Current studies on visuomotor decision making come to inconsistent conclusions regarding the optimality with which these decisions are made. When executing rapid reaching movements under uncertainty, humans tend to automatically select optimal movement paths that take into account the position of all potential targets (spatial averaging). In contrast, humans rarely employ optimal strategies when making decisions on whether to pursue two action goals simultaneously or prioritise one goal over another. Here, we manipulated whether spatial averaging or pre-selection of a single target would provide the optimal strategy by varying the spatial separation between two potential movement targets as well as the time available for movement execution. In Experiment 1, we aimed to determine the time needed to reach for targets with small and large separation between them and to measure baseline strategies under low time pressure. Given generous time limits, participants did not employ a pure averaging approach but instead tended to pre-select the target that was easiest to reach and corrected their movement path in-flight if required. In Experiment 2, a strict time limit was set such that the optimal strategy to reach the correct target depended on the separation between the potential targets: for small separations, there was enough time to employ averaging strategies, but higher success for larger separations required pre-selecting the final target instead. While participants varied in the strategies they preferred, none of them flexibly adjusted their movement strategies depending on the spatial separation of the targets. In Experiment 3, we confirm the bias toward targets that are easiest to reach and show that this comes at the expense of overall task success. The results suggest a strong tendency for humans to minimize immediate movement effort and a general failure to adapt movement strategies flexibly with changes in the task parameters.

当前关于视觉运动决策的研究得出关于这些决策的最优性的结论不一致。当在不确定性下执行快速到达运动时，人类倾向于自动选择最佳运动路径，该路径应考虑所有潜在目标的位置（空间平均）。相比之下，人类在决定是同时追求两个行动目标还是将一个目标优先于另一个目标时，很少采用最佳策略。在这里，我们通过改变两个潜在运动目标之间的空间间隔以及可用于运动执行的时间来控制单个目标的空间平均或预选是否会提供最佳策略。在实验1中，我们的目标是确定达到目标之间的间隔很小和很大的时间，并在低时间压力下测量基线策略。给定足够的时间限制，参与者没有采用纯粹的平均方法，而是倾向于预先选择最容易达到的目标，并在需要时在飞行中纠正他们的运动路径。在实验2中，设置了严格的时间限制，以使达到正确目标的最佳策略取决于潜在目标之间的间隔：对于较小的间隔，有足够的时间采用平均策略，但是对于较大的间隔，成功需要较高的成功率， -选择最终目标。尽管参与者在他们选择的策略上有所不同，他们都没有根据目标的空间间隔灵活地调整其运动策略。在实验3中，我们确认了对最容易达到的目标的偏见，并表明这是以牺牲整体任务成功为代价的。结果表明，人类有强烈的趋势将即时运动的努力减至最少，并且普遍无法根据任务参数的变化灵活地调整运动策略。