Parsing as Incremental Restructuring

A prevalent trend in modeling human sentence processing has been to account for both initial attachment preferences and reanalysis behaviors with minimal extensions to a presumed set of initial parsing operations. Here, an entirely different formulation of the initial attachment and revision processes is suggested. Rather than assuming that all parsing is (as much as possible) initial attachment, the opposite approach is advocated: that all parsing—even initial attachment—is restructuring. The realization of parsing as restructuring arises from a set of independently motivated computational assumptions within the competitive attachment architecture, a hybrid connectionist model of the human sentence processor. Central to the model is a unique parallel attachment operation that simultaneously attaches the current input phrase, while reattaching previously structured phrases. Within this model, reanalysis is not a separate process or module, but rather a side effect of the primary means of forming syntactic structures. The ease of performing possible reanalyses is therefore determined by the same conditions, such as recency and lexical preferences, that affect initial attachments. Furthermore, independently motivated constraints on the network structure determine the allowable syntactic configurations that may undergo restructuring within the competitive attachment operation. The model thus also provides a computational explanation of gardenpath sentences, in which automatic reanalysis is impossible.