Abstract: We propose a game-theoretic model of reciprocity and trust that incorporates personality traits. In the model, positive and negative reciprocity are “reciprocal preferences:” parameters of heterogeneous utility functions that take into account the material welfare of others (positively if they have been kind, negatively if they have been hostile). Trust, on the other hand, is an individual bias that distorts probabilistic beliefs about the trustworthiness of others. Unlike typical game-theoretic models, our model provides an explanation for the heterogeneity of preferences and probabilistic beliefs: a person's personality traits determine both the parameters of his utility function and the magnitude of his beleif bias. We tested the model experimentally. Subjects completed a psychometric questionnaire that measures three personality traits: positive reciprocity, negative reciprocity, and trust. Subsequently, they played a sequential prisoner's dilemma with random re-matching and payoffs changing from round to round. From the subjects' psychometric scores and game behaviors we inferred the relationship between reciprocal preferences, belief biases, and personality. The results confirmed the hypotheses of the model.

Abstract: The main aim of this article is to investigate the behavioral consequences of the provision of subject-specific information in the group effort levels chosen by players in an experimental CPR game. We examine two basic treatments, one with incomplete information and the other with complete information. In the former, subjects are informed only about their own individual payoffs and the aggregate extraction effort level of the group, and in the latter they are also informed about the individual effort levels and payoffs of each subject. Given this setting, the basic question we attempt to answer is: Will the provision of subject-specific performance information (i.e. individual's effort levels and payoffs) improve or worsen the tragedy of the commons (i.e. an exploitation effort level greater than the socially optimum level)? In order to motivate our hypotheses and explain our experimental results at the individual level, we make use of the theory of learning in games, which goes beyond standard non-cooperative game theory, allowing us to explore the three basic benchmarks in the commons context: Nash equilibrium, Pareto efficient, and open access outcomes. We use several learning and imitation theoretical models that are based on contrasting assumptions about the level of rationality and the information available to subjects, namely: best response, imitate the average, mix of best response and imitate the average, imitate the best and follow the exemplary learning rules. Finally, in order to econometrically test the hypotheses formulated from the theoretical predictions we use a random-effects model to assess the explanatory power of the different selected behavioral learning and imitation rules. (C) 2010 Elsevier B.V. All rights reserved.