KB-S and KM-S conceived of the original study. KB-S collected the data. EJ, KB-S, KM-S, and MC conceived of the current analysis, analyzed the data, and revised the manuscript. EJ wrote the initial draft.

#### ACKNOWLEDGMENTS

The data reported in this study was originally collected as part of the doctoral dissertation by Brill-Schuetz (2016). A special thank you goes to Rex Dayola and Mallory Webber for their essential contributions to this study.

of the 25th Annual Conference of the Cognitive Science Society, New York, NY, 270–275.

**Conflict of Interest:** 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 © 2019 Jost, Brill-Schuetz, Morgan-Short and Christiansen. 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) and the copyright owner(s) 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.

# Do Changes in Language Context Affect Visual Memory in Bilinguals?

#### Scott R. Schroeder\*

Department of Speech-Language-Hearing Sciences, Hofstra University, Hempstead, NY, United States

Language is often present when people are encoding visual memories. For bilinguals, this language context can have different forms (i.e., Language A, Language B, or both Language A and B), and can change over the course of events. The current study examined whether a change in language context during a visual event or between visual events affects a bilingual's ability to remember visual information. English-Spanish bilinguals and control participants encoded three lists of novel shapes amid different task-irrelevant language contexts. Following each list, participants completed a free recall test in which they drew the novel shapes they remembered. Results indicated that a change in language context between events, but not during events, affected visual memory. Specifically, the switch in language context between the second and third event (such as an English context in list 2 switching to a Spanish context in list 3) produced a reliable memory advantage for the English-Spanish bilinguals (relative to the control participants). The results offer preliminary evidence that task-irrelevant language context can influence a bilingual's ability to remember non-linguistic information, as well as further evidence for context effects and multi-sensory effects in memory.

#### Edited by:

Vitória Piai, Radboud University Nijmegen, Netherlands

#### Reviewed by:

Angela De Bruin, Basque Center on Cognition, Brain and Language, Spain Greg Poarch, University of Münster, Germany

#### \*Correspondence:

Scott R. Schroeder<EMAIL_ADDRESS>
#### Specialty section:

This article was submitted to Speech and Language, a section of the journal Frontiers in Human Neuroscience

> Received: 30 June 2019 Accepted: 27 September 2019 Published: 17 October 2019

#### Citation:

Schroeder SR (2019) Do Changes in Language Context Affect Visual Memory in Bilinguals? Front. Hum. Neurosci. 13:364. doi: 10.3389/fnhum.2019.00364 Keywords: language, memory, bilingualism, context, multisensory

### INTRODUCTION

Considering that we likely hear upwards of hundreds of words per hour (Hart and Risley, 2003), much of our encoding of visual memories occurs in the context of spoken language. For most people, this spoken language context consists of one or both of their two languages, as bilingualism is the norm worldwide (Grosjean, 2015). Despite the prevalence and despite considerable research on bilingual memory (e.g., Marian and Neisser, 2000; Pu and Tse, 2014; Basnight-Brown and Altarriba, 2016; Heredia and Cie´slicka, 2019), there appears to be no published research examining whether a bilingual's language context influences visual memory (or, more broadly, memory for non-linguistic information). The current study provides an initial examination, by assessing whether a change in language context during or between events influences English-Spanish bilinguals' ability to remember novel shapes.

As a framework to guide us, we can draw upon research from the event processing literature (for reviews, see Zacks and Swallow, 2007; Kurby and Zacks, 2008; Radvansky and Zacks, 2017). According to event processing work (such the Event Horizon Model and Event Segmentation Theory), people parse their ongoing experiences into events and subevents. In other words, people segment continuous activity (e.g., watching a movie or going to the grocery store) into parts and subparts. Possibly, event segmentation could be assisted by a change in language context (for example, a switch from English into Spanish). Specifically, a change in language context within

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an event could facilitate segmentation into subevents (i.e., ending one subevent and starting a new subevent), and a change in language context between events could facilitate segmentation into separate events (i.e., ending one event and starting a new event; see **Figure 1** below for a depiction of these two possibilities). As event segmentation is highly correlated with later event memory (Kurby and Zacks, 2008; Swallow et al., 2009; Sargent et al., 2013), changes in language context over the course of events could affect (even improve) event memory. These two possibilities—i.e., within-event and between-event changes in language context affecting visual event memory—are now fleshed out, with the within-event change discussed first and the between-event change discussed second.

How could a change in language context within an event boost visual memory? In other words, why might visual memory be enhanced when there is a switch in language context at one or more points during the course of a visual event? Theories of event processing, such as the Event Horizon Model, posit that more subevents (each with fewer elements) will lead to better memory than fewer subevents (each with more elements; Radvansky, 2012; Pettijohn et al., 2016). Consistent with this hypothesis, recent work found that memory (e.g., remembering word lists) was improved when the encoding event contained a segmenting cue (e.g., walking through a doorway from one room to another, or closing and then opening a computer window), which divided the encoding event into subevents (Pettijohn et al., 2016). Furthermore, more segmenting cues (and thus more subevents) led to better memory. The explanation is that segmenting an event into subevents provides an organizational structure and breaks the to-be-remembered information into smaller (and thus easier to remember) chunks. Following from this research, the first hypothesis assessed in the current study is that changes in language context within a visual event (thereby creating subevents) will enhance a bilingual's visual memory.

It is also possible that a change in language context between visual events could boost visual memory (the second hypothesis). This hypothesis is rooted in the well-established finding that, when multiple similar events occur over time, there can be proactive interference from the first event to subsequent events, leading to worse memory for subsequent events (than would otherwise be observed; Postman et al., 1968; Anderson and Neely, 1996; Kane and Engle, 2000). In other words, if the first event and second event are similar, memory for the second event can be hindered. However, evidence suggests that proactive interference can be reduced if there is a change in context between the first event and the second event (or subsequent events; Sahakyan and Kelley, 2002; Pastötter and Bäuml, 2007; Bäuml and Kliegl, 2013). With the first and second events having distinct contexts, presumably the two events become easier to differentiate, thereby reducing competitive interference. Extending this line of thinking to language contexts in bilinguals, if the language context (e.g., English) in the first event differs from the language context (e.g., Spanish) in the second event, then proactive interference from the first event to the second event may be diminished. There is some evidence consistent with this hypothesis, as studies assessing word-list memory in bilinguals have shown that a language switch between lists (e.g., list 1 consisting of English words and list 2 consisting of Spanish) can reduce proactive interference and improve memory for list 2 (Goggin and Wickens, 1971; Dillon et al., 1973; Francis, 1999). The current study extends this work on verbal memory to visual memory, by examining whether a change in language context between events can enhance a bilingual's visual memory (the second hypothesis of the study).

As an initial exploration of potential language context effects on visual memory in bilinguals, the current study asked English-Spanish bilinguals and controls (i.e., participants who did not know both English and Spanish) to encode three lists of novel shapes, with a free recall drawing test following each list. During the visual encoding of the shapes, a language context was present (i.e., each new shape was introduced with the phrase ''this drawing looks like this'' in either English or Spanish). The language context was entirely in English for one list of shapes (i.e., the English-Only Context), entirely in Spanish for a second list (i.e., the Spanish-Only Context), and partly in English and partly in Spanish for a third list (i.e., the English-Spanish Context), with the order of these lists counterbalanced across participants.

The first hypothesis—i.e., that a change in language context within an event might boost a bilingual's visual memory—predicted better recall performance for the English-Spanish bilinguals in the English-Spanish Context (as this context involved a within-event language change from English to Spanish to English) relative to the English-Only and Spanish-Only Contexts (as these contexts did not involve a within-event language change) and relative to the control participants (who had a less-comprehensible change in language context). The second hypothesis—i.e., that a change in language context between visual events might boost a bilingual's visual memory—predicted reduced proactive interference from the first list of shapes to the subsequent lists of shapes (i.e., lists 2 and 3) for the English-Spanish bilinguals, because the paradigm entailed a change in language context between each list (i.e., from list 1 to list 2 to list 3). This hypothesis might thus result in the English-Spanish bilinguals having a non-significant decline in recall performance from list 1 to subsequent lists (lists 2 and 3), as well as better performance on lists 2 and 3 relative to control participants (who had a less-comprehensible change in language context). The control participants may also benefit from a change in language context within and between events, despite not knowing one of the languages, though this benefit may be smaller.

#### MATERIALS AND METHODS

#### Participants

Seventy young adults (mean age = 20.41 years; gender = 41 female, 29 male) were included. Participants consented to participate in the experimental protocol, and the protocol was approved by the ethics board at Hofstra University. Participants were categorized as English-Spanish Bilinguals (N = 38) or Controls (N = 32) based on a post-experiment questionnaire completed by participants. If participants listed both English and Spanish as languages they have knowledge

of, then they were placed into the English-Spanish Bilingual group; if they did not list both English and Spanish, then they were placed into the Control group (this atypical group assignment process, in which participants were post hoc assigned to groups rather than in the recruitment phase, was chosen because it reduced the likelihood that participants and experimenters would guess their group and the purpose of the experiment).

Demographic information on the English-Spanish Bilinguals and Controls is provided in **Table 1**. Specifically, **Table 1** provides descriptive statistics for Age, Gender, English Proficiency (selfrated receptive proficiency in English on a 0-low to 10-perfect scale), English AoA (age at which participant first started learning English), English Use (% of time participant currently uses English when they are using a spoken language), Spanish Proficiency (self-rated receptive proficiency in Spanish on a 0-low to 10-perfect scale), Spanish AoA (age at which participant first started learning Spanish), Spanish Use (% of time participant currently uses Spanish when they are using a spoken language), and L2 Proficiency (self-rated receptive proficiency on a 0-low to 10-perfect scale in their second most proficient language). Note that L2 Proficiency was set to 0 in participants who did not list a second language.

#### TABLE 1 | Participant demographic information.

<sup>∗</sup>Note that Language Proficiency, AoA, and Use data are missing for one Control participant.

For the 38 English-Spanish Bilinguals, English was the L1 for 33 of the participants, the L2 for 4, and the L3+ for 1, whereas Spanish was the L1 for 2 of the participants, the L2 for 19, and the L3+ for 17. Note that L1, L2, and L3+ designations were determined by proficiency. In the case of a tie in proficiency, AoA was used to break the tie; if the tie remained, English was given priority because of the English-dominant context in which the participants resided. Of the 38 English-Spanish Bilinguals, 13 only listed English and Spanish as languages they know, whereas 25 listed more than English and Spanish.

Among the 32 Controls, five only listed English, whereas 27 listed more languages than English. English was the L1 for 28 of the Controls, the L2 for 3, and the L3+ for 1. The Controls listed a wide variety of languages, including Romance languages (i.e., a language that derived from Latin, such as French, Portuguese, Italian, Romanian, and Catalan). Nineteen of the Controls listed knowledge of a Romance language. Possibly, knowledge of a Romance language could lead to partial understanding of the Spanish that was heard in the experiment, thereby affecting recall performance. However, the Romance Controls and Non-Romance Controls patterned similarly on the key finding reported in the Results section below. That is, both groups showed a clear proactive interference pattern (recall percentage for Romance Controls: List 1 = 53%, List 2 = 48%, List 3 = 41%; recall percentage for Non-Romance Controls: List 1 = 49%, List 2 = 45%, List 3 = 42%).

Note that the use of the term ''bilingualism'' in the current study is based on the inclusive and minimalist definition by Mackey (1962): a bilingual is a person who has ''the ability to use more than one language.'' However, given that bilingualism is a label with ''open-ended semantics'' (Baetens Beardsmore, 1982) and many definitions, some readers of the current study might have a stricter definition of bilingualism; in such a case, ''second language learners'' would be a more suitable label for the English-Spanish speakers.

#### Procedure

The memory task involved encoding three lists of novel shapes, with a drawing-based free recall test following each list. Each of the three lists had a different language context: (1) English-Only Context; (2) Spanish-Only Context; and (3) English-Spanish Context. The order of the three language contexts was counterbalanced across participants. Participants were told not to be concerned with the language context (rather, they should be concerned with memorizing the novel shapes). The specifics of encoding and retrieval are provided below.

#### Encoding

In each of the three encoding lists, participants were presented with 12 drawings of novel shapes. Three sets of 12 drawings were created for the experiment, and each set appeared with each of the three lists (List 1, List 2, List 3) and with each of the three language contexts (English-Only Context, Spanish-Only Context, English-Spanish Context) a similar number of times.

