Competitive altruism

Competitive altruism is a possible mechanism for the persistence of cooperative behaviors, specifically those that are performed unconditionally. The theory of reciprocal altruism can be used to explain behaviors that are performed by a donor who receives some sort of benefit in the future. When no such compensation is received, however, reciprocity fails to explain altruistic behavior.

To explain competitive altruism, Roberts uses the example of preening among birds. Because certain birds cannot reach parasites on all parts of their bodies, particularly their necks, they benefit from preening one another. For any given bird, there is an entire flock of potential preeners, who compete in hopes of establishing a beneficial relationship. Cheaters, or those birds that try to be preened without preening others, do not compete and thus are excluded from these relationships. Their fitness is lowered because they are ostracized by members of the flock.

McNamara et al. quantitatively analyzed this theory. Like Robert Axelrod, they created a computer program to simulate repeated interactions among individuals. The program involved players with two genetically determined traits, a ‘cooperative trait’ and a ‘choosiness trait.’ They found the following results:

‘Paradoxical’ trait combinations yield particularly low payoffs: individuals with low choosiness but high effort tend to get exploited by their co-players; individuals with high choosiness but low effort waste their time searching for better co-players, which are, however, unlikely to accept them. The positive correlation between choosiness and cooperativeness leads to a positive assortment between cooperative types – an essential feature of all mechanisms that promote cooperation.

The development of such cooperation requires variation in the degree of cooperation and choosiness, which the researchers attributed to genetic mutation and variation. McNamara et al. also determined that since a period of searching is required for ‘mutually acceptable’ players to find one another, competitive altruism is more likely to arise in animals with long life spans.

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