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Geoffrey Bingham, Joe Anderson; Perceptual information for the control of walking-to-reach. Journal of Vision 2008;8(6):615. doi: 10.1167/8.6.615.
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Introduction: We examined perceptual information strategies for control of walking-to-reach. Previous research showed that people use a monocular tau-based strategy for the control of walking to a target (Wann et al., 1996). Recently, we have shown that people also use a relative disparity tau-dot information strategy to control targeted reaching (Anderson & Bingham, 2007). To walking to a stop with soft contact of the hand at a target, multiple timing layers must be integrated and controlled including head-to-target velocity, timing of reach initiation, and hand-to-target velocity. The problem is that binocular tau information is not good at the larger distances entailed by walking and monocular tau information cannot be used to control reaching (Bingham & Zaal, 2005). Therefore, we propose that walking-to-reach entails a transition from monocular tau information for the control of walking to binocular tau information for the control of reaching. We manipulated the presence of monocular or binocular information under conditions of monocular or binocular viewing and analyzed walking and reaching trajectories to evaluate what information strategies might be used to control walking, reach initiation, and targeted reach trajectory.
Method: Eight participants walked briskly to a point-light or a glowing orb target in the dark and brought their hand or nose to a stop at the target. Hand location was specified by a point-light placed on the thumb. Movements were recorded using an OptoTrak. Diodes were placed on the participant's forehead, chest, and hand. Separation of the latter diodes indicated reach initiation.
Results: Results showed that participants used a monocular tau-dot strategy (Tau-dot ≈ −.5) to control walking (confirming previous findings) and used a binocular tau-based strategy to control reaching (confirming previous findings in studies of reaching).
Conclusion: Participants use a monocular tau strategy for control of walking but switch to a disparity tau strategy for control of reaching.
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