Indexical understanding of instructions

Background knowledge is essential for understanding. Our question concerns the nature of that knowledge: Is background knowledge solely descriptive and abstract, that is, consisting of propositions, schemas, and rules, or is there room for experiential and perceptual components? The indexical hypothesis suggests that experiential components are crucial for language comprehension. On this hypothesis, indexing, that is, referring words and phrases to objects (or analogical representations of objects), is required for comprehension. Once a phrase is indexed to an object, then affordances derived from the object are used to guide the interpretation of the language. We demonstrate support for the indexical hypothesis by manipulating the opportunity to index words to objects while acquiring background information about how to use a compass and map to identify landmarks. The participants acquired similar levels of abstract knowledge as assessed by a verbal test. Nonetheless, participants given the opportunity to index, compared to those prevented from indexing, read and followed new directions faster, referred to the background information less frequently, and performed the task using the compass and map more accurately. Discussion focuses on how these data are consistent with the indexical hypothesis and how that hypothesis pertains to comprehension of narratives.