An Analysis of the Three Signal Sir Phillip Sidney Game

An overly simplistic view of evolution would say that it consists only of competition between individuals to survive. However, in actuality ecosystems are often characterized by partial common interest, that is at least some of the time it is in individuals’ best interest to cooperate. Most obviously this occurs in the case of close kin, who share a large portion of common genes and thus will be at least partially successful at passing on their genes to the next generation should their actions ensure the survival of their kin at their own expense. Less obvious but still worth mentioning is that partial common interest can arise between species, even ones with an antagonistic relationship. Consider a predator species A and its prey species B. Members of A can only catch the weaker members of B, if they attempt to catch a strong member of B both will expend resources in the chase and A will get no dinner from it. This is an outcome that neither the strong member of B nor the member of A would like, and so it is in their best interest to develop some way in which the members of B can indicate if they are strong. However, weak members of B who will be eaten if they are chased, have it in their best interest to mimic the “strong signal.” Thus there is only partial common interest, for some individuals it is best to cooperate with the enemy and for others it is best to deceive them.