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Cristina de la Malla, Joan López-Moliner; Coupling of reaction and movement times in reaching. Journal of Vision 2014;14(10):416. doi: 10.1167/14.10.416.
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© ARVO (1962-2015); The Authors (2016-present)
Two main components are considered in reaching movements towards a target: the reaction time (RT, the time between target onset and movement initiation) and the movement time (MT, from movement onset to movement offset). RT is often used as a signature of action planning. We are interested in how both components are coupled and whether they can be controlled independently of each other. We designed a task in which subjects saw a red target that turned green to signal the response period after 0, 0.25, 0.50, 1, 2 or 5 seconds contributing to different degrees of movement planning. After the color change, subjects had to reach the target in 800 ms. In different conditions this time could refer to the duration of the whole movement including RT (RT+MT) or only to the duration of the MT. Results show that the longer the time to plan the movement, the shorter the RT but also (and unavoidably) the longer the MT. Although this coupling could be useful for the RT+MT condition because they compensate one another, it generates systematic temporal errors when the MT has to be controlled independently. The same coupling is found in a task in which subjects are required to make a ballistic movement towards the target. In this task there were not temporal restrictions, but yet MT kept increasing with planning time, resulting in the reported RT-MT coupling. The increase of the MT involved smoother movements, therefore, this automatic coupling could reflect some basic optimization principle when performing the movements that can eventually override the goal of the task (e.g.: perform a movement within some temporal boundaries).
Meeting abstract presented at VSS 2014
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