Is there an uncertainty principle in interceptive timing? J López-Moliner |
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Institute for Brain, Cognition and Behaviour, University of Barcelona, Spain
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| In physics the uncertainty principle asserts a limit to the precision with which position and momentum can be known simultaneously. Intercepting moving objects at given positions within a temporal window also requires precision in predicting future positions (to avoid sensorimotor delays) and knowing the temporal error that we can afford based on target velocity. In two tasks subjects had to synchronise a key press with moving Gabors (0.9 c/deg) crossing a designated position at different speeds or intercept the Gabors by controlling a cursor. To test the reliance on perceived position I induced position shifts (forward/backwards) by adding local drift (same/opposite) to the global displacement. The perceived position accounted for the initiation of the interception but not its end point. This was consistent with subjects monitoring the position to start the action but relying on velocity to perform the motor movement. Interestingly, when subjects only had a single moment (synchronisation task) the responses reflected a compromise between position and velocity. This trade-off resulted in a U-shape of the combined (position and temporal) variability that was only present in the synchronisation task. Single time responses reflect then an uncertainty principle when minimising temporal and position errors. |
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