Marc Lewis*1 “So we're not inherently selfish – but selflessness requires careful thought” http://www.theguardian.com/commentisfree/2016/mar/24/altruism-brain-research-selfish

UCLAのLeonardo Christov-Moore氏*2らのグループは人間の所謂「利他主義(altruism)」が脳のどの部位で掌られているのかということを調査した*3

In each of two dozen trials, participants were offered $10, shown a head shot and pseudonym for another player, and then allowed five seconds to decide “how much $ would you like to offer?” – knowing they’d get to keep the rest. It was real money, and the recipients were real people.

The researchers, Leonardo Christov-Moore and colleagues, assumed that the amount given away indicated each participant’s level of “self-other resonance” or “prosocial decision-making” – in common parlance, altruism or empathy.


We aready know that certain areas “light up” when people respond empathically. One of these is the insula*4, a patch of neurons lodged between the higher reaches of the cortex*5 and the more primitive limbic system*6. The insula allows us to feel our own bodily sensations and, apparently, those of others.

Indeed, Christov-Moore detected more insula activation when people were more generous with the “give” button. Yet the brain region we’re most proud of, that distinguishes us most from other apes and provides us with such handsome foreheads, is the prefrontal cortex*7, the seat of self-control. That region got activated too. But the experiment went further than scanning the brain, comparing activation strengths in both regions. It also manipulated the brain. A technique called transcranial magnetic stimulation (TMS) was used to disrupt the workings of the prefrontal cortex, at least temporarily. Let’s send the manager out for lunch and see how the empathy region behaves without supervision.

Like most researchers (at least those who get published) Christov-Moore and colleagues found what they expected to find. With their prefrontal cortex set to “low”, the people in this study did indeed give away more money. The researchers concluded that, thanks to the insula and its neighbours in the limbic system, “our primary [human] drive … may in fact be to behave prosocially”. Whereas the cognitive controls housed in our latest neural upgrade, the prefrontal cortex, mostly get in the way, probably because they are tuned by evolution to rational self-interest.

In their words, “knocking out these areas appears to free your ability to feel for others.” So, our capacity for logic and judgment, the conventional hallmark of human progress, actually obstructs our deeper (and kinder) selves. In fact, through a “non-invasive” brain manipulation, the “noble savage” can be freed from the self-serving rationality of our prefrontal lobes.

でもちょっと待て! とMarc Lewis氏はいう。

What the UCLA researchers failed to see, and what other science reporters missed as well, is that there are many ways to interpret a correlation between prefrontal activation and socially loaded choices in an experimental setting. In this study, the prefrontal cortex may have constrained the “giving” choices, not because they were altruistic but because they were contrived. Then, with cognitive self-control broken down by TMS, concerns about being manipulated may have lost their hold, so that “generous” choices could proceed without censure.

In fact, it seems that our capacities for reason, perspective, and self-control can either enhance empathy or suppress it. We fashion standards and strategies for our actions, including interpersonal actions, in the prefrontal cortex.

When we view the recipients of our generosity as members of an in group – people like ourselves – then those standards and strategies lean toward altruism. When they are identified as members of a despised out group, then it’s more sensible to harm them instead.

Certainly this is the tip of a huge iceberg. The prefrontal cortex evolved as a partner and guide for the motivational brain. They work together to optimise behaviour across a broad range of contexts. It is too simple to say that rational judgment suppresses (or facilitates) a particular motivational thrust. It depends on the situation.


Let me end with a point that’s quite the opposite of Christov-Moore’s conclusions. We pride ourselves on our prefrontal cortex because it vaults us beyond the base impulsivity of our animal cousins. But it can only achieve this feat by distancing us from our actions, allowing us to think before we act and consider desirable outcomes beyond our immediate gains.

I doubt whether altruism would count for much if it weren’t for the guidance of our prefrontal lobes. We have to know where to aim our generous impulses and when to release them. For empathy to be effective, to help where help is needed, we must rely on intelligence, discernment, and sometimes patience. If only they were in greater supply.