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Effects of Semantic Association on the Resolution of Coordination Ambiguities


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1 EFFECTS OF SEMANTIC ASSOCIATION ON THE RESOLUTION OF COORDINATION AMBIGUITIES By CHRISTOPHER BARKLEY A THESIS PRESENTED TO THE GRADUATE SCHOOL OF THE UNIVERSITY OF FLORI DA IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF MASTER OF ARTS UNIVERSITY OF FLORIDA 2007

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2 2007 Christopher Barkley

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3 To all those who nurtured my academic curiosit y, interests, and pursuit of knowledge throughout my life

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4 ACKNOWLEDGEMENTS I would like to thank my committee, Dr. Edith Kaan and Dr. Wind Cowles, for their helpful advice while conducting this research. I would also like to thank my classmates and lab colleagues for their support a nd suggestions on this work.

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5 TABLE OF CONTENTS page LIST OF TABLES................................................................................................................. ..........7 FIGURE......................................................................................................................... ..................8 ABSTRACT....................................................................................................................... ..............9 CHAPTER 1 INTRODUCTION..................................................................................................................12 Sentence Processing Models and Ambiguity Resolution.......................................................12 Syntax-First versus C onstraint-Based Models................................................................12 Good-Enough Representations in Sentence Processing......................................................20 Processing Coordination........................................................................................................ .26 Processing Coordination Ambiguities.............................................................................29 Processing Coordinate Structures....................................................................................31 2 MATERIALS AND METHODS...........................................................................................34 The Present Experiment......................................................................................................... .34 Predictions.................................................................................................................... ..........36 Questionnaire study............................................................................................................ ....37 Participants................................................................................................................... ...37 Materials...................................................................................................................... ....38 Procedure...................................................................................................................... ...39 Analysis....................................................................................................................... ....39 Results........................................................................................................................ .....39 Self-Paced Reading Study......................................................................................................39 Participants................................................................................................................... ...39 Materials...................................................................................................................... ....40 Procedure...................................................................................................................... ...41 Analysis....................................................................................................................... ....42 3 RESULTS........................................................................................................................ .......43 Comprehension Data............................................................................................................. .43 Accuracy....................................................................................................................... ...43 Reaction Time.................................................................................................................43 Reading Time Data.............................................................................................................. ...44 4 DISCUSSION..................................................................................................................... ....47 Comprehension Data............................................................................................................. .47 Reading Time Data.............................................................................................................. ...50

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6 Interaction of Parallelism and Ambiguity at the Post Disambiguating Verb Preposition (Position 11).........................................................................................50 Main Effect of Parallelism at th e Post-Conjunction Noun (Position 9)..........................52 The Relationship between Comprehe nsion and Reading Time Data.....................................56 Syntax-First versus C onstraint-Based Models........................................................................56 Good-Enough Representations in Sentence Processing....................................................58 5 CONCLUSION..................................................................................................................... ..59 6 FUTURE WORK....................................................................................................................60 APPENDIX A EXPERIMENTAL MATERIALS..........................................................................................61 B FILLER SENTENCES...........................................................................................................65 LIST OF REFERENCES............................................................................................................. ..66 BIOGRAPHICAL SKETCH.........................................................................................................69

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7 LIST OF TABLES Table page 1-1: mean RT and accuracy per condition.....................................................................................45 1-2: mean (SD) reading times by condition...................................................................................45

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8 FIGURE Figure page 2-1: mean reading times at each position (by subjects).................................................................46

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9 Abstract of Thesis Presen ted to the Graduate School of the University of Florida in Partial Fulfillment of the Requirements for the Degree of Master of Arts EFFECTS OF SEMANTIC ASSOCIATION ON THE RESOLUTION OF COORDINATION AMBIGUITIES By Christopher Barkley May 2007 Chair: Edith Kaan Major: Linguistics In constructions such as (1) the man is temporarily ambiguous: it can either serve as the second NP of a coordinate object of the first verb (NP-coordination) or th e subject of the second verb (S-coordination). Previous research ha s demonstrated that readers prefer an NP coordination reading, and garden path at the second verb in the sentence. One account is that the ambiguous NP is initially attached to the preceding NP to form a coordinate noun phrase forcing readers to re-analyze when they reach the disa mbiguating verb, based on syntactic principles. A recent study, examined effects of non-syntactic information on the resolution of coordination ambiguities and demonstrated that poor thematic f it between the initial verb in the sentence and the ambiguous noun phrase can reduce processing difficulty at the disamb iguating region but not completely eliminate it. In the present study, we investigated whether th e effect of semantic association between the relevant NPs can ease or eliminate difficulty at the disambiguating region in these constructions. In addition, we i nvestigated whether after disambiguation, readers successfully re-analyze cons tructions such as (1). (1) The girl screamed at the woman and the man screamed at the boy.

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10 Thirty-six participants read seven trials each of the four conditions in (2) in a self-paced reading study, intermixed with filler items. The experimental sentences were either ambiguous (a, c) or unambiguous (b, d), based on the conj unction, and the two subj ect NPs were either associated (c, d) or un-associated (a, b) as determined by an inde pendent paper-and-pencil rating. Care was taken to avoid plausibility confounds by using only neutral, transitive verbs and animate, human NPs in the experimental sentences If readers indeed take information regarding semantic association into account while parsing ambiguous sentences, then processing difficulty should be reduced or eliminated at the disamb iguating verb in the associated NP, ambiguous condition. We found a main effect of association at the noun fo llowing and, with the nouns unassociated with the first subject NP (2a, b) taking longer to read than associated nouns (2c, d). The direction of the main effect at the post-co njunction NP shows that this effect cannot be attributed to different degrees of lexical priming between local NPs. We also found an interaction between association a nd ambiguity at the post-verbal preposition. Reading times were longest for the unassociated, ambiguous condition (2a) compared to the remaining conditions, which did not differ. This suggests that the effect of semantic association can almost completely override processing difficulty in the disambiguating region. Accu racy data illustrate that participants may not always re-analyze thes e constructions completely, as accuracy was significantly lower to the ambiguous sentences than the non-ambiguous it ems. Accuracy was also significantly higher to associated than nonassociated conditions, suggesting that semantic information may ease re-analysis. These results suggest that readers are taking semantic factors into account online, and using this informati on to guide parsing deci sions, but do not always successfully reanalyze or overwri te the initial interpretation.

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11 (2) a. Non-associated subject NPs, ambiguous The enemy talked to the queen a nd the king talked to the people. b Non-associated subject NPs, non-ambiguous The enemy talked to the queen but the king talked to the people. c. Associated subject NPs, ambiguous The king talked to the enemy and the queen talked to the people. d. Associated subject NPs, non-ambiguous The king talked to the enemy but the queen talked to the people.

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12 CHAPTER 1 INTRODUCTION Sentence Processing Models and Ambiguity Resolution Syntax-First versus Constraint-Based Models Language comprehension takes place both rapi dly and incrementally. Because a large part of the comprehension of a sentence is base d on its syntactic structure, comprehenders are forced to make decisions of a structural nature in real time, although th ey are frequently faced with syntactic indeterminacy and temporary am biguity. Traditionally, there have been two approaches to describing how the parser accomp lishes the feat of interpretation under these less than ideal circumstances, and these approaches have been contrasted extensively in the literature. The first approach grants primacy to structurally based factors. Accordin g to these syntax-first models, listeners/readers employ kno wledge of the grammar of thei r language in order to build a single structure into which incoming words are placed ; without recourse to context, plausibility, or any other non-structural source of information. Thus, during comprehension the listener/reader adopts a single in terpretation of the unfolding sent ence based only on grammatical category information and syntactic principles an d only employs other sources of information in order to evaluate the appropriate ness of the structure and revise it if necessary. This view of sentence parsing has been very influential and th ere are many versions of this approach (Ferreira & Clifton, 1986; Frazier 1979), with perhaps the most influe ntial being Lynn Fr aziers garden path model (Frazier, 1979). In this model, the parser build s a first parse based on only the grammatical categories of the incoming lexica l items. When a sequence of grammatical categories is consistent with more than one structure, the processo r employs parsing principles to distinguish between them. The pr incipal of minimal attachment states that incoming materials are attached into the phrase marker with the fe west syntactic nodes c onsistent with the well-

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13 formedness rules of the language. If two analyses are equally simple, late closure dictates that incoming information is attached to the constituen t currently being processe d; this ensures that only one structure will be pursued. Based purely on grammatical category information and these structural principles, the pa rser constructs its initial analysis of the sentence. In opposition to these syntax -first models, constraint-b ased models (MacDonald Perlmutter, & Seidenberg, 1994); assert that th e process of building the interpretation of a sentence involves the interaction of numerous f actors in addition to synt actic considerations. Plausibility, frequencies of occu rrence and co-occurence, the rela tive weighting of grammatical and probabilistic constraints, and animacy are ju st some of the sources of information that contribute to the construc tion of an interpretation. As a se ntence unfolds, all possible analyses are computed in parallel by the parser and evaluated using multiple sources of evidence in the input. Alternative structures are partially act ive with the activation level dependent on the degree to which the input supports a given struct ure. The interpretation that receives the most support from the input then wins out over its competitors, and the input is assigned this structure. Processing difficulty arises when a lternatives are closely matched in terms of the support they receive from the input Grammatical information may indeed be important to this process and therefore may be a heavily-weighted s ource of evidence, but it s temporal primacy is removed and it takes no serial precedence over non-st ructural factors. The role of syntactic factors is not the only crucial difference betw een the models, however. Syntax-first models compute structures in serial order, and thus are often called serial, depth-first parsers; the first parse is computed based on structural factors, an d then revisions are computed serially based on other relevant sources of information in the input In contrast, constraint-based models assume that all structures are computed in parallel, generating a type of competition which the best

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14 structure wins. The contrast between these two models has motivated a great deal of research, generating results that appear to strongly support these contrasting views. The present research aims to add to the debate between these models by examining the effects that semantic association has on the resolution of coordination ambiguities. Ferreira & Clifton (1986) employed eye-track ing and a behavioral self-paced movingwindow technique to show that readers expe rienced difficulty when what was initially understood as a subject plus main verb was disambiguated towards the dispreferred (nonminimal attachment), less frequent reduced rela tive clause structure (1a, 2a below) This structure, depending on verbs th at are morphologically ambiguous between past participle and past tense forms, is known as the reduced relativ e ambiguity and has been studied extensively. Ferreira and Clifton demonstrated that this processing disrupti on, the garden path effect, was experienced even when the subject plus main ve rb analysis was highly unlikely because of an inanimate subject in sentence-init ial position, as in 2a). Thus, Fe rreira and Clifton saw increased reading times at the disambiguating region in both 1a and 2a (when compared to unambiguous counterparts in b): 1a) The defendant examined by the lawyer turned out to be unreliable. 1b) The defendant that was examined by the lawyer turned out to be unreliable. 2a) The evidence examined by the lawyer turned out to be unreliable. 2b) The evidence that was examined by the lawyer turned out to be unreliable. As readers begin to construct their parse of sentences like 1) and 2) above, it is assumed that they initially adopt a main-clause analysis and assign the role of subject and agent to the defendant in 1) and the evidence in 2) (Based on the principl e of minimal attachment under a syntax-first model (Frazier, 1979); or based on the higher frequency of this structure under a

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15 constraint-based approach (MacDonald et al 1994). However, when readers reach the by -phrase followed by the main verb, the parse under construc tion becomes inconsistent with the input and the structure must be revised. This is the cause of the increase in reading time when compared to the sentences in b) which are unambiguous between main verb and reduced-relative interpretations because of the appearance of that which unambiguously signals a relative clause. Crucially, if readers take animacy or plausibility into account to guide parsing decisions, then the difficulty should be overridden or at least reduced in 2a) when co mpared to 1a). The fact that Ferreira and Clifton observed simila r patterns of disruption in 1a) and 2a) led them to argue for an informationally-encapsulated syntax module. They argue that this module operates on purely syntactic principles and is insensitive to othe r sources of information, such as animacy. Thus, their results support a synt ax-first parser and are inconsistent with a constraint-based process in which multiple structures are computed in parallel based on the contributions of all possible sources of information. Trueswell, Tanenhaus, and Garnsey (1994) influe ntially challenged the results of Ferreira and Clifton (1986) by asserting that the implausibl e (inanimate) subjects were selected for their materials without extensive pre-te sting. Trueswell et al. argued that many of the implausible subjects were actually compatible with the main verb interpretation (such as the car towed.) thus making the results of Ferre ira and Clifton hard to inte rpret and rendering the data inconclusive. Using paper-and-pencil completion norms, Trueswell et al. had participants rate how typical animate and inanimate nouns were as agents and themes. Based on the results of this study, Trueswell et al. constructed the sa me paradigm employed by Ferreira and Clifton (1986), except with more highly controlled nouns in sentence-initial subj ect position, and then employed the same experimental techniques in order to determine if Ferreira and Cliftons

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16 results were replicable. This ensured that all animate subjects we re good agents, and all inanimate subjects were poor agen ts and good themes. Trueswell et al. (1994) reported that, with their modified materials, the diffi culty observed at the disambiguating byphrase of reduced relative constructions with inanim ate subjects disappeared. The au thors state that their results are most consistent with a evidential constrai nt-based model of sentence parsing in which grammatical information takes no precedence over nonstructural factors, a nd multiple sources of information interact during stru cture-building operations. Clifton, Traxler, Mohamed, W illiams, Morris, & Rayner (2003) extended the research of Ferreira & Clifton (1986) by employing an eyetracking methodology to examine the resolution of reduced-relative ambiguities. They again cros sed ambiguity with the animacy of the subject to form sentence quadruplets like 3) below: 3a) The man paid by the parents was unreasonable. 3b) The man who was paid by the parents was unreasonable. 3c) The ransom paid by the parents was unreasonable. 3d) The ransom that was paid by the parents was unreasonable. Clifton et al. also manipulated para foveal preview of the disambiguating byphrase so that each condition above was seen by so me participants with the disambiguating byphrase visible in their para fovea and by others with the disambiguating byphrase masked. This manipulation was introduced in response to so me criticisms of Ferre ira and Clifton (1986); namely that the grammatical information expressed by the byphrase may have been used to guide parsing decisions. By introducing this ma nipulation into their experimental design as a factor, they were able to determine any possible effect of the participant seeing the byphrase while processing the ambiguous verb. Clifton et al. found evidence of di sruption (in terms of

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17 first-pass time, regression frequency and regressi on duration) at the disa mbiguating region (again the byphrase) in the reduced relative constructions regardless of animacy or preview. Late measures of processing seemed to indicate that animacy made the ambiguity especially hard to overcome, with the reduced relative structures with animate subjects proving hardest to revise. These data support the notion that animacy cannot guide parsing d ecisions, but that it can serve to ease re-analysis after misinterpretation. While these results initially seem to argue for a syntax-first parser, Clifton et al eloquently argue that this is a hasty conclusion. Clifton et al. state that while the data do cast doubt on the no tion that semantic and pragmatic factors can override syntactic considerations, that this can not be straightfo rwardly concluded. They contend that syntactic preferences may be overridden in some domains and not others, and that a constraint-based theory could al so explain their data by simply ranking constraints such that structural simplicity outweighs se mantic plausibility. These ar guments actually extend to most research designed to probe this theoretical dis tinction; with proponents of each model attributing effects to different stages of the parsing proce ss. For example, if it appears that animacy can guide parsing decisions (e.g Trueswell, Tane nhaus, and Garnsey, 1994); then syntax-first proponents can simply attribute these effects to rapid re-analysis guided by semantic principles. For this reason, it is notoriously difficult to interp ret data gathered by experiments designed to test syntax-first vers us constraint-based models. The issues raised by Clifton et al. should be considered when critically evalua ting any research in this domain. One issue that arises when cr itically evaluating these studie s is the use of animacy as a semantic factor. Trueswell (1994), Clifton et al. (2003), and Ferreir a & Clifton (1986) all employed animacy to argue either for or against semantic effects on parsing decisions. Animacy is not the ideal factor for this purpose, as it is somewhat cont roversial as to whether it is a

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18 completely non-structural factor. When consider ing what sort of inform ation could influence a restricted domain, or syntax-first parser, there was considerable debate about whether to include thematic information such as animacy. Animacy is morphologically marked in some languages with clear morpho-syntactic conseq uences, and in some languages, such as Japanese, structural decisions on subject-hood are based on animacy inform ation. It is also inco rporated into a verbs argument structure under some accounts, grantin g animacy structural consequences. The semantic manipulation in the present experiment was desi gned to avoid this issue. Trueswell (1996) examined the effect of frequency on the resolution of ambiguous reduced relative clauses. The sp ecific type of frequency that he was interested in was the frequency with which a verb that is morphol ogically ambiguous between past tense and past participle appears in each of these forms. Cr ucially, constraint-based models predict that difficulty in assigning a reduced re lative clause interpretation to a structure should be modulated by the frequency with which a morphologically ambiguous verb form is employed in this construction. Trueswell conducted two self-pace d reading experiments in which readers read relative clause ambiguities which were mani pulated along three dimensions: whether the sentence contained a reduced or unreduced relative clause, whet her the subject was animate or inanimate, and whether the main verb had a high or low frequency as a past participle. Results of these experiments supported the notion that readers are subject to frequency effects when building the first-parse of a sentence. Trueswell found that when the relative clause interpretation received support from semantics (in the form of an inanimate subject), this information served to override processing difficulty for verbs with high participle frequencies but not those with low participle frequencies. When semantics provided support for the main clause interpretation (in the form of an animate subject ), there was evidence of processing difficulty for

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19 both verbs, though ambiguity resolution appeared to be faster in the high participle frequency group. Trueswell states that these results support a constraint-based model of sentence parsing, in which verb-form frequency interacts with ot her structural and non-st ructural sources of information during parsing. Trueswell argues that based on this data, processing models should take statistical frequency into account in ad dition to other non-struc tural factors. Garnsey, Pearlmutter, Myers, & Lotocky (1997) examined the effects of verb bias and plausibility on the resolution of sentences cont aining temporary ambiguities. Garnsey et al. manipulated the plausibility that th e post verbal NP would be interpreted as a direct object of the verb, the bias towards the transitive reading indu ced by the verb, and the presence or absence of ambiguity. These manipulations resulte d in the paradigm seen in 5): Direct-object (DO) biasing verbs: 5a) The talented photographer accepted (t hat) the money could not be spent. 5b) The talented photographer ac cepted (that) the fire coul d not have been prevented. Subordinate clause biasing verbs 5c) The ticket agent admitted (that) th e mistake had been careless and stupid. 5d) The ticket agent admitted (that) the airplane had been late in taking off. Non-biasing verbs 5e) The sales clerk acknowledged (that) the error should have been detected earlier. 5f) The sales clerk acknowledged (that) the shirt should have been marked down. Garnsey et al. found that ve rb bias has a rapid effect on ambiguity resolution, with readers experiencing the most difficulty at th e disambiguating region in sentences with DO biasing verbs. Garnsey et al. also found an effect of plausibi lity, with implausible objects reducing difficulty at the point of disambiguation, and this effect in teracted with verb bias during

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20 comprehension. The authors interpreted their results as best fitting into a constraint-based model of sentence parsing, which takes into account non -structural factors (plausibility) and factors generated by comprehenders experience with tran sitivity/subordinate clause frequencies of specific verbs. Good-Enough Representations in Sentence Processing To this point, I have focused my descripti on of sentence processing models on the factors that may or may not interact to guide parsi ng decisions during comprehension. Verb bias, plausibility, animacy, and frequency are among th e sources of information that may possibly influence structure building operati ons; and there is evidence pointi ng either to effects generated by these factors or a lack thereof. A great deal mo re research is required to resolve this debate. There is another debate, orthogonal to the debate between syntax-first and constraint-based models, and it concerns the repres entational nature of the output of the parsing processes. An implicit assumption of both syntax-first and constr aint based models is that the end result of parsing (with or without re-analysis) is a syntactic frame that is fu lly compatible with the input. Regardless of whether the relativ e activation of this frame can be influenced by non-syntactic information as the parser moves through the sentence, the interpretation of a sentence must be based on a syntactic frame. The parser is tr aditionally viewed as a compositional algorithmic processor that continues processing until the correct structure is built. The meaning of a sentence is derived from the composition of the meaning of its parts; and the parser analyzes to the extent that it can reach this interpreta tion. Recent research has begun to challenge this assumption by illustrating that the end result of comprehension is often an incomplete or inaccurate representation. One source of data that supports this view is the Moses illusion (Erickson & Mattson, 1981). When asked, How many animals of each type did Moses bring on the ark? people often respond two, without noticing the glaring error. While this evidence is frequently

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21 employed to demonstrate the fallibility of memo ry, the degree to which listeners do not fully process the input is striking. Barton and Sanford (1993) documen ted a similar effect, noticing that people rarely notice the problem with the question, Where did the author ities bury the survivors? While these sources of informati on are somewhat anecdotal, they do lend support to the view that language processing is sometime s shallow and that compositionality does not always hold. I will now summarize some research that lends support to this shallow, heuristic processing. Ferreira (1996) used simple, unambiguous se ntences to investigat e the issues raised above. Ferreira examined this issue with the paradigm in 6), which manipulates bias, plausibility, and grammatical voi ce. The sentence was either presented in active or passive voice, and the arguments could be presented in on e of two orders. In th e reversible conditions, reversing the order of the argumen ts led to a possible but impl ausible arrangement (as can be seen in 6b). In the non-revers ible condition, reversi ng the order of the arguments led to a semantically anomalous arrangement, and in the symmetrical condi tion rearranging the arguments had no effect on plausibility. The full paradigm can be seen in 6): Active Passive 6a) biased, reversible, plausible The dog bit the man. The dog was bitten by the man. 6b) biased, reversible, implausible The man bit the dog The man was bitten by the dog. 6c) nonreversible, plausible The mouse ate the cheese. The cheese was eaten by the mouse 6d) nonreversible, implausible

