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Jason Chuang, Xin Huang; The effects of dynamic background noise on speed perception. Journal of Vision 2012;12(9):747. doi: 10.1167/12.9.747.
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© ARVO (1962-2015); The Authors (2016-present)
In natural scenes, objects commonly move upon cluttered backgrounds. Visual contexts can significantly influence motion perception. Here we investigate how visual contexts influence speed perception. We asked whether background-stimuli that did not move in a specific direction could influence the perceived speed of a center-stimulus. Visual stimuli were two overlapping random-dot patches. The diameters of the "center" and "background" patches were 5° and 7°, respectively. The random dots in the center patch moved coherently in a fixed direction at one of four speeds (5, 10, 15, 20°/s). The velocity of the random dots in the background patch was 0 (i.e. no net motion), but the motion coherence was set at one of several levels ranging from 0% to 100%. Human subjects performed a temporal 2AFC task to compare the speed of the center patch with that of a comparison patch. The speed of the comparison patch was varied from trial to trial and a matching speed was determined via a staircase procedure. We found that the perceived speed of the center patch was significantly faster than its veridical speed when the background contained random motion noise. The perceived speed was tuned to the coherence level of the background dots. The coherence level at which the perceived speed was the fastest shifted from high (i.e. less noisy) to low (i.e. more noisy) when the speed of the center patch changed from low to high. In other words, the effects of the background-stimulus on the perceived speed of the center-stimulus depended on the spatial-temporal characteristics of the center and background motions. We also found that these effects did not rely on whether the center-stimulus could be segmented from the background. These results suggest that speed perception is related to the overall motion energy within a specific region.
Meeting abstract presented at VSS 2012
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