Sensitivity to Syntactic Changes in Garden Path Sentences ...

J Psycholinguist Res (2008) 37:391–403 DOI 10.1007/s10936-008-9072-4 ORIGINAL ARTICLE

Sensitivity to Syntactic Changes in Garden Path Sentences Kiel Christianson

Published online: 29 April 2008 © Springer Science+Business Media, LLC 2008

Abstract The results of two text-change experiments are reported. The experiments were designed to investigate the syntactic representation of garden path sentences such as While the man hunted the deer that was brown and graceful ran into the woods, specifically the claim that a significant number of misinterpretations of such sentences are due to incomplete syntactic reanalysis (Christianson et al. Cogn Psychol 42:368–407, 2001). In the experiments reported here, the pronoun it was added (Expt. 1) or deleted (Expt. 2) from short texts containing such sentences. Participants were more or less likely to notice both deletions and additions of it in certain syntactic contexts, as predicted by the incomplete reanalysis account. Correlations with reading times support this interpretation of the results. Overall, the data are consistent with a “good enough” view of language processing (Ferreira et al. J Psycholinguist Res 30:3–20, 2001). Keywords Sentence comprehension · Syntactic parsing · Good-enough language processing · Reading

Introduction A central assumption in the study of language comprehension has been that sentence meaning is derived from a structural representation that is faithful to both the input and the grammar of the language (Frazier and Clifton 1996; MacDonald et al. 1994). A growing body of research has demonstrated, however, that under certain conditions, people in fact derive interpretations of linguistic input that are not completely faithful to the content of the input. Much of this research has focused on so-called shallow semantic processing, building on the classic Moses Illusion (Erickson and Mattson 1981), in which people are relatively insensitive to semantic

K. Christianson (B) Department of Educational Psychology and Beckman Institute, University of Illinois, Urbana-Champaign, Education Building, Rm. 226A, MC-708, 1310 S. 6th St., Champaign, IL 61820, USA e-mail: [email protected]

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anomalies in sentences such as, How many animals of each type did Moses take on the ark? or Suppose there was an airplane crash right on the border of France and Spain. Where should the survivors be buried? (Barton and Sanford 1993). The growing consensus among researchers is that linguistic representations are often underspecified (Sanford 2002; Sanford and Sturt 2002; Sturt et al. 2004), and that the degree to which they are underspecified is modulated by specific task or communicative demands (Ferreira et al. 2002; Swets et al. 2008). The degree to which the syntactic representation may remain underspecified has received somewhat less attention than the semantic representation. At least one major theory of syntactic parsing (Frazier and Clifton 1996) predicts that ambiguous “secondary,” or adjunct, phrases or clauses such as who was on the balcony in (1) might remain “associated” with a higher constituent rather than fully attached. Christianson et al. (2001) presented data strongly suggesting that even the attachment of arguments that are misanalyzed during the initial parse of garden path sentences such as in (2–3) might not be resolved completely. (1) (2) (3)

Someone shot the servant of the actress who was on the balcony. While the man hunted the deer that was large and brown ran into the woods. While Anna dressed the baby that was cute and cuddly spit up on the bed.

