Scope of superordinate categorisation modulates semantic radical effects in Chinese word reading: an ERP study

Semantic radicals facilitate Chinese word recognition, but how their neural effects are modulated by conceptual scope remains unclear. We conducted two ERP experiments using narrow-scope (animal/plant) and broad-scope (natural/man-made) categorisation tasks. The results revealed a profound task-dependent modulation of radical effects across both early (N400) and late (LPC) processing stages. In the narrow-scope task, the N400 effect showed a topographical dissociation (posterior for plants vs. anterior for animals), and the LPC effect was stronger for animals, suggesting specialised processing pathways. In contrast, for the broad-scope task, radical facilitation in both the N400 and LPC was observed only for natural objects. We propose a “radical diagnosticity” framework to unify these findings, positing that the brain dynamically assesses a radical’s utility for the current judgment. This framework is formalised in a Diagnosticity-Driven Model (DDM), which specifies how top-down task demands gate the influence of bottom-up orthographic cues.