Memory operations and structures in sentence comprehension: Evidence from Ellipsis

Abstract

Natural language often contains dependencies that span words, phrases, or even sentences. Thus, language comprehension relies on recovering recently processed information from memory for subsequent interpretation. This dissertation investigates the memory operations that subserve dependency resolution through the lens of verb-phrase ellipsis (IPE) and sluicing.

Chapter One discusses two operations: (1) accessing an antecedent in memory, and (2) integrating that representation into the local context. Three studies investigated whether the first operation involves search or direct-access retrieval by measuring the effect of increased distance between antecedent and VPE on comprehension speed and accuracy. Distance decreased accuracy, indicating the quality of retrieved information decreased as distance increased. However, contra a search, speed was unaffected. This pattern suggests the memory structures formed during comprehension are content-addressable and retrieved with a direct-access operation.

To address the second operation, three studies manipulated antecedent length and complexity. One kind of antecedent complexity lowered accuracy, notably, the number of discourse entities in the antecedent. However, the speed of interpretation was unaffected. This pattern is inconsistent with a strict copy operation, suggesting VPE interpretation may involve a pointer to extant structures in memory.

Chapter Two discusses the pointer hypothesis via a study designed to detect forward search strategies in VPE. By manipulating the location of interfering material—either before the onset of the antecedent (PI) or intervening between antecedent and ellipsis (RI), we tested for forward and backward search, where retrieval dynamics should slow as a function of distance. However, the interfering material's position only affected accuracy: RI engendered lower accuracy than PI. Crucially, location did not affect the speed of processing, which is inconsistent with both forward and backward search.

Chapter Three applies this approach to another type of elided dependency, sluicing. Sluicing differs from VPE in that its retrieval cues provide more constraint on the identity of its antecedent verb, and is not subject to syntactic isomorphism, lending itself to testing the effects position and order information on dependency resolution, which were not testable in VPE. Though antecedent position adversely affected accuracy, the timecourse profile remained consistent with a cue-dependent direct-access pointer whose performance is shaped by general memory variables.