Cooperators, Competitors, and Response to GRIT

Eighty-seven subjects were classified as cooperators and competitors. They then participated in a 30-trial Prisoner's Dilemma situation with a simulated other who, after 10 trials of 50% cooperation, followed one of three strategies during the next 10 trials: GRIT, tit-for-tat, or 100% cooperation. As predicted, competitors as well as cooperators responded cooperatively only to the GRIT strategy. During the final 10 trials, which were 100% cooperative in all three conditions, the cooperators were somewhat more cooperative than the competitors. In postexperimental ratings, competitors estimated people in general to be more competitive and untruthful than did cooperators. They also rated themselves as more competitive than did cooperators.