Distinguish between focus and newness: An ERP study

Journal of Neurolinguistics 31 (2014) 28e41

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Distinguish between focus and newness: An ERP study Lijing Chen a, b, Lin Wang a, Yufang Yang a, * a

Key Laboratory of Behavioral Science, Institute of Psychology, Chinese Academy of Sciences, 16 Lincui Rd., Chaoyang District, Beijing, China Department of Psychology, Fujian Normal University, Fuzhou, China

b

a r t i c l e i n f o

a b s t r a c t

Article history: Received 13 November 2013 Received in revised form 16 June 2014 Accepted 16 June 2014 Available online

The relationship between focus and newness was explored by recording brain responses to information structure in discourse reading. Focus was manipulated by whether or not placing a Chinese focus-particle “shi” in front of the critical words, while newness was manipulated by whether or not introducing the critical words in the preceding context. The focused words elicited a larger P2 as well as a larger positivity than the non-focused words, possibly reflecting attention allocation and immediate integration of focused information respectively. In contrast, the new words elicited a larger N400 and a smaller LPC than the given words, which may reflect difficult integration or memory retrieval of new information. These results suggest that the processing of focus and newness may involve different cognitive processes. Therefore, focus should be distinguished from newness from the perspective of cognitive processing. © 2014 Elsevier Ltd. All rights reserved.

Keywords: Focus Newness ‘Shi’ Information structure ERPs Discourse processing

1. Introduction In everyday communication, speakers/writers make use of information structure to ensure that the receivers pick up the most relevant information. Typically, information structure divides a sentence into two complementary parts, such as focus vs. background, new vs. given information, theme vs.

* Corresponding author. Tel.: þ86 10 64888629. E-mail addresses: [email protected], [email protected] (Y. Yang).

http://dx.doi.org/10.1016/j.jneuroling.2014.06.002 0911-6044/© 2014 Elsevier Ltd. All rights reserved.

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rheme, and so on (Chomsky, 1965; Karttunen & Peters, 1979; Paterson et al., 2007; Steedman, 1991). Among them, the dichotomy of focus vs. background and that of new vs. given information are often intertwined with each other. In the dichotomy of focus vs. background, focus is the most emphasized or prominent constituent in a sentence, whereas the other part of the sentence is background (Halliday, 1967). For example, in the sentence “It was Tom who helped her. (The focused element is in boldface)” The cleft-element “Tom” is emphasized by the cleft structure and becomes the focus of the sentence. This way of invoking information structure is equivalent to the use of Chinese focus particle ‘shi’ in the Chinese sentence “Shi Tom helped her.” In addition to syntactic markers (i.e., it-cleft structure and focus particles), other linguistic devices, such as wh-question context (“Who/What/Where…”) in question answer pairs and pitch accent in some spoken languages (e.g., Dutch and English), can also be used to mark focus. For brevity, this distinction of focus vs. background will be referred to as “focus”. On the other hand, in the dichotomy of new vs. given, new information is the previously unknown information, whereas given information is what has been known with respect to receiver's knowledge (Prince, 1992). In the discourse context, new information refers to a word/phrase that appears for the first time, whereas given information refers to a word/phrase that has appeared in the prior context (Prince, 1992). For clarification, the dichotomy of new vs. given will be referred to as “newness” in the following text. Linguistic theories often propose that focus conveys new information (e.g., Halliday, 1967). For example, “Tom” in the sentence “It was Tom who helped her.” may answer an implicit question of “who helped her?” and thus conveys previously unknown information. Since “new information” is an important part of focus, the relationship between focus and newness is intertwined and complicated. Previous linguistic studies examined this issue in two different directions. Several studies defined new information as a subtype of focus (Halliday, 1967), and thus the boundary between focus and newness was blurred. On the other hand, some recent studies proposed to treat focus and newness as two independent concepts and restrict the concept “new information” only in the category of newness to ry & Krifka, 2008; Selkirk, 2008). To support this view, they provided some acoustic avoid confusion (Fe evidence which showed that the prosodic patterns of focus and newness were different (Beaver, Clark, ry & Ishihara, 2009; Katz & Selkirk, 2011; Selkirk, 2002). Flemming, Jaeger, & Wolters, 2007; Fe However, the distinction between focus and newness has been largely unexplored until recently. As an extreme instance, focus and newness were not distinguished from each other at all. For example, Zimmer and Engelkamp (1981) examined the effect of newness on picture viewing. After defining new information as the first-mentioned word and given information as the second-mentioned word, new information was also focused by the cleft structure whereas given information was not. They found that new (focused) information was fixated on longer than given (non-focused) information. This interesting result was interpreted as the effect of new (focused) information. However, if the premise, that newness and focus are the same, is false, the results could not be easily interpreted. The similar manipulation in which focus and newness are intertwined was also adopted in some other studies, especially in spoken language studies (Breen, Fedorenko, Wagner, & Gibson, 2010). Most psycholinguistic studies on focus/newness examined only one of them, without comparing their effects or exploring their relationship. For focus, while most behavior studies (Almor, 1999; Birch & Garnsey, 1995; Foraker & McElree, 2007; Klin, Weingartner, Guzman, & Levine, 2004; Liversedge, Paterson, & Clayes, 2002; Ni, Crain, & Shankweiler, 1996; Paterson, Liversedge, & Underwood, 1999; Sanford, Price, & Sanford, 2009; Sedivy, 2002; Sturt, Sanford, Stewart, & Dawydiak, 2004) have shown the advantages of focus on language comprehension, the studies on on-line processing of focus reported inconsistent results. That is, several eye movement studies showed that focused information was processed more quickly than non-focused information, reflecting the facilitation of the processing of focus (Birch & Rayner, 2010; Morris & Folk, 1998), whereas some other eye movement studies showed that the on-line processing patterns between focused and non-focused information were not different (Ward & Sturt, 2007). For newness, on the other hand, all the self-pace reading studies and eye-movement studies have shown that new information took longer time to read than given information (Irwin, Bock, & Stanovich, 1982; Liversedge, Pickering, Clayes, & Branigan, 2003; Raney & Rayner, 1995; Rayner, 1998; Traxler, Foss, Seely, Kaup, & Morris, 2000), reflecting the processing difficulty for new information compared to given information. The processing difficulty might relate to