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22 The cheese ate the mouse. The mouse was eaten by the cheese. 6e) symmetrical, one order The woman visited the man. The man was visited by the woman. 6f) symmetrical, other order The man visited the woman. The woman was visited by the man. Sentences were presented to the participan ts aurally, and the participants were then probed with comprehension questions that forced them to identify the thematic roles in the sentence (i.e., DO-ER? ). The results show that there is a cost for the passive, so that for all sentence types, the participants made more erro rs on the questions probing the passive voice than they did on the questions probing the active voice, and also res ponded to these sentences more slowly. It appears that, even in relatively simple, unambiguous sentences, comprehenders frequently misassign thematic roles leading to inaccurate representations. The authors conducted a second experiment to ensure that it was not surface frequency of the construction generating this effect, passive being less frequent than active, by comparing simple active sentences and subject-cleft constructions. This was indeed no t the case as subjects pe rformed equally well to questions probing actives and subject clefts, even though the subjectcleft construction is extremely infrequent in English. A third experi ment demonstrated a parallel between object and subject clefts and actives and passives, with participants performing poorly on questions probing the object clefts. The parallel be tween the object-cleft construction a nd the passive is instructive. Both of these constructions force comprehenders to assign thematic roles in an atypical order. The fact that this atypical order of assignment is so problematic for read ers points to a processor that employs heuristic strategies (one such strategy, the NVN strategy, listeners readers to identify the pre-verbal noun as a proto-agent and the post-verb al noun as the proto-patient)

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23 caused rather than detailed algorithms; strategies which are prone to breakdown in atypical or infrequent situations. Ferreira in terprets these results as evidence of a heuristic processor, she states that comprehenders often rely on shallo w processing that is simply good enough, rather than always relying on complex s yntactic algorithms. In some cases, as in the experiment, noncanonical or atypical structures cau se the parser to assign thema tic roles to the wrong syntactic constituents. The result is an underspecifie d, incomplete representation that may never be completely revised. Crucially, Ferreira argues that these results are inconsistent with any processing model (Frazier, 1979; MacDonald et al. 1994) that a ssumes that the parser only computes structures that are c onsistent with the s yntactic information encoded in the input. Whether non-structural information can influenc e the computation of th e structure or not, both types of model argue that the structure must be built based on a syntactic frame. Ferreira argues against this position convincingly. Christianson, Hollingworth, Halliwell, a nd Ferriera (2001) examined incomplete or inaccurate representations by examining whether read ers ever fully delete their initia l incorrect interpretation of a sentence after re-analysis. In order to examine this issue they employed transitivity ambiguities (with no commas to enhance the effect) as seen in (7). The reader will initially interpret the baby as the object of dressed. However, when they encounter the verb spit they will encounter difficulty as the parse under construction is inc onsistent with the input. They will then have to revise their interpretation; and the authors were interested in the fate of the initial analysis. 7) While Anna dressed the baby spit up. Previous research has assumed that, afte r mis-analysis, readers fully repair the representation to the extent that the parse becomes fully consiste nt with the input string. After

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24 reading sentences such as 7), subjects were probed with questions such as Did Anna dress the baby? and, Did the baby spit up? Questions such as these can onl y be answered correctly if, after mis-analysis, the parser detaches the baby from the slot designating it as the object of the verb and re-attaches it to subject position of th e second verb. Christianson et al. found that subjects were almost 100% accurate in stating that the baby spit up. However, a surprising number of errors were found in which subjects took the baby to be the object of dressed. This is evidence that their final representa tion is not consistent with the input. This could be caused by a failure to re-analyze and assign thematic roles to the correct constituents, or by interference between the unsurpressed initial incorrect interpreta tion and the correct one. It also may provide evidence that a comprehenders final representation isnt always consistent with linguistic wellformedness conditions, as some participants interpreted the baby as both the subject of spit up and the object of dressed an interpretation that violates stru ctural principles such as the thetacriterion. Though as stated above, it could also be the case that the accuracy pattern described may be caused by the incorrect analysis persisting in memory to the extent that it can compete with the subsequent analysis and influence co mprehension. In the second experiment, the researchers compared garden-path sentences such as 7) with unambiguous controls. The results suggest that readers often do not completely re-analyze a constr uction, or that if they do, the incorrect analysis persists to the extent that it can influence comprehension. These results nicely tie language comprehension to other areas of cognitive science, such as vision, where recent findings have shown that the visual system does not construct a true global image of a visual scene leading to change blindness, which refers to the observation that many participants are insensitive to changes in a visual scene as they ar e viewing it. These data suggest that the visual system may also rely on re presentations that are not always fully detailed. It may be the case that

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25 the heuristic strategies discussed by Ferreir a (1996) and Christia nson et al. (2001) are advantageous to an organism who must interact with its environment rapi dly, in which case these types of strategies would be employed in all domains of cognition and decision making. Further evidence for the persistence of the initial misanalysis and its effects on comprehension comes from a study by Van Gompel, Pickering, Pearson, & Jacob (2006). They had participants read sentences including verbs that were ambiguous between transitive and intransitive structures; in one condition the transitivity of the verb was disambiguated with a comma but it in the other condition no disambiguating information was presen t leading subjects to initially interpret an intransitive verb as transitive. This led partic ipants to garden path and temporarily activate a transitive reading of the verb in the condition with no comma. After having read the sentence, participants were prompted to complete a senten ce fragment out loud. Participants were more likely to produce transitive comp letions after the ambiguous conditi on in which they had initially misinterpreted the verb as transi tive, indicating that the initial mi sinterpretation persisted to the extent that it could influence production. The authors were unable to distinguish between the different accounts that provide an explanation for th is effect (persistence of a memory trace, lack of re-analysis, or appl ication of a heuristic). In sum, Ferreira (1996), Christianson et al. (2001), and Van Go mpel et al. (2006) demonstrate that the parser often constructs incomplete representations that are not the result of exhaustive analysis. Whether it is the result of applying a heuristic to the processing of simple sentences, failing to completely re-analyze the inpu t, or not suppressing the initial interpretation; evidently the parser is often satisfied with constructing repr esentations that are only good enough.

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26 The research that I have presented lays out the issues surroundi ng the debate between syntax-first and constraint ba sed processing models, and betw een algorithmic and heuristic processors. As we have seen, these debates cen ter on what types of information (syntactic and non-syntactic) can influen ce initial parsing decisions and whether the end result of this parse is a linguistic representation that is fully specified at all levels. Processing Coordination The purpose of the current study is to colle ct data that help to resolve these issues utilizing coordination ambiguities and a manipulation that varies which previous noun phrase in a sentence an ambiguous noun phrase is semantically associated with. A coordination ambiguity is a sentence like (8) below; in which the NP the man is ambiguous between being the second NP in a coordinate object of the main verb of the firs t clause and the subject of the main verb of the second clause. The sentence is disambiguated at the verb talked, when it becomes clear that the man is in fact the subject of a second clause. 8) The woman talked to the boy and the man talked to the girl. Previous research on this construction has demonstrated the so called NP coordination preference (Frazier, 19 79; Kaan & Swaab, 2003; Hoeks, 2006). Th is causes reader s to initially interpret the ambiguous NP as part of a coordinate object of the first verb and therefore initially adopt the wrong analysis of the sentence. This triggers processing difficu lty and re-analysis at the second verb, when the parser realizes that the input has been misanalyzed. For instance, Kaan and Swaab (2003) provided evidence for the NP coordination preference using an ERP technique. Part of their expe rimental manipulation compared coordinated sentences with ungrammatical con tinuations versus continuations that were dispreferred. Importantly, the dispreferred condition is only di spreferred if participants initially adopt an analysis where the house and the garage form a coordinated NP. For example:

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27 Ungrammatical 9) The man was painting the house and th e garage were already finished. Dispreferred 10) The man was painting the house and th e garage is already finished. Kaan and Swaab (2003) found that both di spreferred and ungrammatical continuations elicited a LAN effect at the ve rb after the ambiguous NP, this ERP component indexes early syntactic processing difficulty that may reflect local phrase struct ure violations induced by what the parser perceives as word category errors (Friederici, Pfeiffer, and Hahne 1993; Neville, Nicol, and Barss 1991, Hahne and Friederici 1999). Crucially, for the purposes of this paper, these data suggest that the parser initially a ttached the ambiguous NP to the preceding NP to form a complex object. When it reaches the disambiguating verb, th e parser experiences difficulty and initially interprets the string as ungrammatical because the verb cannot be incorporated into the phr ase structure currently under construc tion. While these data do reveal that the parser is prone to attaching the ambiguo us NP to form an NP coordination, they have nothing to say about what underlies this effect I will quickly summarize two approaches to explain this parsing preference: syntactic principles and frequency based accounts. Following the syntactic principle of minima l attachment, Frazier (1979) predicts that readers will initially attach the ambiguous noun phr ase to a second object sl ot of the first verb, creating a coordinate noun phrase reading. This occurs because to creat e a full S-coordination requires the creation of one ex tra S node to head the new cl ause, thus violating minimal attachment (create the fewest nodes possibl e) and causing the parser to choose the NPcoordination analysis. After the reader adopts this structure, they will garden path at the second

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28 verb and have to re-analyze th eir initial mis-interpretation, presumably with measurable processing cost resulting. This is a syntax-b ased account of the NP c oordination preference. Hoeks (2006) adopted a freque ncy based approach in attempt to explain this preference. He conducted a corpus study examining the prevalen ce of Sand NP-coordinations in the Dutch newspaper TROUW. In a set of 1000 occurr ences, NP coordination was by far the most prevalent, making up 46% of the in stances using the Dutch connective en (equivalent to and ). Scoordination only made up 10% of these instances. So, perhaps it is not necessarily a syntactic principle that underlies the NP c oordination preference, but rather just frequency of occurrence which causes readers to adopt the most likely structure based on frequency. While the underlying mechanism of the NP coordination preference may be unclear, it is a robust finding in sentence processing experi ments. Whether motivated by frequency or syntactic principles, this preference causes re aders to incorrectly assign an NP coordination reading to S-coordination struct ures and garden path at the di sambiguating verb. The purpose of the current research is to a ttempt to modulate this attachme nt preference in coordination ambiguities with semantic factors. By varying whether the ambiguous noun phrase is semantically associated with the subject or the ob ject of the first verb, the present study aims to determine whether this preference can be overridden and processing di fficulty reduced. If this is the case, processing disruption w ould be reduced at the disambiguating verb in sentences like (8). Before summarizing the present study, it is first necessary to discuss the previous research that has been examined factors that can influence the reso lution of coordination ambiguities as well as the factors that influen ce the processing of the second conjunct of a coordinate phrase.

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29 Processing Coordination Ambiguities Hoeks (1997, 1999, 2002) has conducted a series of experiments examining factors that have an effect on the online resolution of c oordination ambiguities. Before examining these factors, Hoeks (1997) employed eye-tracking and ERP methodologies to examine the NPconjunction preference predicted by minimal attach ment (Frazier, 1979). The data from these parallel experiments suggest that readers do indeed demonstrate this processing preference, as ERP and eye-tracking indices of parsing disruption were eviden t at and immediately following the disambiguating region of the coordination ambiguity. Next, Hoeks examined whether a semantic manipulation could eliminate processi ng difficulty by overridi ng the NP-conjunction preference. He chose to investigate this issue by manipulating the thematic fit between the verb and the ambiguous noun phrase, leading to th e experimental manipulation seen in 9): 9a) The boatman repaired the ma insail and the skipper painted the mast of the boat. 9b) The sheriff saw the Indian and the cowboy noticed the horse in the bushes. If the parser computes thematic fit online and uses this information to guide parsing decisions, then the processing difficulty encounte red at the underlined region of 9b) should be reduced at the underlined region of 9a). In 9a), the NP the skipper is not a good argument of the verb repair because it is animate, and Hoeks (1997) wa s interested in whether this type of information was taken into account when parsing these constructions. He found that all effects of processing difficulty in the disambiguating regi on disappeared as a result of this manipulation, and used these data to argue ag ainst syntax-first models. Wh ile he acknowledges the argument that re-analysis may have proceeded very quick ly in these cases, indi cating that the ambiguous construction was still mis-analyzed; he argued that if this were the case, then the ERPs would have shown signs of residual processing difficu lty, which they did not (however see Hoeks (2006), in which he argues that signs of residual difficulty are in fact present). One issue that is

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30 evident in regards to these experi mental materials is that perhaps the conjunction of animate and inanimate NPs is so unnatural that the readers did not consider the NP -conjunction analysis. This argument is backed up by an examination of language corpora which demonstrate that that coordination of this type very rarely occurs in natural language (Hoeks, 2006). Hoeks (2002) examined the effect that di scourse structure in the preceding context has on the resolution of coordination ambiguities. He argued that the NP conjunction preference demonstrated by himself and other re searchers is motivated by the fact that this interpretation is simpler in terms of discourse structure. Hoeks first conducted a completion study which illustrated the NP-coordination preference. He found that when completing fragments such as The photographer spoke with th e model and the actress., only 15% of completions represented S-coordination. However, when the prior contex t introduced two subjects (see 10a), the number of S-coordination completions rose to 80%. He then examined these issues with eye-tracking and self-paced reading techniques. He ha d participants read ambiguous S-coordination sentences, that were either preceded by neutral contexts or contexts th at introduced two NPs in coordinate subject position into the discourse. The paradigm is seen in 10) 10a), biasing context: When they met the designer at the party afterward, the model a nd the photographer were very excited. 10a), neutral context: It was not surprising that the party af ter the fashion show was exhilarating. 10b), target sentence: The model embraced the designer and the photographer laughed.

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31 Hoeks found that readers en countered difficulty at the disambiguating region of the coordination ambiguities when they were preced ed by neutral contexts. When the ambiguous target sentence was preceded by a sentence intr oducing two subjects, all traces of processing difficulty disappeared. He used this data to argue for the immediate effect of context on the resolution of coordination ambiguities and agains t models of sentence processing that give precedence to structural sources of information. Hoeks (1997, 1999, 2002) documented that thema tic fit and discourse structure have effects on the resolution of coordination ambiguities, and it is essentially his work that will be extended in this paper. Let us first examine this issue from a slightly different perspective. Lyn Frazier and colleagues have conducted a series of experiments examining what factors can influence the processing of the second conjunct in a coordinate phrase, and I will now summarize this work. Processing Coordinate Structures In earlier work, Frazier et al. (1984) conducted a series of self-paced reading experiments examining the coordination of sentences. Frazier et al. were interested in whether they could find an effect of structural paralle lism (two constituents are said to be structurally parallel when they share the same internal structure) when pr ocessing coordinated phrases. They investigated this in many syntactic environments, such as active/passive, minimal/ non-minimal attachment, shifted/non-shifted heavy NPs, agent/theme, and animate vs. inanimate NPs. Across all environments, Frazier et al. found an effect of parallelism. Ther efore an active construction was read more quickly when it was preceded by an active than when it was preceded by a passive, a non-minimally attached structure was read mo re quickly when it was preceded by another nonminimally attached structure than when it was pre ceded by a minimally attached structure, etc. Frazier et al. used these data to argue that coordination constitu tes a special syntactic case, but

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32 does not and cannot conclude what the cause of the parallelism ef fect is. Nonetheless, this research demonstrates that parallelism is a fact or that can affect the processing of coordinate structures. Frazier, Munn, and Clifton (2000) conducted as se ries of four experiments examining the processing of coordinate struct ures. They utilized an eyetracking methodology to investigate factors that influenced the proces sing of these structures. They found that coordination of unlike categories was just as acceptable as processing tw o conjuncts of the same category. They used this data to argue against a grammatical constrai nt that only constituents of the same category can be conjoined. They did, how ever, find processing facilitation (in terms of reading time) at the second of two conjuncts when it was either parallel in terms of category or internal structure. For example the underlined portion of (9) was read faster than the underlin ed portion of (10), due the fact that it is preceded by a conjun ct with the same internal structure. 9) Bill talked to the tall man and the short woman. 10) Bill talked to the man and the short woman. Additionally, Frazier et al. (2000) found a similar effect of s yntactic category, leading to a reduction in reading time for a constituent th at was preceded by a constituent of the same category. This effect would lead to the underlin ed portion of 11) being read faster than the underlined portion of 12): 11) John walked with great speed and with great care. 12) John walked slowly and with great care However, the same facilitation was not found between two noun phrases that served as the subject and object of a verb. The authors use these data to argue that coordination enjoys some sort of special status, as effects were not seen when using the same NPs in different

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33 constructions. The authors successfully demonstrat e that internal structure of the conjuncts is one factor that influences the processing of coordinate structur es, and hint at the fact that coordinate structures may be influenced by factors that do not necessarily influence other structures. This echoes Clifton s (2003) argument that factors ma y have an influence on parsing decisions in some doma ins, but not others. While Fraziers primary interest is in the processing facilitation induced by structural parallelism in coordination structures, and the current experimental paradigm will manipulate whether an ambiguous noun phrase is semantically associated with the subject or object of the main verb, her work still provides crucial b ackground to the presen t study. The present study aims to elucidate the factors that can influe nce the interpretation of the ambiguous NP in coordination ambiguities. Research into these factors can be conceptualized in two ways. First, it is a continuation of Hoeks work that has already documente d the effect that discourse structure and thematic information can have on the attachment of this noun phrase. Secondly, the present experiment has much in common with the work of Frazier and colleagues. Crucially, the ambiguous noun phrase is a second conjunct a nd its interpretation can be influenced by characteristics of the first c onjunct as documented by Frazier. If semantic parallelism has a similar effect to structural parallelism between conjuncts, then the at tachment of the second conjunct should be influenced by which other NP in the sentence it is semantically parallel with. So, the attachment of this ambiguous NP can be influenced in two ways: by factors that affect ambiguity resolution and by virtue of its semantic parallelism with a preceding conjunct. While these two accounts are difficult to tease apart, I will keep both in mind while analyzing the data resulting from the present experiment.

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34 CHAPTER 2 MATERIALS AND METHODS The Present Experiment The present experiment aims to add to the two debates central to the sentence processing literature as well as extendi ng the results of Hoeks (1997,19 99,2002), and determining whether lexical/semantic parallelism has an effect on the resolution of coordination ambiguities. While Hoekss results are intriguing, ther e are issues with his experiment al design that I intend to remedy. First, as he himself acknowledges, the data that he uses to argue that semantic information can override structural preferences in coordination ambiguities are flawed. He employs materials that have an animate NP and an inanimate NP surrounding the conjunction and. Based on corpus studies, coordinate phrases of th is type are extremely rare. Therefore, his data may only indicate that struct ural preferences were overridden by frequency or plausibility factors While this is interesting in and of itself, it does not constitute evidence that structural preferences have been overridden by semantic factors. Seco ndly, animacy itself is not purely semantic. As I discussed earlier, in some la nguages animacy has morpho-syntactic consequences and the possibility that it can have similar infl uences in English cannot be excluded. I aim to remedy these issues with the paradigm seen in (11) which manipulates whether the ambiguous noun-phrase is semantically associated with the subject of the first cl ause or the object of the first verb:

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35 Non-parallel, ambiguous 11a) The enemy talked to the king and the queen talked to the people. Q: Did the enemy talk to the queen? Non-parallel, non-ambiguous 11b) The enemy talked to the king but the queen talked to the people. Q: Did the enemy talk to the queen? Parallel, ambiguous 11c) The king talked to the enemy and the queen talked to the people. Q: Did the king talk to the queen? Parallel, non-ambiguous 11d) The king talked to the enemy but the queen talked to the people. Q: Did the king talk to the queen? This paradigm will allow me to examine the sa me issues that are central to the work of Hoeks, but has the following advantages: 1. All NP s are human and animate. This allows the reader to create equally natural conjunctions of both noun phrases and sentences. 2. The verbs are neutrally biasing. In combin ation with the selection of nouns this leads to elimination of plausibility confounds and eliminates differences in selectional restrictions or thematic fit between nouns and verbs across conditions. Th e manipulation is unequivocally semantic in nature, in contrast to Hoeks (1997). He manipulated the anim acy of the ambiguous noun phrase, while the paradigm in 11) manipulates whic h previous noun-phrase the ambiguous noun-phrase is associated with. If indeed, information on se mantics/lexical association is taken into account to guide parsing decisions, then difficulty in the disambiguating region should be reduced when the ambiguous NP is semantically associated with th e subject of the first cl ause. If this reduction in difficulty is observed, it would constitute compelling evidence against serial, depth-first models of parsing as in no way does the above manipulation have synt actic or structural ramifications. I also aim to extend the work of Ferreira (1996) and Christianson (2001), by examining the representational nature of the re sult of the parsing pro cess. The process of resolving coordination ambiguities is similar to the process of resolving the transitivity ambiguities in Christianson et al. (2001). I wi ll examine accuracy data in an attempt to

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36 determine whether full re-analysis is undertaken, if the end result of pars ing is a fully-detailed representation, if the sema ntic manipulation can have an effect on accuracy, and if the end result of parsing is fully specified and consiste nt with linguistic we ll-formedness conditions. Predictions The paradigm in 11) above crosses ambiguity ( but versus and ) with the semantic manipulation that varies which prior noun phrase the post conjunction noun is associated with. In the parallel conditions, the ambiguous noun phrase is highly associated with the subject of the main verb, while in the non-parallel conditions th e ambiguous noun phrase is associated with the object of the main verb. If the preference for NP coordination is replicat ed in this study, then reading times will be elevated at the second verb in the ambiguous conditions when compared to the non-ambiguous conditions. This increase in reading time reflects the fact that the nonambiguous conditions do not license the NP c oordination reading which is licensed in, and causes difficulty in, the ambiguous conditions. If there is no such preference, we will not see differences between ambiguous and non-ambiguous condi tions. If semantic information is taken into account and helps guide parsing decisions then reading time at the second verb (and downstream) in the parallel, ambi guous condition should be reduced when compared to the nonparallel, ambiguous condition. This reduction may manifest itself as a main effect of parallelism or an interaction between pa rallelism and ambiguity at th e point of disambiguation and subsequent positions. However, if this informa tion is ignored during initial parsing decisions then reading time will be comparable at this position. The reading time data gathered in the ambiguous region and post-ambiguity will determine whether information on semantic association is reducing processing difficulty in th ese constructions. If semantic information is strong enough to trigger S-coordi nation; we would expect an in crease in reading time for nonparallel conditions when compared to parallel cond itions. Accuracy data wi ll also be collected

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37 comparing ambiguous and non-ambiguous conditions on questions that probe the grammatical role of the ambiguous noun phrase. For example, the sentence The king talked to the enemy and the queen talked to the people, would be probe d with the question Did the king talk to the queen? If participants fully recover from the ambiguity and accu rately re-assign theta roles or successfully suppress the misint erpretation, then there will be no difference between these conditions. However, if partic ipants do not fully recover from a misinterpretation of the ambiguity, we will observe significantly lower accuracy to the ambiguous than non-ambiguous constructions. These data will help determine whether participants undertake full re-analysis when recovering from a coordination ambiguity. Questionnaire study In order to generate the experimental paradi gm described above with adequate control, it was first necessary to create noun sets that contained two associat es and one non-associate. For this purpose, a questionnaire study which was designe d to collect association ratings on pairs of nouns was conducted. Participants Fifty participants from the University of Florida population participated in the experiment. Data from ten participants were excluded due to their responses on an accompanying language questionnaire that show ed that they were not monolingual native speakers of English. Participants gave informed consent accordi ng to University of Florida IRB procedures, and were not compen sated for their participation.

