". . . the reactivation of prior referents is restricted by grammatical constraints. In the case where such information does not sufficiently constrain the list of potential antecedents to a single one, the pragmatic and other sentence/discourse processing procedures undoubtedly come into play, but, given the present evidence, only at a later point in processing."

(Nicol and Swinney, 1989, p.18)

While the lack of interference from an inaccessible antecedent seems to imply that binding conditions are applied before other cues such as gender features are recruited, there is as yet no firm evidence that discourse cues, for example, are systematically withheld relative to binding constraints in the time-course of pronoun resolution. Given that discourse cues are increasingly found to act early and even predictively (e.g., Koornneef and Van Berkum, 2006; Cozjin et al., 2011), further research on the interaction between condition B and the discourse status of antecedents would be welcome, to confirm or disconfirm a strict ordering of constraint application.

In addition, any model of the retrieval process should be able to incorporate the profiles of both native and non-native comprehenders. As far as the L2 processing is concerned, the current study shows that the processing of pronouns may be driven by a search for a salient subject, rather than making use of a detailed structural analysis to distinguish condition B and SDP environments; this is not the case for L1 processing. This demonstrates a different sensitivity to structural cues in the two populations; generalizing a retrieval or processing model so that it applies equally well to L1 and L2 pronoun resolution could perhaps be achieved by assigning differing constraint weights in different populations.

#### **CONCLUSION**

Native English speakers appear to successfully apply condition B online so that they do not consider an inaccessible antecedent at any point during processing, which is in line with the BAIF hypothesis. They are also sensitive to syntactic cues that distinguish syntactic environments that either require, or do not require, the exclusion of a local referent. By contrast, non-native speakers do not appear to distinguish condition B environments from SDP environments online, appearing to opt for salient subject antecedents in both despite offline awareness of the difference. The different processing profiles of native and non-native speakers must be incorporated into models of retrieval, with particular reference to the relative importance of structural cues for different populations.

11Note that in order to draw any meaningful conclusions about possible L1 transfer, learner groups from different L1 backgrounds would need to be compared.

### **ACKNOWLEDGMENTS**

Part of this research was completed as part of Clare Patterson's PhD dissertation at the University of Potsdam. She was supported by an ESRC postgraduate studentship awarded by the Department of Language and Linguistics at the University of Essex, and by an Alexander-von-Humboldt-Professorship to Prof. Harald Clahsen (Potsdam Research Institute for Multilingualism), which is gratefully acknowledged.

#### **REFERENCES**

**Conflict of Interest Statement:** The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.

*Received: 15 October 2013; accepted: 05 February 2014; published online: 25 February 2014.*

*Citation: Patterson C, Trompelt H and Felser C (2014) The online application of binding condition B in native and non-native pronoun resolution. Front. Psychol. 5:147. doi: 10.3389/fpsyg.2014.00147*

*This article was submitted to Language Sciences, a section of the journal Frontiers in Psychology.*

*Copyright © 2014 Patterson, Trompelt and Felser. This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) or licensor are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.*

# Structural constraints on pronoun binding and coreference: evidence from eye movements during reading

Ian Cunnings 1 \*, Clare Patterson2 and Claudia Felser 2

*1 School of Psychology and Clinical Language Sciences, University of Reading, Reading, UK, 2 Potsdam Research Institute for Multilingualism, University of Potsdam, Potsdam, Germany*

A number of recent studies have investigated how syntactic and non-syntactic constraints combine to cue memory retrieval during anaphora resolution. In this paper we investigate how syntactic constraints and gender congruence interact to guide memory retrieval during the resolution of subject pronouns. Subject pronouns are always technically ambiguous, and the application of syntactic constraints on their interpretation depends on properties of the antecedent that is to be retrieved. While pronouns can freely corefer with non-quantified referential antecedents, linking a pronoun to a quantified antecedent is only possible in certain syntactic configurations via variable binding. We report the results from a judgment task and three online reading comprehension experiments investigating pronoun resolution with quantified and non-quantified antecedents. Results from both the judgment task and participants' eye movements during reading indicate that comprehenders freely allow pronouns to corefer with non-quantified antecedents, but that retrieval of quantified antecedents is restricted to specific syntactic environments. We interpret our findings as indicating that syntactic constraints constitute highly weighted cues to memory retrieval during anaphora resolution.

#### Edited by:

*Charles Jr. Clifton, University of Massachusetts Amherst, USA*

#### Reviewed by:

*Dave Kush, Haskins Laboratories, USA Roger P. G. Van Gompel, University of Dundee, UK*

#### \*Correspondence:

*Ian Cunnings, School of Psychology and Clinical Language Sciences, University of Reading, Earley Gate, Reading RG6 7BE, UK<EMAIL_ADDRESS>
#### Specialty section:

*This article was submitted to Language Sciences, a section of the journal Frontiers in Psychology*

Received: *16 February 2015* Accepted: *03 June 2015* Published: *23 June 2015*

#### Citation:

*Cunnings I, Patterson C and Felser C (2015) Structural constraints on pronoun binding and coreference: evidence from eye movements during reading. Front. Psychol. 6:840. doi: 10.3389/fpsyg.2015.00840* Keywords: pronoun resolution, memory retrieval, quantification, eye movements, reading, English

### Introduction

The successful interpretation of anaphoric elements during language comprehension involves forming dependencies between constituents that may span several words or sentences. Anaphora resolution thus provides a key test case for studying the memory system that subserves language comprehension, as the correct interpretation of anaphoric constituents crucially relies on the retrieval of a particular item, the antecedent, from memory. A growing number of studies have investigated how syntactic and non-syntactic factors combine to cue the retrieval of an antecedent during the resolution of different types of anaphora (Badecker and Straub, 2002; Sturt, 2003; Xiang et al., 2009; Clackson et al., 2011; Cunnings and Felser, 2013; Dillon et al., 2013; Chow et al., 2014; Clackson and Heyer, 2014; Cunnings and Sturt, 2014; Patterson et al., 2014). Most previous research has investigated constraints on the resolution of reflexives and object pronouns, where syntactic constraints (e.g., binding conditions A and B; Chomsky, 1981) restrict memory retrieval to an antecedent in a particular syntactic domain. Research on real-time pronoun resolution has investigated the extent to which such syntactic constraints interact with other sources of information, such as discourse prominence and gender/number congruence, to guide the retrieval of a particular antecedent. While some have claimed that syntactic constraints act as "hard constraints" that restrict memory retrieval to syntactically licit antecedents (e.g., Dillon et al., 2013; Chow et al., 2014), others argue that syntactic constraints are violable and interact with other sources of information to cue antecedent retrieval (e.g., Badecker and Straub, 2002).

While binding conditions A and B have been well studied, to date little research has investigated the time-course of the application of syntactic constraints on the interpretation of pronouns linked to quantified and non-quantified antecedents as in (1) and (2) respectively.

In (1a), the subject pronoun he can refer to either the matrix subject the man or the quantified antecedent every boy. In (1b) however, when every boy appears inside a relative clause, it is not possible for the pronoun to be bound by it. Note that this is not an absolute restriction on antecedents inside relative clauses however, as the pronoun can freely refer to the non-quantified antecedent the boy in both (2a) and (2b). This contrast between quantified and non-quantified antecedents thus provides a particular challenge for memory retrieval mechanisms during language processing. For example, if retrieval operations disfavored antecedents inside relative clauses this would ensure that syntactically illicit quantified antecedents, as in (1b), are not retrieved, but would also rule out perfectly licit nonquantified antecedents as in (2b). Conversely, if subject pronouns routinely trigger retrieval of antecedents inside relative clauses, syntactically illicit quantified antecedents may be retrieved. Instead, successful pronoun interpretation requires selective retrieval of antecedents inside relative clauses, but this is dependent on the properties of the to-be-retrieved material.

The aim of the current study was to investigate the retrieval of quantified and non-quantified antecedents during pronoun resolution to further examine how syntactic constraints on memory retrieval are implemented during real-time anaphora resolution. To this end, we conducted an offline judgment task and three online reading experiments investigating pronoun resolution with quantified and non-quantified antecedents. We begin below by discussing theoretical accounts of the contrast between quantified and non-quantified antecedents as exemplified in (1) and (2), before discussing implications of this contrast for models of memory retrieval during language processing in more detail.

### Background

### Variable Binding and Coreference Assignment

In linguistic theory, it has been claimed that pronoun resolution can be achieved in different ways. Although theoretical accounts differ in their precise nature, a core idea is that pronouns can be resolved either in the discourse representation, via coreference assignment, or in logical syntax, via variable binding (e.g., Evans, 1980; Bosch, 1983; Reinhart, 1983; Reuland, 2001, 2011). Coreference assignment involves linking a pronoun to a referential antecedent in the discourse, as in the case of linking the pronoun he to either of the antecedents (the man or the boy) in (2). Quantified phrases (QPs), as in (1), however do not refer to a single individual in the discourse, and a pronoun linked to a QP co-varies in interpretation with the quantifier. Pronouns linked to QPs are thus said to involve variable binding rather than coreference assignment.

A long-standing observation in the linguistics literature is that variable binding is only possible in certain syntactic configurations. This restriction has traditionally been characterized in terms of c-command. C-command refers to a relationship between constituents in the phrase structure representation of a sentence based on the notion of hierarchical dominance. In the standard definition, a constituent c-commands its sister constituents and any constituents that these dominate (Reinhart, 1983). Variable binding is only possible between a pronoun and an antecedent that c-commands it (see e.g., Reuland, 2001, 2011). As such, in (3a), when the QP every boy c-commands the pronoun, the pronoun can be bound by it, while in (3b), when the QP does not c-command the pronoun, variable binding between the pronoun and QP is not possible. Coreference assignment to non-quantified determiner phrases (DPs) is not contingent on c-command however, and as such the pronoun can corefer with the referential antecedent the boy in both (2a) and (2b).

### Memory Retrieval during Language Processing

Recent psycholinguistic research has motivated a cue-based model of memory retrieval during language processing (McElree, 2000; McElree et al., 2003; Lewis et al., 2006). In cue-based content-addressable models, retrieval is achieved by matching a set of retrieval cues with the contents of all items in memory in parallel. The item in memory that provides the best match to these cues becomes most highly activated and will thus be retrieved. The distinction between variable binding and coreference assignment has a number of implications for models of memory retrieval during language processing.

One theoretical implication relates to how the c-command constraint on variable binding is implemented in contentaddressable memory. Content-addressable models are wellsuited to utilize feature-based cues that target intrinsic properties of to-be-retrieved material. For example, it is straightforward to implement a [+masculine] feature for masculine pronouns to cue retrieval of a masculine antecedent. However, the c-command constraint on variable binding may be more difficult to implement, as it involves access to information about the relation between two items in memory (the pronoun and antecedent), rather than accessing an intrinsic feature of the antecedent (for discussion, see Kush, 2013; Kush et al., 2015). The primary aim of the current study was to investigate if the c-command constraint on variable binding restricts antecedent retrieval, rather than the question of how it is implemented. We do however return to this issue in the General Discussion.

A second implication that the distinction between variable binding and coreference assignment has for models of memory retrieval during language processing relates to how pronouns that are ambiguous with regards to variable binding and coreference assignment are resolved. Research in theoretical linguistics has claimed that syntactic variable binding is preferred over coreference assignment. Reuland (2001, 2011), for example, proposed an economy principle which predicts that variable binding should be computed before coreference assignment is attempted (see also Koornneef, 2008). This predicts that variable binding antecedents should preferentially be retrieved before coreference antecedents. Cunnings et al. (2014) tested this prediction in two reading experiments. They manipulated gender congruence between a pronoun and two potential antecedents in the discourse, and monitored participants' eye-movements as they read sentences as in (3).

In their Experiment 1, exemplified in (3a), gender congruence was manipulated between the pronoun and a c-commanding QP (every soldier), and between the pronoun and a non c-commanding but linearly closer proper name coreference antecedent (James/Helen). They hypothesized that if variable binding is computed before coreference assignment, when participants encounter the pronoun, the c-commanding QP antecedent should be preferentially retrieved. In this case, the gender of the c-commanding QP should affect reading times at a point in time before the gender of the proper name. However, in contrast to this prediction, they observed that reading times at and shortly after the pronoun were longer when the pronoun mismatched in gender with the proper name antecedent, and were not significantly affected by the gender of the QP. This suggests that the proper name antecedent, rather than the QP, was preferentially retrieved upon encountering the pronoun. In their Experiment 2 however, exemplified in (3b), when the QP was linearly closer to the pronoun than the proper name antecedent, reading times at and shortly after the pronoun were reliably longer when the QP mismatched in gender with the pronoun. Together, these results indicate there is no overall preference for either variable binding or coreference assignment. For variable binding antecedents to be retrieved additional factors, such as antecedent recency, need to favor the QP antecedent.

