Axelrod came up with four rules to establish cooperation. First, do not be envious. Be satisfied with absolute rather than relative gains, so that if you are doing nicely, do not worry is someone is doing even better. Second, do not be the first to defect, because you need to establish the logic of cooperation. Third, if another player defects, reciprocate in order to establish confidence in your retaliation. Last, do not be too clever, as others will not be sure what you are up to.
