The Economist reports that anonymous benevolence makes people feel good . Researchers at the National Institute of Neurological Disorders and Stroke in Bethesda, Maryland used MRI to explore the neurological basis of charity .
They found that a variety of brain centers were involved. Donating money activated the brain center associated with sex, money, food and drugs – the mesolimbic pathway, mediated by dopamine. The warm glow of giving is the same as some other warm glows. Donating also engaged the part of the brain that plays a role in the bonding behaviour between mother and child, mediated by the hormone oxytocin.
Making complex trade-offs where self-interest and moral obligations conflict activated yet a third part of the brain, the anterior prefrontal cortex, which is thought to be unique to humans. It seems that giving makes many animals feel good, but grappling with ethical dilemmas seems to be part of what makes us human.
 The joy of giving, Economist, 14 October 2004, at http://www.economist.com/science/displaystory.cfm?story_id=E1_RDNPPDS (subscription may be required)
 Jorge Moll, Frank Krueger, Roland Zahn, Matteo Pardini, Ricardo de Oliveira-Souza, and Jordan Grafman, “Human fronto–mesolimbic networks guide decisions about charitable donation,” PNAS 2006 103: 15623-15628, at http://www.pnas.org/cgi/content/full/103/42/15623.