Towards a better understanding of prioritization of visual information during preview search

In visual search tasks, if a subset of the search items (without the target) is presented at least 400 ms before the full set is in view, visual search efficiency is improved as if only the second set of items had been searched. This phenomenon is known as visual marking, and is thought to reflect both inhibitory-tagging of old previewed items and prioritization of the new items due to their more recent (and distinct) onset. This study investigates the nature of this inhibitory-tagging in two perspectives. Part I investigates whether this inhibitory-tagging is location-based or feature-based. Subjects searched for a sideway T among Ls of identical color and regular Ts and upside-down Ts of a second color, and reported the orientation of the target T. In addition, to eliminate the contribution of bottom-up attentional capture by the onset of the second set of items, we included a 200ms blank display between the initial preview and the final search display. In five experiments, we demonstrated that the preview benefit relies preferentially on feature-based inhibitory tagging (Experiments 1-3), even when location-based information is available and can be used to improve search efficiency (Experiments 4 and 5). The results are discussed in the context of processing economies and provide strong evidence that the mechanisms underlying the preview benefit are very sensitive to the experimental context in which the preview search is investigated. Part II investigates whether this inhibitory-tagging can be semantically mediated. In four experiments, we demonstrated that previewing a color blob indicating either target color or distractor color (Experiment 6 and 7) can also produce a preview benefit, and previewing target color is equivalent to previewing half of the distractors. When the previewed color information is further abstracted to semantic level by showing a word cue which indicates either distractor color or target color (Experiment 8 and 9) , this preview benefit is even stronger. In fact, previewing target color information produces the same benefits in terms of RTs as previewing half of the distractors. This is not true for previewing distractor color information. In summary, the results suggest that in visual search, prioritizing visual information is flexible and higher search efficiency can be achieved from different sources.