Monkeys and other animals appear to share with humans two risk attitudes predicted by prospect theory: an inverse-S-shaped probability-weighting (PW) function and a steeper utility curve for losses than for gains. These findings suggest that such preferences are stable traits with common neural substrates. We hypothesized instead that animals tailor their preferences to subtle changes in task contexts, making risk attitudes flexible. Previous studies used a limited number of outcomes, trial types, and contexts. To gain a broader perspective, we examined two large datasets of male macaques’ risky choices: one from a task with real (juice) gains and another from a token task with gains and losses. In contrast to previous findings, monkeys were risk seeking for both gains and losses (i.e., lacked a reflection effect) and showed steeper gain than loss curves (loss seeking). Utility curves for gains were substantially different in the two tasks. Monkeys showed nearly linear PWs in one task and S-shaped ones in the other; neither task produced a consistent inverse-S-shaped curve. To account for these observations, we developed and tested various computational models of the processes involved in the construction of reward value. We found that adaptive differential weighting of prospective gamble outcomes could partially account for the observed differences in the utility functions across the two experiments and thus provide a plausible mechanism underlying flexible risk attitudes. Together, our results support the idea that risky choices are constructed flexibly at the time of elicitation and place important constraints on neural models of economic choice.
Bibliographical noteFunding Information:
Received Aug. 9, 2017; revised March 19, 2018; accepted March 23, 2018. Author contributions: S.F., H.A., B.H., and A.S. edited the paper; B.H. and A.S. wrote the first draft of the paper; S.F.,B.H.,andA.S.designedresearch;S.F.,H.A.,B.H.,andA.S.performedresearch;S.F.andA.S.analyzeddata;B.H. and A.S. wrote the paper. This work is supported by the National Science Foundation (CAREER Award BCS1253576 to B.H. and EPSCoR RII Track-2 FEC Grant to A.S.) and the National Institutes of Health (Grant R01 DA038615 to B.H.). We thank Meghan Castagno,MarcMancarella,andCalebStraitforassistancewithdatacollectionandReiAkaishi,BenEisenreich,Clara Guo, Daeyeol Lee, and Katherine Rowe for helpful comments on the manuscript. The authors declare no competing financial interests. Correspondence should be addressed to the following: Alireza Soltani, Department of Psychological and Brain Sciences, Moore 6207, Dartmouth College, Hanover, NH 03755, E-mail: firstname.lastname@example.org. DOI:10.1523/JNEUROSCI.2260-17.2018 Copyright © 2018 the authors 0270-6474/18/384383-16$15.00/0
- Cognitive flexibility
- Loss seeking
- Probability distortion
- Reflection effect