Why do we feel each other's pain?
The ability to suffer not only our own pain -- which anything with a rudimentary nervous system can do -- but also the pain of others, has long been considered the distilled essence of our humanity. Altruism, which comes from the Latin root alter, or "other," could not exist without this distinction, but it is only since the mid 1990s that we've actually come to understand how empathy is sparked in the human brain, and why our species alone -- in all of creation -- has the hard wired ability to step far enough outside ourselves to walk in another person's shoes.
One summer day in Parma, Italy, neurologist Iaccomo Rizzolatti was conducting an experiment on monkeys when something extraordinary took place. Rizzolatti and his team were studying the region of the monkey's brain involved in planning and carrying out movements. Each time the monkey took hold of an object, cells corresponding with that region in the brain would activate and cause the monitor to beep. Then came the eureka moment. A student of Rizzolatti's entered the lab holding an ice cream cone. When he lifted the ice cream to his mouth, the monitor started to beep, even though the monkey hadn't moved at all but was merely watching the student enjoy his afternoon gelato.
"It took us several years to believe what we were seeing," Dr. Rizzolatti later told the New York Times. In fact, the neurologist and his team had accidentally discovered a special class of cells called mirror neurons that had fired in the monkey's brain simply because he had observed an action. The human brain has mirror neurons that are far smarter, more flexible, and more highly evolved than those in monkeys, Rizzolatti later deduced, and with this revelation we entered a brave new world of moral understanding. Brain guru extraordinaire V. Ramachandran has suggested that the discovery of mirror neurons will provide a "unifying framework" for explaining everything from how empathy, language and culture work to why some people are autistic. This could turn out to herald "the fifth revolution in human history," Ramachandran claims, "the ‘neuroscience revolution'" -- following the paradigm-shifting breakthroughs of Copernicus (the earth's not the center of the universe), Darwin (natural selection), Freud (the existence of the subconscious), and Crick (the discovery of DNA).
Mirror neurons are the brain's hardware for harmonizing individuals to their environment. The sole purpose of these neurons is to reflect inside ourselves actions we observe in others. "Mirror neurons allow us to grasp the minds of others not through conceptual reasoning but through direct simulation," Rizzolatti explains. "By feeling, not by thinking." It is because of mirror neurons that you blush when you see someone else humiliated, flinch when someone else is struck, and can't resist the urge to laugh when seeing a group struck with the giggles. (Indeed, people who test for "contagious yawning" tend to be more empathic.) Mirror neurons are the reason why emotions - both negative and positive - are so inexplicably contagious. They enable us to experience others as if from inside their own skin. In order to understand other people, we actually become them - a little bit - and bring the outside world inside by way of our own nervous systems.
Mirror neurons are the reason for the chameleon effect (the brain-to-brain imitation that causes babies to stick out their tongues when you do), as well as the Michelangelo effect, in which couples who've been married a long time begin to resemble one another by mirroring each other's expressions. As Daniel Goleman has pointed out, by mimicking what another person does or feels, mirror neurons create a shared sensibility, imprinting our neural pathways with imitated emotions. Seeing another's pain or disgust is almost exactly like being disgusted or in pain oneself. This maps the identical information from what we are seeing onto our own motor neurons, allowing us to participate in the other person's actions as if we ourselves were executing that action. Moreover, when we witness another being rejected, our brains "actually register the pain of social rejection," which is "mapped in the brain by the same mechanism that encodes physical real pain." Social emotions like guilt, shame, pride, embarrassment, disgust, and lust are learned in precisely the same way, from observing the responses of others, beginning with our parents.
As babies gaze out at the world, reading the faces and gestures of their caretakers, they are literally etching in their own brains a repertoire for emotion, behavior, and how the world works. A newborn baby, barely able to see, can imitate the facial expressions of adults within one hour of delivery. This motor imitation feeds the emotional system. Merely seeing a picture of a happy face elicits fleeting activity in the muscles that pull a child's mouth up into a smile. When a child unconsciously mimics the delight or sadness of a caretaker, this automatically creates a coupling between the baby's expressions and its emotions (this is also why physical behaviors such as smiling actually make us feel better - whether we're having a good day or not).
From the beginning, we respond to each other's feelings. When infants hear other babies crying, they howl, too - almost from birth - to show they are sympathetically upset. Mirror neurons appear to be linked to autism; some scientists believe that people with autism have "broken mirror" neurons that deprive them of bonding skills and empathy. (While many people with autism can identify an emotional expression, like sadness, or imitate sad looks with their own faces, they do not feel the emotional significance of the imitated emotion.)
So, the next time you start tearing up when you witness someone else in pain, or feel the queasy sensation of grief when you see a tragedy on TV, don't turn away or change the channel. Be grateful that your mirror neurons are doing their job, maintaining the hard-wired connection between your heart and the rest of the world.