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Poster E33, Friday, November 10, 10:00 – 11:15 am, Harborview and Loch Raven Ballrooms

The shared and dissociable neural substrates of generalized and particularized conversational implicature

Wangshu Feng1,2, Hongbo Yu1,3, Xiaolin Zhou1,2,4,5,6;1Center for Brain and Cognitive Sciences, Peking University, Beijing 100871, China, 2School of Psychological and Cognitive Sciences, Peking University, Beijing 100871, China, 3Department of Experimental Psychology, University of Oxford, OX1 3UD, Oxford, UK, 4Key Laboratory of Computational Linguistics, Ministry of Education, Peking University, Beijing 100871, China, 5Beijing Key Laboratory of Behavior and Mental Health, Peking University, Beijing 100871, China, 6PKU-IDG/McGovern Institute for Brain Research, Peking University, Beijing 100871, China

In daily conversation, the listener often has to infer the speaker’s intended meaning beyond the literal information conveyed by the utterance. Such non-literal meaning is conversational implicature, which can be categorized into generalized conversational implicature (GI) and particularized conversational implicature (PI). GI can be obtained without knowing the context of utterance, whereas PI is based on specific context (Grice, 1975). It is controversial whether GI and PI involve identical or distinct cognitive processes. Neuroimaging studies have found that the generation of GI elicits increased activation in mPFC, MFG, and left IFG, whereas the generation of PI engages the theory-of-mind (ToM) network, including mPFC and TPJ, and the core language network, including IFG and MTG. The current study aimed to identify the shared and distinct neural processes underlying GI and PI by comparing them in the same experiment. To this end, we presented participants with simple dialogue scenes in which one interlocutor asked a question and then another interlocutor gave a reply, following a cover story. The reply was indirectly related to the question; understanding its meaning either required knowledge of the context (PI) or did not (GI). For their respective controls (i.e., NG and NP), essentially the same sentence was used as a direct reply to the preceding question. Twenty-eight participants made binary judgment as to whether the reply was intended to provide a yes or no answer to the question while undergoing fMRI scanning. They also completed a ToM localizer task after the main task. A conjunction of the contrast between GI and its control and the contrast between PI and its control revealed activity in bilateral IFG, left MTG, and mPFC, indicating shared neural substrates for understanding GI and PI. In line with this, multivariate fMRI pattern classifiers accurately (>95%) discriminated GI and PI from their respective controls. Moreover, the classifier trained on GI from its control could cross-discriminate PI from its control, and vice versa, suggesting that GI and PI elicit shared neural representations. We also examined the extent to which language and ToM processing could classify the neural representations of GI and PI. Independently defined Language and ToM prototypical brain patterns, either by a meta-analytic database ("Language”) or by the localizer task (“ToM”), were applied to discriminate GI and PI with their respective controls. The “Language” pattern could discriminate both GI/NG and PI/NP, but performed at chance level when discriminating PI/GI, indicating that both PI and GI engage the identical pattern of language processing. By contrast, the ToM pattern performed at chance level in discriminating GI/NG, while performing significantly above chance in discriminating both PI/NP and PI/GI, suggesting that the ToM-related inferential process is unique to PI. Taken together, our findings show that PI and GI processing are neither identical nor completely distinct; instead, our data suggest that, while PI and GI have overlapping neural processes, the difference between these two implicatures is in the involvement of ToM and intention consideration.

Topic Area: Meaning: Discourse and Pragmatics

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