Research on language comprehension has focused on the resolution of syntactic ambiguities, and most studies have employed garden-path sentences to determine the system's preferences and to assess its use of nonsyntactic sources information. A topic that has been neglected is how syntactically challenging but essentially unambiguous sentences are processed, including passives and object-clefts--sentences that require thematic roles to be assigned in an atypical order. The three experiments described here tested the idea that sentences are processed both algorithmically and heuristically.