How Hate Works

If you're a heavy metal fan, you've probably heard the Iron Maiden song "There's a Thin Line Between Love and Hate." As it turns out, those lyrics have a grain of truth in them, at least in a neurological sense.

In 2008, scientists at University College London in the U.K. published a study in which they included 17 subjects who'd expressed a strong hatred for another person -- typically, an ex-lover or a colleague. When the subjects' brains were mapped with an MRI scanner while they looked at pictures of the people they hated, activity was observed the putamen and insular cortex -- two brain regions that also light up when a person sees a picture of a loved one [source: Zeki, Robson].

The involvement of the putamen in both emotions is particularly revealing, because that part of the brain also prepares the body for movement. Scientists hypothesize that this area goes into action with the aim of providing protection to a loved one -- to prepare for an aggressive or spiteful act from a hated person [source: Zeki, Robson].

But the researchers also spotted a key difference between the two emotions. When a person sees another person he or she loves, the areas of the frontal cortex associated with judgment and critical thinking typically become less active than normal. But when subjects saw someone they hated, most of the frontal cortex remained active. In fact, the researchers found that when they compared the brain scans to answers that subjects had given on a questionnaire, the more intensively a person said that he or she hated another person, the more energetically the subject's frontal cortex lit up at the sight of the person. So here's the upshot: Hating someone isn't just a knee-jerk emotional reaction. It also involves a certain amount of reasoning and rumination [source: Zeki, Robson].

Hate involves both the interior, primitive parts of the brain and the parts that developed relatively late in human evolution. So our capacity for intense dislike of others of our species may date back as far as 150,000 years, when the first modern humans emerged [source: AMNH.org]. Why hate developed is a murkier question. There's some evidence that humans' ability to hate may actually be an evolutionary adaptation, one that made it easier for a group of hunter-gatherers to justify taking scarce food from competing groups [source: Fishbein].

But even after humans developed agriculture and organized themselves into civilizations, that venomous urge persisted. We'll look at hate's history on the next page.

We know hate's been around for a long time because it's mentioned in texts that date back for centuries. Hate is mentioned in the Book of Genesis and in Indian Vedic scripture [source: Tuske]. The ancient Greeks also contemplated its meaning. Fourth century B.C. philosopher Diogenes Laertius defined hate as "a growing or lasting desire or craving that it should go ill with somebody," and included it among the irrational urges that plagued humankind [source: Diogenes].

The ancients often acted upon their animosity. In the second century B.C., the great Carthaginian general Hannibal pledged to his father eternal hatred against the Romans, who had seized valued provinces from Carthage [source: Lendering]. Hannibal made good on that by invading Italy. But the Romans responded even more venomously. In 146 B.C., they set out to wipe the hated Carthaginians off the face of the Earth, burning down the city's houses as their trapped inhabitants screamed for help [source: BBC].

Hatred was condemned by most of the world's holy scriptures, from the fifth century B.C. Buddhist Dhammapada and the Christian New Testament to the Islamic Koran, which admonishes believers to "let not hatred of a people incite you not to act equitably" [sources: Medieval Sourcebook]. The Muslim Turks behaved similarly hatefully when they sacked the Byzantine Christian capital of Constantinople in 1453, according to the eyewitness account of Nicolo Barbaro, a Venetian physician. He wrote that "anyone [the Turks] found, they put to the scimitar, women and men, old and young, of any condition" [source: Barbaro].

Even in peacetime, it was so common in Medieval and Renaissance Europe to hate others that there was a legal term for it, inimicitia (Latin for "unfriendship") [source: Gibson]. In Italy, such extreme resentments evolved into a custom called the vendetta, in which a person's kinsmen and descendants were obligated to seek vengeance, no matter how long it took [source: Dean].

Despite attempts to ban the vendetta, it persisted and gradually even took root in America. In West Virginia in the late 1800s, a dispute over the alleged theft of a pig mushroomed into a bloody feud between the Hatfield and McCoy families that claimed nearly a half-dozen lives [source: Lugar].

But modern societies have become much more efficient -- and deadly -- at fomenting hatred, as we'll discuss on the next page.

While humans have the basic neural wiring to hate, getting a entire group of people to hate requires convincing them that another person or group of people is evil or dangerous.

Rutgers University sociologist Martin Oppenheimer, who with his family fled Nazi persecution in the 1930s, argues that hate is sown among a group by identifying and exploiting their frustrations, insecurities, and/or fear of losing out on things they want or need. The trick is convincing people that the explanation for their problems is someone else who is threatening to take away things that ought to be theirs, or is a menace to their safety. Additionally, he says, organized hatred helps give meaning to the lives of those who feel marginalized. "These are the movements of growing numbers of the insecure, who seek islands of safety in a rapidly changing and increasingly insecure world," he writes [source: Oppenheimer].

