Multiple semantic processes at different levels of syntactic hierarchy: does the higher-level process proceed in face of a lower-level failure?

Humans have special abilities in processing hierarchical, recursive structures. Here we investigated how an upcoming word embedded in a hierarchical structure is semantically integrated into the prior representation during sentence comprehension. Participants read Chinese sentences with a complex verb argument structure "subject noun+verb+numeral+classifier+object noun", in which the object noun was constrained by the classifier in a local structure and by the verb in a higher-level structure. The semantic congruence between the classifier and the noun, between the verb and the noun, and between the verb and the classifier was manipulated individually or simultaneously to create a local mismatch (i.e., with classifier-noun mismatch), a sequential mismatch (with verb-classifier and classifier-noun mismatches) or a triple mismatch (with verb-classifier, classifier-noun, and verb-classifier mismatches) condition. Event-related potentials locked to the object noun showed increased N400 and late negativity responses over the local mismatch, the sequential mismatch and the triple mismatch conditions. The local mismatch additionally elicited a posterior positivity effect on the object noun. The verb-classifier mismatch elicited a right N400-like effect followed by a posterior positivity (P600) effect on the classifier. The N400 effects demonstrate that the semantic process at a higher syntactic level can proceed in face of the failure of semantic processes at lower levels when no structural re-interpretation is available, and that the semantic congruence between earlier sentence constituents can affect the integration of the upcoming word in the hierarchical structure. The P600 effects suggest the immediate triggering of a co-ordination process across syntactic levels whereas the late anterior negativity effects suggest the initiation of a second-pass semantic re-interpretation process.