Proceedings of the National Academy of Sciences of the United States of America
Punishment of free-riding has been implicated in the evolution of cooperation in humans, and yet mechanisms for punishment avoidance remain largely uninvestigated. Individual variation in these mechanisms may stem from variation in the serotonergic system, which modulates processing of aversive stimuli. Functional serotonin gene variants have been associated with variation in the processing of aversive stimuli and widely studied as risk factors for psychiatric disorders.
A multi-armed bandit problem is a search problem on which a learning agent must select the optimal arm among multiple slot machines generating random rewards. UCB algorithm is one of the most popular methods to solve multi-armed bandit problems. It achieves logarithmic regret performance by coordinating balance between exploration and exploitation. Since UCB algorithms, researchers have empirically known that optimistic value functions exhibit good performance in multi-armed bandit problems.
The iterated Prisoner's Dilemma has become the standard model for the evolution of cooperative behavior within a community of egoistic agents, frequently cited for implications in both sociology and biology. Due primarily to the work of Axelrod (1980a, 1980b, 1984, 1985), a strategy of tit for tat (TFT) has established a reputation as being particularly robust.
Cooperation among genetically unrelated individuals is commonly explained by the potential for future reciprocity or by the risk of being punished by group members. However, unconditional altruism is more difficult to explain. We demonstrate that unconditional altruism can evolve as a costly signal of individual quality (i.e. a handicap) as a consequence of reciprocal altruism.
If someone is nice to you, you feel good and may be inclined to be nice to somebody else. This every day experience is borne out by experimental games: the recipients of an act of kindness are more likely to help in turn, even if the person who benefits from their generosity is somebody else. This behaviour, which has been called 'upstream reciprocity', appears to be a misdirected act of gratitude: you help somebody because somebody else has helped you. Does this make any sense from an evolutionary or a game theoretic perspective?
The evolution of cooperation has been a major challenge in evolutionary biology. Unconditional cooperators who help others at a cost to themselves are exploited by defectors who enjoy the benefits without any help in return. It has been argued that cooperation can be established in repeated dyadic interactions if cooperators punish defectors by withholding future cooperation. In social interactions involving more than two individuals, however, withholding future cooperation may result in penalizing not only defectors but also other cooperators.
We analyse generosity, second-party ('spiteful') punishment (2PP), and third-party ('altruistic') punishment (3PP) in a cross-cultural experimental economics project. We show that smaller societies are less generous in the Dictator Game but no less prone to 2PP in the Ultimatum Game. We might assume people everywhere would be more willing to punish someone who hurt them directly (2PP) than someone who hurt an anonymous third person (3PP). While this is true of small societies, people in large societies are actually more likely to engage in 3PP than 2PP.
By applying a technique previously developed to study ecosystem assembly [Capit·n et al., Phys. Rev. Lett. 103, 168101 (2009)] we study the evolutionary stable strategies of iterated 2 ◊ 2 games. We focus on memory-one strategies, whose probability to play a given action depends on the actions of both players in the previous time step. We find the asymptotically stable populations resulting from all possible invasions of any known stable population. The results of this invasion process are interpreted as transitions between different populations that occur with a certain probability.
When people are the victims of greed or recipients of generosity, their first impulse is often to pay back that behavior in kind. What happens when people cannot reciprocate, but instead have the chance to be cruel or kind to someone entirely different--to pay it forward? In 5 experiments, participants received greedy, equal, or generous divisions of money or labor from an anonymous person and then divided additional resources with a new anonymous person. While equal treatment was paid forward in kind, greed was paid forward more than generosity.
Humans are often generous, even towards strangers encountered by chance and even in the absence of any explicit information suggesting they will meet again. Because game theoretic analyses typically conclude that a psychology designed for direct reciprocity should defect in such situations, many have concluded that alternative explanations for human generosity--explanations beyond direct reciprocity--are necessary.