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38 Materials For the purpose of selecting the nouns for th e self-paced reading study, forty-two noun pairs were chosen based on data from the Universi ty of South Florida association database (http://w3.usf.edu/FreeAssociation/). Nouns were selected based on the following criteria: The noun refers to a descriptive or occupational role that a human could fill, the noun is an animate count noun, the noun has a noun with the above charac teristics on its list of associates, and the cue-to-target association strength between the two nouns is at leas t .20 as listed in the association database. A cue-to-target strengt h of .20 indicates that when pr ompted with the cue, 20% of participants responded with the ta rget. The original forty-two nouns and their associates thus made up forty-two pairs of associated nouns. Based on intuition, a th ird, unassociated, noun was added to each pair yielding triple ts. Crucially, this noun could not a ppear on the list of associates of either of the other two nouns. By splitting the triplets into thei r constituent pairs (ABC AB, CB, e.g, king-queen; enemy-queen), eighty-four pairs of nouns were created; forty-two that were associated and forty-two that were una ssociated. These eighty-four noun pairs were randomly intermixed with eighty-four filler pairs, yielding 168 pairs of nouns in total. These distractors were designed to mask the experime ntal manipulation as well as to encourage the participant to utilize the entire rating scale. For example, the part icipant could be asked to rate the association between donkey an d gymnast, or coal and tree. The noun pairs were pseudorandomized so that no experimental pairs followed each other, and the pages of the questionnaire were presented randomly to eliminate the effect of presentation order on the participants ratings.

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39 Procedure The participants task was to provide a rating of how asso ciated the two nouns were by circling a number between 1 (completely unass ociated) and 7 (completely associated). Participants were given instru ctions to answer based on thei r initial intuitions, and given examples in order to familiarize them with th e rating scale. The participants were also encouraged to employ all parts of the rating scal e. The questionnaire stud y lasted 15 minutes. Analysis We first calculated mean ratings for all eighty-four experimental pairs (42 associated pairs and 42 unassociated pairs). Then t-test s were conducted examining the difference between mean ratings of associated and unassociated pair s across items and comparing the associated and unassociated pairs by item. Results The results of the t-test comparing the a ssociated and unassociate d conditions revealed that overall there was a significant difference between the ratings [t(1,41)=20.3, p < .001). The results of the individual t-tests between the consti tuent pairs of each triplet yielded twenty-eight triplets whose rating difference was significant at an alpha level of .001 (mean associated rating = 5.68, mean unassociated rating 3.25). These twenty-e ight triplets were th en employed to create the experimental materials for the self-paced reading study. Self-Paced Reading Study Participants Forty-three participants (26 female, 17 male ) from the University of Florida population participated in the experiment for course cr edit, and gave informed consent according to University of Florida IRB procedures. All partic ipants had no known speech or hearing disorders as indicated by self report. The mean age of participants was 20.4 years (range 18 to 28). Data

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40 from seven participants were ex cluded from analysis based on responses to the accompanying the language questionnaire that showed that they were not monoli ngual native speakers of English. Thus, the data from 36 participants was analyzed. Materials The twenty-eight noun triplets from the que stionnaire study were inserted into the experimental paradigm (11), yieldi ng twenty-eight sets of experimental items. Note that in the critical region starting from the determiner after the conjunct, the four co nditions are physically similar. Across the twenty-eight sets, four neutral verbs (talk to, w alk with, meet with, ask about) were each repeated seven times. This was done to ensure that there were no differences in thematic fit between noun and verb acro ss items, and that the ambiguous noun in postconjunction position could serve equa lly well as the agent and the patient of the verb. Each participant saw seven items from each experimental condition as well as fifty-six fillers. The fillers were constructed with the following aims: to balance out the number of S and NP coordinations across the entire se t of experimental materials thus precluding the development of implicit processing strategies by th e participant, to vary the clau se boundary so that it could not be predicted purely by linear position, to ensu re that all conjunctions not signal a clause boundary, and to form as natural a set of materi als as possible by introducing different verbs and types of nouns. Four item groups were created by dividing th e twenty-eight experimental items into groups of seven. Across these groups, the diffe rence between associated and unassociated pairs was held constant such that a comparison of th ese conditions yielded non -significant results. A one-way ANOVA with the factor group was co nducted, yielding a p-value of .878. This confirmed that across item groups, there was no si gnificant difference in the difference between

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41 associated and unassociated pairs. Unfortunately because of the manner in which the critical nouns were selected and the limited number of creatable noun pairs with the desired characteristics; we were unable to balance length and frequency acr oss lists or item groups. We instead focused on balancing association streng th, which is critical to the experimental manipulation. The item groups were then distributed across four participant lists and counterbalanced. In this way each participant only saw each item in one condition, and all items were seen an equal number of times in all conditions. Fillers and experimental items were pseudo-randomized such that no two experimental items followed each other. Participants were probed with comprehens ion questions after each sentence. These questions were designed to probe the role assigned to the ambiguous noun phrase after the conjunction in the experimental conditions, in or der to determine whether the reader recovered from the garden path. For example, the senten ce, the enemy talked to the king and the queen talked to the people, would be probed with the se ntence, Did the enemy talk to the king? The remainder of the comprehension questions probed relationships between the other arguments in the sentences. The complete set of experimental materials and some examples of fillers sentences are attached in the appendix. Procedure Participants were individually tested. S timulus presentation and data acquisition was controlled using E-Prime (Psychology Software Tools) running on a PC. The experiment employed a self-paced reading, moving window pa radigm. Before beginning the experiment, each participant was familiarized with the task with instructions and a brief practice block of five items. After we were certain th at the participants understood the task, the experiment began and proceeded as follows: The trial began with a se ries of dashes on the screen which represented

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42 each word of the sentence (with the number of dashes corresponding to the number of letters in each word), and the participant pressed the ente r button on the button box for the first word (presented in size 15, courier new; black text on white screen) to appear. Each successive press of the enter button caused the current word to disappear and the next word in the sentence to appear. This continued to the end of the sent ence at which point the question related to the previous sentence appeared on the screen with in structions to press the Y: button for yes, and the N button for no. Once the participant answ ered the question, a press X for next screen appeared. Once the participant pressed the X bu tton, the screen disappear ed and the next trial proceeded as described above. Analysis Reaction time data from the remaining thirty-s ix participants were first trimmed using the following procedures: Any data point exceedi ng 3000 msec was treated as missing during the analysis, this procedure affected .007% of the data. Additionall y, means were calculated at each word position for each condition for each participant and any data point that exceeded the mean plus or minus 2 standard deviations was replaced with the mean, affecting .05% of the data. A repeated measures ANOVA was conducted on the part icipant (F1) and item means (F2) with the factors ambiguity (2 levels) and pa rallelism (2 levels) as within subject (item) factors, and item as a between item factor and list as a between su bject factor. Question accuracy and RT data were analyzed using a two-way ANOVA with factors ambiguity and parallelism.

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43 CHAPTER 3 RESULTS Comprehension Data Accuracy Overall, questions probing the experimental ma terials were answered quite accurately. Table 1 summarizes comprehension data on the four experimental conditions The results of the two-way ANOVA revealed a significant e ffect of ambiguity [F1(1,35)=14.316, p < .001; F2(1,27)=4.44, p < .05], with accuracy on questions probing ambiguous items significantly lower (mean =89.3%) than accuracy on non-ambiguous ite ms (mean= 93.7%). There was also an effect of parallelism, that was significant by su bjects but not by items [F1 (1, 35)=6.171, p < .05; F2 (1,27)=2.766, p=.108], with accuracy on questions probing parallel items higher (93.7%) than on the non-parallel items (88.8%). Additiona lly, the interaction be tween ambiguity and parallelism was significant [F1 (1,35)=36.594, p < .001; F2(1,27)=17.016, p < .001]. The pattern of the interaction reveals that there is a large accuracy differe nce between the two non-parallel conditions, while the mean accuracy to the parallel conditions is mu ch closer. Post-hoc Tukeys pairwise comparisons on accuracy by condition i ndicated that accuracy on questions probing the non-parallel, ambiguous condition wa s significantly lower than fo r on all other experimental conditions (p < .001 in all three comparisons). Reaction Time Question response times patte rn with the accuracy data The results of the ANOVA indicated that the interaction between pa rallelism and ambiguity was significant [F1 (1,35)=13.367, p < .001; F2 (1,27)= 14.008, p < .001]. The pattern of the inter action reveals that there is a large reaction time difference between the two non-para llel conditions, while the mean reaction time to the parallel condi tions is much closer There was a marginal main effect of

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44 ambiguity [F1(1,35)=3.723, p=.062; F2 (1,27)=3 .089, p=.090], though the means do illustrate that participants t ook longer to answer questions pr obing ambiguous (2778 ms) than nonambiguous (2547 ms) items. There was no main effect of parallelism [F1(1,35)=1.347, p=.254, F2 (1,27)=.868, p=.360]. Mean reading times do how ever indicate that subjects took longer to answer questions probing nonparallel items (2742 ms) than parallel items (2578ms). Reading Time Data A GLM repeated measures ANOVA was perfor med on all experimental items with the within-subject factors ambiguity (ambiguous or not) and para llelism (parallel or not), and the between-subject factors list a nd item group. An analysis includ ing only correct items did not yield qualitatively different results, and will therefore not be discussed. Table 2 presents the reading times at position 5 (the determiner of the pre-conjuncti on noun phrase) and each subsequent position and figure 1 su mmarizes reading times at all pos itions in the experimental sentences. The ANOVA revealed an effect of parall elism at the pre-conjunction noun that was significant by items [F1(1,32)=2.98, p=.09; F2(1, 24)=7.12, p< .05] and an effect at the postconjunction noun that was significant by subjects but marginal by items [F1(1,32)=5.125, p< .05; F2(1,24)=3.199, p=.086], with the nonparallel items taking longer to re ad than the parallel items at both positions. There was al so an interaction between ambi guity and parallelism at position 11, which was significant by subjects onl y [F1(1,24)=4.575, p < .05; F2(1,32)=1.45, p=.24].1 The pattern at this position reve als that the non-paral lel ambiguous condition takes the longest to 1 The discrepancy between p-values in the F1 and F2 anal yses can be explained by the manner in which the items were controlled. Controlling for association between as sociated and non-associated pairs across lists and item groups dictated that frequency and length could not be adequately controlled for. We believe that this led to the differences in significance in the F1 and F2 analyses.

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45 read, while the parallel ambiguous condition and the two non-ambiguous conditions have virtually identical means. The analysis revealed no main effects of ambiguity at any position. Main effects of and interactions with list and item group ranged fr om p=.018 to p=.969, and all effects at other positions were non-significant. Table 1-1: mean RT and accuracy per condition NonParallel, Amb NonPar allel, NonAmb Parallel, AmbParallel, NonAmb Accuracy 81.1% (.39) 96.8% (.12) 97.2% (.15) 90.6 %(.29) RT 3051 (1069) 2433 (785) 2505 (813) 2652 (1021) Table 1-2: mean (SD) r eading times by condition the N conj. the N V P the N. N-P, A 356(14) 510(41) 426(19) 364(11) 442(29) 421(19) 364(12) 346(11) 725(51) N-P, N-A 370(15) 473(32) 411(16) 367(13) 460(27) 414(22) 345(9) 337(10) 688(35) P, A 363(24) 463(34) 446(22) 377(14) 417(19) 411(18) 346(11) 348(10) 702(51) P, N-A 361(12) 459(32) 425(21) 383(18) 436(25) 393(14) 346(9) 353(10) 719(47)

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46 300 350 400 450 500 550 600 650 700 750The N V P the N conj. the N V P the N N-P, A N-P, N-A P, A P, N-A Figure 2-1: mean reading times at each position (by subjects)

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47 CHAPTER 4 DISCUSSION The goal of the present study was to provide da ta that would help re solve two of the more prevalent debates in the sentence processing literature. By empl oying a manipulation that varied which previous noun phrase the ambiguous noun phrase in a coordination ambiguity was semantically associated with, and probing the attachment of this ambiguous noun phrase with comprehension questions; the present study was de signed to provide data that distinguished between constraint based versus syntax-first parsers, and between e xhaustive, algorithmic parsing and parsing that outputs merely good-enough representati ons. We hypothesized that if semantic information is taken into account dur ing parsing, reading time at the disambiguating region in the non-parallel, ambiguous condition w ould be elevated in comparison with the parallel, ambiguous condition; and that differenc es in accuracy to ambiguous and non-ambiguous conditions would provide evidence for a pa rser that sometimes outputs good-enough representations. Comprehension and reading time data will be discussed before they are placed in the context of models of processing and representation. Comprehension Data The data reveal that subjects answered questions probing non-ambiguous items more accurately than questions probing their ambiguous counterparts. Subjects were also more accurate when responding to questions in the parallel conditions than when responding to the non-parallel conditions. These two factors also interacted signif icantly, with a large accuracy difference between the two ambiguous conditions th at was almost twice the difference between the two non-ambiguous conditions. The demonstration that participants res pond more accurately to questions probing nonambiguous (93.7%) than questions probing ambiguous items (89.3%) supports the notion that

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48 participants sometimes do not overw rite or suppress their initial in terpretation of a sentence, even when that interpretation is erroneous. Extending results of Ferreira et al (2002) and Christianson et al. (2001) with a different c onstruction, these results appear to demonstrate that the initial misinterpretation of a sentence can persist even in the face of disambiguating input. It appears that in the ambiguous conditions, readers some times attach the ambiguous noun phrase as an object of the first verb (based on either minimal attachment or the higher frequency of the NP coordinate structure). Even after the main ve rb of the second clause is encountered and it becomes clear that the ambiguous noun phrase is actua lly a subject, this r eading survives to the extent that it can effect question answering by lowering accuracy. The present results cannot distinguish between the different accounts of this effect (unde rrepresentation, a lack of reanalysis, or persistence of the initial analysis ), but they do seem to indicate that readers sometimes rely on representations that are not th e result of exhaustively analyzing the input until the correct structure is built. The comparison of accuracy to parallel and non-parallel conditions also reached significance, as did the interac tion between ambiguity and parallelism. The accuracy to parallel conditions (93.7%) was higher than accuracy to non-p arallel items (88.8%). These results provide evidence that purely seman tic information can affect comprehension of a sentence. The data on the accuracy to quest ions probing non-parallel ambiguous (81.1%) and parallel, ambiguous trials (97.2%) ar e also very interesting. This large difference in accuracy to syntactically identical ambiguous constructions may be because participants are relying on semantics when answering these questions. In the case of the parallel ambiguous conditions, semantic information supports the correct structur e in which the associated nouns are subjects of their own clauses. Accuracy is high in this condition. In the non-parallel conditions, the semantic information supports the wrong struct ure in which the associated nouns are both

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49 objects, and consequently accuracy is low in this condition. If this is the case, then it can provide some insight into a heuristic processor that does not always decommit from its initial interpretation and/or revise after mis-anal ysis. This type of processor may output a representation that is structurally underspecified due to a lack of re-analysis, or it may output multiple structures that represent all interpretations entertained during the parsing process leading to interference between correct and in correct structures. Regardless of the exact mechanism leading to deficits in structural re presentation, it appears th at the language system can recruit other sources of information to mask these inadequacies. When probed on a sentence of which it has an inadequate representation, the system resorts to semantic sources of information. When these cues are present a nd supportive, they are enough to override the difficulty engendered by an inade quate representation. Th is is evidenced by the high accuracy to the parallel, ambiguous condition (97.2%). Howeve r, when these cues are not present or support the wrong interpretation, the system is left to deal with its deficits in structural representation and accuracy drops sharply (81.1%). The reaction time data gathered from the comprehension questions supports the error patt erns described above. While co mparisons of the experimental factors do not reach significance, the pattern of the means supports the above conclusions. The non-parallel, ambiguous condition wh ich yielded the lowest accur acy also yielded the highest reaction time (3051 ms). This indicates that there was no speed-accuracy tradeoff for the participants. The difference between parallel ambiguous (2505 ms) a nd non-parallel, ambiguous (3051) mirrors the large difference in accuracy to these conditions and against suggests that semantics can be recruited to facilitate off-line comprehension. When sema ntic cues are present, subjects respond quickly and accurately. When these cues are not present, subjects respond slowly and less accurately.

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50 Reading Time Data The data reveal a main effect of paralle lism at both the preand post-conjunction nouns, with non-parallel items taking longer to read th an parallel items at both positions. There was also a significant interaction be tween parallelism and ambiguity at the post disambiguating verb preposition which resulted in a three versus one pattern. The non-parallel, ambiguous condition showed an increase in reading time at this posi tion when compared to a ll other conditions. Interaction of Parallelism and Am biguity at the Post Disambiguati ng Verb Preposition (Position 11) As our interest is most sharply focused in the disambiguating region of the sentence, let us begin a discussion of the results there. The interaction between parall elism and ambiguity at this position is perhaps the most intriguing finding in this study. While the interaction was only significant by subjects and not by items (see footnot e 1), this effect may provide evidence that semantic information can override processi ng difficulty in a s yntactically ambiguous environment. At the preposition, the pattern of the means reveals that the parallel, ambiguous condition patterns with the two non-ambiguous conditions. Relative to these conditions, the nonparallel ambiguous condition shows an elevati on in reading time of approximately 20 ms reflecting processing difficulty. Th ese data appear to demonstrate that semantic information can eliminate the garden path effect at the disa mbiguating verb, as no evidence of processing disruption is seen in the para llel, ambiguous condition. This patte rn of reading times is best explained with a constraint-based account of pars ing that resolves ambiguity through the process of structure competition. Constraint based models of sentence processing state that as the parser incrementally interprets the input, multiple structur es consistent with the input are built based on all information currently available to the parser These structures compete, in that they become relatively more or less active than thei r competitors as the sentence unfolds and more

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51 information becomes available, and at the end of the sentence the structure with the highest activation wins. Crucially, th is type of model predicts th at when two analyses receive approximately equal support from the input, severe competition will occur and processing difficulty will result. In contrast, when one analysis receives virtually all of the support, processing will be facilitated because of a lack of competition. The crucial sources of information here are the NP-coordination prefer ence, semantics, and processing biases that develop throughout the experiment. Due to the variable contributions of these sources of information at prior positions in the sentence, the parser reaches the di sambiguating region with structures that are competing to different degr ees in the two ambiguous conditions. The differing degree to which these structures compete can explain the data at the preposition, and explain why the parallel, ambiguous condition patterns with the non-ambiguous conditions at this position. As the parser processes the conjunction and the post-conjunction region, both S and NP coordinate structures become active. Their relati ve levels of activation are influenced in this region by semantics, general processing princi ples, and parsing pref erences that develop throughout the experiment. Differe nt cues are available in each condition, and this leads to variable levels of activation (a nd therefore competition) betwee n the two competing structures across the conditions. As the parser reaches the preposition in the non-parallel, ambiguous condition the two structures are competing greatly due to the two licit stru ctures being activated to approximately the same extent. This causes an elevation in reading time when the parser encounters the disambiguating verb and it become s evident that the S-coordination reading is correct. However, in the parallel ambiguous c ondition, the S-coordinate structure is already highly active due to the contribution of semantics at previous positions in the sentence. This eliminates processing difficulty in the disambigua ting region as the correct structure is already

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52 highly active. The observation that the para llel, ambiguous condition shows no increase in reading time relative to the two non ambiguous cons tructions suggests that the contribution of semantics is enough to boost the activation of the S-coordination reading to the extent that it is virtually identical to the activation of the S st ructure when it is unambiguously signaled by the preposition but. These results are hard to reconcile with a syntax-first parser, even one that claims that semantic information can be recruited rapidly to facilitate re-a nalysis. The sentences are syntactically identical at this position, licensing the same two structures, so differences among the conditions are unlikely to be based on syntactic considerations Additionally, a claim that a syntax-first parser is si mply recruiting semantic information to re-analyze at this position would be unfounded. If this were the case, th en both ambiguous conditions would show an elevation in reading times compared to th e non-ambiguous conditions, although perhaps this effect would be smaller for the parallel conditio ns, since semantic information could ease reanalysis. This pattern is not present in the data, as only the non-parallel ambiguous condition shows an elevation compared to the non-ambiguous items. We therefore believe that the patterns at this position are generated by the variable contributions of se mantics in a constraint-based competition model that also calculates the probabili ty of alternative structures based on general parsing principles and processing strategies that are sensitive to the frequency of occurrence of alternative structures in the materials set. Main Effect of Parallelism at the Post-Conjunction Noun (Position 9) The main effect of parallelism at this positi on is also interesting. The direction of the effect, with the non-parallel items taking longer to read than their pa rallel counterparts, eliminates the possibility that this is simple local priming between noun-phrases as the effect is in the wrong direction. Here is the experiment al paradigm again (with position 9 in bold), provided for clarity of discussion:

