Eye Movements and Spoken Language Comprehension: effects of visual context on syntactic ambiguity resolution Spivey et al. (2002) Psych 526 Eun-Kyung Lee

Research Question Does referential context affect initial parsing of syntactically ambiguous sentences? When referential context supports less preferred syntactic structure, could it eliminate processing difficulty in early phrases? The role of nonlinguistic factors in sentence processing Garden path model vs. Constraint-based model

Previous Research[1] Limitations Reading time measures restricted to measuring processing difficulty No information about what is being processed how Misleading notion of referential context Not just equated with the preceding linguistic context Salient information in the environment, the set of presuppositions shared by discourse participants

Previous Research[2] Two Paradigms Language-as-action Interactive settings Real-world referents Clear behavioral goals Offline methods Language-as-product Online measures (Response measures time-locked to the linguistic input) Decontextualized input Not goal-directed

Current Study Combines the two paradigms Communication task, well-defined context, clear behavioral goal (Language-as-action) On-line measure of eye-movement (Language-as- product)

Target Sentence A temporarily ambiguous prepositional phrase Put the apple on the towel in the box Preference for a goal argument over an optional adjunct Syntactically simpler (Frazier 1987) General preference for arguments over adjuncts (Abney 1989) Linguistic presupposition of uniqueness associated with a definite noun phrase (Crain & Steedman 1985) Ambiguous region Disambiguating region

Linguistic Presupposition & Referential Context When there is a single entity in the context Modification is redundant  favor argument analysis When there is more than one entity in the context Referential indeterminacy is created Modification is required to establish a unique referent  Multiple-referent contexts eliminate processing difficulty for the otherwise less-preferred modification analysis (Crain & Steedman 1985, Altmann & Steedman 1988)  What if there is no referential indeterminacy in multiple-referent contexts?

Experiment 1

Method 6 participants Listen to a spoken instruction read out from a script Move objects in a visual workspace following the instruction Lightweight headband-mounted eyetracker to monitor the participant’s attentional shifts 3 types of context (one-referent, two-referent, three-and- one referent context) with ambiguous and unambiguous instructions Put the apple on the towel in the box Put the box that’s on the towel in the box 18 experimental, 90 filler instructions in 36 trials (or instruction triplets)

Example of an instruction set Look at the cross Put the apple on the towel in the box Now put the pencil on the other towel Now put it in the box Critical instructions were always the first instruction in the set

3 types of Visual Context [1] One-referent context Single referent If there is a garden path effect, more looks to the empty towel for “on the towel” in the ambiguous instruction compared to the unambiguous instruction

3 types of Visual Context[2] Two-referent context Multiple referents (eliciting referential indeterminacy) whether referential context eliminates garden path effect If a referential account is correct, looks to the incorrect goal should be eliminated in the ambiguous instruction  modifier interpretation

3 types of Visual Context[3] Three-and-one-referent context Multiple referents (eliciting no referential indeterminacy) Whether linguistic presuppositions with definite NPs are used on-line in resolving syntactic ambiguity If yes, looks to the incorrect goal should be eliminated in the ambiguous instruction  modifier interpretation

Results[1] Distractor Object Incorrect Goal

Results[2] One-referent context More frequent saccade (55%) out of the target referent region and into the incorrect goal region in the ambiguous instruction Two-referent context Rare looks at the incorrect goal (14%) in the ambiguous instruction No difference between the ambiguous and unambiguous instructions Three-and-one referent context No significant difference in looks at the incorrect goal between the ambiguous (0%) and unambiguous instructions (22%)  The decision to modify the noun phrase is not purely due to the presence or absence of referential indeterminacy  Reflects on-line access to specific presuppositions associated with definiteness and modification

Results[3] Referential contexts influence an initial interpretation of ambiguous sentences However, Possible confounding effects by some intonational patterns

Experiment 2

Method The same stimuli and instructions as Experiment 1, but with prerecorded instructions 6 participants Ambiguous instructions were digitally converted from the unambiguous versions by editing out “that’s” e.g. Put the apple that’s on the towel in the box  What about the prosodic cues in the critical regions?

Results[1] Parallel results with those of experiment 1

Results[2] Combined Analysis of Exp 1,2 One-Referent Incorrect Goal > Correct Goal Garden Path Effect in the ambi. condition

Results[3] Combined analysis of Exp 1,2 Two-Referent fixation to the distractor referent due to Referential indeterminacy No difference b/w ambi. and unambi. conditions

Results[4] Combined analysis of Exp 1,2 Three & One Referent Fewer fixation to distractor reference Only a few fixation to Incorrect Instrument No difference b/w ambi. and unambi. conditions

Summary Referential contexts play an initial role in parsing (even when the verb takes an obligatory verb argument) The online use of linguistically coded presuppositions even in the absence of referential indeterminacy (Three & one reference context) Supports a constraint-based model of parsing

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