Evaluating an Expectation-Driven QUD Model of Discourse Interpretation

According to Question-Under-Discussion (QUD) models of discourse interpretation, clauses cohere with the preceding context by virtue of providing answers to (usually implicit) questions that are situated within a speaker’s goal-driven strategy of inquiry. In this paper, we present four experiments that examine the predictions of a QUD model of interpretation when cast in terms of an integrated, expectation-driven model of discourse processing. The results of these studies together support the predictions of the model, demonstrating that contextual cues affect comprehenders’ expectations about ensuing QUDs (Experiment 1), QUD expectations in turn influence the interpretation of discoursedependent linguistic expressions (Experiment 2), and the biases associated with those expressions in turn influence the anticipation of QUDs (Experiments 3a/b). Pronouns in a QUD Model 2 Evaluating an Expectation-Driven QUD Model of Discourse Interpretation In a conversation that recently transpired, a linguist named Andy said the following to his collaborator Hannah: (1) We should write a paper. There’s a special issue of Discourse Processes coming up that will be dedicated to QUDs. A conversation ensued in which Hannah asked Andy about the timeline for the special issue, they compared schedules, and so forth: Hannah clearly inferred that the paper Andy had in mind would be for the special issue. That’s strange; Andy didn’t actually say that. Of course, Hannah did what hearers typically do: They don’t generally interpret co-occurring statements as independent facts about the world, but instead assume that the statements are somehow relevant to one another. According to contemporary theories of discourse interpretation, this assumption of relevance, and the inferences that comprehenders must draw to maintain it, result from the need to establish the COHERENCE of a discourse. In fitting with the theme of the special issue, the work reported here examines the Question Under Discussion (QUD) analysis of coherence, pursued in different instantiations by researchers including Carlson (1983), Klein and Stutterheim (1989), Kuppevelt (1995), Roberts (1996), Ginzburg (1996), Larsson (1998), and Ginzburg and Sag (2000). In QUD analyses, discourses are structured by question/answer relationships: Roughly speaking, an utterance is coherent insofar as it provides an answer to a (generally implicit) question that is relevant to the preceding discourse. For instance, in unexceptional circumstances, the second sentence of (1) will be interpreted to answer the question Why? with respect to the eventuality described by the first. Importantly, the second sentence can only be understood to answer this question if it is assumed that the paper is being written for the special issue. Although by no means entailed by the passage, this assumption is easily accommodated by the addressee in the absence of any beliefs to the contrary. Pronouns in a QUD Model 3 Indeed, if Andy had later commented Oh, I don’t think we should submit to the special issue; I was thinking about a different paper, Hannah would have been rightfully confused, and perhaps even have dropped her joint projects with Andy in favor of working with other, presumably more sane, collaborators. QUD analyses reflect a complex interplay between the linguistic characteristics of a speaker’s contribution and her underlying communicative intentions in producing it. In the QUD analysis set forth by Roberts (2012/1998), for instance, the coherence of discourse fundamentally depends on the conversational goals that interlocutors have and the STRATEGIES OF INQUIRY they employ to satisfy them. She suggests, following Stalnaker (1979), that discourse is to be viewed as an attempt by conversational participants to discover and share “the ways things are” (or, to phrase it another way, to answer the question What is the way things are? ). Thus, by engaging in a conversation, the interlocators agree to jointly adopt goals that center around finding answers to this question. This in turn will generally necessitate the adoption and satisfaction of subgoals centered on answering sub-questions, giving rise to a hierarchical discourse structure. On the QUD model, therefore, understanding a discourse requires that hearers not only understand the particular utterances in the discourse, but also recover the questions they answer, and situate those questions within the underlying strategy of inquiry. This paper sets out to explore the ramifications of adopting a QUD model for the study of sentence and discourse processing, and conversely, to examine using sentence and discourse processing data how QUDs might be utilized during interpretation. Two possibilities for processing models come immediately to mind. First, according to a REACTIVE model of processing, comprehenders will first compute interpretations of individual utterances, and then use linguistic cues, world knowledge, and