Why do most of us work together for the common good, even when it might personally benefit us more to cheat? Is it because we fear we would be punished for not following the rules? Because we have been taught to treat others as we would want to be treated?
Because cooperation is vital for survival in a variety of contexts, it may be that fair play is an evolutionary adaptive behavior, scientists say. Of course, the flip side is that when an individual does behave selfishly, others often use some form of negative reinforcement to dissuade such behavior in the future.
It appears animals do the same. First, though, an animal must recognize unfair situations. To find out if primates can do so, Dr. Sarah F. Brosnan of Georgia State University and her colleagues set up a series of experiments in which pairs of primates were trained to perform the same task, but one received a much tastier reward. Brosnan discovered that they do realize (and respond negatively) when another primate receives a "better" reward for completing the same task. Even when they get the same reward they did before (in the control situation) that they were happy with, the animals will not be satisfied "if a partner gets a better deal," Brosnan and Dr. Frans B. M. de Waal say in their article. Primates "clearly have to be able to assess quantities or qualities and compare them, so there is a baseline level of cognition which is required," said Brosnan.
Sometimes, certain primates will refuse food rewards that they deem insufficient. Like petulant children, primates have been known to toss the reward from the test chamber. "When I began the research, I never expected to see individuals refusing food rewards," Brosnan said.
So, what about the other animal, the one that who received more food? Even though they were better rewarded, these chimpanzees refused to participate more often than when the food was distributed more fairly. Is this due to a sense of justice? Or just a desire to avoid retaliation (in other words, punishment) from their partner chimp after the experimenter leaves?
In a similar study using dogs as subjects, when two dogs performed the same task and one dog received a reward when the other didn't, the "slighted" dog recognized the unfair treatment and began to refuse to obey the experimenter. However, unlike the primates, the dogs did not seem to notice when the other dog received a larger or better reward, as long as they both received something.
Although we might expect it of our primate relatives, and even dogs who spend so much time with humans, it seems humble fish also recognize when they're being cheated. Cleaner fish, as the name implies, remove dead skin, parasites, and other bits of junk on larger "client" fish. However, the fish tend to prefer the healthy scales and mucus to the dead cells, so they will sometimes "cheat" and bite the body itself of the client fish. Naturally, these bites often cause the client to swim away, thus depriving the cleaner fish (and their cleaning partners) of a meal.
Image courtesy of João Paulo Krajewski.
Raihani and her colleagues tested the fish in the laboratory to simulate conditions in the ocean. To represent client fish, they prepared a plate of food with both fish flakes (which cleaner fish like okay) and prawns (which the fish love). A low-value plate had four fish flakes while high-value ones had eight. The experimenters put a plate of food in front of each pair of cleaner fish (one male, one female). They were allowed to eat as many of the fish flakes as they liked, but as soon as one of them ate a prawn, the plate of food was removed (to simulate the client fish swimming away). The researchers then measured the level of punishment (aggressive chasing) that the male doled out to his partner.