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Kaori Yanase, Jun Kawahara, Michiteru Kitazaki; Stimulus-driven attentional capture by task-irrelevant optic flow. Journal of Vision 2012;12(9):1350. doi: 10.1167/12.9.1350.
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Researchers have debated about whether the deployment of visual attention is dependent on stimulus saliency or on attentional set. Studies supporting the latter view have used static features and have found that attention is captured only when task-irrelevant stimuli (distractors) share features with the target. Although several recent studies have included dynamic attributes, investigations have been limited to transient changes or the translation of local independent objects. Given that the visual system is sensitive to global signals such as optic flow, which is vital for locomotion, it is conceivable that global motion would be able to capture attention irrespective of attentional set. Thus, we investigated whether task-irrelevant optic flow captured attention when participants searched for a target defined by a specific color. The stimulus display consisted of 2,000 dots and a rapid stream of letters in the center. Observers searched for a green letter embedded in heterogeneously colored letters. The dots expanded or contracted for 100 ms at 300 ms or at 100 ms before or after 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 optic flow expanded 300 ms before target onset. A subsequent experiment revealed that an abrupt cessation, rather than an abrupt onset, of optic flow also impaired target identification when it occurred 300 ms before target onset. However, neither acceleration nor deceleration in the range of half to double the speed caused any significant decrement in target identification. We conclude that salient discontinuities in global motion induce attentional capture when observers engage in feature-search mode in a different stimulus domain.
Meeting abstract presented at VSS 2012
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