Christianson et al. (2001) measured people’s interpretations of sentences like (2–3) by asking comprehension questions such as Did the man hunt the deer? or Did Anna dress the baby? They found that people consistently and confidently (as measured by confidence ratings) answered “Yes” (i.e., incorrectly according strictly to the syntax of the sentence) to such questions approximately 75% of the time for sentences like (2) and 65% of the time for sentences like (3). Based on the results from a series of experiments in which syntactic manipulations modulated the rate of incorrect response, Christianson et al. (2001) argued that a failure to fully reanalyze the syntactic structure of the initial incorrect parse led ultimately to misinterpretation above and beyond what can be ascribed to simple inference. The strongest evidence for this view was the consistently high rate of misinterpretation even in sentences like (3), in which full reanalysis results in a mandatory reflexive interpretation (i.e., Anna must be dressing herself), leaving little room for inference as compared to (2). The above results were replicated by Christianson et al. (2006), who also found that older readers with less working memory capacity responded at chance to questions like, Did Anna dress herself? after reading sentences like (3). This performance was significantly worse than that of older readers with more working memory capacity and young adult readers. Christianson et al. (2006) proposed that full syntactic reanalysis was required to reactivate the syntactic structure necessary to instantiate the c-command relationship (Chomsky 1986) between Anna and the object position of reflexive absolute transitive verbs such as dress (Trask 1993). Older readers with less working memory capacity who were unable to reconstruct the quickly decaying syntactic structure (Sachs 1967; Ferreira 2003) were also unable to perform full syntactic reanalysis. The argument put forth by Christianson and colleagues is that syntactic reanalysis can, in some cases, be terminated before a single, unified, licit syntactic structure is constructed. This incomplete processing has been termed “good-enough” language processing (Christianson et al. 2001, 2006; Ferreira et al. 2001, 2002). The two experiments presented here use a text-change paradigm to address the issue of incomplete syntactic reanalysis. It is argued that in a small but significant number of cases, the reanalysis of garden path sentences like (2) is terminated before completion, resulting in a syntactic structure that is inconsistent with the input. The results support a view of “good-enough” language processing as involving both syntactic and semantic levels of representation.

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Attach Anyway and “Tree-Splicing” Fodor and Inoue (1998) describe a model of syntactic reanalysis called Attach Anyway. In this account, incoming material that is inconsistent with the existing phrase structure is first attached, regardless of its syntactic incompatibility. This attachment triggers a serial, backwards, step-by-step revision of the structure, beginning at the error signal created by the most recent attachment. Thus in (2) above, ran is attached as the matrix verb, despite the fact that the only possible matrix subject NP is already serving as the direct object of the subordinate verb hunted. In order to address this first structural problem, the string the deer is, according to Fodor and Inoue, “stolen” to serve as subject for the matrix verb. Doing so, however, results in a transitive subordinate verb structure lacking a direct object. As described by Fodor and Inoue, if the parser continues its backward path through the structure, revising completely, the lexicon is accessed for an intransitive verb and, when one is found, it replaces the transitive verb and the object position of the subordinate verb is erased. Fodor and Inoue allow, however, that complete reanalysis is difficult, and the existing structure (and interpretation) can be resistant to change. They posit a Thematic Overlay Effect (TOE), which states that once a thematic role has been assigned, the noun phrase (NP) to which it has been assigned is resistant to relinquishing it. As a result, Christianson et al. (2001) propose that what happens in sentences like (2) is that the deer is stolen to serve as matrix subject, but the argument structure of the subordinate verb is never changed, and, as a result, the object node in the original, ultimately incorrect syntactic structure is never erased. In effect, two NPs remain— two deer—one phonologically and syntactically realized in the subject position of the matrix clause, and one that lingers thematically (and possibly syntactically) in the object position of the subordinate clause, but which is not realized phonologically. Good enough processing, then, describes situations in which a partial reanalysis results in an interpretation that is coherent and plausible, despite the fact that the structural representation is not, in fact, licit. In the example described above, a sort of “tree-splicing” has taken place, where a licit syntactic tree is constructed and spliced into an existing tree which continues to exert influence over the ultimate interpretation (cf. van Gompel et al. 2006 for evidence from syntactic priming). The goal of the present study was to look for evidence of the existence of an unreanalyzed, phonologically null object lingering in the hypothesized “spliced” tree. Text-Change Paradigm The text-change, or change-detection, paradigm has been used in a recent series of studies examining semantic underspecification or “shallow processing” (Sanford et al. 2005; Sturt et al. 2004). In this paradigm, participants read a short text (usually around three sentences), then they press a button to view another version of the same text (in a different font). The second version may or may not include one or more changes from the first version. The participants are asked to read the second version and simply report whether anything is changed, and if so, what. In the study of depth of semantic processing, the logic behind this paradigm is straightforward: The more deeply an individual lexical item is processed, the more likely it is that any changes in meaning to that item will be noticed. Thus, if the word hated appears in the first version of the text, and is relatively shallowly processed, a change to disliked in the second text is more likely to be missed than a change to the semantically more distant enjoyed. The present study employs the text-change paradigm in an investigation of syntactic processing, but the general idea is the same as in the semantic domain: The likelihood of detection

