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It is just a small, almond-shaped body part that is situated in the front of the brain's temporal lobe. Scientists have always associated the amygdala with negative, primal behaviors, such as fear and rage. However, researchers at the University of Pennsylvania found that the unique collection of nuclei can help to promote positive social behavior, such as kindness and charity, making them better understand autism and anxiety too.

"What we're trying to do 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," said Michael Platt, co-author, in a press release.

"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."

The social behavior of rhesus macaques, a species of non-human primates examined for 22 years, showed a link between reward and donation. It was an experiment that made them see how they could make beneficial decisions.

"We have an actor monkey and a recipient monkey," he said. "The actor monkey learns that different colored shapes on the screen are associated with a reward that can be delivered to himself, to the monkey next to him, to both or to nobody at all. They learn that over a couple of weeks."

Scientists offered the actor monkey with some options. They could either keep the reward, share it or give it away.

"Generally, our actor monkeys prefer to reward the other monkey rather than let it go unclaimed," said Platt. "They are more likely to give to those they're more familiar with, and also to monkeys subordinate to them. The social relationships shape how prosocial the actor monkeys are."

Platt and his team examined the amygdala's neural activity, finding that it correlated with value placed on the reward for the actor. It helped them to predict when the actors would offer rewards based on its neural activity.

The study was published in the Dec. 14 issue of the Proceedings of the National Academy of Sciences.