Observations: playing for real
Analyzing economic behavior using virtual world cybergames.
AUTHORS: Lovejoy, Kristin
Multiple selves in intertemporal choice
We propose that individuals consider future versions of themselves to truly be separate persons, not simply as a convenient modeling device but in terms of actual brain systems and decision-making processes. Intertemporal choices are thus quite literally strategic interactions between multiple agents. Previous neuroscientific studies have found evidence that systems involved with Theory of Mind (that is, mentalizing other agents) are similar to those involved with prospection (imagining oneself in the future). We provide a conceptual framework for this work and suggest that, instead of prospection, a more analogous future task is one that concerns intertemporal choice and time preferences, since these involve implicit prediction of future actions. Recent functional imaging studies appear to confirm such a link. Additional studies - behavioral, clinical, and neuroimaging - are proposed in order to confirm the specific nature of the correspondence and to elucidate the underlying mechanisms. Finally, given that society may have a vested interest in promoting the welfare of future selves, we discuss possible policy implications of departing from the standard framework in which individuals act in their own best interests as defined over the entire lifetime.
AUTHORS: Wegener, Jon; Jamison, Julian
Games with synergistic preferences
In economic situations a player often has preferences regarding not only his or her own outcome but also regarding what happens to fellow players, concerns that are entirely apart from any strategic considerations. While this can be modeled directly by simply writing down a player's final preferences, these are commonly unknown a priori. In many cases it is therefore both helpful and instructive to explicitly model these interactions. This paper, building on a model due to Bergstrom (1989, 1999), presents a simple structure in the context of game theory that incorporates the "synergies" between players. It is powerful enough to cover a wide range of such interactions and model many disparate experimental and empirical results, yet it is straightforward enough to be used in many applied situations where altruism, or a baser motive, is implied.
AUTHORS: Jamison, Julian
Valuable cheap talk and equilibrium selection
Intuitively, we expect that players who are allowed to engage in costless communication before playing a game would be foolish to agree on an inefficient equilibrium. At the same time, however, such preplay communication has been suggested as a rationale for expecting Nash equilibrium in general. This paper presents a plausible formal model of cheap talk that distinguishes and resolves these possibilities. Players are assumed to have an unlimited opportunity to send messages before playing an arbitrary game. Using an extension of fictitious play beliefs, minimal assumptions are made concerning which messages about future actions are credible and hence contribute to final beliefs. In this environment it is shown that meaningful communication among players leads to a Nash equilibrium (NE) of the action game. Within the set of NE, efficiency then turns out to be a consequence of imposing optimality on the cheap talk portion of the extended game. This finding contrasts with previous "babbling" results.
AUTHORS: Jamison, Julian
Minimally acceptable altruism and the ultimatum game
I suppose that people react with anger when others show themselves not to be minimally altruistic. With heterogeneous agents, this can account for the experimental results of ultimatum and dictator games. Moreover, it can account for the surprisingly large fraction of individuals who offer an even split, with parameter values that are more plausible than those required to explain outcomes in these experiments with the models of Levine (1998), Fehr and Schmidt (1999), Dickinson (2000), and Bolton and Ockenfels (2000).
AUTHORS: Rotemberg, Julio J.
Strategic choice of preferences: the persona model
We introduce a modification to the two-timescale games studied in the evolution of preferences (EOP) literature. In this modification, the strategic process occurring on the long timescale is learning by an individual across his or her lifetime, not natural selection operating on genomes over multiple generations. This change to the longer timescale removes many of the formal difficulties of EOP models and allows us to show how two-timescale games can provide endogenous explanations for why humans sometimes adopt interdependent preferences and sometimes exhibit logit quantal response functions. In particular, we show that our modification to EOP explains experimental data in the Traveler?s Dilemma. We also use our modification to show how cooperation can arise in nonrepeated versions of the Prisoner?s Dilemma (PD). We then show that our modification to EOP predicts a ?crowding out? phenomenon in the PD, in which introducing incentives to cooperate causes players to stop cooperating instead. We also use our modification to predict a tradeoff between the robustness and the benefit of cooperation in the PD.
AUTHORS: Harre, Michael; Wolpert, David H.; Newth, David; Jamison, Julian
Some problems of infinite regress in social-choice models: a category theory solution
An analysis of the infinite regress that appears in the statement of Gauthier's bargaining approach to social choice. The author shows how category theory provides the tools for constructing the appropriate bargaining models by furnishing a setting for the concepts of continuity, limits, and fixed points.
AUTHORS: Alameddine, Fadi
Bargaining and the value of money
Search models of monetary exchange have typically relied on Nash (1950) bargaining or strategic games that yield an equivalent outcome to determine the terms of trade. By considering alternative axiomatic bargaining solutions in a simple search model with divisible money, we show how this choice matters for important results such as the ability of the optimal monetary policy to generate an efficient allocation. We show that the quantities traded in bilateral matches are always inefficiently low under the Nash (1950) and Kalai-Smorodinsky (1975) solutions, whereas under strongly monotonic solutions such as the egalitarian solution (Luce and Raiffa, 1957; Kalai, 1977), the Friedman Rule achieves the first best allocation. We evaluate quantitatively the welfare cost of inflation under the different bargaining solutions, and we extend the model to allow for endogenous market composition.
AUTHORS: Waller, Christopher J.; Rocheteau, Guillaume
Bargaining a monetary union
AUTHORS: Chang, Roberto
Financial matchmakers in credit markets with heterogeneous borrowers
What happens when liquidity increases in credit markets and more funds are channeled from borrowers to lenders? We examine this question in a general equilibrium model where financial matchmakers help borrowers (firms) and lenders (households) search out and negotiate profitable matches and where the composition of heterogeneous borrowers adjusts to satisfy equilibrium entry conditions. We find that enhanced liquidity causes entry by all borrowers and tends to benefit low-quality borrowers disproportionately. However, liquid credit markets may or may not be associated with higher output and welfare. The result is determined by whether the effect of higher market participation outweighs that of lower average quality. The net effect depends crucially on the source of the liquidity shock (financial matching efficacy, productivity, or entry barriers).
AUTHORS: Becsi, Zsolt; Li, Victor E.; Wang, Ping