Prosocial games played with nonhuman primates.

Studies differ with regard to payoff distribution, and whether help is costly. Included are studies only in which subjects have to choose between physically presented payoff distributions by pulling an apparatus within reach.
Ref.: 1Silk et al. 2005, 2Jensen et al. 2006, 3Vonk et al. 2008, 4Burkart et al. 2007, 5Lakshminarayanan and Santos 2008, 6Takimoto et al. 2010, 7Cronin et al. 2009, 8Stevens 2010, 9Massen et al. 2010.
areward written in „()“ goes to an empty compartment and is therefore out of reach for both subjects.
bdonor is allowed to choose both distributions during one trial.
c1 = favored reward; 1 = less favored reward; 1 = non-favored reward.
dtested one-tailed t-test; but not statistically significant if tested two-tailed like other studies did.
eyes for subdominant recipient, no for dominant recipient; no for subdominant if invisible, neg. for dominant if invisible.
fyes for kin partner; no for non-kin partner; under both conditions prosocial tendency declined with increasing rank number.