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53 Non-parallel, ambiguous The enemy talked to the king and the queen talked to the people. Non-parallel, non-ambiguous The enemy talked to the king but the queen talked to the people. Parallel, ambiguous The king talked to the enemy and the queen talked to the people. Parallel, non-ambiguous The king talked to the enemy but the queen talked to the people. The difference in reading time between the non-ambiguous conditions can again be explained through a constraint based model of pa rsing. While competition is limited because the conjunction but only licenses S-coordinati on, the contribution of seman tics can still explain the increase in reading time in the non-parallel, non-ambiguous condition compared to the parallel, non-ambiguous condition. In the parallel conditi on, the semantics of the noun phrase support the S-coordination that is highly activated, while in the non-para llel condition semantics provides interference against the S-coordina te reading. This leads to a re duction of the activation of the Scoordinate structure, and thus an increase in reading time to the non-parallel, non-ambiguous condition. The difference between the two ambiguous c onditions at this position is perhaps more interesting. One of the primary goa ls of the experiment was to de termine if semantic association could influence the attachment of this ambiguous noun phrase. It appears as if it can, and the interaction of semantics, gene ral parsing principles, and expe riment specific strategies can explain the differences between ambiguous conditions at this position. In contrast to the nonambiguous items above, when the parser encounters the conjunction and two structures become active as and licenses both S and NP coordination. The initial pattern of ac tivation should favor the NP-coordinate structure, as it is this struct ure that is predicted by mi nimal attachment and the observation that NP coordination enjoys a large a dvantage over S-coordina tion in terms of realworld frequency of occurrence (Hoeks, 2006). As the parser reaches the post conjunction noun

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54 in these constructions, the contributions of expe riment specific biases and semantics generate a different pattern of activation ac ross the ambiguous conditions. Th is leads to a high degree of competition in the non-parallel condition, and a c onsiderable advantage for the S-coordinate structure in the parallel condition. This variab le level of competiti on can explain both the elevation in reading time at this position for the non-parallel items as well as provide the reason that these two conditions reach the disambiguating region with di fferent levels of competition between alternatives as described above. The co ntribution of semantics is clear; it supports Scoordination in the parallel conditions and NP-c oordination in the non-parallel conditions, but the contribution of experiment-specific parsing prin ciples must be elucidated. As stated earlier, NP coordination is statistically much more frequent in natu ral language, this assertion is supported by completion and corpora studies (Hoeks, 2006). However, following psycholinguistic research methods, the number of S and NP coordinations in the present study was balanced to inhibit the devel opment of processing strategies throughout the experiment based on the probability of encountering one of the two alternative structures that and licenses. Based on the data, it appears that this ba lancing had the opposite effect a nd actually induced the parser to modify its attachment preferences. It appears th at the parser is sensitive to the discrepancy between the probability of encounter ing one of two alternate structur es in the real world and the same probability within the materials set. This discrepancy causes the pa rser to modify general principles to lower processing diffi culty across the board. This lead s to an attenua tion of the NPcoordination preference, and enable s semantics to have more of an effect in the post-conjunction region. This idea is supported by an analysis that included time as a factor to determine whether participants are reacting to the disambiguating region di fferently at the beginning and end of the experiment. The experimental sent ences that occurred durin g the first 25% of the

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55 experiment show a robust garden path effect at the disambiguating ve rb in the two ambiguous conditions indicating that the parser is initia lly creating NP coordina te structures when encountering and this effect averages 45 ms. However, th is effect has been reduced to 7.5 ms in experimental trials that occur during the last 25% of the experiment. Wh ile the interaction of ambiguity and time does not reach significance at the verb due to the necessity of only analyzing a subset of items [F 1(1,35)=1.91, p=.168], this pattern is suggestive that the parser employed the frequency with which S and NP coordi nate structures occur within the experiment to modify the NP coordination preference and reduce processing difficulty as the experiment progressed. This interpretation generates testable predictions. Namely, that by modulating the frequency of alternative structures within an experimental set either towards or away from preferences that have been established by the pa rser in response to real world frequencies; varying results will be observed. If this pr ediction is proven true, it would be of great methodological consequence. For instance, if a set of materials was created in which S coordinations were much more frequent than th eir NP counterparts (oppos ite of the distribution in natural language), one would predict garden path effects in the disambiguating region of the NP coordinate structures. These results are di fficult to interpret under a syntax-first view, as semantic information appears to be having an e ffect before the disamb iguating region triggers revision. The main effect of parallelism at the pre-co njunction noun is difficult to interpret. At this position, non-parallel conditions take longer to read than parallel c onditions. This effect is not due to length or frequency differences between the nouns in the two conditions, and cannot be explained through recourse to synt ax-first or constraint based pa rsing models. One speculative account is that the participants have more troubl e constructing a mental model in the non-parallel

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56 conditions due to the arrangement of the noun phrase s. In this case, plau sibility at the real world level is the crucial factor. This account would have to be further pursued by conducting norming studies on the experimental materials. The Relationship between Comprehension and Reading Time Data When interpreting the reading time and comprehension data simultaneously, a clear picture emerges. It appears that the semantic manipulation in the experimental materials has an effect on both online and offline linguistic proc essing. In terms of online processing, we see clear effects of the semantic manipulation at both the post-conj unction noun and the post-verbal preposition. At these positions, the add itional semantic information provided by the manipulation facilitates processing and reduces the difficulty that is encountered in the disambiguating region of the sentence by reducing the level of competition between alternative structures. In terms of offline processing, this same semantic information increases accuracy and decreases response time when answering questions The experimental condition that generates the most processing difficulty online also causes th e most difficulty offline, as subjects spend longer and answer less accurately than to any other condition. Syntax-First versus Constraint-Based Models The results of this experiment are most co mpatible with a constraint-based model of sentence processing in which alte rnative structures compete based on evidence from the input. It is very difficult to reconcile this data with a synt ax-based parser that grants primacy to structural factors. At the post-conjunction noun in the expe rimental materials there is a main effect of parallelism. At this position non-parallel conditions show an incr ease in reading times compared to parallel conditions (both ambiguous and non-ambiguous). Crucially, the non-parallel ambiguous condition takes longer to read than the parallel, ambiguous condition. This effect is difficult to explain without recourse to some nonstructural factors. At this position in the

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57 sentence, when comparing parallel to non-pa rallel ambiguous, the structures are equally ambiguous. In both sentences at this position, bo th the S and NP coordination readings are licensed by the rules of syntax. The only diffe rence between these items is in the lexical association between the lexical item currently bei ng parsed and a lexical item somewhere else in the sentence. What then causes the increase in read ing time? We believe that this elevation is a result of increased competiti on between alternatives receivin g equal amounts of support in the non-parallel ambiguous condition. An explanation ba sed purely on syntax fails here, as does an account in which a syntax-based parser recruits semantic information during re-analysis as the disambiguating region has yet to be reached and re-a nalysis has therefore yet to be initiated. At the post-disambiguating verb pre position, there is a significant interaction between parallelism and ambiguity that we also believe to be ev idence for constraint-based parsing in these constructions. At the preposition, evidence of processing difficulty only appears in the nonparallel, ambiguous condition. The parallel ambi guous condition does not show this disruption and the mean reading time at this position is virtually identical to the means of the nonambiguous conditions. We feel that this lack of difficulty in the parallel ambiguous condition is due to the heightened activation of the S read ing over the NP reading due to the relative contributions of constraints at the post-con junction noun. Even proponents of a syntax-based parser that recruits semantic information for ra pid re-analysis would have trouble explaining this effect at this position. Perhaps this is the case and the methodology employed lacked the sensitivity to detect residual processing difficulty, but the reading time data appear to illustrate that the semantic information provided by the prior context is enough to eliminate processing difficulty entirely. For these reasons, we feel that our data are most consistent with a constraint based parser that considers all available sources of information to create multiple structures in

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58 parallel, with the structure that receives th e most support from the input mapping on to the meaning of the sentence. Good-Enough Representations in Sentence Processing A secondary aim of this research was to discriminate between fully detailed and good enough representations in senten ce processing. While the data collected here is relatively limited in this regard, it does point to a sentence processor that outputs representations that are not always the result of exhaustively analyzi ng the input. Our accuracy data indicate that participants do not always re-analy ze their interpretation or suppress it to the extent that it cannot influence comprehension. It appear s that this initial mis-interpretation can persist to the extent that it can affect comprehension. Interestingly, our data also suppor t the notion that this type of heuristic syntactic processing may be aided by semantic cues in a manner that masks its representational defici ts. When support from semantics was not present in the ambiguous constructions, participants experienced a huge drop in accuracy when compared to when the semantic cues were present. We feel that this type of processor may use these additional cues to mask when structural processing is not comple te and only good enough, in the same way that employing semantic cues help Brocas aphasics ma ke structural decisions when their receptive grammatical deficits prevent them from undertaki ng a complete analysis. The degree of fall-off once these cues are taken away is not as dramatic in the current participants, but conceptually we believe the recruitment of semantic cues to ma sk structural deficits may be the same. In conclusion, our accuracy data are not conclusive in either direction, but do appear to support the notion that comprehenders often rely on representations that are not fully detailed in terms of the correct structure of the input either because of a lack of full re-ana lysis or an inability to suppress the representation that resulted from an incorrect parse.

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59 CHAPTER 5 CONCLUSION The reading time study described here was desi gned to investigate whether information regarding semantic association would facilitate processing in the disambiguating region of a coordination ambiguity and also whether the end result of parsing this construction is fully specified. The answer to the first question appear s to be yes. During the experiment, processing difficulty appeared to be eliminated by the seman tic manipulation to the extent that the parallel, ambiguous condition patterned with the two non-ambiguous conditions at the postdisambiguating verb preposition. There was also an effect of the seman tic manipulation in the pre-disambiguating region, providing further evidence for the influe nce of semantics on the firstpass parse. In terms of the nature of the out put of parsing these constructions, we observed significant differences in accuracy to ambi guous and non-ambiguous constructions; indicating that perhaps participants weren t completely re-analyzing the i nput or were failing to suppress the initial incorre ct parse. Evidence was also found that suggests that the parser may modifiy attachment preferences in res ponse to the discrepancy between the frequency of alternative structures in the real world and the materials set. These findings provide support for a constr aint-based parser that takes semantic information into account when build ing the parse, and that is also sensitive to the probability of encountering possible alternate struct ures in the real world and in the context of an experiment. The parser may output underspecified representations or fail to s uppress representati ons that lead to clashes in terms of thematic role as signment and deficits in comprehension.

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60 CHAPTER 6 FUTURE WORK The data presented here represent only an in itial investigation into the effects that nonstructural sources of information can have on the attachment of the ambiguous noun phrase in a coordination ambiguity. Future projects include investigating the manipulation described herein with more sensitive experimental techniques, su ch as eye-tracking or Event Related Potentials (ERPs). I also plan to investigate the effects that a fine grai ned plausibility ma nipulation or verb differences at the discourse level may have on th e parsers preferences at this noun phrase. A study currently under preparation will investigate the role that the relative frequency of NP and S coordination within the material s set can have on the attach ment of this noun phrase. Conclusions drawn from the data generated by this study will be of great theoretical interest.

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61 APPENDIX A EXPERIMENTAL MATERIALS 1. a. The resident talked to the electrici an and the plumber talked to the foreman. b. The resident talked to the electrician but the plumber talked to the foreman. c. The electrician talked to the reside nt and the plumber talked to the foreman. d. The electrician talked to the resident but the plumber talked to the foreman. 2. a. The enemy talked to the queen and the king talked to the people. b. The enemy talked to the queen but the king talked to the people. c. The king talked to the enemy a nd the queen talked to the people. d. The king talked to the enemy but the queen talked to the people. 3. a. The guest talked to the wife and the husband talked to the locals. b. The guest talked to the wife but the husband talked to the locals. c. The wife talked to the guest and the husband talked to the locals. d. The wife talked to the guest a nd the husband talked to the locals. 4. a. The client talked to the architect a nd the builder talked to the contractor. b. The client talked to the architect but the builder talked to the contractor. c. The architect talked to the client and the builder talked to the contractor. d. The architect talked to the client but the builder talked to the contractor. 5. a. The victim talked to the policeman and the fireman talked to the family. b. The victim talked to the policeman but the fireman talked to the family. c. The policeman talked to the victim and the fireman talked to the family. d. The policeman talked to the victim but the fireman talked to the family. 6. a. The parent talked to the teacher a nd the student talked to the classmate. b. The parent talked to the teacher bu t the student talked to the classmate. c. The teacher talked to the parent an d the student talked to the classmate. d. The teacher talked to the parent but the student talked to the classmate 7. a. The adult talked to the expert and the novice talked to the class. b. The adult talked to the expert but the novice talked to the class. c. The expert talked to the adult and the novice talked to the class. d. The expert talked to the adult but the novice talked to the class.

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62 8. a. The coach walked with the swimme r and the diver walked with the fan. b. The coach walked with the swimme r but the diver walked with the fan. c. The swimmer walked with the coach and the diver walked with the fan. d. The swimmer walked with the coach but the diver walked with the fan. 9. a. The master walked with the maid and the butler walked with the kids. b. The master walked with the maid but the butler walked with the kids. c. The maid walked with the master and the butler walked with the kids. d. The maid walked with the master and the butler walked with the kids. 10. a. The parents walked with the sister a nd the brother walked with the grandparents. b. The parents walked with the sister but the brother walked with the grandparents. c. The brother walked with the parents a nd the sister walked w ith the grandparents. d. The brother walked with the parents but the sister walked with the grandparents. 11. a. The friend walked with the blonde and the brunette walked with the salesman. b. The friend walked with the blonde but the brunette walked with the salesman. c. The blonde walked with the friend and the brunette walked with the salesman. d. The blonde walked with the friend a nd the brunette walked with the salesman. 12. a. The servant walked with the lady and the gentleman walked with the children. b. The servant walked with the lady but the gentleman walked with the children. c. The lady walked with the servant a nd the gentleman walked with the children. d. The lady walked with th e servant and the gentleman walked with the children. 13. a. The neighbor walked with the son and the daughter walked with the cop. b. The neighbor walked with the son but the daughter walked with the cop. c. The son walked with the neighbor and the daughter walked with the cop. d. The son walked with the neighbor but the daughter walk ed with the cop. 14. a. The trainer walked with the pitcher and the catcher walked with the umpire. b. The trainer walked with the pitcher but the catcher walked with the umpire. c. The pitcher walked with the trainer and the catcher walked with the umpire. d. The pitcher walked with the trainer but the catcher walked with the umpire.

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63 15. a. The scout met with the actress an d the actor met with the audience. b. The scout met with the actress bu t the actor met with the audience. c. The actor met with the scout a nd the actress met with the audience. d. The actor met with the scout bu t the actress met with the audience. 16. a. The reporter met with the judge and the jury met with the criminal. b. The reporter met with the judge but the jury met with the criminal. c. The judge met with the reporter and the jury met with the criminal. d. The judge met with the reporter bu t the jury met with the criminal. 17. a. The intern met with the producer and the director met with the extra. b. The intern met with the producer but the director met with the extra. c. The producer met with the intern and the director met with the extra. d. The producer met with the intern a nd the director met with the extra. 18. a. The candidate met with the faculty and the staff met with the dean. b. The candidate met with the faculty but the staff met with the dean. c. The faculty met with the candida te and the staff met with the dean. d. The faculty met with the candidate but the staff met with the dean. 19. a. The student met with the chemist and the biologist met with the technician. b. The student met with the chemist but the biologist met with the technician. c. The chemist met with the student a nd the biologist met with the technician. d. The chemist met with the student but the biologist met with the technician. 20. a. The slave met with the prince and the princess met with the ruler. b. The slave met with the prince but the princess met with the ruler. c. The prince met with the slave and the princess met with the ruler d. The prince met with the slave but the princess met with the ruler 21. a. The boss met with the receptionist and the secretary met with the representative. b. The boss met with the receptionist but th e secretary met with the representative. c. The receptionist met with the boss and the secretary met with the representative. d. The receptionist met with the boss but the secretary met with the representative.

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64 22. a. The passenger asked about the co-pilot and th e pilot asked about the stewardess. b. The passenger asked about the co-pilot but th e pilot asked about the stewardess. c. The co-pilot asked about the passenge r and the pilot asked about the stewardess. d. The co-pilot asked about the passenger but the pilot asked a bout the stewardess. 23. a. The officer asked about the killer and the victim asked about the punishment. b. The officer asked about the killer but the victim asked about the punishment. c. The killer asked about the officer and the victim asked about the punishment. d. The killer asked about the officer but the victim asked about the punishment. 24. a. The writer asked about the hero an d the villain asked about the family. b. The writer asked about the hero bu t the villain asked about the family. c. The hero asked about the writer and the villain asked about the family. d. The hero asked about the writer bu t the villain asked about the family. 25. a. The referee asked about the winne r and the loser asked about the crowd. b. The referee asked about the winner but the loser asked about the crowd. c. The winner asked about the refere e and the loser asked about the crowd. d. The winner asked about the referee but the loser asked about the crowd. 26. a. The customer asked about the ch ef and the cook asked about the busboy. b. The customer asked about the chef but the cook asked about the busboy. c. The chef asked about the custom er and the cook asked about the busboy. d. The chef asked about the customer but the cook asked about the busboy. 27. a. The relative asked about the brid e and the groom asked about the band. b. The relative asked about the brid e but the groom asked about the band. c. The bride asked about the relative and the groom asked about the band. d. The bride asked about the relative but the groom asked about the band. 28. a. The child asked about the minister a nd the preacher asked about the congregation. b. The child asked about the minister but the preacher asked about the congregation. c. The minister asked about the child a nd the preacher asked a bout the congregation. d. The minister asked about the child but the preacher asked about the congregation.

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65 APPENDIX B FILLER SENTENCES And NP coordination 1. The lion hunted for a zebra and a buffalo in the long grass. 2. The manager spoke with the assistant a nd the janitor during their lunch break. Or NP coordination 3. Alex had to meet with Jason or Stephen to work on their new design. 4. The antelope was eaten by a leopa rd or a hyena during the night. Since S coordination 5. Since Julie covered for Sara Whitney had to come in to work today. 6. Since a citizen shouted at the mayor the governor has been more careful. Because S coordination 7. Because the scientist lied about the da ta the public did not know the truth. 8. Because the accountant mixed up the numbers the banker lost his new job.

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66 LIST OF REFERENCES Altmann. 1998. Ambiguity in Sentence Processing. TICS 2(4)146-152. Barton S.B., and Sanford A.J. 1993. A case study of anomaly detection: Shallow semantic processing and cohesion establishment. Memory and Cognition 21: 477487 Christianson, Hollingworth, Hall iwell, & Ferreira. 2001. Them atic roles assigned along the garden path linger. Cognitive Psychology 42. Clifton, Charles, Traxler, Matthew J., Mohame d, Mohamed Taha, Williams, Rihana S., Morris, Robin K., and Rayner, Keith. 2003. The use of thematic role information in parsing: Syntactic processing autonomy revisited. Journal of Memory and Language 49:317-334. Erickson T.A., and Mattson M.E. From words to meaning: a semantic illusion. Journal of verbal learning and verbal behavior 20: 540-552. Ferreira, Fernanda. 2003. The misinterpr etation of non-canonical sentences. Cognitive Psychology 47:164-203. Ferreira, Fernanda, Bailey, K., & Ferraro, V. 2002. Good-Enough Representations in Language Comprehension. Current directions in psychological science 11:11-15. Ferreira, Fernanda, & Clifton Jr., Charles. 1986. The independence of syntactic processing. Journal of Memory and Language 25:348-368. Fodor, J.D., & Inoue, A. 1998. Attach anyway. In J.D Fodor & Fernanda Ferreira (Eds.) Reanalysis in sentence processing (pp101-141). Dordrecht: Kluwer. Frazier, Lyn. 1979. On comprehending sentences: S yntactic parsing strategies, Univeristy of Connecticut: Ph.D. Thesis. Frazier et al. 1984. Pa rallel structure: a source of facilitation in comprehension. Journal of Memory and Cognition 12(5). Frazier, L., Munn, A., & Clifton, C. 2000. Processing coordina te structures. Journal of Psycholinguistic research 29(4): 343-366. Friederici, A., Pfeiffer, E., & Hahne, A. 1993. Event-related brain potentials during natural speech: processing effects of semantic, mo rphological, and syntactic violations. Cognitive Brain Research 1(1): 183-192. Garnsey, Susan M, Pearlmutter, Neal J, Myers, Elizabeth, & Lotocky, Melanie A. 1997. The Contributions of Verb Bias and Plausibil ity to the Comprehension of Temporarily Ambiguous Sentences. Journal of Memory and Language 37:58-93.

