The Role of Color in Search Templates for Real-world Target Objects

During visual search, target representations (attentional templates) control the allocation of attention to template-matching objects. The activation of new attentional templates can be prompted by verbal or pictorial target specifications. We measured the N2pc component of the event-related potential (ERP) as a temporal marker of attentional target selection to determine the role of color signals in search templates for real-world search target objects that are set up in response to word or picture cues. On each trial run, a word cue (e.g., “apple”) was followed by three search displays that contained the cued target object among three distractors. The selection of the first target was based on the word cue only, while selection of the two subsequent targets could be controlled by templates set up after the first visual presentation of the target (picture cue). In different trial runs, search displays either contained objects in their natural colors or monochromatic objects. These two display types were presented in different blocks (Experiment 1) or in random order within each block (Experiment 2). RTs were faster and target N2pc components emerged earlier for the 2nd and 3rd display of each trial run relative to the 1st display, demonstrating that pictures are more effective than word cues in guiding search. N2pc components were triggered more rapidly for targets in the 2nd and 3rd display in trial runs with colored displays. This demonstrates that when visual target attributes are fully specified by picture cues, the additional presence of color signals in target templates facilitates the speed with which attention is allocated to template-matching objects. No such selection benefits for colored targets were found when search templates were set up in response to word cues. Experiment 2 showed that color templates activated by word cues can even impair the attentional selection of non-colored targets. Results provide new insights into the status of color during the guidance of visual search for real-world target objects. Color is a powerful guiding feature when the precise visual properties of these objects are known, but seems to be less important when search targets are specified by word cues.