This 2014 Georgetown study was of people who had donated a kidney to a stranger. The study found that the subjects had a larger right amygdala part of their limbic systems:

“Our results support the possibility of a neural basis for extraordinary altruism.

In sum, our findings suggest that individuals who have performed an act of extraordinary altruism can be distinguished from healthy controls by increased right amygdala volume, as well as heightened responsiveness in right amygdala to fearful facial expressions, which may support enhanced recognition of these expressions.”

The researchers stopped short of causal explanations. They stated in the study’s abstract that:

“Individual variation in altruistic tendencies may be genetically mediated”

but didn’t develop any evidence to support this statement.

It would have been within the scope of the study had the researchers continued on to examine:

• What may have happened in the subjects’ lives to possibly cause their neurobiological and psychological attributes?
• What were the causes for the subjects’ extreme altruistic behavior?
• Were these the same causes for their larger, more sensitive amygdala?

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An accompanying PNAS commentary from a Harvard researcher made other points. However, the author showed his biases that the cerebrum rules human behavior with an out-of-left-field question at the end of a paragraph in which he developed specious reasoning.

The commentator was completely off base when he stated:

“Could it be that extraordinary altruists such as Maupin [a study participant] and the 19 individuals studied by Marsh et al. [the researchers] are special, not only because of how they feel when they see people in distress, but because of how they think?”

I don’t imagine that the brilliant commentator’s attempt to upstage the study’s subjects and put the spotlight on himself for some brilliant idea was much appreciated by anyone involved.

The amygdala is the central hub of a person’s limbic system. The study’s findings had very little to say about the subjects’ cerebral activity – thinking.

To postulate that the researchers missed that there was something different about the subjects’ thinking was out of touch with the realities of both the researchers’ scientific bases and the subjects. It’s another example of the current research mindset/social meme of cerebral dominance.

http://www.pnas.org/content/111/42/15036.full “Neural and cognitive characteristics of extraordinary altruists”