Abstract
Recent studies about attentional capture reported that the capture of attention by a singleton distractor increased when search efficiency decreased. Expanding these studies, we tested whether search efficiency manipulation has similar effect on stimulus-driven attentional capture across different types of search tasks. In our experiment, twenty undergraduates performed two different types of visual search tasks, including a single target and eight distractors. For one, participants searched for a right- or left-tilted line among vertical lines (orientation feature search). For the other, participants looked for an outlined square with a right- or left-gap among squares with a top- or bottom-gap (Landolt C search). For each search task, we had two different levels of search difficulty (easy vs. difficult); For the feature search task, the tilt of the target was either 4.5 (difficult) or 9 degree (easy). For the Landolt-C search, the size of gap was set to either 3 or 6 degree. A half of the total trials had a distinct color distractor and these trials are referred to as distractor-present trials. In the remaining trials, there was no singleton distractor (distractor-absent). As results, under feature search, attentional capture by the color singleton was found, p< .001. This capture significantly increased when the similarity between the target and distractor decreased, p< .05, replicating previous findings. Under the Landolt-C search, no attentional capture was found, p>.47. Importantly, both the easy and difficult Landolt-C search tasks yielded more robust set-size effect and longer RT than the easy feature search. These results indicate that search difficulty or efficiency cannot fully explain the capture of attention by a salient stimulus. The present findings suggest that the process of searching for the Landolt target involves qualitatively different process than the feature search, pointing to the role of search demand on attentional capture.
Meeting abstract presented at VSS 2018