Whole-body movements are performed daily, and humans must constantly take into account the inherent instability of a standing posture. At times these movements may be performed in risky environments and when facing different costs of failure. The aim of the study was to test the hypothesis that in upright stance participants continuously estimate both probability of failure and cost of failure such that their postural responses will be based on these estimates. We designed a snowboard riding simulation experiment where participants were asked to control the position of a moving snowboard within a snow track in a risky environment. Cost functions were provided by modifying the penalty of riding in the area adjacent to the snow track. Uncertainty was modified by changing the gain of postural responses while participants were standing on a rocker board. We demonstrated that participants continually evaluated the environmental cost function and compensated for additional risk with feedback-based postural changes, even when probability of failure was negligible. Results showed also that the participants' estimates of the probability of failure accounted for their own inherent instability. Moreover, participants showed a tendency to overweight large probabilities of failure with more biomechanically constrained standing postures that results in suboptimal estimates of risky environments. Overall, our results suggest that participants tune their standing postural responses by empirically estimating the cost of failure and the uncertainty level in order to minimize the risk of falling when cost is high.

中文翻译：

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调整站立姿势对不稳定性和成本函数的反应。

每天都要进行全身运动，因此人类必须不断考虑站立姿势固有的不稳定性。有时，这些移动可能会在危险环境中以及面临不同的失败成本时执行。该研究的目的是检验以下假设：在直立姿态下，参与者不断估计失败的可能性和失败的成本，以使他们的姿势反应将基于这些估计。我们设计了一个单板滑雪模拟实验，要求参与者在有风险的环境中控制运动的单板在雪道内的位置。通过修改雪道附近区域的骑行惩罚来提供成本函数。当参与者站在跷板上时，通过改变姿势反应的获得程度来修改不确定性。我们证明，即使失败的可能性可以忽略不计，参与者仍继续评估环境成本函数并通过基于反馈的姿势变化来补偿其他风险。结果还表明，参与者对失败概率的估计说明了他们自身固有的不稳定性。此外，参与者表现出倾向于增加较大的失败概率，而更多的生物力学限制了站立姿势，这导致对危险环境的估计不足。总体，