FOUR

THE SCIENCE OF MAD

“Revenge is sweeter far than flowing honey,” Homer wrote. Lord Byron wrote, “Sweet is revenge.” Both of these men were in good company when it came to adopting the sweetness of revenge as a literary metaphor. Recited in so many poems, plays, novels, and screenplays, and given its sugary properties, “revenge is sweet” has by now become the kind of cliché that causes cavities.

Shakespeare, too, saw revenge as synonymous with food. “I will feed the ancient grudge I bear him. . . . If it will feed nothing else, it will feed my revenge,” so says Shylock in The Merchant of Venice.

“Revenge is a dish best served cold.” Or so goes the proverbial maxim that is referenced in the novel The Godfather and the films Kill Bill, vol. 1, and Star Trek II: The Wrath of Khan. It is often attributed to the American writer Dorothy Parker, although its origins date back to an 1841 French novel by Marie-Joseph (Eugène) Sue. Tony Soprano, the Mafia chieftain from The Sopranos who was no stranger to food, once mangled the phrase by saying, “Revenge is like serving cold cuts.”

Many people say, “I want to taste my revenge” or, even, “I won’t be satisfied until I have my revenge,” with satisfaction spoken of in the same way as the alleviation of hunger.

What is it with revenge and food? Those who insist on taking too much revenge, who ignore the law of the talion, who exceed their entitlement and overfill on revenge beyond the point of satisfaction can be described as revenge gluttons. Alfred Hitchcock once said, “Revenge is sweet and not fattening.” That actually may not be so true after all.

Dr. Eddie Harmon-Jones, a neuroscientist at the University of Wisconsin, using sophisticated brain-wave technology, discovered that when people anticipate the taking of revenge after having been insulted or injured, the left prefrontal cortex of their brains is activated in the same manner as when they are about to satisfy their cravings for food.1 The left prefrontal cortex can’t distinguish between food and justice—each sustains life, both are equally anticipated and subject to the same cravings.

So revenge, in fact, is sweet, and buttery, and flavorful, and perhaps even irresistible. A literary metaphor is without meaning if the association it draws on doesn’t ring true—or, in this case, taste great. “Revenge is like a baby’s sweet smile,” or “revenge is like a golden sunrise,” or “revenge is like a woman’s supple caress”—none of these phrases resonate as recognizable substitutes for revenge. Not even Lord Byron could turn these forced descriptions into poetry. For thousands of years artists have pegged revenge as having the same allure as a special taste. Vengeance and nourishment are like siblings of the soul—both satisfy cravings, both feel so good until taken to excess. Getting sick to one’s stomach can arise equally from ravenous food intake as well as the taking of disproportionate revenge.

The visceral connection between vengeance and food has always been obvious, which is why so many poets throughout history and across all cultures mined the same metaphor. With the assistance of modern science, however, we now know that food cravings and vengeance are actually neural roommates, sharing space in the same sector of the human brain. “Revenge is sweet” is both visceral and cognitive. The biological link has always been there. Nature called when it came to vengeance. Human beings always felt it; we just couldn’t see it. Intuitively we knew that the revenge impulse was emotional. But that didn’t mean that the revenge experience was entirely brainless. The fact is, there is a neurological basis for why revenge is so faithfully associated with comfort food: both are satisfying and are lodged in the same region of the brain where cravings are stored.

And this presents a fundamental problem in the centuries-long crusade against revenge. The one thing that governments and organized religion never counted on was that vengeance might actually be hardwired into the human brain. Revenge is not like a bad habit, something to be licked and overcome. It is as innate to man as breathing, having sex, falling in love, and making war, which is oftentimes represented as vengeance taken against nations. These are not vices but verities. We can’t simply wish them away. And this is particularly true of revenge. It is an evolutionary principle, a mainstay of human engineering. And that’s why it has never disappeared despite society’s considerable efforts to make it go the way of the dinosaurs.

Human beings have had a long history of preserving vengeance in their lives. Revenge is in many ways the cornerstone of our evolutionary history. Why else would we silently applaud vengeance when properly exercised? Why else are vengeful feelings so pronounced when individuals are laid low, or when we witness someone getting away with having committed a wrong? Far from being a human defect, a short circuit of our anatomy, vengeance might actually be one of the clearest expressions of human nature at work. Revenge creates order out of chaos by sending a message as to how one is expected to behave in a civilized society. It also speaks directly to the deep human instinct for fairness. The bond between the evolution of humankind and its reliance on revenge is as inviolable as any other instinct of the human species.

“The urge to take revenge or punish cheaters is not a disease or a toxin or sign that something has gone wrong,” says Michael McCullough, a professor of psychology and the author of Beyond Revenge: The Evolution of the Forgiveness Instinct. “From the point of view of evolution, it’s not a problem but a solution.”2

Margaret Truman, the daughter of President Harry S. Truman, had been singing professionally since 1947, headlining at such venerable venues as the Hollywood Bowl and Carnegie Hall. She had even signed a recording contract with RCA. In December 1950, Ms. Truman was slated to perform in Constitution Hall, in the nation’s capital where her father just happened to be the occupant of the White House. It was going to be a sold-out gig in Washington, DC, in front of her parents and with the considerable advantage of a home-court crowd. Home-court advantage in all ways, except for the Washington Post.

Throughout Ms. Truman’s fledging career her audiences had generally been quite large and respectful (in the days before the Internet and TMZ, how else could citizens keep tabs on presidential offspring except by going to see them in person?), but the critical reception to her performances was usually mixed to mediocre at best. Washington’s own media, however, had yet to weigh in on the talents of the nation’s first daughter until the day after Ms. Truman performed live at Constitution Hall.

In the next morning’s Washington Post, Paul Hume, the paper’s music critic, wrote that Ms. Truman “cannot sing very well. She was flat a good deal of the time . . .” and had no “professional finish.” Ouch!

President Truman, someone who insisted that the buck always stopped at his desk and who never shied away from telling someone how he really felt, wrote Hume a letter, which the flattered critic couldn’t resist releasing to the press. He knew that this presidential blowup would make for good copy. The president wrote: “I have just read your lousy review. I have never met you, but if I do, you’ll need a new nose.” Double ouch or, touché! These words came from a Cold War president, the commander in chief over America’s fearsome nuclear arsenal—the man who actually dropped the bomb!—and someone who suddenly showed himself to be an equally combative, defensive father.

When asked about her father’s gesture on her behalf, Margaret Truman said, “I’m glad to see that chivalry is not dead.” The president’s advisers, however, were not similarly amused. In fact, they were furious that the president had now turned a mere music review into such a public fight. In their opinion, this angry, thuggish, undignified letter made Truman appear unpresidential in the eyes of his own people, and equally so in the estimation of world leaders. This was a breakout in hostilities at the lowest possible of levels. If “containment” meant anything in the nomenclature of the Cold War, it should have meant: “Contain your emotions, Harry! Save it for Korea, or Greece and Turkey, for God’s sakes.”

Surely this was not a great demonstration of the president’s judgment. How petty can the leader of the free world be? Truman’s advisers feared that the lasting impression from this regrettable piece of musical theater was that such a hotheaded father should never be allowed to have his finger on the atomic bomb. Besides, he already had enough political difficulties without now also appearing to be emotionally unstable. Truman, however, was of a very different mind as to how this was all going to play out with the general public. He reassured his advisers, “Wait till the mail comes in. I’ll make you a bet that 80 percent of it is on my side of the argument.”

A week later, the president marched his West Wing staff over to the mailroom. On Truman’s instructions, the mailroom clerk had stacked up thousands of what were now being called “Hume letters” into two piles—those in favor of their vengeful president and those against. As Truman had predicted, slightly more than 80 percent favored his defense of his daughter. He had, indeed, displayed the highest degree of fatherly chivalry from the grandest of all stages—the Oval Office. Many of these letters, in fact, came from mothers who understood exactly how he felt. They wrote that they, too, would have expected their own husbands to respond the same way, regardless of how others would have perceived it.

