Egg-trading in simultaneous hermaphrodites: an alternative to Tit-for-Tat

Reciprocal Altruism or reciprocity occurs when an individual performs a costly act for the benefit of another individual in anticipation of receiving beneficence via a costly act in return (Trivers 1971, Connor 1986, Rothstein and Pierotti 1988). Thus the key defining feature of reciprocity is that in any given exchange an individual would do better by, in the absence of punishment, not reciprocating. Connor (1986) introduced the term ‘pseudo-reciprocity’ for a widespread phenomenon that had often been interpreted as reciprocity. Organisms often engage in activities which benefit themselves but which also incidentally benefit conspecifics or members of different species. In the pseudo-reciprocity paradigm, and individual A performs a beneficent act for an individual B in order to increase the probability of receiving incidental benefits from B. Because the return benefits to A derive from behaviors B performs to benefit B, there is no cheating in pseudoreciprocity. Here I will describe a mechanism in which two individuals may exchange benefits by parcelling those benefits to manipulate each other’s optimal strategy. The resulting exchange of beneficence is similar to reciprocity in that an individual A performs a costly act for another individual B in anticipation of B performing a costly act for A in return. However, in reciprocity, an individual would realize short-term benefits by cheating on any given interaction. This is not the case in the model presented here.