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Huaiyong Zhao, William Warren; Intercepting a moving target in fog: On-line or model-based control?. Journal of Vision 2014;14(10):1350. doi: 10.1167/14.10.1350.
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© ARVO (1962-2015); The Authors (2016-present)
When walking to intercept a moving target, people appear to use a constant bearing strategy (Chardenon, et al., 2002, 2005; Lenoir, et al., 1999, 2002): interception behavior is closely modeled by nulling change in the bearing direction of the target, based on current visual information (Fajen & Warren 2004, 2007). Alternatively, interception might be controlled by an internal model of the target's motion, which is updated by current information (Diaz, et al., 2013). To investigate whether interception is under on-line or model-based control, participants intercepted a moving target that became visually blurred or totally occluded, as if in fog. Participants (N=10) walked in a virtual environment (12m x 12m), and displays were presented stereoscopically in a head mounted display (63˚H x 53˚V, 60 Hz), while head position was tracked (60 Hz). The target (7.8m distant) moved at 0.6, 0.8 or 1.0 m/s. 2.5s after it appeared, the target either remained fully visible or passed behind a translucent gray occluder, so it was blurred at one of 4 levels or completely occluded; 2.5-6.0s later the participant reached the occluder and their position was recorded. Blur levels were created by varying the target's width and contrast using a Gaussian filter, to induce position and speed uncertainty. As blur increased, participants increasingly lagged behind the target (p<0.01) and SD of this error increased (p<0.01), with total occlusion yielding the largest errors (CE=-1.0m, mean SD=0.4m, p<0.01). Thus, degrading target visibility progressively impairs interception accuracy and precision, and occlusion severely impairs performance. The results are consistent with dependence on current visual information, and imply that the fidelity of an internal model, if one exists, rapidly decays beyond the greatest blur level and is ineffective for guiding locomotion. These findings suggest that interception of a moving target is normally controlled on-line based on current visual information.
Meeting abstract presented at VSS 2014
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