Misinterpretation of Garden-Path Sentences: Implications for Models of Sentence Processing and Reanalysis by Ferreira et al. Kate Kokhan Department of Linguistics University of Illinois at Urbana-Champaign

Outline What is a garden-path sentence? Motivation for the research by Ferreira et al. Description of the experiments and the findings Implications for reanalysis: Fodor and Inoue (1998)

What is a garden-path sentence? A garden path sentence is a grammatically correct sentence that starts in such a way that a reader's most likely interpretation is an incorrect one, luring him initially into an improper parse that then turns out to be a dead end. The "garden path" is a reference to the saying "to be led down the garden path", meaning "to be misled.“

Motivation for the research Previous work on how garden-path sentences are processed had barely addressed how these sentences are actually understood. No data on the question of whether people understand these sentences the way we presume they should.

Motivation of the research General goal was “to discover how people understand language” Many studies showed that people had problem understanding some sentences (if they are presented visually without punctuation): While Anna dressed the baby spit up on the bed. The baby is the object of dressed When they encounter spit up => error

Models of reanalysis Goal of all models of reanalysis is to describe and motivate the mechanisms used by the parser to detect errors, deduce useful information about the nature of the necessary repair from those errors, and ultimately to create successful parse. Is reanalysis always successful? – No => Another goal of models of reanalysis is to explain why it is that successful revision is possible for some sentences but impossible for others.

What does influence the ease of reanalysis? Ferreira & Henderson (1991, 1998) => While Anna dressed the baby that was small and cute spit up on the bed. the error signal the head of the misanalysed phrase Reanalysis is more difficult if the head of the misanalysed phrase is distant from the error signal! However, the length of the sentence is not important.

Christianson et al.’s experiments 3 experiments but the same paradigm: Participant were asked to read garden-path sentences or corresponding control sentences They answered YES/NO questions Indicated their confidence in that answer Primary dependent measures are question- answering accuracy and confidence.

Experiment 1: Stimuli (1a) While Bill hunted the deer (that was brown and graceful) ran into the woods. G-P (1b) While Bill hunted the deer (that was brown and graceful) paced in the zoo. G-P (1c) While Bill hunted the pheasant the deer (that was brown and graceful) ran into the woods. Non-G-P Difference between (a) and (b) => the plausibility of misinterpretation Note: each participant saw only one out of the 6 possible versions but experience each of the 6 conditions. Read the sentences at their own pace.

Experiment 1: continuation (1a) While Bill hunted the deer (that was brown and graceful) ran into the woods. (1b) While Bill hunted the deer (that was brown and graceful) paced in the zoo. (1c) While Bill hunted the pheasant the deer (that was brown and graceful) ran into the woods. Question: Did Bill hunt the deer? If people answer YES to (a) and (b) => they did not end up with the appropriate interpretation for the sentences. If they say YES if the material in the parenthesis is included => tendency to say YES is attributable to the initial syntactic misanalysis

Results of Experiment 1

Experiment 2 With 2 innovations: Instead of using the control condition, they created non-garden-path conditions by reversing the order of the subordinate and main clauses => The deer ran into the woods while the man hunted Asked people two questions: Did the man hunt the deer? + Did the deer run into the woods? Note: both phrases were long instead of short vs. long in Experiment 1

Experiment 2: Stimuli (2a) While Bill hunted the brown and graceful deer/ the deer that was brown and graceful ran into the woods. (2b) The brown and graceful deer/ the deer that was brown and graceful ran into the woods while Bill hunted. Questions: Did Bill hunt the deer? or Did the deer run into the woods?

Experiment 2: Results

Experiment 3 To avoid the inference: when someone is intransitively hunting, he or she may be hunting a deer => Reflexive Absolute Transitive (RAT) verbs, e.g. dress and bathe Two sub-experiments: 1. The non-GP condition was created by reversing the order of the subordinate clause. 2x2 design= a sentence was either G-Pathing or not and the verb was either normal or RAT 2. They varied whether or not a comma separated the subordinate and the main clause: While Anna dressed, the baby spit up on the bed. The same 2x2 design

Experiment 3: Results

Explanation of the results The general reasoning argument: High numbers of incorrect answers to the comprehension questions stem from pragmatic inference: the man is hunting, and the deer, which is a common quarry for hunters, is running away => the man is possibly hunting the deer.

