Altruism refers to behaviors that are performed for the sake of benefiting others at a cost to oneself. Reciprocal altruism is when altruistic behaviors are performed because they increase the likelihood of repayment in the future. For quite some time the presence of altruistic behaviors in animals and humans was a genuine puzzle for the Darwinian account of evolution through natural selection. It seemed impossible for an organism that acts unselfishly for the sake of another (non-related) organism to benefit in any way that would encourage that organism’s reproductive success. This is simply because selfish (non-altruistic) individuals would on average have more resources than altruistic individuals. After many generations, natural selection seemed to dictate that any genetic basis for altruistic behavior should be eliminated from a population. The theory of reciprocal altruism was first described by the evolutionary biologist, Robert Trivers, as a solution to the problem of how altruistic behaviors directed toward nonkin could have emerged through natural selection.
Trivers’s insight was that often an individual could act in such a manner (e.g., by sharing food) as to increase its chance of survival if it could depend on similar altruistic behavior from another individual at some point in the future. For the strategy of reciprocal altruism to work, however, a few conditions must be met: Individuals must interact more than once (so that the opportunity to be repaid can arise), individuals must be able to recognize other individuals reliably, and individuals must be able to remember the past behavior of those with whom it interacts. Because of these constraints, reciprocal altruism is less common than is kin-directed altruism, where individuals act for the good of individuals who share their genes.
Reciprocal altruism is often discussed in the context of game theory, particularly the Prisoner’s Dilemma Game. This Prisoner’s Dilemma provides an elegant way to test cooperative behavior in the simplified context of a game. An influential analysis by the political scientist Robert Axelrod and the evolutionary biologist William Hamilton demonstrated that in this game, in which two isolated “prisoners” must decide whether to “cooperate” and refuse to confess, or to “defect” and confess for a lesser sentence, the most effective strategy (submitted by the mathematical psychologist Anatol Rapoport)—that is, the strategy with the best payoff across repeated interactions—was a tit-for-tat strategy—a strategy that repays in kind. If your partner cooperates, you return the favor. If he or she cheats, you do the same. Because this strategy is essentially reciprocal altruism, Axelrod and Hamilton’s analysis was able to demonstrate that evolution could easily have selected for genes that might encourage such altruistic behavior.
It is often remarked that reciprocal altruism is not genuine altruism because it has the seemingly selfish goals of repayment, whereas true altruism is usually defined as self-sacrifice for the sole sake of benefiting others. The fact that altruistic behaviors could emerge through natural selection via the mechanism of reciprocal altruism, however, says nothing about the motives of the organism engaged in the altruistic act. It is important to recognize that reciprocal altruism is a theory of how cooperation could have evolved, not a theory of the psychological states of the altruist.
- Pizarro, D. (2000). Nothing more than feelings? The role of emotions in moral judgment. Journal for the Theory of Social Behaviour, 30, 355-375.
- Trivers, R. (1971). The evolution of reciprocal altruism. Quarterly Review of Biology, 46, 35-37.