ehavioral economists employ an experimental procedure called the Ultimatum Game. It goes something like this. You are given $100 to split between yourself and your game partner. Whatever division of the money you propose, if your partner accepts it, you are both richer by that amount. How much should you offer? Why not suggest a $90–$10 split? If your game partner is a rational, self-interested money maximizer, he isn’t going to turn down a free 10 bucks, is he? He is. Research shows that proposals that deviate much beyond a $70–$30 split are usually rejected. Why? Because they aren’t fair. Says who? Says the moral emotion of “reciprocal altruism,” which evolved over the Paleolithic eons to demand fairness on the part of our potential exchange partners. “I’ll scratch your back if you’ll scratch mine” only works if I know you will respond with something approaching parity. The moral sense of fairness is hardwired into our brains and is an emotion shared by most people and primates tested for it. Thousands of experimental trials with subjects from Western countries have consistently revealed a sense of injustice at low-ball offers. Further, we now have a sizable body of data from peoples in non-Western cultures around the world, including those living close to how our Paleolithic ancestors lived, and although their responses vary more than those of modern peoples living in market economies do, they still show a strong aversion to unfairness. - www.scientificamerican.com