The president turned to his advisers and said, “The trouble with you guys is, you don’t understand human nature.”3

In Truman’s case, the father who was willing to defend the honor of his daughter played much better on Main Street than his daughter’s own singing career would have on Broadway. And his West Wing staff was clearly tone deaf when it came to anticipating public opinion. Truman came across as far more human than if he had instead exhibited the demeanor of a measured, buttoned-up, unemotional Cold War president. Remember how voters reacted to Governor Dukakis’s emotionally obtuse response to the hypothetical rape and murder of his wife, discussed in an earlier chapter? The public’s expectation is that a true man would stand up for the honor of his wife and make her murderer pay for his crime. A real father would defend his daughter. Dukakis appeared to be a first-class wimp who couldn’t get his head out of reciting his campaign’s position papers. Truman, in contrast, a true man, was perceived not as a deranged Cold War president but as a righteous father whose daughter had just been publically humiliated.

Perhaps citizens, on certain occasions, prefer to see their leaders more fatherly and less presidential—the real person over the empty suit, the emotionally honest dad over the manufactured wonk, the kind of person who doesn’t spend his day reading the polls but actually takes in his surroundings and notices that there are real people who he is morally obligated to protect. It’s worth remembering that George Washington is equally regarded as the father of the United States and its first president. And fathers have moral responsibilities to protect the honor of their children. Harry Truman never lived long enough to see this concept immortalized in The Godfather. For him it was all instinctual. What’s more, he knew that the public would appreciate this singular display of fatherly love.

President Harry Truman correctly assessed the close association between human nature and vengeance. Standing up for oneself—or defending the honor of a child or spouse—is not just a morally righteous act, it is encoded in the DNA of human evolution, programmed into the human brain itself. President Truman may have started out as a haberdasher, but he had the instincts of an evolutionary psychologist when it came to his understanding of revenge and how it relates to humankind.

The assumptions we make about revenge—for instance, that it is innate to our species—is no longer mere uneducated guesswork. Revenge has transcended common sense and has made its way into modern science. Scientists have taken an interest in vengeance and the complicated interplay between emotions and critical thought. From behavioral economics, evolutionary psychology, and neurobiology, recent empirical data—both in the social sciences and in medicine—show that various biological, social, and economic forces can influence the taking of revenge. Social scientists have also found that there are gender, age, income, and cultural differences that determine how people feel about revenge.4 Perhaps it was a mistake for humankind to have so reflexively surrendered to societal pressure, ignoring feelings of vengeance so indispensable to our mental makeup and so biologically linked to our moral development.

As a species we are profoundly sensitive to injustice and we react viscerally, and cerebrally, to both unfairness and the delivery of just deserts. Fairness and reciprocity are fundamental human concerns. Everyone responds to injustice on some level, and a legal system is not necessary to having such feelings. The human obsession with just deserts long predates courts of law. Children who shout “Hey, that’s not fair!” are connecting cerebrally and emotionally with the natural history of the human species. Studies show that children, in particular, are willing to sacrifice their own treats in order to punish other children who have grabbed more than their fair share. “‘One for me, two for you’ may not be too bad,” said Ernst Fehr from the University of Zurich. “But ‘one for me, five for you’ would not be accepted.”⁵ Perhaps this study should have served as the scientific rallying cry for the Occupy Wall Street movement.

Nations and cultures also have different levels of tolerance for revenge.

A study published in the British journal Nature noted that men experience more personal satisfaction in seeing someone get punished than do women.6 Men and women were found to be equally outraged by unfair treatment, but men had less empathy for those who were about to be punished and, in fact, took more pleasure from watching the punishment take place.⁷ Women express more vengeful attitudes but might ultimately be more squeamish about actually seeing it done, much less doing it themselves.

Yet a recent study published in the National Bureau of Economic Research, involving eighty-nine thousand people in fifty-three countries, concluded that women are, in fact, more vengeful than men; older people are more vengeful than younger people; the poor are more vengeful than the rich; and if someone has been exposed to high crime or has been the victim of a crime, he or she will tend to be the most vengeful of all.⁸ Of course, this study only speaks to vengeful dispositions; it doesn’t address whether any of the respondents would have actually resorted to revenge if given the chance.

Of course, that’s always the problem with polls and surveys. People don’t reveal what’s actually going on inside their heads; they respond with what they think we want to hear or what’s culturally acceptable to say. But now science can actually read minds by taking simultaneous pictures of the brain at work. Peter Sokol-Hessner, from the Center for Brain Imaging at New York University, has explained how magnetic resonance imagining (MRI) machines can reveal the changes that occur in the brain when human beings are placed in certain situations or are forced to react to threats or insults. “As blood pumps through the brain, the oxygen it contains causes small changes in the magnetic field,” he says. “The scanner can pick up on that and tell us where the blood is flowing. We get a picture of which parts of the brain are being used.”⁹ Dominique de Quervain, a neuroscientist from the University of Zurich and the leader of the most important study on altruistic punishment to date, says that “increased blood flow in a certain brain region means oxygen consumption and more brain activity in that region.”¹⁰

All of these recent advances in brain-scan technology finally prove what we always knew to be true in our bones: revenge is very much built into our anatomy and hardwired in our brains.

The prefrontal cortex of the brain is where human beings engage in logical reasoning, cost-benefit analyses, and the performance of critical mental tasks. The parietal cortex and the temporal lobes are involved in decision making, as well. Not surprisingly, these areas of the human brain are much larger than the same areas found in animals. Scientists believe that these sections were the last to develop in human evolution.11

In July 2008, the New York Times, inspired by the capture of Radovan Karadzic, the former leader of the Bosnian Serbs who was charged with the genocide of nearly eight thousand Muslims, reported on several recent studies showing that there is, among other things, an economic calculation to vengeance.¹² Avengers actually do engage in a cost-benefit analysis before vindicating their loss. Vengeance is not a brainless activity, and revenge is neither as irrational nor as impulsive as we have been led to believe. Avengers are not all Mad Maxes, loose cannons always in a state of half-cocked readiness. On the contrary, avengers are deliberate thinkers and methodical risk takers. And economic theory can be used to quantify revenge and account for those risks.

Below the top of the brain is where the limbic, the orbitofrontal cortex, the right insula cortex, the dorsal striatum, and the caudate nucleus sections are all found. These areas of the brain are believed to have developed first and, along with the amygdala, are involved in the processing of human emotions. Humankind evolved first as emotional beings long before advanced thinking distinguished us from all other life on Earth. During the natural history of our species, our emotional development preceded our facility to reason. An amusing paradox is that rationality was an afterthought in the evolution of the human brain. We pride ourselves on our ability to engage in critical thinking, but our emotions might actually supply the more elegant, if not essential, feature of brain circuitry. The dorsal striatum and the caudate nucleus are especially involved in the processing of rewards (and experiencing delicious tastes) that result from having made a decision or taken some action.¹³ This is the region of the brain where feelings that arise from decision making are centered. And it is here where a biological basis for revenge is found, and where the anticipation and taking of revenge generates positive emotions.14

One of the reasons why psychologists and economists have joined forces is because the part of the brain that is responsible for rational decision making oftentimes produces irrational results. This phenomenon, so common in everyday life, contradicts the premises of the rational actor model, in which human behavior is always presumed to be rational and predictable. This model, however, seems to work better on paper than it does in practice. The brain is surely capable of consistent rational decision making. But emotional influences keep getting in the way. And the rational actor model has never properly accounted for the psychology of the revenge impulse, where unfairness and injustice bring about a response that is motivated by vengeance and not purely rational thought.¹⁵ Moral outrage cancels out rational choice and still ends up with a decision that makes perfect sense—morally and emotionally. But what’s the point of having a highly developed prefrontal cortex if so many people end up making boneheaded decisions? Human beings are, if nothing else, creatures of error. The prefrontal cortex is often grossly underused. Critical thought is suspended and defers to emotional thinking.

