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Frank Zaal, Rémy Casanova, Simon Ledouit, Reinoud Bootsma; Fractional-Order Information for Interception. Journal of Vision 2017;17(10):1164. doi: 10.1167/17.10.1164.
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Seeking or avoiding contact with stationary and moving targets is at the heart of many day-to-day behavior in humans and other animals. A close inspection of the visual control of such behavior shows that different strategies seem to be used in different situations. For instance, when considering a lateral-interception task, in which soccer goalkeepers have to stop balls shot at their goal, and in which these balls either have a sideways curve or not, the goalkeepers seem to rely on different informational variables in both conditions. This difference could be captured by the (integer) order of the informational variable: zeroth-order information would mean a pursuit strategy and first-order information would mean an interception strategy. The present contribution proposes that both situations can be understood to originate from the use of the same, fractional-order (i.e., non-integer), informational variable, the order of which relies on the specifics of the target movement. That is to say, rather than nulling the bearing angle (zeroth order) or its speed (first order), a fractional derivative of this optical angle is being nulled by the goalkeeper. Moreover, the specific fractional order is arrived at depending on the situation: every situations asks for its own order of control. We have elaborated a first proof of concept, based on experimental data in which goalkeepers, in virtual reality, were to catch balls arriving at the goal line. The order of control was close to 1.0 and 1.8 for the trajectories without and with sidespin, respectively. In addition, the model was also able to account for the systematic patterns in movement initiation times. The current work holds great promise for arriving at a unified account of interception and avoidance.
Meeting abstract presented at VSS 2017
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