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increased memory retrieval effort and more careful examination of new information compared to given information. To explore the relationship between focus and newness more directly, in a previous eye movement study (Chen, Li, & Yang, 2012), we explored the effects of focus and newness during on-line discourse processing. As shown in the sample passages (see Table 1), the factors Focus (focus vs. non-focus) and Newness (new vs. given) were orthogonally manipulated on the target name (“Zhongying”). Focus was marked by a Chinese focus-particle “shi” which is equivalent to the cleft structure in English (Fang, 1995). Newness was realized by the control of preceding context in a way that the target name was introduced for the first time or for the second time. In the experiment, for each passage, the entire text was shown on the same screen. The participants read these passages at their own pace. The findings showed clearly different processing patterns between focus and newness. The focused names were processed more quickly than the non-focused names, while the new names were processed more slowly than the given names. These results may reflect that focused information was easier to process than non-focused information, whereas new information was more difficult to process than give information, and thus reveal the difference between focus and newness during discourse comprehension. Moreover, our previous eye-movement study (Chen et al., 2012) has revealed an interaction between focus and newness on the post-target regions, indicating that the newness effect on the posttarget regions only occurred in the focus condition. However, it remains unclear whether the effect is a delay effect of the target words, or it reflects the on-line integration of the post-target words. That is, first, in a natural reading situation, the participants adjust the reading pace by themselves, thus, it is possible that the target words are not processed enough and the effect is delayed to the succeeding words. And second, excluding the first case, the primary effect in the post-target region is caused by processing and integrating the post-target word into the discourse. Hence, to address this question, in the present experiment, we displayed the text in a word by word manner to separate the target word from the post-target word. A word-by-word presentation has been extensively used in numerous event-related potential (ERP) studies due to the necessity of identifying critical words as well as controlling horizontal eye movement during EEG recording (Kutas & Hillyard, 1980). In addition, we presented each word with a long display time (e.g., 700 ms, which is quite longer than the necessary time to process a word) to force the readers to process the words more carefully, which may eliminate the delayed effect of the target words. Although this way of presenting stimuli might impose different demands on working memory and co-reference establishment from natural reading, it would have similar effects across different conditions. Compared to eye-movement technique, ERP technique records the brain response to words stimuli. The measured ERPs are supposed to reflect different cognitive processes (Luck, 2005). Therefore, the use of ERP technique enables us obtain more direct evidences regarding the underlying cognitive processes involved in the focus/newness processing. Previous ERP studies rarely distinguished Table 1 An example of experimental materials. The context sentences in the new condition: 何仁正在劝说朋友们和他去郊游, 根本不管天气预报说要变天。 Heren was persuading his friends to go on an outing. (He) ignored that the weather forecast had predicted a bad weather. The context sentences in the given condition: 何仁正在劝说钟 钟莹他们去郊游, 根本不管天气预报说要变天。 Heren was persuading Zhongying and others to go on an outing. (He) ignored that the weather forecast had predicted a bad weather. The target sentence in the focus condition: 这时候 是 钟莹 理智地 反对 他。 At that time shi Zhongying reasonably opposed him. At that time it was Zhongying (who) opposed him reasonably. The target sentence in the non-focus condition: 这时候 钟莹 理智地 反对 他。 At that time Zhongying reasonably opposed him. At that time Zhongying opposed him reasonably. “Zhongying” in the target sentence is the target word; “shi” is the focus-particle. The words in bracket do not exist in the original Chinese materials.

