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James R Tresilian; A simple empirical law for a class of visually timed interceptive actions. Journal of Vision 2003;3(9):380. doi: 10.1167/3.9.380.
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People are highly skilled at intercepting moving objects and capable of remarkably precise timing—in the order of a few milliseconds. The timing of interceptions is constrained by two situational factors: the time available to plan and complete the action and the temporal precision required by the task. Recent research on interceptive actions indicates that a highly replicable relationship is likely to exist between movement timing and task constraints. This is analogous to the classic Fitts' law relationship that relates movement time (MT) to task variables for movements aimed at stationary targets. We report two experiments that allowed a description of the relationship for an anticipatory interception task (without target pursuit). Two quantities that determine the required temporal precision were varied in experiment 1—target speed and size. Available time (viewing time, VT) was kept constant and relatively large (1.6 s). MT was found to decrease with increases in target speed and decreases in target size. These results conformed to a specific empirical relationship between MT and the task variables. In experiment 2, VT and target speed were varied. MT was found to decrease monotonically with decreases in VT and the effect of target speed declined, becoming undetectable at the shortest VT (0.4s). These results can be interpreted as providing direct information about the ‘rule’ used by the nervous system to pre-determine MT in anticipatory interceptions.
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