We study how intelligence and personality affect the outcomes of groups, focusing on repeated interactions that provide the opportunity for profitable cooperation. Our experimental method creates two groups of subjects who have different levels of certain traits, such as higher or lower levels of Intelligence, Conscientiousness, and Agreeableness, but who are very similar otherwise. Intelligence has a large and positive long-run effect on cooperative behavior. The effect is strong when at the equilibrium of the repeated game there is a trade-off between short-run gains and long-run losses. Conscientiousness and Agreeableness have a natural, significant but transitory effect on cooperation rates.
That is by Eugenio Proto, Aldo Rustichini, and Andis Sofianos, forthcoming in the JPE. Note that agreeable people do cooperate more at first, but they don’t have the strategic ability and consistency of the higher IQ individuals in these games. Conscientiousness has multiple features, one of which is caution, and that deters cooperation, since the cautious are afraid of being taken advantage of. So, at least in these settings, high IQ really is the better predictor of cooperativeness, especially over longer-term horizons.