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of a change in the second version of a text should depend on the details of the representation constructed during the reading of the first version of the text. In the case of incomplete reanalysis resulting in a good enough representation based upon a “spliced” syntactic tree, we would expect that surface changes to the string that are consistent with the underlying tree would be relatively difficult to detect. For example, if (4a) were changed to (4b), such that an it fills the object position of the subordinate verb, precisely where the hypothesized undeleted syntactic node might still remain in a partially reanalyzed structure, such a change might be small enough and consistent enough with the good enough syntactic representations so as to be difficult to detect. (4) a. While the man hunted the deer that was large and brown ran into the woods. b. While the man hunted it the deer that was large and brown ran into the woods. The strongest prediction in such a paradigm that could be made based on Christianson et al.’s (2001, 2006) results would be that people might be completely insensitive to the insertion of an it in the direct object position of the subordinate verb. Of course, a number of other factors might make a syntactic change such as this more or less easy to detect. One is the backwards anaphora, or cataphora, that is created by adding a pronoun before its antecedent (Petrovitz 1996; van Gompel and Liversedge 2003). This factor will be discussed in more detail below. Also, simply adding a word—even one as short as it—might be too large a change, and too easy to detect. If so, then the text-change paradigm could be considered unsuitable for investigations such as this. A weaker prediction, however, would predict that even if change detection is easier when garden path sentences are involved, the likelihood of detecting the it in the subordinate object position should be lower even in resultant cataphoric sentences compared to the anaphoric sentences than in non-garden path counterparts (i.e., one would expect some sort of an interaction). Finally, false alarm errors should be relatively less frequent overall in conditions where the it is easily detected; conditions in which the it fails to “jump out” should display similar rates of false alarms.

Experiment 1 Method Materials Thirty-six of the garden path sentences from Christianson et al. (2001) were adapted for the present study. For each item, two context sentences were created, one which preceded the critical sentence and one which followed it. Each item appeared in the first version of the text in either garden path or non-garden path form. Non-garden path sentences were disambiguated with commas. In the second (changed, signaled by →) version of each text, an it was added either immediately following the subordinate verb (it_NP) or following the relative clause modifier of the ambiguous NP (NP_it) (cf. Christianson et al. 2001; Ferreira and Henderson 1991). The pre- and post-change conditions are illustrated in (5). (5) a. The country roads were rutted and very dangerous. While Rick drove the car that was red and dusty veered into a ditch. Fortunately, no one was injured in the accident (garden path). →

