Source: Sunday Times
Date: 12 February 2006

Love is the drug

Falling head over heels for someone can feel heavenly or hellish.
But can scientists explain what's really happening?
John Cornwell reports

There's a joke e-mail doing the rounds of the neuroscience labs: "Why did the chicken cross the road?" To which: "Because its dopaminergic neurons fired synchronously across the synapses of its caudate nucleus, triggering motor contractions propelling the organism forward, while emitting 'cluck' distress signals, to a goal predetermined by its hippocampal road mappings." The anorak drollery is, of course, about explanation: the absurdity of applying physiological descriptions to profound "why" questions. Love of family, and platonic love, are not so susceptible to scientific probing. But since my first disastrous infatuation with a girl I believed to be my eternal soul mate, I've been convinced that romantic love, RL, is a profoundly physical rather than spiritual phenomenon.

In RL, our neurons and our hormones, our brains and our blood pressure, our stomachs and hearts, are in a state of upheaval. And if we check out the behaviour of our close primate relatives, we can detect links between human bonding of the RL type, and evolutionary survival pressures. In fact, there's no area of physiology, or behavioural and evolutionary biology, that doesn't boast an explanatory claim to RL.

The feeling that RL is akin to being "besotted" lies deep in western folk memory. From the ancient Greek myth of the centaur Nessus and his dangerous love potions, to E M Forster's lovesick Maurice's complaint that he is "drugged", our forebears have characterised RL as a potent substance. But is it generated within, or outside, the body? Many of our ancestors cited external influences: drugged arrows, spells, planetary forces, charms, potions.

A medieval recipe for a "true-love powder" states: "Take elecampane, the seeds and flowers of vervain, and the berries of mistletoe. Beat them, after being well dried in an oven, into a powder, and give it to the party you design upon in a glass of wine and it will work wonderful effect to your advantage."

But Galen, the 2nd-century Greek "prince of physicians", insisted that the affliction was purely a matter of internal chemistry. It's what happens, he asserted, when the crucial four bodily fluids, or humours — yellow bile, black bile, phlegm and blood — get into a muddle. For Galen's followers, right down to Robert Burton, author of The Anatomy of Melancholy, the theory of humoralism held good. Galen was eventually displaced by 19th-century theories of cell biology, but modern physiologists nevertheless share his broad conviction that RL is induced by powerful natural bodily chemicals. In our own day, the favoured chemical explanation focuses on a molecule called PEA: phenylethylamine, a kind of natural amphetamine that revs up the brain and the central nervous system. PEA causes the experience of euphoria, hyperventilation, increased heart rate, dilated pupils, and secretions of odours that can seduce an unsuspecting love object. The eye of the chemical storm is in the brain.

The brain in RL resembles a huge geological and meteorological event: earthquakes, cyclones, tsunamis. It's as if the ecosystem of the lover's brain, the pulsing grey-blue-green planet in the skull, suffers a drastic depletion of the protective cortical ozone layer, triggering neuronal global warming with consequent atmospheric storms.

The notion that reason goes to pot in RL fits with a popular mind-brain theory first proposed in the 1970s. The outer brain, or cortex, which evolved late in evolution, is associated with rational thought and intelligence. The midbrain, known as the limbic system, regulates the emotions. But there's a deep inner core, located at the final bulb where the spinal cord enters the brain, dubbed by the physiologist Paul MacLean "the reptilian brain", where lurk our darker, primeval, instinctive behaviours of territoriality, mating and reward-seeking.

When two separate researchers, the British brain mapper Semir Zeki and the American anthropologist-psychologist Helen Fisher, used functional magnetic resonance imaging to explore the neural basis of RL, the brains of their lovelorn volunteers lit up precisely in that deep region known as the caudate nucleus: the site of the reptilian brain, thought to be 65m years old in evolutionary terms. The more passionate the subjects, the more active the caudate nucleus. The reptilian brain connects directly with the limbic system, where, according to Helen Fisher, "the chemical storms, leading to infatuation, almost certainly have their physical origin". In RL the music of cortical sweet reason is drowned out by the primitive drumbeats of our limbic and reptilian brains, stimulating cascades of PEA in the central nervous system. At the same time, adrenaline levels are boosted, prompting the release of a chemical called dopamine. Dopamine is associated with highly targeted attention, stamina, energy, all focused on reward.

As these powerful chemicals run riot down the neuronal pathways, they dilute and cancel out the nerve chemical called serotonin. Serotonin controls impulses, unruly passions, obsessive behaviour: it aids the sense of power over action, the feeling of "being in control". A severe depletion of serotonin can induce panic, anxiety, queasiness, manic behaviour, depression, obsession: "I can't get her/him out of my mindÉ I'm thinking about her/him all the time."

