Stalnaker: Modeling Credibility

by Yang Liu

CUNY SEMINAR IN LOGIC AND GAMES
Modeling Credibility
Robert Stalnaker (MIT/Columbia)
4:15 – 6:15 PM, Friday, December 6, 2013
Room 6496, CUNY GC

Abstract. A “cheap talk” move in a game is a move that does not affect either the subsequent moves available, or the payoffs, for any of the players. The point of such a move can only be to convey information to the other players, but nothing endogenous to the game can determine either what information the player aims to convey, or whether she will be successful in conveying that information. We might add to the game a language that is presumed to be common knowledge among the players, with a semantics that determines the informational content of the cheap talk moves. But since these moves do not affect any payoffs, there is no assurance that the players will tell the truth. My concern in this talk will be with the problem of characterizing the conditions under which a cheap talk message will be credible: the conditions under which players receiving a message will have reason to believe that the sending player is telling the truth. The rough idea is that a message is credible when the payoffs are such that the sending player wants the receiving player to believe the message only if it is true, but there are problems making this idea precise. I will look at some simple and familiar games when they are preceded by a cheap talk move in which a player has the opportunity to signal what moves he intends to make, and at some signaling games that raise problems for the definition of credibility.