Temporal Dynamics of Morphological Priming: A Comparison with Orthographic and Semantic Priming in Event-related...

While the unmasked priming paradigm has effectively revealed a biphasic pattern of morphological decomposition-characterized by early morpho-orthographic segmentation followed by later morpho-semantic integration-it remains unsettled which ERP components reliably reflect these distinct stages of morphological processes. To address this, we systematically compared ERP responses across three priming conditions-morphological (e.g., swiftly-swift), orthographic (e.g., surgeon-surge), and semantic (e.g., explode-burst)-focusing on the N250, early N400, late N400, and late negativity (LN). The N250 showed no facilitative effects and instead exhibited increased negativities across all conditions, challenging its reliability as a marker of early morpho-orthographic processing under unmasked priming. In contrast, both the early and late N400 subcomponents provided consistent indices of morpho-orthographic segmentation and morpho-semantic integration, respectively. In the early N400, morphological priming elicited earlier and stronger negativity attenuation than orthographic priming, with minimal semantic influence, reflecting semantically blind morpho-orthographic segmentation. In the late N400, negativity attenuation for morphological priming was further amplified and exceeded that of semantic priming, indicating morpho-semantic integration via shared morphemes. Notably, we also observed a unique biphasic orthographic priming pattern with embedded word targets: a relatively short and weak early N400 attenuation followed by an LN peak, reflecting initial facilitation from embedded word identification and subsequent lateral inhibition between orthographically related but semantically unrelated words. These findings establish the early and late N400 as robust ERP signatures of biphasic morphological processing under unmasked priming and elucidate the temporal dynamics of morphological, orthographic, and semantic processes.