Patients with compulsive disorders — such as nonstop hand-washing and bulimia — are often prescribed Prozac (fluoxetine hydrochloride), which increases the activation of lowered serotonin in the synapses. In the language of pharmacology, Prozac is an SSRI, a selective serotonin-reuptake inhibitor. SSRIs prevent serotonin being swallowed up too quickly in the synapses. There are serious suggestions that the lovesick should be given a good dose of an SSRI.

So what, chemically speaking, is happening to the lovesick — the jilted, the jealous? The lover needs the constant fix of encounters with the love object to satisfy and dampen the excitation of those cataracts of PEA; any thwarting ("I can't get no-o... satis-faction!") can only lead to further drenching of PEA, resulting in even more drastic loss of serotonin. This explains the highs and lows of the lovesick, the out-of-control symptoms of possessiveness, goose pimples, butterflies in the stomach, restlessness, inability to concentrate, sleeplessness: that generalised delicious agony called infatuation.

But should RL be reciprocated, there follows the second stage: sexual fulfilment, in which the hormone testosterone becomes rampant in men, and also in women, especially at ovulation and even beyond the menopause. When actual contact with the love object occurs — stroking, love play, kissing, leading eventually to coitus — a heady hormone identified as oxytocin explodes like a firework display in the brain, releasing showers of natural opiates known as endorphins, a kind of natural crack: a mega-reward! At orgasm a man's oxytocin levels can increase by a factor of five. In women the oxytocin levels can be even higher during intercourse. Oxytocin, moreover, combines with the hormone vasopressin, which is associated with vivid emotional memories, visual, tactile, aural and nasal, consolidating the image and associated deep feelings for the love object. That piece of music, that particular scent, the purr of their voice, the shape of that nose exciting so much passion. The oxytocin highs, with their consequent endorphin hits, do much to explain the withdrawal symptoms when the love object goes cold and, worst of all, is seen in the arms of another. Small wonder psychiatrists have likened disappointed love to acute depression.

But what of lust, pure and simple? Lust can flourish independently of RL. Obviously, it can exist simultaneously with RL. In some lovers, though — the capricious, the promiscuous, the congenitally uncommitted — satisfaction of lust can kill accompanying RL stone dead. Most research shows, moreover, that simple lust seldom progresses to RL. As Helen Fisher puts it, "The brain circuitry of lust does not necessarily ignite the furnace of romance." On the other hand, RL can progress, especially after the birth of children, to the third stage: attachment — crucial for a stable marriage. Deeper attachment, in which long-term, mature love prospers, typically follows the birth of a child. Yet there are many examples of lifelong attachment between couples without children, just as many couples with children fail to achieve lasting attachment.

But all the chemical and neuronal rioting of RL raises another chicken question: does falling in love cause the chemical upheaval, or vice versa? Chicken or egg? There's an explanation originally propounded by the German ethologist (specialist in comparative animal behaviour studies) Konrad Lorenz. Lorenz, who worked for the Nazis, but survived the war to earn a Nobel prize, observed in ducks a phenomenon known as imprinting. There is a critical moment for a nestling bird, when its brain and central nervous system are geared to be bonded to its mother.

In the absence of the mother, the bird will bond with whatever animal it first encounters. The imprinting mechanism is crucial for survival, since it is supposed to attach to its protective parent like an invisible wire of inseparability.

The psychologist John Bowlby adapted Lorenz's imprinting concept into an intriguing idea known as "attachment theory". Bowlby was interested in the deleterious effects of maternal deprivation, and this led to his conviction that bonding with a parent or parent figure emerged through evolutionary pressures. Obviously, the child that failed to bond with the mother stood less chance of survival. Noting the similarity between a deprived child and a disappointed lover, for example, psychologists have identified this reconfigured imprinting in adult love: RL. Like the bonded child, the lover will stare into the love object's eyes and make coochicoo noises. If jilted, the lover, like the abandoned child, weeps, falls into depression, and can self-harm.

If the sexual bonding is successful, long-term attachment is in prospect. It occurs, if it does, after the RL high has run its course and the union has led to children. This new stage is fortuitous, since typically after 18 months to three years the PEA, dopamine and oxytocin cascades dwindle to a trickle (a result, neuroscientists say, of a kind of neutrotransmitter burnout).

