N400 differences between physical and mental metaphors: The role of Theories of Mind

Whether Theory of Mind (ToM) contributes to metaphor understanding has been largely investigated in language acquisition and decay. Yet we know very little about the role of ToM in real-time processing of metaphors in neurotypical adults. Here, we tested the relationship between ToM and metaphor through Event Related Potentials (ERPs) by capitalizing on the difference between metaphors inviting inferences on physical (Boxers are pandas) vs. mental aspects (Teachers are books). Physical metaphors involved a larger and sustained negativity compared to mental ones. This pattern resembled concreteness effects and suggests that physical metaphors may benefit from both verbal and perceptual information. Moreover, higher scores in the Reading the Mind in the Eyes Test (RMET), but not in the Animation task, were associated with a reduction of the N400 amplitude for both physical and mental metaphors. When exploring the ERP temporal trajectory with Generalized Additive Mixed Modeling, earlier differences between metaphors characterized individuals with higher RMET scores. Among the various ToM components, thus, emotion recognition seems to be involved in the processing of metaphors in general, with an earlier impact on the mental type. These findings highlight the multifaceted nature of metaphor, at the crossroad of language, social and perceptual experience.