There has been a vivid debate on whether we humanize the animals too much or not, by associating certain "typically human feelings" with them. But scientific experiments revealed that animals too, and apes even more, experience sophisticated emotions, from joy to sadness, and communicate employing language. Still one thing seems to remain ours: spite.

A team led by Keith Jensen at the Max Planck Institute for Evolutionary Anthropology at Leipzig, Germany, made experiments with our closest relatives, the chimpanzees, in which they placed a food-laden table in front of a caged ape. The table had attached a string the chimp could pull to collapse the table.

The chimp did not pull the string as long as it could reach the food. But when the food was placed to the opposite side of the table, the frustrated chimp pulled the string in 30% of the trials.

In a second test, the scientists placed a second chimp in a cage located at the opposite side of the table. When replacing the food on the table, the second chimp benefited from this. If the first chimp had been spiteful, it could have simply pulled the table, impeding its rival from feeding. But the chimps displayed the same level of frustration as in the previous approach, collapsing the food just in 30% of the time. Only when the second chimp tried to move the food closer to itself, by pulling a string of its own, the first chimp displayed anger, pulling the string in 50% of the time.

"Spite is a common human reaction. Imagine you're a kid at a birthday party. The mother gives you cake, then takes it away and gives it to another kid. It's not his fault, but you'll still be annoyed with him because of his good fortune. But chimps don't care who's got the cake, just who took it from them," said Jensen.

It appears that chimps do not perceive things from another's point of view.

"And if a chimp's lack of empathy leaves it unable to feel spite, it may also fail to behave altruistically. There have been experiments that gave chimps the chance to be nice to another at no cost to themselves, but they weren't interested. They didn't have a human propensity to be nice," said behavioral ecologist Rufus Johnstone of the University of Cambridge in the UK.

"Many differences obviously remain. Humans actually care about outcomes affecting others. The good side of that is altruism. Spite is the evil twin that can't be separated from it.", Jensen said.