Parsing Coordinates and Ellipsis: Copy α

In this paper we argue that the human parsing mechanism has available two distinct methods of building syntactic structure. One mechanism, which has been studied extensively, involves building structure in response to the input in a step-by-step, inference-by-inference manner. Building more structure by this means involves more processing cost than building less structure. The second mechanism, proposed here, involves essentially cost-free copying of the structure of an antecedent clause. Building more structure by this means (copying) does not necessarily impose a greater cost than building (copying) less structure. The results of several sentence processing studies are presented in support of the proposal.