The N400 reflects problems of thematic hierarchizing.

Using event-related potentials (ERPs), we present evidence that the current interpretation of the N400 component must be extended. This component is elicited in incorrect German sentences with two grammatical subjects, thereby showing its sensitivity to thematic relations between arguments in a sentence (who is doing what to whom). Such a violation only elicits an N400 when both arguments are animate but not when one of them is animate and the other inanimate, thus showing that the brain uses animacy information to overcome interpretation problems due to thematic competition. Structures with two subjects additionally elicit a P600 component which occurs independently of the animacy variation. Thus, animacy information does not appear to influence the syntactic processing problems resulting from such violations.