A third issue relates to how the c-command constraint on variable binding, however it is implemented, interacts with other cues to antecedent retrieval. Cunnings et al. only investigated cases in which variable binding antecedents were syntactically licit, and did not test sentences containing QPs that did not ccommand the critical pronoun. A key prediction of cue-based models is similarity-based interference (see e.g., Lewis et al., 2006; Van Dyke and Johns, 2012). As retrieval involves the matching of a set of retrieval cues with all items in memory in parallel, a distractor item that partially matches the retrieval cues may sometimes be retrieved instead of the intended retrieval target. This leads to the possibility that a QP antecedent that does not c-command a pronoun may occasionally be retrieved even though this dependency is ungrammatical.

Attraction effects in subject-verb agreement are a key example of such interference effects during language processing. For example, Wagers et al. (2009) reported longer reading times for sentences containing ungrammatical compared to grammatical subject-verb agreement (e.g., the key to the cabinet was rusty vs. the key to the cabinet were rusty). This ungrammaticality effect was however reliably attenuated when the structurally illicit distractor matched the agreement marking of the critical verb (e.g., the key to the cabinets were rusty). This attraction effect provides good evidence that structural cues (e.g., [+phrasal head]) and agreement (e.g., [+plural]) are equally weighted cues that combine to guide retrieval during subject-verb agreement. When no item in memory fully matches the cues at retrieval, a partially matching distractor can sometimes be retrieved. We will refer to this pattern of results as facilitatory interference, as the processing of ungrammatical sentences is facilitated by a partially matching distractor.

Although facilitatory attraction effects are well attested for subject-verb agreement, a number of studies have failed to observe this specific pattern of interference during anaphora resolution (e.g., Sturt, 2003; Xiang et al., 2009; Dillon et al., 2013; Chow et al., 2014; Cunnings and Sturt, 2014). Sturt, for example, manipulated gender congruence between a reflexive and two antecedents in a piece of discourse (e.g., Jonathan/Jennifer remembered that the surgeon had pricked himself/herself with a used syringe needle) and observed that while first-pass reading times at the reflexive were reliably longer when the structurally licit antecedent the surgeon mismatched in stereotypical gender with the reflexive, the gender of the structurally illicit antecedent (Jonathan/Jennifer) did not affect reading times in this measure. Results such as these have led some to claim that while equally weighted syntactic and agreement cues combine to guide retrieval for subject-verb agreement, anaphora resolution is guided by syntactic "hard constraints" that restrict retrieval to syntactically licit antecedents (Dillon et al., 2013; Chow et al., 2014). Although the question of whether or not structurally illicit antecedents are always ignored during anaphora resolution is debated (e.g., Badecker and Straub, 2002; Cunnings and Felser, 2013; Clackson and Heyer, 2014), the contrast in attraction effects observed for agreement and anaphora suggests these dependencies implement agreement cues in different ways. For anaphora, syntactic constraints appear to be more strongly weighted cues to retrieval than gender/number congruence.

Syntactic constraints on reflexives could potentially be implemented as highly weighted cues that trigger retrieval of an antecedent within a particular syntactic domain (e.g., the same clause as the reflexive; see Dillon et al., 2013). However, constraints on quantified and non-quantified antecedents are difficult to implement in this way, as it is not the case that antecedents within a particular syntactic domain (e.g., a relative clause) are categorically ruled out. Rather, sensitivity to constraints on variable binding and coreference assignment require retrieval operations to be able to selectively retrieve antecedents that do not c-command pronouns depending on their quantificational status. The contrast between variable binding and coreference assignment thus provides a unique challenge to memory retrieval operations during language processing, which may leave variable binding more susceptible to facilitatory interference than has been observed for other types of anaphora, such as reflexives.

We are aware of only one study that has investigated the potential for facilitatory interference during the resolution of bound variable anaphora. Kush et al. (2015) recorded participants' eye-movements as they read sentences as in (4).

In (4a), the only syntactically licit antecedent for the pronoun her is the coreference antecedent the boy/girl. In (4b), the pronoun has no syntactically licit antecedent as the quantified phrase (no boy/girl) does not c-command it. Kush et al. hypothesized that if the pronoun triggers retrieval of the coreference antecedent in (4a), a gender mismatch effect should be observed, with longer reading times for gender mismatching (the boy) than gender matching (the girl) antecedents. If antecedent retrieval respects the c-command constraint, this contrast between gender matching (no girl scout) and gender mismatching (no boy scout) antecedents should not be observed in (4b). If the c-command constraint does not restrict antecedent retrieval however, Kush et al. hypothesized that the gender mismatch effect should be observed in both (4a) and (4b), as evidence of facilitatory interference. During first-pass processing at the pronoun Kush et al. observed a gender mismatch effect in (4a) but not (4b), suggesting the c-command constraint on variable binding restricts the early stages of antecedent retrieval. They did observe gender mismatch effects in (4c) however, when the quantified phrase c-commanded the pronoun. Kush et al interpreted these results as indicating that pronouns trigger retrieval of both c-commanding quantified phrases and non c-commanding coreference antecedents, but not non c-commanding quantified antecedents, suggesting that the c-command constraint restricts antecedent retrieval.

Against this background, the aim of the current study was to further investigate the implementation of the c-command constraint on variable binding during anaphora resolution. While Kush et al. compared antecedent retrieval for c-commanding and non c-commanding quantified antecedents in different sentence structures with different (subject and object) pronouns, we investigated variable binding and coreference resolution in maximally similar sentences with identical (subject) pronouns across four experiments. We also tested the universal quantifier every rather than the negative quantifier no. Together with the study reported by Kush et al., the current experiments provide a systematic examination of how constraints on retrieving quantified phrases and referential antecedents during anaphora resolution are implemented during language processing. Experiment 1 was an offline task that tested the extent to which naïve participants are sensitive to the c-command constraint on variable binding in an untimed task. Experiments 2–4 were online reading studies in which participants' eye-movements were monitored. Experiments 2–3 contrasted the retrieval of quantified and non-quantified referential antecedents in order to test the extent to which variable binding and coreference antecedents are retrieved in c-commanding and non c-commanding configurations. Experiment 4 tested the extent to which the c-command restriction on variable binding acts as a "hard constraint" on antecedent retrieval.

### Experiment 1

Experiment 1 used a sentence judgment paradigm to assess sensitivity to the c-command constraint on variable binding in an untimed offline task. The materials consisted of sentences as in (5), which manipulate the factor "c-command" to test whether participants are willing to link pronouns to QPs in different syntactic configurations.

(5a) C-commanding QP

The surgeon suggested that every man on the waiting list definitely realized that he needed some help.

(5b) Non c-commanding QP

The surgeon who every man on the waiting list suggested definitely realized that he needed some help.

In (5a), the QP every man c-commands the pronoun he and as such the pronoun can be bound by the QP via variable binding. In (5b) however, the QP appears inside a relative clause and as such does not c-command the pronoun. In this case, the pronoun can only refer to the matrix subject the surgeon. We expect native English speakers to be sensitive to the c-command constraint on variable binding in this offline task. That is, participants should consider the QP as a possible antecedent for the pronoun in (5a) but not (5b).

### Methods

#### Participants

32 native English speakers (17 males, mean age 21; range 18– 30) from the University of Edinburgh community either received course credit or a small payment for taking part in Experiment 11 . All participants in Experiment 1, and Experiments 2–4, provided written, informed consent before the experiment began. Ethical approval for all experiments was granted by the Department of Psychology Research Ethics Committee at the University of Edinburgh.

### Materials

Materials consisted of 16 experimental items constructed as in (5). In each item, the pronoun matched in definitional gender with the QP antecedent. The pronoun also always matched in stereotypical gender with the matrix subject to ensure that the texts were felicitous. The materials manipulated the factor "c-command" in two conditions, such that the QP either ccommanded or did not c-command the QP. A full list of experimental items is provided in Appendix A. In addition to the

1The participants in Experiment 1 also completed Experiment 3. All participants completed Experiment 3 before Experiment 1.

experimental items, 24 filler items were also constructed, some of which also contained pronouns but others which did not.

#### Procedure

The experimental and filler items were presented to participants as a questionnaire in Microsoft Word. A question appeared under each text with two possible answers. For the experimental items, the question always probed the interpretation of the pronoun. In (4), for example, the question was "Who does 'he' refer to?" with "(A) the surgeon" and "(B) every man" as possible answers. Participants provided a response by selecting one of five options from a drop-down menu that appeared beside each text. Possible responses were "(A) strongly preferred", "(A) mildly preferred", "(A) or (B) equally likely", "(B) mildly preferred" or "(B) strongly preferred". Across the 16 experimental items, the matrix subject and QP antecedents each appeared as options "(A)" and "(B)" an equal number of times. Fillers that did not include pronouns consisted of complex (ambiguous and unambiguous) sentences containing elliptical gaps. Two paraphrases, (A) and (B), were provided as answers which participants had to choose between using the same scale as in the experimental items.

The experimental and filler items were pseudo-randomized such that no two experimental items appeared next to each other. Items were spread across two presentation lists in a Latin-square design. Forward and reverse orders of each list were presented to the same number of participants. Participants were instructed to simply read each sentence and provide an answer to the questions using the drop-down menu.

### Results

Responses were coded from −2 to 2, with −2 meaning "QP strongly preferred" and 2 meaning "DP strongly preferred." A score of 0 indicated either antecedent was equally likely, while −1 and 1 indicated a mild preference for the QP and DP respectively. The average rating in the c-commanding QP condition was −0.16 (SD 1.62) and in the non c-commanding condition 1.38 (SD 1.14). A pairwise comparison indicated that scores were significantly higher in the non c-commanding QP condition than the c-commanding QP condition [t1(31) = 8.19, p < 0.001; t2(15) = 11.80, p < 0.001]. This indicates that the DP antecedent was chosen more often when the QP did not c-command the pronoun compared to when it did. One sample t-tests indicated that the average scores in the c-command condition did not differ significantly from 0 [t1(31) = 0.90, p = 0.374; t2(15) = 1.23, p = 0.237], but that the scores in the non c-command condition were significantly higher than 0 [t1(31) = 11.12, p < 0.001; t2(15) = 16.46, p < 0.001]. This indicates that when the QP c-commanded the pronoun, participants considered either antecedent equally likely, but that the DP was preferred when the QP did not c-command the pronoun.

### Discussion

The results of Experiment 1 align with intuitions from the theoretical linguistics literature. When the QP c-commanded the pronoun, participants were equally likely to interpret the pronoun as referring to either the QP or the DP antecedent. When the QP did not c-command the pronoun, participants preferred to interpret the pronoun as being coreferential with the DP. Experiment 1 thus suggests that naïve participants are sensitive to the c-command restriction on variable binding2 . Experiment 2 tested how this constraint is implemented during online sentence processing.

## Experiment 2

The aim of Experiment 2 was to investigate the application of the c-command constraint on variable binding during realtime language processing. Participants read a series of texts as in (6) while their eye-movements were monitored. The gendermismatch paradigm (Sturt, 2003; Kazanina et al., 2007) was used as a diagnostic of dependency formation.

In (6a,b) the pronoun he is c-commanded by the QP every old (wo)man. In (6c,d) the pronoun is not c-commanded by the QP, as it appears inside a relative clause. In (6a,c) the QP every old man matches the gender of the pronoun, while in (6b,d) the QP every old woman does not. If participants attempt to retrieve the c-commanding QP upon encountering the pronoun, we expect to observe a gender mismatch effect such that reading times at or shortly after the pronoun should be longer in gender mismatch condition (6b) than gender match condition (6a). If the c-command constraint restricts antecedent retrieval during processing (Kush et al., 2015), no gender mismatch effect should be observed when the QP appears inside a relative clause, as in (6c,d). If however participants violate the c-command constraint during processing, we can expect to see gender mismatch effects in both (6a,b) and (6c,d). Sensitivity to the c-command constraint

2A reviewer notes that the results of Experiment 1 on their own could equally be explained in terms of a dispreference for linking pronouns to antecedents inside relative clauses, irrespective of quantification, rather than a specific constraint on variable binding to QPs. While this is a possible explanation of the results in Experiment 1, the results of Experiments 2 and 3 suggest that the restriction on binding to QPs is best characterised in terms of the c-command constraint, rather than a general dispreference against antecedents inside relative clauses.

is thus diagnosed statistically by an interaction between the main effects of c-command and gender, while main effects of gender would indicate constraint violation.

### Methods

### Participants

Thirty two native English speakers (8 males, mean age 19; range 17–23) from the University of Edinburgh community with normal or corrected-to-normal vision, and who did not take part in any of the other experiments reported here, took part in Experiment 2.

