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Michiteru Kitazaki, Yuta Murofushi, Jun Kawahara; Task-irrelevant attentional capture by salient expanding motion. Journal of Vision 2014;14(10):314. doi: 10.1167/14.10.314.
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© ARVO (1962-2015); The Authors (2016-present)
Salient discontinuities in expanding optic flow induce attentional capture even when observers engage in feature-search mode in a different stimulus domain (Kawahara, Yanase, & Kitazaki, Journal of Vision 2012). We aimed to investigate whether global motion like as coherent optic flow is necessary or mere presence of a salient motion is sufficient for attentional capture to occur. In Experiment 1, the stimulus display consisted of 2,052 dots and a rapid stream of nontarget letters in the center. Observers searched for a green letter embedded in heterogeneously colored nontarget letters. The dots were divided into four square-regions (2x2 matrix, 18x18-deg each), so that the letter stream appeared in the intersection of the region borders. The bunch of dots expanded or contracted in each region for 100 ms at 300 ms before the presentation of a target. A control condition, under which the dots remained static, was also included. The results indicated that correct identification of the target was significantly impaired when the motions of four regions were contractions, suggesting that the expanding motion perceived locally around the central letter stream captures attention. In Experiment 2, the stimuli were identical to Experiment1 except that the dots in 6-deg diameter around the letters were deleted. We found that the accuracy for letter identification was impaired by four regions of expanding dots. This result suggests that local expanding motions capture attention. In Experiment 3, we presented a second-order motion of expanding or contracting circular contour by accretion and deletion of stationary dots (2,000 dots, contour diameter: min 6.9 to max 18.3-deg), and found the expanding second-order motion impaired letter-identification accuracy. This result suggests that the second-order motion can capture attention if the motion is expansion and sufficiently salient. We conclude that saliency of expanding motions is critical for the task-irrelevant attentional capture to occur.
Meeting abstract presented at VSS 2014
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