A new study conducted by researchers at Yale University has discovered that not only will monkeys make the effort to punish other monkeys that get more food than them, they also have the ability to act spiteful just like humans. In the study, the team examined capuchin monkeys and found that they will pull on a rope that stimulates the collapse of a table holding another monkey's food. Although chimpanzees, which are apes, will only participate in this behavior after direct personal confrontations such as theft, capuchins will do so even in cases where another monkey simply received more food.
"One hallmark of the human species is the fact that we're willing to make a special effort to punish those who violate social norms," Laurie Santos, senior author of the study, said in a press release. "We punish those who take resources unfairly and those who intend to do mean things to others. Many researchers have wondered whether this motivation is unique to our species."
Santos and her team wanted to examine a distantly related primate species to determine if they would punish others that received socially unequal rewards and found that they acted more spitefully than chimpanzees.
"Our study provides the first evidence of a non-human primate choosing to punish others simply because they have more," said Kristen Leimgruber, first author of the paper. "This sort of 'if I can't have it, no one can' response is consistent with psychological spite, a behavior previously believed unique to humans."
"Our findings suggest that the psychological roots of human-like punishment motivations may extend deeper into our evolutionary history than previously thought," Santos said.
The findings were published in the Dec. 15 issue of Evolution and Human Behavior.
