COPING WITH RARE AND EXTREME EVENTS: BLACK SWAN AVOIDANCE AND JACKPOT SEEKING IN HUMANS AND RATS

Uncertainty is a fundamental feature of decision-making and has been extensively studied in neuroscience and economics. However, little is known about how humans and other animals cope with events that are simultaneously very rare (probability < 2%) and extreme in their consequences, referred to here as Rare and Extreme Events (REEs). Such events can be negative (Black Swans, BS) or positive (Jackpots, JP).

To investigate behavioral responses to REEs, we studied humans and rats using a four-armed bandit task involving stochastic gains and losses, including occasional exposure to REEs. Previous work in rats revealed a marked sensitivity to REEs, characterized by two main strategies: strong avoidance of BS and partial seeking of JP.

In the present study, we extended this paradigm to humans using two task variants that differed in their mode of entry: one relying on training and implicit learning, and the other providing a partial explicit description of outcomes. Across both tasks, humans exhibited behavioral strategies remarkably similar to those observed in rats, showing robust BS avoidance and moderate JP seeking, with substantial inter-individual variability in strategy strength. Notably, responses to REEs were asymmetric and consistent with a gambling fallacy: following a BS, participants avoided risky options, apparently anticipating the recurrence of another BS, whereas, after experiencing a JP, most participants shifted toward safer choices, behaving as if another JP was unlikely to occur.

These findings suggest conserved cross-species strategies for coping with radical uncertainty and highlight a fundamental asymmetry in how positive and negative REE shape decision-making.