Empathy draws on both mammalian circuits that we share with other animals and cognitive abilities that only appear to be present in our closest relatives, the great apes and and cetaceans, and ourselves. As with happiness and self-control, there is strong evidence that differences in our capacity for compassion and empathy are tied to differences in the brain structures and neurochemistries that they depend on.
In this series:
To feel much for others and little for ourselves, that to restrain our selfish, and to indulge our benevolent affections, constitutes the perfection of human nature; and can alone produce among mankind that harmony of sentiments and passions in which consists their whole grace and propriety.
–Adam Smith, The Theory of Moral Sentiments pt i, ch i (1759)
The language of virtue and character has been in decline for at least a century, with the exception of the prosocial traits like kindness, fairness and compassion. The rise of the value on caring can be seen for instance in a study done on the frequency of virtue terms in books since 1900.  Three quarters of the terms, like virtue or character, declined in frequency, while compassion, fairness, tolerance and selflessness were among the few that become more common. This is probably due to the spread of Enlightenement thought, which values caring and fairness over obedience to authority, self-control, in-group loyalty and deference to religion, as I will discuss in relation to Jon Haidt’s work in the next essay.
As a result, in cultures influenced by the Enlightenment, caring for others has become almost synonymous with morality. In 2014 a large multinational team surveyed 2800 students from fourteen countries, and asked them to rate the importance of different virtues. The only virtues that made it to the top of the list in all fourteen countries were the prosocial ones, honesty, respect and kindness.
Selection for Altruism The existence of altruistic behavior in non-human animals has long been a puzzle to evolutionary biologists. Following Darwin and Dawkins they insisted that organisms are simply mechanisms for reproducing their own genes, so at best altruism was some kind of calculation on the part of genetics about the replication of the organism’s or its closely related genes. Putatively altruistic behavior might in fact be a selfish way of increasing social capital and future reproductive success. Or a suicidal sacrifice might be genes calculating that dying to save three siblings or half a dozen cousins is actually a statistically better deal.
But this dogma didn’t do much to explain non-genetically related altruism, and is now giving way to more acknowledgement of the mechanisms of “group selection,” natural selection at the level of groups. Genes for empathetic, altruistic and cooperative neurological mechanisms and behaviors increased the evolutionary fitness of the groups they belonged to, even if they didn’t increase the likelihood of that particular self-sacrificing animal reproducing.
Emotional Empathy and Mirror Neurons Research on rodents and primates suggests that at least one of these genetically-enabled empathic mechanisms is mirror neurons. Mirror neurons trigger sympathetic feelings in the parts of our brains that process touch, emotions, and actions when we observe those sensations, feelings or actions in others. Human babies are distressed by seeing or hearing other infants cries, and, when they are able to, they try to comfort them. They not only trigger sympathetic joy and distress when observing related animals of your own species, but probably also facilitate learning useful new behaviors through copying. These neurons are thought to help bond infants to their mothers by imitating facial expressions, and the imitative success of a newborn predicts their later emotional and cognitive development.
Cognitive Empathy and Theory of Mind The more recent (50-100 thousand years old) cognitive architecture that empathy relies on is the prefrontal cortex’s ability to generate a model of what other people are thinking and feeling, a “theory of mind” (ToM). ToM is the result of a learning process about the relationship of other people’s experience and its relationship to one’s own. This is sometimes called “cognitive empathy” to distinguish it from the more primitive forms of empathetic distress and mirror neuron facilitated “emotional empathy”.
The brain systems for emotive and cognitive empathy dynamically interact in most people to generate empathy and compassion. We can react viscerally to a scene in a movie in which someone is injured, while cognitively our empathy is tempered by knowing that no one was really hurt. Or we can cognitively understand that someone has suffered a tragedy even if they display no emotion to trigger our visceral reactions. We can also use cognitive empathy to generate compassion for people and animals that are very different from us, or that we can’t see. Among the many effects of autism are impairments in the development of theory of mind and cognitive empathy; autists are just as emotionally responsive as “neurotypicals” but have a hard time understanding and predicting the feelings of others. Psychopathy, on the other hand, is more a dysfunction of emotional empathy and the amygdala; psychopaths understand and can predict the emotions of others just fine, they just aren’t motivated to care about them. A recent meta-analysis of 38 studies found that the amount of both cognitive and emotive empathy independently predicts criminal offending (although it is important to note that psychopathy is a predictor of criminal behavior while autism is not).
Oxytocin Emotional empathy, cognitive empathy and prosocial behavior are all moderately to highly inheritable according a recent review of evidence by Chakrabarti and Baron-Cohen, with emotional empathy having the strongest genetic correlates. One of the nine candidate genetic variations Chakrabarti and Baron-Cohen identify as linked to differences in empathy are genes that determine how much of the neurochemical oxytocin is produced in the brain. Oxytocin is boosted naturally in the body when mothers interact with infants, stimulating the flow of breast milk, and during sex. Oxytocin enhances parts of the brain that attend to other people’s faces and emotions, and boosts the connection between the amygdala and the prefrontal cortex. Variations in oxytocin genes, and the amount of oxytocin in the brain, are associated with differences in both emotional and cognitive empathy, prosocial behaviors, facial and emotional recognition skills, the personality trait of extraversion and the incidence of autism  and psychopathic callousness .
Because it is a safe and easily administered chemical, hundreds of experiements have been done on the behavioral and neurological effects of snorting oxytocin. Oxytocin enhancement generally increases interpersonal attentivenes, trust, constructive communication and prosocial behavior, at least between relatives and other in-group members. Oxytocin enhancement makes other people appear more attractive, and improves men’s sexual performance. Married men given oxytocin get more rewards from their brain when looking at images of their wives’ faces, and oxytocin also enhances positive feelings of parents towards infants. Oxytocin therapy is finding some moderate success as a treatment for autistic children’s attentiveness to faces and emotions.
Testosterone Genes that control testosterone are also identified by Chakrabarti and Baron-Cohen as linked to empathy. One theory about the etiology of autism is that it is Extreme Male Brain, triggered by exposure to high levels of testosterone during fetal development. Levels of testosterone are also linked to aggression, perception of threats and dominance behavior, and the levels of testosterone have declined in the human species over the last 200,000 years contributing to a decline in violence. The effects of testosterone are still poorly understood however. One study found for instance, that giving doses of testosterone to women and to men with low prenatal testosterone increased their cooperative behavior. 
Serotonin A third set of genes linked to empathy code for the production of serotonin. The more serotonin people have the more they empathize with other people’s emotions, and variations in serotonin genes are associated with prosocial behavior because serotonin boosts the threat people feel from others’ distress.  Boosting serotonin with SSRIs reduces the willingness to punish others in games.
Personality: Agreeableness These differences in prosocial brain structure and neurochemistry presumably underlie our personality settings for agreeableness and willingness to cooperate. The personality trait of agreeableness has been identified in chimpanzees, suggesting that we share these neurological variations in empathy and sociability settings. People who score high on agreeableness are more empathetic, trusting and prosocial throughout their lives.
Part Two will be published Monday
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