How does feature-based attention affect visual processing

Five experiments are reported from which it is concluded that attending on the basis of a stimulus feature (e.g., red)does not directly affect he sensory quality of stimuli that possess that feature. Feature-based attention was manipulated in a visual search task by providing information about he probability that the target would possess a given feature (e.g., "The target has a 1.0 probability of being red when present."). Feature-based attention failed to aid performance under "data-limited " conditions (i.e., those under which performance was primarily affected by the quality of the stimulus) but did affect performance under conditions that were not data limited (Experiments 1-3). If attending to a feature had affected the sensory quality of stimuli, performance should have been aided under all conditions. Experiments 4 and 5 provided converging support for this conclusion. How does attending to a particular feature, such as red, affect visual processing? Suppose that you are to meet a friend at a crowded baseball game and that you know that he will be wearing a red sweatshirt. One possibility is that looking for the red sweatshirt makes the red things in th