The everyday apparent ease of language comprehension conceals the
considerable complexity of the processes that are necessary to its
success. In particular, this work examines evidence for the
controver-sial idea that the comprehension system considers multiple
inter-pretations of the evolving sentence in parallel. This idea,
already well established for lexical items, is controversial for
syntactic structures. In two experiments, evidence is presented in
support of the idea that the comprehension system activates multiple
possibilities for how the sen-tence will continue. Using event-related
potentials (ERPs), an N400 was obtained at "shot" in the sentence "The
claim that the cop shot the informant might have affected the jury" even
though the sentence continues in a plausible way. The N400, therefore,
indicates that the comprehension system was likely considering the
sentence "The claim that the cop shot*" as well. Using this type of
evidence, this work argues for the existence of parallelism in the
comprehension system and provides an overview of current theories in the
comprehension literature.