Outcome expectancy and suboptimal risky choice in nonhuman primates
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Outcome expectancy and suboptimal risky choice in nonhuman primates Travis R. Smith 1
&
Michael J. Beran 2
# The Psychonomic Society, Inc. 2020
Abstract Animals will favor a risky option when a stimulus signaling reward bridges the choice and the outcome. The present experiments investigated signal-induced risky choices and reward-outcome expectations in rhesus and capuchin monkeys. Risky choice was assessed by preference for a large-probabilistic reward over a modest-certain reward. Outcome expectancy was assessed by providing a truncation-response to shorten the delay period. In Experiment 1 both species generally favored the risky option compared to a safe option when the outcomes were signaled and generally shortened the delays except when a signaled-loss stimulus was presented. The use of the delay-truncation response suggested that the monkeys were sensitive to the information conveyed by the stimulus. Experiments 2 and 3 were designed to investigate whether the delay-truncation response used by capuchin monkeys was strategically used reflecting explicit decision-making versus a conditioned response to reward stimuli. A perceptual judgment task was included and the selective use of the delay-truncation response on unsignaled correct trials may suggest the involvement of metacognitive processes. The capuchin monkeys generally truncated the delays except under conditions where reward would not be expected (risky-loss or incorrect-judgment). When the outcomes were unsignaled during the delay some capuchin monkeys were less likely to truncate the delay following an incorrect task response. Overall, the monkeys: (1) made more risky choices when the outcomes were signaled – consistent with gambling-like behavior. (2) selectively truncated the unsignaled delays when rewards could be anticipated (even when metacognitive-like awareness guided anticipation) – suggesting that delay truncation responses reflect explicit outcome expectancy. Keywords Risk preference . Gambling . Capuchin monkeys . Rhesus monkeys . Signaled reinforcement . Metacognition
Introduction Risky choice, defined here as a choice between an option offering probabilistic outcomes and a safe(r) option offering certain outcomes, is studied in humans and nonhuman animals (animals, hereafter). Studying risky decision-making is important to understanding decision-making across a range of disciplines (Mishra, 2014) and in understanding the fundamental cognitive processes that govern decision-making in animals (e.g., Kacelnik & Bateson, 1996; Kacelnik & El Mouden,
* Travis R. Smith [email protected] 1
Department of Psychological Sciences, Kansas State University, 492 Bluemont Hall, 1114 Mid-Campus Dr North, Manhattan, KS 66506-5302, USA
2
Language Research Center and Department of Psychology, Georgia State University, Atlanta, GA, USA
2013). Animal models of risky choice have practical implications in understanding human risky decision-making in the real-world, and they aid in the development of interventions that can attenuate maladaptive
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