The effect of an initial cooperative or competitive treatment upon a subject's response to conditional cooperation

Subjects, 112 male and 112 female college students, participated in four experiments with mixed-motive games, using a Prisoner's Dilemma and a Chicken matrix. A prearranged program simulating the “other player” made 30 consecutive cooperative or competitive choices during a “pretreatment” and then, for 200 trials, reciprocated the S's choices with a one-trial lag (the tit-for-tat treatment). A highly significant increase in cooperative behavior was observed in all four experiments. The data suggest that either type of pretreatment may facilitate the development of a cooperative strategy, if followed by a tit-for-tat treatment, while in the absence of pretreatment, no increase in cooperative behavior was found. The sex of S and the effect of the first move of tit-for-tat treatinent interacted with other experimental conditions. Cooperative pretreatment, followed by a cooperative first move, produced one of the highest levels of cooperation observed in these experiments.