FIGURE 8–3. Human brain, showing the major cortical regions that regulate aggression
Source: 3D Brain Illustration by AXS Biomedical Animation Studio, created for Dolan DNA Learning Center.
Though Gage’s senses, memories, and movement were intact, it soon became clear that the damaged parts of his brain had been doing something important. Here is how his physician described the change:The equilibrium or balance, so to speak, between his intellectual faculties and animal propensities, seems to have been destroyed. He is fitful, irreverent, indulging at times in the grossest profanity (which was not previously his custom), manifesting but little deference for his fellows, impatient of restraint or advice when it conflicts with his desires, at times pertinaciously obstinate, yet capricious and vacillating, devising many plans of future operations, which are no sooner arranged than they are abandoned in turn for others appearing more feasible. A child in his intellectual capacity and manifestations, he has the animal passions of a strong man. Previous to his injury, although untrained in the schools, he possessed a well-balanced mind, and was looked upon by those who knew him as a shrewd, smart businessman, very energetic and persistent in executing all his plans of operation. In this regard his mind was radically changed, so decidedly that his friends and acquaintances said he was “no longer Gage.”60
FIGURE 8–4. Human brain, medial view
Source: 3D Brain Illustration by AXS Biomedical Animation Studio, created for Dolan DNA Learning Center.
Though Gage eventually recovered much of his equipoise, and the story has been embellished and sometimes garbled in generations of retelling to introductory psychology students, today our understanding of the function of the orbital cortex is broadly consistent with the doctor’s description.
The orbital cortex is strongly connected to the amygdala, hypothalamus, and other parts of the brain involved with emotion.61 It is suffused with neurons that use dopamine as their neurotransmitter and that are connected to the Seeking system in the striatum. It is adjacent to an island of cortex called the insula, the front of which just barely peeks out from beneath the Sylvian fissure in figure 8–3; the rest of the insula extends back under that fissure, obscured by overhanging flaps of the frontal and temporal lobes. The insula registers our physical gut feelings, including the sensation of a distended stomach and other inner states like nausea, warmth, a full bladder, and a pounding heart. The brain takes metaphors like “that makes my blood boil” and “his behavior disgusts me” literally. The cognitive neuroscientist Jonathan Cohen and his team found that when a person feels he is getting a raw deal from another person who is dividing a windfall between them, the insula is fired up. When the stingy allocation is thought to come from a computer, so there’s no one to get mad at, the insula remains dark.62
The orbital cortex resting on the eyeballs (figure 8–3) and the ventromedial cortex facing inward (figure 8–4) are, as mentioned, adjacent, and it’s not easy to distinguish what they do, which is why neuroscientists often lump them together. The orbital cortex seems to be more involved with determining whether an experience is pleasant or unpleasant (befitting its position next to the insula, with its input from the viscera), while the ventromedial cortex is more involved with determining whether you are getting what you want and avoiding what you don’t want (befitting its position along the midline of the brain, where the Seeking circuit extends).63 The distinction may carry over to a difference in the moral realm between an emotional reaction to a harm, and judgment and reflection on it. But the dividing line is fuzzy, and I’ll continue to use “orbital” to refer to both parts of the brain.
The inputs to the orbital cortex—gut feelings, objects of desire, and emotional impulses, together with sensations and memories from other parts of the cortex—allow it to serve as the regulator of emotional life. Visceral feelings of anger, warmth, fear, and disgust are combined with the person’s goals, and modulating signals are computed and sent back down to the emotional structures from which they originated. Signals are also sent upward to regions of the cortex that carry out cool deliberation and executive control.
This flowchart suggested by the neuroanatomy corresponds fairly well with what psychologists see in the clinic and lab. Making allowances for the difference between the flowery language of medical reports in the 19th century and the clinical jargon of the 21st, today’s descriptions of patients with damage to their orbital cortex could have applied to Phineas Gage: “Disinhibited, socially inappropriate, susceptible to misinterpreting others’ moods, impulsive, unconcerned with the consequences of their actions, irresponsible in everyday life, lacking in insight into the seriousness of their condition, and prone to weak initiative.”64
The psychologists Angela Scarpa and Adrian Raine offer a similar list, but with an additional symptom at the end that is relevant to our discussion: “Argumentativeness, lack of concern for consequences of behavior, loss of social graces, impulsivity, distractibility, shallowness, lability, violence.”65 The extra noun came from Raine’s own studies, which, instead of selecting patients with orbital brain damage and then examining their personalities, selected people prone to violence and then examined their brains. He focused on people with antisocial personality disorder, defined by the American Psychiatric Association as “a pervasive pattern of disregard for, and violation of, the rights of others,” including lawbreaking, deceit, aggressiveness, recklessness, and lack of remorse. People with antisocial personality disorder make up a large proportion of violent felons, and a subset of them, who possess glibness, narcissism, grandiosity, and a superficial charm, are called psychopaths (or sometimes sociopaths). Raine scanned the brains of violence-prone people with antisocial personality disorder and found that the orbital regions were shrunken and less metabolically active, as were other parts of the emotional brain, including the amygdala.66 In one experiment, Raine compared the brains of prisoners who had committed an impulsive murder with those who had killed with premeditation. Only the impulsive murderers showed a malfunction in their orbital cortex, suggesting that the self-control implemented by this part of the brain is a major inhibitor of violence.
