"As for the patients who became involved in porn, most were able to go cold turkey once they understood the problem and how they were plastically reinforcing it. They found eventually that they were attracted once again to their mates. . . . when they understood what was happening to them, they stopped . . ."

"All addiction involves long-term, sometimes lifelong, neuroplastic change in the brain. . . . The men at their computers looking at porn were uncannily like the rats in the cages of the NIH, pressing the bar to get a shot of dopamine or its equivalent. Though they didn't know it, they had been seduced into pornographic training sessions that met all the conditions required for plastic change of brain maps. Since neurons that fire together wire together, these men got massive amounts of practice wiring these images into the pleasure centers of the brain, with the rapt attention necessary for plastic change."

WARNING: Not Suitable Reading For Children! — Dr. Norman Doidge is a medical doctor with expertise in brain neuroplasticity, and he has helped uncover information which frees many people from their addictions to internet pornography. The following story contains frank discussion regarding illicit sexual acts. The reader's discretion is advised.



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The human libido is not a hardwired, invariable biological urge but can be curiously fickle, easily altered by our psychology and the history of our sexual encounters. And our libido can also be finicky. Much scientific writing implies otherwise and depicts the sexual instinct as a biological imperative, an everhungry brute, always demanding satisfaction — a glutton, not a gourmet. But human beings are more like gourmets and are drawn to types and have strong preferences; having a "type" causes us to defer satisfaction until we find what we are looking for, because attraction to a type is restrictive: the person who is "really turned on by blondes" may tacitly rule out brunettes and redheads.

Given that sexuality is an instinct, and instinct is traditionally defined as a hereditary behavior unique to a species, varying little from one member to the next, the variety of our sexual tastes is curious. Instincts generally resist change and are thought to have a clear, non-negotiable, hardwired purpose, such as survival. Yet the human sexual "instinct" seems to have broken free of its core purpose, reproduction, and varies to a bewildering extent, as it does not in other animals, in which the sexual instinct seems to behave itself and act like an instinct. No other instinct can so satisfy without accomplishing its biological purpose, and no other instinct is so disconnected from its purpose.

Love too is remarkably flexible, and its expression has changed through history. Though we speak of romantic love as the most natural of sentiments, in fact the concentration of our adult hopes for intimacy, tenderness, and lust in one person until death do us part is not common to all societies and has only recently become widespread in our own. For millennia most marriages were arranged by parents for practical reasons.

Certainly, there are unforgettable stories of romantic love linked to marriage in the Bible, as in the Song of Songs, and linked to disaster in medieval troubadour poetry and, later, in Shakespeare. But romantic love began to gain social approval in the aristocracies and courts of Europe only in the twelfth century — originally between an unmarried man and a married woman, either adulterous or unconsummated, usually ending badly. Only with the spread of democratic ideals of individualism did the idea that lovers ought to be able to choose spouses for themselves take firmer hold and gradually begin to seem completely natural and inalienable.

It is reasonable to ask whether our sexual plasticity is related to neuroplasticity. Research has shown that neuroplasticity is neither ghettoized within certain departments in the brain nor confined to the sensory, motor, and cognitive processing areas we have already explored. The brain structure that regulates instinctive behaviors, including sex, called the hypothalamus, is plastic, as is the amygdala, the structure that processes emotion and anxiety. While some parts of the brain, such as the cortex, may have more plastic potential because there are more neurons and connections to be altered, even noncortical areas display plasticity. It is a property of all brain tissue.

Plasticity exists in the hippocampus (the area that turns our memories from short-term to long-term ones) as well as in areas that control our breathing, process primitive sensation, and process pain. It exists in the spinal cord — as scientists have shown; actor Christopher Reeve, who suffered a severe spinal injury, demonstrated such plasticity, when he was able, through relentless exercise, to recover some feeling and mobility seven years after his accident. Merzenich puts it this way: "You cannot have plasticity in isolation ... it's an absolute impossibility." His experiments have shown that if one brain system changes, those systems connected to it change as well. The same "plastic rules" — use it or lose it, or neurons that fire together wire together — apply throughout. Different areas of the brain wouldn't be able to function together if that weren't the case.

Do the same plastic rules that apply to brain maps in the sensory, motor, and language cortices apply to more complex maps, such as those that represent our relationships, sexual or otherwise? Merzenich has also shown that complex brain maps are governed by the same plastic principles as simpler maps.

