HOW DOES FEATURE-BASED ATTENTION AFFECT VISUAL PROCESSING

Five experiments are reported from which it is concluded that attendin g on the basis of a stimulus feature (e.g., red) does not directly aff ect the sensory quality of stimuli that possess that feature. Feature- based attention was manipulated in a visual search task by providing i nformation about the probability that the target would possess a given feature (e.g., ''The target has a 1.0 probability of being red when p resent.''). Feature-based attention failed to aid performance under '' data-limited'' conditions (i.e., those under which performance was pri marily affected by the quality of the stimulus) but did affect perform ance under conditions that were not data limited (Experiments 1-3). If attending to a feature had affected the sensory quality of stimuli, p erformance should have been aided under all conditions. Experiments 4 and 5 provided converging support for this conclusion.