Proceedings of the Annual Meeting of the Cognitive Science Society

This short report summarizes a new model of question answering that we have developed and tested. The model specifies how humans answer many different kinds of questions (including why, how, when, where, enablement, consequence, and significane questions) after comprehending narrative passages. For example, if a narrative passage contained the episode the dragon kidnapped the maidens, te why-question for this episode would be why did the dragon kidnap the maidens? and possible answers would be because the dragon wanted to eat the maidens and because the dragon was lonely. According to the model, the major information sources for answers to questions include the passage structure and the generic knowledge structures that are associated with the content words in the query (i.e., DRAGON, MAIDEN, KIDNAPPING). After these knowledge structures are activated in working memory, there are convergence mechanisms which narrow down the node space to a set of relevant answers to a given question. The convergence mechanisms involve four major components. First, there is an arc search procedure, associated with each question category, which specifies what categories and paths of arcs are sampled when knowledge structures are tapped for answers. Second, there are a set of heuristics for establishing priorities among knowledge structures. heuristics for establishing priorities among knowledge structures. Third, there is an intersecting node identifier which segregates those nodes in a given knowledge structure which overlap (match) a node in at least one other knowledge structure in working memory. Fourth there is a constraint proagation component which prunes out erroneous nodes during the evaluation of (a) the intersecting nodes and (b) the nodes that radiate from intersecting nodes. The model has been tested by simulating question answering protocols collected from human subjects.