People buy feverishly into stock and real estate bubbles. They trust Ponzi schemers even when the methods of these charlatans simply don’t add up. They fall victim to addictions, like drugs, alcohol, and gambling, even though the rational mind is fully aware of how ruinous these deviances can be. And when it comes to love, the prefrontal cortex automatically shuts off and the limbic, insula cortex, and striatum sections of the brain, apparently, go into serious party mode. Human beings are fated to fall in love with the wrong people. But if lovers start out as rational actors, why can’t they process the clues of a love about to go bad and simply move on to a more suitable mate?

Nonetheless, sociologists, economists, and political scientists are largely guided by, and direct their scholarship toward, the clear-eyed certainties of the rational actor model. Despite so much evidence to the contrary, there remains a presumptive faith that individuals will gravitate toward rational decision making. Revenge, however, is generally understood to be governed by emotional influences and moral rewards. Revenge taps into the spiritual and moral universe; its value is not usually measured in tangible outcomes. This perhaps explains why in a culture where values are measured exclusively in material terms—money and status—the benefits of vengeance can be easily and mistakenly undervalued. The true riches of revenge are experienced internally. They are mainly appreciated as pleasures, in the unreachable, intangible caverns of the soul where honor and duty reside. It’s not that the rational actor model fails to properly account for revenge, it’s that a very different form of rationality must be accepted in order for the avenger to be properly understood as engaging in rational behavior. In fact, it’s perhaps safe to say that the emotions of revenge end up supplanting the steely premises of rationality.

The growing field of behavioral economics, neuroeconomics, and the cognitive neuroscience of social behavior examines the relationship between decision making and irrational conduct. Jonathan Cohen, a neuroscientist and director of Princeton’s Center for the Study of the Brain, Mind, and Behavior says, “The key idea in neuroeconomics is that there are multiple systems within the brain. Most of the time these systems cooperate in decision-making, but under some circumstances they compete with one another.”16 It is precisely this competition that explains why revenge is so sweet, and why perhaps, in the mind of the avenger, it might actually be more rational to opt for revenge rather than listen to all the cautionary warnings that play repeatedly inside one’s head.

Brain scans, whether from an MRI or from positron emission tomography (PET) machines, which measure blood flow to the brain, show that when people are insulted there is heightened activity in the prefrontal cortex, which is the area of the brain that experiences hunger and cravings.¹⁷ There is also activity in the bilateral anterior insula, which flares up when one is exposed to anger and distress.¹⁸ Justice is neither felt nor experienced by pure reason alone. A strong inner sensation arises that something is either righteously correct or grossly amiss. The heart of the brain, so to speak, where emotions are generated and localized, registers its own reaction.

A craving for chocolate or a feeling of resentment and a desire to strike back in response to the actions of another each causes an immediate increase in blood flow activity to the brain. A revenge fantasy and the need for a chocolate fix can result in the same craving: a desire to be satisfied, whether with temping food or injustice rectified. A dessert of chocolate and just deserts that is witnessed being delivered to a wrongdoer produce similar neural sensations and light up the same regions of the brain.

Given these scientific findings, it’s easy to see why revenge has always been referred to as both a pleasure and an addiction. Revenge actually does taste good—even by those who are merely watching from the sidelines. Dramatists always appreciated the sensory power of revenge—and long before anyone ever imagined what a brain driven mad by resentment actually looks like. Even the eighteenth-century Scottish philosopher David Hume would have been unsurprised by these scientific findings. Nearly three hundred years before anyone could have comprehended what an MRI machine looked like, Hume wrote, in his Treatise on Human Nature, that the “science of man” didn’t necessarily comport with rationality. If anything, reason always takes a back seat to desire, and passion is the most reliable guide to human behavior. To the extent that revenge is animated by desire, Hume would find little difficulty supporting the idea that reason has far less to do with it than does emotion.

The human brain reacts positively when it experiences the satisfaction of getting even. And given that a mind high on revenge looks similar to one undergoing a sugar rush, it is fair to say that the brain has a sweet tooth for vengeance. The increase in blood flow to the dorsal striatum and the caudate nucleus, where the enjoyment of rewards are experienced and where feelings of satisfaction are centralized, suggest that the mind plays no favorites between vengeance and chocolate. Both receive equal billing in the brain. Outside of our heads, however, chocolate is the main course on Valentine’s Day. Revenge receives no such indulgence in public enjoyment, and the only date it can get you is one straight to prison. One is accepted in moderation; the other is never tolerated. Of course, these equal levels of neural stimulation are achieved simply by the anticipation of satisfaction; one doesn’t actually have to consume chocolate or take revenge in order to experience these sensations.

Chocolate isn’t the only thing that can disable our critical thinking and activate the emotional spheres of the brain in which the processing of rewards are experienced. Emotions trump pure reason when the brain is exposed to cheaters or sly defectors who craftily manipulate games dealing with money. Scientists who work in the fields of behavioral economics and neuroeconomics have devised a number of experiments that test what happens to the human brain when it is exposed to injustice and unfairness.

Investment games conducted by Jeffrey H. Carpenter and Peter Hans Matthews, both economists at Middlebury College, demonstrate that 10–40 percent of the people they tested would punish someone by docking them money if they were discovered to have played the game unfairly or ungenerously. “The urge to punish seems very strong,” Carpenter asserts. “Some people will spend money to punish even if it has no effect on them.”19 Even mere spectators to the game are prone to retaliate. Such is the purview of the altruistic punisher, who is prepared to deliver the punishment or, in the case of the Hollywood hero, take on the role of the crusading avenger at great risk to himself and largely for the benefit of others.

The brain is stimulated not only by resentment but also by the positive emotions that are generated when someone is punished for bad behavior. This offers further credence to the theory that revenge has played, and continues to play, a strong biological role in the human experience. For instance, one Swiss study, conducted in 2004, demonstrated a neural basis for altruistic punishment, and did so by having the participants play the Trust Game.²⁰

Volunteers designated as players 1 and 2 were each given $10 and told that they could either keep it or transfer it to another person (player 2). If player 1 chose to turn it over to player 2, the total amount, then in the possession of player 2, was automatically quadrupled to $40, giving him $50 in total. Player 2 was then given the choice to reciprocate and either return half of the $50 to player 1, who, after all was the original source of his newfound wealth, or he could keep the $50 entirely for himself. If player 2 decides to keep all of the money, player 1 has the option to inflict a punishment, for example, taking back $25. It is at the point of anticipating the payback—the inflicting of punishment on player 2 because he behaved so ungraciously—that neuroscientists have observed the most elevated levels of brain activity in the very sectors of the brain that register emotional satisfaction. The study demonstrates that the mere anticipation of revenge can be the source of positive feelings.

The chance to punish player 2, the defector who was more than happy to walk away and hoard his bounty rather than share it, increased the consumption of player 1’s oxygen to the striatum, lighting up the same brain circuitry as a visit to a chocolate shop or taking in a revenge movie on a Saturday afternoon. And the same results ensued even when player 1 was advised that there might be a personal cost to seeking revenge. The only difference in that case was that the medial prefrontal cortex, the area of the brain involved in the balancing of costs and benefits, was also activated.

A more recent study, conducted in Germany in 2010, relied on the Dictator Game, in which player 1, the dictator, decides how to split a pie with player 2, who has no means to reject player 1’s division, but player 2 is given a chance to punish player 1 at the cost of reducing his own share.21 The study tested the brain activation of player 2, who is given the opportunity to exercise revenge against player 1, along with the brain activity of a third party, player 3, who merely witnessed and did not derive any material benefit from the exchange. The study concluded that player 2 experienced heightened brain activity associated with altruistic punishment in the dorsolateral prefrontal cortex, the anterior cingulate cortex, and the anterior insula when he chose to involve himself directly in the punishment—meaning, player 2 engages in his own self-help and does not delegate his duty to avenge. As for player 3, she experienced the same brain activation, especially in the limbic regions, such as the insula and the striatum, but only if the punishment had a strong negative effect on player 1—meaning, punishment with real results.

