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.不同时间维度收益间的决策，是经济学、心理学与行为生态学等多元学术领域中被广泛研究的课题。已有研究证实，人类与其他动物在开展这类跨期选择（intertemporal choices）时，会依据收益的延迟时长以双曲线方式对其价值进行贴现，该过程即延迟折扣（delay discounting），因此常被判定为呈现短视决策特征。不过在行为生态学研究范畴中，跨期选择被认为需契合最优化原则，即实现能量或奖励率最大化（reward rate maximization）。截至目前，学界尚未明确如何调和“价值贴现”与“奖励率最大化”这两种不同分析范式。本研究针对人类被试（N=81）在跨期决策中的奖励价值贴现程度与奖励率最大化倾向展开了实验探究。结果显示，双曲线贴现（hyperbolic discounting）模型与奖励率最大化模型均能较好拟合多种不同跨期选择设计范式下的被试决策行为；尤为关键的是，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。与既往研究结论相悖的是，本研究中奖励率最大化倾向普遍存在于所有决策框架中，并未局限于觅食类任务场景。此外，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显著相关。这一发现支持了一种演化假说：进化选择青睐双曲线贴现行为，是因为该机制可通过灵活调整对“小而即时”与“大而延迟”收益的偏好，助力实现奖励率最大化。由此可见，奖励率最大化或许是一条普适性原则，从整体上塑造了跨物种、大范围跨期决策问题中的决策行为模式。