Actions taken by an individual organism at its cost for the benefit of another are generally defined as altruistic. Examples of altruistic acts include that of vampire bats that regurgitate blood for other group members to feed on, birds that help, protect, and feed the fledglings of other flocks, and Vervet monkeys that risk their lives to warn pack members of danger. From the standpoint of evolutionary theory, altruism is rather puzzling: one would expect organisms to increase their own chances of survival and reproduction, not those of others. From an economist’s standpoint, altruism seems incoherent with the laws of classical game theory: we would expect organisms to play their dominant strategy and arrive at one of the Nash equilibria.

Altruism can be illustrated as a Hawk-Dove game, where the players can choose either to be altruistic or selfish. When both players act selfishly and uncooperatively, the payoffs are very low (essentially close to zero) because they must allocate resources to fend themselves from members of their own species. When one player acts selfishly, he benefits from his partner’s altruism and receives the entire payoff. When both players act altruistically, they obtain the highest combined payoff because they are now able to act as a unit and acquire resources more efficiently; however, each individual is worse off than he would be if he chose to be selfish while his partner chose to be altruistic. A sample payoff matrix for this game would look like the following:

In this game, both organisms have as their dominant strategies being selfish, and thus, the two Nash equilibria being at (25, 0) and (0, 25), we would not expect organisms to exhibit altruistic behavior in nature.

In order to address this dilemma, researchers have constructed alternative game scenarios. According to them, the altruism demonstrated in our game above is a form of “strong altruism” that rarely occurs in nature. Instead, most altruistic acts performed in nature are varieties of “weak altruism” that have positive externalities. For example, an organism’s tending the fledglings of its fellow species, has the positive externality of boosting the chances of the altruistic organism’s genetic material of surviving into the next generation (if only a fraction of it). Furthermore, many altruistic acts are reciprocal. For example, altruistic vampire bats and Vervet monkeys get rewarded with altruism in turn. Thus, the altruist in nature displays weak altruism: he is not necessarily reducing his absolute fitness; rather, he is reducing his relative fitness to the recipient.

Because of these “unrealized” gains, a more accurate scenario for altruism would look like this:

In this case, the Nash Equilibrium occurs when both organisms behave altruistically, which is also the socially optimal choice. The results are very different from the strong altruist game; the unrealized gains change the weak altruist’s payoffs completely, resulting in a different Nash equilibrium.

This article relates directly with what we’ve learned in class - how games can be used to predict behaviors in humans and animals. Altruism, once properly understood, also shows the potential of being explained through game theory.

http://plato.stanford.edu/entries/altruism-biological/

http://www.sciencedaily.com/releases/2008/04/080428094212.htm