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There's a man out there somewhere who looks a little bit like the actor Idris Elbeth, or at least he did 20 years ago. I don't know anything else about him except that he once saved my life by putting his own life in danger. This man ran across four lanes of freeway traffic in the middle of the night to bring me back to safety after a car accident that could have killed me. And the whole thing left me really shaken up obviously, but it also left me with this kind of burning, annoying need to understand why he did it. What forces within him caused him to make the choice that I owe my life to, to risk his own life to save the life of a stranger. In other words, what are the causes of his or anybody else's capacity for altruism? But first let me tell you what happened. That night I was 19 years old and driving back to my home in Tacoma, Washington down the interstate 5 freeway when a little dog darted out in front of my car. And I did exactly what you're not supposed to do, which is swirled to avoid it. And I discovered why you're not supposed to do that. I hit the dog anyways. And that sent the car into a fish tail and then a spin across the freeway. And so finally it wound up in the fast land of the freeway, facing backward into oncoming traffic. And then the engine died. And I was sure in that moment that I was about to die too. But I didn't because of the actions of that one brave man who must have made the decision within a fraction of a second of seeing my stranded car. So pull over and run across four lanes of freeway traffic in the dark to save my life. And then after he got my car working again and got me back to safety and made sure I was going to be all right, he drove off again. Never even told me his name. And I'm pretty sure I forgot to say thank you. So before I go any further, I really want to take a moment to stop and say thank you to that stranger.

I'm telling you all this because the events of that night changed the course of my life to some degree. I became a psychology researcher and I've devoted my work to understanding the human capacity to care for others. Where does it come from and how does it develop and what are the extreme forms that it can take? These questions are really important to understanding basic aspects of human social nature. A lot of people, and this includes everybody from philosophers and economists or ordinary people, believe that human nature is fundamentally selfish. They were only ever really motivated by our own welfare. But if that's true, why do some people, like the stranger who rescued me, do selfless things like helping other people at enormous risk and cost to themselves? During this question, requires exploring the roots of extraordinary acts of altruism and what might make people who engage in such acts different than other people. But until very recently, very little work on this topic had been done. The actions of the man who rescued me meet the most stringent definition of altruism, which is a voluntary, costly behavior motivated by the desire to help another individual. So it's a selfless act intended to benefit only the other. Work could possibly explain an action like that. One answers compassion, obviously, which is a key driver of altruism. But then the question becomes, why does some people seem to have more of it than others? And the answer may be that the brains of highly altruistic people are different in fundamental ways.

But to figure out how, I actually started from the opposite end with psychopaths. A common approach to understanding basic aspect of human nature, like the desire to help other people, is to study people in whom that desire is missing. And psychopaths are exactly such a group. Psychopathy is a developmental disorder with strongly genetic origins, and it results in a personality that's cold and uncaring and a tendency to engage in anti-social and sometimes very violent behavior. Once my colleagues and I at the National Institute of Mental Health conducted some of the first ever brain imaging research, the psychopathic adolescents. And our findings and the findings of other researchers now have shown that people who are psychopathic pretty reliably exhibit three characteristics. First, although they're not generally insensitive to other people's emotions, they are insensitive to signs that other people are in distress. And in particular, they have difficulty recognizing fearful facial expressions like this one. And fearful expressions convey urgent need and emotional distress, and they usually elicit compassion and a desire to help and people who see them. So it makes sense that people who tend to lack compassion also tend to be insensitive to these cues. The part of the brain that's the most important for recognizing fearful expressions is called the amygdala. They're very rare cases of people who lack amygdala completely, and they're profoundly impaired in recognizing fearful expressions. And, whereas healthy adults and children usually show big spikes in amygdala activity when they look at fearful expressions, psychopaths amygdala are under reactive to these expressions, sometimes they don't react at all, which may be why they have trouble detecting these cues. Finally, psychopaths amygdala are smaller than average, by about 18 or 20 percent.

