http://www.nytimes.com/2010/07/23/opinion/23brooks.html?_r=2&th&emc=th
“people have a rudimentary sense of justice from a very early age. This doesn’t make people naturally good. If you give a 3-year-old two pieces of candy and ask him if he wants to share one of them, he will almost certainly say no. It’s not until age 7 or 8 that even half the children are willing to share. But it does mean that social norms fall upon prepared ground. We come equipped to learn fairness and other virtues. “