Burrell Mark, Pastor-Bernier Alexandre, Schultz Wolfram
Department of Physiology, Development and Neuroscience, University of Cambridge, Cambridge CB2 3DY, United Kingdom.
bioRxiv. 2023 Jan 10:2023.01.10.523384. doi: 10.1101/2023.01.10.523384.
All life must solve how to allocate limited energy resources to maximise benefits from scarce opportunities. Economic theory posits decision makers optimise choice by maximising the subjective benefit (utility) of reward minus the subjective cost (disutility) of the required effort. While successful in many settings, this model does not fully account for how experience can alter reward-effort trade-offs. Here we test how well the subtractive model of effort disutility explains the behavior of two non-human primates ( ) in a binary choice task in which reward quantity and physical effort to obtain were varied.Applying random utility modelling to independently estimate reward utility and effort disutility, we show the subtractive effort model better explains out-of-sample choice behavior when compared to parabolic and exponential effort discounting. Furthermore, we demonstrate that effort disutility is dependent on previous experience of effort: in analogy to work from behavioral labour economics, we develop a model of reference-dependent effort disutility to explain the increased willingness to expend effort following previous experience of effortful options in a session. The result of this analysis suggests that monkeys discount reward by an effort cost that is measured relative to an expected effort learned from previous trials. When this subjective cost of effort, a function of context and experience, is accounted for, trial-by-trial choice behavior can be explained by the subtractive cost model of effort.Therefore, in searching for net utility signals that may underpin effort-based decision-making in the brain, careful measurement of subjective effort costs is an essential first step.
All decision-makers need to consider how much effort they need to expend when evaluating potential options. Economic theories suggest that the optimal way to choose is by cost-benefit analysis of reward against effort. To be able to do this efficiently over many decision contexts, this needs to be done flexibly, with appropriate adaptation to context and experience. Therefore, in aiming to understand how this might be achieved in the brain, it is important to first carefully measure the subjective cost of effort. Here we show monkeys make reward-effort cost-benefit decisions, subtracting the subjective cost of effort from the subjective value of rewards. Moreover, the subjective cost of effort is dependent on the monkeys’ experience of effort in previous trials.
所有生物都必须解决如何分配有限的能量资源，以从稀缺机会中获取最大利益。经济理论假定，决策者通过最大化奖励的主观利益（效用）减去所需努力的主观成本（负效用）来优化选择。虽然该模型在许多情况下都很成功，但它并未完全解释经验如何改变奖励与努力之间的权衡。在此，我们测试努力负效用的减法模型在二元选择任务中对两种非人类灵长类动物行为的解释程度，该任务中奖励数量和获取奖励所需的体力努力是变化的。通过应用随机效用模型独立估计奖励效用和努力负效用，我们发现与抛物线型和指数型努力折扣相比，减法努力模型能更好地解释样本外的选择行为。此外，我们证明努力负效用取决于之前的努力经验：类似于行为劳动经济学的研究，我们开发了一个参考依赖型努力负效用模型，以解释在一个实验环节中，经历过费力选项后增加的付出努力的意愿。该分析结果表明，猴子会根据相对于从之前试验中学到的预期努力来衡量的努力成本对奖励进行折扣。当考虑到这种努力的主观成本（它是情境和经验的函数）时，逐次试验的选择行为可以用努力的减法成本模型来解释。因此，在寻找可能支撑大脑中基于努力的决策的净效用信号时，仔细测量主观努力成本是至关重要的第一步。
所有决策者在评估潜在选项时都需要考虑他们需要付出多少努力。经济理论表明，最优的选择方式是对奖励与努力进行成本效益分析。为了能够在许多决策情境中高效地做到这一点，需要灵活地进行，并根据情境和经验进行适当调整。因此，在旨在理解大脑中如何实现这一点时，首先仔细测量努力的主观成本很重要。在此我们表明，猴子会做出奖励与努力的成本效益决策，从奖励的主观价值中减去努力的主观成本。此外，努力的主观成本取决于猴子之前试验中的努力经验。
