For centuries, a bedrock economic, legal, and social assumption was that people were inherently so selfish that they could not be expected to support or aid others not in their own genetic line. Now the study of human behavior reinforces the neglected fact that we are hardwired equally to be cooperative. As social psychologist Dacher Keltner writes in Born to Be Good, humans could not have survived and evolved without the social organization that only cooperation, mutuality, and reciprocity make possible. In fact, we are so tilted toward cooperation that we punish non-cooperators in our communities, even at cost to ourselves. This “strong reciprocation” strategy reflects a deep recognition, made instinctual through millennia of group activity, that all behavior is contagious, and that rewarding good with good and bad with punishment is the best way to protect our societies and therefore ourselves. Reciprocity makes compassion not a form of weakness but a model of strength; it makes pro-social morality not just moral but natural and smart.

Liu, Eric; Hanauer, Nick (2011-12-06). The Gardens of Democracy: A New American Story of Citizenship, the Economy, and the Role of Government (Kindle Locations 371-378). Perseus Books Group. Kindle Edition.