Altruism: A Story of Amygdalae and Kidneys
What is the first thing that comes to mind when you hear the phrase “animal instincts”? We tend to associate animal instincts with sex and aggression, framing the rest of the animal kingdom as entirely selfish creatures whose only goals are food and reproductive success. In contrast, we humans like to think of ourselves as endowed with mechanisms of self-control and with an innate benevolence towards others, the ability for selflessness and empathy. We are pinnacles of righteousness, our moral compasses placing us in a different realm than the rest of earth’s inhabitants. And it’s true—it is difficult to find examples of true altruism outside of humankind, which makes it an intriguing topic for neuroscientists and psychologists.
The first task at hand in studying altruism is to define it. The Oxford English Dictionary describes it as “disinterested or selfless concern for the well-being of others, esp. as a principle of action.” There is also a secondary definition from zoology: “Behaviour of an animal that benefits one or more others (typically of its own species), but which carries a cost for the individual concerned.” Some would argue for an additional condition: for an act to be truly altruistic, there must be no advantage to the individual, even in terms of evolutionary benefit.
This is the point at which instances of seemingly generous sacrifice among other species fail to make the cut. For example, honeybees sting anyone who threatens their nest in an act of martyrdom, dying to protect their bee-utiful bee relatives. But this ensures that their genetic material—present in those relatives—will continue to thrive. The honeybee’s sacrifice is really an attempt at achieving genetic immortality. But what about helping non-kin? Mama bats not only feed their young, but also feed other lady bats (who were less lucky hunters that day) by regurgitating blood from their latest kill into the other females’ mouths (yummy!). But the bats are being generous with the expectation that the recipients of their bloody snack will return the favor someday. The strategy seems to work; the other females do reciprocate, perhaps contributing to the fact that female bats live about twice as long as male bats who are too cool to share .
The possible beginnings of true altruism can be seen in our species’ closest living relatives, chimpanzees. A study showed that baby chimps were quick to help a struggling adult experimenter, jumping to hand the adult an item that had fallen out of reach although they were given no reward or praise for doing so . A group of 18-month-old infants in the same study offered help in more situations than the chimps did, perhaps pointing to greater innate altruism but also possibly because the human infants understood the goals of the experimenter more fully than the baby chimps. Either way, the study suggests that our last common ancestor might have had a tendency for altruistic cooperation.
While the chimps’ helpful spirit was mostly limited to retrieving fallen items, the examples of altruism (according to the Oxford English Dictionary) in human society are innumerable. But with the additional condition of no personal advantage, the altruistic nature of many of our actions might be called into question. Because our society reveres magnanimity, making a sacrifice for someone else boosts one’s own popularity. In addition, like the bloodthirsty bats, if we dole out occasional favors, our kindnesses are likely to be returned when we are in a position of need. And of course, altruism is a sought-after characteristic in a mate , making selfless behavior a tool for success in the mating game. For more discussion on the psychosocial forces behind gift-giving, check out a previous NeuWriteSD piece by Ethan!
So, how do you begin to study the neural underpinnings of something so difficult to define or identify? And since virtually all of us do kind things on occasion, how would you compare altruists and non-altruists to see whether there are any differences in brain structure or activity? Dr. Abigail Marsh, a professor at Georgetown University, was determined to find a way. She recruited a group of 19 extraordinary altruists: men and women who had donated a kidney to a complete stranger.
Anonymous organ donation to a stranger ranks among the most bewildering examples of extreme altruism. The surgery comes with serious risks, recovery is painful, and the donors are making this sacrifice for someone they’ve never met. For all they know, the recipient might be someone who cheats on his wife or harbors a hatred for small animals or is voting for Donald Trump for President of the United States. This is also not a situation in which the altruistic act draws admiration from family and friends; acquaintances of the donor tend to view the decision as a bit batty. My driver’s license says “Organ Donor,” but I wasn’t planning to have any of my organs harvested while I am still alive and actively using them, and I don’t think my mother would encourage me to do so. But I digress.
When she brought the group of kidney donors to her lab, Dr. Marsh had a specific hypothesis for what she might find. She had done extensive research on the neural basis of psychopathy—a disorder characterized by antisocial behavior and difficulty processing the emotional responses of others—and she proposed that altruism was on the opposite end of a continuous spectrum. At the heart of her hypothesis was a particular brain structure: the amygdala.