The language context was created by introducing each novel shape with the phrase: ''This drawing looks like this'' (the phrase in Spanish is ''Este dibujo se ve así.''). Both the English and Spanish phrase were recorded in the same voice, by an English-Spanish bilingual speaker. In the English-Only Context, the English phrase was used to introduce each (and every) shape, and likewise, in the Spanish-Only Context, the Spanish phrase was used to introduce each (and every) shape. In the English-Spanish Context, the English phrase was used to introduce shapes 1 through 4, the Spanish phrase was used to introduce shapes 5 through 8, and the English phrase was used to introduce shapes 9 through 12. There were thus two language switches rather than one, because previous work indicated that two segmenting cues (and thus three subevents) led to better memory than one segmenting cue (and thus two subevents; Pettijohn et al., 2016).

The phrase ''This drawing looks like this'' was heard during the 4,000 ms interstimulus interval before each shape appeared. After the 4,000 ms interstimulus interval, the shape appeared in the center of the screen for 3,000 ms. **Figure 2**, on the left side, provides a visual depiction of the encoding process.

Before each encoding list, participants were instructed to learn the novel shapes for a memory test but not to be concerned with the language context. Specifically, the instructions were: ''You are going to see a string of abstract images. Try to remember as many images as you can; you will be asked to draw them after the recording ends. You will also hear someone talking in English or Spanish; you can ignore the person talking, as you will not have to remember what they said or what language they were using.''

#### Retrieval

Immediately after each encoding list, participants were asked to perform a free recall test in which they were to draw all of the shapes they remembered from the preceding list of 12 shapes. The recall sheet that was used can be seen on the right side of **Figure 2**. The recall sheet reads: ''Please draw all of the images that you remember. You will not use all of the boxes.'' Participants were given an unlimited amount of time to complete the free recall test.

After completing the memory task, participants filled out the post-experiment language and demographic questionnaire. The memory task data were coded by a research assistant who was blind to the participant's group and to the purpose of the experiment. The coding entailed matching each of the participant's drawings to one of the drawings in the target list. If the drawing could be exclusively matched to a single drawing in the target list (even if some minor details were missing), the participants received credit for that drawing; however, if the drawing could not be matched to any drawings, could be matched to multiple drawings, or could be matched to a drawing in a non-target list, the participant did not receive credit.

Consistent with the values of open science, the raw visual memory data, the recall scores, and the relevant questionnaire data are freely available to the public through the Open Science Framework at the following web address: https://osf.io/f5wrh/. All other information and stimuli will be willingly provided by the author.

#### RESULTS

### A Change in Language Context Within an Event

To assess the first hypothesis (i.e., that a change in language context within an event might help visual memory in bilinguals), we can compare recall when there was a change in language context within an event (i.e., the English-Spanish Context) to recall when there was not (i.e., the English-Only Context and

the Spanish-Only Context) in the English-Spanish Bilinguals and the Controls. These data are displayed in **Figure 3** below. As can be seen in **Figure 3**, the mean percentage of shapes recalled for the English-Spanish Bilinguals was not higher when there was a change in language context within an event (i.e., the English-Spanish Context) vs. when there was not; in fact, the opposite pattern was seen. Furthermore, English-Spanish Bilinguals' recall when there was a within-event language context change (i.e., the English-Spanish Context) appears to be very similar to that of Controls' recall. Thus, by visual inspection, the data clearly do not support the hypothesis that a change in language context within an event helps visual memory in bilinguals.

Two statistical tests were conducted to assess the first hypothesis: a traditional ANOVA and a generalized linear mixedeffects model.

#### ANOVA

The ANOVA was a 3 × 2, with Language Context (English-Spanish Context vs. English-Only Context vs. Spanish-Only Context) as a within-subjects independent variable, Group (English-Spanish Bilinguals vs. Controls) as a between-subjects independent variable, and mean percentage of shapes recalled as the dependent variable. The ANOVA yielded a non-significant main effect of Language Context, F(2,136) = 1.06, p = 0.35, partial η <sup>2</sup> = 0.02, a significant main effect of Group, F(1,68) = 4.59, p = 0.04, partial η <sup>2</sup> = 0.06, and a non-significant interaction between Language Context and Group, F(2,136) = 2.13, p = 0.12, partial η <sup>2</sup> = 0.03. The significant main effect of Group reflects an advantage for the English-Spanish Bilinguals, but this advantage seems to be due mostly to enhanced performance when there was no change in language context within an event, which goes against the hypothesis.

#### Mixed-Effects Model

A generalized linear mixed-effects model yielded similar results. The model consisted of Group and Language Context as fixed effects and Participant as a random effect (on the intercept). The model was computed using the glmer function in R, with the fixed effects sum coded, and with significance assessed through an Analysis of Deviance Table (Type III Wald chi-square

tests). There was a non-significant main effect of Language Context, χ 2 (2) = 1.73, p = 0.42, a significant main effect of Group, χ 2 (1) = 4.62, p = 0.03, and a trending interaction between Language Context and Group, χ 2 (2) = 5.39, p = 0.07.

### A Change in Language Context Between Events

To assess the second hypothesis (i.e., that a change in language context between events might help visual memory in bilinguals), we can compare recall when there was a change in language context between events (i.e., Lists 2 and 3) to recall when there was not (i.e., List 1) in the English-Spanish Bilinguals and the Controls. These data are shown in **Figure 4** below. A visual inspection of **Figure 4** reveals a consistent decline in recall for the Controls from List 1 to List 2 to List 3, i.e., a proactive interference effect. For the English-Spanish Bilinguals, however, the decline is less consistent, with List 3 showing the opposite of proactive interference and resulting in a noticeable difference between the English-Spanish Bilinguals and Controls. These visual impressions are partially consistent with the second hypothesis.

As with the first hypothesis, two statistical tests (i.e., a traditional ANOVA and generalized linear mixed-effects model) were used to assess the second hypothesis.

#### ANOVA

The 3 × 2 ANOVA had List Number (List 1 vs. List 2 vs. List 3) as a within-subjects independent variable, Group (English-Spanish Bilinguals vs. Controls) as a between-subjects independent variable, and mean percentage of shapes recalled as the dependent variable. The ANOVA revealed a significant main effect of List Number, F(2,136) = 3.37, p = 0.04, partial η <sup>2</sup> = 0.05, reflecting a proactive interference effect from List 1 to List 2 to List 3, and a significant main effect of Group, F(1,68) = 5.13, p = 0.03, partial η <sup>2</sup> = 0.07, reflecting that English-Spanish Bilinguals had better recall overall than Controls. Crucially, there was also a significant interaction between List Number and Group, F(2,136) = 3.79, p = 0.03, partial η <sup>2</sup> = 0.05.

To follow up the interaction, Bonferroni-corrected t-test comparisons among lists (i.e., List 1 vs. List 2, List 1 vs. List 3, and List 2 vs. List 3) were conducted for both English-Spanish Bilinguals and Controls. The only comparison that survived correction for multiple comparisons was List 1 vs. List 3 in Controls (p = 0.01), reflecting a significant decline in performance from List 1 to List 3 (i.e., a proactive interference effect) for Controls (but not for English-Spanish Bilinguals). The decline for the Controls in List 3, in conjunction with a reversal pattern for English-Spanish Bilinguals, appeared to create a sizable difference between groups in List 3 (but not Lists 1 and 2). To assess statistical significance, Bonferroni-corrected t-tests compared groups on each of the 3 lists, with the only significant difference emerging on List 3 (p = 0.003).

#### Mixed-Effects Model

Next, a generalized linear mixed-effects model was conducted, with Group and List Number as fixed effects and Participant as a random effect (on the intercept). The generalized linear mixedeffects model allows us to determine if the crucial interaction

between Group and List Number could be replicated with a different type of analysis and with an analysis that accounts for the random effect of participants. The model was computed using the glmer function in R. The fixed effects were sum coded, and statistical significance was determined through an Analysis of Deviance Table (Type III Wald chi-square tests). The analysis yielded a trending main effect of List Number, χ 2 (2) = 5.01, p = 0.08, a significant main effect of Group, χ 2 (1) = 4.60, p = 0.03, and, critically, a significant interaction between List Number and Group, χ 2 (2) = 6.54, p = 0.04.

#### Additional Analyses

Analyses were then conducted in order to rule out alternative explanations for the finding of superior recall for English-Spanish Bilinguals relative to Controls on List 3 (resulting from a lack of proactive interference). It seemed possible that the high recall was due, not to the English-Spanish bilingualism per se, but either to: (1) bilingualism more generally; or (2) by chance to the order in which groups completed the lists (given the atypical group assignment process). This first alternative explanation was excluded as a likely possibility because English-Spanish Bilinguals and Controls did not differ in their second language proficiency, t(67) = 1.03, p = 0.31, and second language proficiency did not correlate with recall on List 3 (r = 0.03, p = 0.81). The second alternative explanation was also excluded as a likely possibility, as a log-linear analysis of a 3-way contingency table of Group (English-Spanish Bilinguals vs. Controls), Language Context (English-Only Context vs. Spanish-Only Context vs. English-Spanish Context), and List Number (List 1 vs. List 2 vs. List 3) revealed no significant or near-significant interaction between Group, Language Context, and List Order, G <sup>2</sup> = 2.04, df = 12, p = 0.99 (this contingency table is represented in **Table 2** below). In other words, despite the atypical group assignment process, the two groups were exposed to the language contexts in a similar order.

In a final, exploratory analysis, a potential effect of the initial language context (i.e., English vs. Spanish) on subsequent memory performance was assessed. That is, did starting in English or in Spanish on List 1 affect subsequent recall for the English-Spanish Bilinguals? To assess this question, English-Spanish Bilinguals who started on the English-Only Context (i.e., English-starters; N = 14) and English-Spanish Bilinguals who started on the Spanish-Only Context (i.e., Spanish-starters; N = 13) were compared in their performance on the subsequent single-language context (i.e., Spanish for the English-starters and English for Spanish-starters) and the English-Spanish Context

Note. Each cell contains the number of participants who were exposed to a given language context in a given list order. For example, 14 of the 38 English-Spanish Bilinguals completed the English-Only Context in the first list.

(Eleven started on the English-Spanish Context and were thus not included in this analysis). The English-starters had a mean recall percentage of 53.60% (SD = 12.87%) on the singlelanguage context and 41.07% (SD = 12.85%) on the English-Spanish Context, whereas the Spanish-starters had a mean recall percentage of 53.85% (SD = 20.30%) on the single-language context and 53.21% (SD = 25.58%) on the English-Spanish Context. Thus, numerically, the Spanish-starters performed better than the English-starters on the English-Spanish context. However, the interaction between Group (English-starters vs. Spanish-starters) and Language Context (single-language context vs. English-Spanish Context) did not reach significance in either an ANOVA, F(1,25) = 2.49, p = 0.13, partial η <sup>2</sup> = 0.09, or a generalized linear mixed-effects model with Participant as a random effect (same model details as the above mixed-effects models), χ 2 (1) = 2.32, p = 0.13.

### DISCUSSION

With research on event processing as a guiding theoretical framework, the current study served as a preliminary examination into how changes in the ambient linguistic environment might influence visual memory in bilinguals. Specifically, the study assessed whether a shift in language context within an event (hypothesis 1) or between events (hypothesis 2) enhances a bilingual's visual memory, with the results providing partial initial empirical support for hypothesis 2 (but not hypothesis 1). In partial support of hypothesis 2, the control participants had a consistent downward recall trajectory from the first list to the second list to the third list (i.e., a proactive interference effect), whereas the English-Spanish bilinguals did not have a decline from the second list to the third list (resulting in a recall advantage on the third list for the English-Spanish bilinguals relative to the controls), presumably because of the change in language context between lists. Thus, while merely preliminary, the results suggest that the ambient linguistic background may in some circumstances boost a bilingual's non-linguistic memory performance.

Although the results are consistent with hypothesis 2 (i.e., that a change in language context between events helps memory), they are only partially so, because the memory benefit emerged on the third list but not the second list. Why did the benefit emerge only on the third list? A plausible explanation is that by the onset of the third list, participants had been exposed to two different language contexts, thereby making it clear that the language context changes from list to list and could thus be used to differentiate lists. At the onset of the second list, with exposure to only one list-wide language context, participants did not know that language context would be varied across lists and that it could be used as a distinguishing element to reduce interference.

Notably, the memory benefit on the third list for the English-Spanish bilinguals appears to have been driven more by the single-language contexts (i.e., the English-Only and Spanish-Only Contexts) than the dual-language context (i.e., English-Spanish Context; see bottom of **Figure 4**). Why is this the case? It could be due to the single-language contexts being more distinct from the previous lists. The single-language contexts only share contextual commonalities with one of the previous lists, whereas the dual-language context shares contextual commonalities with both of the previous lists. With more dissimilarity, there is potentially less competition and better memory. A related explanation invokes languagedependent memory (Marian and Neisser, 2000; Marian and Fausey, 2006; Marian and Kaushanskaya, 2007), a phenomenon whereby a language context evokes memories that were encoded in that same language context. In the current paradigm, the single-language contexts would only cue memories of a subset of the previously encoded shapes, whereas a dual-language context would cue memories of all previously encoded shapes, potentially creating more interference.

