Risky choices with potentially ‘fatal’ outcomes: Introducing the Extinction Gambling Task

Humans often need to make choices that trade off a benefit against a small chance of extinction (e.g., death or even human extinction). We developed a novel risky-choice gambling task, the ”Extinction Gambling Task'', to study how people reason about these types of events. In the Extinction Gambling Task, participants need to decide between a risky gamble (with a higher expected payoff but a small chance of extinction) and a safe gamble (lower expected payoff but no chance of extinction) across a series of trials (100 in our study). Our task has two possible payoff structures to model extinction risk: In the “complete extinction scenario” drawing the extinction option implies that all past earnings are wiped out and that no earnings can be accumulated in future trials. In the “opportunity cost extinction” scenario, extinction merely implies that the participant cannot earn additional money in trials after the extinction event; however, they can keep their earnings from previous trials. We derived optimal decision strategies for both of these scenarios and validated them against simulations. In the “complete extinction case”, the optimal strategy only considers the probability of the risky choice and the number of trials but not the order in which choices are made. In the “opportunity cost extinction” case, the optimal strategy considers both the probability of risky choices and the order in which choices are made. Compared to the complete extinction scenario, the optimal number of risky choices is higher in the opportunity cost case. Furthermore, the optimal strategy in the opportunity cost case involves first playing safe and switching to solely playing the risky gamble towards the end of the experiment. We compared participants' performance across both scenarios in a between-participants design where each participant played one round of 100 trials. We found that (1) people are far too risk-seeking in early trials, which leads a large proportion of participants to become extinct relatively soon, and (2) for participants in the opportunity cost condition, the first choice of the risky gamble is later than for participants in the complete extinction condition, indicating that participants have some understanding of the different affordances of the two scenarios. Further, participants qualitatively follow the optional strategy by increasing the proportion of risky choices towards the end in the opportunity cost condition of the experiment, whereas participants in the complete extinction case do not show this pattern. We will present results from a mixture model describing different groups of participants. The “Extinction Gambling task” is a promising approach that can shed light on human decision processes with important real-world implications.