| There has been a considerable amount of research investigating the effects of semantics on the speed and accuracy with which words presented in isolation are recognized. The present thesis contributes to this research by investigating interactions between a novel semantic variable, namely semantic distance (e.g., K. Lund & C. Burgess, 1996), and strategic control of lexical processing. Semantic distance is defined as the mean distance between a word and its ten nearest neighbors in high-dimensional space (L. Buchanan, C. Westbury, & C. Burgess, 2001). Words that have relatively close semantic neighbors are called low semantic distance words, whereas words that have relatively distant semantic neighbors are called high semantic distance words. Interactions were investigated in the lexical decision, semantic categorization, lexical decision/semantic categorization, and word naming tasks. In each task, semantic distance exerted a facilitatory effect (i.e., low semantic distance words were responded to more rapidly than high semantic distance words) when task demands required relatively extensive lexical processing. In task conditions that required relatively less extensive lexical processing, there was no effect of semantic distance. A cross-module activation account of semantic effects in lexical processing is described and the present findings are explained within this framework. It appears that semantic distance exerts at least two types of influence on the lexical processing system. The first type of influence arises from semantic neighbors influencing the settling times of orthographic and phonological codes (codes located outside the semantic module). The second type of influence arises from semantic neighbors influencing the settling times of semantic codes (codes located inside the semantic module). |