While there was support for the second hypothesis, there was no support for the first hypothesis. Why did the results fail to support the first hypothesis? That is, why did a within-event language context change not increase memory performance? One possibility is that this benefit is restricted to high proficiency (and high use) bilinguals. Spanish proficiency was low (as was current Spanish use) for many of the English-Spanish bilinguals in the current study, as can be gleaned from the Spanish proficiency (and Spanish use) mean and standard deviation in **Table 1**. However, an exploratory correlation analysis reveals no link between Spanish proficiency and recall performance in the English-Spanish Context (i.e., the within-event context change condition) for the English-Spanish bilinguals (Pearson'sr = 0.02), suggesting that the low proficiency of many of the bilinguals did not prevent support for hypothesis 1 from emerging. Nevertheless, a follow-up study with high proficiency (and high use) bilinguals is warranted. A second possibility is that, while proficiency may not be especially relevant, code-switching behavior may be, and the potential memory enhancement from a within-event language switch may be restricted to bilinguals who code-switch frequently. A third possibility is that bilinguals incurred a cognitive processing cost when a withinevent language switch occurred; that is, bilinguals may have deployed cognitive control resources to suppress the previous language (Philipp and Huestegge, 2015; Olson, 2017; but see Declerck et al., 2019), resulting in fewer resources available for memory encoding. A fourth possibility relates to the strength of the language context; perhaps the ambient linguistic context needs to be stronger and may even need to include expressive language in addition to receptive language. A fifth and final possibility is that there is a benefit to a within-event language switch, but that it was masked by a potential benefit of the single-language English-Only and Spanish-Only contexts. In other words, a consistent and meaningful context in the form of a single-language context may have aided encoding, which concealed a benefit that may also be derived from a language switch. As this list shows, there are many possibilities for why a within-event language context change effect did not manifest in the current paradigm, rendering this study preliminary and warranting additional studies.

Given that this study served as merely an initial foray into this research topic, there were several limitations (four of which are noted here) that should be addressed with future research. One shortcoming is the limited data on the linguistic backgrounds of the bilinguals (such as whether they code-switch often and are objectively proficient in the two languages). A second shortcoming is the absence of repeated language contexts (such as an English-Only Context followed by an English-Only Context) and a no-language context. A third shortcoming is that cognitive abilities, such as IQ and working memory, were not measured and thus may have differed between groups. A fourth shortcoming is that the retrieval task of drawing shapes was not completely language-free, as instructions were provided in English.

Despite these limitations, the current work provides initial data suggesting that a bilingual's non-linguistic memory can be influenced (and even boosted) by a subtle and task-irrelevant

#### REFERENCES

linguistic context. On a practical level, these data imply a possible way to enhance memory, such as when studying for tests. Potentially, studying for a course's first exam in one language context and for the second exam in a different language context could prove beneficial. On a theoretical level, these data provide further evidence that memory is influenced both by context (Smith and Vela, 2001) and by multi-sensory audiovisual interactions (Thelen et al., 2015). More broadly, the current data underline the tight link between two of our most cherished mental abilities—language and memory.

#### DATA AVAILABILITY STATEMENT

The data are available through the Open Science Framework at the following web address: https://osf.io/f5wrh/.

#### ETHICS STATEMENT

The studies involving human participants were reviewed and approved by Hofstra University Institutional Review Board. The patients/participants provided their written informed consent to participate in this study.

#### AUTHOR CONTRIBUTIONS

SS conceived the study, designed the study, analyzed the data, wrote and revised the manuscript.

(New York, NY: Springer), 147–184. doi: 10.1007/978-1-4614- 9218-4\_8

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

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## Bridging the Gap Between Second Language Acquisition Research and Memory Science: The Case of Foreign Language Attrition

Anne Mickan1,2\*, James M. McQueen1,3 and Kristin Lemhöfer <sup>1</sup>

<sup>1</sup>Donders Institute for Brain, Cognition and Behaviour, Radboud University, Nijmegen, Netherlands, <sup>2</sup> International Max Planck Research School for Language Sciences, Max Planck Institute for Psycholinguistics, Nijmegen, Netherlands, <sup>3</sup>Max Planck Institute for Psycholinguistics, Nijmegen, Netherlands

#### Edited by:

Melissa Duff, Vanderbilt University Medical Center, United States

#### Reviewed by:

Gulsen Yilmaz, Humboldt University of Berlin, Germany Claudia Peñaloza, Boston University, United States

> \*Correspondence: Anne Mickan<EMAIL_ADDRESS>
#### Specialty section:

This article was submitted to Speech and Language, a section of the journal Frontiers in Human Neuroscience

> Received: 27 June 2019 Accepted: 23 October 2019 Published: 13 November 2019

#### Citation:

Mickan A, McQueen JM and Lemhöfer K (2019) Bridging the Gap Between Second Language Acquisition Research and Memory Science: The Case of Foreign Language Attrition. Front. Hum. Neurosci. 13:397. doi: 10.3389/fnhum.2019.00397 The field of second language acquisition (SLA) is by nature of its subject a highly interdisciplinary area of research. Learning a (foreign) language, for example, involves encoding new words, consolidating and committing them to long-term memory, and later retrieving them. All of these processes have direct parallels in the domain of human memory and have been thoroughly studied by researchers in that field. Yet, despite these clear links, the two fields have largely developed in parallel and in isolation from one another. The present article aims to promote more cross-talk between SLA and memory science. We focus on foreign language (FL) attrition as an example of a research topic in SLA where the parallels with memory science are especially apparent. We discuss evidence that suggests that competition between languages is one of the mechanisms of FL attrition, paralleling the interference process thought to underlie forgetting in other domains of human memory. Backed up by concrete suggestions, we advocate the use of paradigms from the memory literature to study these interference effects in the language domain. In doing so, we hope to facilitate future cross-talk between the two fields and to further our understanding of FL attrition as a memory phenomenon.

Keywords: foreign language attrition, forgetting, retrieval-induced forgetting, interference, competition, second language acquisition, memory

#### INTRODUCTION

In 2016, more than 60% of adult European citizens were able to speak at least one foreign language (FL; European Commission—Eurostat, 2016). With multilingualism on the rise, learning foreign languages (FLs) is so common these days, it is often taken for granted. Yet, regardless of how ordinary it might seem, mastering a new language is and always will be an immensely complex task. Being able to formulate sentences in any language requires knowledge of its words and grammatical structures, all of which have to first be encoded, and then consolidated and integrated into long-term memory. All of these processes are common to other types of learning as well and are ultimately underpinned by the same fundamental memory processes. Surprisingly, despite the obvious overlap between second language processing and memory function, the empirical investigations of the two have often gone on in parallel; and so for a long time the fields of second language acquisition (SLA) and memory science developed in isolation from each other<sup>1</sup> . This is also true for the study of FL attrition, which investigates the phenomenon of forgetting a previously mastered FL. While it is not new to apply memory theories of forgetting and their corresponding paradigms to (FL) attrition, they have, as we shall argue, not been used to their full potential. Taking FL attrition as an example, we will posit that both SLA and human memory could benefit from more cross-talk. In doing so, we encourage future research exploiting parallels between the two fields.

#### Previous Research on Foreign Language (FL) Attrition

In the past 50 years, researchers have gone to great lengths to document language forgetting. Most of this research has been directed towards first language (L1) attrition in migrants (for reviews on L1 attrition, see Köpke and Schmid, 2004; Schmid, 2016). Much less work has been dedicated to FL attrition, the forgetting of a language learned later in life (for an overview, see Schmid and Mehotcheva, 2012). The present article will focus on this latter type of attrition, partly because it is a less well studied and hence less well-understood type of attrition; but also because, as will become apparent later on, the approach we are advocating in this article is most directly applicable to the FL attrition context.

FL forgetting often first manifests in a decrease in fluency and lexical diversity in the FL (Bardovi-Harlig and Stringer, 2010). Consequently, the majority of studies on FL attrition have focused on the lexicon (i.e., vocabulary), leaving (morpho- ) syntax and phonology aside (but see for example, Berman and Olshtain, 1983; Hedgcock, 1991; Dugas, 1999; Tomiyama, 2008). Given this bias in the existing literature, most examples given below will pertain specifically to lexical FL attrition, though we will speculate about the applicability of our proposed approach to other types of attrition as well (see ''Going Beyond Foreign Language Vocabulary Attrition'' section).

Based on the existing FL attrition literature, forgetting seems to set in very quickly after one stops using a FL; yet it then gradually levels off, with the most basic vocabulary apparently preserved in so-called ''permastore'' (Bahrick, 1984). It furthermore appears that productive skills deteriorate faster than receptive skills (e.g., Bahrick, 1984; De Groot and Keijzer, 2000), and that one tends to first lose the information learned last (or possibly what has been consolidated or practiced the least; i.e., the ''regression hypothesis (RH)''; e.g., Cohen, 1986; Olshtain, 1989; Kuhberg, 1992; see ''Discussion and Directions for Future Research'' section for a more in-depth discussion of this hypothesis and its alternative formulations). Next to those commonalities, attrition differs heavily from person to person. Exactly how severe and fast the attrition process is depends on a variety of factors. Bahrick's (1984) study on schoollearned Spanish, for example, showed that those individuals with the highest Spanish proficiency before attrition onset were least affected by forgetting (see also Weltens, 1988; Murtagh, 2003; Mehotcheva, 2010). Age at attrition onset (Olshtain, 1989; Bardovi-Harlig and Stringer, 2010) as well as language usage and exposure patterns (e.g., Mehotcheva, 2010) are also believed to play a role in determining the course of FL attrition: the earlier one stops learning the FL and the less exposure one has to it afterward, the more likely one is to suffer from attrition in that language. Finally, one's attitude towards the target language as well as motivation to maintain it is also believed to influence its attrition rate (e.g., Mehotcheva, 2010). Research on especially the latter two variables' role in attrition, however, has often yielded contradictory results (see Schmid and Mehotcheva, 2012), thus calling for more research into the determinants of attrition.

Interestingly, in most cases FL attrition (just as in fact any type of attrition) appears to be temporary and reversible: while one may not consciously recall the words learned in French class in high school, studies have demonstrated that relearning seemingly lost FL vocabulary is much easier and faster than learning new FL vocabulary from scratch (e.g., Hansen et al., 2002; de Bot et al., 2004). Such relearning advantages indicate residual storage of the purportedly ''forgotten'' words and thus speak against complete loss of memory traces. Attrition, like any other kind of forgetting, is thus best understood as a performance problem, characterized by accessibility difficulties rather than actual loss (Sharwood Smith, 1989).

Relatedly, it should be noted that observed FL attrition rates depend heavily on how the FL knowledge is tested: while attriters may be unable to freely recall and produce a word, they might still be able to recognize the word in a lexical decision task or other recognition-based tests. In other words, as mentioned earlier, productive recall failure appears to precede recognition inability. In earlier studies on FL attrition, the focus was often on receptive vocabulary knowledge, as this was thought to give the clearest picture of a person's existing FL knowledge, but those studies often reported very little to no attrition even after years of no exposure (e.g., Weltens et al., 1989; Grendel, 1993). These null results stand in stark contrast to studies reporting significant attrition in productive recall tasks already within the first year of disuse (e.g., Bahrick, 1984; Mehotcheva, 2010). This distinction needs to be kept in mind in interpreting differences in attrition rates between populations and studies.

### Forgetting Due to Competition and Interference: A Domain-General Perspective

The above studies have made important contributions to our understanding of language attrition. It remains unclear, however, what exactly causes language forgetting, and thus which cognitive mechanisms underlie it. Forgetting is by no means limited to language though, and is, in fact, a rather pervasive phenomenon: we forget where we park our car, or what that distant friend's name was. Research on forgetting from a more domain-general perspective dates back to the 19th century and Ebbinghaus' research on the ease of learning and relearning nonsense-syllable sequences (Ebbinghaus, 1885, 1913). Ebbinghaus discovered that memory loss was not linear over time, but logarithmic

<sup>1</sup>We use the terms ''second'' and ''foreign'' language interchangeably in this article. Both refer to any language other than one's mother tongue (L1); that is any language learned later in life, be it a second (L2), third (L3) or even fourth foreign language. In using both terms we stick to common terminology in both ''second language acquisition'' as well as ''foreign language attrition'' research.

instead: most forgetting happens over the first minutes to hours and then gradually levels off; note that this resembles what Bahrick (1984) observed for the retention of school-learned Spanish. Ebbinghaus' work inspired many theories about the possible mechanisms behind forgetting (for an overview, see Ecke, 2004; Anderson, 2015). The probably most influential of these is interference theory. Rather than assuming that forgetting is a by-product of time (see decay theory, Thorndike, 1914), interference theory attributes forgetting to interference from related, competing memories. Essentially, it relies on the fact that memories that share a common retrieval cue (e.g., your car being the shared cue for its location today vs. yesterday) compete with one another for selection upon presentation of that cue, thus hindering future retrieval.

