Fine-Grained Concreteness Effects on Word Processing and Representation Across Three Tasks: An ERP Study.

People process concrete words more quickly and accurately than abstract ones-the so-called "concreteness effect." This advantage also reflects differences in how the brain processes and stores concrete versus abstract words. In this electrophysiological study, we treated word concreteness as a continuous variable and examined its effects on ERPs across three tasks with distinct processing demands (semantic, affective, grammatical). Behavioral results revealed task-dependent concreteness effects: in the semantic task, reaction times were faster for words at both concreteness extremes, and the classical linear advantage emerged for concrete words. Mass univariate ERP analyses revealed distinct spatiotemporal patterns of task-dependent concreteness effects. In the semantic task, we identified three significant clusters reflecting increased parietal N2/P3-like and sustained bilateral fronto-temporal negativity ERPs and decreased central N400-like ERP for abstract words. By contrast, the affective task elicited an increased parietal P600-like ERP for abstract words. Moreover, results from multivariate representational similarity analysis and an intersection analysis revealed that concreteness is encoded in ERP spatiotemporal patterns from 450 ms onwards, regardless of task, suggesting its role not only as an organizational principle in semantic representation, but also as a factor influencing downstream word processing and univariate ERP concreteness effects. Our findings challenge and extend existing theories like the dual coding and context availability ones, highlighting the importance of treating concreteness as a continuous variable and considering task context in word processing studies. This approach, enabled by advanced analytical techniques, provides a more nuanced understanding of how the brain processes and represents words.