Average player traits as predictors of cooperation in a repeated prisoner's dilemma

Many studies have looked at how individual player traits influence individual choice in the repeated prisoner's dilemma, but few studies have looked at how the average traits of pairs of players influence the average choices of pairs. We consider cognitive ability, patience, risk tolerance, and the Big Five personality measures as predictors of individual and average group choices in a 10-round repeated prisoner's dilemma. We find that a pair's average cognitive ability measured by Raven's cognitive ability test predicts average cooperation rates robustly and average earnings more modestly. Openness predicts both greater joint cooperation and the use of reciprocity to sustain cooperation.