Which brings us to the question: what do men and women really want from a love partner? Human statistics with a dash of animal behavioural psychology come to the explanatory rescue. More than a decade ago the American psychologist David Buss canvassed over 10,000 people in 37 cultures of the world, to conclude that women are programmed to seek out men who are breadwinners, whereas men are wired to detect breeding potential signalled by big hips, youth, healthy skin, bright eyes and lustrous hair.

And yet, despite the powerful determining forces of evolution, RL can re-emerge in a variety of combinations. While still warmly attached, in the bosom of the family, it's common to be attracted to another available love object. Helen Fisher again: "It seems to be the destiny of humankind that we are neurologically able to love more than one person at a time. You can feel profound attachment for a long-term spouse, while you feel romantic passion for someone in the office or your social circle, while you feel the sex drive as you read a book, watch a movie, or do something else unrelated to either partner."

Human mates who stay together are rewarded in evolutionary terms by the knowledge that their genes are being perpetuated. But adultery lurks constantly in the wings. Men make a huge investment in their offspring, and it would be unthinkable to see a rival's genes prosper. In this sense, jealousy is an evolutionary strategy to prevent cuckoldry. "Sexual jealousy," writes David Buss, "is activated when one is confronted either with signs that someone else has an interest in one's mate or with signs of defection by one's mate, such as flirting with someone else."

Despite strong motives and ideals for single attachment, human promiscuity is pervasive, especially among males (British heterosexual males admit to an average of six sexual partners in a lifetime, as opposed to an average of four admitted by women). Primate males, however, never refuse a chance to seduce an available female, and female primates are ready and willing should a forceful, attractive male appear despite fear of a walloping from her current mate. The ethologist Geoffrey Miller, in The Mating Mind: How Sexual Choice Shaped the Evolution of Human Nature, has an interesting take on defences against sexual infidelity. While granting that RL "evolved through sexual selection, not least because it signalled fidelity", and that RL lasts no longer than a matter of months, Miller believes that monogamy is actually encouraged by flirtation: "The human capacity for flirtation (sexually inhibited pseudo-courtship) is one of the modern world's most underrated virtues, the principal spice of adult social life throughout history." He believes sexual fantasy is of equal importance. "It permits sexual infidelity in the virtual reality of the imagination," he asserts, "without offending one's real sexual partner as much as a real affair would."

But here's a paradox. Prospects for sexual success, with the promise of preserving one's gene pool, favour sexual fidelity. Yet there are clearly reproductive benefits in promiscuity, especially for males. Obviously, flirtation is dangerous, since it can lead to mating. According to Miller, then, the clash of drives towards both monogamy and polygamy in the human animal creates a queasy tightrope walk. "We are not always sexually faithful," he argues, "but that does not mean that our capacity for fidelity is a flawed adaptation. It may be perfectly adapted to a Pleistocene world in which the highest reproductive success went to those who were almost always faithful, except when a significantly more attractive option arose."

Comparisons to primates, and even distant ancestors, have their limitations. In recent years it has been discovered that the most neglected aspect of sexual attraction in women is their desire for steadfast kindness in a mate. But is that kindness genetically determined, or does it arise from our unique human freedoms? In his book The Selfish Gene, Richard Dawkins argues that humans have language and imagination, endowing us with freedom to turn our genetic determination on its head. The last sentence of his book asserts: "We, alone on earth, can rebel against the tyranny of the selfish replicators." But a recent book by Frans de Waal, Our Inner Ape, challenges that contention. De Waal, a leading primatologist, has worked with chimpanzees, which are famously aggressive and selfish, and bonobos, which are given to altruism and empathy.

Both primates possess DNA nearly identical to humans, and de Waal argues that Homo sapiens therefore inherits genetically the violent, competitive traits as well as the kind and gentle ones. Bonobos greet colonies outside their own and they spend their time grooming, playing games and having sex. De Waal is convinced that when we come to understand the evolutionary pressures that shaped bonobo society, we shall begin to understand how they escaped the tendency to selfishness, hostility and violence. He is unhappy with the Dawkins scenario that describes our genetic inheritance as one of self-centred aggression, masked only by a fragile, non-altruistic and utilitarian co-operation based on self-interest. De Waal believes there is kindness in our genes, that it is in our nature to be both gentle as well as violent.

But in reminding us that there are areas of human behaviour that genetic determinism does not reach, Dawkins is acknowledging the limits of scientific explanation. Unlike the objective and scientifically measurable symptoms of being in love — your pulse, blood pressure, the state of your digestion — falling in love is an intensely subjective, conscious experience. And the phenomenon of individual consciousness is famously intractable to scientific investigation.