### Materials

Twenty four experimental items as in (6) were constructed. A full list can be found in Appendix B. Each item began with a short context sentence that took up one line onscreen. The critical second sentence appeared across two lines, with the line-break always appearing before the adverb [silently in (6)] that appeared before the verb preceding the critical pronoun. The matrix subject of the critical sentence always matched the pronoun in stereotypical gender to ensure that a felicitous interpretation of the pronoun was always possible. The critical gender manipulation between the QP and pronoun always involved definitional gender (e.g., every old man/ woman).

In addition to the experiment items, 60 filler texts were also constructed that included a variety of different constructions, some of which included different types of anaphors. The fillers took up between two and three lines of text onscreen.

### Procedures

Experimental and filler items were pseudo-randomized such that no two experimental items appeared adjacent to each other and were spread across four presentation lists in a Latin-square design. A different random order of items was presented to each participant. The experiment began with five practice items to familiarize participants with the procedure. All items were presented in Consolas fixed width font and displayed across up to three lines of text onscreen.

Eye movements were recorded using the EYELINK 2000 system, sampling at a rate of 1000 Hz. While viewing was binocular, eye movements were recorded from the right eye only. Each experimental session began with calibration of the eye-tracker on a nine-point grid, and any drift in calibration was compensated for via recalibration between trials if required. Before each trial, participants fixated on a fixation marker above the first word of the trial to be displayed. Upon fixation on this marker, the trial text appeared. Participants read each text silently at their normal reading rate, pressing a button on a control pad once completed. To ensure participants paid attention to the content of the sentences, comprehension questions requiring a yes/no push button response followed two thirds of all trials. The entire experiment lasted approximately 30–45 min in total.

Reading times are reported for four regions of text. The critical pronoun region consisted of the subject pronoun and the preceding complementiser (that he). We extended the pronoun region to the left of the critical pronoun rather than the right to avoid effects of first-pass processing at the pronoun being mixed with spillover effects at the post-pronoun region. As the perceptual span in English is approximately eight characters to the right of fixation (Rayner, 1998), fixations on the complementiser are likely to involve foveal processing of the pronoun. The spillover region comprised the two words after the pronoun (could go) while the prefinal region consisted of the next two words (a little). The final region consisted of the rest of the critical sentence (bit faster).

Four reading time measures are reported for each region of text. First pass reading time is the summed duration of fixations within a region during its first inspection, until it is exited to the left or right, while regression path duration is calculated by summing the duration of each fixation, starting with the first fixation when a region is entered from the left, up until but not including the first fixation in a region to the right. In addition to these two first-pass processing measures, we also calculated second pass times, which included all fixations within a region after it has been exited following the first-pass. Total viewing times, which sum all fixations in a region, are reported as a global measure of processing load. All trials in which track loss occurred were discarded, and regions which were initially skipped during reading were treated as missing data in the two first-pass measures. For second pass times, trials in which a region was not refixated after the first-pass contributed a second pass time of zero to the calculation of averages. Prior to the calculation of reading time measures an automatic procedure merged short fixations of 80 ms or below that were within one degree of visual arc of another fixation. All other fixations of 80 ms or below, as well as those above 800 ms, were removed. Outliers that were above or below 3.5 standard deviations from a participant's mean reading time for each measure were also removed before analysis.

Analysis was conducted using linear-mixed effects models with crossed random effects for subjects and items (Baayen, 2008; Baayen et al., 2008). For each reading time measure, the analysis included deviation-coded fixed main effects of "c-command" (ccommand vs. non c-command), "gender" (match vs. mismatch) and their interaction. Subject and item random intercepts, as well as subject and item random slopes for each fixed effect, were included using a "maximal" random effects structure (Barr et al., 2013). If this maximal model failed to converge, the random effects structure was simplified by removing the random correlation parameters, which for the analyses reported here always led to convergence. For fixed effects, p-values were estimated from the t distribution (Baayen, 2008, p. 248). In the case of reliable interactions, planned comparisons compared gender mismatch effects separately for the two c-command and two non c-command conditions.

### Results

Overall accuracy to the comprehension questions was 88% (all subjects above 73%), indicating that participants paid attention to the content of the sentences. Track loss accounted for 0.1% of the data and skipping rates for the pronoun, spillover, prefinal and final regions were 26, 5, 19, and 10% respectively3 . A summary of the reading time data is provided in **Table 1**. **Table 2** provides a summary of the statistical analysis.

At the pronoun region, there was a significant main effect of c-command in first-pass reading times, with reading times being longer in the two non c-command conditions (6c,d) than c-commanding conditions (6a,b). This likely reflects spillover processing as a result of the extra layer of syntactic embedding from the relative clause that appears in conditions (6c,d) but not (6a,b). There were significant c-command by gender interactions in both second-pass and total viewing times. Planned comparisons in both measures indicated that when the QP ccommanded the pronoun, reading times were longer in gender mismatch condition (6b) than gender match condition (6a) (for second-pass times, estimate = 71, SD = 30, t = 2.407, p = 0.017; for total viewing times, estimate = 80, SD = 31, t = 2.586, p = 0.010). The same comparisons in the two non c-command conditions were not significant (for both measures, t < 1, p > 0.651). This pattern of results, with gender mismatch effects in the c-command conditions only, is illustrated for second pass times in **Figure 1**. These results indicate that readers attempted to link the pronoun to the QP when it c-commanded the pronoun but not when it did not.

At the spillover region, there were significant main effects of gender in both second-pass and total viewing times that were modulated by significant c-command by gender interactions in both measures. Again, planned comparisons in the c-command conditions indicated significantly longer reading times for gender mismatch condition (6b) than gender match condition (6a) (for second-pass times, estimate = 111, SD = 33, t = 3.403, p < 0.001; for total viewing times, estimate = 134, SD = 35, t = 3.920, p < 0.001), but there were no significant differences between the two non c-command conditions (for both measures, t < 1, p > 0.563). These results further indicate that readers retrieved the QP upon encountering the pronoun, but only when the QP c-commanded it.

At the prefinal and final regions there were marginally significant c-command by gender interactions in the regression path times. At the prefinal region, regression path durations were again numerically larger following a gender mismatch in the c-command conditions only, but here neither of the planned comparisons was significant (both t < 1.2, both p > 0.236). At the final region, regression path durations were marginally longer following gender mismatches in the two c-command conditions (estimate = 405, SD = 225, t = 1.801, p = 0.073). The same comparison for the two non c-command conditions was not significant (t < 1. p > 0.470).

### Discussion

The results of Experiment 2 clearly show that readers readily retrieved the QP upon encountering the pronoun, but only when it was a syntactically licit antecedent. At both the critical pronoun and spillover regions, second-pass and total viewing times were longer when the QP mismatched in gender with the pronoun,

3 Skipping rates at the pronoun region were quite high in Experiments 2–4. We thus conducted an additional analysis in which the two first-pass measures at the pronoun were calculated using a leftward-shifting procedure (see Sturt, 2003, p. 548). In this analysis, if the pronoun was initially skipped during reading, fixations up to four characters to the left of the region boundary were included in the calculation of first-pass and regression path times. This reduced skipping rates at the pronoun to below 8% across experiments, but did not alter the overall pattern of results compared to the non-shifted analysis reported in the main text.

TABLE 2 | Summary of statistical analyses for four eye-movement measures at four regions of texts in Experiment 2.

*Estimate* = *Model Estimate (SE in brackets). (*\**)* = *p* < *0.10,* \* = *p* < *0.05,* \*\* = *p* < *0.001.*

but only when the QP c-commanded the pronoun. Similar trends were also observed in regression path times at later regions of text. At no point in time did we observe any reliable effect of the gender of the QP on participants' reading times when it did not c-command the pronoun. These results indicate that the c-command constraint on variable binding restricts antecedent retrieval during the resolution of subject pronouns.

One potential counterargument to this interpretation of our results is that the QPs inside relative clauses may have been ignored during retrieval not because of the ccommand constraint on variable binding, but rather because antecedents inside relative clauses are comparatively nondiscourse prominent. The results of Cunnings et al. (2014) however provide evidence against this interpretation. In their Experiment 1, they observed that readers would readily retrieve a non-quantified coreference antecedent inside a relative clause. This suggests that it is not the case that all antecedents inside relative clauses are ignored during retrieval, but rather they are readily retrieved only when syntactically licit.

However, it remains at least possible that there may have been subtle pragmatic differences between the texts used in Experiment 2 reported here and those used by Cunnings et al. (2014), which may have favored retrieval of the relative clause antecedent in Cunnings et al.'s study but not here. Note also that the coreference antecedent in Cunnings et al. was a proper name, which are known to be particularly discourse prominent (Sanford and Garrod, 1988). The aim of Experiment 3 was to investigate whether the selective retrieval profile observed in the current experiment is truly a result of the c-command constraint on variable binding or results from differences in discourse prominence between c-commanding and non c-commanding antecedents in general.

## Experiment 3

The aim of Experiment 3 was to investigate whether the c-command relationship between antecedent and pronoun affects the possibility of retrieval for non-quantified referential antecedents. The experimental materials used were identical to those from Experiment 2, except that the critical QP was replaced with a non-quantified referential DP as in (7).

As for QPs in Experiment 2, the DP c-commands the pronoun in (7a,b) but does not in (7c,d). In conditions (7a,c) the pronoun matches in gender with the DP, while in (7b,d) there is a gender mismatch. While variable binding between the pronoun and QP was syntactically illicit in conditions (6c,d) in Experiment 2, there is no constraint that restricts linking the pronoun to the DP in (7c,d) via coreference assignment. As such, if the results of Experiment 2 reflect application of the c-command constraint on variable binding, we expect to find different results with coreference antecedents in Experiment 3. That is, in contrast to the interactions observed in Experiment 2, in Experiment 3 main effects of gender should be observed such that reading times should be longer in gender mismatch conditions (7b,d) than gender match conditions (7a,c), irrespective of c-command.

However, if antecedents inside relative clauses are simply ignored during retrieval as they are not discourse prominent, we expect to observe similar results in Experiment 3 as were observed in Experiment 2. That is, we should observe reliable ccommand by gender interactions, with gender mismatch effects being observed in c-command conditions (7a,b) but not non c-commanding conditions (7c,d).

## Methods

### Participants

32 native English speakers (17 males, mean age 21; range 18–30) from the University of Edinburgh community, none of whom took part in any of the other eye-tracking experiments reported here, took part in Experiment 3. All had normal or corrected-tonormal vision.

### Materials

The 24 sets of experimental items from Experiment 2 were adapted as in (7). Experimental items were again interspersed with 60 fillers and pseudo-randomly distributed across four presentation lists in a Latin-square design.

### Procedures

The procedure and data analysis were the same as outlined for Experiment 2.

### Results

Average comprehension question accuracy was 90% (all subjects over 77%). There was no track loss and skipping rates for the pronoun, spillover, prefinal, and final regions were 32, 9, 16, and 12% respectively. Summaries of the reading time data and statistical analysis are provided in **Tables 3**, **4**.

At the pronoun region, there were significant main effects of gender in second pass and total viewing times, with reading times being longer in gender mismatch conditions (7b,d) compared to gender match conditions (7a,c). In contrast to Experiment 2, there was no hint of an interaction between c-command and gender in any measure at the pronoun region. This suggests that the DP was retrieved irrespective of whether or not it was inside a relative clause. This pattern of results for the second pass times at the pronoun region is shown in **Figure 1**.

The results of the spillover region replicated this pattern of results. In second pass times there was a marginal main effect of gender, with reading times again tending to be longer following a gender mismatch between the pronoun and DP compared to when there was a gender match. Total viewing times displayed the same pattern of results, with the main effect of gender being fully significant in this measure.

At the prefinal region, there was a significant c-command by gender interaction in first-pass reading times. Here, in the ccommand conditions reading times were numerically longer in gender mismatch condition (7b) than gender match condition (7a). The planned comparison was however not significant (t = 1.506, p = 0.133). The opposite numerical pattern was observed in the two non c-command conditions, with gender match condition (7c) having numerically longer reading times than gender mismatch condition (7d). The planned comparison was however only marginally significant (estimate = 24, SD = 13, t = 1.851, p = 0.065). It is unclear what this numerical pattern might mean, and it is not replicated in any other measure. Indeed, in the regression path times at this region there was a significant main effect of gender, with reading times following the pattern observed at the pronoun and spillover regions, with reading times being longer following gender mismatches between the DP and pronoun compared to when there was a gender match.

#### TABLE 3 | Reading times in milliseconds for four eye-movement measures at four regions of texts in Experiment 3 (SDs in parentheses).

