Event-Related Brain Potentials and Case Information in Syntactic Ambiguities

In an ERP study German sentences were investigated that contain a case-ambiguous NP that may be assigned accusative or dative case. Sentences were disambiguated by the verb in final position of the sentence. As our data show, sentences ending in a verb that assigns dative case to the ambiguous NP elicit a clear garden-path effect. The garden-path effect was indicated by a broad centro-posterior negative shift that occurred between 300 and 900 msec after the dative-assigning verb was presented. No enhanced P600 following the misanalysis was observed. Noun phrases whose case ambiguity was resolved in favor of accusative case and unambiguouslv dativemarked NPs did not trigger significant ERP differences. We will discuss the implications of our results for parsing and its neuropsychological correlates. The results of this study support a parser design according to which the so-called structurdl case (nominative or accusative) is assigned without any delay in the absence of morpho-lexical counterevidence. It is argued that the enhancement of a negative ERP component with a "classical" N400 topographv reflects the difficulty of reanalysis due to reaccessing morpho-lexical information that lies outside the domain of the parsing module. Consequently, ERP responses to garden-path effects are not confined to a late positivity but vary depending on the level of processing involved in reanalysis. The fact that garden-path effects may also elicit an N400 can be linked to the nonhomogeneous linguistic properties of the constructions from which they arise