But the main point is that in our critical periods we can acquire sexual and romantic tastes and inclinations that get wired into our brains and can have a powerful impact for the rest of our lives. And the fact that we can acquire different sexual tastes contributes to the tremendous sexual variation between us. The idea that a critical period helps shape sexual desire in adults contradicts the currently popular argument that what attracts us is less the product of our personal history than of our common biology.

Certain people — models and movie stars, for instance — are widely regarded as beautiful or sexy. A certain strand of biology teaches us that these people are attractive because they exhibit biological signs of robustness, which promise fertility and strength: a clear complexion and symmetrical features mean a potential mate is free from disease; an hourglass figure is a sign a woman is fertile; a man's muscles predict he will be able to protect a woman and her offspring.

But this simplifies what biology really teaches. Not everyone falls in love with the body, as when a woman says, "I knew, when I first heard that voice, that he was for me," the music of the voice being perhaps a better indication of a man's soul than his body's surface. And sexual taste has changed over the centuries. Rubens's beauties were large by current standards, and over the decades the vital statistics of Playboy centerfolds and fashion models have varied from voluptuous to androgynous. Sexual taste is obviously influenced by culture and experience and is often acquired and then wired into the brain.

"Acquired tastes" are by definition learned, unlike "tastes," which are inborn. A baby needn't acquire a taste for milk, water, or sweets; these are immediately perceived as pleasant. Acquired tastes are initially experienced with indifference or dislike but later become pleasant — the odors of cheeses, Italian bitters, dry wines, coffees, pates, the hint of urine in a fried kidney. Many delicacies that people pay dearly for, that they must "develop a taste for," are the very foods that disgusted them as children.

In Elizabethan times lovers were so enamored of each other's body odors that it was common for a woman to keep a peeled apple in her armpit until it had absorbed her sweat and smell. She would give this "love apple" to her lover to sniff at in her absence. We, on the other hand, use synthetic aromas of fruits and flowers to mask our body odor from our lovers. Which of these two approaches is acquired and which is natural is not so easy to determine. A substance as "naturally" repugnant to us as the urine of cows is used by the Masai tribe in East Africa as a lotion for their hair — a direct consequence of the cow's importance in their culture. Many tastes we think "natural" are acquired through learning and become "second nature" to us. We are unable to distinguish our "second nature" from our "original nature" because our neuroplastic brains, once rewired, develop a new nature, every bit as biological as our original.

The current porn epidemic gives a graphic demonstration that sexual tastes can be acquired. Pornography, delivered by highspeed Internet connections, satisfies every one of the prerequisites for neuroplastic change. Pornography seems, at first glance, to be a purely instinctual matter: sexually explicit pictures trigger instinctual responses. The same triggers, bodily parts and their proportions, that appealed to our ancestors would excite us. This is what pornographers would have us believe, for they claim they are battling sexual repression, taboo, and fear and that their goal is to liberate the natural, pent-up sexual instincts.

But in fact the content of pornography is a dynamic phenomenon that perfectly illustrates the progress of an acquired taste. Thirty years ago "hardcore" pornography usually meant the explicit depiction of sexual intercourse between two aroused partners, displaying their genitals. "Softcore" meant pictures of women, mostly, on a bed, at their toilette, or in some semiromantic setting, in various states of undress, breasts revealed. Now hardcore has evolved and is increasingly dominated by the sadomasochistic themes of forced sex, ejaculations on women's faces, and angry anal sex, all involving scripts fusing sex with hatred and humiliation. Hardcore pornography now explores the world of perversion, while softcore is now what hardcore was a few decades ago, explicit sexual intercourse between adults, now available on cable TV. The comparatively tame softcore pictures of yesteryear — women in various states of undress — now show up on mainstream media all day long, in the pornification of everything, including television, rock videos, soap operas, advertisements, and so on.

Pornography's growth has been extraordinary; it accounts for 25 percent of video rentals and is the fourth most common reason people give for going online. An MSNBC.com survey of viewers in 2001 found that 80 percent felt they were spending so much time on pornographic sites that they were putting their relationships or jobs at risk. Softcore pornography's influence is now most profound because, now that it is no longer hidden, it influences young people with little sexual experience and especially plastic minds, in the process of forming their sexual tastes and desires. Yet the plastic influence of pornography on adults can also be profound, and those who use it have no sense of the extent to which their brains are reshaped by it.

