Top-down effects of semantic knowledge in visual search are modulated by cognitive but not perceptual load.

Moores, Laiti, and Chelazzi (2003) found semantic interference from associate competitors during visual object search, demonstrating the existence of top-down semantic influences on the deployment of attention to objects. We examined whether effects of semantically related competitors (same-category members or associates) interacted with the effects of perceptual or cognitive load. We failed to find any interaction between competitor effects and perceptual load. However, the competitor effects increased significantly when participants were asked to retain one or five digits in memory throughout the search task. Analyses of eye movements and viewing times showed that a cognitive load did not affect the initial allocation of attention but rather the time it took participants to accept or reject an object as the target. We discuss the implications of our findings for theories of conceptual short-term memory and visual attention.