Economic choices reveal probability distortion in macaque monkeys.


Change log
Authors
Stauffer, William R  ORCID logo  https://orcid.org/0000-0003-1031-8824
Bossaerts, Peter 
Schultz, Wolfram 
Abstract

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.

Description
Keywords
economic choice, monkey, probability distortion, utility, Animals, Choice Behavior, Conditioning, Classical, Cues, Games, Experimental, Macaca mulatta, Male, Probability, Reward, Risk-Taking
Journal Title
J Neurosci
Conference Name
Journal ISSN
0270-6474
1529-2401
Volume Title
35
Publisher
Society for Neuroscience
Sponsorship
Medical Research Council (G0001354)
Wellcome Trust (095495/Z/11/Z)
Medical Research Council (G1000183)
This work was supported by the Wellcome Trust, European Research Council (ERC) and Caltech Conte Center.