Effect of stimulus degradation on category search

Two experiments studied the category effect in a visual search task. Experimental variables were Category Relationship (between vs within-category search) and Noise Condition (visual noise vs control). They were factorially combined in both experiments. Results indicated that the two factors had additive effects on search speed, but interacted with respect to errors and detection distances. The findings are discussed in the framework of a two-process model of search control. The model assumes that two operations are performed simultaneously during search: Controlled Search (CS) and Automatic Detection (AD). Both operations are affected by the category relationship between targets and nontargets, but the locus of the effect is different for CS and AD.