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between focus and newness. In response to focus manipulation, different ERP effects have been reported (Bornkessel, Schlesewsky, & Friederici, 2003; Cowles, Kluender, Kutas, & Polinsky, 2007; Stolterfoht, Friederici, Alter, & Steube, 2007). Several studies indicated that focused elements elicited a larger P3b component than non-focused elements (Bornkessel et al., 2003; Cowles et al., 2007). Since the P3b component is often associated with the integration processes, these results were interpreted as an indication of more integration effort devoted to focus than to non-focus (Bornkessel et al., 2003; Cowles et al., 2007). On the other hand, some other studies reported that focused words elicited a smaller N400 than non-focused words (Wang, Hagoort, & Yang, 2009). Because there is a link between the N400 component and processing difficulty (Kutas & Hillyard, 1980), these results were interpreted as the processing facilitation of focus (Wang et al., 2009). As to newness, however, previous studies generally showed a larger N400 for new information compared to given information (Anderson & Holcomb, 2005; Camblin, Ledoux, Boudewyn, Gordon, & Swaab, 2007; van Petten, Kutas, Kluender, Mitchiner, & McIsaac, 1991), which may reflect the processing difficulties of new information. In addition, in word list recall, a larger LPC (starting at about 500 ms post-onset) for given words compared to new words was also reported, which may reflect the memory retrieval process of the given words. Interestingly, in discourse context, this effect showed opposite patterns for common nouns vs. proper names. For common nouns, given words elicited a smaller LPC than new words, reflecting lighter mnemonic demands to given nouns than new nouns; whereas for proper names, given words elicited a larger LPC than new words as long as the discourse was congruent, reflecting the memory retrieval process of the given names (van Petten et al., 1991; Swaab, Camblin, & Gordon, 2004). Recently, several ERP studies investigated the interaction between focus and newness by marking focus using pitch accent during spoken language comprehension (Hruska & Alter, 2004; Li, Hagoort, & Yang, 2008; Wang, Bastiaansen, Yang, & Hagoort, 2011). They found that when new information was not marked to be focus by pitch accent, an N400 effect was found. On the other hand, when given information was marked to be focus by pitch accent, a larger positivity was elicited. Therefore, there seems to be an interaction between focus (which is marked by pitch accent) and newness. In addition, although the interaction between focus and newness is unclear in text comprehension, related work has provided some insight into this question. In Ledoux, Gordon, Camblin, and Swaab (2007), a repeated name referred to the singular character in the context which can be taken as a focused antecedent (e.g., “Daniel moved the cabinet because Daniel needed room for the desk.”), or referred to one of the two characters in the context which can be taken as non-focused antecedents (e.g., “Daniel and Amanda moved the cabinet because Daniel needed room for the desk.”). They found that when referring to the non-focused antecedent, the repeated name elicited a smaller N400 than the new name, whereas this difference was eliminated when the repeated name referred to the focused antecedent, suggesting an interaction between focus and newness. Thus, in order to further explore the relationship between focus and newness, we conducted an ERP experiment using similar experimental materials as those in Chen et al. (2012), which marked focus using Chinese particle “shi”. The primary hypothesis in the present study is that focus and newness would elicit different ERP effects. Although previous studies that tested the focused/non-focused words have proposed different interpretations of the effects of focus, all the findings seemed to reveal a larger positivity for the focused words than for the non-focused words. Thus, we expected to see such a positive effect for focus. Based on previous studies, we expected to see an N400 effect and an LPC effect for newness. However, it remains an open question whether focus and newness interact with each other. If the cognitive processes involved in them are different and independent, there should be no interaction; however, if they share similar cognitive processes with each other (as shown previously between pitch accent and newness), an interaction between these two factors should be observed. 2. Material and methods 2.1. Participants Twenty undergraduate or graduate students (mean age: 22.1 years, age range: 20e24 years; 10 males) were paid to participate in the experiment. All were native speakers of Mandarin Chinese, right-

