Incremental and predictive discourse processing based on causal and concessive discourse markers: ERP studies on German and English

Incremental and predictive discourse processing based on causal and concessive discourse markers: ERP studies on German and English Heiner Drenhaus (drenhaus@coli.uni-saarland.de) Saarland University, 66123 Saarbrucken Germany Vera Demberg (vera@coli.uni-saarland.de) Saarland University, 66123 Saarbrucken Germany Judith Kohne (judith.koehne@uni-bamberg.de) Otto-Friedrich-Universitat Bamberg, Germany Francesca Delogu (delogu@coli.uni-saarland.de) Saarland University, 66123 Saarbrucken Germany Abstract There is some evidence for both the hypothesis that discourse connectors facilitate text comprehension and the hypothesis that processing discourse connectors is highly incremental. Less, however, is known about the way in which different discourse connectors help comprehension and whether they can elicit predictions of upcoming contents. In the present ERP studies on German and English we investigated the effect of congruency and connector type (causal / concessive) on the prediction of a target referent (2x2 design). We found a fronto-central positivity for the concessive connector compared to the causal condition and an N400-like effect for the target noun phrase for incongruent compared to congruent conditions. Our results suggest an effect of context-updating at the connector (frontal positivity) and provide evidence for prediction of upcoming content based on the discourse connector. Keywords: Sentence Processing, ERP, N400; Frontal Positivity, Predictability, Discourse Connectors, Discourse Relations Introduction Discourse connectors (such as therefore, however, instead) have been shown to facilitate comprehension, at least when used appropriately (e.g., Millis & Just, 1994). It is, however, less clear in which way different types of discourse connectors help processing and, in particular, whether they elicit predictions of upcoming linguistic material. Existing work on the processing of discourse relations revealed that discourse connectors are rapidly and incrementally integrated with earlier parts of the discourse (e.g., Traxler et al., 1997). Previous research on the processing of discourse relations also suggests that people have some general cognitive biases when processing text, which lead them to more easily infer causal and continuous than, for instance, concessive discourse relations (Murray, 1995; Sanders, 2005; Brehm, 2005). Of particular relevance here is an ERP study by Kuperberg et al. (2011), who found evidence for a default to interpret adjacent sentences as standing in a causal relationship: causally unrelated scenarios induced a larger N400 than intermediately related scenarios which, in turn, elicited a larger N400 than causally related scenarios. The view that causal and continuous discourse relations are generally expected by comprehenders is also consistent with recent analyses of discourse relation marking in production data: Asr & Demberg (2012) find that causal and continuous discourse relations are less likely to be marked using explicit discourse connectors than other (presumably less expected) discourse relations. This observation is in accordance with the uniform information density hypothesis (Levy & Jaeger, 2007), which holds that optional linguistic elements (like discourse connectors) may be omitted when they do not convey much new information, i.e. when they mark an expected discourse relation. Taken together, these findings lead to the prediction that discourse connectors which signal discontinuity should be more difficult to process because they require a re-interpretation of the discourse relation that was assumed by default. In the present ERP studies on German and English, we compare the processing of causal versus concessive discourse connectors. Concessive discourse connectors represent an interesting comparison to causal connectors from a theoretical perspective, as they have been argued to represent the same type of relation but to differ in polarity (Louwerse, 2001; Sanders et al., 1992), and have sometimes been referred to as “negative causals” (Konig & Siemund, 2000). Previous work comparing the processing of causals and concessives in the visual world paradigm (Kohne & Demberg, 2013) showed that both causal and concessive discourse markers can be rapidly integrated into on-line comprehension and that processing the concessive leads to a search for alternatives. While the visual world paradigm is useful in revealing predictions during sentence comprehension through visual attention, it does not give much insight into the underlying processes. Kohne and Demberg’s experiment using eye-movements in reading additionally indicates highly incremental processing and prediction in causals. However, no evidence for incremental processing and rapid integration was found for concessives. The authors hypothesize that their results may be due to an increased difficulty of processing concessives, or of integrating them with upcoming content.