The Biology of Benevolence

Is virtue really its own reward? When it comes to altruism, the
brain seems to pat itself on the back. The choice to cooperate stimulates
pleasure centers in the brain and can even overcome the urge to strive
for increased financial gains. This reward circuitry may provide a
biological basis for altruism, selfless behavior that is unique to
humans.

Researchers at Emory University scanned the brains of 36 women as
they played Prisoner's Dilemma, a game that pits two subjects against
each other and has been used in the study of social behavior for at least
half a century. Subjects were rewarded money based on their choice to
defect or to cooperate: A defection resulted in greater financial gain,
while cooperation activated areas of the brain linked to the processing
of pleasures such as drugs and food. Researchers also paired subjects
with a computerized partner, but cooperation in this instance stimulated
only one region of the brain, as opposed to the three distinct areas
involved in positive human interactions.

Subjects reported feelings of trust and camaraderie toward their
partners—emotions key to sustaining cooperation. And after cooperating in
one round, participants were less likely to defect. "This reward circuit
is strong enough to override the temptation to opt for selfish short-term
gains," explains James Rilling, Ph.D., the lead investigator and a
postdoctoral research fellow at Princeton University. The study used only female subjects to avoid the
confounding factor of gender roles. Rilling speculates that the outcome
would be the same with male subjects.

Rilling notes that there is one instance in which subjects shunned
cooperation: when reacting to a partner who had previously defected on
them. "If you can't trust the other person, sometimes the safest thing to
do is defect."