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handed and had normal or corrected-to-normal vision. Informed written consent was obtained from each participant. 2.2. Materials We constructed 160 sets of passages. Each passage consisted of three sentences (See Table 1). The initial sentence introduced either two protagonists of different genders (in the given information condition, one of them was defined as a critical word) or only one protagonist (in the new information condition, the not introduced protagonist was defined as a critical word). The continuation sentence referred to the first given (and therefore not the critical word) protagonist and developed the story. In the third sentence, the critical word was focused by placing the focus-particle shi in front of it (in the focus condition) or was not focused at all (in the non-focus condition). Thus, each passage had four versions which resulted from the manipulations of the initial sentence and the third sentence. The critical words were two-character person names and were the same in all the four versions. We also constructed 80 filler passages in order to obscure the purpose of the experiment. All were three-sentence passages, with the location of the focus-particle (20 in the first sentence, 20 in the second sentence and the remainder with no focus-particle) as well as the number of the protagonists varied (1, 2, 3 or more). Four counterbalanced lists were created according to a Latin square procedure. Only one version of each passage was presented in each list. Each list contained 250 passages, including 160 experimental passages (40 passages per condition), 80 filler passages, and 10 practice passages. 2.3. Procedures Participants were seated in a comfortable armchair located in a sound-attenuating room. The passages were presented visually on a monitor located approximately 80 cm in front of participants. The stimuli were presented in white Chinese Songti font on a black background, with a font size of 18. Each trial started with a “þ” appearing in the center of the screen for 1000 ms. Then after a 300 ms blank screen interval, the text was presented word by word in the center of the screen. Each word was presented for 400 ms and was followed by a 300 ms blank screen interval. The comma/period appeared together with the last word of each sentence. Participants were instructed not to move during the presentation of the texts. Participants were instructed to read the passages for comprehension. To make sure that they actually comprehended the passages, a comprehension question was presented after the presentation of the passage for 1/3 of the trials. The question required a YESeNO response, with half YES (pressing the “F” key) and half NO (pressing the “J” key). The whole question appeared on the screen for 5000 ms and the participants had to give a response before it disappeared. Once the participants gave a response, the question disappeared, and the next trial began after a 300 ms blank screen interval. For the other trials that were not followed by a question, a 5000 ms blank screen was presented. The participants could choose to go to the next trial by pressing the SPACE key. The passages were presented in 10 blocks of 24 trials each. The trials were presented in different pseudorandom orders to eliminate order effects. Each block took approximately 6 min. Between the starting of blocks, participants were given short breaks. Before the experimental session, participants completed 10 practice trials to familiarize with the experimental procedure. The whole experiment lasted approximately 2.5 h, including participant preparation, practice and the formal experiment. 2.4. EEG recording and preprocessing The EEG was recorded from 64 Ag/AgCl electrodes embedded in an electrode cap (Neuroscan, Inc.). The electrodes were placed according to the extended 10-20 system (for the electrodes configuration see http://www.easycap.de/easycap/e/electrodes/09_M11.htm). Electrodes were referenced online to the right mastoid. The vertical eye movements and blinks were monitored bipolar via electrodes placed above and below the left eye. Horizontal eye movements were monitored bipolar with electrodes at the

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outer canthus of each eye. Impedances were kept below 5 KU for all electrodes. The EEG signal was amplified by SYNAMPS (Neuroscan, Inc.) amplifier with a band pass of 0.05e100 Hz and was continuously recorded at a sampling frequency of 500 Hz. Offline, the data of one participant (female) were discarded because of technical problem. For the remaining 19 participants, the eye blinks were corrected automatically by Neuroscan module “Ocular artifact reduction”. It corrected eye blinks using the method developed by Semlitsch, Anderer, Schuster, and Presslich (1986). The data were filtered with a 40 Hz low-pass filter and segmented into epochs spanning from 200 ms to 800 ms relative to the onset of the critical word, with a 200 ms pre-stimulus baseline. The trials with voltage exceeding ±75 mV were rejected. One participant (male) was excluded from further analysis because the rejection rate of his data exceeded 40%. For the remaining 18 participants, 4.6% of the trials were rejected. The data were re-referenced to the algebraic average of both mastoids in the end.

2.5. Data analysis On the basis of both visual inspection of the grand averages (see Fig. 1) and previous studies (Cowles et al., 2007; van Petten et al., 1991; Swaab et al., 2004; Wang et al., 2009), three time windows of interest were selected: (a) 150e250 ms (b) 250e500 ms (c) 500e700 ms. For each time windows, separate repeated-measure ANOVAs were conducted for mean amplitude values on the midline electrodes and lateral electrodes. The midline electrodes were grouped and averaged in three regions: anterior (FPZ, FZ), central (FCZ, CZ, CPZ), and posterior (PZ, POZ, OZ). The lateral electrodes were grouped and averaged in six regions which were symmetrical between the two hemispheres (left vs. right): left anterior (FP1, AF3, AF7, F3, F5, F7), left central (FC3, FC5, C3, C5, CP3, CP5), left posterior (P3, P5, P7, PO3, PO7, O1), right anterior (FP2, AF4, AF8, F4, F6, F8), right central (FC4, FC6, C4, C6, CP4, CP6), and right posterior (P4, P6, P8, PO4, PO6, O2). Thus for the midline electrodes, a three-way ANOVA with the factors Anteriority (anterior, central, posterior), Newness (new, given), and Focus (focus, non-focus) were calculated. While for the lateral electrodes, a four-way ANOVA with the factors Hemisphere (left, right), Anteriority (anterior, central, posterior), Newness (new, given), and Focus (focus, non-focus) were calculated. The significant level was set at alpha ¼ 0.05. The Greenhouse and Geisser (1959)

