We study the intergenerational accumulation of knowledge in an infinite-horizon model of communication. Each in a sequence of players receives an informative but imperfect signal of the once-and-for-all realization of an unobserved state. The state affects all players’ preferences over present and future decisions. Each player observes his own signal but does not directly observe the realized signals or actions of his predecessors. Instead, he must rely on cheap-talk messages from the previous players to fathom the past. Each player is therefore both a receiver of information with respect to his decision, and a sender with respect to all future decisions. Senders’ preferences are misaligned with those of future decision makers.
We ask whether there exist “full learning” equilibria — ones in which the players’ posterior beliefs eventually place full weight on the true state. We show that, regardless of how small the misalignment in preferences is, such equilibria do not exist. This is so both in the case of private communication in which each player only hears the message of his immediate predecessor, and in the case of public communication, in which each player hears the message of all previous players. Surprisingly, in the latter case full learning may be impossible even in the limit as all players become infinitely patient. We also consider the case where all players have access to a mediator who can work across time periods arbitrarily far apart. In this case full learning equilibria exist.
Examples of repeated destructive behavior abound throughout the history of human societies. This paper examines the role of social memory — a society’s vicarious beliefs about the past — in creating and perpetuating destructive conflicts. We examine whether such behavior is consistent with the theory of rational strategic behavior.
We analyze an infinite-horizon model in which two countries face off each period in an extended Prisoner’s Dilemma game in which an additional possibility of mutually destructive “all out war” yields catastrophic consequence for both sides. Each country is inhabited by a dynastic sequence of individuals who care about future individuals in the same country, and can communicate with the next generation of their countrymen using private messages. The two countries’ actions in each period also produce physical evidence; a sequence of informative but imperfect public signals that can be observed by all current and future individuals.
We find that, provided the future is sufficiently important for all individuals, regardless of the precision of physical evidence from the past there is an equilibrium of the model in which the two countries’ social memory is systematically wrong, and in which the two countries engage in all out war with arbitrarily high frequency.
Surprisingly, we find that degrading the quality of information that individuals have about current decisions may “improve” social memory so that it can no longer be systematically wrong. This in turn ensures that arbitrarily frequent all out wars cannot take place.
JEL Classification: C72, C79, D80, D83, D89
Keywords: Social memory, Private communication, Dynastic games, Physical evidence
A canonical interpretation of an infinitely repeated game is that of a “dynastic” repeated game: a stage game repeatedly played by successive generations of finitely-lived players with dynastic preferences. These two models are in fact equivalent when the past history of play is observable to all players.
In our model all players live one period and do not observe the history of play that takes place before their birth, but instead receive a private message from their immediate predecessors.
Under very mild conditions, when players are sufficiently patient, all feasible payoff vectors (including those below the minmax) can be sustained as a Sequential Equilibrium of the dynastic repeated game with private communication. The result applies to any stage game for which the standard Folk Theorem yields a payoff set with a non-empty interior.
Our results stem from the fact that, in equilibrium, a player may be unable to communicate effectively relevant information to his successor in the same dynasty. This, in turn implies that following some histories of play the players’ equilibrium beliefs may violate “Inter-Generational Agreement.”
JEL Classification: C72, C73, D82
Keywords: Dynastic repeated games, Private communication, Folk theorem