UC Santa Cruz

Language comprehension requires a complex series of decisions under uncertainty. This is especially obvious when one string may have multiple different interpretations, whether due to lexical ambiguity, or the potential for an inference beyond literal content. This dissertation profiles how the human system for language comprehension times those decisions, specifically when and why it sometimes postpones them. Evidence comes from nine reading experiments in English probing variation across a range of different types of uncertain meaning (homonymy and polysemy, predicate distributivity, scalar implicatures from "some", and causal inferences from discourse coherence) and across two tasks (self-paced-reading and the Maze task of Forster et al., 2009). Diagnosing the presence of decisions by testing for garden-path effects and costs associated with selection against a bias, I highlight two key patterns. First, some decisions, e.g. sense specification for polysemous nouns, are delayed in normal reading, but occur immediately when a rapid decision would be more useful; I conclude that decisions to postpone are flexible and sensitive to a comprehender's goals. Second, possible scalar implicatures and causal inferences rapidly affect comprehension, but do not receive any typical, decisive commitment until much later; I conclude that comprehenders may develop expectations gradiently based on multiple possible interpretations before they make a firm decision. Throughout the dissertation, I explore how these and related facts might be explained as a consequence of the ways humans attempt to rationally allocate cognitive resources under uncertainty.