So all of these findings are reliable and robust and they're very interesting. But remember that my main interest is not understanding why people don't care about others. It's understanding why they do. So the real question is, could extraordinary altruism, which is the opposite of psychopathy in terms of compassion and a desire to help other people, emerge from a brain that is also the opposite of psychopathy, sort of anti-psychopathic brain, better able to recognize other people's fear. An amygdala that's more reactive to this expression and may be larger than average as well. As my research has now shown, all three things are true. And we discover this by testing a population of truly extraordinary altruists. These are people who have given one of their own kidneys to a complete stranger. So these are people who have volunteered to undergo major surgery so that one of their own healthy kidneys can be removed and transplanted into a very ill stranger that they've never met and may never meet. Why would anybody do this? That's a very common question. And the answer may be that the brains of these extraordinary altruists have certain special characteristics. They are better at recognizing other people's fear. They're literally better at detecting when somebody else is in distress. This may be, in part, because their amygdala is more reactive to these expressions. And remember, this is the same part of the brain that we found was under-reactive in people who are psychopathy. And finally, their amygdala are larger than average as well, by about 8%.

So together what these data suggest is the existence of something like a caring continuum in the world that's anchored at the one end by people who were highly psychopathic and that the other by people who were very compassionate and driven to acts of extreme altruism. But I should add that what makes extraordinary altruists so different is not just that they're more compassionate than average. They are. What's even more unusual about them is that they're compassionate and altruistic, not just towards people who are in their own innermost circle of friends and family. Because they have compassion for people that you love and identify with is not extraordinary. Truly extraordinary altruists, compassion extends way beyond that circle, even beyond their wider circle of acquaintances, the people who are outside their social circle altogether. Total strangers, just like the man who rescued me. And I've had the opportunity now to ask a lot of altruistic kidney donors, how it is that they manage to generate such a wide circle of compassion that they're willing to give a complete stranger their kidney. And I found it's a really difficult question for them to answer. I say, you know, how is it that you're willing to do this thing when so many other people don't? You're one a fewer than 2,000 Americans who's ever given a kidney to a stranger. What is it that makes you so special? And what do they say? They say nothing. There's nothing special about me. I'm just the same as everybody else. And I think that's actually a really telling answer because it suggests that the circles of these altruists don't look like this. They look more like this. They have no center. These altruists literally don't think of themselves as being at the center of anything, as being better or more inherently important than anybody else.

When I asked one altruist why donating her kidney made sense to her, she said, because it's not about me. Another said, I'm not different. I'm not unique. Your study here is going to find out that I'm just the same as you. I think the best description for this amazing lack of self-centeredness is humility, which is that quality that in the words of St. Augustine makes men as angels. And why is that? It's because if there's no center of your circle, there can be no inner rings or outer rings. Nobody who's more or less worthy of your care and compassion than anybody else. And I think that this is what really distinguishes extraordinary altruists from the average person. But I also think that this is a view of the world that's attainable by many and maybe even most people. And I think this because of the societal level, expansions of altruism and compassion are already happening everywhere. The psychologists, Stephen Pinker and others have shown that all around the world, people are becoming less and less accepting of suffering and ever widening circles of others, which has led to the clients of all kinds of cruelty and violence from animal abuse to domestic violence to capital punishment. And it's led to increases in all kinds of altruism. A hundred years ago, people would have thought it was ludicrous. How normal and ordinary it is for people to donate their blood and bone marrow to complete strangers to that. Is it possible that a hundred years from now, people will think that donating a kidney to a stranger is just as normal and ordinary as we think donating blood and bone marrow is today? Maybe.

So what's at the root of all these amazing changes? In part, it seems to be increases in wealth and standards of living. As societies become wealthier and better off, people seem to turn their focus of attention outward. And as a result, all kinds of altruism towards strangers increases from volunteering to charitable donations and even altruistic kidney donations. But all of these changes also yield a sort of strange and paradoxical result, which is that even as the world is becoming a better and more humane place, which it is, there's a very common perception that it's becoming worse and more cruel, which it's not. And I don't know exactly why this is, but I think it may be that we now just know so much more about the suffering of strangers in distant places. And so we now care a lot more about the suffering of those distant strangers. But what's clear is that the kinds of changes we're seeing show that the roots of altruism and compassion are just as much a part of human nature as cruelty and violence, maybe even more so. While some people do seem to be inherently more sensitive to the suffering of distant others, I really believe that the ability to remove oneself from the center of the circle and expand the circle of compassion outward to include even strangers is within reach for almost everyone.