But another part of its job description may come into play as well. Monkeys with lesions in the orbital cortex have trouble fitting into dominance hierarchies, and they get into more fights.67 Not coincidentally, humans with orbital damage are insensitive to social faux pas. When they hear a story about a woman who inadvertently disparaged a gift she received from a friend, or accidentally divulged that the friend had been excluded from a party list, the patients fail to recognize that anyone had said anything wrong, and don’t realize that the friend might have been hurt.68 Raine found that when people with antisocial personality disorder were asked to compose and deliver a speech about their own faults, which for ordinary people is a nerve-racking ordeal accompanied by embarrassment, shame, and guilt, their nervous systems were unresponsive.69
The orbital cortex, then (together with its ventromedial neighbor), is involved in several of the pacifying faculties of the human mind, including self-control, sympathy to others, and sensitivity to norms and conventions. For all that, the orbital cortex is a fairly primitive part of the cerebrum. We saw it in the lowly rat, and its inputs are literally and figuratively from the gut. The more deliberative and intellectual modulators of violence rely on other parts of the brain.
Consider the process of deciding whether to punish someone who has caused a harm. Our sense of justice tells us that the perpetrator’s culpability depends not just on the harm done but on his or her mental state—the mens rea, or guilty mind, that is necessary for an act to be considered a crime in most legal systems. Suppose a woman kills her husband by putting rat poison in his tea. Our decision as to whether to send her to the electric chair very much depends on whether the container she spooned it out of was mislabeled DOMINO SUGAR or correctly labeled D - CON: KILLS RATS—that is, whether she knew she was poisoning him and wanted him dead, or it was all a tragic accident. A
brute emotional reflex to the actus reus, the bad act (“She killed her husband! Shame!”), could trigger an urge for retribution regardless of her intention. The crucial role played by the perpetrator’s mental state in our assignment of blame is what makes the Moralization Gap possible. Victims insist that the perpetrator deliberately and knowingly wanted to harm them, while perpetrators insist that the harm was unintended.
The psychologists Liane Young and Rebecca Saxe put people in an fMRI scanner and had them read stories involving deliberate and accidental harms. 70 They found that the ability to exculpate harm-doers in the light of their mental state depends on the part of the brain at the junction between the temporal and parietal lobes, which is illuminated in figure 8–3 (though it’s actually the counterpart of this region in the right hemisphere that lit up in the study). The temporoparietal junction sits at a crossroads for many kinds of information, including the perception of the position of one’s own body, and the perception of the bodies and actions of other people. Saxe had previously shown that the region is necessary for the mental faculty that has been called mentalizing, intuitive psychology, and theory of mind, namely the ability to understand the beliefs and desires of another person.71
There is another kind of moral deliberation that goes beyond the gut: weighing the consequences of different courses of action. Consider the old chestnut from moral philosophy: a family is hiding from the Nazis in a cellar. Should they smother their baby to prevent it from crying and giving away their location, which would result in the deaths of everyone in the family, baby included? How about throwing a fat man in front of a runaway trolley so that his bulk will stop it before it slams into five workers on the track? A utilitarian calculus would say that both killings are permissible, because they would sacrifice one life to save five. Yet many people would balk at smothering the baby or heaving the fat man, presumably because they have a visceral reaction against harming an innocent person with their bare hands. In a logically equivalent dilemma, a bystander to the runaway trolley could save the five workers by diverting it onto a side track, where it would kill just one. In this version, everyone agrees that it’s permissible to throw the switch and save five lives at a cost of one, presumably because it doesn’t feel like you’re really killing anyone; you’re just failing to prevent the trolley from doing it.72
The philosopher Joshua Greene, working with Cohen and others, has shown that the visceral reaction against smothering the baby or throwing the man in front of the train comes from the amygdala and orbital cortex, whereas the utilitarian thinking that would save the greatest number of lives is computed in a part of the frontal lobe called the dorsolateral prefrontal cortex, also illuminated in figure8–3.73 The dorsolateral cortex is the part of the brain that is most involved in intellectual, abstract problem-solving—it lights up, for example, when people do the problems on an IQ test. 74 When people consider the case of the crying baby in the cellar, both their orbital cortex (which reacts to the horror of smothering the baby) and their dorsolateral cortex (which calculates lives saved and lost) light up, together with a third part of the brain that deals with conflicting impulses—the anterior cingulate cortex in the medial wall of the brain, shown in figure 8–4. The people who deduce that it’s all right to smother the baby show greater activation in the dorsolateral cortex.