During the mid- to late 1990s, when the Internet was growing rapidly and pornography was exploding on it, I treated or assessed a number of men who all had essentially the same story. Each had acquired a taste for a kind of pornography that, to a greater or lesser degree, troubled or even disgusted him, had a disturbing effect on the pattern of his sexual excitement, and ultimately affected his relationships and sexual potency. None of these men were fundamentally immature, socially awkward, or withdrawn from the world into a massive pornography collection that was a substitute for relationships with real women. These were pleasant, generally thoughtful men, in reasonably successful relationships or marriages.

Typically, while I was treating one of these men for some other problem, he would report, almost as an aside and with telling discomfort, that he found himself spending more and more time on the Internet, looking at pornography and masturbating. He might try to ease his discomfort by asserting that everybody did it. In some cases he would begin by looking at a Playboy-type site or at a nude picture or video clip that someone had sent him as a lark. In other cases he would visit a harmless site, with a suggestive ad that redirected him to risque sites, and soon he would be hooked.

A number of these men also reported something else, often in passing, that caught my attention. They reported increasing difficulty in being turned on by their actual sexual partners, spouses or girlfriends, though they still considered them objectively attractive. When I asked if this phenomenon had any relationship to viewing pornography, they answered that it initially helped them get more excited during sex but over time had the opposite effect.

Now, instead of using their senses to enjoy being in bed, in the present, with their partners, lovemaking increasingly required them to fantasize that they were part of a porn script. Some gently tried to persuade their lovers to act like porn stars, and they were increasingly interested in "fucking" as opposed to "making love." Their sexual fantasy lives were increasingly dominated by the scenarios that they had, so to speak, downloaded into their brains, and these new scripts were often more primitive and more violent than their previous sexual fantasies. I got the impression that any sexual creativity these men had was dying and that they were becoming addicted to Internet porn.

The changes I observed are not confined to a few people in therapy. A social shift is occurring. While it is usually difficult to get information about private sexual mores, this is not the case with pornography today, because its use is increasingly public. This shift coincides with the change from calling it "pornography" to the more casual term "porn."

For his book on American campus life, I Am Charlotte Simmons, Tom Wolfe spent a number of years observing students on university campuses. In the book one boy, Ivy Peters, comes into the male residence and says, "Anybody got porn?" Wolfe goes on, "This was not an unusual request. Many boys spoke openly about how they masturbated at least once every day, as if this were some sort of prudent maintenance of the psychosexual system." One of the boys tells Ivy Peters, "Try the third floor. They got some one-hand magazines up there." But Peters responds, "I've built up a tolerance to magazines ... I need videos." Another boy says, "Oh, f'r Chrissake, I.P., it's ten o'clock at night. In another hour the cum dumpsters will start coming over here to spend the night. . . And you're looking for porn videos and a knuckle fuck." Then Ivy "shrugged and turned his palms up as if to say, 'I want porn. What's the big deal?'"

The big deal is his tolerance. He recognizes that he is like a drug addict who can no longer get high on the images that once turned him on. And the danger is that this tolerance will carry over into relationships, as it did in patients whom I was seeing, leading to potency problems and new, at times unwelcome, tastes. When pornographers boast that they are pushing the envelope by introducing new, harder themes, what they don't say is that they must, because their customers are building up a tolerance to the content.

The back pages of men's risque magazines and Internet porn sites are filled with ads for Viagra-type drugs — medicine developed for older men with erectile problems related to aging and blocked blood vessels in the penis. Today young men who surf porn are tremendously fearful of impotence, or "erectile dysfunction" as it is euphemistically called. The misleading term implies that these men have a problem in their penises, but the problem is in their heads, in their sexual brain maps. The penis works fine when they use pornography. It rarely occurs to them that there may be a relationship between the pornography they are consuming and their impotence. (A few men, however, tellingly described their hours at computer porn sites as time spent "masturbating my brains out.") One of the boys in Wolfe's scene describes the girls who are coming over to have sex with their boyfriends as "cum dumpsters." He too is influenced by porn images, for "cum dumpsters," like many women in porn films, are always eager, available receptacles and therefore devalued.

The addictiveness of Internet pornography is not a metaphor. Not all addictions are to drugs or alcohol. People can be seriously addicted to gambling, even to running. All addicts show a loss of control of the activity, compulsively seek it out despite negative consequences, develop tolerance so that they need higher and higher levels of stimulation for satisfaction, and experience withdrawal if they can't consummate the addictive act. All addiction involves long-term, sometimes lifelong, neuroplastic change in the brain.

