Stauffer William R, Lak Armin, Bossaerts Peter, Schultz Wolfram
Department of Physiology, Development and Neuroscience, University of Cambridge, Cambridge CB2 3DY, United Kingdom,
Department of Physiology, Development and Neuroscience, University of Cambridge, Cambridge CB2 3DY, United Kingdom.
J Neurosci. 2015 Feb 18;35(7):3146-54. doi: 10.1523/JNEUROSCI.3653-14.2015.
Economic choices are largely determined by two principal elements, reward value (utility) and probability. Although nonlinear utility functions have been acknowledged for centuries, nonlinear probability weighting (probability distortion) was only recently recognized as a ubiquitous aspect of real-world choice behavior. Even when outcome probabilities are known and acknowledged, human decision makers often overweight low probability outcomes and underweight high probability outcomes. Whereas recent studies measured utility functions and their corresponding neural correlates in monkeys, it is not known whether monkeys distort probability in a manner similar to humans. Therefore, we investigated economic choices in macaque monkeys for evidence of probability distortion. We trained two monkeys to predict reward from probabilistic gambles with constant outcome values (0.5 ml or nothing). The probability of winning was conveyed using explicit visual cues (sector stimuli). Choices between the gambles revealed that the monkeys used the explicit probability information to make meaningful decisions. Using these cues, we measured probability distortion from choices between the gambles and safe rewards. Parametric modeling of the choices revealed classic probability weighting functions with inverted-S shape. Therefore, the animals overweighted low probability rewards and underweighted high probability rewards. Empirical investigation of the behavior verified that the choices were best explained by a combination of nonlinear value and nonlinear probability distortion. Together, these results suggest that probability distortion may reflect evolutionarily preserved neuronal processing.
经济选择在很大程度上由两个主要因素决定，即奖励价值（效用）和概率。尽管非线性效用函数几个世纪以来已为人所知，但非线性概率加权（概率扭曲）直到最近才被视为现实世界选择行为中普遍存在的一个方面。即使结果概率是已知且被认可的，人类决策者通常也会高估低概率结果而低估高概率结果。虽然最近的研究测量了猴子的效用函数及其相应的神经关联，但尚不清楚猴子是否以与人类相似的方式扭曲概率。因此，我们研究了猕猴的经济选择，以寻找概率扭曲的证据。我们训练了两只猴子，让它们根据具有恒定结果值（0.5毫升或无）的概率性赌博来预测奖励。获胜的概率通过明确的视觉线索（扇形刺激）来传达。赌博之间的选择表明猴子利用明确的概率信息做出有意义的决策。利用这些线索，我们从赌博和安全奖励之间的选择中测量了概率扭曲。对选择进行参数建模揭示了具有倒S形的经典概率加权函数。因此，这些动物高估了低概率奖励而低估了高概率奖励。对行为的实证研究证实，这些选择最好由非线性价值和非线性概率扭曲的组合来解释。总之，这些结果表明概率扭曲可能反映了进化上保留的神经元处理过程。