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The country roads were rutted and very dangerous. While Rick drove it the car that was red and dusty veered into a ditch. Fortunately, no one was injured in the accident (it_NP). OR The country roads were rutted and very dangerous. While Rick drove the car that was red and dusty it veered into a ditch. Fortunately, no one was injured in the accident (NP_it). b. The country roads were rutted and very dangerous. While Rick drove, the car that was red and dusty veered into a ditch. Fortunately, no one was injured in the accident (non-garden path). → The country roads were rutted and very dangerous. While Rick drove it, the car that was red and dusty veered into a ditch. Fortunately, no one was injured in the accident (it_NP). OR The country roads were rutted and very dangerous. While Rick drove the car that was red and dusty, it veered into a ditch. Fortunately, no one was injured in the accident (NP_it). The experimental items were thus crossed in a 2 (syntactic status of the pre-change version) ×2 (order of it and NP in the changed version) design and distributed among four experimental lists in a Latin Square. The order of experimental items on each list was quasirandomized such that at least one filler item intervened between experimental items. There were 92 filler items on each list, which also consisted of three-sentence texts. Many of these shared similar characteristics with the experimental items (beginning with While, multiple clauses, containing names, etc.). Slightly more than half of the post-change filler items contained no changes; the slightly fewer than half that did contained changes in punctuation, lexical changes, changes in tense, additions or deletions of short words, and changes in word order. Approximately half the total 128 items thus contained changes in the post-change version, and approximately half did not. Participants Thirty-six participants from the University of Illinois at Urbana-Champaign community participated in the experiment. They were compensated with course credit or $7. All were native speakers of American English. Procedure Presentation of the pre- and post-change versions of the texts was programmed on E-Prime 1.1 experiment design software and run on a Dell microcomputer. Participants were seated in front of the computer’s CRT display monitor with a dedicated Psychology Software Tools five-button response box. First, informed consent was given by participants. Participants then read on-screen instructions for the main experiment, were allowed to ask questions, and then were presented with six practice items. In the actual experiment, participants read silently the pre-change texts at a normal pace with no time limit. The pre-changed text was presented in the center of the screen in Times New Roman font. When finished, they pressed the center button on the button box to view the post-change text, which was presented in the same size in Arial font. The somewhat wider Arial font produced an apparent lengthening

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of post-change texts compared to pre-change texts, even when no words were added in the change (Sanford et al. 2005). Participants then silently read the second text and reported to a research assistant what, if any, change(s) they had noticed. The research assistant had a list of all experimental and filler items for each participant’s session, and made hand-written notes of the reported changes. A coding system was devised for major change types, including “addition,” “deletion,” and “changed word” in order to establish consistency between the records kept by each of the three research assistants who ran participants. After reporting any change(s), the participant pressed the middle button again to proceed to the next item. Sessions lasted 70–90 min on average.

Results Detection Accuracy ANOVAs were performed on the results of the detection reports, with one analysis treating participants as a random factor (F1) and one treating items as a random factor (F2). Sentence form (garden path or non-garden path) in the pre-change text and order of constituents in the post-change text (it_NP or NP_it) were within-subject/item factors. List was included as a between-participants factor and list condition as a between items factor in the participant and item analyses, respectively, to account for random variance associated with list order (Pollatsek and Well 1995). The dependent variable was the proportion of trials on which the participants detected the precise change affected in the second version of the text, e.g., “An ‘it’ was added after ‘drove”’ or “. . .was added here” (pointing). Results of the analysis by participants, i.e., mean proportion of trials in which changes were correctly detected, are reported in Table 1. Analysis revealed a significant main effect of pre-change sentence structure: F1(1, 35) = 15.48, M S E = .04, p < .001; F2(1,35) = 20.57, M S E = .03, p < .001. Changes to garden path sentences were more accurately detected than changes to non-garden paths. There was also a main effect of post-change constituent order: F1(1, 35) = 48.07, M S E = .06, p < .001; F2(1, 35) = 91.92, M S E = .03, p < .001. The addition of the pronoun it was detected far more often when it occurred before the NP (it_NP, or cataphora) compared to after the NP (NP_it, or anaphora). The interaction of pre-change sentence type and post-change constituent order was significant by participants and nearly so by items: F1(1, 35) = 4.34, M S E = .02, p = .045; F2(1, 35) = 4.02, M S E = .03, p = .054. The increase in detection rate for the added cataphoric (it_NP) it over detection rate for the added anaphoric (NP_it) it was less dramatic in the garden path condition than it was in the non-garden path condition. We return to this result in the Discussion.