For addicts, moderation is impossible, and they must avoid the substance or activity completely if they are to avoid addictive behaviors. Alcoholics Anonymous insists that there are no "former alcoholics" and makes people who haven't had a drink for decades introduce themselves at a meeting by saying, "My name is John, and I am an alcoholic." In terms of plasticity, they are often correct. In order to determine how addictive a street drug is, researchers at the National Institutes of Health (NIH) in Maryland train a rat to press a bar until it gets a shot of the drug. The harder the animal is willing to work to press the bar, the more addictive the drug.

Cocaine, almost all other illegal drugs, and even nondrug addictions such as running make the pleasure-giving neurotransmitter dopamine more active in the brain. Dopamine is called the reward transmitter, because when we accomplish something — run a race and win — our brain triggers its release. Though exhausted, we get a surge of energy, exciting pleasure, and confidence and even raise our hands and run a victory lap. The losers, on the other hand, who get no such dopamine surge, immediately run out of energy, collapse at the finish line, and feel awful about themselves.

By hijacking our dopamine system, addictive substances give us pleasure without our having to work for it.

Dopamine, as we saw in Merzenich's work, is also involved in plastic change. The same surge of dopamine that thrills us also consolidates the neuronal connections responsible for the behaviors that led us to accomplish our goal. When Merzenich used an electrode to stimulate an animal's dopamine reward system while playing a sound, dopamine release stimulated plastic change, enlarging the representation for the sound in the animal's auditory map.

An important link with porn is that dopamine is also released in sexual excitement, increasing the sex drive in both sexes, facilitating orgasm, and activating the brain's pleasure centers. Hence the addictive power of pornography. Eric Nestler, at the University of Texas, has shown how addictions cause permanent changes in the brains of animals. A single dose of many addictive drugs will produce a protein, called ΔFosB (pronounced "delta Fos B"), that accumulates in the neurons. Each time the drug is used, more ΔFosB accumulates, until it throws a genetic switch, affecting which genes are turned on or off. Flipping this switch causes changes that persist long after the drug is stopped, leading to irreversible damage to the brain's dopamine system and rendering the animal far more prone to addiction. Nondrug addictions, such as running and sucrose drinking, also lead to the accumulation of ΔFosB and the same permanent changes in the dopamine system.

Pornographers promise healthy pleasure and relief from sexual tension, but what they often deliver is an addiction, tolerance, and an eventual decrease in pleasure. Paradoxically, the male patients I worked with often craved pornography but didn't like it. The usual view is that an addict goes back for more of his fix because he likes the pleasure it gives and doesn't like the pain of withdrawal. But addicts take drugs when there is no prospect of pleasure, when they know they have an insufficient dose to make them high, and will crave more even before they begin to withdraw. Wanting and liking are two different things.

An addict experiences cravings because his plastic brain has become sensitized to the drug or the experience. Sensitization is different from tolerance. As tolerance develops, the addict needs more and more of a substance or porn to get a pleasant effect; as sensitization develops, he needs less and less of the substance to crave it intensely. So sensitization leads to increased wanting, though not necessarily liking. It is the accumulation of ΔFosB, caused by exposure to an addictive substance or activity, that leads to sensitization.

Pornography is more exciting than satisfying because we have two separate pleasure systems in our brains, one that has to do with exciting pleasure and one with satisfying pleasure. The exciting system relates to the "appetitive" pleasure that we get imagining something we desire, such as sex or a good meal. Its neurochemistry is largely dopamine-related, and it raises our tension level. The second pleasure system has to do with the satisfaction, or consummatory pleasure, that attends actually having sex or having that meal, a calming, fulfilling pleasure. Its neurochemistry is based on the release of endorphins, which are related to opiates and give a peaceful, euphoric bliss.

Pornography, by offering an endless harem of sexual objects, hyperactivates the appetitive system. Porn viewers develop new maps in their brains, based on the photos and videos they see. Because it is a use-it-or-lose-it brain, when we develop a map area, we long to keep it activated. Just as our muscles become impatient for exercise if we've been sitting all day, so too do our senses hunger to be stimulated.

The men at their computers looking at porn were uncannily like the rats in the cages of the NIH, pressing the bar to get a shot of dopamine or its equivalent. Though they didn't know it, they had been seduced into pornographic training sessions that met all the conditions required for plastic change of brain maps. Since neurons that fire together wire together, these men got massive amounts of practice wiring these images into the pleasure centers of the brain, with the rapt attention necessary for plastic change.