Evidence against a general reasoning arguments 1. The strong head position effect in Experiment 2=> no obvious reason why “the deer that was brown and furry” should be more likely to be inferred to the quarry of the hunt than “the brown and furry deer”, yet the subjects were more likely to derive an incorrect interpretation from the former construction than from the latter. 2. Elimination of syntactic ambiguity without changing the information load: reversing the clause order and separating the clauses with a comma => significantly fewer incorrect YES responses than the GP sentences 3. Use of RAT verbs =>participants had trouble reaching the correct interpretation of RAT verbs in the GP conditions => Pragmatic inferencing cannot account for the misinterpretation effect in the GP conditions.

Final explanation of the results Some garden-path sentences were completely reanalyzed but for others, no reanalysis occurred. The significant proportion of incorrect YES responses in the GP conditions could have been attributed to guessing on the trials on which the reanalysis did not take place = > evidence against this possibility. Some degree of reanalysis must have taken place for the NP initially parsed as the object of the subordinate clause to be recruited as the subject of the matrix clause.

Nonsyntactic factors cannot account for the data. Thus… Two alternative explanations: Radical (that reanalysis terminates with and the parser settles on a structure that is not licensed by the principles of human syntax) The NP that is necessary for the main clause is stolen from the subordinate clause, yet not erased from the original position =>this explanation is consistent with a model of parsing and reanalysis by Fodor and Inoue (1998)

Fodor and Inoue (1998) “Attach Anyway” => directs the parser simply to attach an incoming element even if it does not fit into the current phrase marker, temporarily ignoring the ungrammaticality that results “Adjust” =>resolves the grammatical conflict minimally, so that the adjustment may result in yet another conflict elsewhere in the tree. Adjust then moves on to correct that conflict and so on. Note: Adjust is constrained by Grammatical Dependency Principle (GDP)=>Adjust operations apply between nodes that are in some sort of a grammatical relationship: a head and its argument or a verb and its subject

Fodor and Inoue (1998) Reanalysis of the sentences used in Ferreira et al.’s experiments does not involve elements in such a relationship => in such circumstances, Fodor and Inoue suggest that the parser engages in “theft”, i.e. the lexical string the deer is stolen from the subordinate clause and assigned a position in a matrix clause, in violation of GDP. Theft could result in the dual thematic role assignment of Theme and Agent to deer because when GDP is violated the backward repair operations (Adjust) that are normally set in motion by Attach Anyway do not take place. as a result, the parser would not end up being able to return to the subordinate verb, re-access the lexicon, and locate its intransitive argument structure. The subordinate verb would, therefore, remain transitive, yielding a structure that could support the dual Theme/Agent (mis)interpretation.

Fodor and Inoue (1998) For the plausible sentences (e.g. While the man hunted the deer ran into the woods, the overall interpretation is checked according to the Minimal Revisions Principle (MRP) MRP: any revisions deemed necessary and consistent with the error signal should maintain as much of the initially assigned structure and interpretation as possible. The MRP predicts that the proposition stating that the man hunted the deer would not necessarily be erased, because that interpretations should be maintained to the extent possible.

Fodor and Inoue (1998) RAT verbs=> reanalysis differs The correct analysis of the sentence While Anna dressed the baby spit up on the bed had the parser assigning the role of Theme to an empty category after dressed, resulting in a specific theme for the verb dressing (Anna herself). contrasts with While Bill hunted the deer ran into the woods: hunt’s Theme role cannot be assigned to any syntactic constituent at all. Therefore, the interpretation that must be created is generic: Bill hunted something or other. The participants’ level of confidence suggests that they are relatively insensitive to any violations that might result from the early termination of Adjust operations

General conclusion “It appears that people work on sentences until they reach a point where it subjectively makes sense to them and then processing may cease… these garden-path sentences somehow produce an illusion of comprehension in our participant...They will be misunderstood despite the best attempts of the comprehender to come up with a correct analysis”