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.

不同时间节点下的收益抉择是经济学、心理学与行为生态学等多大学术领域均得到广泛研究的经典议题。已有研究证实，人类与其他动物在进行这类跨期选择（intertemporal choices）时，会依据奖励的延迟时长对其价值实施双曲线贴现，即延迟折扣（delay discounting），因此常被判定为短视决策行为。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。迄今为止，学界仍未明确如何调和这两种分别以奖励贬值、奖励率最大化为核心的研究范式。本研究针对81名人类被试在跨期决策中的奖励贴现程度与奖励率最大化倾向展开了实验探究。实验结果表明，双曲线贴现模型与奖励率最大化模型均能较好地拟合多种跨期选择设计范式下的被试决策数据。值得注意的是，在所有实验条件中，奖励率最大化模型对决策数据的拟合效果均优于双曲线贴现模型。有趣的是，与既往研究结论相悖，奖励率最大化倾向在所有选择框架中均普遍存在，并非仅局限于觅食场景。此外，在所有实验条件下，奖励率最大化倾向与双曲线贴现程度均呈现显著相关。这一发现支持了如下假说：进化之所以青睐双曲线贴现行为，是因为该机制可通过灵活调整对“小而早”与“大而晚”奖励的偏好，从而助力实现奖励率的最大化。因此，奖励率最大化或许是一条普适性原则，从整体上塑造了包括人类在内的众多物种在各类跨期决策问题中的决策行为。