They imagined these images when away from their computers, or while having sex with their girlfriends, reinforcing them. Each time they felt sexual excitement and had an orgasm when they masturbated, a "spritz of dopamine," the reward neurotransmitter, consolidated the connections made in the brain during the sessions. Not only did the reward facilitate the behavior; it provoked none of the embarrassment they felt purchasing Playboy at a store. Here was a behavior with no "punishment," only reward. The content of what they found exciting changed as the Web sites introduced themes and scripts that altered their brains without their awareness. Because plasticity is competitive, the brain maps for new, exciting images increased at the expense of what had previously attracted them — the reason, I believe, they began to find their girlfriends less of a turn-on.

The story of Sean Thomas, first published in England's Spectator, is a remarkable account of a man descending into a porn addiction, and it sheds light on how porn changes brain maps and alters sexual taste, as well as the role of critical-period plasticity in the process. Thomas wrote, "I never used to like pornography, not really. Yes, in my teens in the Seventies I used to have the odd copy of Playboy under my pillow. But on the whole I didn't really go for skin mags or blue movies. I found them tedious, repetitive, absurd, and very embarrassing to buy." He was repelled by the bleakness of the porn scene and the garishness of the mustachioed studs who inhabited it.

But in 2001, shortly after he first went online, he got curious about the porn everyone said was taking over the Internet. Many of the sites were free — teasers, or "gateway sites," to get people into the harder stuff. There were galleries of naked girls, of common types of sexual fantasies and attractions, designed to press a button in the brain of the surfer, even one he didn't know he had. There were pictures of lesbians in a Jacuzzi, cartoon porn, women on the toilet smoking, coeds, group sex, and men ejaculating over submissive Asian women. Most of the pictures told a story. Thomas found a few images and scripts that appealed to him, and they "dragged me back for more the next day. And the next. And the next." Soon he found that whenever he had a spare minute, he would "start hungrily checking out Net Porn."

Then one day he came across a site that featured spanking images. To his surprise, he got intensely excited. Thomas soon found all sorts of related sites, such as "Bernie's Spanking Pages" and the "Spanking College." "This was the moment," he writes, "that the real addiction set in. My interest in spanking got me speculating: What other kinks was I harboring? What other secret and rewarding corners lurked in my sexuality that I would now be able to investigate in the privacy of my home? Plenty, as it turned out. I discovered a serious penchant for, inter alia, lesbian gynecology, interracial hardcore, and images of Japanese girls taking off their hotpants. I was also into netball players with no knickers, drunk Russian girls exposing themselves, and convoluted scenarios where submissive Danish actresses were intimately shaved by their dominant female partners in the shower. The Net had, in other words, revealed to me that I had an unquantifiable variety of sexual fantasies and quirks and that the process of satisfying these desires online only led to more interest."

Until he happened upon the spanking pictures, which presumably tapped into some childhood experience or fantasy about being punished, the images he saw interested him but didn't compel him. Other people's sexual fantasies bore us. Thomas's experience was similar to that of my patients: without being fully aware of what they were looking for, they scanned hundreds of images and scenarios until they hit upon an image or sexual script that touched some buried theme that really excited them. Once Thomas found that image, he changed. That spanking image had his focused attention, the condition for plastic change.

And unlike a real woman, these porn images were available all day, every day on the computer. Now Thomas was hooked. He tried to control himself but was spending at least five hours a day on his laptop. He surfed secretly, sleeping only three hours a night. His girlfriend, aware of his exhaustion, wondered if he was seeing someone else. He became so sleep deprived that his health suffered, and he got a series of infections that landed him in a hospital emergency room and finally caused him to take stock. He began inquiring among his male friends and found that many of them were also hooked. Clearly there was something about Thomas's sexuality, outside his awareness, that had suddenly surfaced.

Does the net simply reveal quirks and kinks, or does it also help create them? I think it creates new fantasies out of aspects of sexuality that have been outside the surfer's conscious awareness, bringing these elements together to form new networks. It is not likely that thousands of men have witnessed, or even imagined, submissive Danish actresses intimately shaved by their dominant female partners in the shower.

Hardcore porn unmasks some of the early neural networks that formed in the critical periods of sexual development and brings all these early, forgotten, or repressed elements together to form a new network, in which all the features are wired together. Porn sites generate catalogs of common kinks and mix them together in images. Sooner or later the surfer finds a killer combination that presses a number of his sexual buttons at once. Then he reinforces the network by viewing the images repeatedly, masturbating, releasing dopamine and strengthening these networks. He has created a kind of "neosexuality," a rebuilt libido that has strong roots in his buried sexual tendencies.

