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Patrick Cavanagh, Stuart Anstis; The Flash Grab Effect. Journal of Vision 2012;12(9):778. doi: 10.1167/12.9.778.
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© ARVO (1962-2015); The Authors (2016-present)
When an object moves back and forth, its trajectory appears significantly shorter than it actually is. The object appears to stop and reverse well before its actual reversal point, as if there is some averaging of location within a window of about 100 ms (Sinico et al, JEP:HPP 2009). Surprisingly, if a bar is flashed at the physical end point of the trajectory, right on top of the object just as it reverses direction, the flash is also shifted – grabbed by the object – and is seen at the perceived endpoint of the trajectory rather than the physical endpoint (Anstis & Cavanagh, VSS 2010). This shifts the perceived location of the flash by several times its physical size and by up to several degrees of visual angle. We measure the shifts in the perceived flash location and show that there is a small spatiotemporal attraction zone around the physical end point of the trajectory. Any flash falling in that zone is pulled toward the perceived endpoint. The effect scales linearly with speed and is independent of the contrast of the moving stimulus once it is above 5%.
Meeting abstract presented at VSS 2012
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