Sympathy, Natural Sociality, and Mirror Neurons

In his Treatise of Human Nature (2.2.5.15), David Hume stresses the importance of sympathy for social life. We

"observe the force of sympathy thro' the whole animal creation, and the easy communication of sentiments from one thinking being to another. In all creatures, that prey not upon others, and are not agitated with violent passions, there appears a remarkable desire of company, which associates them together, without any advantages they can ever propose to reap from their union. This is still more conspicuous in man, as being the creature of the universe, who has the most ardent desire of society, and is fitted for it by the most advantages. We can form no wish, which has not a reference to society. A perfect solitude is, perhaps, the greatest punishment we can suffer. Every pleasure languishes when enjoyed apart from company, and every pain becomes more cruel and intolerable. Whatever other passions we may be actuated by; pride, ambition, avarice, curiosity, revenge or lust; the soul or animating principle of them all is sympathy; nor would they have any force, were we to abstract entirely from the thoughts and sentiments of others. Let all the powers and elements of nature conspire to serve and obey one man: Let the sun rise and set at his command: The sea and rivers roll as he pleases, and the earth furnish spontaneously whatever may be useful or agreeable to him: He will still be miserable, till you give him some one person at least, with whom he may share his happiness, and whose esteem and friendship he may enjoy."

A few paragraphs later, Hume remarks that "the minds of men are mirrors to one another, not only because they reflect each others emotions, but also because those rays of passions, sentiments, and opinions may be often reverberated, and may decay away by insensible degrees."

In associating "sympathy" broadly understood as fellow-feeling with "friendship," Hume suggests that this corresponds to Aristotle's use of "friendship" (philia) as a broad term for all social bonds. Unlike Thomas Hobbes, therefore, Hume does not think that rationality alone (Hobbes' "laws of nature") can make society possible. Rather, society requires the natural animal tendency to the affective bonding of sympathy. (Hobbes's "natural lust" for the "government of small families" [Leviathan, chap. 13] is a confined version of Hume's sympathy.)

Adam Smith elaborated this Humean conception in using sympathy as the social glue for all social bonding and moral life. Charles Darwin then adopted this Humean and Smithian conception of sympathy in explaining the natural social instincts and moral sense. Darwin was impressed by Hume's insistence that sympathy was not uniquely human because it was found in other social animals. "'Tis evident, that sympathy, or the communication of passions, takes place among animals, no less than among men" (Treatise, 2.2.12).

Neuroscience is now showing how this sympathy by which the minds of social animals are "mirrors to one another" is rooted in "mirror neurons."

In the early 1990s, Giacomo Rizzolatti and his colleagues at the University of Parma in Italy reported that their neurophysiologial studies of monkeys had uncovered some neurons with remarkable properties. These neurons were activated not only when a monkey performed a certain action--like reaching to pick up a raisin--but also when the monkey observed another monkey or a human being performing the same action. These "mirror neurons" seemed to show how primates understand the intentional actions of others by simulating those actions within their own brains.

Three years ago, I wrote a post on mirror neurons. Since then, the research has progressed, particularly in the study of mirror neuron systems in human beings. Rizzolatti and his colleagues have written two good surveys of this research. The most elaborate survey is a book--Mirrors in the Brain (MIT Press, 2008). A very brief survey is in a book chapter for the 4th edition of The Cognitive Neurosciences (MIT Press, 2009), edited by Michael Gazzaniga.

This research on mirror neurons has stirred a lot of popular interest, because if there are mirror neurons in human beings as well as monkeys, this would show how our brain allows us to understand the actions and emotions of other individuals by sharing their experiences in our own minds. The director and playwright Peter Brook observed that mirror neurons would explain the experience of great actors who become as one with their spectators. That we can share the experiences of even fictional characters is a powerful manifestation of our sympathy.

As Rizzolatti indicates, prior to the discovery of mirror neurons, it was common for neurophysiologists to assume that the motor areas of the cerebral cortex were clearly separated from those areas devoted to perception and cognition, and that the motor areas merely executed the orders coming from perceptive and cognitive processes: we perceive what is happening within and around us, we decide by cognition how to respond to these circumstances, and then we command the motor areas of our brain to execute appropriate movements.