One example of forgetting by competition is retrieval-induced forgetting (RIF; Anderson et al., 1994). In a typical RIF study, participants first study a number of category-exemplar pairs (e.g., FRUIT-apple, FRUIT-banana, FURNITURE-table). This phase is followed by selective retrieval practice of some exemplars from some of the categories (FRUIT-banana, but not FRUITapple or FURNITURE-table). Finally, recall is tested for all originally studied pairs. Of course, recall is best for the practiced pairs (FRUIT-banana), but interestingly, it is worse for unpracticed exemplars from practiced categories (FRUIT-apple) compared to recall for unpracticed exemplars from unpracticed categories (FURNITURE-table). The mere act of retrieving information can thus hamper access to information related to the practiced material. RIF is typically attributed to executive control processes in the form of inhibition applied to competitors during the retrieval practice phase (e.g., to apple), making these suppressed competitors harder to retrieve at final test (e.g., Anderson, 2003; Bäuml et al., 2005; Román et al., 2009; though see Williams and Zacks, 2001; Raaijmakers and Jakab, 2013; for alternative explanations). RIF effects have been demonstrated with a wide variety of stimulus materials. It thus appears to be a generalizable phenomenon (for a review, see Storm et al., 2015).

### EXPLORING PARALLELS BETWEEN MEMORY AND SLA RESEARCH

Competition does not only exist between exemplars of a semantic category, but also between translation equivalents in different languages that share a common concept. When a speaker of English and Spanish wants to refer to a ''table,'' both Spanish ''mesa'' and English ''table'' will be activated and compete for selection. This between-language competition is well-known to affect (online) word production in bilinguals (e.g., Hermans et al., 1998; Colomé, 2001; for an overview, see Kroll et al., 2008). As in RIF, bilingual lexical access is often seen as a matter of executive control: it is assumed that in order to avoid unwanted language selection/production errors, speakers need to inhibit the non-target language during speaking. This, however, can, as an undesirable side effect, lead to later retrieval difficulties in the inhibited language (Green, 1998). In terms of competition for retrieval, translation equivalents (sharing the same concept) are thus similar to pairs of exemplars sharing one semantic category cue. Given this parallel, the question arises whether between-language competition is also a driving mechanism behind language forgetting, and thus whether the between-language competition observed during the short-term, online processing also has long-term ramifications.

### Between-Language Interference as a Mechanism Behind FL Attrition?

The idea that attrition is the result of complex interactions and competition between languages is not new. Sharwood Smith (1989) as well as Seliger and Vago (1991) already noticed how L1 attrition is influenced by the newly acquired FL (L2), for instance in the form of code switches to L2 while speaking in L1. This ''cross-linguistic influence hypothesis'' (Sharwood Smith, 1989) is also central to more recent approaches to attrition. Its ideas have been formally discussed, for example, within the context of Paradis' Activation Threshold Hypothesis (ATH, see Köpke, 2002; Gürel, 2004; Paradis, 2004, 2007). The ATH assumes that all items in the linguistic system, such as words, are interconnected and influence one another. Each item has an activation threshold (AT). Retrieving a word requires that its activation exceed its AT. The AT is lowered after successful retrieval but is increased again either gradually through disuse or through top-down inhibition during access of other, competing words (as is also believed to be the case in RIF; Anderson, 2003). A latter mechanism is a form of cross-linguistic influence since competing items will often be translation equivalents in other languages. Heightened ATs then lead to retrieval difficulties because more activation is needed to pass them. Ultimately, ATs can be so high that a word can no longer be accessed, and hence is ''forgotten'' until accessed again (e.g., during re-learning). For Paradis (L1 lexical), attrition is thus the result of a lack of stimulation of certain words, combined with more recent and frequent access of competing for translation equivalents<sup>2</sup> .

Applying ideas and frameworks like the ATH to attrition forms part of an increasing effort towards studying the phenomenon from a psycholinguistic perspective (see also Schmid and Köpke, 2017). Surprisingly though, only a handful of psycholinguistically-inspired attrition articles explicitly connect their ideas to memory theories of forgetting. In an effort to encourage more such cross-talk, Ecke (2004) summarized theories of forgetting from the memory literature and stressed their theoretical relevance and explanatory value for attrition (see also Köpke, 2004). While discussing multiple theories of forgetting, he identifies interference processes as the ''main contributor to attrition'' (Ecke, 2004; p. 337). We aim to build on Ecke's (and Paradis') contribution, but go one crucial step further: next to using memory theories of forgetting as a

<sup>2</sup>Paradis (2004) also distinguishes between declarative (i.e., explicit) and procedural (i.e., implicit) memory. Declarative memory encompasses knowledge of facts and events and is accessed consciously; procedural memory refers to memory for skills and is largely unconscious (Squire, 1992). Paradis (2004) assumes the language faculty is subserved by both these types of memory as well, with any language's vocabulary and the majority of FL grammar being instances of declarative memory, and L1 grammar mostly procedural (also see Ullman, 2001, 2004). For attrition, Paradis further speculates that declarative memory, and hence L1/FL vocabulary and FL grammar, will be more prone to interference and forgetting than aspects of procedural memory. The present article is on lexical FL attrition and thus concerns the declarative memory system only.

framework within which to think about attrition, we argue that an important added value of these theories are the experimental paradigms that have been developed to test them. The application of these paradigms to the study of (at least FL lexical) attrition forms a crucial addition to the available evidence on FL attrition. Via snapshots of FL ability at different time points, existing observational studies document merely the result, but not the process of attrition itself. Observed links between, for example, language use (as typically measured in questionnaires) and attrition are then purely correlational and do not indicate causal relationships. Traditional attrition studies thus cannot be taken as proof that any factor discovered in this manner is a driving force in attrition. The memory approach to the investigation of forgetting is quite different from the traditional attrition approach: experimental paradigms (e.g., the RIF paradigm) aim at inducing and thus simulating forgetting in a tightly controlled setting. To do so, cognitive psychologists typically manipulate the presence or absence of a presumed cause of forgetting (e.g., interference) while keeping all other potentially relevant factors (e.g., amount of studied materials) constant. By determining the conditions that do and do not lead to forgetting, this procedure allows for causal inference.

This experimental approach can be applied to language attrition. Retrieval of words in one language should induce retrieval difficulties, and thus ultimately forgetting of translation equivalents in another language. A handful of studies have put this hypothesis to test, among those a recent study by Mickan et al. (submitted). Participants first learned a set of new L3 Spanish words. A day later, interference was introduced: participants were asked to retrieve half of these newly learned words in either L1 Dutch or L2 English; the other half were not interfered with. Finally, after a 20-min delay, all originally learned words were tested again in Spanish. In line with predictions based on interference theory, participants were worse at recalling interfered words compared to not-interfered words. That is, retrieving translation equivalents in other languages made them forget (some of) the recently learned Spanish words. This interference effect was also visible in naming speed for the words that were still successfully remembered: it took participants longer to retrieve interfered compared to not-interfered words. In reaction times, this effect persisted in a follow-up Spanish test a week later, thus showing that interference has true long-term effects and establishing it as a plausible mechanism behind FL attrition.

Similar observations had previously been made for L1 attrition, for which Levy et al. (2007) had shown that retrieval practice in L2 Spanish impaired subsequent recall for L1 translation equivalents. For FL attrition, there are two corroborating studies with similar results. Bailey and Newman (submitted) tested L1 English learners of L2 Welsh and showed that participants were slower to recall newly learned Welsh words when these words had intermittently been retrieved in L1. Likewise, Isurin and McDonald (2001) found that memory for newly learned L2 Russian words was worse if participants had in between learned the same words in L3 Hebrew as compared to when no extra learning had taken place. Note though that neither Bailey and Newman (submitted) nor Isurin and McDonald (2001) allowed for consolidation of the newly learned Welsh or Russian L2 words: finding interference in these cases is less surprising given that the newly learned material had no chance to consolidate. Moreover, neither of these studies had a delay between ''interference'' and final recall, thus not providing evidence for long-term interference effects (for which a delay of at least 20 min is called for, following standard memory procedures; Anderson et al., 1994). Both these studies are thus somewhat more removed from real-world attrition scenarios and less convincingly link interference to long-term forgetting than Mickan et al. (submitted).

Delays of up to 1 week, as tested in Mickan et al. (submitted), might seem minuscule compared to the time delays of multiple months or even years that are typically reported in observational attrition studies. In experimental terms, however, it is quite remarkable for effects to persist for an entire week. While looking at longer time delays would be theoretically interesting for future studies, doing so only makes sense if: (1) it can be guaranteed that the participants are not re-exposed to the target language within that time; and (2) only if additional interference can be reliably quantified. If these two conditions are not met, the experimenter would no longer have the experimental control that makes the simulation approach so useful. What is more, it would be difficult to interpret the outcome of a longer time delay: additional interference through the intermittent use of other languages would happen equally often for items in the interference and no interference conditions, and so would wash the interference effect out. The experimentally induced interference effect might thus disappear with time, however, not necessarily because it is not long-lasting, but instead because of additional interference, the very mechanism that caused the effect in the first place. There is thus a logical limit to the length of the delays one can sensibly look at while maintaining experimental and explanatory control; and 1 week is arguably already stretching this limit.

Overall, while there is clearly a need for more studies to establish interference-based forgetting as a robust phenomenon in the language domain, the above-cited studies illustrate that using paradigms from the memory literature complements more traditional approaches to attrition, allows for causal rather than just correlational inferences and thereby advances our understanding of why we forget languages.

### DISCUSSION AND DIRECTIONS FOR FUTURE RESEARCH

We have argued that the use of memory paradigms for the study of attrition has a number of advantages over more traditional approaches. Simulating rather than observing attrition in real life makes it possible to control, isolate and manipulate possible determinants of the attrition process and assess their effect on retention rates. Most obviously, this includes manipulations of the interference phase as the phase during which attrition is (presumably) taking place. As a secondary question, Mickan et al. (submitted), for example, asked whether the type of interference matters: manipulating interference language between experimental groups, they found that another FL (L2 English) interfered more with L3 Spanish than the participants' dominant L1. Along similar lines, one might ask what the role of typological proximity or language distance is in driving attrition. Do two related languages interfere more with one another than two distant ones? For vocabulary, this question translates to a comparison of cognates (i.e., words that share meaning and form across languages) and non-cognates. Cognates have often, not surprisingly, been reported to be less affected by attrition than non-cognates (e.g., Weltens, 1988). This assumption is in line with interference theory: since cognates share form and meaning, there is no need to suppress the translation equivalent when retrieving a cognate in the target FL. One might even expect a boost for identical cognates given the form overlap. Often, however, words in typologically similar languages overlap only partially (e.g., ''table'' in English and ''Tafel'' in Dutch). It is unclear whether such non-identical cognates interfere more or less with each other than two non-cognate translation equivalents. This could be addressed in an experiment that compares interference effects for the two types of nouns. Given that, by definition, two typologically similar languages will have relatively more (nonidentical) cognates than two distant languages (Chiswick and Miller, 2005), stronger (or weaker) interference effects between non-identical cognates as compared to non-cognates would be evidence in favor of (or against) the hypothesis that two typologically close languages interfere more with one another than more distant languages.

Likewise, it would be interesting to test whether active use of other languages is necessary to induce forgetting, or whether mere passive exposure to other languages is enough. Evidence from memory studies seems to suggest that active retrieval and response generation (though not necessarily successful retrieval, Hellerstedt and Johansson, 2016) is necessary to induce RIF; passive exposure or even reading out loud of exemplar-pairs does not induce forgetting of related items (Anderson et al., 2000; Bäuml, 2002). It remains to be seen whether these findings generalize to the attrition context.