Because he often develops tolerance, the pleasure of sexual discharge must be supplemented with the pleasure of an aggressive release, and sexual and aggressive images are increasingly mingled — hence the increase in sadomasochistic themes in hardcore porn. Critical periods lay the groundwork for our types, but falling in love in adolescence or later provides an opportunity for a second round of massive plastic change.

Stendhal, the nineteenth-century novelist and essayist, understood that love could lead to radical changes in attraction. Romantic love triggers such powerful emotion that we can reconfigure what we find attractive, even overcoming "objective" beauty. In On Love Stendhal describes a young man, Alberic, who meets a woman more beautiful than his mistress. Yet Alberic is far more drawn to his mistress than to this woman because his mistress promises him so much more happiness. Stendhal calls this "Beauty Dethroned by Love." Love has such power to change attraction that Alberic is turned on by a minor defect on his mistress's face, her pockmark. It excites him because "he has experienced so many emotions in the presence of that pockmark, emotions for the most part exquisite and of the most absorbing interest, that whatever his emotions may have been, they are renewed with incredible vividness at the sight of this sign, even observed on the face of another woman ... in this case ugliness becomes beauty."

This transformation of taste can happen because we do not fall in love with looks alone. Under normal circumstances finding another person attractive can prompt a readiness to fall in love, but that person's character and a host of other attributes, including his ability to make us feel good about ourselves, crystallize the process of falling in love. Then being in love triggers an emotional state so pleasurable that it can make even pockmarks attractive, plastically rewiring our aesthetic sense.

Here is how I believe it works. In 1950, "pleasure centers" were discovered in the limbic system, a part of the brain heavily involved in processing emotion. In Dr. Robert Heath's experiments on humans — an electrode was implanted into the septal region of the limbic system and turned on — these patients experienced a euphoria so powerful that when the researchers tried to end the experiment, one patient pleaded with them not to. The septal region also fired when pleasant subjects were discussed with the patients and during orgasm. These pleasure centers were found to be part of the brain's reward system, the mesolimbic dopamine system. In 1954 James Olds and Peter Milner showed that when they inserted electrodes into an animal's pleasure center while teaching it a task, it learned more easily because learning felt so pleasurable and was rewarded.

When the pleasure centers are turned on, everything we experience gives us pleasure. A drug like cocaine acts on us by lowering the threshold at which our pleasure centers will fire, making it easier for them to turn on. It is not simply the cocaine that gives us pleasure. It is the fact that our pleasure centers now fire so easily that makes whatever we experience feel great. It is not just cocaine that can lower the threshold at which our pleasure centers fire. When people with bipolar disorder (formerly called manic depression) begin to move toward their manic highs, their pleasure centers begin firing more easily. And falling in love also lowers the threshold at which the pleasure centers will fire. When a person gets high on cocaine, becomes manic, or falls in love, he enters an enthusiastic state and is optimistic about everything, because all three conditions lower the firing threshold for the appetitive pleasure system, the dopamine-based system associated with the pleasure of anticipating something we desire.

The addict, the manic, and the lover are increasingly filled with hopeful anticipation and are sensitive to anything that might give pleasure — flowers and fresh air inspire them, and a slight but thoughtful gesture makes them delight in all mankind. I call this process "globalization." Globalization is intense when falling in love and is, I believe, one of the main reasons that romantic love is such a powerful catalyst for plastic change. Because the pleasure centers are firing so freely, the enamored person falls in love not only with the beloved but with the world and romanticizes his view of it. Because our brains are experiencing a surge of dopamine, which consolidates plastic change, any pleasurable experiences and associations we have in the initial state of love are thus wired into our brains.

Globalization not only allows us to take more pleasure in the world, it also makes it harder for us to experience pain and displeasure or aversion. Heath showed that when our pleasure centers fire, it is more difficult for the nearby pain and aversion centers to fire too. Things that normally bother us don't. We love being in love not only because it makes it easy for us to be happy but also because it makes it harder for us to be unhappy. Globalization also creates an opportunity for us to develop new tastes in what we find attractive, like the pockmark that gave Alberic such pleasure. Neurons that fire together wire together, and feeling pleasure in the presence of this normally unappealing pockmark causes it to get wired into the brain as a source of delight.

A similar mechanism occurs when a "reformed" cocaine addict passes the seedy alleyway where he first took the drug and is overwhelmed with cravings so powerful that he goes back to it. The pleasure he felt during the high was so intense that it caused him to experience the ugly alleyway as enticing, by association. There is thus a literal chemistry of love, and the stages of romance reflect the changes in our brain during not only the ecstasies but also love's throes.

