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Hoko Nakada, Ikuya Murakami; Search inefficiency in a directionally consistent target among directionally switching distractors. Journal of Vision 2018;18(10):346. doi: 10.1167/18.10.346.
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Visual search is efficient when observers search for a moving target among static distractors and that search efficiency is equally high for a static target among moving distractors. However, visual motion often compromises search efficiency, as when all search items are moving, making search based on other features rather inefficient. Based on these effects of the presence of motion signals on visual search, we asked whether more complex motion signals such as directional reversal could affect search efficiency. To address this question, we used moving gabor patches as search items and reversed their motion directions over time during a visual search task. In one condition, the target was a gabor patch that periodically switched its motion direction whereas the remaining items, the distractors, maintained their motion directions. In another condition, the target maintained its motion direction whereas the distractors periodically switched their directions altogether. If the presence of visual motion per se disturbed search, both tasks should cause inefficient search. If, on the other hand, motion direction switching generally facilitated search, both tasks should cause efficient search. Furthermore, if the direction switching served as a salient feature, search asymmetry should emerge because a more salient item among less salient distractors would be easier to find than vice versa. Our results indeed demonstrated search asymmetry. Search was efficient for the directionally changing target among the consistently moving distractors, but was inefficient when the target consistently moved while the distractors changed their directions. This search asymmetry supported the hypothesis that motion direction switching is a salient feature in a visual search task for moving stimuli. Through a series of experiments, we clarified the determinant factor in motion direction switching that caused the search asymmetry, testing for possible factors such as orientation, acceleration, and synchrony.
Meeting abstract presented at VSS 2018
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