When we talk of "conscious" experience, we are saying that there is something that it is like — to smell a rose, feel lonely, get the point of a joke e-mail. To complete the idea, there's a parable doing the rounds of philosophy seminars. It tells of a neurophysiologist called Mary, who is the world's leading expert on colour vision. Mary can tell you what happens when you see a red pillar box: how the photons of light bounce off the pillar box and impinge on your optic nerves, sending signals to the cortical areas that give rise to the coloured image. Yet Mary doesn't have the faintest idea about the "something that it is like" to experience a red as opposed to blue pillar box — because she is colour-blind! In our attempts to understand consciousness, say the philosophers, no amount of scientific explanation is a substitute for personal, subjective experience. They call it the "hard problem" of consciousness.

With love it's undoubtedly the same. Science has myriad fascinating explanations for what happens, objectively, when people fall in love; but the explanations are not sufficient to encapsulate that "something that it is like" to be in love. Through the 20th century, however, western culture was mightily influenced by a group of psychologists who claim to have established a science of human relationships, stressing the importance of the unconscious as well as the conscious subject. Bypassing genetics, hormones, ethology and brain scans, Sigmund Freud's followers find explanations for RL in the dynamic of mother, father and child. Freud believed that love in adulthood is shaped by experiences in infancy; that adult RL is a subconscious attempt to mend the severed bond of child from parents.

The restoration of bonding, said Freud, involves a repeat of the childhood passions of jealousy, rivalry and rage, but there are exquisite pleasures in the restoration and expansion of those infant pleasures of oral satisfaction at the breast. RL involves acts of narcissism and self-love as you project your ego onto the significant other, leading, at the height of the love experience, to a sense of oceanic unity. At the same time, RL creates dependency, which can lead to vulnerability. Freud insisted, however, that in the long term the mother cannot be substituted for the adult love object, nor can the lover expect to discover the lost unconditional love of the mother for her infant.

But psychology does not stand still. By the mid-20th century, branches of psychology, pre-eminently among the "behaviourists", were stressing the primacy of culture and the environment over genetics, evolution or Freud's complexes — nurture over nature, in other words. They argued that RL is induced by influences of upbringing, local culture, society and history; hence there is nothing inevitable about falling in love. RL, they said, is an artificial social construct: acquired in the past through poetry, folk songs and religion; and in our own day through pop songs, movies, pulp fiction and soaps. Much as we pay lip service, they insist, to the notion of everlasting love till the seas run dry, our love convictions are prompted by our scriptwriting.

The implication that our scripts can be rewritten, and rewritten again, is the sobering conclusion of the eminent British sociologist Anthony Giddens. In his essay Intimacy, Giddens argues that contemporary western love practices are marked by selfishness and lack of commitment. The post-modern lover, he asserts, is a "flaneur" who stays in a partnership, including a marriage that has produced children, for as long as he obtains the rewards he seeks. He says the traditional love "narrative" has been transformed by changing social attitudes towards gender, sexual orientation, contraception and new types of sexual partnership. Sex, he points out, has become a leisure activity, detached from the complexities of marriage and childbearing.

In her book Falling in Love: A History of Torment and Enchantment, Sheila Sullivan maintains that contemporary marriage, in the current social context of greater equality in gender relationships, has serious consequences for women, who "now have a whole new script to learn, which tells them that sex, love, career, children, home can be managed all at once".

But whether the nature of RL is revealed by nurture rather than nature, by evolution rather than hormones, psychodynamics rather than behaviourism, there are significant lessons to be learnt from the science of statistics. Divorces, steadily on the increase these past five decades, now run at a rate of more than 50% in the highly concentrated residential districts of the southeast of England. The figures do not include the failed heterosexual partnerships that never reached marriage, nor homosexual partnerships, but the statistics reinforce the message that we should be sceptical about RL as a prelude to lasting love. And yet, statistics also reveal that, despite the scepticism, marriages are on the increase, at a rate of about 2% per annum. The notion that romantic love is worth it, that it can transform to permanent attachment, is not only far from dead, it is evidently alive and well and thriving.

At a conference on love held about 30 years ago in the US, the delegates agreed that romantic love should be defined as "a cognitive-affective state characterized by intrusive and obsessive fantasizing concerning reciprocity of amorant feelings by the object of the amorance". That, of course, is the problem of seeking to understand RL in clunking scientific language. Science tells us much that is interesting about love. But to describe what it is really like to fall in love, subjectively, personally, and to understand why we continue to embark on its exciting, as well as painful and hazardous, journey, we must turn to other kinds of human discourse: poetry, fiction, memoir, and real-life experience.

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