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--  作者:admin
--  发布时间:2010/2/17 18:59:06
--  The science of love

爱情的科学(The science of love)
I get a kick out of you / 我觉得你真带劲儿

Scientists are finding that, after all, love really is down to a chemical addiction between people


OVER the course of history it has been artists, poets and playwrights who have made the greatest progress in humanity\'s understanding of love. Romance has seemed as inexplicable as the beauty of a rainbow. But these days scientists are challenging that notion, and they have rather a lot to say about how and why people love each other.


Is this useful? The scientists think so. For a start, understanding the neurochemical pathways that regulate social attachments may help to deal with defects in people\'s ability to form relationships. All relationships, whether they are those of parents with their children, spouses with their partners, or workers with their colleagues, rely on an ability to create and maintain social ties. Defects can be disabling, and become apparent as disorders such as autism and schizophrenia—and, indeed, as the serious depression that can result from rejection in love. Research is also shedding light on some of the more extreme forms of sexual behaviour. And, controversially, some utopian fringe groups see such work as the doorway to a future where love is guaranteed because it will be provided chemically, or even genetically engineered from conception.

这真的有用吗?科学家们确实如是考虑。首先,让我们先来了解一下可调节社会附属关系的神经化学路径, 这有助于我们解决某些缺乏建立人际能力人群的问题。对于所有关系而言——无论是父母与子女间的亲情关系、夫妻间的婚姻关系,还是同事间的伙伴关系,全都依赖于一种建立并保持社会性纽带的能力。这种能力的缺损可使个人丧失行为能力并导致明显的心理紊乱,如自闭症和精神分裂症,正如将恋爱拒之门外可导致严重的沮丧一样。研究者们同样把目光投向了若干形式更为极端的性行为。有争议的是, 一些理想化且处于前沿领域的团体视该项工作为通向未来的一道大门。那时爱情将不会有任何风险,因为源于这个概念的化学或基因工程便可能将其变为现实。

The scientific tale of love begins innocently enough, with voles. The prairie vole is a sociable creature, one of the only 3% of mammal species that appear to form monogamous relationships. Mating between prairie voles is a tremendous 24-hour effort. After this, they bond for life. They prefer to spend time with each other, groom each other for hours on end and nest together. They avoid meeting other potential mates. The male becomes an aggressive guard of the female. And when their pups are born, they become affectionate and attentive parents. However, another vole, a close relative called the montane vole, has no interest in partnership beyond one-night-stand sex. What is intriguing is that these vast differences in behaviour are the result of a mere handful of genes. The two vole species are more than 99% alike, genetically.


Why do voles fall in love? / 为什么田鼠会坠入爱河?

The details of what is going on—the vole story, as it were—is a fascinating one. When prairie voles have sex, two hormones called oxytocin and vasopressin are released. If the release of these hormones is blocked, prairie-voles\' sex becomes a fleeting affair, like that normally enjoyed by their rakish montane cousins. Conversely, if prairie voles are given an injection of the hormones, but prevented from having sex, they will still form a preference for their chosen partner. In other words, researchers can make prairie voles fall in love—or whatever the vole equivalent of this is—with an injection.

像往常一样,最让人着魔的是田鼠爱情故事的进展细节。当草原田鼠性交时,其体内会释放两种称作催产素和抗利尿激素的荷尔蒙。如果这些荷尔蒙的释放被阻断,草原田鼠的性生活便成了短暂的艳遇,它们就会像生性放荡的山区堂兄那样去尽享受风流韵事。 相反,如果给草原田鼠注射以上荷尔蒙,虽然阻止它们性交,它们依然会钟情于已选择的伴侣。换句话说, 不过就一剂注射,研究者们便能让草原田鼠落入情网,不管草原田鼠的感觉如何,反正它们会产生与爱相类似的神经反应。

A clue to what is happening—and how these results might bear on the human condition—was found when this magic juice was given to the montane vole: it made no difference. It turns out that the faithful prairie vole has receptors for oxytocin and vasopressin in brain regions associated with reward and reinforcement, whereas the montane vole does not. The question is, do humans (another species in the 3% of allegedly monogamous mammals) have brains similar to prairie voles?

研究者找到一条与正在发生情形相关的线索,这一线索与如何使上述结果作用于人类有关。线索的结论是:当把这一魔术般的汁液注入山区田鼠体内,其反应与草原田鼠如出一辙。这就证实了,在忠诚的草原田鼠大脑内,与奖赏与强化相关联的区域中,具有一种催产素和抗利尿激素的荷尔蒙受体, 然而山区田鼠却没有。 问题是: 人类——据称是3%实行一夫一妻制的哺乳动物中的另一物种,是否也具有和草原田鼠相似的大脑结构?

To answer that question you need to dig a little deeper. As Larry Young, a researcher into social attachment at Emory University, in Atlanta, Georgia, explains, the brain has a reward system designed to make voles (and people and other animals) do what they ought to. Without it, they might forget to eat, drink and have sex—with disastrous results. That animals continue to do these things is because they make them feel good. And they feel good because of the release of a chemical called dopamine into the brain. Sure enough, when a female prairie vole mates, there is a 50% increase in the level of dopamine in the reward centre of her brain.

