Endogenous correlated equilibria in noncooperative games

Most of the results of modern game theory presuppose that the choices rational agents make in noncooperative games are probabilistically independent. In this paper I argue that there is noa priori reason for rational agents to assume probabilistic independence. I introduce a solution concept for noncooperative games called anendogenous correlated equilibrium, which generalizes the Nash equilibrium concept by dropping probabilistic independence. I contrast the endogenous correlated equilibrium with the correlated equilibrium defined by Aumann (1974, 1987). I conclude that in general the endogenous correlated equilibrium concept is a more appropriate solution concept for noncooperative game theory than the less general Nash equilibrium concept. I close by discussing the relationship between endogenous correlated equilibrium and the game solution concept calledrationalizability introduced by Bernheim (1984) and Pearce (1984).     

Comparative statics for rank-dependent expected utility theory

Recently, a number of generalizations of the expected utility (EU) model have been proposed. In order to make such generalizations useful, it is necessary that they should yield sharp comparative static results, like those obtained using EU theory. In this article, rank dependent expected utility (RDEU) theory, a generalization of EU theory based on the concept of probability weighting, is examined. A number of methods of extending results from EU to RDEU are considered. It is shown that a major class of comparative static results can be extended to the RDEU model, but not to the case of general smooth preferences. This is because RDEU maintains the separation between probabilities and utilities that is abandoned in the general case.     

Comparative accuracy of value solutions in non-sidepayment games with empty core

This article reports a test of the predictive accuracy of solution concepts in cooperative non-sidepayment n-person games with empty core. Six solutions were tested. Three of these were value solutions (i.e., -transfer value, -transfer nucleolus, and -transfer disruption value) and three were equilibrium solutions (deterrence set, stable set, and imputation set). The test was based on a laboratory experiment utilizing 5-person, 2-choice normal form games with empty core; other related data sets were also analyzed. Goodness-of-fit results based on discrepancy scores show that the three value solutions are about equally accurate in predicting outcomes, and that all three are substantially more accurate than the other solutions tested.     

Effects of fixed costs in two-person sequential bargaining

Rubinstein (1982) considered the problem of dividing a given surplus between two players sequentially, and then proposed a model in which the two players alternately make and respond to each other's offers through time. He further characterized the perfect equilibrium outcomes, which depend on the players time preferences and order of moves. Using both equal and unequal bargaining cost conditions and an unlimited number of rounds, two experiments were designed to compare the perfect equilibrium model to alternative models based on norms of fairness. We report analyses of final agreements, first offers, and number of bargaining rounds, which provide limited support to the perfect equilibrium model, and then conclude by recommending a shift in focus from model testing to specification of the conditions favoring one model over another.     

NTU core,TU core and strong equilibria of coalitional population games with infinitely many pure strategies

Theory and Decision - Inspired by Scarf (J Econ Theory 3: 169–181,  1971), Zhao (Int J Game Theory 28: 25–34, 1999), Sandholm (Population games and...     

The preservation of multivariate comparative statics in nonexpected utility theory

This article investigates the preservation of multivariate expected utility comparative statics for “smooth” nonexpected utility representations. Specifically, we answer the following question: if an expected utility comparative statics property depends only on preferences over sure prospects, then when will a nonexpected utility maximizer with identical sure preferences also satisfy that property? We demonstrate that the effects of increased risk aversion are preserved under the “Almost Degenerate Independence” axiom, but that those of distribution changes of exogenous risks are not preserved under stringent assumptions. Hence, nonexpected utility comparative statics may diverge from expected utility, even for “first-order” properties—those whose effect is determinable from restrictions on “local” utility functions.     

Left-Side strong increases in risk and their comparative statics

This paper introduces a new concept of left-side strong increases in risk (L-SIR) that extends the definition of strong increases in risk (SIR). We also provide somewhat stronger restrictive set of risk-averse decision-makers with a non-negative third derivative utility (prudence) to obtain an appealing comparative statics result for L-SIR.The authors gratefully acknowledge the helpful comments and suggestions of an anonymous referee     

Rational beliefs in extensive games

Given an extensive game, with every node x and every player i a subset k _i (x) of the set of terminal nodes is associated, and is given the interpretation of player i's knowledge (or information) at node x. A belief of player i is a function that associates with every node x an element of the set K _i (x). A belief system is an n-tuple of beliefs, one for each player. A belief system is rational if it satisfies some natural consistency properties. The main result of the paper is that the notion of rational belief system gives rise to a refinement of the notion of subgame-perfect equilibrium.     

Staying power in sequential games

Staying power is the ability of a player to hold off choosing a strategy in a two-person game until the other player has selected his, after which the players are assumed to be able to move and countermove sequentially to ensure their best possible outcomes before the process cycles back to the initial outcome and then repeats itself (rational termination). These rules of sequential play induce a determinate, Paretosuperior outcome in all two-person, finite, sequential games in which the preferences of the players are strict.In 57 of the 78 distinct 2 × 2 ordinal games (73 percent), it makes no difference who the (second-moving) player with staying power is, but in the other 21 games the outcome is power-dependent. In all but one of these games, staying power benefits the player who possesses it.If no player has staying power, the outcomes that result from sequential play and rational termination are called terminal; they coincide with staying power outcomes if they are Pareto-superior. Normative implications of the analysis for rationally justifying cooperation in such games as Prisoners' Dilemma and Chicken, and implementing Pareto-superior outcomes generally, are also discussed.We are grateful to D. Marc Kilgour for very valuable comments on an earlier version of this paper, causing us to rethink and redefine staying power. The earlier version was presented at the Seventeenth North American Conference, Peace Science Society (International), University of Pennsylvania, November 9–11, 1981.     

