Abstract
A key component of economic decisions is the integration of information about reward outcomes and probabilities in selecting between competing options. In many species, risky choice is influenced by the magnitude of available outcomes, probability of success and the possibility of extreme outcomes. Chimpanzees are generally regarded to be risk-seeking. In this study, we examined two aspects of chimpanzees' risk preferences: first, whether setting the value of the non-preferred outcome of a risky option to zero changes chimpanzees’ risk preferences, and second, whether individual risk preferences are stable across two different measures. Across two experiments, we found chimpanzees (Pan troglodytes, n = 23) as a group to be risk-neutral to risk-avoidant with highly stable individual risk preferences. We discuss how the possibility of going empty-handed might reduce chimpanzees' risk-seeking relative to previous studies. This malleability in risk preferences as a function of experimental parameters and individual differences raises interesting questions about whether it is appropriate or helpful to categorize a species as a whole as risk-seeking or risk-avoidant.This article is part of the theme issue ‘Existence and prevalence of economic behaviours among non-human primates’.
Highlights
Decisions under risk and uncertainty are a ubiquitous part of both human and animal lives, ranging from complex monetary investment decisions in humans to decisions about where and when to forage or how to pursue mating efforts for most other animals
Haun et al [16] presented all four species of great apes with a setup where subjects could choose between a safe reward option and a risky option, which consisted of a variable number of ‘risky cups’ that could potentially contain a larger piece of banana
Across two experiments we found less risk-seeking in chimpanzees compared with previous findings [10,16,17,18,19]
Summary
Decisions under risk and uncertainty are a ubiquitous part of both human and animal lives, ranging from complex monetary investment decisions in humans to decisions about where and when to forage or how to pursue mating efforts for most other animals. Chimpanzees’ avoidance of the more variable option may have been related to the possibility of getting nothing in a few cases (risk of zero was 10% for the high-variance stack) or may be the result of differences in experimental procedures compared with previous studies (for example, having two static stacks of pre-baited cups to choose from, as in the Primate Gambling Task, is different from having an experimenter set up and re-bait two cups repeatedly for each choice trial) In any case, this finding provides an interesting first indication that the possibility of getting nothing might elicit different responses, namely playing it safer, compared with small-reward gambles in chimpanzees.
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