F3

FZ

F4

C3

CZ

C4

P3

PZ

P4

——

focus/new

------

focus/given

——

non-focus/new

------

non-focus/given

uV

ms

Fig. 1. Grand average ERPs for the four conditions at F3, FZ, F4, C3, CZ, C4, P3, Pz, P4 electrodes.

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correction was applied to the critical values when the degree of freedom was larger than 1 and the sphericity test was significant. 3. Results 3.1. Behavioral results The average accuracy of the comprehension questions was 96.2%, suggesting that the participants actively read and comprehended the passages. There was no significant difference among the four conditions (Fs < 1.7).

3.2. ERP results Fig. 1 shows the grand average ERPs elicited by the critical words in the four conditions (2 Focus * 2 Newness) at selected electrode sites. Compared with the non-focused words, the focused words elicited an enhanced P2 (150e250 ms), a reduced N400 (250e500 ms) and an enhanced LPC (500e700 ms) component, whereas the new words elicited an enhanced N400 (250e500 ms) and a reduced LPC (500e700 ms) component relative to the given words. 3.2.1. 150e250 ms (P2) The analysis of the lateral electrodes revealed a significant main effect of Focus (F(1, 17) ¼ 39.30, p < .001), indicating that the focused words elicited a larger positivity than the non-focused words (Fig. 1). There was a three-way interaction among Focus, Anteriority and Hemisphere (F(2, 34) ¼ 4.24, p < .05). Further analysis revealed a significant interaction between Focus and Anteriority in the left hemisphere (F(2, 34) ¼ 5.59, p < .05), showing that the effect of Focus was more robust over the leftcentral region (left-anterior region: F(1, 17) ¼ 22.94, p < .001; left-central region: F(1, 17) ¼ 31.98, p < .001; left-posterior region: F(1, 17) ¼ 24.26, p < .001). For the right hemisphere, there was no significant interaction between Focus and Anteriority (F(2, 34) < 2.2); however, there was a significant main effect of Focus (F(1, 17) ¼ 36.69, p < .001), indicating that the focus effect was shown over the whole right hemisphere (Fig. 2). For the midline electrodes, a significant main effect of Focus (F(1, 17) ¼ 29.33, p < .001) was found, indicating that the focused words elicited a larger positivity than the non-focused words. There was no significant main effect of Newness or interaction between Focus and Newness (Fs < 1). 3.2.2. 250e500 ms (N400) The analysis of the lateral electrodes revealed a significant main effect of Focus (F(1, 17) ¼ 69.27, p < .001) (Fig. 1) and an interaction between Focus and Anteriority (F(2, 34) ¼ 5.65, p < .05). Further analysis showed that the focused words elicited a smaller negativity than the non-focused words for all the three regions and the effect was more robust for the central region (anterior region: F(1, 17) ¼ 22.10, p < .001; central region: F(1, 17) ¼ 66.79, p < .001; posterior region: F(1, 17) ¼ 54.19, p < .001) (Fig. 2). For Newness, on the other hand, the analysis also revealed a significant main effect (F(1, 17) ¼ 18.81, p < .001), indicating that the new words elicited a larger negativity than the given words (Fig. 1). For the midline electrodes, similar results were found. A significant main effect of Focus (F(1, 17) ¼ 35.34, p < .001) and an interaction between Focus and Anteriority (F(2, 34) ¼ 15.15, p < .001) were observed, with the Focus effect being most prominent for the central region (anterior region: F(1, 17) ¼ 11.65, p < .01; central region: F(1, 17) ¼ 38.07, p < .001; posterior region: F(1, 17) ¼ 37.02, p < .001). A significant main effect of Newness (F(1, 17) ¼ 22.13, p < .001) and an interaction between Newness and Anteriority (F(2, 34) ¼ 4.34, p < .05) were also observed, with the Newness effect being most prominent over the central region (anterior region: F(1, 17) ¼ 12.11, p < .01; central region: F(1, 17) ¼ 23.94, p < .001; posterior region: F(1, 17) ¼ 13.00, p < .01). There was no interaction between Focus and Newness (Fs < 1).

