Setting up the target template in visual search.

Top-down knowledge about the target is essential in visual search. It biases visual attention to information that matches the target-defining criteria. Extensive research in the past has examined visual search when the target is defined by fixed criteria throughout the experiment, with few studies investigating how subjects set up the target. To address this issue, we conducted five experiments using random polygons and real-world objects, allowing the target criteria to change from trial to trial. On each trial, subjects first see a cue informing them about the target, followed 200-1000 ms later by the search array. We find that when the cue matches the target exactly, search speed increases and the slope of response time-set size function decreases. Deviations from the exact match in size or orientation slow down search speed, although they lead to faster speed compared with a neutral cue or a semantic cue. We conclude that the template set-up process uses detailed visual information, rather than schematic or semantic information, to find the target.