Memory paradigms might also help answer long-standing open questions regarding FL attrition. The RH is a case in point: in its original formulation, RH posits that we tend to forget first the information (e.g., words) we learned last (Jakobson, 1941). However, the order of acquisition itself might not actually matter as much as the degree of learning of a given word (i.e., ''best learned = last forgotten''; Hedgcock, 1991). In the real world, these two theories are almost impossible to tease apart: with more time for rehearsal and repetition, remotely learned words will be better encoded than recently learned words. To worsen matters further, the first words one learns in a new language tend to be the most frequent; later learned words or structures instead are usually less frequent, harder to learn, and possibly more vulnerable to forgetting because of their difficulty rather than order of acquisition. A lab study could disentangle these options by manipulating the acquisition order during the initial learning phase while keeping the amount of exposure (and thus the degree of learning) for each word—as well as subsequent interference—equal.

Another option would be to compare receptive and productive recall abilities. As mentioned in ''Previous Research on Foreign Language Attrition'' sections, it is generally assumed that productive loss precedes receptive loss. Support for this claim often comes from comparisons across studies, that is between different groups of participants and even different language combinations (though see Bahrick, 1984; De Groot and Keijzer, 2000; for exceptions). The above-reported studies (all testing productive recall with the exception of Bailey and Newman, submitted) could easily be adjusted to test both productive and receptive recall at final test (e.g., via a lexical decision test in addition to a picture-naming test) and hence could be used to directly compare the two. Finding that words that are already ''forgotten'' in productive tasks are still available to the participant in receptive tasks would be much more convincing proof of the claim that receptive knowledge outlasts productive recall ability than the cross-experiment comparisons that have often been the basis for this claim in the past.

Yet another possible future research avenue concerns manipulations of the level of FL proficiency reached prior to attrition onset. Higher ultimate attainment, as it is often called, has consistently been linked to better retention (see Schmid and Mehotcheva, 2012). Yet, it is unclear whether this means that highly proficient FL learners really attrite less, or whether they, in fact, attrite equally much in absolute terms, but are left with a larger vocabulary because they had a bigger lexicon to begin with (Bahrick, 1984, supports the latter). Most studies to date cannot disentangle these two options because they often do not have the necessary baseline measurement (with the exception of longitudinal studies, yet those tend to be underpowered). A simulation study might again help to disentangle the two: one could test two groups of participants, one as described above, and one with an extended initial learning session (possibly spread over multiple days and/or with an increase in the number of words to be learned) to simulate a higher FL proficiency level, while keeping the amount of interference constant. It should get harder to simulate attrition in the lab as FL proficiency increases if higher ultimate attainment really leads to less attrition. Crucially though, comparing the low and high attainment groups will reveal whether forgetting rates are comparable or actually different across different levels of ultimate FL attainment.

Finally, lab studies could be used to investigate individual differences in attrition. With a large enough pool of participants, there is bound to be variability in forgetting rates, even in an otherwise tightly controlled lab study. It would be interesting to test whether factors known to modulate RIF and interference resolution in bilingual processing also play a role in determining the rate of interference-induced FL attrition. An interesting case in point is executive/cognitive control ability, which has been found to be implicated both in bilingual processing (e.g., Linck et al., 2008) and RIF (e.g., Mall and Morey, 2013; though not always to same extent or even in the same manner, see Aslan and Bäuml, 2011). Traditional attrition studies have, to our knowledge, paid little attention to cognitive control ability. Should it turn out to be a reliable predictor of forgetting rates in the lab, it would merit investigation in large scale studies with real attriters; and might explain some of the residual variances that remain unexplained by the otherwise mostly socio-linguistic variables assessed in previous studies.

As these examples show, the possibilities using variations of memory paradigms are manifold. Of course, as with any approach, there are also downsides: using tightly controlled experiments clearly comes at the cost of ecological validity. Attrition is a complex, multi-faceted phenomenon, which is simplified in the above experiments. There are undoubtedly questions that our approach will not be able to answer (e.g., motivational/attitudinal aspects). Before looking at large complexities, however, one needs to understand the basic mechanisms. The power of lab studies lies in making exactly that possible: by simplifying matters and isolating individual factors, they can substantially contribute to the development of a cognitive theory of attrition, uncontaminated by the noise that is inevitable in observational studies. Of course, the mechanisms unraveled in the lab will then need to be verified by large-scale longitudinal studies with real attriters. Such studies need to keep detailed records of all possible determiners of attrition, like their participants' language usage patterns, for example, via questionnaires or more formal tasks at regular and short intervals (monthly at least). While it will remain challenging to recruit a large enough, homogenous sample of ''natural'' attriters, we would like to highlight the possibility of online testing nowadays. There are many types of measures that can be taken online (both receptive and productive tasks are possible), and one can much more easily reach a large number of people, which would ultimately allow for firmer conclusions if patterns emerge reliably. Hence, we do not propose that experimental studies should replace traditional ones. Instead, we see the two approaches as complementary and believe there should be a healthy balance between them.

### Going Beyond Foreign Language Vocabulary Attrition

#### Syntax

The present article focuses on FL lexical attrition. Yet, speaking a language requires much more than just mastery of its words. Similarly, attrition is by no means limited to the forgetting of vocabulary; grammatical structures have, for instance, also been found to attrite (e.g., Hansen, 1999; Tomiyama, 2008). It will be crucial to extend the current line of research to cover these other types of attrition as well. As a first step, one could look at grammatical gender, for which negative transfer and interference effects are well documented in online processing (e.g., Lemhöfer et al., 2008). One might ask whether retrieving L1 gender for a set of nouns (e.g., ''der Mond,'' masculine in German) interferes with and makes people forget just recently learned, but incompatible FL gender assignments (e.g., ''la luna,'' female in Spanish).

For more rule-governed aspects of grammar, the design might need some adjustments: the learning phase, for example, will most likely need to be longer, and include tasks other than just picture naming for participants to learn the rule. Moreover, the control (i.e., no-interference) condition will need to be carefully chosen: if the syntactic property is not item-specific (unlike grammatical gender), one would need to find a syntactic rule that is comparable in complexity, yet not in conflict with and thus not prone to interference from L1. This might prove challenging for some aspects of grammar. In such cases, one might need to resort to between-subject designs and compare a group that learns a conflicting rule with a group that learns the same rule but in a language which implements this rule similarly to their L1. Though somewhat more challenging, we think that extending our approach to syntax would be a very interesting line of research.

#### First Language Attrition

While almost all the above studies are concerned with FL attrition, Levy et al.'s (2007) research suggests that L1 attrition can also be experimentally induced. The design of a study on L1 attrition differs slightly from the FL attrition studies reported above though: there is no need for an initial learning phase in L1; one instead would start with a baseline L1 picture naming test. This baseline speed and accuracy measurement would then be followed by an interference phase that could consist of learning of some of the same words in a new FL. Finally, retrieval speed and accuracy would be measured again for all words in L1. While such a study is perfectly conceivable, it remains unclear how easily deeply engrained L1 knowledge can be interfered with. Even though Levy et al. (2007) observed worse L1 English recall rates after L2 Spanish retrieval practice, Runnqvist and Costa (2012) were later unable to replicate this finding. What is more, Levy et al. (2007) used a rather indirect measure of recall ability (rhyme-generation rather than picture naming), which possibly underestimated L1 productive knowledge. For successful L1 attrition induction, as measured in a final picture naming task, the interference phase might need to be longer, or spaced out over multiple days. Even if L1 attrition proves to be inducible in the lab though, it should be mentioned that the L1 words under investigation will have been learned in the wild and not under controlled circumstances. Hence, there will be limitations to the types of simulations one can run; some of the questions addressed in ''Going Beyond Foreign Language Vocabulary Attrition'' section will be impossible to implement for L1 attrition (e.g., disentangling the effects of order of acquisition vs. degree of learning of L1 words on L1 attrition rates).

### Bridging Between Memory and SLA—a Two-Way Street

Finally, we would also like to emphasize that the benefit of applying psychological theories of forgetting to the language attrition context is not a one-way street. Traditional memory paradigms often make use of artificial learning materials that are hardly representative of what people learn outside the laboratory (e.g., word lists, association pairs, or visual patterns). FL learning and forgetting offers a more realistic scenario to memory researchers to test their theories on. This advantage should not be overlooked given that the FL scenario is arguably as close to real-life as memory studies on the topic can get, while maintaining tight experimental control.

#### Concluding Remarks

We hope to have shown that the approach of using experimental paradigms from human memory research to study FL attrition is a promising avenue for future research. It provides a fresh look at FL attrition that allows for very different types of inferences than those supported by traditional observational studies. We believe that a sound mixture of both approaches is needed if we are to understand what it means to forget a FL. The field of FL attrition is only one example out of many in SLA research for which such interdisciplinary cross-talk is relevant (e.g., effects of testing, spacing and later

### REFERENCES

consolidation for FL vocabulary learning). We hope to have contributed our share to a productive bridging between SLA and memory science.

#### AUTHOR CONTRIBUTIONS

AM wrote and edited the manuscript. KL and JM provided feedback and edited the manuscript. All authors read and approved the submitted version.

#### FUNDING

This work was supported by an International Max-Planck Research School for Language Sciences PhD Fellowship awarded to the first author AM (Grant period: 2016–2020).

**Conflict of Interest**: 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 © 2019 Mickan, McQueen and Lemhöfer. 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) and the copyright owner(s) 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.

# Distinguishing Old From New Referents During Discourse Comprehension: Evidence From ERPs and Oscillations

#### Mante S. Nieuwland1,2 \*, Cas W. Coopmans1,3 and Rowan P. Sommers<sup>1</sup>

<sup>1</sup> Max Planck Institute for Psycholinguistics, Nijmegen, Netherlands, <sup>2</sup> Donders Institute for Brain, Cognition and Behaviour, Nijmegen, Netherlands, <sup>3</sup> Centre for Language Studies, Radboud University, Nijmegen, Netherlands

#### Edited by:

Melissa Duff, Vanderbilt University Medical Center, United States

#### Reviewed by:

Cybelle Marguerite Smith, University of Pennsylvania, United States Heather Dee Lucas, Louisiana State University, United States

\*Correspondence: Mante S. Nieuwland<EMAIL_ADDRESS>
#### Specialty section:

This article was submitted to Speech and Language, a section of the journal Frontiers in Human Neuroscience

Received: 17 July 2019 Accepted: 23 October 2019 Published: 14 November 2019

#### Citation:

Nieuwland MS, Coopmans CW and Sommers RP (2019) Distinguishing Old From New Referents During Discourse Comprehension: Evidence From ERPs and Oscillations. Front. Hum. Neurosci. 13:398. doi: 10.3389/fnhum.2019.00398 In this EEG study, we used pre-registered and exploratory ERP and time-frequency analyses to investigate the resolution of anaphoric and non-anaphoric noun phrases during discourse comprehension. Participants listened to story contexts that described two antecedents, and subsequently read a target sentence with a critical noun phrase that lexically matched one antecedent ('old'), matched two antecedents ('ambiguous'), partially matched one antecedent in terms of semantic features ('partial-match'), or introduced another referent (non-anaphoric, 'new'). After each target sentence, participants judged whether the noun referred back to an antecedent (i.e., an 'old/new' judgment), which was easiest for ambiguous nouns and hardest for partially matching nouns. The noun-elicited N400 ERP component demonstrated initial sensitivity to repetition and semantic overlap, corresponding to repetition and semantic priming effects, respectively. New and partially matching nouns both elicited a subsequent frontal positivity, which suggested that partially matching anaphors may have been processed as new nouns temporarily. ERPs in an even later time window and ERPs time-locked to sentence-final words suggested that new and partially matching nouns had different effects on comprehension, with partially matching nouns incurring additional processing costs up to the end of the sentence. In contrast to the ERP results, the time-frequency results primarily demonstrated sensitivity to noun repetition, and did not differentiate partially matching anaphors from new nouns. In sum, our results show the ERP and time-frequency effects of referent repetition during discourse comprehension, and demonstrate the potentially demanding nature of establishing the anaphoric meaning of a novel noun.

Keywords: anaphora and coreference resolution, EEG and ERP, time-frequency analysis, N400 and P600, gamma and theta activity, beta activity, old/new effect, lexical repetition

## INTRODUCTION

All nouns have a general meaning, maybe even multiple general meanings, but they acquire a particular, referential meaning when used to refer to someone or something in the world. This flexible use of language and memory yields incredible expressive power for communicating information about the world (e.g., Clark and Murphy, 1982; Martinich, 1985;

Gibson and Pearlmutter, 2011), but also harbors a potential mapping problem for language comprehenders: different words like 'martian' and 'alien' can have the same referent, and the same word can have different potential referents, such as 'the alien' when there are multiple aliens in the context. To examine how people solve such mapping problems, we compared electrophysiological brain responses [event-related potentials (ERPs) and oscillatory activity] to referring expressions that have either one, two or no suitable referent in the linguistic context and that may differ in form (and general meaning) from their referent.