inference to determine the identity of the QUD and to integrate the utterance into the larger discourse. On this type of bottom-up view of language processing, the interpretation of linguistic input affects the identification of the QUD, but not the other way around. Whereas this picture is perfectly compatible with many linguistic theories that invoke QUDs in treatments of different phenomena, it seems unlikely in light of a substantial line of research that shows that interpretation is incremental and probabilistic at various levels of Pronouns in a QUD Model 4 linguistic processing (Crain & Steedman, 1985; Altmann, 1988; and many others). This research would instead suggest an alternative EXPECTATION-DRIVEN model of processing, according to which comprehenders are anticipators who use contextual cues to generate expectations about where the discourse is going in terms of the QUDs to which subsequent sentences will provide answers. On this model, evidence for the ensuing QUD may come from any of a number of contextual sources; examples that have been posited in the literature include focus marking and accent placement (Roberts, 2012/1998; Büring 2003), the semantic type of the verb appearing in a context sentence (Kehler et al., 2008), aspect (H. Rohde et al. 2006), the typicality of objects of transfer in transfer-of-possession events (H. Rohde et al., 2007, Experiment 1), and the existence of indefinites, disjunctions, and/or existential quantifiers in a context sentence (Anderbois, 2011), among others. The advantage of computing such expectancies for the comprehender is that the ensuing linguistic material will be easier to process when their expectations prove to be correct. Confirmation of the predictions of a QUD analysis would thus suggest that QUDs need to be taken into account in theories of discourse-dependent linguistic forms if these theories are to be empirically adequate. This paper describes a series of experiments designed to examine three predictions of an expectation-driven QUD model of discourse processing. First, the model predicts that discourse participants will use contextual clues to create expectations about the ensuing QUD that a subsequent utterance will answer. Experiment 1 asks whether we find such evidence. The results from participants producing questions in a simple dialog task demonstrate that different contexts yield different distributions of questions. The second prediction is that comprehenders will bring QUD-level expectations to bear when interpreting linguistic expressions that are highly discourse dependent. 1 A remaining question, not addressed by the current work, is whether such evidence strongly favors QUD analyses over other analyses of discourse coherence on offer. We return to this question in the General Discussion. 2 Von Kuppevelt (1995) in fact proposed that a set of possible questions arise in a listener’s mind during discourse comprehension, and that these questions are entertained as ones that may be answered in subsequent discourse. He leaves open the question of which factors in a context contribute to the anticipation of these upcoming questions, however. Pronouns in a QUD Model 5 Experiment 2 examines third-person pronouns as a case study: Can we find evidence that QUDs affect the incremental assignment of referents to pronouns? The results answer this question affirmatively using a self-paced reading task in which the participants were told what QUD a pronoun-containing clause would answer. Lastly, a fully integrative expectation-driven model would also predict that the interaction between inferring implicit QUDs and interpreting linguistic expressions should be bidirectional, that is, that encountering linguistic material will introduce new biases that will in turn update expectations about QUDs. Experiments 3a/b address this question with passage completion studies, showing that the mere occurrence of an ambiguous pronoun in the completion prompt – a form which is known to carry its own referential biases – has a significant effect on the distribution of questions that the completions answer. The results are highly consistent with the predictions of an integrated, expectation-driven QUD model of discourse processing in which the anticipation of QUDs affects the interpretation of linguistic expressions, and the interpretation of linguistic expressions in turn affects the anticipation of QUDs. Experiment 1: The Effect of Context on QUDs According to the expectation-driven QUD model, addressees not only establish the implicit QUD that a clause answers when they interpret discourses, they also use contextual cues to generate expectations about ensuing QUDs. We investigated this prediction as part of a larger study that also examined the predictions of a RELATIONAL approach to discourse coherence (e.g., Hobbs 1990, Asher and Lascarides 2003). According to the relational approach, establishing coherence between utterances is based on making the inferences necessary to meet the con