What's more interesting is that the study found that monkeys have consciences as well as the rudimentary ability to remember obligations.
"There is enough evidence for the following of social rules to agree that some of the stepping stones towards human morality can be found in other animals," lead researcher Prof Frans de Waal of Emory University in Georgia said.
The researchers came to the conclusion after carrying out experiments on monkeys and apes to see if they understood the idea of fairness. The animals were asked to perform a set of simple tasks and then rewarded with food or affection.
The study found that the animals had an acute sense of fairness and objected strongly when others were rewarded more than themselves for the same task, often sulking and refusing to take part any further, The Sunday Times reported.
Another experiment looked at altruism in chimps -- it found they were often willing to help others even when there was no obvious reward. "Chimpanzees spontaneously help both humans and each other in carefully controlled tests," he said.
"Everything else being equal, they prefer to reward a companion together with themselves rather than just themselves -- the research suggests that giving is self-rewarding for monkeys," De Waal said.