Hierarchies achievable in simple games

A previous work by Friedman et al. (Theory and Decision, 61:305–318, 2006) introduces the concept of a hierarchy of a simple voting game and characterizes which hierarchies, induced by the desirability relation, are achievable in linear games. In this paper, we consider the problem of determining all hierarchies, conserving the ordinal equivalence between the Shapley–Shubik and the Penrose–Banzhaf–Coleman power indices, achievable in simple games. It is proved that only four hierarchies are non-achievable in simple games. Moreover, it is also proved that all achievable hierarchies are already obtainable in the class of weakly linear games. Our results prove that given an arbitrary complete pre-ordering defined on a finite set with more than five elements, it is possible to construct a simple game such that the pre-ordering induced by the Shapley–Shubik and the Penrose–Banzhaf–Coleman power indices coincides with the given pre-ordering.     

Team selection in children's games

Games provide valuable learning experiences for children. Team games in particular involve them in a variety of roles and responsibilities. This article examines team selection in spontaneous playground games in an elementary school enrolling 500. The approach is naturalistic and ethnographic. The children were very concerned about choosing teams of comparable ability so as to ensure an even and fair contest. The key was careful selection of team captains based on athletic ability. Friendship played a secondary role. These athletically skilled captains in turn chose teams according to ability. Girls and less skilled boys were not selected to lead because that would threaten the balance of the teams. Children chosen last for the team or not chosen at all felt rejected socially as well as athletically.     

Punishing greediness in divide-the-dollar games

Brams and Taylor 1994 presented a version of the divide-the-dollar game (DD), which they call DD1. DD1 suffers from the following drawback: when each player demands approximately the entire dollar, then if the least greedy player is unique, then this player obtains approximately the entire dollar even if he is only slightly less greedy than the other players. I introduce a parametrized family of 2-person DD games, whose “endpoints” (the games that correspond to the extreme points of the parameter space) are (1) a variant of DD1, and (2) a game that completely overcomes the greediness-related problem. I also study an n-person generalization of this family. Finally, I show that the modeling choice between discrete and continuous bids may have far-reaching implications in DD games.     

Deterministic transformations of random variables and the comparative statics of risk

In this article, a general class of deterministic transformations that can be interpreted as changes in risk are identified. This provides a fourth characterization of a Rothschild-Stiglitz increase in risk. In addition, a particular subclass of these transformations, termed simple transformations, is shown to be well suited for comparative static analyses. This subclass contains as a special case the linear transformation used so often in the literature. A theorem is presented that generalizes the known comparative static results for large as well as small changes in risk.     

An incompleteness problem in Harsanyi's general theory of games and certain related theories of non-cooperative games

The theory of games recently proposed by John C. Harsanyi in A General Theory of Rational Behavior in Game Situations, (Econometrica, Vol. 34, No. 3) has one anomalous feature, viz., that it generates for a special class of non-cooperative games solutions which are not equilibrium points. It is argued that this feature of the theory turns on an argument concerning the instability of weak equilibrium points, and that this argument, in turn, involves appeal to an unrestricted version of a postulate subsequently included in the theory in restricted form. It is then shown that if this line of reasoning is permitted, then one must, by parity of reasoning, permit another instability argument. But, if both of these instability arguments are permitted in the construction of the theory, the resultant theory must be incomplete, in the sense that there will be simple non-cooperative games for which such a theory cannot yield solutions. This result is then generalized and shown to be endemic to all theories which have made the equilibrium condition central to the treatment of non-cooperative games. Some suggestions are then offered concerning how this incompleteness problem can be resolved, and what one might expect concerning the postulate structure and implications of a theory of games which embodies the revisions necessitated by a resolution of this problem.This research was supported by a grant to the author from the City University of New York Faculty Research Award Program.     

Trading transforms of non-weighted simple games and integer weights of weighted simple games

Theory and Decision - This study investigates simple games. A fundamental research question in this field is to determine necessary and sufficient conditions for a simple game to be a weighted...     

Cycles versus equilibrium in evolutionary games

Mixed-strategy equilibria are typically rather unstable in evolutionary game theory. “Monocyclic” games, such as Rock–Paper–Scissors, have only mixed equilibria, some of which are “stable” in the sense that sequential best replies lead to them; yet, even these games are prone to stable cycles under discrete-time simultaneous best replies, giving an unusual equilibrium-selection problem. This article analyzes such games in a random-utility setting where changing strategies is costly, and the speed of the dynamic is, thus, endogenous. The stochastically stable outcome is determined by the cost of switching strategies; when switching costs are high, mixed equilibria are selected, whereas when switching costs are low, cycles are selected.