Many comprehension theories assert that increasing the distance between elements participating in a linguistic relation (e.g., a verb and a noun phrase argument) increases the difficulty of establishing that relation during on-line comprehension. Such locality effects are expected to increase reading times and are thought to reveal properties and limitations of the short-term memory system that supports comprehension. Despite their theoretical importance and putative ubiquity, however, evidence for on-line locality effects is quite narrow linguistically and methodologically: It is restricted almost exclusively to self-paced reading of complex structures involving a particular class of syntactic relation. We present 4 experiments (2 self-paced reading and 2 eyetracking experiments) that demonstrate locality effects in the course of establishing subject-verb dependencies; locality effects are seen even in materials that can be read quickly and easily. These locality effects are observable in the earliest possible eye-movement measures and are of much shorter duration than previously reported effects. To account for the observed empirical patterns, we outline a processing model of the adaptive control of button pressing and eye movements. This model makes progress toward the goal of eliminating linking assumptions between memory constructs and empirical measures in favor of explicit theories of the coordinated control of motor responses and parsing.

Eye fixation durations during normal reading correlate with processing difficulty, but the specific cognitive mechanisms reflected in these measures are not well understood. This study finds support in German readers' eye fixations for two distinct difficulty metrics: surprisal, which reflects the change in probabilities across syntactic analyses as new words are integrated; and retrieval, which quantifies comprehension difficulty in terms of working memory constraints.We examine the predictions of both metrics using a family of dependency parsers indexed by an upper limit on the number of candidate syntactic analyses they retain at successive words. Surprisal models all fixation measures and regression probability. By contrast, retrieval does not model any measure in serial processing. As more candidate analyses are considered in parallel at each word, retrieval can account for the same measures as surprisal. This pattern suggests an important role for ranked parallelism in theories of sentence comprehension.

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While it is widely acknowledged in the formal semantic literature that both the truth-functional focus particle only and it-clefts convey exhaustiveness, the nature and source of exhaustiveness effects with it-clefts remain contested. Based on an event-related brain potentials (ERPs) study on only-foci and it-clefts, we provide experimental evidence that the violation or cancelation of exhaustive readings involve different underlying processes in the two structural environments.

Background: In addition to the canonical subject-verb-object (SVO) word order, German also allows for non-canonical order (OVS), and the case-marking system supports thematic role interpretation. Previous eye-tracking studies (Kamide et al., 2003; Knoeferle, 2007) have shown that unambiguous case information in non-canonical sentences is processed incrementally. For individuals with agrammatic aphasia, comprehension of non-canonical sentences is at chance level (Burchert et al., 2003). The trace deletion hypothesis (Grodzinsky 1995, 2000) claims that this is due to structural impairments in syntactic representations, which force the individual with aphasia (IWA) to apply a guessing strategy. However, recent studies investigating online sentence processing in aphasia (Caplan et al., 2007; Dickey et al., 2007) found that divergences exist in IWAs' sentence-processing routines depending on whether they comprehended non-canonical sentences correctly or not, pointing rather to a processing deficit explanation. Aims: The aim of the current study was to investigate agrammatic IWAs' online and offline sentence comprehension simultaneously in order to reveal what online sentence-processing strategies they rely on and how these differ from controls' processing routines. We further asked whether IWAs' offline chance performance for non-canonical sentences does indeed result from guessing. Methods & Procedures: We used the visual-world paradigm and measured eye movements (as an index of online sentence processing) of controls (N = 8) and individuals with aphasia (N = 7) during a sentence-picture matching task. Additional offline measures were accuracy and reaction times. Outcomes & Results: While the offline accuracy results corresponded to the pattern predicted by the TDH, IWAs' eye movements revealed systematic differences depending on the response accuracy. Conclusions: These findings constitute evidence against attributing IWAs' chance performance for non-canonical structures to mere guessing. Instead, our results support processing deficit explanations and characterise the agrammatic parser as deterministic and inefficient: it is slowed down, affected by intermittent deficiencies in performing syntactic operations, and fails to compute reanalysis even when one is detected.

Three experiments (self-paced reading, eyetracking and an ERP study) show that in relative clauses, increasing the distance be tween the relativized noun and the relative-clause verb makes it more difficult to process the relative-clause verb (the so-called locality effect). This result is consistent with the predictions of several theories (Gibson 2000, Lewis and Vasishth 2005), and contradicts the recent claim (Levy 2008) that in relative-clause structures increasing argument-verb distance makes processing easier at the verb. Levy's expectation-based account predicts that the expectation for a verb becomes sharper as dis- tance is increased and therefore processing becomes easier at the verb. We argue that, in addition to expectation effects (which are seen in the eyetracking study in first-pass regression probability), processing load also increases with increasing distance. This contradicts Levy's claim that heightened expectation leads to lower processing cost. Dependency- resolution cost and expectation-based facilitation are jointly responsible for determining processing cost.

Two Hindi eyetracking studies show that clefting a noun results in greater processing difficulty initially, due to the extra processing steps involved in encoding a clefted noun (e.g., for computing the exhaustiveness interpretation). However, this extra difficulty in encoding a clefted noun results in a processing advantage when the clefted noun needs to be retrieved later on in the sentence - the clefted noun is retrieved faster in subsequent processing compared to its non-clefted counterpart. This effect is short-lived, however; it does not last beyond the current sentence. We also show that given-new ordering yields a processing advantage over new-given order, but this is only seen after the whole sentence is processed, i.e., it is a late effect that occurs after syntactic processing is completed. Finally, following up on work on German by Hoernig et al. (2005), we present evidence that non-canonical order can be processed more easily than canonical order given appropriate context.

What theories best characterize the parsing processes triggered upon encountering ambiguity, and what effects do these processes have on eye movement patterns? An eye-tracking study involving adjunct attachment ambiguities in Spanish showed that although conventional dependent measures favored the unrestricted race model, when we additionally took eye-movement patterns into account, the evidence was consistent only with the good-enough theory of parsing.A scanpath analysis further showed that rereading occurred more often in high working-memory capacity participants, which verifies a surprising prediction of the good-enough parsing account: high-capacity participants tend to commit to a parse more often than low-capacity participants, leading to more errors and a greater need to reanalyze. These findings also have broader implications for models of reading processes: Late regressive eye movements triggered in response to disambiguation suggest that the coupling of the eye and parser may not be as tight as assumed in current computational models of reading.

Which repair strategy does the language system deploy when it gets garden-pathed and what can regressive eye movements in reading tell us about reanalysis strategies? Several influential eye-tracking studies on syntactic reanalysis (Frazier & Rayner 1982, Meseguer et al 2002, Mitchell et al 2008) have examined scanpaths-sequences of eye fixations-to answer this question. However, in the absence of a suitable method for analyzing scanpaths, these studies relied on simplified dependent measures that are arguably ambiguous and hard to interpret. We address the theoretical question of repair strategy by developing a new method that quantifies scanpath similarity. Our method reveals several distinct fixation strategies associated with reanalysis that went undetected in a previously published data set (Meseguer et al 2002). One prevalent pattern suggests re-parsing of the sentence, a strategy that has been proposed in the literature (Frazier & Rayner 1982); however, readers differed tremendously in how they orchestrated the various fixation strategies. Our results raise the possibility that the human parsing system non-deterministically adopts different strategies when confronted with the need to reanalyze.