July 16, 2007 — A new study on our closest living relatives, chimpanzees, found the animals might enact revenge under certain circumstances, but never with spite.
The finding, published in the latest Proceedings of the National Academy of Science, suggests homo sapiens are the only known species that sometimes feel a need to see others suffer.
For chimps, on the other hand, the message is, "Don't mess with my lunch, or else."
Researchers Keith Jensen, Josep Call and Michael Tomasello of the Max Planck Institute for Evolutionary Anthropology in Germany devised experiments where 13 chimps could pull a string attached to a table, causing the table to collapse and fall to the ground. The primates had no trouble doing this, and quickly learned not to pull the string when they were eating food that was resting on the table.
A few study phases tested the general frustration of chimps, since the scientists would allow one chimp to dine in front of another. The onlooker could not reach the food, yet could pull the string. In another version of this test, a person would grab food from one eating, potentially string-pulling chimp and then give the food to another in full view.
The only situation that repeatedly caused the chimps to collapse the table was when a chimpanzee would blatantly steal food from the other. The victim would then pull the string, but without pleasure.
"The chimpanzees who collapsed the table were often angry and would continue to threaten the thief," lead author Jensen told Discovery News. "If they had the chance, and they were dominant, they would likely have beaten up the other chimpanzee."
The chimps did not seem to hold a lasting grudge, however.
Jensen said "when the test was done and the subjects were allowed to be with the rest of the group, there appeared to be no consequences for either individual."
The researchers believe punishment — in this case disrupting lunch — can benefit social groups in the long run, since it may discourage selfish behavior and help prevent "the degrading influence of free-riders."
Spite, on the other hand, is not always a means to an end, but rather is an end in itself.
A sneaky human, for example, might hide and pull on the string just to enjoy seeing the table collapse underneath someone else whose lunch was on the table.
