Abstract
Cueing attention to a particular location is space leads to enhanced processing of objects in that circumscribed area. However, attention can also be cued to non-spatial properties of objects (e.g. colour) resulting in preferential processing of that feature throughout the visual field. We have previously shown that this principle of feature-based attention contributes to higher-level processing, such as during the perception of objects. When attending to contour defined loops, perception of similar object contours is better relative to the perception of other incongruent features. In the current experiment we investigated the influence of feature cues. Participants viewed a rapid serial visual presentation of random arrays of gabors that sometimes formed a loop that was either contour- or motion-defined and that should be detected as quickly as possible. To cue feature-based attention, in separate blocks of trials there was an 80% chance that the target was a contour or motion, respectively. We found valid cues to contour-defined loops produced faster reaction times compared to invalid cues. This demonstrates the impact of a feature cue in perceiving object contours. To investigate the neural mechanism responsible for this feature cue effect, we recorded ERP's while performing this task. We observed cue-related positivity at about 300ms after stimulus onset. Our data argue for a contribution of later, possibly top-down mechanisms to feature-based attention, perhaps reflecting an attentional set for feature dimensions.