When verbs have bugs: lexical and syntactic processing costs of split particle verbs in sentence comprehension

German particle verbs consist of a base and a particle, two constituents which occupy separate positions in main clauses, but share one lexical entry. It is still unclear if the combination of particles and bases during sentence comprehension is lexical, syntactic or dual in nature. Using behavioural and ERP measurements, we investigated lexical access and sentence integration of split particle verbs in German two-argument sentences. Our results show that the integration of split particle verbs violating sentence structure or lexical constraints leads to both lexical and syntactic processing difficulty. This extends earlier comparable findings reporting only lexical access difficulties, and suggests that the parse is not immediately abandoned upon encountering a nonexistent particle verb. The integration of grammatical particle verbs assigning lexical case did not lead to measurable processing difficulties. We discuss the impact of this finding for current accounts of the role of lexical case marking in sentence comprehension.