The Better Angels of Our Nature: Why Violence Has Declined

by Steven Pinker

  Baumeister, with psychological spectacles still affixed, calls this the myth of pure evil. The mindset that we adopt when we don moral spectacles is the mindset of the victim. Evil is the intentional and gratuitous infliction of harm for its own sake, perpetrated by a villain who is malevolent to the bone, inflicted on a victim who is innocent and good. The reason that this is a myth (when seen through psychological spectacles) is that evil in fact is perpetrated by people who are mostly ordinary, and who respond to their circumstances, including provocations by the victim, in ways they feel are reasonable and just.

  The myth of pure evil gives rise to an archetype that is common in religions, horror movies, children’s literature, nationalist mythologies, and sensationalist news coverage. In many religions evil is personified as the Devil—Hades, Satan, Beelzebub, Lucifer, Mephistopheles—or as the antithesis to a benevolent God in a bilateral Manichean struggle. In popular fiction evil takes the form of the slasher, the serial killer, the bogeyman, the ogre, the Joker, the James Bond villain, or depending on the cinematic decade, the Nazi officer, Soviet spy, Italian gangster, Arab terrorist, inner-city predator, Mexican druglord, galactic emperor, or corporate executive. The evildoer may enjoy money and power, but these motives are vague and ill formed; what he really craves is the infliction of chaos and suffering on innocent victims. The evildoer is an adversary—the enemy of good—and the evildoer is often foreign. Hollywood villains, even if they are stateless, speak with a generic foreign accent.

  The myth of pure evil bedevils our attempt to understand real evil. Because the standpoint of the scientist resembles the standpoint of the perpetrator, while the standpoint of the moralizer resembles the standpoint of the victim, the scientist is bound to be seen as “making excuses” or “blaming the victim,” or as trying to vindicate the amoral doctrine that “to understand all is to forgive all.” (Recall Lewis Richardson’s reply that to condemn much is to understand little.) The accusation of relativizing evil is particularly likely when the motive the analyst imputes to the perpetrator appears to be venial, like jealousy, status, or retaliation, rather than grandiose, like the persistence of suffering in the world or the perpetuation of race, class, or gender oppression. It is also likely when the analyst ascribes the motive to every human being rather than to a few psychopaths or to the agents of a malignant political system (hence the popularity of the doctrine of the Noble Savage). The scholar Hannah Arendt, in her writings on the trial of Adolf Eichmann for his role in organizing the logistics of the Holocaust, coined the expression “the banality of evil” to capture what she saw as the ordinariness of the man and the ordinariness of his motives.42 Whether or not she was right about Eichmann (and historians have shown that he was more of an ideological anti-Semite than Arendt allowed), she was prescient in deconstructing the myth of pure evil. 43 As we shall see, four decades of research in social psychology—some of it inspired by Arendt herself—have underscored the banality of most of the motives that lead to harmful consequences.44

  In the rest of this chapter I’ll lay out the brain systems and motives that incline us toward violence, while trying to identify the inputs that ramp them up or down and thereby offer insight into the historical decline of violence. Appearing to take the perspective of the perpetrator is just one of the dangers that attends this effort. Another is the assumption that nature organized the brain into systems that are morally meaningful to us, such as ones that lead to evil and ones that lead to good. As we shall see, some of the dividing lines between the inner demons of this chapter and the better angels of the next were guided as much by expository convenience as by neurobiological reality, because certain brain systems can cause both the best and the worst in human behavior.

  ORGANS OF VIOLENCE

  One of the symptoms of the myth of pure evil is to identify violence as an animalistic impulse, as we see in words like beastly, bestial, brutish, inhuman, and wild, and in depictions of the devil with horns and a tail. But while violence is certainly common in the animal kingdom, to think of it as arising from a single impulse is to see the world through a victim’s eyes. Consider all the destructive things that members of our species do to ants. We eat them, poison them, accidentally trample them, and deliberately squish them. Each category of formicide is driven by an utterly distinct motive. But if you were an ant, you might not care about these fine distinctions. We are humans, so we tend to think that the terrible things that humans do to other humans come from a single, animalistic motive. But biologists have long noted that the mammalian brain has distinct circuits that underlie very different kinds of aggression.