TABLE 4 | Summary of statistical analyses for four eye-movement measures at four regions of texts in Experiment 3.

*Estimate* = *Model Estimate (SE in brackets). (*\**)* = *p* < *0.10,* \* = *p* < *0.05,* \*\* = *p* < *0.001.*

There was also a marginally significant main effect of gender in the regression path times at the final region, with reading times again tending to be longer when the pronoun mismatched in gender with the DP compared to when there was a gender match.

#### Discussion

The results of Experiment 3 are in clear contrast to those from Experiment 2. Whereas we observed significant c-command by gender interactions at the pronoun and spillover regions in Experiment 2, in Experiment 3 we observed only significant main effects of gender at these regions. This suggests that, in contrast to Experiment 2, in Experiment 3 participants were equally likely to retrieve the DP antecedent in both the ccommand and non c-command conditions. Indeed, the relative time-course of mismatch effects across both experiments is very similar (compare graphs from Experiments 2 and 3 in **Figure 1**). The crucial difference between the two is that while mismatch effects were restricted to the c-command conditions in Experiment 2, they appear irrespective of c-command in Experiment 3. This provides good evidence that the results of Experiment 2 cannot be explained in terms of antecedents inside relative clauses simply being non-discourse prominent. Rather, while both antecedents that c-command a pronoun and those that do not are readily retrieved, quantified antecedents are only retrieved when variable binding is syntactically licit. It is this contrast between syntactically licit and syntactically illicit pronoun-antecedent dependencies that appears to best explain the contrast in results between Experiments 2 and 3.

Although the results of Experiments 2 and 3 indicate that the c-command constraint restricts antecedent retrieval during language processing, one issue that remains is how the ccommand constraint and gender congruence combine during anaphora resolution. In Experiments 2 and 3, there was always at least one gender-matching and syntactically licit antecedent in the discourse, namely the matrix subject DP [the surgeon in (5) and (6)]. To fully test how the c-command constraint and gender congruence interact to guide antecedent retrieval, it is also necessary to investigate anaphora resolution when the only syntactically licit antecedent available in the discourse provides only a partial match to the cues at retrieval. Experiment 4 was thus conducted to test this issue.

## Experiment 4

The aim of Experiment 4 was to investigate how the ccommand constraint and gender congruence combine to guide antecedent retrieval. Materials in Experiment 4 contained the two non c-command conditions from Experiment 2, additionally manipulating the stereotypical gender relationship between pronoun and matrix subject DP as in (8).

In (8), the QP always appears inside a relative clause and as such is not a syntactically licit antecedent of the pronoun. In each condition, the only syntactically licit antecedent is the matrix subject DP the surgeon. In (8a,b), this DP matches in stereotypical gender with the pronoun, whereas in (8c,d) there is a stereotypical gender mismatch. In (8a,c) the non c-commanding QP additionally matches the gender of the pronoun, while in (8b,d) it does not.

Different predictions with regards to the time-course of antecedent retrieval can be made depending on how the c-command constraint and gender congruence combine. If syntactic constraints on anaphora resolution constitute "hard constraints" that gate retrieval to syntactically licit antecedents (Dillon et al., 2013; Chow et al., 2014; Kush et al., 2015), we should observe main effects of the gender of the DP only. Reading times should be longer in DP gender mismatch conditions (8c,d) than in DP gender match conditions (8a,b). The gender of the syntactically illicit QP should not influence reading times at any point in the sentence.

Alternatively, if the c-command constraint and gender congruence combine to guide retrieval, we expect to observe facilitatory interference (e.g., Wagers et al., 2009). In this case, we would expect reading times to generally be longer in DP gender mismatch conditions (8c,d) than DP gender match conditions (8a,b). However, the size of the gender mismatch effect should be reliably attenuated when the structurally illicit QP matches in gender with the pronoun. In this case, reading times should be shorter in condition (8c), when the QP matches the gender of the pronoun, in comparison to (8d), when neither antecedent matches. This result would indicate that when no syntactically licit antecedent is available in the discourse that matches the pronoun's gender, a gender matching but syntactically illicit antecedent may sometimes be retrieved.

Another possibility is that we may observe a difference in the time-course of effects for syntactically licit and illicit antecedents. Sturt (2003) proposed the "defeasible filter" hypothesis which predicts that initially only structurally licit antecedents are considered, but that structurally illicit antecedents can subsequently be retrieved during later stages of processing. Applying this logic to the current experiment, we may observe an initial attempt to retrieve only the syntactically licit DP, followed by subsequent effects of the syntactically illicit QP. In this case, we should observe main effects of stereotypical gender mismatch between the pronoun and DP antecedent only at or shortly after the pronoun, with any effects of the gender of the structurally illicit QP antecedent being in comparison delayed.

### Methods

### Participants

32 native English speakers (12 males, mean age = 24; range = 18– 49) from the University of Edinburgh community with normal or corrected-to-normal vision, none of which took part in Experiments 1–3, took part in Experiment 4.

### Materials

The 24 experimental items from Experiment 2 were adapted as in (8), and again pseudo-randomly interspersed with 60 fillers across four presentation lists in a Latin-square design. The stereotypical gender manipulations included items that had previously been pre-tested to ensure they displayed the intended stereotypes (Cunnings and Felser, 2013; Cunnings et al., 2014).

### Procedures

The procedure and data analysis were the same as in Experiments 2 and 3.

### Results

Overall accuracy to comprehension questions was 89% (all subjects above 77%). Track loss accounted for 0.1% of the data. Skipping rates for the pronoun, spillover, prefinal and final regions were 21, 7, 14, and 7% respectively. Summaries of the reading times and statistical analyses are shown in **Tables 5**, **6**.

At the pronoun region, we observed significant main effects of the gender of the DP in both second pass and total viewing times. In both measures, reading times were longer when the DP mismatched in stereotypical gender with the pronoun, as in (8c,d) compared to when there was a stereotypical gender match, as in (8a,b). The gender of the QP did not significantly affect reading times in any measure at this region. These results suggest that participants attempted to retrieve the syntactically licit DP antecedent. This pattern of results is illustrated in **Figure 1**, which shows the second pass times at the pronoun region.

At the spillover region, there was a significant main effect of DP gender in first pass times. Here, reading times were again longer when the DP mismatched in stereotypical gender with the pronoun compared to when there was a gender match. There was also a significant main effect of the gender of the DP in both second-pass and total viewing times, with reading times again being longer when the DP mismatched in stereotypical gender with the pronoun. There was additionally a marginally significant main effect of QP gender in total viewing times only. Here, reading times tended to also be longer when the QP mismatched in gender with the pronoun. There was no hint of an interaction however, as this numerical trend for longer reading times following gender mismatching QPs was observed in both the DP match and DP mismatch conditions.

At the prefinal region, there was again a significant main effect of DP gender in total viewing times, with reading times being longer when the DP mismatched in stereotypical gender with the pronoun. No significant effects of the gender of the QP were found at this region.

At the final region there was a marginally significant interaction in first-pass times. Here, in the DP stereotypical gender match conditions, reading times tended to be longer in QP match condition (8a) compared to QP mismatch condition (8b), but the planned comparison was not significant (t = 1.476, p = 0.141). The opposite numerical pattern was observed in the DP stereotypical gender mismatch conditions, but again the comparison was not significant (t = 0.779, p = 0.437). In regression path times the main effect of the stereotypical gender of the DP was significant, the main effect of the gender of the QP marginal, and the DP gender by QP gender interaction significant. In this measure, while reading times in DP match conditions (8a,b) did not differ (t = 0.381, p = 0.703), for the DP stereotypical gender mismatch conditions, reading times were longer in QP match condition (8c) than QP mismatch condition (8d) (estimate = 569, SD = 220, t = 2.591, p = 0.010). While this reading time measure thus provides evidence of the QP's gender

TABLE 6 | Summary of statistical analyses for four eye-movement measures at four regions of texts in Experiment 4.

*Estimate* = *Model Estimate (SE in brackets). (*\**)* = *p* < *0.10,* \* = *p* < *0.05,* \*\* = *p* < *0.001.*

significantly influencing reading times, the direction of the effect in the DP stereotypical gender mismatch conditions is in the opposite direction to that predicted by facilitatory interference. Total viewing times at the final region exhibited reading times similar to earlier regions of text, with reading times being significantly longer when the DP mismatched in stereotypical gender with the pronoun compared to when there was a gender match. The QP did not significantly influence reading times in this measure.

### Discussion

The results of Experiment 4 indicate that readers readily retrieved the syntactically licit DP antecedent upon encountering the pronoun. In a number of measures across all regions of text reported, we observed significantly longer reading times when the DP mismatched in stereotypical gender with the pronoun compared to when there was a gender match. Effects of the gender of the QP antecedent were more elusive and the one significant effect that we did observe was delayed in comparison to the effects that were observed of the DP's gender. While DP stereotypical gender mismatch effects were first observed in second pass and total viewing times at the pronoun, and first pass times at the spillover region, the only reliable effect of the gender of the QP was observed in the regression path times at the final region. We leave discussion of this delayed effect of the QP's gender until the General Discussion, but overall interpret the relative time-course of effects as indicating that the c-command constraint on variable binding restricts the initial stages of antecedent retrieval during comparatively earlier stages of anaphora resolution. We discuss the implications of these results, along with the other experiments reported above, in more detail below.

### General Discussion

The aim of this study was to investigate if the c-command restriction on variable binding restricts antecedent retrieval during anaphora resolution. The results of Experiment 1 indicate that native English speakers are sensitive to the c-command restriction on binding by quantified antecedents in an offline judgment task. Experiment 2, which investigated the extent to which QP antecedents are retrieved upon encountering a pronoun during online processing, indicates that participants readily retrieved the QP upon encountering the pronoun, but only when the QP c-commanded the pronoun. The results of Experiment 3 showed that retrieval of DP antecedents, which is not contingent on c-command, was equally likely irrespective of whether or not the DP c-commanded the pronoun. The results of Experiments 2 and 3 together confirm that it is not the case that non c-commanding antecedents are generally ignored due to their lower discourse salience. Instead, both c-commanding and non c-commanding antecedents are readily retrieved, but only when they are syntactically licit antecedents for a pronoun. Finally, the results of Experiment 4 indicate that when only one syntactically licit antecedent is available in the discourse, that antecedent is preferentially retrieved over a syntactically illicit QP, even when the syntactically licit antecedent mismatches in gender with the pronoun. This different pattern of results across the three eye-movement experiments is illustrated in **Figure 1**. Together, these data indicate that the c-command constraint on variable binding restricts antecedent retrieval during anaphora resolution. Below we discuss the implications of these results with regards to how the c-command constraint on variable binding may be implemented in models of memory retrieval, and the relative weightings of different cues to antecedent retrieval during anaphora resolution.

### Implementing the C-command Constraint

One potential way to help ensure that only syntactically licit QPs are retrieved during anaphora resolution might be to restrict at least initial memory access operations to antecedents that ccommand a pronoun. This proposal would be similar to claims in the linguistics literature that variable binding is computed before coreference assignment (e.g., Reuland, 2001, 2011; Koornneef, 2008). In the current study, c-commanding antecedents always appeared in the main clause of the critical sentence, while non c-commanding antecedents appeared in relative clauses. The preference for retrieving a c-commanding antecedent in the current study could thus potentially be achieved by postulating that pronouns preferentially cue retrieval of an antecedent carrying a [+main clause] feature. However, this would also predict that non c-commanding DPs, even though they can be linked to the pronoun via coreference assignment, should also initially be ignored. Note however that while we observed selective retrieval of QPs in Experiment 2 and retrieval of DPs irrespective of c-command in Experiment 3, the time-course of gender mismatch effects across the pronoun and spillover regions in both experiments was very similar. If an initial retrieval favors antecedents carrying the [+main clause] feature only, we would have expected to see a delay in gender mismatch effects for non c-commanding DP antecedents compared to c-commanding DP antecedents in Experiment 3 that was not observed. The results from Cunnings et al. (2014) also clearly indicate that there is no initial preference for c-commanding over non c-commanding antecedents. Thus, we believe the hypothesis that initial retrieval operations should always simply ignore non c-commanding antecedents can be rejected. Nor can the retrieval operation initially target only referential antecedents or quantified ones, considering that Cunnings et al. (2014) observed no overall preference for either variable binding or coreference assignment.

