Empathy, research indicates, is made possible by a special group of nerve cells called mirror neurons.

What enables us to feel empathy—to experience or share another person’s pain, fear, joy, or any other emotion? Empathy, research indicates, is made possible by a special group of nerve cells called mirror neurons, at various locations inside the brain. These special cells enable us to “mirror” emotions. However, the activity of these neurons can be modified by various factors, including the relationship of the people involved. A new study suggests that, at least in men, whether we empathize with another person’s pain depends on how that person had behaved in the past, and, perhaps more important, whether we like or dislike them. Mirror, Mirror in the Brain Mirror neurons were first discovered in the early 1990s by Italian scientists who, while looking at the activity of individual nerve cells inside the brains of macaque monkeys, noticed that neurons in the same area of the brain were activated whether the animals were performing a partic-ular movement (reaching for a peanut, for instance) or simply observing another monkey—or a researcher— perform the same action. It appeared as though the cells in the observer’s brain “mirrored” the activity in the performer’s brain. A similar phenomenon takes place when we watch someone experience an emotion and feel the same emotion in response, says Marco Iacoboni, a neuroscientist at the University of California, Los Angeles. The same neural systems get activated in a part of the cortex called the insula, which is part of the mirror neuron system, and in the emotional brain areas associated with the observed emotion. However, the amount of activation is slightly smaller for the “mirrored experience” than when the same emotion is experienced directly, Iacoboni adds. A recent study by Iacoboni and colleagues highlights the impor-tance of mirror neurons and their role in the development of autism spectrum disorder (ASD). ASD is a pervasive developmental disorder characterized by impaired social interactions. Iacoboni’s team used functional magnetic resonance imaging (fMRI) to investigate neural activi-ty of 10 high-functioning children with ASD and 10 normally developing children as they observed and imitated facial emotional expressions. Although both groups performed the tasks equally well, children with autism showed reduced mirror neuron activity, particularly in the area of the inferior frontal gyrus. Moreover, the degree of reduction in mirror neu-ron activity in the children with autism correlated with the severity of their symptoms. Iacoboni says, these results indicate that a healthy mirror neuron system is crucial for normal social development. “If you have ‘broken mirrors,’ or deficits in mirror neurons, you likely end up having social problems, as patients with autism do,” he says. There are many kinds of mirror neurons, Iacoboni says. They include neurons for hand actions such as grasping, holding, and tearing, and mouth actions including biting, drinking, and a wide variety of facial gestures. “We also think there are ‘super mirror neurons,’ although we do not yet have direct evidence for their existence,” he says. These super mirror neurons could control and inhibit the activity of lower-level mirror neurons, Iacoboni suggests. He also hypothesizes that by modulating, or modifying, the activity of other neurons, super mirror neurons could enable one to experience either pain or joy, depending on the circumstances, when watching another person suffer. From Pain to Joy In a study published in the Jan. 26, 2006, issue of Nature, Tania Singer, a research fellow at the Wellcome Department of Imaging Neuroscience at University College London, and colleagues found what could be, according to an accompanying editorial, the first neuroscientific evidence for the existence of schadenfreude, the joy derived from another’s troubles. In order to investigate the conditions under which individuals empathize with another person’s pain, the researchers first had their subjects take part in a game in which the other participants were associates, or “con-federates,” of the experimenters. The confederates played either fairly (displaying trust and cooperation) or unfairly (exhibiting a lack of trust and cooperation), in an attempt to make the subjects like or dislike them. The research subjects always “moved first” and could show they either trusted the other players, by sending them money, or mistrusted them, by withholding the money. The confederates were always “second movers” and could choose between a fair and an unfair response: returning high or low amounts of money. “We used this game because we know that it is a very good way to induce strong emotions,” Singer says. “If you engage in cooperation and trust and the other person doesn’t trust you, you really start disliking this person. But if people respond with cooperation, you begin to like them.” An analysis of the results showed that subjects did indeed perceive the confederates as being fair or unfair according to their game-playing strategy. Furthermore, behavioral ratings confirmed that both male and female subjects rated the fair players as being significantly more agreeable, more likeable, and more attractive than the unfair players. In the second part of the experiment, the investigators used functional magnetic resonance imaging to look at brain activity patterns while the subjects observed the confederates, who they thought were being given painful electric shocks. As expected, subjects showed strong activation of pain-related brain regions when witnessing fair players receiving electric shocks. However, these empathy-related responses were significantly reduced in males when observing an unfair person being shocked. Moreover, this effect was accompanied by “increased activation in reward-related areas, which correlated with an expressed desire for revenge,” the investigators reported. Singer says the fact that some people appear to be pleased when others who had been unfair are being punished can be explained in terms of evolutionary psychology. “It is important for people to cooperate with one another, if society is to remain stable,” she says. “Therefore, it might be good if people punish those who are unfair and do not cooperate, so that overall, society gets more and more cooperators.” The scientists are not sure why men appeared to be less empathetic and more revengeful than women toward unfair players. Singer speculates that this finding is attributable to the study having involved the application of physical pain (electric shocks applied to the back of the hand). “If we had a psychological revenge, such as ruining the reputation of the other player, perhaps women would behave the same way,” she says.

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