  The most obvious form of aggression in the animal kingdom is predation. Hunters such as hawks, eagles, wolves, lions, tigers, and bears adorn the jerseys of athletes and the coats of arms of nations, and many writers have blamed human violence, as William James did, on “the carnivore within.” Yet biologically speaking, predation for food could not be more different from aggression against rivals and threats. Cat people are well aware of the distinction. When their animal companion sets its sights on a beetle on the floorboards, it is crouched, silent, and intently focused. But when one alley cat faces off against another, the cat stands tall, fur erect, hissing and yowling. We saw how neuroscientists can implant an electrode into the Rage circuit of a cat, press a button, and set the animal on attack mode. With the electrode implanted in a different circuit, they can set it on hunting mode and watch in amazement as the cat quietly stalks a hallucinatory mouse.45

  Like many systems in the brain, the circuits that control aggression are organized in a hierarchy. Subroutines that control the muscles in basic actions are encapsulated in the hindbrain, which sits on top of the spinal cord. But the emotional states that trigger them, such as the Rage circuit, are distributed higher up in the midbrain and forebrain. In cats, for example, stimulating the hindbrain can activate what neuroscientists call sham rage. The cat hisses, bristles, and extends its fangs, but it can be petted without it attacking the petter. If, in contrast, they stimulate the Rage circuit higher up, the resulting emotional state is no sham: the cat is mad as hell and lunges for the experimenter’s head.46 Evolution takes advantage of this modularity. Different mammals use different body parts as offensive weapons, including jaws, fangs, antlers, and in the case of primates, hands. While the hindbrain circuits that drive these peripherals can be reprogrammed or swapped out as a lineage evolves, the central programs that control their emotional states are remarkably conserved.47 That includes the lineage leading to humans, as neurosurgeons discovered when they found a counterpart to the Rage circuit in the brains of their patients.

  Figure 8–1 is a computer-generated model of the brain of a rat, facing left. A rat is a sniffy little animal that depends on its sense of smell, and so it has enormous olfactory bulbs, which have been amputated from the left-hand side of the model to leave room for the rest of the brain in the picture. And like all quadrupeds, the rat is a horizontal creature, so what we think of as the “higher” and “lower” levels of the nervous system are really laid out front to back, with the rat’s high-level cogitation, such as it is, located at the front (left) end of the model and the control of the body at the rear (right), extending into the spinal cord, which would spill out of the right edge of the picture if it were shown.

  FIGURE 8–1. Rat brain, showing the major structures involved in aggression Source: Image derived from the Allen Mouse Brain Atlas, http://mouse.brain-map.org.

  The Rage circuit is a pathway that connects three major structures in the lower parts of the brain.48 In the midbrain there is a collar of tissue called the periaqueductal gray—“gray” because it consists of gray matter (a tangle of neurons, lacking the white sheaths that insulate output fibers), “periaqueductal” because it surrounds the aqueduct, a fluid-filled canal that runs the length of the central nervous system from the spinal cord up to large cavities in the brain. The periaqueductal gray contains circuits that control the sensorimotor components of rage. The
y get inputs from parts of the brain that register pain, balance, hunger, blood pressure, heart rate, temperature, and hearing (particularly the shrieks of a fellow rat), all of which can make the animal irritated, frustrated, or enraged. Their outputs feed the motor programs that make the rat lunge, kick, and bite.49 One of the oldest discoveries in the biology of violence is the link between pain or frustration and aggression. When an animal is shocked, or access to food is taken away, it will attack the nearest fellow animal, or bite an inanimate object if no living target is available.50

  The periaqueductal gray is partly under the control of the hypothalamus, a cluster of nuclei that regulate the animal’s emotional, motivational, and physiological state, including hunger, thirst, and lust. The hypothalamus monitors the temperature, pressure, and chemistry of the bloodstream and sits on top of the pituitary gland, which pumps hormones into the bloodstream that regulate, among other things, the release of adrenaline from the adrenal glands and the release of testosterone and estrogen from the gonads. Two of its nuclei, the medial and ventrolateral, are parts of the Rage circuit. “Ventral” refers to the belly side of the animal, as opposed to its “dorsal” or back side. The terms were grandfathered over to the human brain as it evolved its perpendicular perch atop a vertical body, so in the human brain “ventral” points to our feet and “dorsal” to the top of our scalp.

