is that it is common.
In this months (feb. 08) issue of Scientific American, Michael Shermer makes the argument that free trade is essentially fair trade because most trading is not based on greed but on an instinctive sense of right & wrong and good & bad.
Sheremer writes every month a column labelled "Skeptic." His column usually applies a scientific eye to issues like homeopathy, economic, polotics, a wide variety of issues where science trumps common sense.
In this month's column he brings a few examples to make his argument. One example is that if you take two people and tell one that he can get up to $100 if person B lets him have that amount or he can negotiate with person B. And they found that when person B is offered $10 leaving $90 for person A that the guy feels ripped off and doesn't agree. The split usually ends up at $70-$30. Shermer deduces that because the guy feels cheated, even though he would have recieved a free $10, but he needs some level of parity to assuage his moral outrage.
The same he says is true of primates. In tests primates that scratch each other back for a treat will preform about 90% of the time, unless one primate gets a better treat than the other. When one primate got a grape instead of a cucumber slice the rate dropped to 60%. When he got anouther grape the primate threw his cucumber slice at the human.
Shermer argues that the innate need for parity is based on good, on the idea of fairness.
All the test subjects were predators. These tests do not work on Prey members of the animal kingdom. The need to acheive parity is not based on good it is based on dominance. The human might not have the free $10 but he has the power to prevent the other guy from getting his $100. And he excercises that power and leverage to recieve $30. The primate excercises his leverage to prevent the other from getting any more grapes unless he gets grapes as well.
If these predators could make the rewards weigh in their favor they would. They only have enough leverage to argue for something close to parity; not our of goodness or fairness; from predatory struggle of dominance.