Our study investigates the comprehension of expressions that refer to a previously mentioned referent in the discourse context, i.e., anaphoric reference to a linguistic antecedent (e.g., Garnham, 2001; Almor and Nair, 2007). Psycholinguistic theories stipulate the importance of general memory representations and processes during anaphor resolution (e.g., Garrod and Sanford, 1977; Gernsbacher, 1989; McKoon and Ratcliff, 1998; Myers and O'Brien, 1998). Such theories often distinguish an initial activation phase, wherein anaphors are thought to reactivate antecedents from a memory representation of the context (including the described referents), and a subsequent integration phase wherein the reactivated representation is integrated with the unfolding representation of the narrated event. Our main interest in this paper is antecedent activation, which is viewed as a memory-based process in which semantic and syntactic content of an anaphor serves as a memory cue to the antecedent. This process entails the recognition of the anaphor as an instantiation of the antecedent – even when they differ in linguistic form – through the computation of a similarity/identity relation between the two words. This computation gives the language system both great flexibility and speed, by enabling efficient reactivation of semantically complex concepts (e.g., 'Boris Johnson'), either by other complex concepts ('blonde haired Brexiteer') or by minimal-content pronouns ('he'). The ease with which people understand noun phrase anaphors depends on content overlap of the anaphor with the intended referent relative to other antecedents (e.g., Garrod and Sanford, 1977, 1982; Krahmer and Deemter, 1998; Almor, 1999; Van Gompel et al., 2004; Pyke, 2007). Repeated noun phrase anaphors are easier to resolve than anaphors that only partially match an antecedent (e.g., McKoon and Ratcliff, 1980; Tyler, 1983; Walker and Yekovich, 1987), e.g., 'the alien' referring to an alien/a martian<sup>1</sup> . An anaphor whose semantic content does not distinguish between antecedents, e.g., 'the alien' in a story about two aliens, is referentially ambiguous. A preceding determiner may already hint at whether the upcoming noun is anaphoric (e.g., Garrod and Sanford, 1977; Clark and Sengul, 1979; Garnham, 1989), with the definite determiners 'the' heralding an anaphoric noun phrase and the indefinite determiner 'a' heralding a novel, non-anaphoric noun phrase. However, definite noun phrases sometimes introduce a new referent (e.g., Heim, 1982; Fraurud, 1990; Garrod et al., 1994; Poesio and Vieira, 1998; Gundel et al., 2001; Pyke, 2007; Pyke et al., 2007a,b), and people can use the semantic content of a definite noun as a basis to introduce a novel referent when required, e.g., 'the alien' when the context only mentioned astronauts. This process is sometimes referred to as discourse updating (e.g., Burkhardt, 2006), which is related to, yet distinct from the integration process by which people process discourse-level meaning (e.g., Coopmans and Nieuwland, 2019). In other words, processes involved in noun phrase anaphor resolution must distinguish old from new referents, and may do so partly relying on memory processes (for a review and computational account, see Pyke, 2007). To address this issue, the current study investigates whether old and new noun phrase referents elicit distinct neural responses, as measured with ERPs and time-frequency analysis.

#### Noun Phrase Anaphors and ERPs

Noun phrase anaphors have been associated with several distinct ERP effects, in particular with modulations of the N400, the Late Positive Component (LPC), and the Nref effect. The N400 component is a negative ERP deflection that peaks approximately 400 ms after word onset and is maximal at centroparietal electrodes (Kutas and Hillyard, 1980). The N400 reflects semantic processing and its amplitude is modulated by the relationship between the meaning of a word and its context (Kutas and Hillyard, 1980, 1984; for review, see Kutas and Federmeier, 2011). Words whose meaning is easier to access based on the context typically elicit reduced N400 amplitude compared to words whose meaning is unrelated to the context (Kutas and Federmeier, 2011). Compatible with such findings, noun phrase anaphors that are either repeated from the context or that are contextually implied ('the conductor' in a context describing an orchestra) elicit reduced N400 amplitude compared to novel, unrelated noun phrases (e.g., Burkhardt, 2006, 2007). Such N400 modulations may reflect the ease with which the meaning of the anaphor is activated as a function of the context (e.g., Kutas and Federmeier, 2011), and need not reflect higher-level processes such as discourse updating or integration. While recent studies suggest that N400 activity can arise from a cascade of processes that activate and integrate word meaning with context into a sentence-level meaning (e.g., Baggio and Hagoort, 2011; Baggio, 2019; Nieuwland et al., 2019), some studies have failed to observe updating- or integration-related effects on the N400 and found them on a later positive-going ERP component, the LPC (e.g., Burkhardt, 2006, 2007; Delogu et al., 2019). For example, Burkhardt (2006) reported that contextually implied and novel definite referents ('the conductor' when the context does or does not describe an orchestra, respectively) elicit a similar post-N400, LPC when compared to a repeated noun phrase anaphor. Burkhardt concluded that the LPC effect reflected the costs of updating a discourse representation with an additional referent (for such costs observed in behavioral studies, see, for example, Murphy, 1984; cf., Pyke, 2007). Subsequent studies found compatible results with related manipulations (Burkhardt, 2007; Schumacher and Hung, 2012). However, the nature and generalizability of this reference-related LPC effect remains to be established. One study with a similar manipulation did not report any LPC modulation (Yang et al., 2007). And while one recent study with repeated proper name anaphors also reported

<sup>1</sup>Partially matching anaphors are particularly taxing to comprehension when they are semantically more specific than the antecedent, like 'the martian' referring back to an alien, or when they are atypical of a semantic category rather than typical (e.g., Almor, 1999; Van Gompel et al., 2004).

enhanced LPC for new names (Coopmans and Nieuwland, 2019), two other studies with proper names reported a reverse LPC pattern (Van Petten et al., 1991; Swaab et al., 2004). For example, in a study on natural text comprehension, Van Petten et al. (1991) reported enhanced LPC amplitude for repeated proper names compared to novel names, and suggested that these effects reflect the retrieval of semantic information associated with known names<sup>2</sup> .

Whereas the semantic relationship between an anaphor and its context can modulate the N400 (and LPC), the referential relationship between an anaphor and its context can elicit an LPC effect or yet another ERP effect. Referentially ambiguous anaphors, like 'the alien' when two different aliens were mentioned in the context, or the pronoun 'he' without a male antecedent in the sentence, elicit a sustained, frontal negativity compared to non-ambiguous anaphors (the Nref effect; for reviews, see Van Berkum et al., 2007; Nieuwland and Van Berkum, 2008b). The Nref effect can start at about 200–300 ms after word onset (not unlike an N400 effect, at least for written language comprehension), and has been obtained with noun phrases (e.g., Van Berkum et al., 1999a, 2003; Nieuwland et al., 2007; Nieuwland and Van Berkum, 2008a), pronouns (e.g., Nieuwland and Van Berkum, 2006; Nieuwland, 2014; Karimi et al., 2018), noun phrase ellipsis (e.g., Martin et al., 2012), and proper names (e.g., Coopmans and Nieuwland, 2019). While the onset latency of the Nref suggests that it indexes processes that rapidly link expressions to potential referents, the sustained nature of this effect suggests that inability to resolve reference may have a prolonged impact on comprehension (see Nieuwland et al., 2007; Nieuwland and Martin, 2017).

#### Anaphora and Neural Oscillations

ERPs are the most common dependent measure in electrophysiological research on language comprehension, but some studies have instead or additionally examined neural oscillatory responses, measured with time-frequency analysis. Oscillatory activity reflects the synchronization and desynchronization of neural populations, i.e., the transient coupling or uncoupling of functional cell assemblies (e.g., Engel et al., 2001; Buzsáki and Draguhn, 2004). ERPs and oscillatory responses are complementary electrophysiological measures, because whereas ERP analysis can only detect activity that is both time- and phase-locked to stimulus onset, time-frequency analysis can detect activity that is time-locked only<sup>3</sup> . To date, only a handful of studies have applied time-frequency analysis to examine reference processing (Van Berkum et al., 2004; Heine et al., 2006; Boudewyn et al., 2015<sup>4</sup> ; Meyer et al., 2015; Nieuwland and Martin, 2017; Coopmans and Nieuwland, 2019).

Heine et al. (2006) reported that pronouns with low-frequency antecedent nouns elicit reduced power in the theta (4–7 Hz) range compared to pronouns with high-frequency antecedents. They argued that pronoun resolution is relatively easy for low-frequency words because they capture elevated attention. Consistent with a role for memory processes in pronoun resolution, source analyses (albeit based on low resolution, 27-channel EEG data) suggested a contribution from the parahippocampal gyrus to the observed theta effect.

Meyer et al. (2015) reported that pronouns with antecedents that were embedded in a subordinate clause elicit enhanced theta power compared to pronouns referring to non-embedded antecedents, and source analysis suggested contributions from left-frontal, left-parietal, and bilateral-inferior-temporal cortices (based on 64-channel data). Meyer and colleagues argued that embedded antecedents were harder to retrieve from verbal working memory compared to non-embedded antecedents.

In other words, both Heine et al. (2006) and Meyer et al. (2015) took enhanced theta power to index difficulty with reactivating or retrieving an antecedent from memory, in line with the literature on theta effects and verbal and non-verbal working memory retrieval (e.g., Bastiaansen and Hagoort, 2003; Jacobs et al., 2006). However, it is unclear whether the reported theta effects were truly oscillatory in nature and distinct from phase-locked activity that also yields an associated ERP effect.

Two other studies report effects of reference processing in the gamma (>30 Hz) frequency range but not in the theta range. An unpublished study by Van Berkum et al. (2004) reported increased gamma power (40–55 Hz) range for pronouns with a single matching antecedent (e.g., 'she' in a sentence with one male and one female antecedent) compared to pronouns with two or zero matching antecedents ('she' in a sentence with either two female or two male antecedents, respectively). A study by Nieuwland and Martin (2017) re-analyzed four EEG datasets that had initially been collected for ERP analysis (Nieuwland and Van Berkum, 2006; Nieuwland et al., 2007; Martin et al., 2012; Nieuwland, 2014). In each dataset they observed increased gamma power for referentially successful expressions (pronouns, noun phrases, ellipsis that matched a single antecedent) compared to referentially problematic expressions (with either two matching antecedents or no matching antecedent). In one of those four studies, they compared the oscillatory response to a matching pronoun with that to a mismatching, ambiguous pronoun (e.g., "The boy said that he/she would win the race"). They found a brief gamma power increase in the 35–45 Hz range between 400 and 600 ms after pronoun onset. Beamformer source analysis (64-channel data) suggest contributions from left posterior parietal cortex, a brain region that is thought to be involved in recognition memory (Cabeza et al., 2008). They also observed a more extended gamma power increase in

<sup>2</sup> In studies on recognition memory, correctly recognized items are associated with enhanced parietal LPC responses compared to correctly rejected items, which is referred to as the parietal old/new LPC effect (e.g., Van Petten and Senkfor, 1996; Rugg and Curran, 2007; Voss and Paller, 2009). It is unknown whether such LPC effects are related to LPC effects associated with anaphoric processing.

<sup>3</sup>The brain continuously generates neural oscillations at a wide range of frequencies and the phase of these frequencies may differ at stimulus onset. By averaging over trials, ERP analysis cancels out activity that differs in phase over trials. However, a stimulus may impact the activity in a specific frequency band without changing its phase (e.g., Bastiaansen et al., 2013; Lewis et al., 2015). This impact cannot be detected in an ERP analysis, but can be detected in time-frequency analysis of spectral power.

<sup>4</sup>Boudewyn et al. (2015) investigated correlations between antecedent-elicited spectral power and ERP activity associated with noun phrase anaphora, but did not investigate spectral power changes associated with anaphors themselves and is therefore not discussed in this section.

the 60–80 Hz range between 500 and 1000 ms after pronoun onset, with source analysis suggesting a contribution from left inferior frontal gyrus, and brain region that is thought to be involved in sentence-level unification/integration processes (e.g., Hagoort, 2005; Hagoort and Indefrey, 2014). Based on these findings, Nieuwland and Martin (2017) argued that the observed gamma-band power increases reflect successful referential binding and resolution, which links incoming information to antecedents through an interaction between the brain's recognition memory networks and fronto-temporal language network.

In a recent study on comprehension of proper name anaphors, Coopmans and Nieuwland (2019) observed effects in both the theta and gamma frequency range. Their participants read story contexts that described characteristics of two people (e.g., "John and Peter are the best players in the football team"), followed by a target sentence containing a repeated or novel proper name that was either congruent or incongruent with the discourse context (e.g., "The top scorer of the team was John with thirty goals in total"). Repeated names elicited increased theta power compared to new names, which may have originated from anterior temporal regions (based on beamformer source analysis of 64-channel data), and a weak effect in the 40–55 Hz gamma range (see also Van Berkum et al., 2004). Discourse-congruent names elicited increased gamma power (60–80 Hz) compared to incongruent names in the 500–1000 ms time window, with source analysis suggesting a contribution from left frontal cortex.