The findings of the German study largely support the conclusions of the Swiss study by establishing, once again, that the reward regions of the brain are activated during altruistic punishment—we like seeing wrongdoers receive their due, even if we have not been personally wronged. And we might even participate in the punishment if called on to do so. The German study included a third player, someone who was merely watching the reciprocity, or lack thereof, between players 1 and 2. She, too, was affected by the witnessing of injustice and received her own neural satisfaction from watching player 1, the dictator, receive his just deserts—even though player 3 had no independent reason to desire revenge, nor would she have been expected to derive a subjective benefit from doing so, and stood to receive no material benefit from the revenge taken by another. As the study surmises, “Observing someone else being treated unfairly could initiate a simulation process which requires the same network as the processing of an unfair offer itself.”22 This study undoubtedly validates a neural basis for why the spectator in the bleachers, or the member of a movie audience, enjoys watching payback when it is deserved and when it results in a true detriment to the wrongdoer.

The witnessing of justice, especially injustice, is not a matter of indifference to most people. It perhaps explains why contemporary culture is so riveted by TV courtrooms, from The People’s Court to Judge Alex. The soap operas that once dominated daytime television have suddenly been replaced by a curious incarnation of reality daytime TV—with storylines entirely focused on parties to a legal dispute. Real cases with actual litigants and real judgments with binding remedies are what now seem to entertain the daytime TV viewer. However, the popular appeal of courtroom-focused TV is not driven entirely by entertainment, or even a desire to learn a moral lesson or see right prevail over wrong. Perhaps, more important, the human brain is simply constructed to enjoy someone receiving a public comeuppance, witnessed by all, each of us sharing in the satisfaction, responding to the inner core of our evolutionary history and neural development.

Another neuroscientific test, the Ultimatum Game—this one dealing with duplicity in matters of dollars and cents—was conducted several years ago by researchers at Princeton University.²³ Two players are handed a total of $10 between them. Player 1 is asked to share the amount with player 2. He can decide to give as much or as little as he wishes; he can divide it up any way he wants. If player 2 refuses the allocation that is offered him, then both players will receive nothing. Both players are aware of the rules beforehand.

The rational actor model would suggest that player 2 should accept any low offer, since rejecting the offer would leave him with nothing. Of course, it would also leave player 1 with nothing. Perhaps player 1 deserves nothing. What if player 1 merely wishes to hand over one dollar, and he gets to keep $9. Surely that’s not fair. It isn’t like the $10 actually belonged to player 1 or that he had done something special to deserve it. It was a mere fortuity that the money was initially handed to him rather than player 2. He should be punished for his lack of generosity by having player 2 reject the offer, but then player 2 would get nothing out of the deal. Rejecting an insulting offer isn’t rational, since one dollar is better than nothing. But then again, perhaps player 2 realizes that he didn’t do anything to earn the money, either, so it’s better to reject any paltry amount as an act of vindication against the bad behavior of player 1.

The emotion of moral injury is always a game changer when it comes to refuting the rational actor model. A human brain exposed to an insult takes on a very different mindset, one influenced by human nature rather than simple economics. It turns out that most people will reject any offer of $3 or less. And some will turn down any offer that is less than half of the amount player 1 was initially given. Why reject $4, which is essentially free money? John Hibbing, a professor who studies biological connections to social behavior, explained the raw emotions that underlie the Ultimatum Game. “Say it is $20. If I get three or four dollars, I’ll say—‘Screw you.’ I’d rather go away with nothing than see you get most of it.”24

But what’s rational about that? It’s certainly not the behavior of a rational actor; it’s more like a playground tantrum where the boy excluded from the game just happens to be the owner of the ball. Nursing all kinds of adolescent hurt, he simply decides to go home and take his ball with him. Now, no one gets to play. If he decides to stick around, he might get picked the next time. Everybody wins. Of course, that’s what a rational playground actor might do, a kid who doesn’t allow his emotions and pride to stand in the way of his long-term interests in schoolyard fun. Of course, any economist who insists that the boy should stay and share his ball obviously hasn’t spent much time in and around schoolyards.

In the Ultimatum Game, rejecting the offer spells the end of the game, but player 2 doesn’t merely walk away with nothing. Yes, no money changes hands, but player 2 at least receives the satisfaction of not allowing an ingrate to get away with an unjust windfall. The reward is intangible but not altogether immaterial.

And the human brain bears this out. Researchers hooked up volunteers to MRI machines and had them play the Ultimatum Game. When player 2 received a stingy offer from player 1, $3 or less, for example, both the dorsolateral prefrontal cortex (associated with critical reasoning and the balancing of costs and benefits) and the bilateral anterior insula (the limbic region of the brain, which processes anger and distress) were reported as most active. The more personally offended player 2 is from receiving such a disgracefully low offer, the more likely he or she will be to reject it. But the technicians watching from the control room only see brain circuitry lighting up like a starburst as blood flow increases and oxygen is consumed in the limbic region where all those vengeful emotions compete with the rational mind.

A similar study of the Ultimatum Game, this one conducted in the Karolinska Institute’s Osher Center in Stockholm, demonstrated that when one player insisted on keeping 80 percent of the money, the amygdala, where outrage is triggered in the brain, and the higher cortical domains, which is associated with introspection and conflict resolution in the upholding of rules, were aroused. Only by giving the participants antianxiety medication could their amygdala responses be suppressed. “This indicates that the act of treating people fairly and implementing justice in society has evolutionary roots. It increases our survival,” wrote Katarina Gospic in the journal PLoS Biology.25

A 2002 study conducted by psychologists at Princeton University examined a thousand people to see how they would punish an assortment of crimes and misdemeanors.²⁶ Most of the participants carefully tailored their punishment to match the severity of the wrongdoing. They seemed inordinately focused on getting their measurements right, making certain that their sentencing recommendations approximated an eye for an eye. These punishments were given solely to address each offense. The participants were told not to worry about deterring future behavior. The purpose of the exercise was merely to right a wrong, to do what is deserved, regardless of whether it might have an effect on the future. And with that goal in mind, each person went about the tedious business of approximating their punishments, measure for measure.

All of these tests point to the same conclusion: the human brain is wired for justice, and short circuits when exposed to injustice. It is stimulated both by the anticipation of vengeance and the completion of justice. And the brain experiences a particularly intense reaction to unfairness and a compulsive desire to respond to that unfairness—even if it means rooting for revenge from afar or sacrificing something to assure that vengeance ultimately is achieved. And last, the human brain has an inherent understanding that punishment cannot be arbitrary or excessive—that, not unlike the law of the talion, punishment must always be subject to proportional limits. Indeed, the enduring legacy of the talionic principle must have biological roots, too—the rule simply made infinite sense to ancient peoples. Once again, human emotions, so essential to understanding revenge, play an equal role in the human brain’s response to injustice. It becomes emotionally intolerable to watch and, even worse, to experience firsthand.

While the human brain is always on high alert to matters of justice and revenge, the decisions it makes in response to insult and injury are not determined by purely cognitive, logical reasoning. “These findings suggest that when participants reject an unfair offer, it is not the result of a deliberative thought process,” writes Cohen, the neuroscientist from Princeton. “Rather, it appears to be the product of a strong (and seemingly negative) emotional response.”27

Human beings gravitate toward fairness. When they are in the presence of unfairness, or when they are treated unfairly, their minds go mental, and the brain lights up in every section where emotions matter. This heightened neural sensitivity to injustice explains why, when given the chance, human beings will punish the wrongdoer even if it confers no direct personal benefit on them. This is the very essence of “altruistic punishment”—an individual chooses to take on a costly, selfless act for no reason other than that, morally, it must be done. He or she performs this task out of pure altruism and chivalry, even though there may be great risk involved. And, not unlike the human brain’s response to cravings, it’s the anticipation that always matters most. The idea that justice will be done is more important than how one feels after justice has finally arrived.

