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Jiayi Chen, Melisa Menceloglu, Marcia Grabowecky, Satoru Suzuki; Motion estimation behind an occluder: dependence on speed and direction. Journal of Vision 2020;20(11):1581. doi: https://doi.org/10.1167/jov.20.11.1581.
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© ARVO (1962-2015); The Authors (2016-present)
Estimating moving objects’ spatiotemporal trajectories behind an occluder is important for performing daily tasks. We investigated potential biases in extrapolating motion behind an occluder. On each trial, a bar appeared at the edge of the screen and moved across the screen with constant speed, going behind an occluder for the latter half of the movement. Participants (N=24) were asked to press a key when they thought the occluded bar had reached the end of the occluder. We manipulated motion direction (rightward, leftward, downward, and upward) and speed (taking 500, 750, 1000, 1500, or 2000ms to move across the screen) across trials. Participants generally underestimated the bar’s speed as their responses were delayed relative to the actual time of the bar reaching the end of the occluder. The underestimation of the speed was minimal on trials following the initial practice trials with feedback (where the location of the bar was revealed at the time of the key press) and steadily grew over the 400 trials without feedback, indicating that the speed-underestimation bias is intrinsic. Interestingly, the amount of speed underestimation followed Weber’s law (~20% underestimation) up to the speed corresponding to moving across the screen in 1000ms; for slower speeds the proportion of underestimation decreased to ~14% for 1500ms and ~10% for 2000ms. Because Weber’s law held within the sub-second range (500, 750, and 1000ms), an intriguing possibility is that this underestimation may depend on the temporal duration during which motion is attended rather than speed. We will investigate this possibility by varying the size of the screen as the motion-attention-duration hypothesis predicts that the proportion of speed underestimation should depend only on temporal parameters. The amount of speed underestimation was also consistently larger in the upward direction than in other directions, potentially due to visual experience in gravity.
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