为对上述疑惑刨根问底,就需要“挖”得更深一些。一位来自佐治亚州,亚特兰大Emory大学,研究社会附属关系的学者Larry Yong,他对此的解释是,田鼠(以及人类和其他动物)的大脑内具有一套奖赏系统用以鼓励它(他)们去做生物应该完成的行为。如若不然,动物将忘记进食,饮水和性行为,从而招致灾难性的后果。动物们不断重复这些行为是因为那使它们感到快乐。这种快感是一种称作多巴胺的化学物质在大脑中的释放使然。当雌性草原田鼠交配时,在大脑奖赏系统中枢,多巴胺水平会有50%的上升,而这已完全足够让这些“女士”们产生上面提到的那种快感。

Similarly, when a male rat has sex it feels good to him because of the dopamine. He learns that sex is enjoyable, and seeks out more of it based on how it happened the first time. But, in contrast to the prairie vole, at no time do rats learn to associate sex with a particular female. Rats are not monogamous.


This is where the vasopressin and oxytocin come in. They are involved in parts of the brain that help to pick out the salient features used to identify individuals. If the gene for oxytocin is knocked out of a mouse before birth, that mouse will become a social amnesiac and have no memory of the other mice it meets. The same is true if the vasopressin gene is knocked out.

抗利尿激素和催产素就是从这里进入这个科学传说的。它们参与了大脑一些部分的工作,以帮助选出用于辨别个体的显著特征。 如果在老鼠出生前,DNA中的抗利尿激素基因即被剔除, 那只老鼠将会成为一个社会性失忆个体,它也不会对遇到的其他老鼠留下任何印象。如果催产素基因缺损,以上命题同样成立。

The salient feature in this case is odour. Rats, mice and voles recognise each other by smell. Christie Fowler and her colleagues at Florida State University have found that exposure to the opposite sex generates new nerve cells in the brains of prairie voles—in particular in areas important to olfactory memory. Could it be that prairie voles form an olfactory “image” of their partners—the rodent equivalent of remembering a personality—and this becomes linked with pleasure?

这里的显著特征是气味。耗子、老鼠和野鼠靠嗅觉区分彼此。Christie Fowler和她的同事在佛罗里达州大学的研究中发现,把草原田鼠暴露给异性可使其大脑产生新的神经细胞——在对嗅觉记忆至关重要的一些区域尤其如此。人类是靠个性特征来记住某一个人的。那么草原田鼠会构造一个嗅觉“形像”去记住伴侣吗?这与性愉悦是否存在关联呢?

Dr Young and his colleagues suggest this idea in an article published last month in the Journal of Comparative Neurology. They argue that prairie voles become addicted to each other through a process of sexual imprinting mediated by odour. Furthermore, they suggest that the reward mechanism involved in this addiction has probably evolved in a similar way in other monogamous animals, humans included, to regulate pair-bonding in them as well.


You might as well face it ... / 你或许也会面对它……

Sex stimulates the release of vasopressin and oxytocin in people, as well as voles, though the role of these hormones in the human brain is not yet well understood. But while it is unlikely that people have a mental, smell-based map of their partners in the way that voles do, there are strong hints that the hormone pair have something to reveal about the nature of human love: among those of Man\'s fellow primates that have been studied, monogamous marmosets have higher levels of vasopressin bound in the reward centres of their brains than do non-monogamous rhesus macaques.


Other approaches are also shedding light on the question. In 2000, Andreas Bartels and Semir Zeki of University College, London, located the areas of the brain activated by romantic love. They took students who said they were madly in love, put them into a brain scanner, and looked at their patterns of brain activity.

其他方法也正在为人们寻找这些问题的谜底。2000 年,来自伦敦市大学学院的Andreas Bartels和Semir Zeki定位出了能被浪漫爱情激活的大脑区域。两位学者选择自称正在热恋的学生作为测试目标,利用脑扫描仪对他们的大脑活动模式进行观测。

The results were surprising. For a start, a relatively small area of the human brain is active in love, compared with that involved in, say, ordinary friendship. “It is fascinating to reflect”, the pair conclude, “that the face that launched a thousand ships should have done so through such a limited expanse of cortex.” The second surprise was that the brain areas active in love are different from the areas activated in other emotional states, such as fear and anger. Parts of the brain that are love-bitten include the one responsible for gut feelings, and the ones which generate the euphoria induced by drugs such as cocaine. So the brains of people deeply in love do not look like those of people experiencing strong emotions, but instead like those of people snorting coke. Love, in other words, uses the neural mechanisms that are activated during the process of addiction. “We are literally addicted to love,” Dr Young observes. Like the prairie voles.