Table 1 Proportion of accurate change detection and errors (false alarms) in Experiment 1 (Standard deviation in parentheses)

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Post-change constituent order

it_NP

NP_it

Pre-change sentence Garden path Errors Non-garden path Errors

0.70 (0.27) 0.13 (0.13) 0.62 (0.30) 0.23 (0.20)

0.48 (0.33) 0.12 (0.12) 0.29 (0.28) 0.43 (0.29)


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Error Rate ANOVAs were also performed on error data, analyzing mean proportion of errors in each condition. Errors were defined as false alarms, i.e., reports of changes that had not occurred. Analysis revealed a main effect of pre-change sentence structure: F1(1, 35) = 31.20, M S E = .05, p < .001; F2(1, 35) = 81.65, M S E = .02, p < .001. A main effect of post-change constituent order was also observed: F1(1, 35) = 11.18, M S E = .03, p = .002; F2(1, 35) = 17.53, M S E = .02, p < .001. These main effects were qualified by an interaction: F1(1, 35) = 13.70, M S E = .02, p = .001; F2(1, 35) = 15.67, M S E = .02, p < .001, which was characterized by almost identically low error rates in the garden path conditions irrespective of post-change constituent order. In the non-garden path conditions, however, the error rate in the post-change anaphoric condition (NP_it) was almost double that in the cataphoric condition (it_NP). Reading Time Because reading times of the post-change texts included reporting time, which was in principle unlimited (participants pressed the continue button after reporting any changes), analyses were performed only on reading times of the pre-change texts. Paired sample t-tests (twotailed) were performed on reading times of garden path (M = 12.4 s) and non-garden path (M = 12.3 s) pre-change texts. The comparison yielded no significant difference between the two text types ( ps > .2). Correlation Analyses A post-hoc Pearson correlation analysis was conducted to determine if change detection was simply a function of reading time on the pre-change text. This analysis revealed a significant positive correlation of r = .38 between reading time of garden path texts and it-detection in the cataphoric (it_NP) post-change texts ( p = .02), but not in the anaphoric (NP_it) post-change texts ( p = .17). The analysis also revealed the opposite pattern of correlations in the non-garden path conditions. Here the correlation between pre-text reading time and detection in the cataphoric (it_NP) condition was not significant ( p = .23), but the positive correlation in the anaphoric (NP_it) condition of r = .49 was significant ( p = .002). Discussion A text-change paradigm was employed to look for evidence of good enough language processing at the syntactic level. Specifically, if partial reanalysis does occur when one is confronted with garden path sentences such as (2), then the resulting syntactic representation could be characterized as a “spliced” tree, in which a phonologically empty syntactic node lingers in the direct object position of the subordinate verb after the ambiguous NP is stolen by the matrix clause (Fodor and Inoue 1998). It was hypothesized that adding an it in the subordinate direct object position would be difficult to detect, because doing so would agree with the underlying partially unreanalyzed structure. The strongest possible evidence for good enough processing and the description of Fodor & Inoue’s (1998) Attach Anyway model of reanalysis would have been a result in which participants were least sensitive to additions of it in the garden path it_NP condition. As can be seen in Table 1, however, this was the condition in which people most accurately identified the text change. In fact, participants were far more accurate in their responses in

