From our June 2003 issue.
Altruism, while rare in the animal kingdom, shows up in humans as young as age two — something of a biological mystery. But now brain scientists at Emory University are beginning to understand why people happily do good for others, sometimes at their own expense. It turns out that our altruistic drive to cooperate is connected to one of the brain's great pleasure centers. Choosing to be cooperative rather than greedy lights up the brain with joy.
The data, published in Neuron, July 18,2002, come from a study of 18 pairs of women who played a version of the classic game "Prisoner's Dilemma" while one of the pair was inside a brain-imaging scanner. The game is complex, but in a nutshell, it challenges each player to either cooperate with, or betray, the other.
What proved fascinating was the brain activity during cooperation. Cooperation, especially when reciprocated, activated an area of the brain rich in dopamine, the chemical that produces the pleasurable sensation activated by certain drugs and other addictive behaviors.
To put this in perspective, in another …