RECIPROCITY AND COMMUNICATION OF PARTNER QUALITY

In a cooperative exchange, the size of a partner's contribution is lik ely to depend both on the partner's ability to supply help and on the partner's need for help in return. Referring to such needs and abiliti es as aspects of partner quality, it follows that variation in the amo unt of help offered in a relationship could transmit information about partner quality. A plausible behaviour might then be to vary the inve stment in a partner according to available information about partner q uality and to invest little in a partner who offers little in return. Thus, regulation of a relationship through communication of partner qu ality would tend to follow the principle of reciprocity. In an analysi s of an iterated game where players have private information about the ir needs and abilities, I verify this possibility by describing an evo lutionarily stable state space strategy, referred to as 'state-depende nt reciprocity', entailing communication of partner quality. Although the evolution of cooperation has been studied in great detail, there h as been no previous analysis of communication of needs and abilities i n a relationship. It may well be that such communication is of major i mportance for the evolution of cooperative behaviour in nature.