While the amygdala at the front end of the brain's temporal lobe has long been associated with fear, it also can influence kindness and what might be called charitable giving in humans, a study (6 pages, PDF) published in the journal Proceedings of the National Academy of Sciences finds.

Researchers at the University of Pennsylvania, Yale University, and Duke University found that when rhesus macaques — which, like humans, live in large social groups and form long-term social bonds — are given a choice to either keep a reward, share it with another macaque, give it away, or let it go unclaimed, they preferred to give the reward to another monkey rather than let it go unclaimed — and were more likely to give it to monkeys they were familiar with or to monkeys that were subordinate to them. Researchers also found that neural activity in the amygdala reflected the value of the recipient monkey's reward in the same way it reflected the value of the reward for the "actor" monkey, enabling scientists to predict, based on these neural responses, when actor monkeys would give rewards to recipients. Moreover, when the monkeys were given oxytocin, a hormone linked to social bonding, they became more "prosocial" (willing to give to other monkeys) and paid more attention to recipient monkeys after offering the reward.

Though not definitive, research on how oxytocin affects humans has, in some cases, been shown to help those with autism better read and understand social cues. "When people inhale oxytocin," said Michael Platt, the James S. Riepe University Professor in psychology, neuroscience and marketing at Penn, "there is a change in blood flow to the amygdala, which we think might be involved in making people kinder and more receptive to others.

"What we're trying to do," added Platt, "is both identify and understand the basic brain mechanism that allows us to be kind to each other and to respond to the experiences of other individuals. We're also trying to use that knowledge to evaluate potential therapies that could improve the function of these neural circuits, especially for those who have difficulty connecting with others."