Role Of Optimist On Emergence Of Cooperation In Demographic Multi-Attribute Donor-Recipient Game

We consider an interaction between a donor and a recipient where the actions of a donor produce multiple results to the recipient. There are Optimists and Pessimists who focus on the best and worst outcomes among them as a recipient of the interaction, respectively, and they try to reflect on their experience in their next action as a donor. What is the effect on the emergence of cooperation? This paper formulates the situation as a Demographic Multi-attribute DonorRecipient game and introduces also Average, who focuses on the average outcome and considers the effect of the initial distribution of them on the emergence of cooperation by Agent-Based Simulation. If the initial population includes only one type from Pessimist, Optimist, or Average, then the emergence rate of cooperation increases in this order. In particular it is very low with only the Pessimist. The emergence rate of cooperation in case of initial populations including both Optimist and Pessimist is larger than that of the initial population including only the Optimist. Thus the Optimist is crucial for a high emergence rate of cooperation in realistic initial populations including the Pessimist.