Brian Knutson, a psychologist at Stanford University, explained that the absence of self-interest doesn’t make altruistic punishment irrational. All it shows is that, “instead of cold calculated reason, it is passion that may plant the seeds of revenge.”²⁸ Ernst Fehr, the director of the Institute for Empirical Research in Economics at the University of Zurich, and a coauthor of the Swiss study, acknowledged that while passion surely plays a role in altruistic punishment, “I do not think that our evidence indicates that passion overrides rationality. In fact, I believe that our evidence shows that people deal quite rationally with their emotions.”29 In the same way that individuals feel personally rewarded by giving to charity, the inclination toward performing a just act is a similarly rational enterprise calculated to produce an intangibly spiritual reward.

When it comes to justice and revenge, one should never underestimate the significance of the emotional sphere of life. But one should also not mistake emotion for misjudgment, for assuming that those who respond emotionally are necessarily without reason. The fact that emotion often drives critical thought doesn’t reduce the moral clarity of the decision. Law professor Michael S. Moore has written that “there is . . . a rationality of the emotions that can make them trustworthy guides to moral insight.”³⁰

In fact, Cohen speculates that these deeply visceral reactions that are lodged in, and instantly uploaded from, the human brain may also have an evolutionary basis. In the days before law enforcement and state-sanctioned retribution, it was important for primitive man never to appear weak or unwilling to retaliate after an attack. “In such an environment,” Cohen said, “it makes sense to build a reputation for toughness.”³¹ One needed to demonstrate that he could not be so easily taken advantage of. Addressing how vital it was for early man to measure up to the societal expectations that force will be met with force, evolutionary psychologists Martin Daly and Margo Wilson observe: “Men are known by their fellows as ‘the sort who can be pushed around’ and ‘the sort who won’t take any shit.’ . . . In most social milieus, a man’s reputation depends in part upon the maintenance of a credible threat of violence.”³²

Offering a similar view that vengeance has an evolutionary basis springing from centuries of human conflict, the anthropologist Lyall Watson speculates that “perhaps our fondness for the idea of just retribution is a sound one, based on long evolutionary experience. It is possible that the satisfaction it brings us, the spiritual fulfillment it seems to bring, despite the pain, is an adaptive response. Revenge makes sense, it feels right, simply because at some level we recognize that it brings long-term stability to competitive rivalries.”³³

Once humankind survived the perils of tribal bullies and nomadic bad asses and realized that not everyone is well suited to a lifetime of vengeance, and after governments stepped in and became the caretakers of justice, why didn’t the rational actor simply behave more rationally and recognize the futility of trying to get even? Revenge should have become obsolete, a survival mechanism from an earlier age that now carried unacceptable risks and no longer made sense.

Brain-scan imaging offers an answer to this as well. The neural basis for revenge aligns critical reasoning with emotional satisfaction. Neither necessarily cancels out the other. Achieving moral balance requires a feeling of justice as much as the fulfillment of revenge. So where does that leave the rational actor model or rational choice theory, the brainchild of economists and political scientists, with its complete reliance on reason and rationality? Vengeance isn’t irrational for the individual. It is perfectly rational to insist on living in a just society and to assume the task of ensuring that justice will be served. It may, however, be irrational for society to allow individuals to take their own revenge, even if they have wholly rational reasons for doing so. For this reason, in justifying the legal restrictions it places on revenge, society regards revenge as irrational. And it finds itself forever having to make its case against private vengeance. Avengers who act alone and pursuant to their own agenda end up interfering with the state’s monopoly over revenge. They get in the way of law enforcement and prosecutorial justice. What is perfectly rational for the avenger can become intolerable for the state.

The rational actor model, however, presumes that human beings are self-guided by the brain and not the heart. And it also assumes that since revenge always carries some risk, a truly rational actor would never willingly place himself in harm’s way. Only an irrational person is driven entirely by emotion—the fool who acts first and thinks later. Truly rational actors would never resort to revenge—unless we’re not nearly as risk averse to vengeance as we had previously thought.

Brain scans show that the part of the brain that responds to justice is activated by emotional considerations—positive emotional feelings of satisfaction that are generated when a wrongdoer receives his or her due. And these same neural sensations operate without regard to personal risk or the expenditure of personal resources. Human beings apply the risk-reward, cost-benefit calculations to revenge as if there were a mental recipe for vengeance. They don’t overlook deliberative judgment. Mental reasoning is not rejected; it is simply added to the emotional mix. Revenge brings emotion and rationality into harmony. And brain scans have demonstrated just how much emotion and reason coexist in the ecosystem of revenge. Human beings are often willing to incur costs if it is in the service of paying back what is justly owed. The precise amount owed is stored in working memory, safely kept and calculated. The brain’s recognition of fairness is so acute that in return for more justice, human beings are seemingly prepared to accept more risk. And they do so not out of rash impulse but through measured, critical thought. The avenger knows exactly what he is getting himself into.

Two presumptions about the rational actor model are debunked by these studies; two types of irrationality are exposed. The avenger responds to an insult or injury with a complex interplay of emotional mechanisms and rational considerations. The result might be risky yet still rational. This is especially true in cases of altruistic punishment. A rational actor thrust into the role of selfless avenger is already acting irrationally. Why would anyone punish on behalf of a stranger unless he or she was under the spell of a super hero complex? “Leave the cape and cowl at home, Batman—that’s what the police are for.” Yet ordinary people are willing to bear the economic cost of making sure that defectors from these economic games, or deviants from society’s rules, receive their just deserts, even if there is no material benefit to them. Such impulses are plainly not rational, and yet the human brain takes each insult personally, and then rationalizes why something must be done.

Scientific research conducted in 2009 has identified a “warrior gene,” monoamine oxidase A (MAOA), suggesting some interplay between behavioral genetics and behavioral economics.34 There just might be a genetic contribution to altruistic punishment, an evolutionary basis to incur a financial cost simply to punish a wrongdoer without receiving any immediate material reward. The warrior gene responds to resentment and spite, which is similar to the punisher who is motivated by pure altruism.³⁵ All of this suggests a strong biological and evolutionary basis for revenge and, perhaps, even a Darwinian explanation for the improbable survival of the revenge instinct. The genetic makeup of our species has long factored in the value of vengeance as a survival tool. We have stubbornly held on to it for millennia and have applied it in our lives with the versatility of manna.

We can fake an orgasm, feign sincerity, exaggerate love, contrive all manner of moral outrage, and profess varying degrees of hatred, but the most genuine of all human impulses, the one that is not easily faked or forfeited, is revenge. Love we can live without, or it can be unrequited or experienced from afar. Anger can be managed. Jealousy can be transferred. Fear can be overcome. Hate has a way of fading, and grief dissipates with time. Revenge, however, is not so easily forgotten. It can be delayed, but it can’t be ignored. It has a long memory. And the withholding of revenge brings about no inner peace. No other emotion carries the same weight or burden. Unrealized revenge is the great disturber of our sleep and the duty that sometimes summons us from our sleep.

So how to respond to those who maintain that revenge is without reason, that the avenger is the most irrational of men? Legal theorists and philosophers have clearly not been keeping up with the scientific community if they insist that revenge is always irrational and that no reasonable man would ever resort to it. For eight centuries, nation-states have taken it on themselves to track down wrongdoers and administer punishments on behalf of all of society. The revenge impulse, however, is still widely felt and appreciated, if not practiced, on individual levels. And not all people are irrational in their high regard for revenge.

Maybe Harry Truman was right all along: those who make public policy simply don’t know enough about human nature. They miss all the signs and mental cues that are vividly captured on a brain scan.

