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Beyond Literal Meaning: A Quantitative Meta-Analysis of N400 and Post-N400 Effects in Figurative Language through Waveform Digitization
Poster Session A, Wednesday, September 30, 11:00 am - 1:00 pm, Wangari Maathai
Paolo Canal1, Francesco Vespignani2, Veronica Mangiaterra3, Fabrizio Luciani1, Federico Frau1, Luca Bischetti1, Valentina Bambini1; 1Laboratory of Neurolinguistics and Experimental Pragmatics (NEPLab), University School for Advanced Studies IUSS, Pavia, Italy, 2Dipartimento di Psicologia dello Sviluppo e della Socializzazione, Università di Padova, Padova, Italy, 3Laboratoire de sciences cognitives et psycholinguistique, École normale supérieure ENS, Paris, France
The time course of figurative language processing in metaphor, idioms, and irony has been investigated via Event Related Potentials (ERPs), often reporting N400 effects. More debated is the presence of post-N400 activity, which, when reported, may take the form of sustained negativities or late positivities [1]. Such variability in the ERP pattern after the N400 calls into question the existence of a “pragmatic P600”. Synthesizing ERP findings is thus crucial, yet quantitative meta-analyses remain difficult because ERP studies vary in the selection of time windows and electrodes of interest, and often do not report effect sizes. To address these limitations, we propose a novel analytical framework that builds on previous waveform digitization approaches [2] to model continuous ERP data across studies. A systematic review identified 66 articles meeting the inclusion criteria: a) the presence of a literal control condition, and b) ERP plots spanning at least -100 to 800 ms. Articles were annotated, and plotted waveforms were digitized and mapped onto a common electrode space. Using a Bayesian framework, we estimated the probability of N400 and P600 effects across frontal and posterior electrodes within conventional time windows, with variance imputed from sample and stimulus sizes. Generalized Additive Modeling (GAM) was then applied to analyze continuous non-literal/-literal differences without predefined temporal windows. We first focused on the two most commonly tested time windows (early: 300-500ms; intermediate: 600-800ms). During the early window, metaphors elicited a larger N400 at posterior electrodes (-0.79 μV, [-1.16, -0.44], 100% posterior probability), whereas irony yielded no reliable differences. In the intermediate window the negative shift for metaphors persisted posteriorly (-0.32 μV, [-0.61, -0.03], 96% probability), while irony exhibited a distinct positive shift in posterior electrodes (+0.53 μV, [0.06, 0.98], 97% probability). Crucially, GAM pointed to a delayed effect for metaphors in a subsequent interval (late: 800-1000ms), revealing moderate evidence of a late frontal positivity (+0.20 μV, [-0.14, 0.54], 83% probability), alongside sustained positivities for irony. Idiom results were inconclusive. We confirmed that metaphor comprehension is associated with a robust N400 effect [3], likely extending into the intermediate window and often followed by a late frontal positivity. Conversely, irony primarily elicits posterior P600 without marked semantic difficulties. Collectively, we take these findings to reflect the complexity of pragmatic inferential processes continuing after the N400 and culminating in late positivities. Differences in latency and topography may account for the more lexical (metaphor) or more social (irony) nature of the non-literal phenomena. More broadly, this work shows that waveform digitization provides a standardized and scalable framework for synthesizing ERP findings while minimizing inconsistencies arising from study-specific analytical choices. [1] Canal, P. & Bambini, V. (2023). Pragmatics Electrified. In Grimaldi, M., Y. Shtyrov & E. Brattico, (Eds.), Language Electrified. Springer. [2] Sambrook, T. D., & Goslin, J. (2015). A neural reward prediction error revealed by a meta-analysis of ERPs using great grand averages. Psychol.Bull., 141(1), 213. [3] Baiocco, L., Kielar, A., & Lai, V. T. (2026). Metaphor comprehension in neurotypical adults: A scoping review of event-related potential studies. CABN, 1-31.
Topic Areas: Meaning: Discourse and Pragmatics, Methods