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A Topography: Focus - Nonfocus 5 uv

-5 uv 150-250 ms

250-500 ms

500-700 ms

B Topography: New -Given 3 uv

-3 uv 150-250 ms

250-500 ms

500-700 ms

Fig. 2. The topographic maps showing the average differences between focus and non-focus conditions (A) and between new and given conditions (B) for the indicated time intervals.

3.2.3. 500e700 ms (LPC) The analysis of the lateral electrodes revealed a significant main effect of Focus (F(1, 17) ¼ 34.52, p < .001), indicating that the focused words elicited a larger positivity than the non-focused words (Fig. 1). There was a significant interaction between Newness and Anteriority (F(2, 34) ¼ 7.58, p < .01), showing a smaller positivity for the new words than for the given words over the anterior region (anterior region: F(1, 17) ¼ 5.08, p < .05; central and posterior regions: Fs < 1.2) (Fig. 2). For the midline electrodes, the analysis revealed a significant main effect of Focus (F(1, 17) ¼ 25.29, p < .001) and an interaction between Focus and Anteriority (F(2, 34) ¼ 3.91, p < .05). Further analysis showed that the effect of Focus was significant for all the three regions, which was most pronounced over central electrodes (anterior region: F(1, 17) ¼ 19.85, p < .001; central region: F(1, 17) ¼ 23.78, p < .001; posterior region: F(1, 17) ¼ 13.61, p < .01). Besides, the analysis also revealed a significant interaction between Newness and Anteriority (F(2, 34) ¼ 4.12, p < .05), though further analysis showed no effect of Newness in any of the regions (Fs < 1.7). For both the lateral and midline electrodes, there was no interaction between Focus and Newness (Fs < 1). In sum, the focused words elicited an enhanced P2 (broadly distributed, and left central prominent), a reduced N400 and an enhanced LPC (broadly distributed, and central prominent) compared to the nonfocused words. In addition, the results revealed an enhanced N400 (broadly distributed, and central prominent) and a reduced LPC (anterior distributed) for the new words than for the given words. 4. Discussion The present study aimed to distinguish between focus and newness by comparing brain responses to the target words in different conditions. The results showed that the focused words elicited a larger

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P2, a smaller N400 as well as a larger LPC than the non-focused words, whereas the new words elicited a larger N400 as well as a smaller LPC compared to the given words. No interaction was found between focus and newness. The fact that focus and newness elicited different ERP effects supported our hypothesis that focus and newness involve different cognitive processes. 4.1. The focus effect The focused words elicited a larger positivity than the non-focused words in the 150e250 ms time window. This effect was broadly distributed and was more prominent over the left central region. Give its peak latency, we took it as a P2 effect. The P2 component has been related to attention allocation, , Mercado, with attended stimuli eliciting larger P2 amplitudes than un-attended stimuli (Carretie Tapia, & Hinojosa, 2001; Hillyard & Münte, 1984; Luck & Hillyard, 1994). Previous linguistic and psycholinguistic studies have suggested that the focused elements gained more attention than the nonfocused elements (Chen et al., 2012; Gundel, 1999; Klin et al., 2004; Sanford, Sanford, Molle, & Emmott, 2006; Wang et al., 2009). For instance, previous behavioral studies using the changedetection paradigm (e.g., Sanford et al., 2009; Sturt et al., 2004) have revealed that the changes in the focused words were detected more frequently and quickly than those in the non-focused words, which may reflect that more attention was allocated to the focused words than the non-focused words. Previous eye movement studies (e.g., Birch & Rayner, 2010; Chen et al., 2012; Morris & Folk, 1998) have revealed that the focused words were processed more quickly than the non-focused words, showing the facilitation of focus. This facilitation effect can also be explained by the attention allocation induced by focus. More direct evidence comes from an fMRI study (Kristensen, Wang, Petersson, & Hagoort, 2013), in which focused information marked by pitch accent activated a frontoparietal attention network to a larger degree than non-focused information. Since the P2 component has been associated to attention allocation, the present finding of the larger P2 for the focused information than for the non-focused information provides direct ERP evidence on the role of focus in modulating attention allocation. Then an interesting question is why previous ERP studies failed to observe the P2 effect of focus. There may be two possible reasons. First, the P2 effect might overlap with other effects observed in previous studies. In the study by Cowles et al. (2007), the focused words elicited a larger long-lasting positivity (200e800 ms) compared with the non-focused words. This was interpreted as a P3b effect. However, considering the early onset latency of this positivity (200 ms), it is possible that the positivity was comprised of both an early P2 and a relatively late P3b effect. Another possibility is that the use of specific focus-marking device may play an important role in the elicited ERP effects. In the present study, the focus particle “shi” was located in front of the focused element in the sentence. Thus, the readers were able to take the particle as an effective cue to immediately allocate attention to the focused element. In contrast, wh-question context, as another device to mark focus, projects a focus using the question context which precedes and separates from the focused element in the answer sentence. This difference may have altered the time course of attention allocation. This interpretation was supported by several studies which showed that different focus-marking devices played different roles during sentence processing (Drenhaus, Zimmermann, & Vasishth, 2011; Filik, Paterson, & Liversedge, 2009). For instance, the use of ‘only’ and ‘it-cleft’ structure were shown to have different semantic constraints on upcoming information, and resulted in different ERP effect. Following the P2 component, the focused words also elicited a reduced N400 and an enhanced LPC compared to the non-focused words. Given the similar distribution of the N400 and LPC effects, we tended to take them as a single, long-lasting positive effect in the time interval of 250e700 ms. This positive effect has been reported in previous studies (Bornkessel et al., 2003; Cowles et al., 2007). Based on the interpretation from previous studies, it could be interpreted as a P3b effect (Bornkessel et al., 2003; Cowles et al., 2007), suggesting that readers engaged in integrating focused words into discourse context to a larger degree than non-focused words. According to Cowles et al. (2007), the focus-marking device sets an empty slot in the discourse context. Then the focused element fills this slot, which induces the integration of the focused element immediately. Thus, a larger positivity was elicited by the focused than the non-focused words. However, it is also possible that different ERP

