and non‐ equibiased ambiguous words and found that: – semantic context can influence initial lexical access but only when the semantic context strongly constrains which meaning is correct (i.e only for equibiased words). – – BUT even this is limited –when the word is non‐equibiased the more dominant meaning cannot help but be activated even when the non‐ dominant meaning is intended

So is initial lexical access modular?

• Duffy compared equibiased and non‐equibiased ambiguous words and found that (cont): – When no context, equibiased words activate all possible meanings; non‐equibiased words activate only the more frequent meaning. – I.E. frequency of meaning/meaning dominance can also play a role in determining whether access is modular or not. • Weber (2012) found similar findings as Duffy in a different experiment – See Weber, Andrea; Crocker, Matthew W. (2012). On the Nature of Semantic Constraints on Lexical Access. Journal of Psycholinguistic Research, v41 n3 p195‐214

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So is initial lexical access modular (cont.)? • Findings: – Equibiased words: initial access is modular (Swinney); access is non‐modular when context is strong (Duffy)

– Non‐equibiased words: access is modular (Duffy)

• So on the whole initial lexical access within a sentence is mainly modular (given many words are non‐equibiased)

Is syntactic parsing modular?

• So if initial lexical access is mainly modular, what about syntactic parsing? Before answering this, let’s consider a couple of principles that have been suggested to guide syntactic parsing.

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Is syntactic parsing modular?

• Frazier & colleagues (1982, 1983, 1987) have suggested that initial syntactic parsing is guided by the principle to keep things as simple as possible to minimise cognitive load. Strategies people are said to use in order to do this are: – Minimal attachment – Late closure

• This is known as the ‘garden path’ theory of sentence processing, which tries to account also for how readers process temporarily ambiguous sentences

Consider the sentence

The girl hit the man with the umbrella.

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Parsing principle 1: Minimal Attachment (MA)

• MA: The girl hit the man with the umbrella Construct simplest  2 options here possible A Analyse as the girl hitting with the syntactic umbrella B. Analyse as man holding the structure. umbrella Option A is simplest in terms of tree structure. Minimal attachment requires that readers initially pursue analysis A.

Parsing preferences: minimal attachment S

8 Nodes NP VP Preferred the girl V NP

S hit NP PP NP VP the man P NP the girl V NP PP with the umbrella

hit the man P NP

with the umbrella 9 nodes The girl hit the man with the umbrella. Dispreferred

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Consider this sentence:

When John jogs a mile seems a long distance.

Parsing Principle 2: Late Closure (LC)

• LC:  When John jogs a mile seems a long distance. Incorporat  When John jogs, a mile seems a long distance.

e new  2 options here information A Analyse as argument of current verb- as part of phrase. current B Analyse as beginning of new clause. phrase Late closure requires that readers whenever initially pursue option A. possible

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Is initial syntactic parsing modular?

• The Garden Path theory says that initial syntactic parsing is not influenced by word meaning or sentence context • In other words: if late closure and minimal attachment can be shown to be the general strategies people use when parsing an ambiguous sentence – no matter what the context –then this is evidence for a modular syntactic system

Q: Who’s doing the examining?

• The evidence examined … • The defendant examined …

• How did you treat each noun? • Did you treat the defendant as ‘the person who examined something’ or ‘person who was examined by someone’? • Did you treat the evidence as ‘the thing that examined something’ or ‘the thing that was examined by someone’’? • If you did the above, then you were using your knowledge about word meanings…

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Syntactic ambiguity and modularity: the role of lexical knowledge Point 1: Does knowledge about word meanings influence initial decisions about sentence structure?

The defendant examined . . . The evidence examined . . .

Example of stimuli used to examine role of lexical knowledge in parsing ambiguous sentences

 The defendant examined by the lawyer was unreliable.

temporarily ambiguous word disambiguating phrase

 Word examined is temporarily ambiguous between 2 readings. 1. Defendant examined someone 2. The defendant was examined by someone.

 Minimal attachment favours reading 1.  Disambiguated as reading 2 on encountering by the lawyer.  Therefore, readers should experience difficulty when reading disambiguating phrase (by the lawyer).

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Example of stimuli.. (Trueswell et al., 1994)

The evidence examined by the lawyer was unreliable.

temporarily “ambiguous” word disambiguating phrase

Following previous example, word examined is temporarily ambiguous between 2 readings. 1. Evidence examined someone (MA ) 2. The evidence was examined by someone.  However, readers know (word knowledge) that inanimate nouns like evidence cannot examine things.  Does knowledge disambiguate structural decision prior to reading by the lawyer?  Do readers experience difficulty reading by the lawyer?

