Viviana Masia

Presupposition of new information as a pragmatic garden path: Evidence from Event-Related Brain Potentials

Abstract This study investigates the processing of presupposition in discourse through the Event-Related Brain Potential technique. While theoretical linguistics has largely described the phenomenon of presupposition, there is little empirical investigation, mainly from behavioural studies. Here we employed the Event Related Potential (ERP) technique to search for the brain signature of presupposition as opposed to assertion in discourse. Based on theoretical accounts, we hypothesized that presupposing new information should elicit higher efforts due to the mismatch between the information packaging and the actual knowledge, and to the need of accommodating the presupposed content in the mental model of discourse. We also hypothesized that these efforts could reflect in enhanced N400, similarly to other mechanisms operating at the discourse-context level. Twenty-seven participants were presented with passages containing new information packaged either as presupposition or as assertion. Two types of presupposition triggers were selected: definite descriptions and temporal subordinate clauses. Results evidenced a difference between the processing of presuppositions and that of assertions, reflected in a more enhanced N400 for the former. Results also showed that the temporal development of the presupposition effect is earlier for subordinate clauses than for definite descriptions. Differently from some behavioural studies on presupposition, but consistently with the theoretical literature and with other ERP studies on discourse processing, our data offer the first neurophysiological evidence that presupposition is more costly than assertion when new information is presented, with differences in the time development of the effect across trigger types. We proposed to account for the N400 effect induced by new presuppositions as stemming from a pragmatic “garden path” effect, in that, being presented with a new presupposition, the receiver is led down a mismatch between information packaging and discourse representation.

Brain response to Information Structure misalignments in linguistic contexts

Abstract The paper inquires, through the analysis of electroencephalographic (EEG) recordings, the processing costs associated to misalignments between the information status (Given/New) of discourse contents and their linguistic packaging as Topic or Focus in discourse. The way information is packaged within utterances, that is, their Information Structure, guides language comprehension. Sentences are typically organized into Topic and Focus units, commonly conveying Given (already active in working memory) and New (not active) information, respectively. Nonetheless, for precise purposes, novel information can be presented in Topic, and known information in Focus. The paper accounts for the efficiency of brain processing in response to such “violations” of Information Structure, through both EEG spectral analysis and whole-brain functional connectivity patterns. The main contribution of the present work is the analysis of brain responses in natural contexts, i.e. when processing whole texts of more sentences, instead of isolated (couples of) utterances as is the case of a number of experimental paradigms pursued in the psycholinguistic domain. EEG signals recorded from a population of 54 subjects highlight the presence of rhythmic changes in different frequency bands, depending on aligned and misaligned Information Structures.

N400 and P600 modulation in presupposition accommodation: The effect of different trigger types

Abstract This study investigates the neurophysiological correlates of presupposition processing in conditions of satisfaction and accommodation, comparing two types of triggers: definite descriptions and change-of-state verbs. Results showed that, for both types, the accommodation of presuppositions is associated with a biphasic N400-P600 pattern at the processing point. With definite descriptions, we observed a more clear involvement of the N400, while for change-of-state verbs the costs of accommodation were associated with a more pronounced P600. Moreover, when conveyed by change of state predicates, presuppositions seem to elicit also a P200 visible already at the trigger verb. The data nicely fit into the Linking-Updating model and support two main conclusions. First, presupposition accommodation is a sequential process unfolding through a biphasic ERP pattern presumably related to search for antecedent and discourse update. Second, the kind of presupposition trigger seems to affect the cognitive cost of presupposition accommodation at different processing times, with definite description capitalizing more on the earlier search for antecedent and change-of-state verbs capitalizing more on the later updating of the discourse mental model with the presupposed information. Overall, our findings suggest that the brain understands information taken for granted by going through a process whose time course involves several phases, differently modulated based on specific linguistic expressions.

Context-Dependent Information Processing

The ways language encodes information depend on when and how the preceding linguistic and non-linguistic context has established it in the participants’ working memory. Information-Structure categories such as Focus and Topic are used to signal that the conveyed information is, respectively, the contribution of the message to the addressee’s knowledge or simply something meant to link the message to the context. Information introduced within a context (“Given”) is expected to be encoded as a Topic, while “New” information is more likely to appear in Focus. The results of a dedicated EEG experiment will show that violation of such expectations causes supplementary processing costs, revealed by rhythmic changes in different frequency bands.