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components have similar scalp distributions, so the N400 and LPC effects might reflect different cognitive processes. For instance, the smaller N400 for the focused than the non-focused words might suggest that the focused words were easier to process and integrate into context than the non-focused words because the focused words received more attention than the non-focused word (as indicated by the preceding P2 effect). Additionally, the LPC effect might be related to a previously reported closure positive shift (CPS) effect. The CPS typically starts at about 500 ms post-target onset and is related to the pause in a sentence (Li & Yang, 2009; Steinhauer, Alter, & Friederici, 1999). In the present study, the focused element was marked by using a focus-particle “shi”, which plays the same role as the English cleft-structure. The cleft may break the structure of the sentence and thus make a pause in the sentence in silent reading, resulting in a CPS effect. Regardless of the interpretations, the observed ERP effects suggest that focused words were integrated into previous contexts differently from nonfocused words. One might take the P2 effect and its following positive effect as being one extended positive effect. However, we were inclined to take them as being two effects for two reasons. First of all, the distribution of the P2 effect differed from the following positive effect (i.e., the combination of the N400 and LPC effects). Thus, different neural activities might be involved underlying these two effects. Second, the interpretation of the P2 effect is consistent with previous behavioral and fMRI studies showing that focused information obtained more attentional resources than non-focused information. The one-extended positive effect was mainly taken as a reflection of facilitated integration of focused information, which is inconsistent with our interpretation of the attention effect. Therefore, we tended to interpret the finding as an early P2 effect (indicating more attention allocated to focused than non-focused words) combining with later integration effects (a long-lasting P3b effect indicating the on-line integration of the focused words, or a reduced N400 effect indicating the facilitation of the integration of the focused words). This interpretation was derived from both the waveforms and distributions of the present ERP effect and the indications of previous behavioral/eye movement studies. 4.2. The newness effect The new words elicited a larger negativity than the given words in the 250e500 ms time window. Based on its eliciting condition, morphology and topography (central maximal), we took this negativity effect as an N400 effect (Gonzalez-Marquez, Mittelberg, Coulson, & Spivey, 2007; Kutas & Federmeier, 2011; Kutas & Hillyard, 1980; Lau, Almeida, Hines, & Poeppel, 2009; van Berkum, Hagoort, & Brown, 1999). The N400 was shown to be sensitive to lexical retrieval or integration difficulty, so the larger N400 elicited by the new information indicates that the new information was more difficult to be retrieved or integrated into previous context. The target words in the given information condition are repeated words. Thus, there is an alternative explanation of the N400 effect: that the effect was not in fact caused by the processing of newness in the discourse-level, but simply owed to the word-form priming. It is hard to exclude this explanation using the data from the present study. Fortunately, several previous studies have supported the contribution of discourse-level newness processing to the N400 effect (Benatar & Clifton, 2014; Besson & Kutas, 1993; Besson, Kutas, & van Petten, 1992; Li et al., 2008). For example, in an ERP study, Besson and Kutas (1993) compared the brain responses elicited by repeated words and new words in the repeated and new contexts. The results showed that the new words in the repeated context elicited a smaller N400 than the repeated words in the new context. Thus, although it is hard to dissociate the effect of lexical priming from the present N400 effect, at least part of the N400 effect is contributed from the discourse-level newness processing. In the 500e700 ms time window, the new words elicited a smaller positivity than the given words over bilateral anterior regions. There are two possible interpretations for this positivity. First, it may be a reduced LPC effect for the new words relative to the given words. Second, it can also be taken as an enhanced negativity for the new words relative to the given words, that is, a prolongation of the preceding N400 effect in the 250e500 ms time window. However, because the preceding N400 effect was most prominent over the central region, while the present positivity/negativity was distributed over the anterior region, we tended to take it as an LPC rather than a prolongation of the preceding

