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

ORIGINAL RESEARCH published: 14 November 2019 doi: 10.3389/fnhum.2019.00398 Distinguishing Old From New Referents During Discourse Comprehension: Evidence From ERPs and Oscillations Mante S. Nieuwland 1,2* , Cas W. Coopmans 1,3 and Rowan P. Sommers 1 1 Max Planck Institute for Psycholinguistics, Nijmegen, Netherlands, 2 Donders Institute for Brain, Cognition and Behaviour, Nijmegen, Netherlands, 3 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 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; Frontiers in Human Neuroscience | www.frontiersin.org 1 November 2019 | Volume 13 | Article 398 Nieuwland et al. Old and New Discourse Referents 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. 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 Yekovi (...truncated)