The amygdala is a pair of almond-shaped structures, one in each hemisphere of the brain. It is known as the brain’s center of emotional processing, especially important in how we experience fear and recognize it in others. You know how it’s hard to remember what you had for lunch on Monday, but you can remember an emotional moment from years ago with exceptional vividness? That is the amygdala at work—the neurons in the amygdala make direct connections with those in the hippocampus (the memory center of the brain) and modulate the formation of memory. Marsh and others had uncovered evidence of anomalies in the size and activity of amygdalae of those exhibiting psychopathic traits. For example, individuals with psychopathy have smaller amygdalae than normal [4,5]. If Marsh were correct in her intuition that altruism and psychopathy are opposite extremes on the same cognitive spectrum, we could expect that extraordinary altruists have larger amygdalae than the rest of us. Lo and behold, MRI scans confirmed that the anonymous kidney donors slightly larger right amygdalae than a group of non-donors! 
The study did not end with an MRI. Marsh’s lab also employed a well-known facial recognition task: participants viewed a series of fearful, angry, and neutral facial expressions while in an fMRI scanner. fMRI is neuroimaging technique that shows which parts of the brain are active as someone is doing a particular task. Individuals with psychopathy exhibit less amygdala activity than control subjects when they view fearful faces —presumably indicating that they are less able to identify and empathize with the emotion expressed in the picture. Marsh hypothesized that extraordinary altruists would have an uncanny ability to notice when someone else was experiencing fear and that activity in the amygdala would reflect this hypersensitivity. Indeed, the altruistic kidney donors’ amygdalae were not only bigger but also more active when exposed to fearful expressions, which was directly correlated to their ability to correctly identify the expression as fear . Altruism is rooted in empathy—to help a friend in need, a necessary first step is recognition and connection with the friend’s state of distress. The amygdala helps us to do this.
Of course, the size and activity patterns of the amygdala cannot reliably predict whether a person will happily part with one of his internal organs—there are other forces at play. There are a few bits of evidence connecting certain genes to altruism. One such gene codes for a dopamine receptor, DRD4. Dopamine is a neurotransmitter, one of the brain’s most important signaling molecules. It is released from one brain cell and lands on a receptor on the surface of a second brain cell, propagating the signal forward. Dopamine is thought to be important in mediating activity of the limbic system , a system that includes the amygdala and is known for its role in emotion, motivation, and social cognition among others . A study of 785 people revealed that those without a certain form of the gene were significantly more likely to be altruists, as assessed by a lengthy questionnaire that measures five aspects of personality .
We’ve established that the amygdala and genes that affect brain signaling are important for altruism, but there are rarely cases when nature thoroughly trumps nurture in the classic, age-old debate. Thankfully, Abigail Marsh has some answers for us about nurture as well. She wondered how well subjective well-being (self-reported engagement, meaning, purpose, positive emotions, life satisfaction, etc.) would correlate to altruistic kidney donation. Of course, the nineteen altruistic kidney donors used in her other study would not be able to provide a big enough sample size to answer this question, so she looked to larger data sets, comparing the number of per capita altruistic kidney donations by state from 1999-2010 to the subjective well-being scores collected by an extensive Gallup poll. Indeed, she found a significant correlation between donation and subjective well-being. You are probably thinking that the effect must have been skewed by a myriad of other factors, particularly discrepancies in financial stability or health. But the effect remained significant even after corrections were made for state-level differences in income, income inequality, education, and physical and mental health .
This finding can be better understood in the context of a model of well-being set forth by Jayawickreme et al.: objective well-being (financial situation, health, etc.) increases subjective well-being, which increases “well-being outcomes”—intrinsically valuable outcomes that contribute to general well-being and can be independently measured . If people are living positively and are actively seeking meaning in their lives, they will be more likely to act altruistically. If helping others enhances psychological well-being, this will in turn make individuals even more likely to continue doing good for others in a perfect positive feedback cycle. Subjective well-being promotes altruism, which promotes subjective well-being, and so forth.
In an NPR interview, Angela Stimpson, a graphic artist from Albany, NY and one of Marsh’s 19 extraordinary altruists, describes her motivation for donating. She relates that she was 42 at the time, single with no children, and while she was very fortunate and loved her life, she would often question whether she had fulfilled her purpose. When she heard about the severe shortage of kidneys available to people on long transplant waitlists and realized that she was in a position to help someone entirely unconditionally, she had an “awe moment.” She never turned back.
At the risk of sounding cliché, it seems that altruism—extraordinary or ordinary—can help bring meaning and fulfillment to our lives. So fire-up your amygdalae! But I promise I won’t judge you if you decide to keep your kidneys. I certainly plan to.
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