In sum, reference processing thus far has been associated with modulations of theta and gamma activity. However, the available studies report mixed results, which may have to do with differences in type of linguistic expression (pronoun, noun phrase, proper name) and experimental manipulation (difficulty with retrieving an antecedent, referential ambiguity, comparing old, anaphoric names with new names). Heine et al. (2006) and Meyer et al. (2015) investigated pronouns that had uniquely identifiable antecedents but differed in the extent to which the antecedent was easily retrieved from memory, whereas Nieuwland and Martin (2017) compared ambiguous to unambiguous anaphors, and Coopmans and Nieuwland (2019) compared anaphoric to non-anaphoric proper names that were coherent or incoherent with the preceding discourse. The type of linguistic expression may matter in particular for modulations of theta activity, because theta activity can be modulated by a word's semantic meaning (e.g., Bastiaansen et al., 2005, 2008).

### The Present Study

The present EEG study investigated how people establish anaphoric meaning for noun phrases, which contain more semantic content than pronouns and proper names and therefore allow an investigation of how people can use semantic memory representations (i.e., word meaning) to resolve anaphoric reference (e.g., Garrod and Sanford, 1977; Garnham, 1989). This semantic richness raises the question of whether or to what extent anaphoric noun phrases are resolved through similar processes as other types of anaphors. Our participants listened to two-sentence story contexts followed by a written sentence that contained a target noun. These stories appeared in one of four conditions that only differed in the two antecedents described in the first sentence (see **Table 1**). Due to these differences, the target noun was either a given or 'old' anaphor (lexically identical to one of the two antecedents), an 'ambiguous' anaphor (lexically identical to both antecedents), a 'partial-match' anaphor (lexically different from both antecedents but close enough in meaning to one of the antecedents to allow an anaphoric interpretation, as indicated in a norming pre-test), or a 'new' noun (lexically and semantically different enough from both antecedents such that a novel referent must be introduced). After each story, the participants used a button press to indicate whether the target sentence contained an anaphoric noun phrase or not (old/new judgment). While this task requires meta-linguistic judgments and is therefore not representative for naturalistic comprehension, we included it in order to separate trials in which participants arrived at the intended interpretation from trials where they did not (as is also done in studies on recognition memory).

For this experimental design, we derived hypotheses from memory-based theories of anaphor resolution (e.g., Myers and O'Brien, 1998), which distinguish an early phase of memory

TABLE 1 | Example stimulus item in Dutch, containing all four conditions.

Approximate English translation is provided below each sentence. The critical word is printed in bold for presentation purposes only. All stimuli available via our OSF page https://osf.io/uak8g.

activation from subsequent discourse updating and integration. We hypothesized that activity in the early phase primarily depends on the ease with which word meaning can be activated, which is easiest for repeated nouns. For the ERP analysis, we expected to observe this phase in N400 activity (e.g., Kutas and Federmeier, 2011), with smaller (less negative) N400 ERPs for old and ambiguous anaphors compared to new nouns and partial-match anaphors (i.e., a lexical repetition effect on the N400, e.g., Van Petten et al., 1991; Besson et al., 1992; Swaab et al., 2004). We also expected smaller N400s for partial-match anaphors compared to novel nouns, because the semantic meaning of partial-match anaphors is more strongly related to the context and therefore more easily activated than that of novel nouns (Kutas and Federmeier, 2000). In our time-frequency analysis, we tested for complementary effects in the theta- and gamma-band, which are strongly associated with memory processes. We expected to observe enhanced theta (and low gamma) power for anaphoric nouns compared to new nouns (see Nieuwland and Martin, 2017, for discussion). Such a pattern would be compatible with the proper name effects recently observed by Coopmans and Nieuwland (2019), and consistent with theta and gamma band effects associated with successful recognition in memory research. However, this hypothesis disregards the association between theta activity and activation of semantic representations (e.g., Bastiaansen et al., 2005, 2008; Piai et al., 2016), which is why we also considered an alternative possibility: if theta power tracks the amount of semantic activation (e.g., Bastiaansen et al., 2005), new nouns could elicit enhanced theta power compared to old nouns.

Activity in the later, post-N400 time-window may be associated with either repetition or with discourse-level processes<sup>5</sup> . For example, we considered the possibility that anaphoric nouns would elicit larger LPCs than novel nouns (Van Petten et al., 1991; Swaab et al., 2004), although such a pattern for repeated referents has not yet been found for noun phrases. We also considered an alternative possibility, namely that new nouns would elicit larger LPCs than anaphors (which would suggest that this component indexes updating of the discourse representation to include a new referent; Burkhardt, 2006; Coopmans and Nieuwland, 2019). Furthermore, we expected ambiguous anaphors to elicit an Nref effect compared to non-ambiguous anaphors (Van Berkum et al., 1999a; Nieuwland et al., 2007; Nieuwland and Van Berkum, 2008a,b). For the time-frequency analysis, we expected enhanced high gamma (60–80 Hz) activity for anaphors compared to new nouns, possibly related to updating or integration processes (e.g., Nieuwland and Martin, 2017).

Of specific interest were the processes involved in resolving partially matching anaphors, which differ in form and meaning from the antecedent (e.g., baliemedewerker-receptioniste, desk clerk-receptionist, in **Table 1**). Previous literature suggests that such anaphors may be relatively difficult to resolve because they unexpectedly introduce new information (Garrod and Sanford, 1977; Garnham et al., 1997), which is atypical for anaphors. This violation of pragmatic principles may cause people to consider the possibility that a new referent is being introduced, and the resulting situation can only be resolved through an elaborative, anaphoric inference based on the semantic similarity of anaphor and antecedent. In such an account, old, new, and partially matching anaphors may elicit a difference in measures that index semantic activation (N400, possibly theta), but later measures could indicate whether the partially matching noun is temporarily processed as a new noun, by comparing the associated neural responses to responses elicited by new or old nouns, respectively. Alternatively, ambiguity regarding the anaphoric nature of partially matching nouns could lead to the type of Nref effect we expected for ambiguous nouns (Nieuwland, 2014).

#### MATERIALS AND METHODS

We pre-registered the number of participants and crucial elements of data processing and analysis on AsPredicted.org, available through the OSF pre-registration portal<sup>6</sup> . Procedures and analyses that were not pre-registered are designated as exploratory.

### Participants

We invited 41 participants (right-handed native-Dutch speakers who were free from known learning or language disorders) from the MPI participant pool (34 females, average age = 23.3 years, range = 19–32 years). All participants gave informed written consent to take part in the experiment, which was approved by the Ethics Committee for Behavioural Research of the Social Sciences Faculty at Radboud University Nijmegen in compliance with the Declaration of Helsinki. They received 18 euros for their participation. One participant did not finish the experiment and was replaced. For the ERP analysis, we excluded three participants due to low trial numbers (on average across conditions < 35 artifact-free trials with correct responses). For the time-frequency analysis, we excluded five participants due to low trial numbers.

#### Stimuli

The entire set of stimuli consisted of 200 experimental and 50 filler mini stories in Dutch. Each mini story consisted of three sentences, of which the first sentence introduced two antecedents (persons or objects), and the third sentence contained a critical noun phrase that also denoted a person or object (see **Table 1**). The antecedents appeared in an indefinite conjoined noun phrase that included two prenominal adjectives and that either repeated the same noun (ambiguous and new condition) or contained different nouns (old and partial-match condition). The critical word (CW) in the third sentence was always a definite noun phrase without a prenominal adjective, was never the first or second word of the sentence, and was followed by exactly four additional words in the sentence.

<sup>5</sup>Because we did not manipulate the ease with which old or new referents could be integrated (i.e., whether they were semantically coherent with the preceding discourse), our hypotheses primarily focused on the discourse updating processes associated with a new referent.

<sup>6</sup>https://osf.io/7pkc5

Both the second context sentence and the target sentence were identical across conditions. The four conditions differed only in the two antecedents described in the first sentence, which determined the available co-referential relationships between the critical word and the antecedents. The critical word in the old condition was a repeated name anaphor, which was identical to and co-referential with one antecedent (receptionist-receptionist). The ambiguous anaphor was identical to both antecedents. The partially matching anaphor was semantically overlapping or synonymous with only one of the antecedents (desk clerk-receptionist, we report semantic similarity values below), which were chosen such that the critical word would be a reasonably plausible anaphor for one antecedent. In the new condition, the critical word did not appear elsewhere in the context, and it had little semantic overlap with either antecedent to the extent that it would not be a plausible anaphor. We tried to write stories wherein the partially matching anaphor was related in meaning to the story context and to the antecedent and plausibly co-referential with the first antecedent, and wherein the novel noun was at least somewhat related in meaning to the story context but not plausibly co-referential and would therefore be interpreted as introducing a new referent. In both the given and the partial-match condition, the anaphor always referred to the first antecedent in the context sentence.

In an effort to optimize our stimulus set for these constraints, we performed a behavioral norming study on an initial set of 240 items. Twenty-four participants, who did not take part in the EEG experiment, each read 240 stories in the New, Old or Partial-Match condition, with conditions counterbalanced over three stimulus lists such that each participant saw the same number of items per condition and each item was seen in each condition equally often across participants. The participants read each story presented as a whole on the screen with the target word in boldface, and judged whether each target word referred back to someone or something in the story ('old') or whether it referred to someone or something new ('new'). Based on the results, we selected the best 200 items, that is, items receiving responses most in line with our design (partial-matching and old anaphors considered 'old' and novel nouns considered 'new'). Because we made further changes to the selected materials after the norming study, and because we also collected old/new judgments during the main EEG experiment (which are the most relevant behavioral data), the results of the stimulus norming test are not discussed here, but they can be found on our OSF page<sup>7</sup> .

For the final set of items, we confirmed that partially matching nouns were more semantically similar to the corresponding first antecedent than new nouns. We used semantic similarity scores obtained from 'snaut' (Mandera et al., 2017) 8 , using a word2vec-compatible 'continuous bag of words' (CBOW) model for Dutch lemmas, trained on the SONAR-500 corpus and an additional subtitle corpus. With the caveat that not all our words found a match in the corpus (155 partially matching nouns and 149 new nouns), partially matching nouns and their antecedents had a smaller semantic distance (i.e., were more semantically similar) than new nouns and their antecedents (0.57 versus 0.70, two-sample t-test t = 8.47, p < 0.001).

For the EEG experiment, we added 50 filler items to the final set of 200 experimental items. Three fillers served as practice items (one item corresponding to the New, Old and Partial-Match condition each). The other 47 fillers had the same format as the New condition, which was done to increase the percentage of stories without an anaphor. Roughly 60% of the items in each stimulus list contained an anaphor, while 40% of all items contained a new noun.

We followed previous studies on discourse comprehension (Van Berkum et al., 1999a,b; Nieuwland and Van Berkum, 2006, 2008a) by using a mixed-modality design where the context sentences were spoken and the target sentence was written. We created audio-recordings (44.1 kHz sampling) for the four different story contexts. All recordings were performed by the same native-Dutch, female speaker in a sound-shielded booth. This speaker recorded both context sentences for the old condition. For the other three conditions, only the first context sentence was recorded, which was then paired with the second sentence recorded for the Old condition. Because the speaking rate for the recordings was considered slightly too fast for the experiment, the recordings were lengthened by 15% using the Praat software (Boersma and Weenink, 2013). This yielded a speaker rate that was comfortable for listening without being unnaturally slow (as evaluated by two native speakers of Dutch) and without compromising sound quality.

As there were four conditions, we created four stimulus lists. Each list contained 50 items of each condition and 50 filler items. The lists were created such that they never contained multiple conditions of the same item. Next, the four lists were distributed equally among the participants. For each participant, the items in the list were pseudorandomized, such that there were no consecutive trials of the same condition.

#### Procedure

After participants had given written informed consent, they were tested in a sound-shielded booth. They were told that the experiment was about understanding mini stories. They were also told that the last sentence of each mini story was about a specific person or object, and that they had to indicate after each trial whether this person or object had been referred to before ('old') or not ('new'). To discourage participants from using a strategy based on noun repetition alone, and to encourage them to establish co-referential relationships between anaphor and antecedent whenever plausible, we told them that anaphors did not have to be exactly the same as antecedent and could be a different word.