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garden path conditions than in non-garden path conditions, as observed in both detection accuracy and error rates. This is actually an important result, as data supporting good enough sentence processing (e.g., Christianson et al. 2001, 2006) could potentially be explained away as due to a general insensitivity to temporary ambiguities, i.e., people just miss them. Participants’ considerable sensitivity to changes in the conditions here, however, suggests that relatively more attention is devoted to garden path structures, though more reading time was not allocated for garden path texts. The subtle yet significant interaction of pre-change structure and post-change constituent order is important, as it is consistent with a weaker prediction of good enough processing in this particular task. Although it was generally easy to spot the it when it was added to garden path texts immediately following the subordinate verb, this ease of detection is in some sense unsurprising: Adding an it in this position produced a cataphoric structure (it_NP), which is both more infrequent and harder to process than anaphoric structures (Petrovitz 1996; see also the reading times in Experiment 2, below), so it may have jumped out at participants. Support for a strong effect of cataphora in the it_NP conditions is also found in the error data. Errors, i.e., false alarms, in anaphoric (NP_it) non-garden path sentences were almost double those in cataphoric (it_NP) non-garden paths. In other words, cataphoric changes were apparently quite obvious in non-garden paths; absent this clear error signal in the anaphoric (NP_it) condition, false alarms proliferated. In the garden path condition, when it was added in precisely the position in which an empty, unreanalyzed object NP node may exist, it was not as noticeable as one would expect given the significantly larger difference between the cataphoric and anaphoric changes in the non-garden path condition. Also, in garden path conditions, there was practically no difference in error rates, suggesting that the cataphoric (it_NP) it did not jump out at participants any more than the anaphoric (NP_it) it, and, absent this clear signal of change, false alarms were relatively equally distributed in the two sentence types. Finally, the significant correlations between reading time and error detection are also consistent with good enough processing. In the garden path condition, reading times were correlated positively with higher detection rates in the cataphoric condition (it_NP). This is precisely what would be predicted if we assume that, in order to spot the added it in this position, full reanalysis would need to be performed. This full reanalysis would naturally be expected to increase reading time. Interestingly, the opposite pattern surfaced in the nongarden path condition, where longer reading times were correlated with higher detection rates in the anaphoric condition (NP_it). The cause of this reversal is not immediately apparent, but it is clear that change detection accuracy was not purely a function of the time spent reading the pre-change text.

Experiment 2 Experiment 2 again employed the text-change paradigm, but this time, the change was a deletion of it in the post-change text (6). The reasoning behind this manipulation is as follows: Previously, it had been hypothesized that a direct object appears in the initial, ultimately incorrect parse of a garden path sentence, and that partial or good enough reanalysis may leave that position unreanalyzed syntactically. If this is correct, then removing an overt, semantically underspecified object (it) from an originally non-garden path sentence should make the resultant garden path structure even more resistant to revision. In other words, participants should be relatively poor at noticing changes even when the pre-change sentence contains a cataphor (it_NP) and the post-change sentence is a garden path, despite the fact

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that both of these types of sentences appeared to increase detection rates and reading times in Experiment 1. The specific predicted results are: (1) The deletion of it should eliminate the cataphoric penalty in the garden path condition observed in Experiment 1. The cataphoric penalty should be balanced out by the “cover” of the perseverant structure, primed by the prechange text, and thus be more likely to be processed post-change in a good enough fashion; (2) The difference between garden path and non-garden path conditions should disappear in the it_NP condition, where perseverant structure should mask the deletion of a clause-final it, with or without a comma present. Method Materials Materials were identical to those in Experiment 1, except that the text change involved deleting it, rather than adding it, as exemplified in (6). (6) a. The country roads were rutted and very dangerous. While Rick drove it the car that was red and dusty veered into a ditch. Fortunately, no one was injured in the accident (it_NP). OR The country roads were rutted and very dangerous. While Rick drove the car that was red and dusty it veered into a ditch. Fortunately, no one was injured in the accident (NP_it). → The country roads were rutted and very dangerous. While Rick drove the car that was red and dusty veered into a ditch. Fortunately, no one was injured in the accident (garden path). b. The country roads were rutted and very dangerous. While Rick drove it, the car that was red and dusty veered into a ditch. Fortunately, no one was injured in the accident (it_NP). OR The country roads were rutted and very dangerous. While Rick drove the car that was red and dusty, it veered into a ditch. Fortunately, no one was injured in the accident (NP_it). → The country roads were rutted and very dangerous. While Rick drove, the car that was red and dusty veered into a ditch. Fortunately, no one was injured in the accident (non-garden path). Participants Thirty-six participants from the University of Illinois at Urbana-Champaign community participated in the experiment. They were compensated with course credit or $7. All were native speakers of American English, and none had participated in Experiment 1. Procedure The procedure was identical to that in Experiment 1.

