Data from: Rate maximization and hyperbolic discounting in human experiential intertemporal decision making

Decisions between differently timed outcomes are a well-studied topic in as diverse academic disciplines as economics, psychology, and behavioral ecology. Humans and other animals have been shown to make these intertemporal choices by hyperbolically devaluing rewards as a function of their delays (‘delay discounting’), thus often deemed to behave myopically. In behavioral ecology, however, intertemporal choices are assumed to meet optimization principles, that is, the maximization of energy or reward rate. Thus far it is unclear how different approaches assuming these two currencies, reward devaluation and reward rate maximization, could be reconciled. Here we investigated the degree at which humans (N = 81) discount reward value and maximize reward rate when making intertemporal decisions. We found that both hyperbolic discounting and rate maximization well approximated the choices made in a range of different intertemporal choice design conditions. Notably, rate maximization rules provided even better fits to the choice data than hyperbolic discounting models in all conditions. Interestingly, in contrast to previous findings, rate maximization was universally observed in all choice frames, and not confined to foraging settings. Moreover, rate maximization correlated with the degree of hyperbolic discounting in all conditions. This finding is in line with the possibility that evolution has favored hyperbolic discounting because it subserves reward rate maximization by allowing for flexible adjustment of preference for smaller, sooner or larger, later rewards. Thus, rate maximization may be a universal principle that has shaped intertemporal decision making in general and across a wide range of choice problems.不同时间节点间的决策选择是经济学、心理学与行为生态学（behavioral ecology）等多大学术领域中被广泛研究的经典议题。既往研究表明，人类与其他动物在开展这类跨期选择（intertemporal choices）时，会依据奖励的延迟时长对其价值进行双曲线贬值，即所谓的‘延迟折扣（delay discounting）’，因此常被认为具有短视决策倾向。但在行为生态学领域，跨期选择被认为需遵循最优化原则，即最大化能量摄入或奖励率最大化（reward rate maximization）。截至目前，学界仍未明确如何调和基于奖励贬值与奖励率最大化这两种不同理论框架的研究路径。 本研究针对81名人类被试（N=81）在进行跨期决策时的奖励贬值程度与奖励率最大化倾向展开了探究。实验结果显示，双曲线折扣（hyperbolic discounting）模型与奖励率最大化模型均能较好地拟合多种不同实验设计条件下的选择行为。值得关注的是，在所有实验条件中，奖励率最大化规则对选择数据的拟合效果均优于双曲线折扣模型。 有趣的是，与既往研究结论相悖，本研究发现奖励率最大化倾向普遍存在于所有选择框架中，且并非仅局限于觅食场景（foraging settings）。此外，在所有实验条件下，奖励率最大化倾向与双曲线折扣程度均呈现显著相关。这一发现支持了如下假说：进化选择之所以青睐双曲线折扣机制，是因为该机制能够通过灵活调整对‘小而即时’与‘大而延时’奖励的偏好，从而实现奖励率最大化。由此可见，奖励率最大化或许是一条普适性原则，从根本上塑造了跨物种、覆盖各类决策场景的跨期决策行为。