Sensitivity to the c-command constraint on variable binding thus requires a restriction that selectively retrieves antecedents based on the c-command relationship between the pronoun and QP. As noted in the introduction, some have claimed that this type of relational constraint may be difficult to implement in content-addressable memory architectures (Kush, 2013; Kush et al., 2015). Kush et al. propose that one way to implement the c-command constraint on variable binding would be to encode all potential antecedents with an ACCESSIBLE feature that the parser is able to dynamically update based on the current state of the parse during incremental processing. That is, antecedents are always initially marked as [+accessible], but retrieval operations at specific points during an incremental parse may deactivate this feature if need be. We believe this proposal could account for our results as follows. In Experiments 2–4, the critical QP/DP (every old man/woman; the old man/woman) will initially be encoded as being [+accessible]. In the c-commanding QP/DP conditions, this feature will always remain activated. In the non c-commanding QP/DP conditions, upon reaching the right-most edge of the relative clause, a retrieval operation will access all antecedents within the relative clause, deactivating the ACCESSIBLE feature for QPs to ensure that they are no longer possible targets for retrieval, but leaving it unchanged for DPs. In this way, well-known clause "wrap-up" effects may in part involve updating items in a particular clause as being either accessible or inaccessible to further retrieval operations. Upon encountering the pronoun, the ACCESSIBLE feature will be a highly weighted cue to retrieval, activating DPs irrespective of c-command, but activating c-commanding QPs only.

### Cue Weighting during Anaphora Resolution

The results of the current study indicate that the c-command constraint on variable binding, perhaps implemented using the ACCESSIBLE feature as above, is a highly weighted cue to antecedent retrieval. The gender mismatch effects observed in Experiment 2 indicate that participants will readily retrieve a ccommanding QP during processing, but we found no evidence of the QP being retrieved when it did not c-command the pronoun. In Experiment 4, when the QP was always syntactically illicit, we found that a number of reading time measures were significantly affected by the stereotypical gender of the syntactically licit DP only. The earliest measures where we observed this effect were those including first pass processing at the spillover region and second pass processing at the pronoun region.

Some models of memory retrieval assume that cues combine in an equally-weighted fashion to guide retrieval during language processing (e.g., Lewis et al., 2006). Evidence from facilitatory interference effects during subject-verb agreement processing for example, suggest that for at least some dependencies syntactic constraints and agreement markers are equally weighted cues to retrieval (e.g., Wagers et al., 2009). More recently however it has been claimed that retrieval cues during language processing are not always equally weighted (Van Dyke and McElree, 2011; Dillon et al., 2013). For example, Dillon et al. claimed that syntactic binding constraints constitute "hard constraints" that restrict retrieval to syntactically licit antecedents. We argued that the most obvious kind of evidence that the c-command constraint and gender congruence combine equally to guide retrieval would be from facilitatory interference effects similar to those observed for subject-verb agreement. However, we failed to observe this pattern of results in Experiment 4.

Although we failed to observe facilitatory interference, Badecker and Straub (2002) reported a different type of inhibitory interference in a series of self-paced reading experiments. They observed longer reading times when multiple antecedents matched in gender with a reflexive or pronoun compared to when there was only one gender matching antecedent. Such effects could indicate that when there are multiple gender matching antecedents in the discourse, both syntactically licit and illicit antecedents compete for retrieval. The clearest evidence of this type of interference in the current study would have been from longer reading times in Experiment 4 in multiple gender match condition (8a) compared to the single match condition (8b). However, we also failed to observe this type of effect.

The clearest evidence of the gender of the QP significantly affecting reading times that we did observe was in the opposite direction predicted by facilitatory interference, and was also dissimilar to the effects observed by Badecker and Straub (2002). In the regression path times for the final region in Experiment 4, reading times were significantly longer when the syntactically illicit QP matched the gender of the pronoun, but only when the grammatically licit DP antecedent itself mismatched in gender with the pronoun. Note also that this effect of the QP's gender appears delayed in comparison to the significant main effects of the stereotypical gender of the syntactically licit DP.

In line with recent proposals that not all cues to memory retrieval are equally weighted during language processing (Van Dyke and McElree, 2011; Dillon et al., 2013), we argue that the c-command constraint on variable binding, implemented with the ACCESSIBLE feature, is a more highly weighted cue to antecedent retrieval than gender congruence during anaphora resolution. Whether or not the c-command restriction acts as a "hard constraint" that imposes a categorical ban on the retrieval of syntactically illicit antecedents is difficult to conclude. However, the relative time-course of effects observed for DP and QP antecedents in Experiment 4 may bear on this issue. Recall that in the DP stereotypical gender mismatch conditions in the regression path times of the final region in Experiment 4, we observed longer reading times when the QP matched the gender of the pronoun compared to when it mismatched. We remain cautious in interpreting precisely what this effect may index, but it could potentially indicate that readers sometimes attempted to coerce an interpretation in which the pronoun was linked to a syntactically illicit but gender matching QP antecedent, with this coercion of a syntactically illicit interpretation leading to longer reading times. The time-course of this effect, appearing at the sentence final region and delayed in comparison to stereotypical gender violations between the DP and pronoun, may indicate that it reflects a relatively late interpretive process that tries to coerce an otherwise dispreferred interpretation for the pronoun. Similar to Sturt's (2003) defeasible filter hypothesis, we propose that the time-course of effects observed in Experiment 4 may indicate that initially, retrieval operations attempt to retrieve syntactically licit antecedents only. Readers may sometimes try to coerce syntactically illicit interpretations during comparatively later stages of processing however, perhaps during reanalysis after initially retrieving a syntactically licit, but gender-mismatching antecedent. We note also however that other interpretations of this delayed effect are possible. Kush et al. (2015) for example, found that non c-commanding QPs did not influence reading times during early stages of anaphor resolution in sentences like (4b), but did find some suggestive evidence of delayed effects of non c-commanding QPs influencing processing in measures that included second-pass processing. They claimed that such delayed effects might index coercion of an additional referential antecedent for the pronoun from the set of antecedents implied by the quantifier. In this sense, when the pronoun matches the gender of a non c-commanding QP in sentences like (8c), the delayed effect we observed may index coercion of a referential antecedent (an old woman) from the set of antecedents implied by the QP (every old woman). We do not attempt to tease apart these two interpretations here. Irrespective of how these effects are to be interpreted, as they appear delayed in comparison to effects of syntactically licit antecedents, we maintain that retrieval operations initially attempt to retrieve grammatically licit antecedents only.

Finally, we note that counterexamples in which variable binding appears to be possible between a pronoun and antecedent irrespective of c-command have been discussed in the linguistics literature. For example, in Every boy's mother says that he is special the pronoun can be bound by the QP every boy even though the QP does not c-command the pronoun under the standard definition. Barker (2012) discusses a number of such counterexamples and claims that the restriction on variable binding should be recast in terms of semantic scope rather than c-command. The relative clause manipulation tested in the current study is a relatively clear-cut case where both traditional accounts and Barker would predict that variable binding is not permitted. Our results show that variable binding is not attempted during processing in such cases, at least during early stages of antecedent retrieval (see also Kush et al., 2015). The extent to which pronouns may trigger retrieval of non ccommanding QPs in other constructions is less well understood. Some researchers have investigated whether pronouns are linked to QPs in non c-commanding configurations other than the relative clause manipulation in the current study (e.g., Carminati et al., 2002; Kush et al., 2015, Experiment 1c), but these experiments used different diagnostics for dependency formation and did not use interference paradigms as in Experiment 4 here. One question that arises is whether retrieval of QPs upon encountering a pronoun is always, at least initially, restricted to c-commanding quantified antecedents, or whether in exceptional cases, as in sentences like Every boy's mother says that he is special, quantified antecedents are always accessible. How the ccommand constraint and gender/number congruence interact to guide anaphora resolution in other constructions will thus be an important avenue of further research to investigate the extent to which the current findings generalize beyond the relative clauses tested here.

### Conclusion

Across four experiments we investigated how constraints on pronoun interpretation influence the retrieval of quantified and non-quantified antecedents in different syntactic configurations. We found that variable binding between a pronoun and quantified antecedent was only attempted if the quantifier c-commanded the pronoun. Retrieval of coreference antecedents, which is not contingent on c-command, was attempted irrespective of c-command. We interpret these results as indicating that syntactic constraints restrict memory retrieval operations during anaphora resolution. We conclude that the c-command constraint on variable binding constitutes a highly weighted cue during anaphora resolution that, at least initially, guides retrieval operations to access syntactically licit antecedents only.

### Acknowledgments

This research was supported by a British Academy Postdoctoral Fellowship to IC (pf100026) and by an Alexander-von-Humboldt-Professorship to Prof. Harald Clahsen (Potsdam Research Institute for Multilingualism), which is gratefully acknowledged. We also acknowledge the support of the Deutsche Forschungsgemeinschaft and the Open Access Publishing Fund of the University of Potsdam.

### References

**Conflict of Interest Statement:** The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.

Copyright © 2015 Cunnings, Patterson and Felser. This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) or licensor are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.

## Appendix A

The materials for Experiment 1 are provided below. The c-command manipulation is denoted in square brackets, delimited with a forward slash (/).

## Appendix B

The materials for Experiment 2 are provided below. Gender manipulations are shown in parenthesis and square brackets denote the c-command manipulation, delimited with a forward slash (/).

every man (woman) at the village church heard] suddenly claimed that he should give more money to charity.

garden/who every girl (boy) in the beautiful garden believed] wishfully thought that she could smell all the lovely roses.

# Active search for antecedents in cataphoric pronoun resolution

*Leticia Pablos1,2\*, Jenny Doetjes1, Bobby Ruijgrok1,2 and Lisa L.-S. Cheng1,2*

*1 Leiden University Center for Linguistics, Leiden University, Leiden, Netherlands, 2 Leiden Institute for Brain and Cognition, Leiden University, Leiden, Netherlands*

Cataphoric dependencies where a pronoun precedes its antecedent appear to call on different mechanisms in language comprehension from forward dependencies where the antecedent precedes the pronoun. Previous research has shown that the resolution of cataphoric dependencies involves predictive processes such as the active search mechanism, which hypothesizes the automatic search for an antecedent immediately after encountering a cataphoric pronoun. The current study employs gender mismatch to investigate whether the active search for an antecedent of a cataphoric pronoun is restricted only to grammatically licit positions. We present results from an eventrelated potential experiment on the reading comprehension of cataphoric dependencies in Dutch. Results show that gender mismatch gives rise to an anterior negativity at grammatically licit antecedent positions only. We hypothesize that this negativity reflects the prediction failure for an antecedent after encountering a pronoun, rather than a gender mismatch. We discuss the timing, topography and functionality of this negativity with respect to previous studies and how this relates to the ERPs elicited in the processing of structural constraints on pronoun resolution.

#### *Edited by:*

*Colin Phillips, University of Maryland, USA*

### *Reviewed by:*

*Stephen Politzer-Ahles, University of Oxford, UK Sol Lago, University of Potsdam, Germany*

#### *\*Correspondence:*

*Leticia Pablos<EMAIL_ADDRESS>
#### *Specialty section:*

*This article was submitted to Language Sciences, a section of the journal Frontiers in Psychology*

*Received: 14 July 2015 Accepted: 12 October 2015 Published: 30 October 2015*

#### *Citation:*

*Pablos L, Doetjes J, Ruijgrok B and Cheng LL-S (2015) Active search for antecedents in cataphoric pronoun resolution. Front. Psychol. 6:1638. doi: 10.3389/fpsyg.2015.01638* Keywords: cataphora, active search, gender mismatch, anterior negativity, Principle C

## INTRODUCTION

The on-line interpretation of pronominal dependencies has raised several questions within theories of sentence comprehension. Forward pronominal dependencies – where the antecedent precedes the pronoun – and backward pronominal dependencies – where the pronoun precedes the antecedent – appear to call on different mechanisms in language comprehension. In the case of forward dependencies, their resolution requires retrieving the information about the antecedent at the position of the pronoun, which is closely connected with memory-retrieval processes (Chow et al., 2014). On the other hand, the resolution of backward dependencies (also called cataphoric dependencies) requires the search for an antecedent, which is related to predictive processes.

One of such predictive processes is the active search mechanism (ASM), found initially for the interpretation of *wh*-gap dependencies (Crain and Fodor, 1985; Stowe, 1986; Clifton and Frazier, 1989). In the case of backward dependencies, the ASM hypothesizes that the human parser automatically starts a search for an antecedent in the upcoming sentence immediately after encountering a cataphoric pronoun. This has been shown in behavioral studies through gender mismatch effect (GMME) observations in experimental paradigms where possible antecedents for cataphoric pronouns are restricted by grammatical principles (Sturt, 2003; Van Gompel and Liversedge, 2003; Kazanina et al., 2007; Yoshida et al., 2014). This paper presents an event related potential (ERP) study where we confirm that a similar effect can also be observed in neurophysiological data. Results support the presence of an ASM for cataphoric dependency resolution that respects grammatical principles. The topography and timing of the ERP component generated at the mismatching antecedent position in our study was an anterior negativity, while previous forward antecedent/pronoun dependencies studies have found a P600 (Osterhout and Mobley, 1995; Van Berkum et al., 2007; Xu et al., 2013). We postulate that the ERP component observed in cataphoric dependencies is related to a failure of a prediction by the parser, in line with the active search approach, while in the case of forward antecedent dependencies the effect can only be connected to a gender mismatch as no prediction is made (the pronoun is not required to interpret the antecedent).

