The Logic of Tsunami-Tendenko: Super-Rationality in the Altruist's Dilemma

This paper examines decision making in disasters. I constructed a two-person game (with two alternatives) of evacuation, which is formulated as the Altruist’s Dilemma (Schelling 1968). I would like to show that “tsunami-tendenko” (Yamashita 2005) is the super-rationality solution to the game.

“Tsunami-tendenko” is a reformulation of a moral handed down in Sanriku area (the northeastern side of the main island) of Japan. It says that we should evacuate from tsunami separately, starting as early as possible, in haste, and without caring for others. The principle is to help yourself based on a tacit agreement and avoid mutual destruction. Sociologists, psychologists, and philosophers (e.g., Arce, et al. 2017; Goltz 2017; Kodama 2015; Yamori 2014) examined (and some of them criticized) tsunami-tendenko. There was no study, however, that described the evacuation decision as the Altruist’s Dilemma.

Super-rationality is the rationality that depends on the others’ rationality, which depends on their dependence on everyone’s rationality, and so on (Hofstadter 1985). Previous studies applied the concept of super-rationality to the Prisoner’s Dilemma (e.g., Fourny 2020; Shafir & Tversky 1992; Wang, et al. 2021) and to the Volunteer’s Dilemma (Diekmann 1985). Super-rationality has not been discussed, however, in the context of the Altruist’s Dilemma.

The evacuation game assumes two types for the players: own payoff watcher and the other’s payoff watcher. If both players rely upon super-rationality, regardless of their types, they separately evacuate without caring for each other. This Pareto-efficient equilibrium is, however, vulnerable to doubt about the other’s rationality. The other’s gesture of a helping hand may become a signal that triggers doubt.

Note that this game does not assume family or community ties. In this sense, the super-rationality solution implies the importance of generalized trust rather than trust in family members, neighbors, or local community that Yamori (2014) emphasized.