The temporoparietal junction and dorsolateral prefrontal cortex, which grew tremendously over the course of evolution, give us the wherewithal to perform cool calculations that deem certain kinds of violence justifiable. Our ambivalence about the outputs of those calculations—whether smothering the baby should be thought of as an act of violence or an act that prevents violence—shows that the quintessentially cerebral parts of the cerebrum are neither inner demons nor better angels. They are cognitive tools that can both foster violence and inhibit it, and as we shall see, both powers are exuberantly employed in the distinctively human forms of violence.
My brief tour of the neurobiology of violence barely does justice to our scientific understanding, and our scientific understanding barely does justice to the phenomena themselves. But I hope it has persuaded you that violence does not have a single psychological root but a number of them, working by different principles. To understand them, we need to look not just at the hardware of the brain but also at its software—that is, at the reasons people engage in violence. Those reasons are implemented as intricate patterns in the microcircuitry of brain tissue; we cannot read them directly from the neurons, any more than we can understand a movie by putting a DVD under a microscope. So the remainder of the chapter will shift to the bird’s-eye view of psychology, while connecting the psychological phenomena to the neuroanatomy.
There are many taxonomies of violence, and they tend to make similar distinctions. I will adapt a four-part scheme from Baumeister, splitting one of his categories in two.75
The first category of violence may be called practical, instrumental, exploitative, or predatory. It is the simplest kind of violence: the use of force as a means to an end. The violence is deployed in pursuit of a goal such as greed, lust, or ambition, which is set up by the Seeking system, and it is guided by the entirety of the person’s intelligence, for which the dorsolateral prefrontal cortex is a convenient symbol.
The second root of violence is dominance—the drive for supremacy over one’s rivals (Baumeister calls it “egotism”). This drive may be tied to the testosterone-fueled Dominance or Intermale Aggression system, though it is by no means confined to males, or even to individual people. As we shall see, groups compete for dominance too.
The third root of violence is revenge—the drive to pay back a harm in kind. Its immediate engine is the Rage system, but it can recruit the Seeking system to its cause as well.
The fourth root is sadism, the joy of hurting. This motive, puzzling and horrifying in equal measure, may be a by-product of several quirks of our psychology, particularly the Seeking system.
The fifth and most consequential cause of violence is ideology, in which true believers weave a collection of motives into a creed and recruit other people to carry out its destructive goals. An ideology cannot be identified with a part of the brain or even with a whole brain, because it is distributed across the brains of many people.
PREDATION
The first category of violence is not really a category at all, because its perpetrators have no destructive motive like hate or anger. They simply take the shortest path to something they want, and a living thing happens to be in the way. At best it is a category by exclusion: the absence of any inhibiting factor like sympathy or moral concern. When Immanuel Kant stated the second formulation of his Categorical Imperative—that an act is moral if it treats a person as an end in itself and not as a means to an end—he was in effect defining morality as the avoidance of this kind of violence.
Predation may also be called exploitative, instrumental, or practical violence.76 It coincides with Hobbes’s first cause of quarrel: to invade for gain. It is Dawkins’s survival machine treating another survival machine as a part of its environment, like a rock or a river or a lump of food. It is the interpersonal equivalent of Clausewitz’s dictum that war is merely the continuation of policy by other means. It is Willie Sutton’s answer to the question of why he robbed banks: “Because that’s where the money is.” It lies beneath the advice of a farmer to increase a horse’s efficiency by castrating it with two bricks. When asked, “Doesn’t that hurt,” the farmer replies, “Not if you keep your thumbs out of the way.”77
Because predatory violence is just a means to a goal, it comes in as many varieties as there are human goals. The paradigm case is literal predation—hunting for food or sport—because it involves no animosity toward the victim. Far from hating their quarry, hunters valorize and totemize them, from Paleolithic cave paintings to trophies above the mantels in gentlemen’s clubs. Hunters may even empathize with their prey—proof that empathy alone is not a bar to violence. The ecologist Louis Liebenberg stu
died the remarkable ability of the !Kung San to infer the whereabouts and physical condition of their game from a few faint tracks as they pursue them across the Kalahari Desert.78 They do it with empathy—putting themselves in the hooves of the animal and imagining what it is feeling and where it is tempted to flee. There may even be an element of love. One night after the ninth inning of a baseball game, I was too comatose to get off the couch or even change the channel and passively watched the following program on the cable sports network. It was a show about fishing, and consisted entirely of footage of a middle-aged man in an aluminum boat on a nondescript stretch of water pulling in one large bass after another. With each catch he brought the fish close to his face and stroked it, making little kissy noises and cooing, “Ooh, aren’t you a beauty! You’re a pretty one! Yes, you are!”
The chasm between the perpetrator’s perspective—amoral, pragmatic, even frivolous—and the victim’s is nowhere wider than in our predation of animals. It’s safe to say that the bass, if given the chance, would not reciprocate the fisherman’s affection, and most people would not want to know the opinion of a broiler chicken or a live lobster on whether the mild pleasure we get from eating their flesh rather than a plate of eggplant justifies the sacrifice they will make. The same incuriosity enables coldhearted predatory violence against humans.
The Better Angels of Our Nature: Why Violence Has Declined Page 75