### Cataphoric Dependencies

Cataphoric pronouns are pronouns that occur linearly before their antecedent. In other words, they are instances of referential dependencies in which the antecedent follows the referentially dependent element, as illustrated in (1). The index *i* indicates that *hei* and *Peteri* refer to the same person.

(1) While **hei** had a broken arm, **Peteri** could not ride his bike.

Pronouns such as *he* in (1) pose an interesting case for parsing theories. In order to resolve the interpretation of the pronoun with an antecedent in the same sentence, the parser needs to wait until the appearance of the antecedent. When the antecedent is found, the pronoun can establish a link with it for its own interpretation. However, this is only possible when the grammar allows the link between the cataphoric pronoun and the antecedent to be established. Consider the pronoun *he* in (2) and the pronoun *his* in (3). In contrast to the pronoun in (1), the pronoun in (2) cannot take the proper name *Peter* as its antecedent (as indicated by the starred index of *j* – *he* cannot have the same index/reference as *Peter*). However, *Peter* can be the antecedent of the pronoun *his* in (3).

The restriction of the pronominal reference in (1), (2), and (3) can be captured under the principles of the Binding Theory (Chomsky, 1981) that indicates the configurations in which nominal elements can or cannot establish a coreferential relation. There are three Binding Principles, each of which concerns a different type of nominal elements. Binding Principles A and B are concerned with two different types of pronouns (*himself* vs. *him*), while Principle C restricts the distribution of Referential Expressions, including proper names such as *Peter*.

We focus on Principle C, which prohibits a Referential Expression (e.g., proper name) from being *bound* (Chomsky, 1981). The pronoun *he* in (1) does not bind the referential expression *Peter*, because the pronoun is embedded in an adverbial clause that does not contain *Peter*. Given that *he* does not bind *Peter*, the two can have the same reference. On the other hand, the pronoun *he* in (2) binds the referential expression *Peter* structurally and in such a case, coreference is excluded. *His* in (3) on the other hand is more deeply embedded in the structure (i.e., in the noun phrase *his brother*), and therefore, it does not act as a binder of *Peter*. Thus, similar to (1), a cataphoric dependency can be established in (3). Referential expressions, such as *John* or *the man*, independently refer and select a referent from the domain of discourse. Given that Referential Expressions have independent reference, they do not need and in fact cannot tolerate a binder. The binder would act as an antecedent for the Referential Expression, which is in conflict with the referential status of the latter.

In this study, we investigate whether Principle C of the Binding Theory is respected in cataphoric pronoun processing. As illustrated in (1), (2), and (3), whether a referential expression can be a potential antecedent for a cataphoric pronoun depends on the structural configuration. If a coreferential relation is established between a referential expression and a cataphoric pronoun and as a result, the referential expression is bound by the pronoun, Principle C of the Binding Theory would be violated. This paper examines how this type of violation affects parsing. In particular, it uses gender mismatch to investigate whether a search for an antecedent is restricted by structural constraints. Given that the parser respects structural constraints such as Principles B and C of the Binding Theory when interpreting pronouns on-line as shown by behavioral studies that have examined reading times (e.g., Kazanina et al., 2007; Chow et al., 2014; Yoshida et al., 2014), we expect these effects to be visible through electroencephalography (EEG) as well.

### Active Search Mechanism [or Active Filler Hypothesis (AFH)]

The ASM claims that an active search is automatically initiated for each uninterpreted element A encountered in a sentence, to find the element B which can help interpret A. The main evidence for the existence of the active search comes from the so-called filled-gap effects involving *wh*-dependencies, which demonstrate that (a) a search for a gap starts as soon as a *wh*-phrase is processed and (b) filling the gap position where the *wh*-word could be interpreted with an overt element (thus blocking the parser from interpreting the *wh*-phrase in that position) results in a longer processing time compared to a sentence where no *wh*-dependency was initiated (Crain and Fodor, 1985; Stowe, 1986; Lee, 2004). Thus, the ASM hypothesizes that the parser anticipates a gap as soon as a *wh*-phrase is processed (Clifton and Frazier, 1989; Frazier and Clifton, 1989).

In the case of pronoun interpretation, the ASM predicts that a search is initiated for an antecedent as soon as a pronoun is encountered (Clifton and Frazier, 1989; Kazanina et al., 2007), in order to resolve the interpretation of the pronoun. Even though pronouns may have antecedents outside of the sentence that contains them, the ASM assumes that the search for an antecedent within the sentence is the default strategy in cases where there is no preceding discourse.

Studies on the processing of cataphoric pronouns have examined whether the parser indeed searches for an antecedent in the sentence once a pronoun has been processed and when the grammar allows the establishment of the binding relation (Sturt, 2003; Van Gompel and Liversedge, 2003; Kazanina et al., 2007; Yoshida et al., 2014). In these behavioral studies, which used eyetracking or self-paced reading methodology, the parser searches for an antecedent in the upcoming input in positions where the coreference between the pronoun and the antecedent is allowed (i.e., such coreference does not lead to a violation of the Binding Theory). In such cases, when the potential antecedent does not match in gender with the preceding pronoun, reading times are longer than when the potential antecedent and the pronoun match in gender (Sturt, 2003; Van Gompel and Liversedge, 2003; Kazanina et al., 2007; Yoshida et al., 2014). This reading slowdown effect, known as the GMME, has been taken to be a sign of the parser's active search for an antecedent to interpret the pronoun. Importantly, the data in these studies show that the GMME does not occur if the coreference between the pronoun and the referential expression yields a violation of the Binding Theory (in particular, Condition C), suggesting that in such cases, the referential expression does not count as a potential antecedent for the pronoun.

The main hypothesis of Kazanina et al. (2007) word-byword self-paced reading experiments is that the parser respects Principle C of the Binding Theory when searching for an appropriate antecedent for a pronoun. This can be illustrated on the basis of the four different conditions in (4), which are from their third experiment: no constraint match in (4a), no constraint mismatch in (4b), Principle C match in (4c) and Principle C mismatch in (4d).

#### (4) **a. No constraint/Match**

**Hisi** managers chatted amiably with some fans while **the talented, young quarterbacki** signed autographs for the kids, but **Carol** wished the children's charity event would end soon so she could go home.

#### **b. No constraint/Mismatch**

**Heri** managers chatted amiably with some fans while **the talented, young quarterback** signed autographs for the kids, but **Caroli** wished the children's charity event would end soon so she could go home.

#### **c. Principle C/Match**

**Hei** chatted amiably with some fans while **the talented, young quarterback** signed autographs for the kids, but **Stevei** wished the children's charity event would end soon so he could go home.

### **d. Principle C/Mismatch**

**Shei** chatted amiably with some fans while **the talented, young quarterback** signed autographs for the kids, but **Caroli** wished the children's charity event would end soon so she could go home.

In the no constraint match condition in (4a), the possessive pronoun *his*, being further embedded in the nominal structure, does not bind the referential expression *young quarterback,* allowing it to be a potential antecedent. In other words, in (4a), Principle C does not block the coreference relation between the pronoun *his* and the referential expression (the antecedent *young quarterback*), and these two elements match in gender. Therefore the cataphoric pronoun should be interpreted at the antecedent position. The no constraint mismatch condition

in (4b) differs from the no constraint match condition in (4a), in that the gender of the pronoun *her* and that of the potential antecedent *young quarterback* do not match, creating a GMME. In the Principle C match condition in (4c), on the other hand, the pronoun *he* binds the referential expression *young quarterback* in the embedded clause. Thus, *young quarterback* is excluded as a potential antecedent of *he* due to a Principle C violation. Furthermore, both the pronoun *he* and the referential expression *young quarterback* match in gender, as both are masculine. Finally, in the Principle C mismatch condition in (4d) the pronoun *she*, binds the referential expression *young quarterback* in the embedded clause, just like in (4c); however, in this case, they mismatch in gender. Importantly, the GMME is expected to be absent in the Principle C mismatch condition (condition 4d) at the position of the referential expression *young quarterback*, relative to the Principle C match condition (4c), as the coreference relation is barred from being established due to Principle C, preventing the GMME to occur. Conversely, the GMME is expected to be present at the referential expression *young quarterback* position in the no constraint mismatch condition (4b), relative to the no constraint match condition (4a). The main findings of Kazanina et al. (2007) confirm these expectations. Their reading time results thus suggest that the parser abides by Principle C when it attempts to resolve the interpretation of cataphoric pronouns in real-time in that they only find a reading time difference, or GMME, in the no constraint conditions, in which the referential expression in the no constraint mismatch condition in (4b) elicited longer reading times than the no constraint match condition (4a) at the same position (in particular, at the noun *quarterback*), whereas this reading time difference was absent at the referential expression in the Principle C conditions in (4c) and (4d). Furthermore, Kazanina et al. (2007) claim that the active search for an antecedent in cataphoric configurations only occurs when the Binding Principles allow it.

Yoshida et al. (2014) examine the formation of cataphoric dependencies across a relative clause island in a word-by-word self-paced reading experiment and they expect to obtain a GMME, or longer reading times, only in cases where coreference between the pronoun and the antecedent is licit (i.e., not obeying Principle C). Further, the GMME would only be expected to occur if cataphoric dependencies were not to be sanctioned across relative clause islands. Similar to Kazanina et al. (2007), Yoshida et al. (2014) manipulated the sentence initial pronoun [nominative vs. (possessive) genitive], the gender of the pronoun and the first referential expression. Their stimuli are shown in (5). In (5a) and (5b) the pronouns *his/her* can corefer with the referential expression *Jeffrey Stewart* (thus, *Jeffrey Stewart* can be a potential antecedent), but in (5c) and (5d) coreference is not licit due to Principle C of the Binding Theory.

#### (5) **a. No Constraint/Match**

**Hisi** managers revealed that the studio that notified **Jeffrey Stewarti** about the new film selected a novel for the script, but **Annie** did not seem to be interested in this information.

#### **b. No constraint/Mismatch**

**Heri** managers revealed that the studio that notified **Jeffrey Stewart** about the new film selected a novel for the script, but **Anniei** did not seem to be interested in this information.

#### **c. Principle C/Match**

**Hei** revealed that the studio that notified **Jeffrey Stewart** about the new film selected a novel for the script, but **Andyi** did not know which one.

#### **d. Principle C/Mismatch**

**Shei** revealed that the studio that notified **Jeffrey Stewart** about the new film selected a novel for the script, but **Anniei** did not know which one.

A GMME or reading slowdown is found at the antecedent position *Jeffrey Stewart* (in particular, at the last name *Stewart*) in (5b) relative to (5a), where the pronoun and the antecedent could corefer (the coreference does not violate Principle C). Moreover, the GMME or reading time difference occurs despite the fact that the potential antecedent is contained within a relative clause island. The GMME generated in the no constraint conditions (5a) and (5b) in the self-paced reading experiment by Yoshida et al. (2014) confirms that online formation of a cataphoric dependency is not affected by island constraints in that coreference is established in (5a) and (5b) conditions when the grammatical constraint of Principle C does not ban this coreference. If island constraints affected the generation of a cataphoric dependency we will not expect a GMME to occur in no constraint conditions, which it does. Furthermore, these results support the claim in Kazanina et al. (2007), that the processing of cataphoric dependencies is modulated by a grammatically constrained ASM, which respects grammatical principles such as Principle C.

The current study aims to replicate the GMME results from previous studies (Sturt, 2003; Van Gompel and Liversedge, 2003; Kazanina et al., 2007; Yoshida et al., 2014; a.o.) using ERP, to identify a neural correlate of the ASM found in the on-line interpretation of cataphoric dependencies. If an active-search is initiated for these dependencies (as shown by previous behavioral studies through the generation of the GMME effect, which is a slowdown in the gender mismatching conditions relative to the gender matched ones), it should be possible to identify an effect (i.e., an ERP component) comparable to the reading time differences shown in behavioral studies with the ERP methodology. In other words, we predict there to be a GMME in the no constraint mismatch conditions such as (4b) and (5b) above, relative to the no constraint match conditions in (4a) and (5a).