But with the understanding of mirror neuron systems, we have to change the traditional view of our mental processes. The sharp division between perception, cognition, and movement is too artificial, because how we perceive or understand our surroundings is embedded in action. We cannot fully understand the movements of other people through a purely sensory or pictorial representation of those movements. We need mirror neurons through which our brains match the movements we see in others to the movements we ourselves perform. We must translate thought and sensation into movement, so that we understand the movements of others by resonating with those movements in our own minds.

In the Platonic tradition of rationalist psychology, the highest activity of the mind is purely contemplative reasoning, which strives to execute its practical decisions by forcing the body to obey the orders of pure reason. By contrast, the existence of mirror neurons suggests the pragmatic constitution of human thought as embodied cognition, by which we understand our world not through passive contemplation but through active movement.

In the context of evolution, it makes sense for the brain to be an instrument for active, bodily engagement with the world, because its evolutionary purpose would be to organize movements to defend against threats and seek out opportunities. For social animals, the greatest threats and opportunities often come from other animals, and so the brains of social animals are adapted for understanding the thoughts and emotions of other animals so that they can navigate their way through social life to ensure their survival and well being. Mirror neurons help primates to do this.

Even without the activity of a neural mirror mechanism, we can probably understand the actions and emotions of others through a purely reflexive processing of sensory information. But this purely intellectual understanding would be a colorless perception with no emotional depth. This is probably how psychopaths understand the moral emotions of other people but without actually feeling those emotions themselves. The impaired social understanding of autistic people probably comes from deficits in their mirror neuron systems.

Although neuroscientists have not yet observed mirror neuron activity in human beings at the level of single neurons--because of the ethical limits on neural research with living human beings--there is research with human patients suffering selective neural damage and research through neuroimaging that confirms the existence of mirror neuron systems, which function in understanding both actions and emotions.

For example, the emotion of disgust is a response to the undesirable taste or smelling of food, and it's associated with distinctive movements around the mouth, the wrinkling of the nose, and feelings of nausea. This experience of disgust requires the activation of the insular cortex of the brain. Our insular cortex is also activated when we observe other people showing the facial expressions of disgust. So the same neural activity necessary for triggering the sensations and expressions of disgust in ourselves is necessary for perceiving this emotion in the faces of other people. It seems that to fully understand someone else's disgust, we need a mirror neuron system that allows us to simulate the experience of disgust in ourselves.

Similarly, Rizzolatti concludes, there is evidence for such mirror neuron processes for all of the primary human emotions--anger, sadness, surprise, enjoyment, contempt, disgust, shame, and fear--that are universal to the human species.

Rizzolatti infers that the emotional neuron system is a necessary condition for empathy (or what Hume, Smith, and Darwin would call "sympathy"). To empathize with others, we must share their emotions. But while this is necessary, it is not sufficient for active empathy expressed as caring for others. Understanding someone else's pain is not the same as feeling compassion for that person. After all, a sadist understands his victim's pain and enjoys it!

Rizzolatti writes: "Compassion depends on many factors other than the recognition of pain; just to name a few: who the other person is, what our relationship with him is, whether or not we are able to imagine ourselves in his position, whether we want to assume responsibility for his emotive state, wishes and expectations, and so on. If it is someone we know and love, the emotive mirroring caused by the sight of their plight may provoke our pity or compassion; if on the other hand, the person is an enemy or is doing something that constitutes a threat for us, of if we are declared sadists, then the situation changes radically. In all these cases, we understand the other's pain, but we do not necessarily experience empathy" (2008, 191).

So here we see the moral ambiguity of our capacity for empathy or sympathy as rooted in neural processes like mirror neurons. On the one hand, having evolved as social animals, we can extend our empathy to our fellow human beings because our minds are "mirrors to one another." On the other hand, having evolved a tribal sociality based on in-group/out-group distinctions, our empathy tends to favor those we identify as friends over those we identify as enemies.

This goes far to explain both the power and the weakness of a cosmopolitan morality of human rights.