Abstract
In contrast to humans and most other animals, rhesus macaques strongly prefer risky rewards to safe ones with similar expected value. Why macaques prefer risk while other animals typically avoid it remains puzzling and challenges the idea that monkeys provide a model for human economic behavior. Here we argue that monkeys’ risk-seeking preferences are neither mysterious nor unique. Risk-seeking in macaques is possibly induced by specific elements of the tasks that have been used to measure their risk preferences. The most important of these elements are (1) very small stakes, (2) serially repeated gambles with short delays between trials, and (3) task parameters that are learned through experience, not described verbally. Together, we hypothesize that these features will readily induce risk-seeking in monkeys, humans, and rats. Thus, elements of task design that are often ignored when comparing studies of risk attitudes can easily overwhelm basal risk preferences. More broadly, these results highlight the fundamental importance of understanding the psychological basis of economic decisions in interpreting preference data and corresponding neural measures.
Highlights
In 1996, Kacelnik and Bateson published a comprehensive review of the literature on animal risk preferences (Kacelnik and Bateson, 1996)
Preferences for risk are strongly dependent on these task parameters, and all published studies of risk attitudes in rhesus macaques have in common the three elements mentioned above
Future studies should directly manipulate these elements in isolation, testing the hypothesis that they are responsible for promoting macaque risk-seeking
Summary
In 1996, Kacelnik and Bateson published a comprehensive review of the literature on animal risk preferences (Kacelnik and Bateson, 1996) They reported that, across 59 different studies, the majority of animals exhibited risk-averse preferences during gambles for food rewards. As the size of the large and small reward diverged, and risk level of the risky option increased, monkeys became even more risk-seeking These monkeys even continued to prefer the risky option in a control experiment where the probability of winning was only 1/3 and the mathematical expected value of the gamble was lower than that of the safe option (McCoy and Platt, 2005). The most important of these elements are (1) decisions have very small stakes, a squirt or two of juice, (2) decisions are repeated hundreds or thousands of times www.frontiersin.org
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