Recent fMRI (functional magnetic resonance imaging) scans of lovers looking at photos of their sweethearts show that a part of the brain with great concentrations of dopamine is activated; their brains looked like those of people on cocaine. But the pains of love also have a chemistry. When separated for too long, lovers crash and experience withdrawal, crave their beloved, get anxious, doubt themselves, lose their energy, and feel run-down if not depressed. Like a little fix, a letter, an e-mail, or a telephone message from the beloved provides an instant shot of energy. Should they break up, they get depressed — the opposite of the manic high. These "addictive symptoms" — the highs, crashes, cravings, withdrawal, and fixes — are subjective signs of plastic changes occurring in the structure of our brains, as they adapt to the presence or absence of the beloved.

A tolerance, akin to tolerance for a drug, can develop in happy lovers as they get used to each other. Dopamine likes novelty. When monogamous mates develop a tolerance for each other and lose the romantic high they once had, the change may be a sign, not that either of them is inadequate or boring, but that their plastic brains have so well adapted to each other that it's harder for them to get the same buzz they once got from each other.

Fortunately, lovers can stimulate their dopamine, keeping the high alive, by injecting novelty into their relationship. When a couple go on a romantic vacation or try new activities together, or wear new kinds of clothing, or surprise each other, they are using novelty to turn on the pleasure centers, so that everything they experience, including each other, excites and pleases them. Once the pleasure centers are turned on and globalization begins, the new image of the beloved again becomes associated with unexpected pleasures and is plastically wired into the brain, which has evolved to respond to novelty. We must be learning if we are to feel fully alive, and when life, or love, becomes too predictable and it seems like there is little left to learn, we become restless — a protest, perhaps, of the plastic brain when it can no longer perform its essential task.

Love creates a generous state of mind. Because love allows us to experience as pleasurable situations or physical features that we otherwise might not, it also allows us to unlearn negative associations, another plastic phenomenon. The science of unlearning is a very new one. Because plasticity is competitive, when a person develops a neural network, it becomes efficient and self-sustaining and, like a habit, hard to unlearn. Recall that Merzenich was looking for "an eraser" to help him speed up change and unlearn bad habits.

Different chemistries are involved in learning than in unlearning. When we learn something new, neurons fire together and wire together, and a chemical process occurs at the neuronal level called "long-term potentiation," or LTP, which strengthens the connections between the neurons. When the brain unlearns associations and disconnects neurons, another chemical process occurs, called "long-term depression," or LTD (which has nothing to do with a depressed mood state).

Unlearning and weakening connections between neurons is just as plastic a process, and just as important, as learning and strengthening them. If we only strengthened connections, our neuronal networks would get saturated. Evidence suggests that unlearning existing memories is necessary to make room for new memories in our networks. Unlearning is essential when we are moving from one developmental stage to the next. When at the end of adolescence a girl leaves home to go to college in another state, for example, both she and her parents undergo grief and massive plastic change, as they alter old emotional habits, routines, and self-images.

Falling in love for the first time also means entering a new developmental stage and demands a massive amount of unlearning. When people commit to each other, they must radically alter their existing and often selfish intentions and modify all other attachments, in order to integrate the new person in their lives. Life now involves ongoing cooperation that requires a plastic reorganization of the brain centers that deal with emotions, sexuality, and the self. Millions of neural networks have to be obliterated and replaced with new ones — one reason that falling in love feels, for so many people, like a loss of identity.

Falling in love may also mean falling out of love with a past love; this too requires unlearning at a neural level. A man's heart is broken by his first love when his engagement breaks off. He looks at many women, but each pales in comparison to the fiancée he came to believe was his one true love and whose image haunts him. He cannot unlearn the pattern of attraction to his first love. Or a woman married for twenty years becomes a young widow and refuses to date. She cannot imagine she will ever fall in love again, and the idea of "replacing" her husband offends her. Years pass, and her friends tell her it is time to move on, to no avail. Often such people cannot move on because they cannot yet grieve; the thought of living without the one they love is too painful to bear. In neuroplastic terms, if the romantic or the widow is to begin a new relationship without baggage, each must first rewire billions of connections in their brains.