### Event-related Potential (ERP) Studies on Gender Agreement/Mismatch

Since the current study examines gender agreement mismatches at the antecedent position in cataphoric configurations, a brief overview of the ERP studies that have tackled gender agreement issues is in order. Gender agreement mismatches have been examined in the ERP literature using different paradigms. Wicha et al. (2004) found a P600 for gender disagreeing nouns in determiner-noun combinations in Spanish, where the expected noun mismatched in gender with the preceding determiner. Van Berkum et al. (2005) on the other hand tested the prediction for the likely appearance of a specific noun based on the previous discourse. Their aim was to examine how listeners use their discourse knowledge to predict specific nouns. If listeners anticipate a noun with a specific gender by the time they encounter the indefinite article (not gender marked) in the story, a gender-mismatched adjective (i.e., mismatched in accordance to the gender of the noun that is expected) would be a surprise, leading to an ERP effect at the adjective position. They tested Dutch sentences where the sentence continuations had either an adjective consistently gender-marked with the upcoming predicted noun and its gender, or an adjective inconsistently gender-marked with respect to the prediction made for the upcoming noun and its gender. Their results again showed a P600 for gender-mismatched adjectives.

In a different set of studies, gender agreement violations between a determiner and a noun, or between an adjective and a noun, showed a left anterior negativity (LAN) followed by a P600 at the noun position for Spanish, Italian, and German (Demestre et al., 1999; Gunter et al., 2000; Barber and Carreiras, 2005; Molinaro et al., 2008; a.o.), a P600 for English and Dutch (Hagoort and Brown, 1999) and a N400 followed by a P600 for Hebrew (Deutsch and Bentin, 2001).

Finally, in a third set of studies, gender violations were tested in forward pronoun resolution dependencies, i.e., dependencies in which antecedents occur before pronouns. Osterhout and Mobley (1995) tested sentences such as (6) where a masculine or feminine pronoun matched or mismatched in gender with a previously encountered antecedent. They found a P600 at the pronoun *he* that mismatched in gender with the previously encountered feminine antecedent *the aunt*. Note that coreference between *he* and *the aunt* is only blocked by the gender mismatch and not by the Binding Conditions, as pronouns, contrary to referential expressions, may be bound by their antecedent if the antecedent is located in a different clause (cf. Principle B of the binding theory).

(6) **The aunt** heard that **she/he** had won the lottery.

Similarly, studies that tested gender violations in comparable forward pronoun configurations in Dutch (Van Berkum et al., 2007) and Chinese (Xu et al., 2013) found a P600 at the position of the pronoun when it mismatched in gender with the preceding antecedent.

Taking into consideration the results in these studies that have manipulated gender agreement, it is clear that a P600 component emerges constantly, regardless of whether the relation is one between (1) a determiner and a noun; (2) an adjective and a noun; or (3) an antecedent and a pronoun. While the P600 is preceded by a LAN or by a N400 in some cases in pure pronoun resolution cases more akin to the manipulation in the current study, only a P600 is obtained at the position of the gender-mismatched pronoun.

### The Current Study

As indicated above, the present study examines processing of pronouns and their antecedents in a *cataphoric configuration*,

where the pronoun linearly precedes the antecedent. To summarize, the aim of this study is threefold. (i) First is to examine whether there is a GMME when the parser encounters the first potential antecedent of the cataphoric pronoun that does not match in gender. This would be an indication that the parser starts actively searching for a matching antecedent after encountering the cataphoric pronoun, even though the antecedent of the pronoun could, in principle, be found outside of the sentence. We predict the GMME to be present in the case of a mismatch, and absent in the matching condition. (ii) Second, we examine if the search mechanism is modulated by grammatical constraints such as Principle C of the Binding Theory. For cases where co-reference may lead to Principle C violations, we predict no difference between the match and the mismatch conditions. We predict that an ERP component is elicited only for referential expressions that can legitimately establish a coreference relation with the cataphoric pronoun. (iii) Third, we examine if cataphoric pronoun dependencies generate the same kind of ERP components as forward pronoun dependencies. As discussed above, previous studies (e.g., Osterhout and Mobley, 1995; Van Berkum et al., 2007; Xu et al., 2013; a.o.) examined forward dependencies. However, no ERP study has examined cataphoric dependencies where the pronoun precedes the antecedent.

We aimed to search for the neuronal correlates of the ASM by means of a technique that has an excellent temporal resolution and where the effects of the active search can be examined by looking directly at brain behavior.

### MATERIALS AND METHODS

### Materials

Thirty-six experimental items were constructed in Dutch. These 36 items were distributed across four lists in a Latin Square design, which implies that each participant saw nine trials per condition. We decided on the relatively small number of trials per condition for a number of reasons: (a) The GMME effect has been quite reliable in the behavioral literature. Thus, we expect the size effect of the gender mismatch to be robust; (b) we would like to avoid reading fatigue as well as participant developing different processing strategies derived from the high number of proper names included in the items. Note that previous studies, which investigated the processing of coreference involving repeated nouns with the ERP technique, used a higher number of trials per condition for their experiments (i.e., 40 trials per condition; see for example, Swaab et al., 2004; Ledoux et al., 2007). However, the research questions of these studies and our initial question do not overlap, since these studies were examining word repetition-priming effects and the impact this factor had on the modulation of the N400 ERP component, whereas our interest lays in the process of coreference itself. The vast majority of ERP experiments in the field present every participant with 20–40 items per condition, but this is because the ERP effects that the experimenters are after are often rather small. Likewise, the use of a large number of trials is often connected to the fact that usually some trials are discarded due

to artifacts or to the type of ERP component that the researchers are after, which might be different in size (see for example, Luck, 2005; Kaan, 2007 for further discussion of this specific issue).

We followed closely the set-up of the English word-by-word self-paced reading experiment by Kazanina et al. (2007) while creating our ERP experiment, since we were interested in seeing the time-course of the GMME using ERPs. There are four experimental conditions, as shown in (7). First, No-Constraint conditions, which contain a possessive pronoun, in masculine (7a) or feminine form (7b) that matches or mismatches, respectively, in gender with the linearly first antecedent *Lodewijk* (masculine). Second, Principle C conditions, which contain a cataphoric nominative pronoun in masculine (7c) or feminine form (7d) that cannot co-refer with the referential expression *Lodewijk* in the embedded clause due to Principle C.

In all conditions, the test sentences always contain a licit antecedent for the pronoun. For example, in the No-Constraint mismatch condition in (7b) and in Principle C conditions in (7c) and (7d), the pronouns corefer with an antecedent that appears toward the end of each sentence [i.e., *Mirjam* in (7b) and (7d), and *Thomas* in (7c)]. Relevantly, even if pronouns could have co-reference with an antecedent outside of the sentence, the availability of an antecedent in the same sentence (i.e., *Mirjam/Thomas*) guarantees that the pronounantecedent relation is resolved within the sentence. Feminine and masculine pronouns and referential expressions were counterbalanced. Previous reading time studies found effects at positions immediately following the antecedent (see Yoshida et al., 2014). Based on this, we included proper names with a surname (such as *Lodewijk Boer*) in our data to ensure that there could be a region immediately following the proper name that was still connected to the antecedent position. However, considering the superior time accuracy of the ERP technique, our prediction was that the effect should be observable at the target position rather than at immediately following regions. Participants read 36 target stimuli such as those in (7; see Data Sheet in Supplementary Material for a whole list of stimuli) randomly interspersed with 35 unrelated fillers that were part of a different experiment that examined the processing of backward negative polarity item dependencies (Pablos et al., 2012).

#### (7) **a. No-Constraint/Match**

**Zijnj** assistenten kwamen erachter dat **Lodewijkj Boer** geen prijswinnaar *His assistants found out that Lodewijkmasc Boer no prizewinner* geselecteerd had, maar **Mirjami** had geen interesse in de roddel.

*selected had but Mirjamfem had no interest in the gossip* 'His assistants found out that Lodewijk Boer had not selected a prizewinner, but Mirjam had no interest in the gossip.'

#### **(b) No-Constraint/Mismatch**

**Haari** assistenten kwamen erachter dat **Lodewijkj Boer** geen prijswinnaar *Her assistants found out that Lodewijkmasc Boer no prizewinner* geselecteerd had, maar **Mirjami** had geen interesse in de roddel. *selected had, but Mirjamfem had no interest in the gossip.*

'Her assistants found out that Lodewijk Boer had not selected a prizewinner, but Mirjam had no interest in the gossip.'

#### **c. Principle C/Match**

**Hiji** kwam erachter dat **Lodewijkj Boer** geen prijswinnaar *He found out that Lodewijkmasc Boer no prize winner*

geselecteerd had, maar **Thomasi** had geen interesse in de roddel.

*selected had, but Thomasmasc had no interest in the gossip.* 'He found out that Lodewijk Boer had not selected a prizewinner, but Thomas had no interest in the gossip.'

#### **d. Principle C/Mismatch**

**Ziji** kwam erachter dat **Lodewijkj Boer** geen prijswinnaar *She found out that Lodewijkmasc Boer no prize winner* geselecteerd had, maar **Mirjami** had geen interesse in de roddel.

*selected had, but Mirjamfem had no interest in the gossip.* 'She found out that Lodewijk Boer had not selected a prizewinner, but Mirjam had no interest in the gossip.'

### Participants

Twenty-four students of Leiden University participated in this study, which was conducted at the EEG Laboratory in the Faculty of Social Sciences of Leiden University. They were all native speakers of Dutch. All participants had normal or corrected-tonormal vision, were right-handed, gave informed consent and were paid €12.50 for their participation, which lasted around 30 min, excluding set-up time. The experiment followed the Ethics Committee regulations of the Faculty of Social Sciences of Leiden University, which approved its implementation.

 Sentences were presented one word at a time in black letters on a white screen using the presentation software E-prime (Psychology Software Tools Inc.). Each sentence was preceded by a fixation cross ("+") which appeared at the center of the screen and remained there for 1000 ms. The fixation point was followed by a blank screen interval of 300 ms, and then the sentence was displayed word by word.

Each word appeared on the screen for 300 ms, followed by a fixation cross ("+") at the center of the screen that remained visible for 300 ms. Participants were instructed to read the sentences carefully for comprehension. The last word of each sentence was marked with a period, and 1000 ms later a comprehension question appeared and prompted the participant to press a button to continue. Every experimental item was followed by a comprehension question. The comprehension questions targeted different positions of the sentence and some of them targeted the referential expressions *Lodewijk Boer* or *Thomas/Mirjam*. The comprehension questions were counterbalanced for yes and no answers and, for some items, they differed across conditions (see Data Sheet in Supplementary Material). Four counterbalanced lists derived from a Latin Square Design were used for the experiment. Before starting the experimental phase, eight warm-up practice trials were presented to the participants, which had no similarity to any of the targets or filler items in the experiment. Participants were able to ask clarification questions to the experimenter about the task at the practice time. The experimental session was broken up by two break periods, with a different number of items distributed across each block, with 35 and 36 sentences per block.

### EEG Recording

The EEG signal was continuously acquired at a sampling frequency of 512 Hz using a BioSemi (Active Two) system from 32 Ag/AgC1 electrodes distributed in the scalp following the extended 10–20 convention (Fp1/2, FC5/, AF3/4, Fz, CP5/6, CP1/2, Cz, F7/8, F3/4, T7/8, C3/4, Pz, FC1/2, P3/4, O1/2, Oz, P7/8, PO3/4). EEG data was referenced on-line to two auxiliary electrodes: common mode sense (CMS) and driven right leg (DRL) and re-referenced off-line to the mean activity at the two mastoids. A high-pass filter with a cut-off frequency of 0.1 Hz was applied online to eliminate DC drifts. Vertical and horizontal eye movements were monitored with two electrodes at the infraorbital and supraorbital, and electrodes at the outer canthus of the right and left eyes. Electrode impedances were monitored during installation to ensure a low level of electronic noise.

### EEG Analysis

For every subject, recorded EEG waveforms were post-processed before analysis to reduce noise and artifacts as much as possible. After applying a high-pass filter to remove slow drifts and DC offsets, ocular correction was performed using an implementation of the Gratton et al. (1983) algorithm. Other artifacts were removed both by visual inspection and by performing an automated detection based on gradient change rate. The process resulted in the rejection of 6% of the trials (51 out of 864) distributed among the experimental conditions as follows: (7a) 1%; (7b) 1%; (7c) 2%; (7d) 2%. To confirm that these small differences between conditions were not significant and did not introduce biases in the results, we ran a repeated measures mixed-logit analysis with Match (match/mismatch) and Constraint (No Constraint/Principle C) as independent variable and Subject as random factor. Both main effects and interactions were considered, and no significant difference in likelihood ratio between the fitted model and a null intercept only model was observed.

As a final step, a low-pass filter with a cut-off frequency of 30 Hz was applied to remove noise and non-neurological signals. After the data cleaning, a few electrodes identified as noisy or with intermittent connection were replaced by an interpolation based on neighboring channel responses.