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67 Frazier, L and Clifton, C. 1981. Parsing coordinates and elli pis: copy alpha. Syntax 4(1): 1-22. Hahne, A., and Friederici, A. 1999. Electrophysio logical evidence for two steps in syntactic analysis: early automatic and late controlled. Journal of Cognitive Neuroscience 11(2), 193-204. Hoeks, J.C.J. 1997. Processing coordinate struct ures. Proceedings of the CLS opening academic year 1997, Nimegen, NL. Hoeks, J.C.J. 1999. The processing of coordination: semantic and pragmatic constraints on ambiguity resolution Doctoral Dissertation. University of Nijmegen, Nijmegen, The Netherlands. Hoeks, J.C.J., Hendriks, P., Vonk, W., Brown, C.M., & Hagoort, P. 2006. Processing the NPversus S-coordination ambiguity. Thematic information does not completely eliminate processing difficulty. Quarterly Journal of Experimental Psychology, 59(9), 1581-1599. Hoeks, J.C.J., Vonk, W., & Schriefers, H. 2002. Processing coordi nation in context: The effect of topic-structure on ambiguity resolution. Journal of Memory and Language, 46, 99-119. Kaan E & Swaab TY 2003. Electrophysio logical evidence for serial sentence Processing: a comparison between disp reffered and ungrammatical continuations Cognitive Brain Research 17(3): 621-635. MacDonald, M. C., Perlmutter, N. J., and Seidenbe rg, M. S., 1994. The lexical nature of syntactic ambiguity resolution. Psychological Review, 101, 676-703. Nelson, D. L., McEvoy, C. L., & Schreiber, T. A. 1998. The University of South Florida word association, rhyme, and word fragment norms. http://www.usf.edu/FreeAssociation/ Neville, H., Nicol, J., and Barss, A., Foster, K., and Garret, M. 1991. Syntactically based Sentence processing classes: evidence from event-related brain potentials. Journal of Cognitive Neuroscience 3, 151-165. Trueswell, J. 1996. The role of lexical fre quency in syntactic ambiguity resolution. Journal of Memory and Language, 35, 566-585. Trueswell, John C., Tannenhaus, Michael K., & Garnsey, Susan M. 1994. Semantic influence on parsing: use of thematic role information in syntactic ambiguity resolution. Journal of Memory and Language 33:285-318.

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68 Van Gompel, R., Pickering, M., Pearson, J., and G unnar, J. 2006. The activation of inappropriate anal yses in garden path sentences: eviden ce from structural priming. Journal of Memory and Language, 55, 335-362. Van Pettern, C., Weckerly, J., McIsaac, H., and Kutas, M. 1997. Working memory capacity dissociates lexica l and sentential context effects. Psychological Science, 8, 238 -243.

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69 BIOGRAPHICAL SKETCH Christopher Barkley was born on Januar y 22nd 1982 in Edinburgh, Scotland. After spending four years in Scotland, Christopher moved to Ingrave, a small village just outside of London, England. When his father was transf erred to a banking position in America, Christopher moved to Jacksonville, FL, in 1992. Chris attended elementary, middle, and high school in Jacksonville until he graduated from the Paxon School for Advanced Studies in 2000. After graduating high school, Chris enrolled at the University of Florida. He obtained his bachelors degree with a major in linguistics in 2005 and his Mast er of Arts in 2007. Chris is currently enrolled in the interdisciplinary pr ogram in Linguistics and Cognitive Science at the University of California, San Diego.


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EFFECTS OF SEMANTIC ASSOCIATION ON THE RESOLUTION OF COORDINATION
AMBIGUITIES














By

CHRISTOPHER BARKLEY


A THESIS PRESENTED TO THE GRADUATE SCHOOL
OF THE UNIVERSITY OF FLORIDA IN PARTIAL FULFILLMENT
OF THE REQUIREMENTS FOR THE DEGREE OF
MASTER OF ARTS

UNIVERSITY OF FLORIDA

2007




























O 2007 Christopher Barkley




























To all those who nurtured my academic curiosity, interests, and pursuit of knowledge throughout
my life









ACKNOWLEDGE1VENTS

I would like to thank my committee, Dr. Edith Kaan and Dr. Wind Cowles, for their

helpful advice while conducting this research. I would also like to thank my classmates and lab

colleagues for their support and suggestions on this work.












TABLE OF CONTENTS


page


LIST OF TABLES .........__... ......._. ...............7....


FIGURE ........._.__........_. ...............8.....


AB S TRAC T ......_ ................. ............_........9


CHAPTER


1 INTRODUCTION ................. ...............12.......... ......


Sentence Processing Models and Ambiguity Resolution ................ ......... ................12
Syntax-First versus Constraint-Based Models .............. ...............12....
"Good-Enough" Representations in Sentence Processing............... ...............2
Processing Coordination................. .... ..........2
Processing Coordination Ambiguities ...._.._.._ ......._._. ...._.._ ............2
Processing Coordinate Structures ................. ...............31........... ....


2 MATERIALS AND METHODS .............. ...............34....


The Present Experiment............... ...............3
Predictions .............. ...............36....

Questionnaire study .............. ...............37....
Participants .............. ...............37....
M material s ................. ...............3.. 8..............
Procedure ................. ...............39.................

Analy si s ................. ...............3.. 9..............
Results .................... ...............39.
Self-Paced Reading Study .............. ...............39....
Participants .............. ...............39....
M material s ................. ...............40.......... .....
Procedure ................. ...............41.................

Analy si s ................. ...............42.......... .....

3 RE SULT S .............. ...............43....


Comprehension Data .............. ...............43....
Accuracy ................. ...............43.......... ......
Reaction Time .............. ...............43....

Reading Time Data ................. ...............44........... ....


4 DI SCUS SSION ................. ...............47................


Comprehension Data .............. ...............47....
Reading Time Data ................. ...............50........... ....











Interaction of Parallelism and Ambiguity at the Post Disambiguating Verb
Preposition (Position 11)................ ... .. .. ... ..... ........5
Main Effect of Parallelism at the Post-Conjunction Noun (Position 9) ................... .......52
The Relationship between Comprehension and Reading Time Data ........._.._.. ........._.._....56
Syntax-First versus Constraint-Based Models............... ...............56
"Good-Enough" Representations in Sentence Processing" ................ .........................58

5 CONCLU SION................ ..............5

6 FUTURE WORK............... ...............60..


APPENDIX

A EXPERIMENTAL MATERIALS................ ...............6


B FILLER SENTENCES .............. ...............65....


LIST OF REFERENCES ................. ...............66................


BIOGRAPHICAL SKETCH .............. ...............69....










LIST OF TABLES

Table page

1-1: mean RT and accuracy per condition ................ ...............45.............

1-2: mean (SD) reading times by condition............... ...............4










FIGURE


Figure page

2-1: mean reading times at each position (by subj ects) ................ ...............46...........









Abstract of Thesis Presented to the Graduate School
of the University of Florida in Partial Fulfillment of the
Requirements for the Degree of Master of Arts

EFFECTS OF SEMANTIC ASSOCIATION ON THE
RESOLUTION OF COORDINATION AMBIGUITIES

By

Christopher Barkley

May 2007

Chair: Edith Kaan
Major: Linguistics

In constructions such as (1) the man is temporarily ambiguous: it can either serve as the

second NP of a coordinate obj ect of the first verb (NP-coordination) or the subj ect of the second

verb (S-coordination). Previous research has demonstrated that readers prefer an NP

coordination reading, and garden path at the second verb in the sentence. One account is that the

ambiguous NP is initially attached to the preceding NP to form a coordinate noun phrase forcing

readers to re-analyze when they reach the disambiguating verb, based on syntactic principles. A

recent study, examined effects of non-syntactic information on the resolution of coordination

ambiguities and demonstrated that poor thematic fit between the initial verb in the sentence and

the ambiguous noun phrase can reduce processing difficulty at the disambiguating region but not

completely eliminate it. In the present study, we investigated whether the effect of semantic

association between the relevant NPs can ease or eliminate difficulty at the disambiguating

region in these constructions. In addition, we investigated whether after disambiguation, readers

successfully re-analyze constructions such as (1).

(1) The girl screamed at the woman and the man screamed at the boy.









Thirty-six participants read seven trials each of the four conditions in (2) in a self-paced

reading study, intermixed with filler items. The experimental sentences were either ambiguous

(a, c) or unambiguous (b, d), based on the conjunction, and the two subj ect NPs were either

associated (c, d) or un-associated (a, b) as determined by an independent paper-and-pencil rating.

Care was taken to avoid plausibility confounds by using only neutral, transitive verbs and

animate, human NPs in the experimental sentences. If readers indeed take information regarding

semantic association into account while parsing ambiguous sentences, then processing difficulty

should be reduced or eliminated at the disambiguating verb in the associated NP, ambiguous

condition.

We found a main effect of association at the noun following 'and', with the nouns

unassociated with the first subject NP (2a, b) taking longer to read than associated nouns (2c, d).

The direction of the main effect at the post-conjunction NP shows that this effect cannot be

attributed to different degrees of lexical priming between local NPs. We also found an

interaction between association and ambiguity at the post-verbal preposition. Reading times were

longest for the unassociated, ambiguous condition (2a) compared to the remaining conditions,

which did not differ. This suggests that the effect of semantic association can almost completely

override processing difficulty in the disambiguating region. Accuracy data illustrate that

participants may not always re-analyze these constructions completely, as accuracy was

significantly lower to the ambiguous sentences than the non-ambiguous items. Accuracy was

also significantly higher to associated than non-associated conditions, suggesting that semantic

information may ease re-analysis. These results suggest that readers are taking semantic factors

into account online, and using this information to guide parsing decisions, but do not always

successfully reanalyze or overwrite the initial interpretation.









(2)

a. Non-associated subj ect NPs, ambiguous

The enemy talked to the queen and the king talked to the people.

b Non-associated subject NPs, non-ambiguous

The enemy talked to the queen but the king talked to the people.

c. Associated subject NPs, ambiguous

The king talked to the enemy and the queen talked to the people.

d. Associated subject NPs, non-ambiguous

The king talked to the enemy but the queen talked to the people.









CHAPTER 1
INTTRODUCTION

Sentence Processing Models and Ambiguity Resolution

Syntax-First versus Constraint-Based Models

Language comprehension takes place both rapidly and incrementally. Because a large

part of the comprehension of a sentence is based on its syntactic structure, comprehenders are

forced to make decisions of a structural nature in real time, although they are frequently faced

with syntactic indeterminacy and temporary ambiguity. Traditionally, there have been two

approaches to describing how the parser accomplishes the feat of interpretation under these less

than ideal circumstances, and these approaches have been contrasted extensively in the literature.

The first approach grants primacy to structurally based factors. According to these "syntax-first"

models, listeners/readers employ knowledge of the grammar of their language in order to build a

single structure into which incoming words are placed; without recourse to context, plausibility,

or any other non-structural source of information. Thus, during comprehension the

listener/reader adopts a single interpretation of the unfolding sentence based only on grammatical

category information and syntactic principles and only employs other sources of information in

order to evaluate the appropriateness of the structure and revise it if necessary. This view of

sentence parsing has been very influential and there are many versions of this approach (Ferreira

& Clifton, 1986; Frazier 1979), with perhaps the most influential being Lynn Frazier' s "garden

path model" (Frazier, 1979). In this model, the parser builds a first parse based on only the

grammatical categories of the incoming lexical items. When a sequence of grammatical

categories is consistent with more than one structure, the processor employs parsing principles to

distinguish between them. The principal of minimal attachment states that incoming materials

are attached into the phrase marker with the fewest syntactic nodes consistent with the well-









formedness rules of the language. If two analyses are equally simple, late closure dictates that

incoming information is attached to the constituent currently being processed; this ensures that

only one structure will be pursued. Based purely on grammatical category information and these

structural principles, the parser constructs its initial analysis of the sentence.

In opposition to these "syntax-first" models, constraint-based models (MacDonald

Perlmutter, & Seidenberg, 1994); assert that the process of building the interpretation of a

sentence involves the interaction of numerous factors in addition to syntactic considerations.

Plausibility, frequencies of occurrence and co-occurence, the relative weighting of grammatical

and probabilistic constraints, and animacy are just some of the sources of information that

contribute to the construction of an interpretation. As a sentence unfolds, all possible analyses

are computed in parallel by the parser and evaluated using multiple sources of evidence in the

input. Alternative structures are partially active with the activation level dependent on the

degree to which the input supports a given structure. The interpretation that receives the most

support from the input then "wins" out over its competitors, and the input is assigned this

structure. Processing difficulty arises when alternatives are closely matched in terms of the

support they receive from the input. Grammatical information may indeed be important to this

process and therefore may be a heavily-weighted source of evidence, but its temporal primacy is

removed and it takes no serial precedence over non-structural factors. The role of syntactic

factors is not the only crucial difference between the models, however. Syntax-first models

compute structures in serial order, and thus are often called "serial, depth-first" parsers; the first

parse is computed based on structural factors, and then revisions are computed serially based on

other relevant sources of information in the input. In contrast, constraint-based models assume

that all structures are computed in parallel, generating a type of competition which the "best"









structure wins. The contrast between these two models has motivated a great deal of research,

generating results that appear to strongly support these contrasting views. The present research

aims to add to the debate between these models by examining the effects that semantic

association has on the resolution of coordination ambiguities.

Ferreira & Clifton (1986) employed eye-tracking and a behavioral self-paced moving-

window technique to show that readers experienced difficulty when what was initially

understood as a subj ect plus main verb was disambiguated towards the dispreferred (non-

minimal attachment), less frequent reduced relative clause structure (la, 2a below) This

structure, depending on verbs that are morphologically ambiguous between past participle and

past tense forms, is known as the reduced relative ambiguity and has been studied extensively.

Ferreira and Clifton demonstrated that this processing disruption, the "garden path" effect, was

experienced even when the subj ect plus main verb analysis was highly unlikely because of an

inanimate subj ect in sentence-initial position, as in 2a). Thus, Ferreira and Clifton saw increased

reading times at the disambiguating region in both la and 2a (when compared to unambiguous

counterparts in b):

la) The defendant examined by the lawyer turned out to be unreliable.

lb) The defendant that was examined by the lawyer turned out to be unreliable.

2a) The evidence examined by the lawyer turned out to be unreliable.

2b) The evidence that was examined by the lawyer turned out to be unreliable.

As readers begin to construct their parse of sentences like 1) and 2) above, it is assumed

that they initially adopt a main-clause analysis and assign the role of subj ect and agent to the

defendantdd~~~~~ddddd~~~~ in 1) and the evidence in 2) (Based on the principle of minimal attachment under a

syntax-first model (Frazier, 1979); or based on the higher frequency of this structure under a









constraint-based approach (MacDonald et al. 1994). However, when readers reach the by-phrase

followed by the main verb, the parse under construction becomes inconsistent with the input and

the structure must be revised. This is the cause of the increase in reading time when compared to

the sentences in b) which are unambiguous between main verb and reduced-relative

interpretations because of the appearance of that which unambiguously signals a relative clause.

Crucially, if readers take animacy or plausibility into account to guide parsing decisions, then

the difficulty should be overridden or at least reduced in 2a) when compared to la). The fact that

Ferreira and Clifton observed similar patterns of disruption in la) and 2a) led them to argue for

an informati onally-encap sulated syntax module. They argue that thi s module operates on purely

syntactic principles and is insensitive to other sources of information, such as animacy. Thus,

their results support a syntax-first parser and are inconsistent with a constraint-based process in

which multiple structures are computed in parallel based on the contributions of all possible

sources of information.

Trueswell, Tanenhaus, and Garnsey (1994) influentially challenged the results of Ferreira

and Clifton (1986) by asserting that the implausible (inanimate) subj ects were selected for their

materials without extensive pre-testing. Trueswell et al. argued that many of the implausible

subjects were actually compatible with the main verb interpretation (such as the car towed....),

thus making the results of Ferreira and Clifton hard to interpret and rendering the data

inconclusive. Using paper-and-pencil completion norms, Trueswell et al. had participants rate

how typical animate and inanimate nouns were as agents and themes. Based on the results of

this study, Trueswell et al. constructed the same paradigm employed by Ferreira and Clifton

(1986), except with more highly controlled nouns in sentence-initial subj ect position, and then

employed the same experimental techniques in order to determine if Ferreira and Clifton's









results were replicable. This ensured that all animate subjects were good agents, and all

inanimate subj ects were poor agents and good themes. Trueswell et al. (1994) reported that, with

their modified materials, the difficulty observed at the disambiguating by-phrase of reduced

relative constructions with inanimate subjects disappeared. The authors state that their results

are most consistent with a evidential constraint-based model of sentence parsing in which

grammatical information takes no precedence over non-structural factors, and multiple sources of

information interact during structure-building operations.

Clifton, Traxler, Mohamed, Williams, Morris, & Rayner (2003) extended the research of

Ferreira & Clifton (1986) by employing an eye-tracking methodology to examine the resolution

of reduced-relative ambiguities. They again crossed ambiguity with the animacy of the subject

to form sentence quadruplets like 3) below:

3a) The man paid by the parents was unreasonable.

3b) The man who was paid by the parents was unreasonable.

3c) The ransom paid by the parents was unreasonable.

3d) The ransom that was paid by the parents was unreasonable.

Clifton et al. also manipulated parafoveal preview of the disambiguating by-phrase so

that each condition above was seen by some participants with the disambiguating by-phrase

visible in their parafovea and by others with the disambiguating by-phrase masked. This

manipulation was introduced in response to some criticisms of Ferreira and Clifton (1986);

namely that the grammatical information expressed by the by-phrase may have been used to

guide parsing decisions. By introducing this manipulation into their experimental design as a

factor, they were able to determine any possible effect of the participant seeing the by-phrase

while processing the ambiguous verb. Clifton et al. found evidence of disruption (in terms of









first-pass time, regression frequency and regression duration) at the disambiguating region (again

the by-phrase) in the reduced relative constructions, regardless of animacy or preview. Late

measures of processing seemed to indicate that animacy made the ambiguity especially hard to

overcome, with the reduced relative structures with animate subj ects proving hardest to revise.

These data support the notion that animacy cannot guide parsing decisions, but that it can serve

to ease re-analysis after misinterpretation. While these results initially seem to argue for a

syntax-first parser, Clifton et al. eloquently argue that this is a hasty conclusion. Clifton et al.

state that while the data do cast doubt on the notion that semantic and pragmatic factors can

override syntactic considerations, that this can not be straightforwardly concluded. They contend

that syntactic preferences may be overridden in some domains and not others, and that a

constraint-based theory could also explain their data by simply ranking constraints such that

structural simplicity outweighs semantic plausibility. These arguments actually extend to most

research designed to probe this theoretical distinction; with proponents of each model attributing

effects to different stages of the parsing process. For example, if it appears that animacy can

guide parsing decisions (e.g Trueswell, Tanenhaus, and Garnsey, 1994); then syntax-first

proponents can simply attribute these effects to "rapid re-analysis guided by semantic

principles." For this reason, it is notoriously difficult to interpret data gathered by experiments

designed to test syntax-first versus constraint-based models. The issues raised by Clifton et al.

should be considered when critically evaluating any research in this domain.

One issue that arises when critically evaluating these studies is the use of animacy as a

semantic factor. Trueswell (1994), Clifton et al. (2003), and Ferreira & Clifton (1986) all

employed animacy to argue either for or against semantic effects on parsing decisions. Animacy

is not the ideal factor for this purpose, as it is somewhat controversial as to whether it is a










completely "non-structural" factor. When considering what sort of information could influence a

restricted domain, or syntax-first parser, there was considerable debate about whether to include

thematic information such as animacy. Animacy is morphologically marked in some languages

with clear morpho-syntactic consequences, and in some languages, such as Japanese, structural

decisions on subject-hood are based on animacy information. It is also incorporated into a verb's

argument structure under some accounts, granting animacy structural consequences. The

semantic manipulation in the present experiment was designed to avoid this issue.

Trueswell (1996) examined the effect of frequency on the resolution of ambiguous

reduced relative clauses. The specific type of frequency that he was interested in was the

frequency with which a verb that is morphologically ambiguous between past tense and past

participle appears in each of these forms. Crucially, constraint-based models predict that

difficulty in assigning a reduced relative clause interpretation to a structure should be modulated

by the frequency with which a morphologically ambiguous verb form is employed in this

construction. Trueswell conducted two self-paced reading experiments in which readers read

relative clause ambiguities which were manipulated along three dimensions: whether the

sentence contained a reduced or unreduced relative clause, whether the subj ect was animate or

inanimate, and whether the main verb had a high or low frequency as a past participle. Results

of these experiments supported the notion that readers are subj ect to frequency effects when

building the first-parse of a sentence. Trueswell found that when the relative clause

interpretation received support from semantics (in the form of an inanimate subj ect), this

information served to override processing difficulty for verbs with high participle frequencies but

not those with low participle frequencies. When semantics provided support for the main clause

interpretation (in the form of an animate subj ect), there was evidence of processing difficulty for









both verbs, though ambiguity resolution appeared to be faster in the high participle frequency

group. Trueswell states that these results support a constraint-based model of sentence parsing,

in which verb-form frequency interacts with other structural and non-structural sources of

information during parsing. Trueswell argues that, based on this data, processing models should

take statistical frequency into account in addition to other non-structural factors.

Garnsey, Pearlmutter, Myers, & Lotocky (1997) examined the effects of verb bias and

plausibility on the resolution of sentences containing temporary ambiguities. Garnsey et al.

manipulated the plausibility that the post verbal NP would be interpreted as a direct obj ect of the

verb, the bias towards the transitive reading induced by the verb, and the presence or absence of

ambiguity. These manipulations resulted in the paradigm seen in 5):

Direct-obj ect (DO) biasing verbs:

Sa) The talented photographer accepted (that) the money could not be spent.

5b) The talented photographer accepted (that) the fire could not have been prevented.

Subordinate clause biasing verbs

Sc) The ticket agent admitted (that) the mistake had been careless and stupid.

5d) The ticket agent admitted (that) the airplane had been late in taking off.

Non-biasing verbs

Se) The sales clerk acknowledged (that) the error should have been detected earlier.

5f) The sales clerk acknowledged (that) the shirt should have been marked down.

Garnsey et al. found that verb bias has a rapid effect on ambiguity resolution, with

readers experiencing the most difficulty at the disambiguating region in sentences with DO

biasing verbs. Garnsey et al. also found an effect of plausibility, with implausible objects

reducing difficulty at the point of disambiguation, and this effect interacted with verb bias during










comprehension. The authors interpreted their results as best fitting into a constraint-based model

of sentence parsing, which takes into account non-structural factors (plausibility) and factors

generated by comprehender' s experience with transitivity/subordinate clause frequencies of

specific verbs.

"Good-Enough" Representations in Sentence Processing

To this point, I have focused my description of sentence processing models on the factors

that may or may not interact to guide parsing decisions during comprehension. Verb bias,

plausibility, animacy, and frequency are among the sources of information that may possibly

influence structure building operations; and there is evidence pointing either to effects generated

by these factors or a lack thereof. A great deal more research is required to resolve this debate.