And yet, rational choice proponents see nothing but illogic in revenge. The philosopher Jon Elster wrote that revenge offers only costs and risks and no benefits. “Rational individuals follow the principles of letting bygones be bygones, cutting their losses and ignoring sunk costs. . . . People act in impulsive, unreflective ways, under the sway of emotions too strong to be resisted. . . . Revenge behavior is impulsive.”36

Judge Richard Posner, one of the leading figures in the field of law and economics, has written that a rational man is fully aware that vengeance “is an extremely clumsy method of maintaining order.”³⁷ Fixated on cost-benefit analysis, the rational actor will come to realize that revenge never truly recoups his losses. Moreover, logically he knows that retaliations raise the stakes on further reprisals.

At the heart of the rational actor model is the clear-eyed, business sense that it is far more costly for society to allow private acts of vengeance than to construct a system of justice charged with maintaining order by way of fines, incarceration, and capital punishment. This argument sounds logical. And it supports many of the premises behind the state’s monopoly over revenge. But it misses, if not altogether ignores, the emotional component for why revenge makes perfect rational sense to aggrieved individuals. It isn’t always true that the rational actor, focused entirely on cost-benefit calculations, can shut himself off from the way human beings actually experience indignity. Hurt feelings are not so easily neutralized; human beings do not inhabit such sterile zones where risk aversion and logic guides all decisions.

When filtered through the far fuzzier math of the avenger, and the rightness of his cause, a much different set of priorities arises and presumed irrational decisions have a way of making rational sense after all.

Charles Ng, a serial killer, was convicted of murdering eleven people in California in the mid-1980s. He was suspected of killing possibly another fourteen. He was put on trial for killing twelve. There was no finding of guilt, however, with respect to the twelfth victim, Paul Cosner. The jury was deadlocked on that count and so the judge ordered a mistrial. The prosecutors ultimately decided not to retry the case on the twelfth count. After all, the trial had already cost the citizens of California $12 million. Another criminal proceeding would only add to the expense and accomplish little else. Ng was already headed for the electric chair (he still remains on death row in San Quentin State Prison). The murder of eleven people had already gotten him the highest punishment he could receive. What would one more conviction do to change the final disposition of the case?

Paul Cosner’s sister Sharon, however, wasn’t satisfied with this legal outcome. Yes, Charles Ng would one day be executed for killing eleven victims, but her brother was not included among them. His death was somehow forgotten. There was no record of why and how he died. Without a cause of death, it was as if her brother’s life had never existed at all. Ng’s execution, should it ever occur, would not vindicate the loss of her brother unless there was a way to connect Paul’s death to Ng’s act. Sharon Cosner was determined to obtain some official public record signifying that her brother had been killed and that Ng was responsible for his death.

She urged the prosecutors to retry the case, but given the cost and the futility of yet another guilty verdict, they decided against it. It wasn’t rational. She then tried a different approach by making a direct appeal to the judge who presided over the case. From him she eventually obtained a one-page, handwritten court order that she used to obtain Paul’s death certificate, which now finally listed the true cause of his death. In it the judge wrote: “Paul Steven Cosner went missing in San Francisco on November 2, 1984. He has not been heard of since and it appears the Court finds that he was the victim of murder at the hands of Leonard Lake (a co-conspirator) and Charles Ng.”

Sharon Cosner said, “I think it’s finally over now. . . . I think this will finally allow us to move on with our lives. . . . Up until Judge Dearman signed this order, there had been no justice, no one held responsible. Now someone has been. . . . [The court order] makes all the difference to me—it really does.”38

Ng was not found guilty, in a legal sense, of killing Paul Cosner. The judge’s order had no legal significance although its emotional, symbolic significance was immense. An official court document, as public record, finally did exist, and proclaimed that Paul Cosner’s murder would not be forgotten. Charles Ng would one day pay the ultimate price, and that payment, symbolically, would now be in the service of honoring Paul Cosner’s memory as well.

A rational actor in Sharon Cosner’s position would have said: “Charles Ng is toast. I know he killed my brother. It’s not worth my time and expenditure of emotion, not to mention the state’s money, proving something we all know to be true. Ng will ultimately receive a lethal injection, and that’s what he deserves.” Was it rational for Sharon Cosner to pursue so obsessively some acknowledgment of her brother’s death? What was wasteful and irrational for the government was indisputably filled with meaning for the murder victim’s anguished sister.

In 2002, Lee Boyd Malvo and John Allen Muhammad, known as the DC Snipers, terrorized the citizens of six states and Washington, DC by shooting and murdering ten people as part of an Islamic jihad. Because some of the murders were committed in the nation’s capital, then attorney general John Ashcroft had the authority to select which jurisdiction would be given the right to conduct this highly visible and emotionally charged capital murder case. Each of the states wished to hold the trial within its own jurisdiction. In fact, they fought over who would get the first crack at prosecuting the DC Snipers with the same ferocity of cities clamoring to host the Super Bowl. The only difference: Super Bowls are moneymakers; high-profile capital murder trials end up rivaling the defense budget of a small country. Economically speaking, murder trials are money losers.

Ashcroft chose Virginia, and the state tried the case in 2003. Muhammad received a death sentence, which was carried out in 2009. Malvo was given a life sentence without parole.

The DC Snipers capital murder trial cost the citizens of Virginia millions of dollars. But the meter continued to run. Immediately after Muhammad and Malvo were sentenced, the five other states insisted that they be given a chance to pursue their own capital murder cases. They wanted these prosecutions held in their own courtrooms, brought on behalf of their own murder victims, and with their own citizens serving as jurors.

Clearly there was no rational reason for doing so. Not only would duplicative trials be wasteful, costly, and redundant, but they also might expose errors or improprieties in the Virginia trial, which could have opened a door for the defense team to undo the earlier verdict. Aside from spending millions of taxpayers’ dollars simply to accomplish the same thing as what had already been achieved in Virginia, there was a real risk of prejudicing the outcome. Besides, Muhammad could only be executed once, and Malvo had but one life with which to serve his life sentence. Why not simply take a free ride courtesy of the tax-paying citizens and victorious state prosecutors of Virginia?

The prosecutors of the other states hadn’t yet had their shot at the DC Snipers. They wanted their turn. They weren’t concerned about wasting taxpayer dollars. In fact, they knew that the citizens of their states weren’t worried about the costs either. Holding separate trials in each state had enormous moral and symbolic value that couldn’t be measured in money. What these citizens wanted most was a public reckoning where the crimes committed against their own state residents would be acknowledged. And they were more than willing to pay for it. Muhammad and Malvo had to be punished for violating the laws of each of these states. Yes, a spectacular waste of money, and surely a waste of time. But there was a duty to the dead—a far greater priority than fiscal discipline—that must be publically honored.

One Maryland prosecutor said, “We had six homicide victims here in Montgomery County; none of them has had their day in court. Neither has the community at large had their day in court.” A Louisiana prosecutor echoed a similar sentiment, “They murdered a nice Baton Rouge woman. . . . They have a date with Louisiana justice. I’ll do everything I can to make sure that they will make that date.”39

The evolutionary development of humankind depended on sending a clear message to wrongdoers that no attack or insult will go unanswered. The reciprocity of payback had to be certain and expected. Aside from enforcing a practice of deserved retaliation, it also established an organizing principle of reciprocity—all scores will be settled, and all acts of kindness, friendship, and cooperation will be met, in kind, with similar positive gestures. The former deters misdeeds; the latter produces trust.

The game theory tit for tat demonstrates how this works.⁴⁰ A rational man would naturally always gravitate toward reciprocity and mutual advantage, which tit for tat virtually assures so long as both parties are rational and neither chooses to defect from the game. If the first move is positive, the second player will reciprocate—tit for tat. Each reciprocal act of cooperation will invite yet another act of mutual advantage. Once one of the actors does something that requires not an act of cooperation (a defection) but rather an act of retaliation, the second player will respond in kind. At this point, however, it is still possible for the parties to resume cooperation rather than repeated retaliations. The party who defected first must be forgiven. And in order for that to occur, he must respond with a cooperative act. If he does, then order is restored.

