An ERP study of P600 effects elicited by semantic anomalies

Syntactic anomalies reliably elicit P600 effects. Recent studies, however, reported P600 effects to semantic anomalies. These findings are difficult to reconcile with the common view on the P600 as a purely syntactic component. The present study--carried out in Dutch--tested the possibility that a P600 to semantic anomalies would nevertheless reflect syntactic processing. We presented semantic reversal anomalies in syntactically correct and unambiguous sentences, like #The cat that fled from the mice.... If participants would use a plausibility strategy and combine the lexical items in the most plausible way, they would--in the case of the example--assume that the mice were fleeing from the cat. Furthermore, this interpretation could lead them to expect a particular inflection of the verb (here: plural inflection). The violation of this expectation could have elicited the P600 effect. Such a syntactic mismatch can occur only in sentences in which the number of theme and agent are different. Therefore, in the present study, the number of theme and agent was either different or the same. A centroparietal P600 effect was present not only in different number sentences but also in same number sentences. Consequently, the P600 effect was not due to a syntactic mismatch, thereby challenging a purely syntactic account of the P600. An alternative view concerning the functional significance of the P600 is discussed, i.e., that it reflects a monitoring component that checks upon the veridicality of ones sentence perception.