An N400/P600 trade-off in abstract priming: ERP evidence from phrasal processing

Through a structural priming paradigm, this ERP study investigated the abstraction of morphosyntactic representations and the neural mechanisms underlying the pre-activation of such representations to facilitate phrasal processing. Chinese verb phrases were constructed with a verb-object compound (VO compound, e.g., -to request a leave) and a position-flexible perfective aspect marker -le (V-O-le and V-le-O, e.g., both and mean requested a leave). By avoiding VO compound overlap and manipulating marker position congruence between the prime and target, the study assessed the conditions under which priming effects arise from the pre-activation of perfective representations. Grand-average ERPs indicated facilitation in both semantic (N400 reduction) and syntactic (P600 reduction) processing streams. Follow-up cluster analysis revealed these group-level effects to be artifacts of averaging across distinct subpopulations with different neurocognitive profiles. A P600-dominant group showed priming effects exclusively as modulation of the P600 component, reflecting a processing strategy focused on later syntactic reanalysis, whereas an N400-dominant group showed effects primarily in the N400 time window, indicating a strategy centered on earlier lexicosemantic integration. Further analyses within each subgroup revealed that the abstract representation of perfectivity was available at the phrasal level and that its activation was contingent on marker position within the phrase. The findings provide evidence not only for abstract morphosyntactic priming below the sentence level, but also for a functional N400/P600 trade-off in language processing, challenging unitary biphasic models and highlighting the need to incorporate systematic individual variation into the debate on syntactic versus semantic pathways of language comprehension.