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400 Table 2 Proportion of accurate change detection and errors (false alarms) in Experiment 2 (Standard deviation in parentheses)

J Psycholinguist Res (2008) 37:391–403 Post-change sentence

Garden path

Non-garden path

Pre-change constituent order it_NP Errors NP_it Errors

0.45 (0.32) 0.15 (0.15) 0.43 (0.33) 0.13 (0.14)

0.46 (0.30) 0.20 (0.20) 0.18 (0.24) 0.58 (0.27)

Results Detection Accuracy ANOVAs were performed on the results of the detection reports, with one analysis treating participants as a random factor (F1) and one treating items as a random factor (F2). Constituent order (it_NP or NP_it) in the pre-change text and sentence structure in the post-change text (GP or non-GP) were within-subject/item factors. List was again included as a betweenparticipants factor in the participant analysis, as was list condition in the item analysis. The dependent variable was the proportion of trials on which the participants detected the change in the second version of the text (see Experiment 1). Results of the analysis by participants are reported in Table 2. Analysis revealed a significant main effect of pre-change constituent order: F1(1, 35) = 14.10, M S E = .06, p = .001; F2(1, 35) = 18.07, M S E = .05, p < .001. There was also a main effect of post-change sentence type: F1(1, 35) = 14.46, M S E = .04, p = .001; F2(1, 35) = 17.08, M S E = .03, p < .001. The main effects were qualified by a reliable interaction of pre-change constituent order and post-change sentence type: F1(1, 35) = 38.49, M S E = .02, p < .001; F2(1, 35) = 23.40, M S E = .02, p < .001. The interaction was characterized by nearly identical accuracy in garden path and non-garden path conditions in the cataphoric (it_NP) condition, and nearly identical accuracy in both cataphoric and anaphoric (NP_it) conditions in the garden path condition, as predicted.

Error Rate ANOVAs were also performed on error data, analyzing mean proportion of errors, i.e., false alarms, in each condition. Analysis revealed a significant main effect of pre-change constituent order: F1(1, 35) = 28.03, M S E = .04, p < .001; F2(1, 35) = 70.85, M S E = .01, p < .001, and a main effect of post-change sentence structure: F1(1, 35) = 64.35, M S E = .04, p < .001; F2(1, 35) = 86.13, M S E = .02, p < .001. These main effects were qualified by a significant interaction: F1(1, 35) = 42.15, M S E = .03, p < .001; F2(1, 35) = 53.01, M S E = .02, p < .001. The interaction was characterized by almost identically low error rates in the garden path conditions, irrespective of pre-change constituent order. While the error rate in the cataphoric (it_NP) condition rose only slightly from the garden path to non-garden path condition, the error rate in the anaphoric (NP_it) condition quadrupled. The overall pattern of error rates here was similar to the situation in Experiment 1, with conditions in which detection proved more difficult yielding higher error rates.

