Goal-directed guidance of attention: evidence from conjunctive visual search.

Conjunctive visual search is most difficult when distractor types are in equal proportions and gets easier as the proportions diverge (e.g., E. Zohary & S. Hochstein, 1989). This may reflect restriction of search to the feature shared by the target and the less-frequent distractor. Alternatively, such effects could reflect target salience, which varies with distractor ratio. In 2 experiments, 60 participants searched 64-element displays for a conjunctive target among distractors of 2 types in various proportions. Participants were correctly informed (Experiment 1) or misinformed (Experiment 2) about which distractor type would be less frequent on most trials. In both experiments, the distractor-ratio effect was significantly influenced by the information provided to participants. These findings demonstrate the efficacy of top-down information in guiding attention and show that it can be applied flexibly, weighted toward particular target features.