The Buzz of Altruism
The Economist summarizes some research published in the Proceedings of the National Academy of Sciences:
Researchers at the National Institute of Neurological Disorders and Stroke in Bethesda, Maryland, wanted to find the neural basis for unselfish acts. They decided to peek into the brains of 19 volunteers who were choosing whether to give money to charity, or keep it for themselves. To do so, they used a standard technique called functional magnetic resonance imaging, which can map the activity of the various parts of the brain….
…the researchers were able to examine what went on inside each person’s head as they made decisions based on moral beliefs. They found that  the part of the brain that was active when a person donated happened to be the brain’s reward centre—the mesolimbic pathway, to give it its proper name—responsible for doling out the dopamine-mediated euphoria associated with sex, money, food and drugs. Thus the warm glow that accompanies charitable giving has a physiological basis.
But it seems there is more to altruism. Donating also engaged the part of the brain that plays a role in the bonding behaviour between mother and child, and in romantic love. This involves oxytocin, a hormone that increases trust and co-operation.
When subjects opposed a cause,  the part of the brain right next to it was active. This area is thought to be responsible for decisions involving punishment.
And  a third part of the brain, an area called the anterior prefrontal cortex—which lies just behind the forehead, evolved relatively recently and is thought to be unique to humans—was involved in the complex, costly decisions when self-interest and moral beliefs were in conflict.