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N400 effect. The LPC component was suggested to be sensitive to word repetition (Kutas & Federmeier, 2011; Olichney et al., 2000; Rugg, 1985; Rugg & Curran, 2007) and reflect memory retrieval of repeated words (van Petten et al., 1991). In the sentence and discourse context, this effect also occurred when the critical words were proper names (van Petten et al., 1991). In the present study, the given name triggered memory retrieval processes of its antecedent, whereas the new name could not be related to any information in memory or in previous context. Thus, no such memory retrieval process was necessary for the new name. Therefore, it is highly possible that the larger LPC effect elicited by the given name was associated with the memory retrieval processes. 4.3. The relationship between focus and newness In sum, focus was associated with attention allocation and immediate integration, whereas newness was associated with difficult integration and memory retrieval. These results suggest that focus and newness are dissociable and involve different cognitive processes. These findings are in agreement with our previous findings in the eye movement study (Chen et al., 2012). However, our previous eye tracking study revealed different processing patterns of focus and newness in the target region as well as an interaction between focus and newness in the post-target region, whereas the present ERP study only showed different brain responses to focus and newness without any interaction. This apparent difference suggests that the interaction in the post-target region found in the eye tracking study was more an indication of post-target word integration than a delayed effect of the target word. In the present ERP study, the allowed processing time for a word was 700 ms. This provided enough time for the participants to process the word thoroughly and thus the effects of the word should occur immediately rather than delay to the succeeding word. Now that in this situation we did not observe the interaction between focus and newness, it seems that the interaction was not associated with the processing of the target word itself. In contrast, it was associated with the integration of both the target words and the post-target words. Moreover, this can also explain the difference between the present study and Ledoux et al. (2007). Ledoux et al. (2007) found an interaction between focus and newness. However, the focus status was manipulated on the antecedent, whereas the interaction effect was observed on the anaphor. Thus, their observed interaction effect could be associated with the later integration of the focused word. These findings support a distinction between focus and newness from a neurocognitive perspective. ry & Krifka, 2008; Fe ry & Ishihara, This is in line with previous acoustic studies (Beaver et al., 2007; Fe 2009; Katz & Selkirk, 2011; Selkirk, 2008, 2002), in which different prosodic patterns were found among contrastive focus, new information, given information and second occurrence focus (SOF, a focused entity which is focused for the second time). By revealing different brain responses elicited by focus and newness, the present study indicates the importance of distinguishing between focus and newness, which has been neglected in a number of previous studies (Breen et al., 2010; Zimmer & Engelkamp, 1981). These findings also provide some insight into the theories of discourse comprehension. For instance, our data are consistent with the specification of the MUC (Memory, Unification and Control) model (Hagoort, 2013), which proposed that language processing can be subdivided into three components: memory, unification and control. During discourse comprehension, readers retrieve lexical semantic information and subsequently combine them to form a coherent mental representation of the language input. These processes relate to memory retrieval and unification components respectively. Moreover, these two processes are subjected to the control component such as attentional control. Newness and focus may associate with different components. On the one hand, newness relates to memory retrieval, which might be under the influence of focus marking. On the other hand, focus marker ‘shi’ modulates attentional resources, which serves as a general control for language processing. Hence, during discourse comprehension, focus and newness could be associated with different components of language processing. In conclusion, the present study examined brain responses elicited by two types of information structure (i.e., focus and newness), and provided evidence to distinguish them as two different concepts. The focused words elicited a larger P2 (150e250 ms) and a long-lasting positivity (250e700 ms) than the non-focused words, reflecting attention allocation and immediate integration of focus

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respectively. In contrast, the new words elicited a larger N400 (250e500 ms) and a smaller LPC (500e700 ms) than the given words, indicating semantic integration difficulty and memory retrieval for newness. Hence, focus and newness involve different cognitive processes, and thus they play different roles in discourse comprehension and should be treated separately in the process of information structure. Acknowledgments This work was supported by the National Natural Science Foundation of China (31070989). We would like to thank Weijun Li for her help in conducting the experiment, Aishi Jiang and Shuzhen Gan for their help in the data analysis, Xiaohong Yang for her help in proof reading the manuscript, and two anonymous reviewers for their help in improving the manuscript. References Almor, A. (1999). Noun-phrase anaphora and focus: the informational load hypothesis. Psychological Riview, 106, 748e765. Anderson, J. E., & Holcomb, P. J. (2005). 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