What they did…

Trueswell et al. (1994) Monitored eye movements as subjects read sentence which: • Were temporarily (structurally) ambiguous or unambiguous. • Contained animate (e.g. defendant) or inanimate (e.g. evidence) subjects of sentence. • Trueswell et al. were interested in initial parsing decisions, so measured first pass reading time for regions of sentence.

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What they found…

Animate condition The defendant examined by the lawyer was unreliable. AMB

The defendant who was examined by the lawyer was unreliable. UNAMB

Inanimate condition The evidence examined by the lawyer was unreliable. ”AMB” The evidence that was examined by the lawyer was unreliable. UNAMB

 Trueswell et al. (1994) found longer first pass reading time for disambiguating phrase of sentences with animate subjects.  No difference in first pass reading time for disambiguating phrase of sentences with inanimate subjects.  Therefore, knowledge about word meaning influenced initial parsing decisions.

Modularity and syntactic ambiguity: The role of contextual* knowledge

Point 2: Does contextual knowledge influence initial parsing decisions?  Altmann, Garnham & Dennis  Eye movement monitored as subjects read  Temporarily ambiguous & unambiguous sentences.  With context & without context.

He told the woman that he had risked his life for to install a smoke detector.

temporarily ambiguous phrase disambiguating phrase

He asked the woman that he had risked his life for to install a smoke detector. (unambiguous)

Finding: Without context, subjects had longer first pass reading time for to install in ambiguous than unambiguous sentences. (Probably expecting something like “He told the woman that he had risked his life for nothing..”)

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Context An off‐duty fireman was talking to two women. He was telling themParsing how syntactically serious the situation ambiguous had been sentence when their with house prior had caught fire. The fireman hadcontext risked his life to rescue one of the women while the other had waited outside.

He told the woman that he had risked his life for to install a smoke detector.

With context, there was no difference in first pass reading time. Therefore, contextual knowledge influences initial parsing decisions.

Revision: Overview of sentence processing • Processes involved in understanding speech • The nature of the sentence • How psycholinguists study sentence processing: off‐line vs. on‐line methods – The use of ambiguous sentences to help understand sentence processing (visual rather than auditory) • Important questions about sentence processing: 1. Does comprehension of the sentence happen all at once, or does comprehension gradually unfold? 2. Is sentence processing a modular process? • Lexical ambiguity –is its resolution influenced by semantic context? • Syntactic ambiguity –is its resolution influenced by (i) lexical knowledge and/or (ii) context?

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What can we say about Q1?

• Is sentence processed as we go along, or only after we have heard whole sentence? – Evidence from parsing studies of both written and spoken sentences suggests that immediacy of interpretation is general rule of our system

What can we say about Q2?

• Is lexical access when processing a sentence modular or interactive? – Seems largely modular, although frequency of meaning can determine to a limited degree whether sentence context influences initial lexical access (see Swinney and Duffy studies)

• Is syntactic parsing modular or interactive? – Processors work mostly with bottom‐up information, but not exclusively so. When prior sentence or visual information permits, we can use word knowledge and context to help guide our syntactic parsing –i.e. sentence processing is sensitive to context to a limited degree

–  MA or LC was not always the default way of parsing a sentence (see Garden Path theory)

– No evidence for strong modular theory, although a weaker one not completely ruled out

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Sources

• Berko‐Gleason, J. and Bernstein Rather, N (eds.) (1998). Psycholinguistics (2nd ed.). Orlando: Harcourt Brace. Ch 5. • Aitchison, Jean (1976). The Articulate Mammal. New York: McGraw Hill. Ch 10. An easy introduction –if you can get a newer edition, try to read that instead. • Steinberg, Danny (1993). An Introduction to Psycholinguistics. London: Longman. Ch. 5 & 6. • Whitney, Paul. Chapter 7 • For classic experiments: http://step.psy.cmu.edu/scripts/index.html • www.biols.susx.ac.uk/Home/ Alan_Garnham/Teaching/LTM/sentproc.ppt • http://www‐hcs.derby.ac.uk/psychology/currentinfo.htm#level2 • www.psych.ufl.edu/~fischler/CP/CP_lang2_post.PPT