Tit for tat mirrors the logic of the Golden Rule: truly do onto others as they actually do unto you—if they are kind, repay with kindness; if they cause harm, then one must reciprocate with harm. Both sides are on notice that the game is always in play. And they know that falling out of line will not be forgotten: “kindness for kindness; evil for evil.” Not unlike with revenge, tit for tat is a game of measurement and precision. All rational actors know that it is always best to respond cooperatively, to trade in positive gestures rather than to invite retaliation that benefits no one. And best of all, for those who fear vengeance because retaliation can be excessive and disproportionate, tit for tat ensures that retaliation will never exceed the action that invited the response.

The game breaks down, however, when the first act of retaliation is not forgiven, and the wrongdoer responds with a reciprocal act of revenge. This is where vengeance becomes recycled, where retaliation rather than mutual cooperation begins to define the relationship between the players who, suddenly, are locked in battle that knows no end. The Cold War, with its strategic alliances and diplomatic maneuvers, very much resembled a game of tit for tat—one with, however, annihilating implications. Ongoing hostilities are clearly not mutually beneficial, and the recycling of vengeance is ultimately self-destructive and irrational. The rationality of tit for tat has its own internal logic—you get what you give. The endgame is reciprocity itself—the players are empowered to decide whether the game will be mutually rewarding or infinitely annihilating. Those who cooperate are rewarded; defectors are punished. Without reciprocity there will be open season on whoever develops a reputation for always backing down.

There are still even more refutations of rational choice theory when it comes to revenge. The Prisoner’s Dilemma demonstrates how the rational actor might be forced to make a decision that, in the end, doesn’t appear to be rational or in anyone’s self-interest.41 Two prisoners are separately interrogated for a crime they jointly committed. If both keep silent and do not implicate the other, the authorities will not have sufficient evidence against either one and they will possibly both be set free. If each blames the other—essentially defecting from the game of mutual trust—then the consequences of the Prisoner’s Dilemma are revealed: both will be punished severely, although their cooperation with the authorities will be taken into account. If, however, only one accepts the deal and implicates the other, then the snitch will receive immunity and be set free, while the prisoner who maintained his silence and refused to betray his coconspirator will take the fall and receive the harshest sentence. Since that is the worst outcome of all, the rational prisoner will avoid the trap of the prisoner’s dilemma by simply hedging his bets and ratting out the other. That way, at least, he won’t be left alone to suffer the consequences of his crime while his duplicitous colleague is set free.

The dilemma that the prisoners must confront is that locked away in separate holding rooms and, in some cases, having no prior social bonds between them, they would have no reason to trust one another. If they had complete trust, then they would both be set free. The absence of trust, however, assures that both will be punished. No one wants to be the only one to take the blame and pay the full price while the other receives the windfall of walking away. Each prisoner rolls the dice that his partner in crime might not defect, in which case the one who does will ultimately go free. For this reason, the most rational choice is also the least optimal one since it requires mistrust and defection. In a world of reciprocal altruism, all prisoners would know to trust one another and always cooperate. No good comes from defection. But rational actors have little faith in altruism and surely know not to count on it. Mutual advantage and trust will set the prisoners free, but they are stuck with the dilemma that rational men and women instinctively know: defectors are more plentiful, and predictable, than cooperators.

Robert C. Solomon has written that games and tactics such as tit for tat and the Prisoner’s Dilemma depend on retaliation—both the threat and its occasional delivery—to make cooperation possible. The cheater or defector needs to be reminded that there is a cost to taking liberties with mutual trust. The amount of the cooperation depends on the certainty of retaliation. The lessons of game theory are the same lessons of survival that social animals had to once learn. Humankind would have become an evolutionary failure had it chosen a life of perpetual forgiveness and the tolerance of endless defection. Solomon writes, “Vengeance is not the antagonist to rationality but its natural manifestation.”42

Once again, however, what is rational for the individual might not be tolerable for society. States can’t afford the social costs of never-ending games of tit for tat that are played like duels rather than love fests, where neither party is willing to break the cycle and cooperate. Over time, the game is played to destruction or to one party’s disappearance. The ultimate demise of the Soviet Union, which had no tat in response to America’s Star Wars program, is one example of this brinksmanship.

But here’s another dilemma: if revenge is biologically imprinted in the brain and if the evolutionary history of humankind came to expect both the threat and anticipation of vengeance, and if revenge is ultimately both rational and potentially destructive, then what are we to do with this instinct that can’t be stopped, feels so good, and yet demands that we somehow control it?

The answer is neither simple nor hopeful. After all, governments and legal systems do a poor job of acting as surrogates for revenge. Private acts of vengeance carry too many risks. Neuroscience informs us that the human brain cannot tolerate injustice and lights up like a slot machine when it anticipates the delivery of justice. Still, revenge is not a complete panacea, largely because legal retribution is often uneven, private vengeance is hard to measure, and what passes for the rational choice might not lead to the optimal outcome.

And there are those who say that for all its purported sweetness, in the end, revenge is ultimately unsatisfying. Vengeance doesn’t actually fulfill its promise of true satisfaction; getting even doesn’t make the avenger feel any better.

A study conducted in 2008 and appearing in the Journal of Personal and Social Psychology, titled “The Paradoxical Consequences of Revenge,” sought to refute the presumption that revenge leads to catharsis and relief, that it produces the necessary closure that is impossible to achieve any other way. Far from delivering closure, the report claims, vengeance actually increases the amount of unsettled aggression that existed before. Those who say “Get it out of your system and go punch a speed bag” would be surprised to learn that punching a bag actually increases one’s aggression.43 The anger doesn’t actually get out of your system; it stays put right where it was before, but now fully reenergized. The report concludes that people grossly over estimate how much the intensity of their anger and its duration would subside if vengeance was made available to them.

In the 2004 Swiss study led by de Quervain and her colleagues, increased blood flow to the dorsal striatum of the brain, the region closely related to pleasure and satisfaction, was activated one minute prior to when the wrongdoer (free rider) was due to be punished—meaning that it measured only the anticipation of punishment and not its aftermath, when vengeance had been taken and the avenger might feel altogether differently. The focus of the study was on the expectation of altruistic punishment—the pleasure that came with its anticipation—and not the actual state of mind of the avenger once the punishment was delivered.

The 2008 study was designed to show the actual experience of witnessing the punishment itself (the brain scans were performed anywhere from one to ten minutes later), which did not match the joy that came from the anticipation of revenge. The avengers were found to be less happy after all. The study found that “people believed that exacting revenge would bring closure, in the sense that they would think less of the free rider, when in fact it had the opposite effect—punishing the free rider made people think about her more, which in turn made them feel worse.”44

Revenge might feel good as a fantasy, but not in reality. Does this undermine the entire revenge enterprise? Why undertake the time and risk of tracking down and punishing a wrongdoer if the ordeal ends up like that lament in the Rolling Stones’ song, where the avenger simply “can’t get no satisfaction”? Neuroscientists can prove that the anticipation of revenge activates the blood flow to the brain. But once revenge is finally taken, the blood flow diminishes like a burst balloon. The circuitry lights up for the craving but not the completion.

Revenge is sweet, but sometimes its aftertaste is bittersweet. There is often ambivalence in the aftermath of vengeance. There can be both elation and, then, letdown. And the avenger can become guilt-ridden or remain bereft and without closure. But this neither should come as much of a surprise nor does it rob vengeance of its entwined connection to justice.