Each trial started with a fixation cross. When participants pressed a button, the two spoken context sentences were presented over loudspeakers located on the desk in front of the participant. Then, 700 ms after the end of the audio recording, the third sentence was presented visually, one word at a time, in black letters (font Lucidia Console, size 20) on the center of a computer screen, which had a light gray background. Each word was presented for 300 ms, with an inter-stimulus-interval of 300 ms. Sentence-final words were presented for 550 ms and

<sup>7</sup>https://osf.io/uak8g/

<sup>8</sup>http://meshugga.ugent.be/snaut

followed by a blank screen for 300 ms. Subsequently, the old-new question was presented, which could be answered by a button press (left button for "new," right button for "old"). Participants were asked to minimize eye blinks and body movements during the word-by-word presentation of the third sentence.

The experiment started with three practice trials, after which the experimental trials would be presented. These were presented in five blocks of 50 items. Participants were allowed to take short breaks between blocks. In total, the experiment lasted approximately 80 min.

#### EEG Recording

The electroencephalogram (EEG) was recorded using an MPI custom actiCAP 64-electrode montage (Brain Products, Munich, Germany), of which 58 electrodes were mounted in the electrode cap (see **Figure 1**). We recorded horizontal EOG with one electrode placed on the outer canthus of the right eye, and vertical EOG with two electrodes placed below both eyes. One electrode was placed on the right mastoid, the reference electrode was placed on the left mastoid, and the ground was placed on the forehead. The EEG signal was amplified through BrainAmp DC amplifiers, referenced online to the left mastoid, sampled at 500 Hz and filtered with a passband of 0.016-249 Hz. Pre-processing was performed in BrainVision Analyzer 2.1 (Brain Products, Munich, Germany).

#### ERP Pre-processing and Analysis

We first visually inspected the raw data and interpolated bad channels if they contained strong 50 Hz line noise or indicated broken electrodes. The data was then band-pass filtered at 0.03– 40 Hz (24 db/oct) and re-referenced to the average of the left and right mastoid. Segments were extracted ranging from −500 to 1500 ms relative to CW onset, and segments in which an incorrect response had been given ('new' response to old, partial-match or ambiguous; 'old' response to new) were rejected. Based on visual inspection, we then removed bad segments containing large eye movements, muscle activity, or amplifier blocking. Subsequently, we removed blinks, eye-movements and steady muscle activity using Independent Component Analysis (ICA; Jung et al., 2000), using ICA weights from a 1 Hz high-pass filtered version

of the data. We then performed baseline correction using a 250 ms pre-CW baseline interval, and then automatically rejected segments that contained voltage values exceeding ±90 µV. We excluded three participants who retained fewer than 140 trials in total (35 per condition, on average). In the final set of trials for the ERP analysis, participants had on average 45.3 trials for ambiguous nouns, 42.8 for old nouns, 43.7 for new nouns, and 35.4 for partially matching nouns.

For analysis of the behavioral responses, we performed mixed effects logistic regression (Baayen et al., 2008) in the R software (R Core Team, 2018) 9 , with correction for multiple comparisons using the Holm method (Holm, 1979, implemented in the p.adjust function). For the ERP analysis, we performed a linear mixed-effects analysis (Baayen et al., 2008). The ERP analyses were done separately for three dependent variables corresponding to a specific region of interest (ROI): N400, LPC and Nref.

For the N400, we calculated the average voltage across the centroparietal electrodes 35, 28, 3, 41, 40, 8, 9, 47, 27, 15 in a 300–500 ms window after CW onset, for each trial and each participant (see **Figure 1**). For the LPC, we calculated the average voltage across these same centroparietal electrodes but in a 500–1000 ms window after CW onset. For the Nref, we calculated the average voltage across the frontal electrodes 53, 60, 21, 46, 59, 14, 39, 58, 7 in a 300–1500 ms window after CW onset.

The variable 'condition' had four levels: old, ambiguous, new, and partial, which were deviation coded. The models had subject and item as random effects, and initially included a by-subject and by-item random slope for 'condition' (Barr et al., 2013) but these slopes were removed due to convergence issues. We compared models with a chi-square test using R's anova() function, and treated p-values below α = 0.05 as statistically significant. For the N400 and LPC, we performed all (Holm-corrected<sup>10</sup>) pairwise comparisons between given anaphors, partially matching anaphor and novel nouns, but not ambiguous anaphors. For the Nref, we specifically tested whether ERPs elicited by ambiguous anaphors were more negative than the mean ERP values across the other three conditions.

#### Oscillatory Pre-processing and Analysis

After interpolation of bad channels, we band-pass filtered the data at 0.1–100 Hz (24 db/oct), re-referenced the data to the average of the left and right mastoid, and segmented the data into epochs ranging from −1000 to 2500 ms relative to CW onset. After this, we used the same procedure as for the ERP analysis to reject trials with incorrect responses or artifacts and to perform ICA-based correction for blinks, eye movements and steady muscle activity. The resulting dataset for each participant contained many artifact-free trials with voltage values exceeding ±100 µV. We therefore considered the preregistered ±100 µV amplitude criterion to be too conservative, excluding on average 50.9 trials per participant (SD = 38.6). We chose to use a more liberal difference criterion, which excluded segments for which the difference between the maximum and minimum voltage exceeded 200 µV (see Coopmans and Nieuwland, 2019). We excluded four participants who retained fewer than 140 trials in total. In the final set of trials for the time-frequency analysis, participants had on average 46.5 trials for ambiguous nouns, 45.2 for old nouns, 43.2 for new nouns, and 37 for partially matching nouns.

Time-frequency analysis was performed using the Fieldtrip toolbox (Oostenveld et al., 2011). We performed time-frequency analysis in two different, but partially overlapping frequency ranges. For the low (2–30 Hz) range, we used a 400-ms Hanning window to compute power changes in frequency steps of 1 Hz and time steps of 10 ms. For the high (25–90 Hz) frequency range, we computed power changes with a multitaper approach (Mitra and Pesaran, 1999) based on Slepian sequences as tapers, with a 400-ms time-smoothing and a ±5 Hz spectral-smoothing window, in frequency steps of 2.5 Hz and time steps of 10 ms. Then, for each trial, we computed power in the post-stimulus interval as a relative change from a baseline interval spanning from −500 to −250 ms relative to CW onset. Average power changes per subject were computed for each condition separately.

For the statistical analysis, we pre-registered three ROIs: theta (4–7 Hz) activity in the 0–1000 ms interval after critical word onset, averaged over frequency but not over time; low gamma (35–45 Hz) in the 400–600 ms interval, average over both frequency and time; high gamma (60–80 Hz) in the 500-1000 ms interval, average over both frequency and time. In addition to these ROIs, we also pre-registered an analysis of the 200–1500 ms time window that did not average activity over time or frequency.

We used cluster-based random permutation tests (Maris and Oostenveld, 2007) to compare differences in oscillatory power across conditions. In brief, this statistical test works as follows: first, by means of a two-sided dependent samples t-test we performed all pairwise comparisons between the four conditions on the three dependent variables described above, which yielded uncorrected p-values. Neighboring data triplets of electrode, time and frequency-band that exceeded a critical α-level of 0.05 were clustered. Clusters of activity were evaluated by comparing their cluster-level test statistic (sum of individual t-values) to a permutation distribution that was created by computing the largest cluster-level t-value on 1000 permutations of the same dataset. Clusters falling in the highest or lowest 2.5th percentile were considered statistically significant. We used the correct-tail option that corrects p-values for doing a two-sided test, which allowed us to evaluate p-values at α = 0.05.

#### RESULTS

#### Old/New Judgments

Participants responded most accurately to ambiguous nouns, then to old nouns, new nouns and partially matching nouns (**Figure 2**; this figure and the analysis only includes participants used in the ERP analysis, average number of trials per conditions is M = 48.3, 46.3, 45.4, and 37.5, respectively). Our analysis

<sup>9</sup>For data manipulation, analysis and visualization, we used the following packages: dplyr (Wickham et al., 2019), gdata (Warnes et al., 2017), tidyverse (Wickham, 2017), tidyr (Wickham and Henry, 2019), Rmisc (Hope, 2013), ggplot2 (Wickham, 2016), cowplot (Wilke, 2019), lme4 (Bates et al., 2015), lmerTest (Kuznetsova et al., 2017), emmeans (Lenth, 2019).

<sup>10</sup>This correction was not pre-registered but requested by a reviewer.

plotted as the number of correct responses using raincloud plots (Allen et al., 2019), with each point representing a single participant, including the corresponding density and box plot. The right graph shows all pairwise differences between conditions, plotted as the estimated marginal means difference with the 95% confidence level.

revealed a strong effect of condition (χ <sup>2</sup> = 517.06, p < 0.001) and differences between all pairs of conditions, with the strongest effects seen in comparison to the partially matching condition.

#### Pre-registered ERP Analyses

#### N400 (300–500 ms)

Our experimental manipulation was associated with modulations of activity in the N400 region of interest (χ <sup>2</sup> = 196.18, p < 0.001), with most negative amplitude elicited by new nouns, followed by partially matching, old and ambiguous nouns in that order (**Figure 3**; ERP waveforms at all individual channels are shown in **Supplementary Figure 1**). Pairwise follow-up tests revealed reliable differences between all conditions (**Figure 4**).

#### LPC (500–1000 ms)

Our experimental manipulation was also associated with modulations of activity in the subsequent LPC time window (χ <sup>2</sup> = 13.311, p = 0.004; **Figures 3**, **4** and **Supplementary Figure 1**). This effect mostly reflected a carry-over effect from the enhanced N400 to new nouns, as the pairwise follow-ups showed that while new nouns elicited reliably more negative voltage than the other three conditions (although for partially matching nouns, this difference was not statistically significant after multiple comparisons correction), these other conditions did not reliably differ from each other.

#### Nref (300–1500 ms)

At the frontal ROI, ambiguous nouns elicit more negative voltage compared to the other conditions (M = −0.32, S.E. = 0.28; **Figures 3**, **4** and **Supplementary Figure 1**), compatible with an Nref effect, but this contrast did not reach the conventional alpha = 0.05 criterion (χ <sup>2</sup> = 1.3, p = 0.25).

#### Exploratory ERP Analyses

Our pre-registered ERP analyses showed that EEG activity was most sensitive to whether or not the critical noun had featured in the spoken story context, but did not differentiate anaphoric nouns and new nouns. Although amplitude in the N400 ROI differentiated between all four conditions, this pattern could merely reflect the relative ease of accessing the meaning of a noun that is more strongly related to context words, in other words, it need not reflect the process of anaphor resolution. Moreover, the smallest N400 was obtained for the ambiguous condition, wherein anaphor resolution was not straightforward. Likewise, we did not obtain a clear pattern of correlation between anaphor resolution and modulation of the LPC in the preregistered ROI. We offer further discussion of these results in the Section "Discussion."

We considered the possibility that our participants used a strategy whereby they based their initial interpretation on whether the noun had been heard before (old/ambiguous versus new/partial), and subsequently changed this initial interpretation if the new noun could plausibly refer back to an antecedent (partial versus new). Such a strategy could be associated with an ERP effect of partial-matching nouns in a different ROI than the one we pre-registered. We tested for such an effect in two exploratory ERP analyses.

Our first exploratory analysis employed a mass regression approach (e.g., Groppe et al., 2011; Nieuwland et al., 2019) to test for later effects in the data segments from the pre-registered analysis. We down-sampled the data to 100 Hz and then ran a mixed-effects model analysis to test the contrast partial-match against the mean of the other three conditions at each electrode channel and at each data point between −500 ms before to 1500 ms after noun onset. This yielded an effect estimate and standard error for each timepoint and channel. The associated

p-values in the post-N400 window (from 500 to 1500 ms after noun onset) were corrected for multiple comparisons using the Benjamini and Hochberg method to control the false discovery rate (Benjamini and Hochberg, 1995). The resulting estimates are plotted as ERPs along with the corrected p-values (**Figure 5** for an ROI-based plot, and **Supplementary Figure 2** for a plot of activity at all individual channels and highlighting of statistically significant samples after multiple comparison correction), revealing that partially matching nouns elicited more positive voltage than the other three conditions, particularly at

for each ROI with 95% confidence level.

middle-frontal, right-frontal and right-central channels in the post-N400 time window. Of note, the ROIs in **Figure 5** contain different numbers of channels.

We performed similar analyses that directly compared partially matching nouns to only new or old nouns, and new nouns to old nouns (**Figure 6** and **Supplementary Figures 3–5**). These results suggest that the processing consequences of the partial match condition extended beyond the pre-registered ROI, and that partially matching nouns and new nouns both elicited a frontal positive ERP effect compared to old nouns in the post-N400 window around 500–1000 ms.