  Modulating the hypothalamus is the amygdala, Latin for “almond,” the shape it takes in the human brain. The amygdala is a small, multipart organ connected to brain systems for memory and motivation. It applies the emotional coloring to our thoughts and memories, particularly fear. When an animal has been trained to expect a shock after a tone, the amygdala helps to store the connections that give the tone its aura of anxiety and dread. The amygdala also lights up at the sight of a dangerous predator or of a threatening display from a member of the same species. In the case of humans, for example, the amygdala responds to an angry face.

  And sitting on top of the entire Rage circuit is the cerebral cortex—the thin layer of gray matter on the outer surface of the cerebral hemispheres where the computations behind perception, thinking, planning, and decision-making are carried out. Each cerebral hemisphere is divided into lobes, and the one at the front, the frontal lobe, computes decisions relevant to how to behave. One of the major patches of the frontal lobes sits on top of the eye sockets in the skull, also known as orbits, so it is called the orbitofrontal cortex, orbital cortex for short.51 The orbital cortex is densely connected to the amygdala and other emotional circuits, and it helps integrate emotions and memories into decisions about what to do next. When the animal modulates its readiness to attack in response to the circumstances, including its emotional state and any lessons it has learned in the past, it is this part of the brain, behind the eyeballs, that is responsible. By the way, though I have described the control of rage as a topdown chain of command—orbital cortex to amygdala to hypothalamus to periaqueductal gray to motor programs—the connections are all two-way: there is considerable feedback and cross talk among these components and with other parts of the brain.

  As I mentioned, predation and rage play out very differently in the behavioral repertoire of a carnivorous mammal and are triggered by electrical stimulation of different parts of the brain. Predation involves a circuit that is part of what Panksepp calls the Seeking system.52A major part of the Seeking system runs from a part of the midbrain (not shown in figure 8–1) via a bundle of fibers in the middle of the brain (the medial forebrain bundle) to the lateral hypothalamus, and from there up to the ventral striatum, a major part of the so-called reptilian brain. The striatum is composed of many parallel tracts (giving it a striated appearance), and it is buried deep in the cerebral hemispheres and densely connected to the frontal lobes.

  The Seeking system was discovered when the psychologists James Olds and Peter Milner implanted an electrode into the middle of a rat brain, hooked it up to a lever in a Skinner box, and found that the rat would press the lever to stimulate its own brain until it dropped of exhaustion.53 Originally they thought they had found the pleasure center in the brain, but neuroscientists today believe that the system underlies wanting or craving rather than actual pleasure. (The major realization of adulthood, that you should be careful about what you want because when you get it you may not enjoy it, has a basis in the anatomy of the brain.) The Seeking system is held together not just by wiring but by chemistry. Its neurons signal to each other with a neurotransmitter called dopamine. Drugs that make dopamine more plentiful, like cocaine and amphetamines, jazz the animal up, while drugs that decrease it, like antipsychotic medications, leave the animal apathetic. (The ventral striatum also contains circuits that respond to a different family of transmitters, the endorphins or endogenous opiates. These circuits are more closely related to enjoying a reward once it arrives than to craving it in anticipation.)

  The Seeking system identifies goals for the animal to pursue, like access to a lever that it may press to receive food. In more natural settings, the Seeking system motivates a carnivorous animal to hunt. The animal stalks its quarry in what we can imagine is a state of pleasant anticipation. If successful, it dispatches the prey in a quiet bite that is completely unlike the snarling attack of rage.