In the modern age, such persuasion to hate has become much easier, thanks to the development of communications technologies that enable hateful words and pictures to be easily disseminated far and wide. A 2010 study by Stanford University researchers Elissa Lee and Laura Leets, who measured teenagers' reaction to hate groups' Web sites, found that storytelling with implicit hate messages, rather than direct exhortations to hate, is the most effective way to persuade impressionable minds [source: Lee and Leets].

In 1915, for example, D.W. Griffith utilized the still-new technology of motion pictures to make "Birth of a Nation," a film that portrayed African-Americans as stupid, lazy and menacing, and glorified the Ku Klux Klan for standing up for the rights of the white majority. It was so effective in fomenting hate against blacks that even Griffith himself was said to have been shocked by what he had wrought [source: Armstrong].

In the 1930s, the Nazi regime in Germany lacked Griffith's qualms. The movie "Jud Suss," filmed at the behest of Nazi propaganda minister Joseph Goebbels, portrayed Jews as greedy and treacherous. It became required viewing for SS storm troopers [source: Connolly]. The Nazis also used radio and put modern presses to work churning out vast numbers of books, like "The Jewish Problem," to build public support for the persecution and eventual murder of millions of Jews across Europe [source: Calvin.edu].

Since then, others around the world have exploited modern media to promote hate. In the 1990s, a Bosnian Serb TV station aired programs like "Genocide" that depicted alleged abuse of Serbs by Bosnian Muslims in an effort to stir up venom and justify ethnic cleansing attacks [source: Hedges]. In the late 1980s, Al Qaeda, the Islamic extremist group founded by Osama bin Laden, learned to exploit the Internet's global reach, launching online chat rooms and blogs and uploading videos to promote hatred of the United States and Israel [source: Moss]. And increasingly, hate-meisters are turning to social networking Web sites and even online games to spread their beliefs and recruit new followers [source: Reuters].

In the United States and elsewhere, Neo-Nazi/white-supremacist groups have even turned to pop music as a means of inciting enmity, forming their own record labels and staging Woodstock-like outdoor festivals where bands perform songs with lyrics like, "I won't calm down until I taste the smell of their blood" [source: ADL.org].

That last line sounds kind of scary. But is such hate really morally wrong? Is it a form of mental illness? Or, are there some instances in which hatred is not only a healthy reaction, but a positive thing? We'll discuss that on the next page.

People filled with hate sometimes do incomprehensible things, from defacing gravestones to stalking and killing people. But is their extreme animosity a form of mental illness?

In 1999, Eric Harris and Dylan Klebold attacked their high school in Columbine, Colo., killing 12 students and a teacher and wounding 24 others, and left behind hateful online rants against society to explain their actions [source: Chua-Eoan]. But it also soon emerged that Harris had been treated with medication for depression, and some believed his despair made him more susceptible to hatred [source: Associated Press]. Other even more notorious hate-mongers, like Hitler and Osama bin Laden, have been diagnosed by mental health experts -- albeit from a safe distance -- as suffering from narcissistic personality disorder and other mental conditions [sources: Coolidge, Diamond].

Based on those examples, it's tempting to jump to the conclusion that those who feel hatred toward others are mentally ill. But that doesn't explain the vast numbers of ordinary Germans and Bosnian Serbs who morphed from friendly neighbors to eager murderers of their countrymen. That's why some mental health experts think that if the tendency to hate is a disease, it's more akin to herpes than a rare cancer.

Early 20th century psychoanalytic pioneer Sigmund Freud, for example, regarded hate as a normal, albeit unpleasant, byproduct of an individual's struggle to maintain and preserve his or her ego in the face of civilization's pressures [source: Abel]. Others think that even ordinary, well-socialized people can be induced to hate others, if they're subjected to sufficient trauma. A 2000 study of adults from war-torn Kosovo, for example, found that those who had suffered the most psychological stress and illness also tended to harbor the most extreme feelings of hatred toward the Serbian troops who had been their tormentors [source: Healy].

But others say that, like a loaded gun, hatred isn't inherently bad -- that it's merely a capacity that can be used for good as well as evil. Psychiatrist and writer Kurt R. Eissler, for example, defended "noble hatred," in which an intense aversion is put to a constructive use, such as overthrowing a cruel dictator. "The activation of compassion would only diminish the impetus of his attack against superior power," he wrote. For a revolutionary fighting against injustice, Eissler argued that hatred is not only normal, but actually can be a positive tool for all of us [source: Bartlett].