Electroencephalography recordings were then segmented from 200 ms before to 800 ms after the onset of the significant region being analyzed (*Lodewijk*). A baseline correction was applied based on the average of the 200 ms prior to the stimulus onset.

Previous studies that have examined gender mismatches consistently reported a P600 component. In order to evaluate the presence of a P600 in our experimental data, the 500–700ms time window was tested by means of a 4-way repeated-measure ANOVA, considering four within-subject factors. Two to evaluate the signal scalp distribution: *Hemisphere* [Left *(Fp1, F3, F7, C3, P3, O1)* Central *(Fz, Cz, Pz)*, Right *(Fp2, F4, F8, C4, P4, O2)*], and *Position* [Frontal *(Fp1, Fp2, F3, F4, F7, F8)*, Medial *(C3, Cz, C4),* and Parietal *(P3, Pz, P4, O1, O2)*]; and two to examine effects between conditions: *Constraint* (No Constraint/Principle C), and *Match* (Match/Mismatch). Mean voltage-amplitude was considered as the dependent variable in the analysis, and p-values where corrected for sphericity where required.

### RESULTS

### Comprehension Questions

Average accuracy rates were high and no participants were rejected on the basis of accuracy (*M* = 84.59%, *SD* = 5.44%). The accuracy scores were similar across conditions (*M*NoConstraintMatch = 81%, *M*NoConstraintMismatch = 84%, *M*PrincipleCMatch = 87%, *M*PrincipleCMismatch = 86%). The difference in mean values was not significant as shown by a 2 × 2 repeated-measures ANOVA randomized by subjects with *Constraint* and *Match* as independent factors and Response Accuracy as dependent variable (*p >* 0.5 for all main effects and interactions).

### Event Related Potentials

We investigated ERPs at the subject position of the embedded clause, *Lodewijk*, which is the first potential antecedent position in the sentence if there is no Principle C violation. Four-way ANOVA performed in the pre-selected P600 time window (500–700 ms) did not result in any significant main effect or interaction (*p* ≥ 0.1 in all cases), as shown in the right most column of **Table 1**. However, visual comparison of the grand average time traces in the anterior electrodes for the No-Constraint Mismatch condition (7b) versus No-Constraint Matched (7a) condition shows an apparent sustained negativity in the 200–600 ms region (**Figure 1**). The anterior topography of the negativity can be observed in **Figure 2**. No such negativity is observed for Principle C Match/Mismatch conditions (**Figures 3** and **4**). The asymmetry observed in the No-Constraint with respect to the Principle C conditions supports the expectation of the experimental manipulation, therefore, an exploratory analysis was performed to investigate the reliability and nature of this apparent difference.

An omnibus ANOVA performed in the complete 200– 600 ms time window shows a significant 4-way interaction of *Constraint, Match, Hemisphere,* and *Position* [*F*(4,92) = 2.572; *p* = 0.043]. Follow-up simple interaction analysis for each level of the *Constraint* factor reveals no significant interaction or main effect in Principle C conditions, while a significant 3-way interaction between *Hemisphere* × *Match* × *Position* is present in No-Constraint [*F*(4,92) = 3.202, *p* = 0.016]. A further breakdown of this interaction for every level of the *Position* condition shows a significant effect of *Match* factor at the Anterior sites [*F*(1,23) = 4.82, *p* = 0.038], and no dependence on *Hemisphere*. The *No-Constraint Mismatch* condition (7b) waveform average amplitude is more negative than (7a) [*t*-test nearly significant difference *t* (23) = 1.989, *p* = 0.057].

The same analysis was repeated using sliding 200 ms long windows to localize the effect with respect to the onset time of the stimuli. **Table 1** summarizes the omnibus ANOVAs and **Table 2** provides the follow up simple interaction evaluation for those regions with significant interaction in the omnibus ANOVA. (Only significant comparisons and effects are shown for readability. Values are corrected for sphericity where required – corrected *p*-values are reported).

Finally, **Table 3** shows a summary of the main effects and *post hoc* pairwise comparisons observed in the two time windows (200–400 ms, 300–500 ms) in the breakdown of the interactions observed in **Table 2**, which in all cases reflect a significant anterior negativity of the *Mismatch* condition for the *No-Constraint* case when compared with the *matched* counterpart.

However, the results of the exploratory analysis above present the multiple comparison problem (MCP). To limit the Family Wise Error Rate (FWER) to a 5% level, the individual comparisons reported in **Table 1** should have a *p*-value lower than 0.05/4 = 0.0125. In addition, an individual 2 × 2 ANOVA – to verify the interaction of the *Constraint* and *Match* factors in the topographical regions of interest defined by the *Position* and *Hemisphere* factors considered in the above analysis – did not yield a significant interaction in neither of the time windows (*p >* 0.10). This result is very likely due to the low statistical power provided by the small number of electrodes in each region of interest, and the limited number of trials.

To address the problem of MCP and verify if the differences observed were reliable, the ERPs measured were analyzed with a repeated measures two-tailed cluster mass permutation test (Bullmore et al., 1999; Maris and Oostenveld, 2007) using the Matlab Mass Univariate ERP Toolbox (Groppe et al., 2011). This test provides a better spatial and temporal resolution and weak control of the FWER. We included

all samples between 200 and 800 ms at all 32 electrodes. Electrodes within an approximate distance of 5.77 cm from each other were considered spatial neighbors for the cluster determination. Repeated measures *t*-tests were performed on the difference wave of the Match and Mismatch conditions for both *No-Constraint* and *Principle C* factor levels. *T*-test included the original data and 2500 random within-subjects permutations. With this technique, we tested separately the null hypothesis that the *Match* and *Mismatch* position do not differ in the No-Constraint and Principle C conditions. The maximum cluster-level mass procedure in the No-Constraint Match versus Mismatch comparison returned a cluster at the central-frontal electrodes extending temporally from 300 to ∼420 ms with an alpha level *p* = 0.07 (see **Figure 2**). In contrast, the procedure in the Principle C conditions did

FIGURE 2 | Topographic scalp maps of the difference wave between the *No-Constraint Mismatch* and the *No-Constraint Match* condition at a series of discrete time positions. The electrodes that were significantly different between the two conditions in the cluster mass univariate analysis (*p <* 0.07) are marked in white.

not reject the null hypothesis to any level of significance (*p >* 0.4).

In conclusion, results show significant differences to an alpha level of ∼0.07 between the *Match* and *Mismatch* conditions in the No-Constraint cases only, with anterior topographic distribution over a window around 300–420 ms. The observed difference is both in the direction expected based on the theoretical predictions, and with a coherent spatial and temporal localization. This reinforces that the effect is reliable even with the aforementioned reduced confidence level, compared to traditional 5% values. The presence of a positive result in an experiment with a relatively low power in terms of the number of trials observed per subject and condition (i.e., 9) suggests that the effect size is large and would be more prominent with an increased number of items [see Maxwell

#### TABLE 2 | Simple interactions follow-up.

∗*p < 0.05.*

#### TABLE 3 | Simple comparisons "No Constraint" condition.

∗*p < 0.05.*

et al. (2008) for a discussion on sample size and statistical power].

### DISCUSSION

### Active Search for Antecedents

We have shown that, in cases such as (7b) (No-Constraint Mismatch), where there is a gender mismatch between the pronoun and the first potential antecedent for this pronoun, an anterior negativity is generated at the potential antecedent position *Lodewijk*. This is not the case for (7a), where the potential antecedent matches in gender with the preceding pronoun. The anterior negativity could be interpreted as a result of the gender mismatch between a cataphoric pronoun and its antecedent, as well as the effect of failing to find an antecedent at the first potential position. However, for (7c) and (7d), where the cataphoric pronoun cannot corefer with the referential expression *Lodewijk* due to Principle C, no component is generated at the referential expression position. This confirms our predictions that (i) an active search for an antecedent is initiated as soon as a cataphoric pronoun is processed and that, (ii) although the ASM can be automatically initiated for every pronoun, which referential expression will be considered by the ASM is constrained by grammatical principles (in this case, Principle C). This result is in line with the behavioral results (e.g., Kazanina et al., 2007) that found a GMME at the potential antecedent.

### Forward vs. Backward Antecedent/Pronoun Dependencies and Prediction Failure

The differences observed in ERP components generated between our results in the case of cataphoric dependencies (anterior negativity) and the forward pronominal dependency studies (Osterhout and Mobley, 1995; Van Berkum et al., 2007; Xu et al., 2013; P600) raise questions on the nature of the effect observed.

In the current experiment, we focus on the relation between a *cataphoric* pronoun and its potential antecedent. In the case of forward antecedent-pronoun dependencies [as in (6)], there is no need to search for a pronoun after encountering the antecedent (e.g., *the aunt*) since this referential expression can be independently interpreted. In other words, we do not expect an active search for a pronoun in the case of forward dependencies. The P600 component in these cases, therefore, must correspond to a gender mismatch between the referential expression and the pronoun.

In backward, cataphoric pronoun-antecedent dependencies, on the other hand, the processes underlying the generation and interpretation of these dependencies are different since the interpretation of the pronoun needs to be resolved. It is therefore reasonable to hypothesize that the parser prefers to start a search as soon as a pronoun is encountered. The anterior negativity in our experiment could be interpreted as related to the searching process itself, namely, a failure of a prediction and not so much to the gender mismatch. The GMME provides the evidence that the antecedent search is active in the noconstraint cases, but it might not be the primary reason for the generation of the anterior negativity. Nevertheless, after having examined previous literature on gender mismatches, we might still wonder why no P600 as well is generated for the gender mismatch at *Lodewijk* in (7b) after encountering the feminine pronoun *haar*. We hypothesize that, in forward dependencies, the parser needs to retrieve the gender of the antecedent from memory and check for gender matching. The P600 could be a reflection of the gender mismatch alone. Conversely, in backward dependencies, the parser anticipates the appearance of an antecedent in the upcoming sentence as soon as it processes the pronoun. Thus, when the parser encounters the first potential antecedent position, it expects to find a matched antecedent. When it fails, there is a negativity generated instead of a P600 because the failure of finding a matching antecedent prevails over the GMME. With this claim we do not intend to imply that the gender mismatch does not occur at all or that it does not precede the expectation failure (since the failure of the prediction cannot occur before the mismatch is detected) rather that the failure of finding a matching antecedent veils the presence of a P600.

In the second experiment in Osterhout and Mobley (1995), a negativity (at anterior and temporal sites in the left-hemisphere between 300 and 500 ms) is found for a dependency where a specific verb form that agrees with the subject is predicted and fails. In our experiment, a negativity is found for a dependency where an antecedent for the cataphoric pronoun is predicted and this prediction fails because of a gender mismatch. These two types of dependencies are different in nature (one involves subject-verb agreement and the other a pronoun-antecedent coreferential relation), but the mechanism of prediction failure seems to be the same in that there is a negative component generated in both cases. Despite of the fact that the negativities in these two studies are different in distribution, we suggest that they are connected to the same basic process, and that they reflect the failure of a previously established expectation. However, we have to consider that the presence of a negativity in agreement violations is currently under debate since not all the studies observed it (see Nevins et al., 2007; Mancini et al., 2011; Molinaro et al., 2011; a.o.).

### Potential Task and Stimuli Presentation Effects

One of the potential sources for the lack of P600 for the gender mismatch in our study might connect to issues that previous studies have discussed (Bornkessel-Schlesewsky et al., 2011; Molinaro et al., 2011; Sassenhagen et al., 2014), such as the influence of task and the modality of stimulus presentation. The current study used word-by-word visual presentation of the sentences in which subjects had to read the sentence and answer a Yes/No comprehension question afterward. Studies that have shown P600 effects for gender mismatches in forward antecedent/pronoun dependencies (Osterhout and Mobley, 1995; Van Berkum et al., 2007; Xu et al., 2013) have all used visual presentation, so the mode of presentation does not seem to have an impact in the results. Differences between our study and previous studies rest in the task that participants were required to complete. Van Berkum et al. (2007) do not require any task from participants besides reading the sentences, whereas Osterhout and Mobley (1995) and Xu et al. (2013) ask their participants to conduct an acceptability judgment after reading each sentence. Sassenhagen et al. (2014) discuss the idea that the generation of a P600 can be taskdependent and that consciously detected violations might differ with respect to non-consciously detected violations in that the detected or attentive violations elicit both an early negative component and a P600, whereas the non-detected ones do not necessarily elicit a P600 (Hasting and Kotz, 2008; Batterink and Neville, 2013). Results from our experiment seem to align with this idea since we only get an early negativity and the study does not implement a task that highlights the mismatch.

### Temporal Characteristics and Scalp Distribution of Negativities in Previous ERP Studies