The work of mourning is piecemeal. We grieve by calling up one memory at a time, reliving it, and then letting it go. At a brain level we are turning on each of the neural networks that were wired together to form our perception of the person, experiencing the memory with exceptional vividness, then saying good-bye one network at a time. In grief, we learn to live without the one we love, but the reason this lesson is so hard is that we first must unlearn the idea that the person exists and can still be relied on.

Walter J. Freeman, a professor of neuroscience at Berkeley, was the first to make the connection between love and massive unlearning. He has assembled a number of compelling biological facts that point toward the conclusion that massive neuronal reorganization occurs at two life stages: when we fall in love and when we begin parenting. Freeman argues that massive plastic brain reorganization — far more massive than in normal learning or unlearning — becomes possible because of a brain neuromodulator.

Neuromodulators are different from neurotransmitters. While neurotransmitters are released in the synapses to excite or inhibit neurons, neuromodulators enhance or diminish the overall effectiveness of the synaptic connections and bring about enduring change. Freeman believes that when we commit in love, the brain neuromodulator oxytocin is released, allowing existing neuronal connections to melt away so that changes on a large scale can follow. Oxytocin is sometimes called the commitment neuromodulator because it reinforces bonding in mammals. It is released when lovers connect and make love — in humans oxytocin is released in both sexes during orgasm — and when couples parent and nurture their children. In women oxytocin is released during labor and breastfeeding. An fMRI study shows that when mothers look at photos of their children, brain regions rich in oxytocin are activated. In male mammals a closely related neuromodulator called vasopressin is released when they become fathers.

Many young people who doubt they will be able to handle the responsibilities of parenting are not aware of the extent to which oxytocin may change their brains, allowing them to rise to the occasion. Studies of a monogamous animal called the prairie vole have shown that oxytocin, which is normally released in their brains during mating, makes them pair off for life. If a female vole has oxytocin injected into her brain, she will pair-bond for life with a nearby male. If a male vole is injected with vasopressin, it will cuddle with a nearby female.

Oxytocin appears also to attach children to parents, and the neurons that control its secretion may have a critical period of their own, Children reared in orphanages without close loving contact often have bonding problems when older. Their oxytocin levels remain low for several years after they have been adopted by loving families.

Whereas dopamine induces excitement, puts us into high gear, and triggers sexual arousal, oxytocin induces a calm, warm mood that increases tender feelings and attachment and may lead us to lower our guard. A recent study shows that oxytocin also triggers trust. When people sniff oxytocin and then participate in a financial game, they are more prone to trust others with their money. Though there is still more work to be done on oxytocin in humans, evidence suggests that its effect is similar to that in prairie voles: it makes us commit to our partners and devotes us to our children.

But oxytocin works in a unique way, related to unlearning. In sheep, oxytocin is released in the olfactory bulb, a part of the brain involved in odor perception, with each new litter. Sheep and many other animals bond with, or "imprint" on, their offspring by scent. They mother their own lambs and reject the unfamiliar. But if oxytocin is injected into a mother ewe when exposed to an unfamiliar lamb, she will mother the strange lamb too. Oxytocin is not, however, released with the first litter — only with those litters that follow — suggesting that the oxytocin plays the role of wiping out the neural circuits that bonded the mother with her first litter, so she can bond with her second. (Freeman suspects that the mother bonds with her first litter using other neurochemicals.) Oxytocin's ability to wipe out learned behavior has led scientists to call it an amnestic hormone. Freeman proposes that oxytocin melts down existing neuronal connections that underlie existing attachments, so new attachments can be formed. Oxytocin, in this theory, does not teach parents to parent. Nor does it make lovers cooperative and kind; rather, it makes it possible for them to learn new patterns. . . .

. . . As for the patients who became involved in porn, most were able to go cold turkey once they understood the problem and how they were plastically reinforcing it. They found eventually that they were attracted once again to their mates. None of these men had addictive personalities or serious childhood traumas, and when they understood what was happening to them, they stopped using their computers for a period to weaken their problematic neuronal networks, and their appetite for porn withered away. Their treatment for sexual tastes acquired later in life was far simpler than that for patients who, in their critical periods, acquired a preference for problematic sexual types. Yet even some of these men were able, like A., to change their sexual type, because the same laws of neuroplasticity that allow us to acquire problematic tastes also allow us, in intensive treatment, to acquire newer, healthier ones and in some cases even to lose our older, troubling ones. It's a use-it-or-lose-it brain, even where sexual desire and love are concerned. . . .

To read more, pick up a copy of The Brain That Changes Itself, by Norman Doidge, M.D. This book is available for purchase on Amazon.com.