There is another debate, orthogonal to the debate between syntax-first and constraint-based

models, and it concerns the representational nature of the output of the parsing processes. An

implicit assumption of both syntax-first and constraint based models is that the end result of

parsing (with or without re-analysis) is a syntactic frame that is fully compatible with the input.

Regardless of whether the relative activation of this frame can be influenced by non-syntactic

information as the parser moves through the sentence, the interpretation of a sentence must be

based on a syntactic frame. The parser is traditionally viewed as a compositional algorithmic

processor that continues processing until the correct structure is built. The meaning of a sentence

is derived from the composition of the meaning of its parts; and the parser analyzes to the extent

that it can reach this interpretation. Recent research has begun to challenge this assumption by

illustrating that the end result of comprehension is often an incomplete or inaccurate

representation. One source of data that supports this view is the M~oses illusion (Erickson &

Mattson, 1981). When asked, "How many animals of each type did Moses bring on the ark?"

people often respond "two," without noticing the glaring error. While this evidence is frequently










employed to demonstrate the fallibility of memory, the degree to which listeners do not fully

process the input is striking. Barton and Sanford (1993) documented a similar effect, noticing

that people rarely notice the problem with the question, "Where did the authorities bury the

survivors?" While these sources of information are somewhat anecdotal, they do lend support to

the view that language processing is sometimes "shallow" and that compositionality does not

always hold. I will now summarize some research that lends support to this shallow, heuristic

processing.

Ferreira (1996) used simple, unambiguous sentences to investigate the issues raised

above. Ferreira examined this issue with the paradigm in 6), which manipulates bias,

plausibility, and grammatical voice. The sentence was either presented in active or passive

voice, and the arguments could be presented in one of two orders. In the reversible conditions,

reversing the order of the arguments led to a possible but implausible arrangement (as can be

seen in 6b). In the non-reversible condition, reversing the order of the arguments led to a

semantically anomalous arrangement, and in the symmetrical condition rearranging the

arguments had no effect on plausibility. The full paradigm can be seen in 6):

Active Passive

6a) biased, reversible, plausible

The dog bit the man. The dog was bitten by the man.

6b) biased, reversible, implausible

The man bit the dog The man was bitten by the dog.

6c) nonreversible, plausible

The mouse ate the cheese. The cheese was eaten by the mouse

6d) nonreversible, implausible










The cheese ate the mouse. The mouse was eaten by the cheese.

6e) symmetrical, one order

The woman visited the man. The man was visited by the woman.

6f) symmetrical, other order

The man visited the woman. The woman was visited by the man.

Sentences were presented to the participants aurally, and the participants were then

probed with comprehension questions that forced them to identify the thematic roles in the

sentence (i.e., DO-ER?). The results show that there is a cost for the passive, so that for all

sentence types, the participants made more errors on the questions probing the passive voice than

they did on the questions probing the active voice, and also responded to these sentences more

slowly. It appears that, even in relatively simple, unambiguous sentences, comprehenders

frequently misassign thematic roles leading to inaccurate representations. The authors conducted

a second experiment to ensure that it was not surface frequency of the construction generating

this effect, passive being less frequent than active, by comparing simple active sentences and

subject-cleft constructions. This was indeed not the case as subjects performed equally well to

questions probing actives and subj ect clefts, even though the subj ect-cleft construction is

extremely infrequent in English. A third experiment demonstrated a parallel between obj ect and

subj ect clefts and actives and passives, with participants performing poorly on questions probing

the obj ect clefts. The parallel between the obj ect-cleft construction and the passive is instructive.

Both of these constructions force comprehenders to assign thematic roles in an atypical order.

The fact that this atypical order of assignment is so problematic for readers points to a processor

that employs heuristic strategies (one such strategy, the NVN strategy, listeners readers to

identify the pre-verbal noun as a proto-agent and the post-verbal noun as the proto-patient)









caused rather than detailed algorithms; strategies which are prone to breakdown in atypical or

infrequent situations. Ferreira interprets these results as evidence of a heuristic processor, she

states that comprehenders often rely on shallow processing that is simply "good enough," rather

than always relying on complex syntactic algorithms. In some cases, as in the experiment, non-

canonical or atypical structures cause the parser to assign thematic roles to the wrong syntactic

constituents. The result is an underspecified, incomplete representation that may never be

completely revised. Crucially, Ferreira argues that these results are inconsistent with any

processing model (Frazier, 1979; MacDonald et al. 1994) that assumes that the parser only

computes structures that are consistent with the syntactic information encoded in the input.

Whether non-structural information can influence the computation of the structure or not, both

types of model argue that the structure must be built based on a syntactic frame. Ferreira argues

against this position convincingly.

Christianson, Hollingworth, Halliwell, and Ferriera (2001) examined incomplete or

inaccurate representations by examining whether readers ever fully delete their initial incorrect

interpretation of a sentence after re-analysis. In order to examine this issue they employed

transitivity ambiguities (with no commas to enhance the effect) as seen in (7). The reader will

initially interpret the baby as the object of dressed. However, when they encounter the verb spit,

they will encounter difficulty as the parse under construction is inconsistent with the input. They

will then have to revise their interpretation; and the authors were interested in the fate of the

initial analysis.

7) While Anna dressed the baby spit up.

Previous research has assumed that, after mis-analysis, readers fully repair the

representation to the extent that the parse becomes fully consistent with the input string. After









reading sentences such as 7), subjects were probed with questions such as DidAnna dress the

baby? and, Did the baby spit up? Questions such as these can only be answered correctly if,

after mis-analysis, the parser detaches the baby from the slot designating it as the obj ect of the

verb and re-attaches it to subject position of the second verb. Christianson et al. found that

subjects were almost 100% accurate in stating that the baby spit up. However, a surprising

number of errors were found in which subj ects took the baby to be the obj ect of dressed. This is

evidence that their Einal representation is not consistent with the input. This could be caused by a

failure to re-analyze and assign thematic roles to the correct constituents, or by interference

between the unsurpressed initial incorrect interpretation and the correct one. It also may provide

evidence that a comprehender' s Einal representation isn't always consistent with linguistic well-

formedness conditions, as some participants interpreted the baby as both the subj ect of spit up

and the obj ect of dressed, an interpretation that violates structural principles such as the theta-

criterion. Though as stated above, it could also be the case that the accuracy pattern described

may be caused by the incorrect analysis persisting in memory to the extent that it can compete

with the subsequent analysis and influence comprehension. In the second experiment, the

researchers compared garden-path sentences such as 7) with unambiguous controls. The results

suggest that readers often do not completely re-analyze a construction, or that if they do, the

incorrect analysis persists to the extent that it can influence comprehension. These results nicely

tie language comprehension to other areas of cognitive science, such as vision, where recent

Endings have shown that the visual system does not construct a true global image of a visual

scene leading to change blindness, which refers to the observation that many participants are

insensitive to changes in a visual scene as they are viewing it. These data suggest that the visual

system may also rely on representations that are not always fully detailed. It may be the case that









the heuristic strategies discussed by Ferreira (1996) and Christianson et al. (2001) are

advantageous to an organism who must interact with its environment rapidly, in which case these

types of strategies would be employed in all domains of cognition and decision making. Further

evidence for the persistence of the initial mis-analysis and its effects on comprehension comes

from a study by Van Gompel, Pickering, Pearson, & Jacob (2006). They had participants read

sentences including verbs that were ambiguous between transitive and intransitive structures; in

one condition the transitivity of the verb was disambiguated with a comma but it in the other

condition no disambiguating information was present leading subjects to initially interpret an

intransitive verb as transitive. This led participants to garden path and temporarily activate a

transitive reading of the verb in the condition with no comma. After having read the sentence,

participants were prompted to complete a sentence fragment out loud. Participants were more

likely to produce transitive completions after the ambiguous condition in which they had initially

misinterpreted the verb as transitive, indicating that the initial misinterpretation persisted to the

extent that it could influence production. The authors were unable to distinguish between the

different accounts that provide an explanation for this effect (persistence of a memory trace, lack

of re-analysis, or application of a heuristic).

In sum, Ferreira (1996), Christianson et al. (2001), and Van Gompel et al. (2006)

demonstrate that the parser often constructs incomplete representations that are not the result of

exhaustive analysis. Whether it is the result of applying a heuristic to the processing of simple

sentences, failing to completely re-analyze the input, or not suppressing the initial interpretation;

evidently the parser is often satisfied with constructing representations that are only "good

enough."









The research that I have presented lays out the issues surrounding the debate between

syntax-first and constraint based processing models, and between algorithmic and heuristic

processors. As we have seen, these debates center on what types of information (syntactic and

non-syntactic) can influence initial parsing decisions and whether the end result of this parse is a

linguistic representation that is fully specified at all levels.

Processing Coordination

The purpose of the current study is to collect data that help to resolve these issues

utilizing coordination ambiguities and a manipulation that varies which previous noun phrase in

a sentence an ambiguous noun phrase is semantically associated with. A coordination ambiguity

is a sentence like (8) below; in which the NP the man is ambiguous between being the second NP

in a coordinate obj ect of the main verb of the first clause and the subj ect of the main verb of the

second clause. The sentence is disambiguated at the verb talked, when it becomes clear that the

man is in fact the subject of a second clause.

8) The woman talked to the boy and the man2 talked to the girl.

Previous research on this construction has demonstrated the so called "NP coordination

preference" (Frazier, 1979; Kaan & Swaab, 2003; Hoeks, 2006). This causes readers to initially

interpret the ambiguous NP as part of a coordinate obj ect of the first verb, and therefore initially

adopt the wrong analysis of the sentence. This triggers processing difficulty and re-analysis at

the second verb, when the parser realizes that the input has been misanalyzed.

For instance, Kaan and Swaab (2003) provided evidence for the NP coordination preference

using an ERP technique. Part of their experimental manipulation compared coordinated

sentences with ungrammatical continuations versus continuations that were "dispreferred."

Importantly, the dispreferred condition is only dispreferred if participants initially adopt an

analysis where the house and the garage form a coordinated NP. For example:









Ungrammatical

9) The man was painting the house and the garage were already finished.

Di preferred

10) The man was painting the house and the garage is already finished.

Kaan and Swaab (2003) found that both dispreferred and ungrammatical continuations

elicited a LAN effect at the verb after the ambiguous NP, this ERP component indexes early

syntactic processing difficulty that may reflect local phrase structure violations induced by what

the parser perceives as word category errors (Friederici, Pfeiffer, and Hahne 1993; Neville,

Nicol, and Barss 1991, Hahne and Friederici 1999). Crucially, for the purposes of this paper,

these data suggest that the parser initially attached the ambiguous NP to the preceding NP to

form a complex obj ect. When it reaches the disambiguating verb, the parser experiences

difficulty and initially interprets the string as ungrammatical because the verb cannot be

incorporated into the phrase structure currently under construction. While these data do reveal

that the parser is prone to attaching the ambiguous NP to form an NP coordination, they have

nothing to say about what underlies this effect. I will quickly summarize two approaches to

explain this parsing preference: syntactic principles and frequency based accounts.

Following the syntactic principle of minimal attachment, Frazier (1979) predicts that

readers will initially attach the ambiguous noun phrase to a second obj ect slot of the first verb,

creating a coordinate noun phrase reading. This occurs because to create a full S-coordination

requires the creation of one extra S node to head the new clause, thus violating minimal

attachment ("create the fewest nodes possible") and causing the parser to choose the NP-

coordination analysis. After the reader adopts this structure, they will garden path at the second









verb and have to re-analyze their initial mis-interpretation, presumably with measurable

processing cost resulting. This is a syntax-based account of the NP coordination preference.

Hoeks (2006) adopted a frequency based approach in attempt to explain this preference.

He conducted a corpus study examining the prevalence of S- and NP-coordinations in the Dutch

newspaper TROUW. In a set of 1000 occurrences, NP coordination was by far the most

prevalent, making up 46% of the instances using the Dutch connective en (equivalent to and). S-

coordination only made up 10% of these instances. So, perhaps it is not necessarily a syntactic

principle that underlies the NP coordination preference, but rather just frequency of occurrence

which causes readers to adopt the most likely structure based on frequency.

While the underlying mechanism of the NP coordination preference may be unclear, it is

a robust finding in sentence processing experiments. Whether motivated by frequency or

syntactic principles, this preference causes readers to incorrectly assign an NP coordination

reading to S-coordination structures and garden path at the disambiguating verb. The purpose of

the current research is to attempt to modulate this attachment preference in coordination

ambiguities with semantic factors. By varying whether the ambiguous noun phrase is

semantically associated with the subj ect or the obj ect of the first verb, the present study aims to

determine whether this preference can be overridden and processing difficulty reduced. If this is

the case, processing disruption would be reduced at the disambiguating verb in sentences like

(8).

Before summarizing the present study, it is first necessary to discuss the previous

research that has been examined factors that can influence the resolution of coordination

ambiguities as well as the factors that influence the processing of the second conjunct of a

coordinate phrase.









Processing Coordination Ambiguities

Hoeks (1997, 1999, 2002) has conducted a series of experiments examining factors that

have an effect on the online resolution of coordination ambiguities. Before examining these

factors, Hoeks (1997) employed eye-tracking and ERP methodologies to examine the NP-

conjunction preference predicted by minimal attachment (Frazier, 1979). The data from these

parallel experiments suggest that readers do indeed demonstrate this processing preference, as

ERP and eye-tracking indices of parsing disruption were evident at and immediately following

the disambiguating region of the coordination ambiguity. Next, Hoeks examined whether a

semantic manipulation could eliminate processing difficulty by overriding the NP-conjunction

preference. He chose to investigate this issue by manipulating the thematic fit between the verb

and the ambiguous noun phrase, leading to the experimental manipulation seen in 9):

9a) The boatman repaired the mainsail and the skipper painted the mast of the boat.

9b) The sheriff saw the Indian and the cowboy noticed the horse in the bushes.

If the parser computes thematic fit online and uses this information to guide parsing

decisions, then the processing difficulty encountered at the underlined region of 9b) should be

reduced at the underlined region of 9a). In 9a), the NP the skipper is not a good argument of the

verb repair because it is animate, and Hoeks (1997) was interested in whether this type of

information was taken into account when parsing these constructions. He found that all effects

of processing difficulty in the disambiguating region disappeared as a result of this manipulation,

and used these data to argue against syntax-first models. While he acknowledges the argument

that re-analysis may have proceeded very quickly in these cases, indicating that the ambiguous

construction was still mis-analyzed; he argued that if this were the case, then the ERPs would

have shown signs of residual processing difficulty, which they did not (however see Hoeks

(2006), in which he argues that signs of residual difficulty are in fact present). One issue that is










evident in regards to these experimental materials is that perhaps the conjunction of animate and

inanimate NPs is so unnatural that the readers did not consider the NP-conjunction analysis.

This argument is backed up by an examination of language corpora which demonstrate that that

coordination of this type very rarely occurs in natural language (Hoeks, 2006).

Hoeks (2002) examined the effect that discourse structure in the preceding context has

on the resolution of coordination ambiguities. He argued that the NP conjunction preference

demonstrated by himself and other researchers is motivated by the fact that this interpretation is

simpler in terms of discourse structure. Hoeks first conducted a completion study which

illustrated the NP-coordination preference. He found that when completing fragments such as

The photographer spoke 0I ithr the model and the actress...., only 15% of completions represented

S-coordination. However, when the prior context introduced two subjects (see 10a), the number

of S-coordination completions rose to 80%. He then examined these issues with eye-tracking

and self-paced reading techniques. He had participants read ambiguous S-coordination

sentences, that were either preceded by neutral contexts or contexts that introduced two NPs in

coordinate subject position into the discourse. The paradigm is seen in 10)

10a), biasing context:

When they met the designer at the party afterward, the model and the photographer were very

excited.

10a'), neutral context:

It was not surprising that the party after the fashion show was exhilarating.

10b), target sentence:

The model embraced the designer and the photographer laughed.









Hoeks found that readers encountered difficulty at the disambiguating region of the

coordination ambiguities when they were preceded by neutral contexts. When the ambiguous

target sentence was preceded by a sentence introducing two subj ects, all traces of processing

difficulty disappeared. He used this data to argue for the immediate effect of context on the

resolution of coordination ambiguities and against models of sentence processing that give

precedence to structural sources of information.

Hoeks (1997, 1999, 2002) documented that thematic fit and discourse structure have

effects on the resolution of coordination ambiguities, and it is essentially his work that will be

extended in this paper. Let us first examine this issue from a slightly different perspective. Lyn

Frazier and colleagues have conducted a series of experiments examining what factors can

influence the processing of the second conjunct in a coordinate phrase, and I will now summarize

this work.

Processing Coordinate Structures

In earlier work, Frazier et al. (1984) conducted a series of self-paced reading experiments

examining the coordination of sentences. Frazier et al. were interested in whether they could

find an effect of structural parallelism (two constituents are said to be structurally parallel when

they share the same internal structure) when processing coordinated phrases. They investigated

this in many syntactic environments, such as active/passive, minimal/non-minimal attachment,

shifted/non-shifted heavy NPs, agent/theme, and animate vs. inanimate NPs. Across all

environments, Frazier et al. found an effect of parallelism. Therefore an active construction was

read more quickly when it was preceded by an active than when it was preceded by a passive, a

non-minimally attached structure was read more quickly when it was preceded by another non-

minimally attached structure than when it was preceded by a minimally attached structure, etc.

Frazier et al. used these data to argue that coordination constitutes a special syntactic case, but









does not and cannot conclude what the cause of the parallelism effect is. Nonetheless, this

research demonstrates that parallelism is a factor that can affect the processing of coordinate

structures.

Frazier, Munn, and Clifton (2000) conducted as series of four experiments examining the

processing of coordinate structures. They utilized an eye-tracking methodology to investigate

factors that influenced the processing of these structures. They found that coordination of unlike

categories was just as acceptable as processing two conjuncts of the same category. They used

this data to argue against a grammatical constraint that only constituents of the same category

can be conj oined. They did, however, find processing facilitation (in terms of reading time) at

the second of two conjuncts when it was either parallel in terms of category or internal structure.

For example the underlined portion of (9) was read faster than the underlined portion of (10), due

the fact that it is preceded by a conjunct with the same internal structure.

9) Bill talked to the tall man and the short woman.

10) Bill talked to the man and the short woman.

Additionally, Frazier et al. (2000) found a similar effect of syntactic category, leading to

a reduction in reading time for a constituent that was preceded by a constituent of the same

category. This effect would lead to the underlined portion of 11) being read faster than the

underlined portion of 12):

11) John walked with great speed and with great care.

12) John walked slowly and with great care.

However, the same facilitation was not found between two noun phrases that served as

the subj ect and obj ect of a verb. The authors use these data to argue that coordination enj oys

some sort of special status, as effects were not seen when using the same NPs in different









constructions. The authors successfully demonstrate that internal structure of the conjuncts is

one factor that influences the processing of coordinate structures, and hint at the fact that

coordinate structures may be influenced by factors that do not necessarily influence other

structures. This echoes Clifton' s (2003) argument that factors may have an influence on parsing

decisions in some domains, but not others.

While Frazier's primary interest is in the processing facilitation induced by structural

parallelism in coordination structures, and the current experimental paradigm will manipulate

whether an ambiguous noun phrase is semantically associated with the subj ect or object of the

main verb, her work still provides crucial background to the present study. The present study

aims to elucidate the factors that can influence the interpretation of the ambiguous NP in

coordination ambiguities. Research into these factors can be conceptualized in two ways. First,

it is a continuation of Hoeks' work that has already documented the effect that discourse

structure and thematic information can have on the attachment of this noun phrase. Secondly,

the present experiment has much in common with the work of Frazier and colleagues. Crucially,

the ambiguous noun phrase is a second conjunct and its interpretation can be influenced by

characteristics of the first conjunct as documented by Frazier. If semantic parallelism has a

similar effect to structural parallelism between conjuncts, then the attachment of the second

conjunct should be influenced by which other NP in the sentence it is semantically parallel with.

So, the attachment of this ambiguous NP can be influenced in two ways: by factors that affect

ambiguity resolution and by virtue of its semantic parallelism with a preceding conjunct. While

these two accounts are difficult to tease apart, I will keep both in mind while analyzing the data

resulting from the present experiment.









CHAPTER 2
MATERIALS AND IVETHODS

The Present Experiment

The present experiment aims to add to the two debates central to the sentence processing

literature as well as extending the results of Hoeks (1997, 1999,2002), and determining whether

lexical/semantic parallelism has an effect on the resolution of coordination ambiguities. While

Hoeks's results are intriguing, there are issues with his experimental design that I intend to

remedy. First, as he himself acknowledges, the data that he uses to argue that semantic

information can override structural preferences in coordination ambiguities are flawed. He

employs materials that have an animate NP and an inanimate NP surrounding the conjunction

and. Based on corpus studies, coordinate phrases of this type are extremely rare. Therefore, his

data may only indicate that structural preferences were overridden by frequency or plausibility

factors. While this is interesting in and of itself, it does not constitute evidence that structural

preferences have been overridden by semantic factors. Secondly, animacy itself is not purely

semantic. As I discussed earlier, in some languages animacy has morpho-syntactic consequences

and the possibility that it can have similar influences in English cannot be excluded. I aim to

remedy these issues with the paradigm seen in (11) which manipulates whether the ambiguous

noun-phrase is semantically associated with the subj ect of the first clause or the obj ect of the first

verb:










Non-parallel, ambiguous
11a) The enemy talked to the king and the queen talked to the people.
Q: Did the enemy talk to the queen?
Non-parallel, non-ambiguous
11Ib) The enemy talked to the king but the queen talked to the people.
Q: Did the enemy talk to the queen?
Parallel, ambiguous
11c) The king talked to the enemy and the queen talked to the people.
Q: Did the king talk to the queen?
Parallel, non-ambiguous
11d) The king talked to the enemy but the queen talked to the people.
Q: Did the king talk to the queen?

