| Recent experimental work has sought to determine whether there are two distinct categories of implicated meaning. Generalized implicatures arise largely independent of context, and particularized implicatures depend on the context in which they occur for their full interpretation to go through (Grice, 1975). Pragmatic models differ about whether there are independent mechanisms for each type of meaning. Some theories assume these two categories are generated by the same context-dependent mechanism (Carston, 2002; Sperber & Wilson, 1986). Other theories, in contrast, assume that generalized implicatures are default inferences that get computed automatically regardless of the context (Chierchia, 2004; Gazdar, 1979; Levinson, 2000).;The experiments reported in this dissertation were designed to test these competing predictions by examining the processing of contrastive pre-nominal modifiers. Sedivy, Tanenhaus, Chambers, & Carlson (1999) showed that upon hearing an instruction, such as Pick up the tall..., the probability of fixating a tall glass will begin to increase, even before the onset of the noun when the visual display contains a contrasting object (i.e. a short glass). This result shows that the comprehension system has certain expectations with regard to quantity of information. In this case, people rely on their knowledge that modifiers are often used to distinguish contrasting objects, and Sedivy et al.'s data indicate that people can rapidly integrate this linguistic knowledge with the available visual information to make an inference about what the target will be.;The results from the first two experiments showed that this inference can be modulated by the extent to which modifiers are used to distinguish contrasting objects over the course of the experiment. When participants were in an informative task environment with respect to modification, they showed early looks to the target. In contrast, subjects who heard a high number of uninformative modifiers failed to show anticipatory looks to the target. These results cast doubt on the default view, which assumes that the contrastive interpretation should be available immediately in all contexts.;In the third experiment, I tested another type of contextual manipulation. In most cases, an indefinite expression (e.g. a glass) is used to introduce an object into the discourse, and afterwards the entity will be referred to with a definite expression (e.g. the glass). In the third experiment, I introduced all of the objects linguistically on each trial with an indefinite expression to determine if this changes the pattern of results that was obtained in the previous two experiments. The key issue is whether visual co-presence provides the adequate conditions for the use of a definite description. If it does not, then adding a short linguistic introduction should facilitate processing when contrasting objects are present, and it should impair processing in the absence of a contrasting object. The results showed little change with the linguistic introduction, suggesting that visual co-presence is sufficient to support a definite referring expression. |