  Animals can attack both in offense and in defense.54 The simplest trigger of an offensive attack is sudden pain or frustration, the latter delivered as a signal from the Seeking system. The reflex may be seen in some of the primitive responses of a human being. Babies react with rage when their arms are suddenly pinned at their sides, and adults may lash out by swearing or breaking things when they hit their thumb with a hammer or are surprised by not getting what they expect (as in the technique of computer repair called percussive maintenance). Defensive attacks, which in the rat consist of lunging at the head of an adversary rather than kicking and biting its flank, are triggered by yet another brain system, the one that underlies fear. The Fear system, like the Rage system, consists of a circuit that runs from the periaqueductal gray through the hypothalamus to the amygdala. The Fear and Rage circuits are distinct, connecting different nuclei in each of these organs, but their physical proximity reflects the ease with which they interact.55 Mild fear can trigger freezing or flight, but extreme fear, combined with other stimuli, can trigger an enraged defensive attack. Forward panic or rampage in humans may involve a similar handoff from the Fear system to the Rage system.

  Panksepp identifies a fourth motivational system in the mammalian brain that can trigger violence; he calls it the Intermale Aggression or Dominance system.56 Like Fear and Rage, it runs from the periaqueductal gray through the hypothalamus to the amygdala, connecting yet another trio of nuclei along the way. Each of these nuclei has receptors for testosterone. As Panskepp notes, “In virtually all mammals, male sexuality requires an assertive attitude, so that male sexuality and aggressiveness normally go together. Indeed, these tendencies are intertwined throughout the neuroaxis, and to the best of our limited knowledge, the circuitry for this type of aggression is located near, and probably interacts strongly with, both Rage and Seeking circuits.”57 To psychologize the anatomy, the Seeking system leads a male to willingly, even eagerly, seek out an aggressive challenge with another male, but when the battle is joined and one of them is in danger of defeat or death, focused fighting may give way to blind rage. Panksepp notes that the two kinds of aggression, though they interact with each other, are neurobiologically distinct. When certain parts of the medial hypothalamus or striatum are damaged, the animal is more likely to attack a prey animal or an unwitting experimenter, but less likely to attack another male. And as we shall see, giving an animal (or a man) testosterone does not make him testy across the board. On the contrary, it makes him feel great, while putting a chip on his shoulder when he is faced with a rival male.58

  One look at a human brain and you know you are dealing with a very unusual mammal. Figure 8–2, with its transparent cortex, shows that all the parts of the r
at brain have been carried over to the human brain, including the organs that house the circuits for rage, fear, and dominance: the amygdala, the hypothalamus, and the periaqueductal gray (which is found inside the midbrain, lining the cerebrospinal canal running through it). The dopaminefueled striatum, whose ventral portion helps set goals for the whole brain to seek, is also prominent.

  FIGURE 8–2. Human brain, showing the major subcortical structures involved in aggression

  Source: 3D Brain Illustration by AXS Biomedical Animation Studio, created for Dolan DNA Learning Center.

  But while these structures take up a large proportion of the rat brain, in the human brain they are enveloped by a bloated cerebrum. As figure 8–3 shows, the outsize cerebral cortex has been wrinkled like a wad of newspaper to get it to fit inside the skull. A large part of the cerebrum is taken up by the frontal lobes, which in this view of the brain extend about three-quarters of the way back. The neuroanatomy suggests that in Homo sapiens primitive impulses of rage, fear, and craving must contend with the cerebral restraints of prudence, moralization, and self-control—though as in all attempts at taming the wild, it’s not always clear who has the upper hand.

  Within the frontal lobes, one can readily see how the orbital cortex got its name: it is a big spherical dent that accommodates the bony socket of the eye. Scientists have known that the orbital cortex is involved with regulating the emotions since 1848, when a railroad foreman named Phineas Gage tamped down some blasting powder in a hole in a rock and ignited an explosion that sent the tamping iron up through his cheekbone and out the top of his skull. 59 A 20th-century computer reconstruction based on the holes in the skull suggest that the spike tore up his left orbital cortex, together with the ventromedial cortex on the inside wall of the cerebrum. (It is visible in the medial view of the brain in figure 8–4.) The orbital and ventromedial cortex are continuous, wrapping around the bottom edge of the frontal lobe, and neuroscientists often use either term to refer to the combination of the two of them.