This paradigm will allow me to examine the same issues that are central to the work of

Hoeks, but has the following advantages: 1. All NPs are human and animate. This allows the

reader to create equally natural conjunctions of both noun phrases and sentences. 2. The verbs

are neutrally biasing. In combination with the selection of nouns, this leads to elimination of

plausibility confounds and eliminates differences in selectional restrictions or thematic fit

between nouns and verbs across conditions. The manipulation is unequivocally semantic in

nature, in contrast to Hoeks (1997). He manipulated the animacy of the ambiguous noun phrase,

while the paradigm in 11) manipulates which previous noun-phrase the ambiguous noun-phrase

is associated with. If indeed, information on semantics/lexical association is taken into account

to guide parsing decisions, then difficulty in the disambiguating region should be reduced when

the ambiguous NP is semantically associated with the subject of the first clause. If this reduction

in difficulty is observed, it would constitute compelling evidence against serial, depth-first

models of parsing as in no way does the above manipulation have syntactic or structural

ramifications. I also aim to extend the work of Ferreira (1996) and Christianson (2001), by

examining the representational nature of the result of the parsing process. The process of

resolving coordination ambiguities is similar to the process of resolving the transitivity

ambiguities in Christianson et al. (2001). I will examine accuracy data in an attempt to









determine whether full re-analysis is undertaken, if the end result of parsing is a fully-detailed

representation, if the semantic manipulation can have an effect on accuracy, and if the end result

of parsing is fully specified and consistent with linguistic well-formedness conditions.

Predictions

The paradigm in 11) above crosses ambiguity (but versus and) with the semantic

manipulation that varies which prior noun phrase the post conjunction noun is associated with.

In the parallel conditions, the ambiguous noun phrase is highly associated with the subj ect of the

main verb, while in the non-parallel conditions the ambiguous noun phrase is associated with the

obj ect of the main verb. If the preference for NP coordination is replicated in this study, then

reading times will be elevated at the second verb in the ambiguous conditions when compared to

the non-ambiguous conditions. This increase in reading time reflects the fact that the non-

ambiguous conditions do not license the NP coordination reading which is licensed in, and

causes difficulty in, the ambiguous conditions. If there is no such preference, we will not see

differences between ambiguous and non-ambiguous conditions. If semantic information is taken

into account and helps guide parsing decisions then reading time at the second verb (and

downstream) in the parallel, ambiguous condition should be reduced when compared to the non-

parallel, ambiguous condition. This reduction may manifest itself as a main effect of parallelism

or an interaction between parallelism and ambiguity at the point of disambiguation and

subsequent positions. However, if this information is ignored during initial parsing decisions

then reading time will be comparable at this position. The reading time data gathered in the

ambiguous region and post-ambiguity will determine whether information on semantic

association is reducing processing difficulty in these constructions. If semantic information is

strong enough to trigger S-coordination; we would expect an increase in reading time for non-

parallel conditions when compared to parallel conditions. Accuracy data will also be collected










comparing ambiguous and non-ambiguous conditions on questions that probe the grammatical

role of the ambiguous noun phrase. For example, the sentence "The king talked to the enemy

and the queen talked to the people," would be probed with the question "Did the king talk to the

queen?" If participants fully recover from the ambiguity and accurately re-assign theta roles or

successfully suppress the misinterpretation, then there will be no difference between these

conditions. However, if participants do not fully recover from a misinterpretation of the

ambiguity, we will observe significantly lower accuracy to the ambiguous than non-ambiguous

constructions. These data will help determine whether participants undertake full re-analysis

when recovering from a coordination ambiguity.

Questionnaire study

In order to generate the experimental paradigm described above with adequate control, it

was first necessary to create noun sets that contained two associates and one non-associate. For

this purpose, a questionnaire study which was designed to collect association ratings on pairs of

nouns was conducted.

Participants

Fifty participants from the University of Florida population participated in the

experiment. Data from ten participants were excluded due to their responses on an

accompanying language questionnaire that showed that they were not monolingual native

speakers of English. Participants gave informed consent according to University of Florida IRB

procedures, and were not compensated for their participation.









Materials

For the purpose of selecting the nouns for the self-paced reading study, forty-two noun pairs

were chosen based on data from the University of South Florida association database

(http://w3.uusf edu/FreeAssociation/). Nouns were selected based on the following criteria: The

noun refers to a descriptive or occupational role that a human could fill, the noun is an animate

count noun, the noun has a noun with the above characteristics on its list of associates, and the

cue-to-target association strength between the two nouns is at least .20 as listed in the association

database. A cue-to-target strength of .20 indicates that when prompted with the cue, 20% of

participants responded with the target. The original forty-two nouns and their associates thus

made up forty-two pairs of associated nouns. Based on intuition, a third, unassociated, noun was

added to each pair yielding triplets. Crucially, this noun could not appear on the list of associates

of either of the other two nouns. By splitting the triplets into their constituent pairs (ABC &

AB, CB, e.g, king-queen; enemy-queen), eighty-four pairs of nouns were created; forty-two that

were associated and forty-two that were unassociated. These eighty-four noun pairs were

randomly intermixed with eighty-four filler pairs, yielding 168 pairs of nouns in total. These

distractors were designed to mask the experimental manipulation as well as to encourage the

participant to utilize the entire rating scale. For example, the participant could be asked to rate

the association between "donkey and gymnast," or "coal and tree." The noun pairs were pseudo-

randomized so that no experimental pairs followed each other, and the pages of the questionnaire

were presented randomly to eliminate the effect of presentation order on the participants' ratings.









Procedure

The participants' task was to provide a rating of how "associated" the two nouns were by

circling a number between 1 ("completely unassociated") and 7 ("completely associated").

Participants were given instructions to answer based on their initial intuitions, and given

examples in order to familiarize them with the rating scale. The participants were also

encouraged to employ all parts of the rating scale. The questionnaire study lasted 15 minutes.

Analysis

We first calculated mean ratings for all eighty-four experimental pairs (42 associated

pairs and 42 unassociated pairs). Then t-tests were conducted examining the difference between

mean ratings of associated and unassociated pairs across items and comparing the associated and

unassociated pairs by item.

Results

The results of the t-test comparing the associated and unassociated conditions revealed

that overall there was a significant difference between the ratings [t(1,41)=20.3, p < .001). The

results of the individual t-tests between the constituent pairs of each triplet yielded twenty-eight

triplets whose rating difference was significant at an alpha level of .001 (mean associated rating

= 5.68, mean unassociated rating 3.25). These twenty-eight triplets were then employed to create

the experimental materials for the self-paced reading study.

Self-Paced Reading Study

Participants

Forty-three participants (26 female, 17 male) from the University of Florida population

participated in the experiment for course credit, and gave informed consent according to

University of Florida IRB procedures. All participants had no known speech or hearing disorders

as indicated by self report. The mean age of participants was 20.4 years (range 18 to 28). Data










from seven participants were excluded from analysis based on responses to the accompanying

the language questionnaire that showed that they were not monolingual native speakers of

English. Thus, the data from 36 participants was analyzed.

Materials

The twenty-eight noun triplets from the questionnaire study were inserted into the

experimental paradigm (11i), yielding twenty-eight sets of experimental items. Note that in the

critical region starting from the determiner after the conjunct, the four conditions are physically

similar.

Across the twenty-eight sets, four neutral verbs ('talk to', 'walk with', 'meet with', 'ask

about') were each repeated seven times. This was done to ensure that there were no differences

in thematic fit between noun and verb across items, and that the ambiguous noun in post-

conjunction position could serve equally well as the agent and the patient of the verb. Each

participant saw seven items from each experimental condition as well as fifty-six fillers. The

fillers were constructed with the following aims: to balance out the number of S and NP

coordinations across the entire set of experimental materials thus precluding the development of

implicit processing strategies by the participant, to vary the clause boundary so that it could not

be predicted purely by linear position, to ensure that all conjunctions not signal a clause

boundary, and to form as natural a set of materials as possible by introducing different verbs and

types of nouns.

Four item groups were created by dividing the twenty-eight experimental items into

groups of seven. Across these groups, the difference between associated and unassociated pairs

was held constant such that a comparison of these conditions yielded non-significant results. A

one-way ANOVA with the factor group was conducted, yielding a p-value of .878. This

confirmed that across item groups, there was no significant difference in the difference between










associated and unassociated pairs. Unfortunately, because of the manner in which the critical

nouns were selected and the limited number of creatable noun pairs with the desired

characteristics; we were unable to balance length and frequency across lists or item groups. We

instead focused on balancing association strength, which is critical to the experimental

manipulation.

The item groups were then distributed across four participant lists, and counterbalanced.

In this way each participant only saw each item in one condition, and all items were seen an

equal number of times in all conditions. Fillers and experimental items were pseudo-randomized

such that no two experimental items followed each other.

Participants were probed with comprehension questions after each sentence. These

questions were designed to probe the role assigned to the ambiguous noun phrase after the

conjunction in the experimental conditions, in order to determine whether the reader recovered

from the garden path. For example, the sentence, "the enemy talked to the king and the queen

talked to the people," would be probed with the sentence, "Did the enemy talk to the king?" The

remainder of the comprehension questions probed relationships between the other arguments in

the sentences. The complete set of experimental materials and some examples of fillers sentences

are attached in the appendix.

Procedure

Participants were individually tested. Stimulus presentation and data acquisition was

controlled using E-Prime (Psychology Software Tools) running on a PC. The experiment

employed a self-paced reading, moving window paradigm. Before beginning the experiment,

each participant was familiarized with the task with instructions and a brief practice block of five

items. After we were certain that the participants understood the task, the experiment began and

proceeded as follows: The trial began with a series of dashes on the screen which represented









each word of the sentence (with the number of dashes corresponding to the number of letters in

each word), and the participant pressed the "enter" button on the button box for the first word

(presented in size 15, courier new; black text on white screen) to appear. Each successive press

of the "enter" button caused the current word to disappear and the next word in the sentence to

appear. This continued to the end of the sentence at which point the question related to the

previous sentence appeared on the screen with instructions to press the "Y: button for yes, and

the "N" button for no. Once the participant answered the question, a "press X for next" screen

appeared. Once the participant pressed the "X" button, the screen disappeared and the next trial

proceeded as described above.

Analysis

Reaction time data from the remaining thirty-six participants were first trimmed using the

following procedures: Any data point exceeding 3000 msec was treated as missing during the

analysis, this procedure affected .007% of the data. Additionally, means were calculated at each

word position for each condition for each participant and any data point that exceeded the mean

plus or minus 2 standard deviations was replaced with the mean, affecting .05% of the data. A

repeated measures ANOVA was conducted on the participant (F l) and item means (F2) with the

factors ambiguity (2 levels) and parallelism (2 levels) as within subj ect (item) factors, and item

as a between item factor and list as a between subject factor. Question accuracy and RT data

were analyzed using a two-way ANOVA with factors ambiguity and parallelism.









CHAPTER 3
RESULTS

Comprehension Data

Accuracy

Overall, questions probing the experimental materials were answered quite accurately.

Table 1 summarizes comprehension data on the four experimental conditions. The results of

the two-way ANOVA revealed a significant effect of ambiguity [Fl(1,35)=14.316, p < .001;

F2(1,27)=4.44, p < .05], with accuracy on questions probing ambiguous items significantly lower

(mean =89.3%) than accuracy on non-ambiguous items (mean= 93.7%). There was also an

effect of parallelism, that was significant by subj ects but not by items [F l (1, 3 5)=6. 171, p < .05;

F2 (1,27)=2.766, p=.108], with accuracy on questions probing parallel items higher (93.7%) than

on the non-parallel items (88.8%). Additionally, the interaction between ambiguity and

parallelism was significant [Fl (1,35)=36.594, p < .001; F2(1,27)=17.016, p < .001]. The pattern

of the interaction reveals that there is a large accuracy difference between the two non-parallel

conditions, while the mean accuracy to the parallel conditions is much closer. Post-hoc Tukey's

pairwise comparisons on accuracy by condition indicated that accuracy on questions probing the

non-parallel, ambiguous condition was significantly lower than for on all other experimental

conditions (p < .001 in all three comparisons).

Reaction Time

Question response times pattern with the accuracy data. The results of the ANOVA

indicated that the interaction between parallelism and ambiguity was significant [Fl

(1,35)=13.367, p < .001; F2 (1,27)= 14.008, p < .001]. The pattern of the interaction reveals that

there is a large reaction time difference between the two non-parallel conditions, while the mean

reaction time to the parallel conditions is much closer There was a marginal main effect of










ambiguity [Fl1(1,3 5)=3.723, p=.062; F2 (1,27)=3.089, p=.090], though the means do illustrate

that participants took longer to answer questions probing ambiguous (2778 ms) than non-

ambiguous (2547 ms) items. There was no main effect of parallelism [Fl1(1,35)=1.347, p=.254,

F2 (1,27)=. 868, p=.360]. Mean reading times do however indicate that subj ects took longer to

answer questions probing non-parallel items (2742 ms) than parallel items (2578ms).

Reading Time Data

A GLM repeated measures ANOVA was performed on all experimental items with the

within-subj ect factors ambiguity (ambiguous or not) and parallelism (parallel or not), and the

between-subj ect factors list and item group. An analysis including only correct items did not

yield qualitatively different results, and will therefore not be discussed. Table 2 presents the

reading times at position 5 (the determiner of the pre-conjunction noun phrase) and each

subsequent position and Eigure 1 summarizes reading times at all positions in the experimental

sentences.

The ANOVA revealed an effect of parallelism at the pre-conjunction noun that was

significant by items [F l(1,32)=2.98, p=.09; F2(1,24)=7.12, p< .05] and an effect at the post-

conjunction noun that was significant by subj ects but marginal by items [Fl1(1,32)=5.125, p< .05;

F2(1,24)=3.199, p=.086], with the non-parallel items taking longer to read than the parallel items

at both positions. There was also an interaction between ambiguity and parallelism at position

11, which was significant by subjects only [Fl(1,24)=4.575, p < .05; F2(1,32)=1.45, p=.24].

The pattern at this position reveals that the non-parallel ambiguous condition takes the longest to



SThe discrepancy between p-values in the F1 and F2 analyses can be explained by the manner in which the items
were controlled. Controlling for association between associated and non-associated pairs across lists and item
groups dictated that frequency and length could not be adequately controlled for. We believe that this led to the
differences in significance in the F1 and F2 analyses.

























Table 1-1: mean RT and accuracy per condition
NonParallel, Amb NonParallel, NonAmb Parallel, Amb Parallel, NonAmb

Accuracy 81.1% (.39) 96.8% (. 12) 97.2% (. 15) 90.6 %(.29)

RT 3051 (1069) 2433 (785) 2505 (813) 2652 (1021)




Table 1-2: mean (SD) reading times by condition
the N conj. the N V P the N.

N-P, A 356(14) 510(41) 426(19) 364(11) 442(29) 421(19) 364(12) 346(11) 725(51)

N-P, N-A 370(15) 473(32) 411(16) 367(13) 404)414(22) 345(9) 337(10) 688(35)

P, A 363(24) 463(34) 446(22) 377(14) 417(19) 411(18) 346(11) 348(10) 702(51)

P, N-A 361(12) 459(32) 425(21) 383(18) 436(25) 393(14) 346(9) 353(10) 719(47)


read, while the parallel ambiguous condition and the two non-ambiguous conditions have

virtually identical means.

The analysis revealed no main effects of ambiguity at any position. Main effects of and

interactions with list and item group ranged from p=.018 to p=.969, and all effects at other

positions were non-significant.













750

700

650

600

550

500






300


-* -N-P A
- --o-- -N-P, N-A

~-P, A
---0--- P, N-A


Figure 2-1: mean reading times at each position (by subj ects)









CHAPTER 4
DISCUSSION

The goal of the present study was to provide data that would help resolve two of the more

prevalent debates in the sentence processing literature. By employing a manipulation that varied

which previous noun phrase the ambiguous noun phrase in a coordination ambiguity was

semantically associated with, and probing the attachment of this ambiguous noun phrase with

comprehension questions; the present study was designed to provide data that distinguished

between constraint based versus syntax-first parsers, and between exhaustive, algorithmic

parsing and parsing that outputs merely "good-enough" representations. We hypothesized that if

semantic information is taken into account during parsing, reading time at the disambiguating

region in the non-parallel, ambiguous condition would be elevated in comparison with the

parallel, ambiguous condition; and that differences in accuracy to ambiguous and non-ambiguous

conditions would provide evidence for a parser that sometimes outputs "good-enough"

representations. Comprehension and reading time data will be discussed before they are placed

in the context of models of processing and representation.

Comprehension Data

The data reveal that subjects answered questions probing non-ambiguous items more

accurately than questions probing their ambiguous counterparts. Subj ects were also more

accurate when responding to questions in the parallel conditions than when responding to the

non-parallel conditions. These two factors also interacted significantly, with a large accuracy

difference between the two ambiguous conditions that was almost twice the difference between

the two non-ambiguous conditions.

The demonstration that participants respond more accurately to questions probing non-

ambiguous (93.7%) than questions probing ambiguous items (89.3%) supports the notion that










participants sometimes do not overwrite or suppress their initial interpretation of a sentence, even

when that interpretation is erroneous. Extending results of Ferreira et al. (2002) and Christianson

et al. (2001) with a different construction, these results appear to demonstrate that the initial

misinterpretation of a sentence can persist even in the face of disambiguating input. It appears

that in the ambiguous conditions, readers sometimes attach the ambiguous noun phrase as an

obj ect of the first verb (based on either minimal attachment or the higher frequency of the NP

coordinate structure). Even after the main verb of the second clause is encountered and it

becomes clear that the ambiguous noun phrase is actually a subj ect, this reading survives to the

extent that it can effect question answering by lowering accuracy. The present results cannot

distinguish between the different accounts of this effect (underrepresentation, a lack of re-

analysis, or persistence of the initial analysis), but they do seem to indicate that readers

sometimes rely on representations that are not the result of exhaustively analyzing the input until

the correct structure is built. The comparison of accuracy to parallel and non-parallel conditions

also reached significance, as did the interaction between ambiguity and parallelism. The

accuracy to parallel conditions (93.7%) was higher than accuracy to non-parallel items (88.8%).

These results provide evidence that purely semantic information can affect comprehension of a

sentence. The data on the accuracy to questions probing non-parallel ambiguous (81.1%) and

parallel, ambiguous trials (97.2%) are also very interesting. This large difference in accuracy to

syntactically identical ambiguous constructions may be because participants are relying on

semantics when answering these questions. In the case of the parallel ambiguous conditions,

semantic information supports the correct structure in which the associated nouns are subjects of

their own clauses. Accuracy is high in this condition. In the non-parallel conditions, the

semantic information supports the wrong structure in which the associated nouns are both










objects, and consequently accuracy is low in this condition. If this is the case, then it can provide

some insight into a heuristic processor that does not always decommit from its initial

interpretation and/or revise after mis-analysis. This type of processor may output a

representation that is structurally underspecified due to a lack of re-analysis, or it may output

multiple structures that represent all interpretations entertained during the parsing process

leading to interference between correct and incorrect structures. Regardless of the exact

mechanism leading to deficits in structural representation, it appears that the language system

can recruit other sources of information to mask these inadequacies. When probed on a sentence

of which it has an inadequate representation, the system resorts to semantic sources of

information. When these cues are present and supportive, they are enough to override the

difficulty engendered by an inadequate representation. This is evidenced by the high accuracy to

the parallel, ambiguous condition (97.2%). However, when these cues are not present or support

the wrong interpretation, the system is left to deal with its deficits in structural representation and

accuracy drops sharply (81.1%). The reaction time data gathered from the comprehension

questions supports the error patterns described above. While comparisons of the experimental

factors do not reach significance, the pattern of the means supports the above conclusions. The

non-parallel, ambiguous condition which yielded the lowest accuracy also yielded the highest

reaction time (3051 ms). This indicates that there was no speed-accuracy tradeoff for the

participants. The difference between parallel, ambiguous (2505 ms) and non-parallel, ambiguous

(3051) mirrors the large difference in accuracy to these conditions and against suggests that

semantics can be recruited to facilitate off-line comprehension. When semantic cues are present,

subjects respond quickly and accurately. When these cues are not present, subjects respond

slowly and less accurately.









Reading Time Data

The data reveal a main effect of parallelism at both the pre- and post-conjunction nouns,

with non-parallel items taking longer to read than parallel items at both positions. There was

also a significant interaction between parallelism and ambiguity at the post disambiguating verb

preposition which resulted in a three versus one pattern. The non-parallel, ambiguous condition

showed an increase in reading time at this position when compared to all other conditions.

Interaction of Parallelism and Ambiguity at the Post Disambiguating Verb Preposition
(Position 11)

As our interest is most sharply focused in the disambiguating region of the sentence, let

us begin a discussion of the results there. The interaction between parallelism and ambiguity at

this position is perhaps the most intriguing finding in this study. While the interaction was only

significant by subjects and not by items (see footnote 1), this effect may provide evidence that

semantic information can override processing difficulty in a syntactically ambiguous

environment. At the preposition, the pattern of the means reveals that the parallel, ambiguous

condition patterns with the two non-ambiguous conditions. Relative to these conditions, the non-

parallel ambiguous condition shows an elevation in reading time of approximately 20 ms

reflecting processing difficulty. These data appear to demonstrate that semantic information can

eliminate the garden path effect at the disambiguating verb, as no evidence of processing

disruption is seen in the parallel, ambiguous condition. This pattern of reading times is best

explained with a constraint-based account of parsing that resolves ambiguity through the process

of structure competition. Constraint based models of sentence processing state that as the parser

incrementally interprets the input, multiple structures consistent with the input are built based on

all information currently available to the parser. These structures "compete," in that they

become relatively more or less active than their competitors as the sentence unfolds and more









information becomes available, and at the end of the sentence the structure with the highest

activation "wins." Crucially, this type of model predicts that when two analyses receive

approximately equal support from the input, severe competition will occur and processing

difficulty will result. In contrast, when one analysis receives virtually all of the support,

processing will be facilitated because of a lack of competition. The crucial sources of

information here are the NP-coordination preference, semantics, and processing biases that

develop throughout the experiment. Due to the variable contributions of these sources of

information at prior positions in the sentence, the parser reaches the disambiguating region with

structures that are competing to different degrees in the two ambiguous conditions. The differing

degree to which these structures compete can explain the data at the preposition, and explain why

the parallel, ambiguous condition patterns with the non-ambiguous conditions at this position.