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Reading Time Because reading times of the post-change texts again included reporting time, analyses were performed only on reading times of the pre-change texts. Paired samples t-tests (two-tailed) were performed on reading times of cataphoric and anaphoric pre-change texts. The comparison yielded the expected result, namely, that texts containing cataphoric sentences were read more slowly (M = 13.0 s) than those containing anaphoric sentences (M = 12.5 s): t1(1, 35) = 2.91, p = .006; t2(1, 35) = 2.32, p = .027. A post-hoc Pearson correlation analysis was conducted as in Experiment 1. This analysis revealed no significant correlations (all ps > .6). Importantly, longer reading times in the cataphoric (it_NP) condition did not lead to better change detection rates. Discussion In Experiment 2, the changes that were made to the initial text consisted of deleting it from positions corresponding to the positions in which it had been added in Experiment 1. It was reasoned that deleting the overt direct object it immediately following the subordinate verb would leave behind the syntactic structure that is hypothesized to exist in cases of partial, good enough, reanalysis. Furthermore, priming this structure was predicted to make it particularly difficult to reanalyze upon reading the changed text and thus difficult to detect the deletion. The results confirmed this prediction. In the pre-change anaphoric (NP_it) condition, the deletion of it was significantly more difficult to detect in the post-change non-garden path texts than in the garden path texts. But in the post-change garden path texts, there was no significant difference between anaphoric (NP_it) and cataphoric (it_NP) pre-change constituent orders. These results have two main implications. First, the relative subtlety of the key interaction in Experiment 1 was plausibly due in part to the large effect of cataphora, the strength of which may have overwhelmed the interaction. When it was added to garden path sentences in Experiment 1, resulting in a cataphoric (it_NP) structure, the change was simply too easy to detect due to the infrequency or processing difficulty associated with cataphora; perhaps cataphora in sentences such as this is borderline infelicitous according to general givenness contraints (Petrovitz 1996).1 Longer reading times on cataphoric texts in Experiment 2 are taken to support this interpretation. Nevertheless, the interaction that did emerge in Experiment 1 represents a small but significant number of trials in which the underlying partially reanalyzed “spliced” tree masked the addition of the it in the position of the hypothesized empty direct object node. Second, the fact that the detection of it-deletion resulting in garden path sentences was no easier than the detection of it-deletion in post-change non-garden path sentences also supports the partial reanalysis conclusion of Christianson et al. (2001). In the anaphoric (NP_it) conditions, there was a large difference in detection rates between garden path and non-garden path conditions. If the effects obtained here were attributable solely to inferential processes, one would expect the anaphoric pre-change conditions to not differ as a function of post-change structure. It appears, however, that structural reconfiguration is occurring, triggered by the deletion of the it. It should also be pointed out that it would be difficult to attribute the pattern of results in Experiment 2 to differing quantities of changes in certain conditions. For example, the change in the cataphoric (it_NP) pre-change text in the non-garden path condition entailed simply the deletion of it, whereas the change in the anaphoric (NP_it) counterpart text entailed 1 One potential way to lessen the cataphoric effect on change detection would be to construct texts in which,

e.g., the car in (5) is not a new discourse entity (Petrovitz 1996).

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both the deletion of it and the migration of the comma from after dusty (6b) to after drove. Nevertheless, a far lower detection rate was obtained in the condition where two changes were performed.2 The reason for participants’ relative failure to notice the change in this condition is hypothesized to be unrelated to good enough reasons: it is the only condition with no extenuating circumstances associated with it—no cataphora and no resultant garden path. The significant difference between detection rate in the garden path versus non-garden path NP_it conditions suggests that good enough processing does not stem from a general inattentiveness to test materials.

General Discussion The two experiments presented here employed a text-change paradigm to explore the existence of perseverant syntactic structure of the sort hypothesized to result as the output of good enough syntactic processing. Methodologically speaking, the experiments were successful in demonstrating that the text-change paradigm is useful in the syntactic as well as the semantic realm (Sanford et al. 2005; Sturt et al. 2004). With respect to good-enough processing, the accuracy, reading time, and error data pointed toward syntactic reanalysis of the stimuli and a small but significant degree of insensitivity to changes that were consistent with a lingering “tree-spliced” structure, which is hypothesized to result from the incomplete reanalysis of some garden path sentences. Acknowledgements The author thanks the members of the Educational Psychology Psycholinguistics Lab at the Beckman Institute, University of Illinois, Urbana-Champaign, especially Kent Lee, Ji Kim, Steve Luke, and Jung Hyun Lim for assistance in running the experiments. Thanks also to the audience at the 48th Annual Meeting of the Psychonomics Society in Houston, where some of the results were first presented. This research was funded in part by a UIUC Campus Research Board grant to the author. Any errors are solely the author’s responsibility. Author contact: Kiel Christianson, Department of Educational Psychology, University of Illinois, .

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