Extreme altruism: right on!, The Economist, September 20th, 2014. An excerpt:
Flyers at petrol stations do not normally ask for someone to donate a kidney to an unrelated stranger. That such a poster, in a garage in Indiana, actually did persuade a donor to come forward might seem extraordinary. But extraordinary people such as the respondent to this appeal (those who volunteer to deliver aid by truck in Syria at the moment might also qualify) are sufficiently common to be worth investigating. And in a paper published this week in the Proceedings of the National Academy of Sciences, Abigail Marsh of Georgetown University and her colleagues do just that. Their conclusion is that extreme altruists are at one end of a “caring continuum” which exists in human populations—a continuum that has psychopaths at the other end. [...]
She and her team used two brain-scanning techniques, structural and functional magnetic-resonance imaging (MRI), to study the amygdalas of 39 volunteers, 19 of whom were altruistic kidney donors. (The amygdalas, of which brains have two, one in each hemisphere, are areas of tissue central to the processing of emotion and empathy.) Structural MRI showed that the right amygdalas of altruists were 8.1% larger, on average, than those of people in the control group, though everyone’s left amygdalas were about the same size. That is, indeed, the obverse of what pertains in psychopaths, whose right amygdalas, previous studies have shown, are smaller than those of controls.
Whether this applies to EAs, however, is unclear. Compare Peter Singer's recent remarks in a panel discussion about empathy:
My admittedly impressionistic observation is that effective altruists are not especially empathetic—at least, not in the sense of emotional empathy. They do have what is sometimes called “cognitive empathy” or “perspective taking” capacity—that is, the ability to see what life is like for someone else.