As the parser processes the conjunction and the post-conjunction region, both S and NP

coordinate structures become active. Their relative levels of activation are influenced in this

region by semantics, general processing principles, and parsing preferences that develop

throughout the experiment. Different cues are available in each condition, and this leads to

variable levels of activation (and therefore competition) between the two competing structures

across the conditions. As the parser reaches the preposition in the non-parallel, ambiguous

condition the two structures are competing greatly due to the two licit structures being activated

to approximately the same extent. This causes an elevation in reading time when the parser

encounters the disambiguating verb and it becomes evident that the S-coordination reading is

correct. However, in the parallel ambiguous condition, the S-coordinate structure is already

highly active due to the contribution of semantics at previous positions in the sentence. This

eliminates processing difficulty in the disambiguating region as the correct structure is already










highly active. The observation that the parallel, ambiguous condition shows no increase in

reading time relative to the two non ambiguous constructions. suggests that the contribution of

semantics is enough to boost the activation of the S-coordination reading to the extent that it is

virtually identical to the activation of the S structure when it is unambiguously signaled by the

preposition but. These results are hard to reconcile with a syntax-first parser, even one that

claims that semantic information can be recruited rapidly to facilitate re-analysis. The sentences

are syntactically identical at this position, licensing the same two structures, so differences

among the conditions are unlikely to be based on syntactic considerations. Additionally, a claim

that a syntax-first parser is simply recruiting semantic information to re-analyze at this position

would be unfounded. If this were the case, then both ambiguous conditions would show an

elevation in reading times compared to the non-ambiguous conditions, although perhaps this

effect would be smaller for the parallel conditions, since semantic information could ease re-

analysis. This pattern is not present in the data, as only the non-parallel ambiguous condition

shows an elevation compared to the non-ambiguous items. We therefore believe that the patterns

at this position are generated by the variable contributions of semantics in a constraint-based

competition model that also calculates the probability of alternative structures based on general

parsing principles and processing strategies that are sensitive to the frequency of occurrence of

alternative structures in the materials set.

Main Effect of Parallelism at the Post-Conjunction Noun (Position 9)

The main effect of parallelism at this position is also interesting. The direction of the

effect, with the non-parallel items taking longer to read than their parallel counterparts,

eliminates the possibility that this is simple local priming between noun-phrases as the effect is

in the wrong direction. Here is the experimental paradigm again (with position 9 in bold),

provided for clarity of discussion:










Non-parallel, ambiguous
The enemy talked to the king and the queen talked to the people.
Non-parallel, non-ambiguous
The enemy talked to the king but the queen talked to the people.
Parallel, ambiguous
The king talked to the enemy and the queen talked to the people.
Parallel, non-ambiguous
The king talked to the enemy but the queen talked to the people.

The difference in reading time between the non-ambiguous conditions can again be

explained through a constraint based model of parsing. While competition is limited because the

conjunction but only licenses S-coordination, the contribution of semantics can still explain the

increase in reading time in the non-parallel, non-ambiguous condition compared to the parallel,

non-ambiguous condition. In the parallel condition, the semantics of the noun phrase support the

S-coordination that is highly activated, while in the non-parallel condition semantics provides

interference against the S-coordinate reading. This leads to a reduction of the activation of the S-

coordinate structure, and thus an increase in reading time to the non-parallel, non-ambiguous

condition.

The difference between the two ambiguous conditions at this position is perhaps more

interesting. One of the primary goals of the experiment was to determine if semantic association

could influence the attachment of this ambiguous noun phrase. It appears as if it can, and the

interaction of semantics, general parsing principles, and experiment specific strategies can

explain the differences between ambiguous conditions at this position. In contrast to the non-

ambiguous items above, when the parser encounters the conjunction and two structures become

active as and licenses both S and NP coordination. The initial pattern of activation should favor

the NP-coordinate structure, as it is this structure that is predicted by minimal attachment and the

observation that NP coordination enj oys a large advantage over S-coordination in terms of real-

world frequency of occurrence (Hoeks, 2006). As the parser reaches the post conjunction noun









in these constructions, the contributions of experiment specific biases and semantics generate a

different pattern of activation across the ambiguous conditions. This leads to a high degree of

competition in the non-parallel condition, and a considerable advantage for the S-coordinate

structure in the parallel condition. This variable level of competition can explain both the

elevation in reading time at this position for the non-parallel items as well as provide the reason

that these two conditions reach the disambiguating region with different levels of competition

between alternatives as described above. The contribution of semantics is clear; it supports S-

coordination in the parallel conditions and NP-coordination in the non-parallel conditions, but

the contribution of experiment-specific parsing principles must be elucidated. As stated earlier,

NP coordination is statistically much more frequent in natural language, this assertion is

supported by completion and corpora studies (Hoeks, 2006). However, following psycho-

linguistic research methods, the number of S and NP coordinations in the present study was

balanced to inhibit the development of processing strategies throughout the experiment based on

the probability of encountering one of the two alternative structures that and licenses. Based on

the data, it appears that this balancing had the opposite effect and actually induced the parser to

modify its attachment preferences. It appears that the parser is sensitive to the discrepancy

between the probability of encountering one of two alternate structures in the real world and the

same probability within the materials set. This discrepancy causes the parser to modify general

principles to lower processing difficulty across the board. This leads to an attenuation of the NP-

coordination preference, and enables semantics to have more of an effect in the post-conjunction

region. This idea is supported by an analysis that included "time" as a factor to determine

whether participants are reacting to the disambiguating region differently at the beginning and

end of the experiment. The experimental sentences that occurred during the first 25% of the










experiment show a robust garden path effect at the disambiguating verb in the two ambiguous

conditions indicating that the parser is initially creating NP coordinate structures when

encountering and, this effect averages 45 ms. However, this effect has been reduced to 7.5 ms in

experimental trials that occur during the last 25% of the experiment. While the interaction of

ambiguity and "time" does not reach significance at the verb due to the necessity of only

analyzing a subset of items [Fl1(1,3 5)=1.91, p=. 168], this pattern is suggestive that the parser

employed the frequency with which S and NP coordinate structures occur within the experiment

to modify the NP coordination preference and reduce processing difficulty as the experiment

progressed. This interpretation generates testable predictions. Namely, that by modulating the

frequency of alternative structures within an experimental set either towards or away from

preferences that have been established by the parser in response to real world frequencies;

varying results will be observed. If this prediction is proven true, it would be of great

methodological consequence. For instance, if a set of materials was created in which S

coordinations were much more frequent than their NP counterparts (opposite of the distribution

in natural language), one would predict garden path effects in the disambiguating region of the

NP coordinate structures. These results are difficult to interpret under a syntax-first view, as

semantic information appears to be having an effect before the disambiguating region triggers

revi sion.

The main effect of parallelism at the pre-conjunction noun is difficult to interpret. At this

position, non-parallel conditions take longer to read than parallel conditions. This effect is not

due to length or frequency differences between the nouns in the two conditions, and cannot be

explained through recourse to syntax-first or constraint based parsing models. One speculative

account is that the participants have more trouble constructing a mental model in the non-parallel









conditions due to the arrangement of the noun phrases. In this case, plausibility at the "real

world" level is the crucial factor. This account would have to be further pursued by conducting

norming studies on the experimental materials.

The Relationship between Comprehension and Reading Time Data

When interpreting the reading time and comprehension data simultaneously, a clear

picture emerges. It appears that the semantic manipulation in the experimental materials has an

effect on both online and omfine linguistic processing. In terms of online processing, we see

clear effects of the semantic manipulation at both the post-conjunction noun and the post-verbal

preposition. At these positions, the additional semantic information provided by the

manipulation facilitates processing and reduces the difficulty that is encountered in the

disambiguating region of the sentence by reducing the level of competition between alternative

structures. In terms of offine processing, this same semantic information increases accuracy and

decreases response time when answering questions. The experimental condition that generates

the most processing dimfculty online also causes the most dimfculty omfine, as subj ects spend

longer and answer less accurately than to any other condition.

Syntax-First versus Constraint-Based Models

The results of this experiment are most compatible with a constraint-based model of

sentence processing in which alternative structures compete based on evidence from the input. It

is very dimfcult to reconcile this data with a syntax-based parser that grants primacy to structural

factors. At the post-conjunction noun in the experimental materials there is a main effect of

parallelism. At this position non-parallel conditions show an increase in reading times compared

to parallel conditions (both ambiguous and non-ambiguous). Crucially, the non-parallel

ambiguous condition takes longer to read than the parallel, ambiguous condition. This effect is

dimfcult to explain without recourse to some non-structural factors. At this position in the









sentence, when comparing parallel to non-parallel ambiguous, the structures are equally

ambiguous. In both sentences at this position, both the S and NP coordination readings are

licensed by the rules of syntax. The only difference between these items is in the lexical

association between the lexical item currently being parsed and a lexical item somewhere else in

the sentence. What then causes the increase in reading time? We believe that this elevation is a

result of increased competition between alternatives receiving equal amounts of support in the

non-parallel ambiguous condition. An explanation based purely on syntax fails here, as does an

account in which a syntax-based parser recruits semantic information during re-analysis as the

disambiguating region has yet to be reached and re-analysis has therefore yet to be initiated. At

the post-disambiguating verb preposition, there is a significant interaction between parallelism

and ambiguity that we also believe to be evidence for constraint-based parsing in these

constructions. At the preposition, evidence of processing difficulty only appears in the non-

parallel, ambiguous condition. The parallel ambiguous condition does not show this disruption

and the mean reading time at this position is virtually identical to the means of the non-

ambiguous conditions. We feel that this lack of difficulty in the parallel ambiguous condition is

due to the heightened activation of the S reading over the NP reading due to the relative

contributions of constraints at the post-conjunction noun. Even proponents of a syntax-based

parser that recruits semantic information for rapid re-analysis would have trouble explaining this

effect at this position. Perhaps this is the case and the methodology employed lacked the

sensitivity to detect residual processing difficulty, but the reading time data appear to illustrate

that the semantic information provided by the prior context is enough to eliminate processing

difficulty entirely. For these reasons, we feel that our data are most consistent with a constraint

based parser that considers all available sources of information to create multiple structures in










parallel, with the structure that receives the most support from the input mapping on to the

meaning of the sentence.

"Good-Enough" Representations in Sentence Processing"

A secondary aim of this research was to discriminate between fully detailed and "good

enough" representations in sentence processing. While the data collected here is relatively

limited in this regard, it does point to a sentence processor that outputs representations that are

not always the result of exhaustively analyzing the input. Our accuracy data indicate that

participants do not always re-analyze their interpretation or suppress it to the extent that it cannot

influence comprehension. It appears that this initial mis-interpretation can persist to the extent

that it can affect comprehension. Interestingly, our data also support the notion that this type of

heuristic syntactic processing may be aided by semantic cues in a manner that masks its

representational deficits. When support from semantics was not present in the ambiguous

constructions, participants experienced a huge drop in accuracy when compared to when the

semantic cues were present. We feel that this type of processor may use these additional cues to

mask when structural processing is not complete and only "good enough," in the same way that

employing semantic cues help Broca's aphasics make structural decisions when their receptive

grammatical deficits prevent them from undertaking a complete analysis. The degree of fall-off

once these cues are taken away is not as dramatic in the current participants, but conceptually we

believe the recruitment of semantic cues to mask structural deficits may be the same. In

conclusion, our accuracy data are not conclusive in either direction, but do appear to support the

notion that comprehenders often rely on representations that are not fully detailed in terms of the

correct structure of the input either because of a lack of full re-analysis or an inability to suppress

the representation that resulted from an incorrect parse.









CHAPTER 5
CONCLUSION

The reading time study described here was designed to investigate whether information

regarding semantic association would facilitate processing in the disambiguating region of a

coordination ambiguity and also whether the end result of parsing this construction is fully

specified. The answer to the first question appears to be yes. During the experiment, processing

difficulty appeared to be eliminated by the semantic manipulation to the extent that the parallel,

ambiguous condition patterned with the two non-ambiguous conditions at the post-

disambiguating verb preposition. There was also an effect of the semantic manipulation in the

pre-disambiguating region, providing further evidence for the influence of semantics on the first-

pass parse. In terms of the nature of the output of parsing these constructions, we observed

significant differences in accuracy to ambiguous and non-ambiguous constructions; indicating

that perhaps participants weren't completely re-analyzing the input or were failing to suppress

the initial incorrect parse. Evidence was also found that suggests that the parser may modify

attachment preferences in response to the discrepancy between the frequency of alternative

structures in the real world and the materials set.

These Eindings provide support for a constraint-based parser that takes semantic

information into account when building the parse, and that is also sensitive to the probability of

encountering possible alternate structures in the real world and in the context of an experiment.

The parser may output underspecified representations or fail to suppress representations that lead

to clashes in terms of thematic role assignment and deficits in comprehension.









CHAPTER 6
FUTURE WORK

The data presented here represent only an initial investigation into the effects that non-

structural sources of information can have on the attachment of the ambiguous noun phrase in a

coordination ambiguity. Future projects include investigating the manipulation described herein

with more sensitive experimental techniques, such as eye-tracking or Event Related Potentials

(ERPs). I also plan to investigate the effects that a fine grained plausibility manipulation or verb

differences at the discourse level may have on the parser' s preferences at this noun phrase. A

study currently under preparation will investigate the role that the relative frequency of NP and S

coordination within the materials set can have on the attachment of this noun phrase.

Conclusions drawn from the data generated by this study will be of great theoretical interest.










APPENDIX A
EXPERIMENTAL MATERIALS


1. h eie tle t eetii a t pub tle t frmn
a. The resident talked to the electrician and the plumber talked to the foreman.
b. The elresident talked to the relietrican bu the plumber talked to the foreman.
c. The electrician talked to the resident and the plumber talked to the foreman.



a. The enemy talked to the queen and the king talked to the people.
b. The enemy talked to the queen but the king talked to the people.
c. The king talked to the enemy and the queen talked to the people.
d. The king talked to the enemy but the queen talked to the people.


3. Tegettle otewf n h ubn akdt h oas
a. The guest talked to the wife and the husband talked to the locals.
b. The gufes talked to the wifes but the husband talked to the locals.
c. The wife talked to the guest and the husband talked to the locals.



a. The client talked to the architect and the builder talked to the contractor.
b. The client talked to the architect but the builder talked to the contractor.
c. The architect talked to the client and the builder talked to the contractor.
d. The architect talked to the client but the builder talked to the contractor.


5. Tevci akdt h oiea n h iea akdt h aiy
a. The victim talked to the policeman and the fireman talked to the family.
b. The voictima talked to the poiciman bu the fireman talked to the family.
c. The policeman talked to the victim and the fireman talked to the family.



a. The parent talked to the teacher and the student talked to the classmate.
b. The parent talked to the teacher but the student talked to the classmate.
c. The teacher talked to the parent and the student talked to the classmate.
d. The teacher talked to the parent but the student talked to the classmate


7. Teauttle oteepr n h oietle otecas
a. The adult talked to the expert and the novice talked to the class.
b. The adulrt talked to the expert but the novice talked to the class.
c. The expert talked to the adult and the novice talked to the class.











a. The coach walked with the swimmer and the diver walked with the fan.
b. The coach walked with the swimmer but the diver walked with the fan.
c. The swimmer walked with the coach and the diver walked with the fan.
d. The swimmer walked with the coach but the diver walked with the fan.



9. Temse akdwt h adadtebte akdwt h is
a. The master walked with the maid and the butler walked with the kids.
b. The maste walked with the maid butn the butler walked with the kids.
c. The maid walked with the master and the butler walked with the kids.


10.
a. The parents walked with the sister and the brother walked with the grandparents.
b. The parents walked with the sister but the brother walked with the grandparents.
c. The brother walked with the parents and the sister walked with the grandparents.
d. The brother walked with the parents but the sister walked with the grandparents.

11.
a. The friend walked with the blonde and the brunette walked with the salesman.
b. The friend walked with the blonde but the brunette walked with the salesman.
c. The blonde walked with the friend and the brunette walked with the salesman.
d. The blonde walked with the friend and the brunette walked with the salesman.

12.
a. The servant walked with the lady and the gentleman walked with the children.
b. The servant walked with the lady but the gentleman walked with the children.
c. The lady walked with the servant and the gentleman walked with the children.
d. The lady walked with the servant and the gentleman walked with the children.

13.
a. The neighbor walked with the son and the daughter walked with the cop.
b. The neighbor walked with the son but the daughter walked with the cop.
c. The son walked with the neighbor and the daughter walked with the cop.
d. The son walked with the neighbor but the daughter walked with the cop.

14.
a. The trainer walked with the pitcher and the catcher walked with the umpire.
b. The trainer walked with the pitcher but the catcher walked with the umpire.
c. The pitcher walked with the trainer and the catcher walked with the umpire.
d. The pitcher walked with the trainer but the catcher walked with the umpire.










15.
a. The scout met with the actress and the actor met with the audience.
b. The scout met with the actress but the actor met with the audience.
c. The actor met with the scout and the actress met with the audience.
d. The actor met with the scout but the actress met with the audience.


16.
a. The reporter met with the judge and the jury met with the criminal.
b. The reporter met with the judge but the jury met with the criminal.
c. The judge met with the reporter and the jury met with the criminal.
d. The judge met with the reporter but the jury met with the criminal.


17.
a. The intern met with the producer and the director met with the extra.
b. The intern met with the producer but the director met with the extra.
c. The producer met with the intern and the director met with the extra.
d. The producer met with the intern and the director met with the extra.

18.
a. The candidate met with the faculty and the staff met with the dean.
b. The candidate met with the faculty but the staff met with the dean.
c. The faculty met with the candidate and the staff met with the dean.
d. The faculty met with the candidate but the staff met with the dean.

19.
a. The student met with the chemist and the biologist met with the technician.
b. The student met with the chemist but the biologist met with the technician.
c. The chemist met with the student and the biologist met with the technician.
d. The chemist met with the student but the biologist met with the technician.

20.
a. The slave met with the prince and the princess met with the ruler.
b. The slave met with the prince but the princess met with the ruler.
c. The prince met with the slave and the princess met with the ruler
d. The prince met with the slave but the princess met with the ruler

21.
a. The boss met with the receptionist and the secretary met with the representative.
b. The boss met with the receptionist but the secretary met with the representative.
c. The receptionist met with the boss and the secretary met with the representative.
d. The receptionist met with the boss but the secretary met with the representative.










22.
a. The passenger asked about the co-pilot and the pilot asked about the stewardess.
b. The passenger asked about the co-pilot but the pilot asked about the stewardess.
c. The co-pilot asked about the passenger and the pilot asked about the stewardess.
d. The co-pilot asked about the passenger but the pilot asked about the stewardess.

23.
a. The officer asked about the killer and the victim asked about the punishment.
b. The officer asked about the killer but the victim asked about the punishment.
c. The killer asked about the officer and the victim asked about the punishment.
d. The killer asked about the officer but the victim asked about the punishment.

24.
a. The writer asked about the hero and the villain asked about the family.
b. The writer asked about the hero but the villain asked about the family.
c. The hero asked about the writer and the villain asked about the family.
d. The hero asked about the writer but the villain asked about the family.

25.
a. The referee asked about the winner and the loser asked about the crowd.
b. The referee asked about the winner but the loser asked about the crowd.
c. The winner asked about the referee and the loser asked about the crowd.
d. The winner asked about the referee but the loser asked about the crowd.

26.
a. The customer asked about the chef and the cook asked about the busboy.
b. The customer asked about the chef but the cook asked about the busboy.
c. The chef asked about the customer and the cook asked about the busboy.
d. The chef asked about the customer but the cook asked about the busboy.

27.
a. The relative asked about the bride and the groom asked about the band.
b. The relative asked about the bride but the groom asked about the band.
c. The bride asked about the relative and the groom asked about the band.
d. The bride asked about the relative but the groom asked about the band.

28.
a. The child asked about the minister and the preacher asked about the congregation.
b. The child asked about the minister but the preacher asked about the congregation.
c. The minister asked about the child and the preacher asked about the congregation.
d. The minister asked about the child but the preacher asked about the congregation.










APPENDIX B
FILLER SENTENCES

AndNP coordination

1. The lion hunted for a zebra and a buffalo in the long grass.
2. The manager spoke with the assistant and the janitor during their lunch break.

Or NP coordination

3. Alex had to meet with Jason or Stephen to work on their new design.
4. The antelope was eaten by a leopard or a hyena during the night.

Since S coordination

5. Since Julie covered for Sara Whitney had to come in to work today.
6. Since a citizen shouted at the mayor the governor has been more careful.

Because S coordination

7. Because the scientist lied about the data the public did not know the truth.
8. Because the accountant mixed up the numbers the banker lost his new j ob.











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BIOGRAPHICAL SKETCH

Christopher Barkley was born on January 22nd 1982 in Edinburgh, Scotland. After

spending four years in Scotland, Christopher moved to Ingrave, a small village just outside of

London, England. When his father was transferred to a banking position in America,

Christopher moved to Jacksonville, FL, in 1992. Chris attended elementary, middle, and high

school in Jacksonville until he graduated from the Paxon School for Advanced Studies in 2000.

After graduating high school, Chris enrolled at the University of Florida. He obtained his

bachelors degree with a maj or in linguistics in 2005 and his Master of Arts in 2007. Chris is

currently enrolled in the interdisciplinary program in Linguistics and Cognitive Science at the

University of California, San Diego.