Altruism and the Amygdala

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By Mary Carpenter

WHEN ALTRUISTS go out of their way to help people they don’t know—along with the risks they take of harming themselves—it may stem from having different brains than most people, also very different from those of psychopaths. In Confessions of a Good Samaritan, filmmaker Penny Lane presents her experience and that of others as they become living donors of kidneys to people they have never met.

Compared to typical people, MRI scans of “non-directed” kidney donors reveal an amygdala, dubbed the “fear center” of the brain, that is larger and more active—along with higher levels of the hormone oxytocin—that enable them to ignore the risks and endure the pain and lengthy recovery time of major surgery to make these donations, according to the film. Even as she suffers weeks of pain and depression following the surgery, Lane’s attitude persists—that because people have two kidneys, it seems obvious to donate one of them.

(Not only is there a waiting list for donated kidneys of about 100,000 people, many of whom will die soon without new kidneys, kidneys from living donors have a much better chance of surviving transplantation than those from cadavers. Most people awaiting donation rely on dialysis, usually requiring four exhausting hours a day, three days a week. Among “non-directed kidney donors,” however, 90% change their minds; and only two percent of all live kidney donations come from someone who does not know the recipient.)

“Most people are more generous toward their family and friends than they are toward strangers, a behavior called social discounting,” according to Georgetown psychologist Abigail Marsh, featured in the documentary, whose research shows a “caring continuum that extends from psychopathy to extreme altruism.” Marsh contends that accounts from “real-life heroes [about] feeling decidedly un-stoic during rescues…helps support the role of the amygdala” in altruism.

The amygdala plays a role “in a wide range of social and emotional processes, but it’s probably best known for [that of] coordinating responses to threats,” writes Marsh. For example, the amygdala might link sensory information about the smell of leaking gasoline to previously learned information about its dangers. In altruists, increased levels of the hormone oxytocin would help shift attention away from dangers (of gas) toward caring for others—similar to elevated levels of oxytocin in mother rats that smell danger but act bravely to protect their babies.

“Neural activity in the amygdala directly mirrored [behavior, so that] the scientists could actually predict when certain monkeys were going to be generous and charitable,” writes Christopher Bergland on PsychologyToday. And when the hormone oxytocin “was introduced into a specific region of the amygdala, prosocial behaviors increased instantaneously.”

But those who disagree about the role of the amygdala believe it is merely a processor of sensory information, such as the sights and sounds of danger—with no role in decision-making or social behaviors. Writes Northeastern University researcher Philip Deming, who studies brains of psychopaths, “There is even mounting evidence refuting the notion that a circuit devoted to the emotion category of fear, or any other discrete emotion category, for that matter, exists in the human brain.”

“The “fear center” view of the amygdala…proposed that psychopathy is rooted in “fearlessness,” a diminished capacity for experiencing fear and for associating actions with, for example, the threat of punishment,” according to Deming. “After two decades of neuroimaging research on psychopathy, the reproducibility of amygdala findings is questionable…instead, the amygdala may be better understood [with the] primary function is to sense and control the viscera…include representing affect [such as arousal].”

Confessions of a Good Samaritan made a strong case for the unusual behavior of extreme altruism—as Lane showed her medical struggles in the aftermath of donation, without questioning her decision to donate. “Because social discounting is so ubiquitous, the question of why certain people choose to be altruistic toward strangers has long puzzled researchers,” according to the Georgetown University post about Marsh’s research—specifically, their ability to ignore possible risks and dangers.  Focusing on empathy, the ability to distinguish emotions in others, the researchers observed MRI scans of altruists that showed more active responses to expressions of fear in others, but not to anxiety or anger—compared with typical brains.

Psychopaths, on the other hand, feel less fear, anger and anxiety than average—giving them less capacity to recognize these emotions in others, notably in their victims. While not an official diagnosis, psychopathy encompasses extreme forms of several personality disorders, notably antisocial personality disorder (APD) and often narcissistic personality disorder (NPD). In general, people with APD are unable to consider the feelings of others without help.

Our research “helps us understand the brain mechanisms that allow altruists to value and care more about others,” writes Marsh. For comparison, testing with an online loving-kindness meditation training “could not induce generosity”—although researchers note “there could be future opportunities to mine deeper into this intervention.”

Donating a kidney to a stranger, much less to someone close to me, seems impossibly risky and unpleasant—especially the weeks or longer of painful recovery. Watching Confessions of a Good Samaritan, though, made me feel a little better—enabling me to blame, at least partially, my reluctant altruism on an average-size amygdala. And whether or not there is a physiological explanation, the film gave me even greater appreciation for people who commit such seemingly selfless acts to help others.

Note: Confessions of a Good Samaritan is available for streaming on Netflix.

—Mary Carpenter regularly reports on topical subjects in health and medicine.