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Ryohei Nakayama, Isamu Motoyoshi, Takao Sato; Motion pop-out is determined by extra-retinal coordinate. Journal of Vision 2013;13(9):964. doi: 10.1167/13.9.964.
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© ARVO (1962-2015); The Authors (2016-present)
It is well known that moving targets pop out against stationary distractors in visual search displays. However, motion can be defined relative to the body (spatiotopic), or to the other stimuli (object-based) as well as in retinal coordinate, but the relative contribution of these different coordinate systems in visual search is not known yet. To clarify this point, we evaluated pop-out in a display where the target- and distractor- motions were defined by different coordinates. The stimulus consisted of 4 or 8 gratings patches (H1.3xV8.7 deg) placed on a gray background (H13xV8.7 deg) with a fixation point at the center. The gratings had randomly assigned orientation (45 or 135 deg). They were either stationary or moved. When they moved, they moved either upward or downward all together within the envelope.z88;Motions defined by different coordinates were created by manipulating combination of stationarity and motion of gratings, background and fixation. For example, if fixation is moved together with the grating motion when the target is moving and distractors are stationary on the screen, the target becomes stationary and distractors become drifting on the retina. Using this logic, we examined the contribution of each coordinate system on pop-out phenomenon. Reaction times were measured for detecting a moving target among stationary distractor or a stationary target among moving distractors. It was found that the target pops out regardless of defining coordinates. In addition, there was an intriguing asymmetry. A target drifting in spatiotopic and object-based coordinate among retinotopically drifting distractors was detected faster than a target in the opposite combination, indicating advantages of spatiotopic and object-based motions in visual search. These results are consistent with our previous findings on the perceptual dominance in binocular rivalry (Nakayama et al., VSS 2012), and suggest that saliency of visual motion predominantly depends on extra-retinal information.
Meeting abstract presented at VSS 2013
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