In Steven Spielberg’s film Munich, the Israeli assassins assigned to kill the Palestinians who were responsible for the murder of the Israeli Olympic team in 1972 spend their nights arguing over the moral implications of their task. With each assassination there is seemingly less of a feeling of relief. Doubt enters their conversations. They lavish attention and appetite over their dinners but feel no satisfaction from the vengeance they are feasting on with noteworthy success. Yet they know their duty and what the wrongdoers deserve, and so they forge on avenging the murders committed by Black September—but, again without ever feeling satisfied.45

In the films Braveheart (1995) and Gladiator (2000), the avengers are never given the chance to experience the satisfaction that should otherwise result from their vengeance. In both films the avenger is dead before the score is ultimately settled, or he dies in the process of redeeming the debt. In the classic Hollywood Westerns The Searchers (1956) and Unforgiven (1992), the avengers complete their task, but there is no happy ending, no realized satisfaction, nothing approximating joyful fulfillment. They simply walk away or return home no happier or accomplished than before.

When it comes to vengeance and justice, it shouldn’t really matter how the avenger feels afterward. All that is important is that the emotion is acted on and that the injustice is not ignored—that no moral revulsion comes from the unsettled debt. A happiness quotient is not the standard; satisfaction is achieved by following through with the duty to avenge without regard to whether it puts a smile on the avenger’s face. Happiness and satisfaction are two very different endgames. Some avengers will feel satisfied; others will feel ambivalent or won’t know exactly how to feel. Revenge is not immune to self-doubt. It is the revenge itself that is obligatory and absolute; the avenger doesn’t have to feel elation or relief—he or she merely has to get the job done. What matters is that honor is reclaimed and all debts are redeemed. Everything else is beyond the scope of vengeance or comes merely as an added bonus.

While the avenger doesn’t need to be made joyful, it is especially important that the wrongdoer be made apprised of why, specifically, he is being made to suffer. Political philosopher Robert Nozick observed that there is a necessary personal tie between the avenger and wrongdoer.⁴⁶ They are forever bound by the wrongdoer’s deed and the avenger’s loss. And this relationship must officially announce itself. After years of toil and then strategic planning, the Count of Monte Cristo let it be known to those who did him wrong that he was actually the betrayed Edmond Dantes, who has finally returned to claim his revenge. Law professor William Ian Miller wondered “what satisfaction could there be in not letting your target know what hit him and for what reason?”⁴⁷

In the 2009 study conducted in Germany, researchers found that participants were satisfied by taking revenge for wrongs done to them, and even more satisfied if the wrongdoer was duly informed why revenge was being taken. The study concludes: “Our findings corroborate the notion that revenge aims at delivering a message between the victim/avenger and the offender, and that revenge is only effective if this message is understood. . . . The message of revenge . . . [is]: ‘Never do this to me again.’”48

In the film, The Princess Bride, Inigo Montoya spends his entire life perfecting his swordsmanship and seeking vengeance against the six-fingered man who murdered his father and scarred both his life and his face. He prepares a speech in anticipation of when he will finally confront his father’s killer: “Hello, my name is Inigo Montoya, you killed my father, prepare to die.”⁴⁹

The film astutely recognizes that while Montoya might have devoted his entire life to honoring his father by avenging his murder, the final vindication does not have to include his own personal happiness. What’s more important is that, in receiving his just deserts, the six-fingered man must also be made aware of the reason why his life must now come to an end. Similarly, in Law Abiding Citizen, the avenger says to the assailant before killing him, “I know what it feels like to be helpless, just like when I watched you slaughter my whole family.”⁵⁰ In the Showtime dramatic series Dexter, a rogue vigilante prowls sunny South Florida in search of murderers that the Miami legal system has failed to punish. Before ending their lives and avenging the memory of their victims, Dexter surrounds them with the photos of all those they had killed as a symbolic reminder of the scores that are now, finally, being settled.

The satisfaction is in the doing and the enunciation of purpose. The feelings that surface in the aftermath of revenge are not the true measures of vindication. Human beings may experience ambivalence, but that doesn’t lessen the moral imperative, which begins with the moral injury and continues until justice is achieved.

On killing the six-fingered man, Montoya acknowledges, “You know, it’s very strange. I have been in the revenge business so long, now that it’s over, I don’t know what to do with the rest of my life.”⁵¹

Revenge isn’t supposed to lead to happiness. Revenge won’t necessarily bring about catharsis or closure, either. Revenge is not a cure to a sickness or the surrendering to a bad habit. It is a duty to the dead, an obligation to stand up for oneself or for another. Whatever damage was done to the victim won’t be repaired if and when the wrongdoer is punished. But that doesn’t alter the obligation. W. H. Auden said this about the “Romantic Avenger Hero”: “My injury is not an injury to me; it is me. If I cancel it out by succeeding in my vengeance, I shall not know who I am and will have to die. I cannot live without it.”52

In 2002, during the scandals of the defrocked, pedophile priests throughout Boston, John Geoghan was serving a ten-year sentence for one of 150 accusations of child molestation committed during his time in the priesthood. He sat in jail while many more trials awaited him. But the waiting—of the condemned priest and his tormented victims—came to an end when a fellow prison inmate, Joseph L. Druce, who had been victimized as a child, decided to take vengeance on behalf of the many children who Geoghan had abused. Druce strangled Geoghan in his prison cell, thus ending what would have been years of criminal trials at enormous taxpayer expense, along with endless trauma to those who would have been called to testify.⁵³

A most economical final resolution, rationally speaking. The problem was that none of Geoghan’s victims felt relief or gratitude for what Druce had done. On the contrary, they were resentful. No one had deputized Druce to give Geoghan his just deserts. The majority of the former priest’s victims believed that in being strangled in his cell by a stranger, Geoghan actually got off easy. Worse still, they felt that they had been deprived of their day in court. What they wanted was to be able to speak to their own sense of private violation by confronting this purported man of God who had once molested them. And they wanted the right, which they had earned from their victimization, to ask the court directly to punish Geoghan for what he had done. None of the victims had delegated anyone else to speak or act on their behalf. After each of their trials had been concluded, many would have been pleased to learn that the priest who still gave them nightmares had been strangled to death. Geoghan surely had to be punished. But it was even more essential for his victims to participate in the process of legal retribution, stating their own cases against the accused. They needed a role and an identity as silent avengers, surrogates of the legal system. They were forever tied to the crime; now they needed to be connected to the punishment. No matter how well intentioned or vicariously vindicating Druce may have been, he was not authorized to serve as judge, jury, and executioner—surely not by the victims he had purportedly sought to benefit.

Addressing the importance of this participatory role, Peter French observed that “the taking of revenge usually produces an emotional or psychological state in the avenger, a feeling of pleasure, a sense of accomplishment, a high. That state cannot fully be experienced if the villain has met his or her end in some natural occurrence, for example, by being buried in an avalanche, unless, of course, the avenger triggered the avalanche with the intent to kill the escaping villain. . . . Unless the avenger is the direct or proximate cause of that ruin, vengeance will not have occurred.”54

Legal philosophers such as Peter French and Jeffrie G. Murphy have set forth three conditions that must be established before an act of revenge can qualify as justified punishment: it must be deserved; the penalty must be in direct proportion to the harm; and the punishing agent or avenger must have the requisite moral authority to do so.⁵⁵ In the case of Geoghan’s prison murder, Druce simply did not have the moral authority to inflict this particular punishment. Revenge works best when the victim participates in the judgment and punishment of the wrongdoer—preferably in concert with the legal process or, if absolutely necessary, as a self-appointed avenger.

Victims have preferences. And those preferences challenge the very premises of rational choice theory or the rational actor model. Victims don’t worry about costs or fitting in within predictive models. They recognize what a free ride looks like but know enough to wave it away. Having already once been treated as disposable cast-offs, victims want to be players in the vindication that vengeance brings. If revenge was all about punishment, if it was all blood and no brains, why would anyone care who delivered the punishment? But victims do care—care deeply, in fact—and not all avengers are authorized to settle the score, especially when it’s not their score to settle. How vengeance is accomplished, and by whom, matters greatly.

At bottom, all victims have an Inigo Montoya speech that they wish to recite. And, in the absence of swashbuckling opportunities for self-help, courtrooms are the ideal settings in which to proclaim publically all of that anguish and rage and to witness justice being done—not in some abstract way, but as a private longing finally fulfilled.