Evolution of Conditional Strategies in Asynchronous Prisoners Dilemma (with L. Andreozzi and M.Ploner)

Abstract

We aim to investigate the evolution of simple conditional response strategies in a cooperative environment. We start by defining properties of response function types in a general theoretical framework. Then we analyze the evolutionary stability of response strategies in a mixed population by using simulations based on an extended repeated prisoners dilemma game. Aligned with game theoretical literature our results confirm that the pure selfish type is likely to dominate the population when the discount factor is sufficiently low while two distinct conditional cooperator types are most likely types to survive when repetition probability is sufficiently high. However, our result show that, being a counter intuitive strategy, a particular hump-shaped response strategy is the most successful conditional strategy in the population for some mediate values of discount factor. Our result provide an intuition to explain the consistent existence of hump shaped responses obvesred in several experimental studies.

The Stability of Reciprocity: Egoism trumps Reciprocal Cooperation in Social Dilemmas (with L. Andreozzi and M.Ploner)

Abstract

An often replicated result in the literature on social dilemmas is that a large share of the subjects reveal conditionally cooperative preferences. Cooperation generated by this type of preferences is notoriously unstable, as individuals reduce their contributions to the public good in reaction to other subjects' free riding. This has lead to the widely shared conclusion that the cooperation observed in experiments (and its collapse) is mostly driven by imperfect reciprocity. In this study, we explore the possibility that reciprocally cooperative preferences may themselves be unstable. We do so by observing the evolution of subjects' preferences in a standard, anonymously repeated social dilemma. Our unsettling result is that, in the course of the experiment, a significant fraction of reciprocally cooperative subjects become egoistic, while the opposite transition is never observed. The non-selfish preferences that appear to be more stable are those most easily attributed to confusion. We are thus driven to the conclusion that egoism is more resistant to exposure to social dilemmas than reciprocity.

Reciprocity in Dictator Games: an Experimental Investigation (with L. Andreozzi and M.Faillo)

Abstract

The Dictator Game has been for a long time considered the sharpest tool to isolate pure altruism from reciprocity. However several criticisms were raised to this approach. First, there is the issue of their external validity: Giving money to randomly chosen strangers seems to be absent among the repertoire of human behavior. Second, experimental evidence has consistently shown that innocuous manipulations of the experimental framework change dramatically subjects’ decision, in ways that are incompatible with rational choice. We argue that positive giving in Dictator Games can be best understood as a form of reciprocal altruism: A subject’s decision to donate when in the Dictator’s position might stem from his implicit belief that the recipient would have donated as well if the roles were reversed. To test this hypothesis, we conducted three experiments: (i) Dictator game, (ii) A reframed dictator game known as “Bully Game” (Krupka & Weber, 2008), and (iii) Dictator Game in which subjects are matched with members of Achioli ethnic group located in Northern Uganda. In each pair, a subject is assigned to the role of dictator and the other to the role of responder. Before that, we used strategy method to collect subjects’ unconditional transfer decisions and transfer decisions conditioned to their opponents’ unconditional transfer decisions. Our main result rejects unconditional altruism hypothesis: In all treatments, majority of the subjects are conditional altruists although, on average, transfers in Achioli treatment are higher. We also confirm that simple framing can manipulate behavior in the dictator game considerably.