Possibly relevant or informative, from this month's SciAm.
The decision to help a friend or stranger—and the amount of help that one chooses to give—may be powerfully shaped by the brain’s basolateral amygdala
...why are some people more generous to socially distant individuals than others are? In recent research, my colleagues and I
gained new insight into these questions by examining a rare population of individuals with selective damage to a part of the brain called the basolateral amygdala. Our findings suggest that this small but important structure may be essential for calibrating our generosity based on how close or distant others feel to us.
Across species, this region has been shown to participate in
evaluating social rewards,
empathic responses and
decisions involving others. In
rodents and
monkeys, neurons in the basolateral amygdala encode the value of not just rewards for oneself but also the rewards received by others. And in humans, the structure has been linked to traits such as
trust,
empathy,
moral decision-making and
extraordinary altruism. Human amygdala volume also correlates with the
size and complexity of a person’s social network. And some evidence suggests that
psychopathy and
aggression are associated with a smaller, less functional amygdala.
To test this idea, my colleagues and I turned to a remarkable group of people in South Africa who have Urbach-Wiethe disease, a very rare genetic condition that causes selective bilateral damage to the basolateral amygdala while leaving the rest of the brain intact. In our study, we invited five women with this condition and 16 women without it to take part in a social discounting task. Each participant listed eight people from her own social network, ranging from her emotionally closest person (ranked as having a social distance of 1) to someone she barely knew (50) or a complete stranger (100). We then asked them to make decisions about how to split money. In each of several rounds, they received a fixed monetary amount and decided how much to share with each of their eight listed contacts.
As expected, the participants gave more to people they were close to than they gave to others who were more distant. That is, generosity declined as social distance increased. We found it interesting, however, that participants with damage to the basolateral amygdala were less generous overall than others, and their generosity decreased more sharply as social distance increased. They showed what we call steeper social discounting: they were still willing to help those they were emotionally closest to, but their willingness to give dropped off markedly for more distant individuals.
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Social distance is, in my mind, a fairly subjective measurement. Once we get beyond people we personally know, some have opined that there is an ordo amoris, an order of caring among different groups, while others have opined that we inhabitants of earth are all sistren and brethren.
