Altruistic people, such as those who would be willing to donate an organ to a stranger, show a stronger response to fearful faces in the form of a spike of activity in the amygdala when scanned using fMRI, according to a feature in the Discover D-Brief Blog.

Researchers including Abigail A. Marsh, PhD, from the department of psychology at Georgetown University, Washington, DC, found that the right sides of altruists’ amygdalas were 8 percent bigger than controls who did not to donate an organ.

They published the results last week in the Proceedings of the National Academy of Sciences. These findings are an interesting contrast to a previous study in psychopaths that revealed smaller amygdalas, indicating a reduced ability to feel empathy.