令人惊讶的是:首先,人脑参与到恋爱的活动区域,较之其他感情(如普通友谊),相对要比较小些。“引人注意的是,结果显示,”两位学者推断说,“美丽的面容是通过控制一个有限区域的大脑皮层来实现‘一顾倾人城,再顾倾人国’的。”  第二个惊奇之处是,大脑内因恋爱而活跃的区域不同于因其他情绪而活跃的区域,例如,恐惧和愤怒。 被恋爱“咬住”的那部份大脑还包括负责内脏感觉和因可卡因等毒品生成快感的区域。因此,因此,深坠爱河的恋人们的大脑,并非类同于经历强烈情绪波动的人,倒更接近那些鼻吸可卡因的瘾君子。换句话说,爱情使用的是在成瘾过程中被激活的神经机制。“严格地讲, 我们成瘾于爱情,”Young博士评述道,“就如同草原田鼠”。

It seems possible, then, that animals which form strong social bonds do so because of the location of their receptors for vasopressin and oxytocin. Evolution acts on the distribution of these receptors to generate social or non-social versions of a vole. The more receptors located in regions associated with reward, the more rewarding social interactions become. Social groups, and society itself, rely ultimately on these receptors. But for evolution to be able to act, there must be individual variation between mice, and between men. And this has interesting implications.

那么看起来,能形成稳固社会联结的动物之所以愿意建立彼此间的伙伴关系,可能是由它们的抗利尿激素和催产素受体在大脑中的位置所决定。生物进化作用于以上受体在大脑的分布,而产生了社会性或非社会性不同版本的田鼠。位于奖赏机制有关区域的受体越多,对个体而言, 社会互动就更具有回报性。动物的社会性团体,乃至整个社会本身都最终依赖于这些受体。但要使进化真能发生效力,在鼠之鼠之间以及人与人之间,一定存在个体变异。这一论述还有引人入胜的推论。

Last year, Steven Phelps, who works at Emory with Dr Young, found great diversity in the distribution of vasopressin receptors between individual prairie voles. He suggests that this variation contributes to individual differences in social behaviour—in other words, some voles will be more faithful than others. Meanwhile, Dr Young says that he and his colleagues have found a lot of variation in the vasopressin-receptor gene in humans. “We may be able to do things like look at their gene sequence, look at their promoter sequence, to genotype people and correlate that with their fidelity,” he muses.

在Emory大学与Young博士一同工作的Steven Phelps去年发现,草原田鼠各个体间抗利尿激素受体的脑内分布,存在着很大的差异。他提出,正是这一变异导致了社会行为的个体差异,换句话说,一些田鼠将会比另一些更加忠诚。同时,Young博士说他和同事已经发现人类抗利尿激素受体基因的许多变异。“我们或许能够做些类似于察看人们的基因序列,察看他们的启动序列等工作,在此基础上对人们进行基因型分类, 并把分类结果与他们的忠诚度关联起来”,Young博士作如是想。

It has already proved possible to tinker with this genetic inheritance, with startling results. Scientists can increase the expression of the relevant receptors in prairie voles, and thus strengthen the animals\' ability to attach to partners. And in 1999, Dr Young led a team that took the prairie-vole receptor gene and inserted it into an ordinary (and therefore promiscuous) mouse. The transgenic mouse thus created was much more sociable to its mate.

事实已经证明可能对这种基因遗传进行修补,并产生了令人吃惊的结果。科学家能增加草原田鼠相关受体的表达,以加强动物对同伴的依附能力。而且在 1999 年,Young博士带领了一只研究队伍,他们将草原田鼠的受体基因插入到一只平常(因此成为杂乱的) 老鼠的体内,由此产生的转基因鼠对它的配偶表现得更为友善。

Love, love me do / 爱我,真心地爱我

Scanning the brains of people in love is also helping to refine science\'s grasp of love\'s various forms. Helen Fisher, a researcher at Rutgers University, and the author of a new book on love*, suggests it comes in three flavours: lust, romantic love and long-term attachment. There is some overlap but, in essence, these are separate phenomena, with their own emotional and motivational systems, and accompanying chemicals. These systems have evolved to enable, respectively, mating, pair-bonding and parenting.

对恋爱中人们大脑的扫描,也有助于使科学对各种形式爱情的领会变得更为精确。Rutgers 大学的一位研究人员Helen Fisher,同时是一本关于爱情的新书作者,她提出,爱会以三种滋味出现:欲望,浪漫的恋爱和长期的附属关系。三种滋味的爱情虽有一些重叠,但本质上是截然不同的现象,并且具有各自的情绪和激发系统,以及相伴的体内化学物质。这些系统通过进化后以分别让交配,伴侣联接和养育子女成为可能。

Lust, of course, involves a craving for sex. Jim Pfaus, a psychologist at Concordia University, in Montreal, says the aftermath of lustful sex is similar to the state induced by taking opiates. A heady mix of chemical changes occurs, including increases in the levels of serotonin, oxytocin, vasopressin and endogenous opioids (the body\'s natural equivalent of heroin). “This may serve many functions, to relax the body, induce pleasure and satiety, and perhaps induce bonding to the very features that one has just experienced all this with”, says Dr Pfaus.

首先当然是欲望,包括对性的强烈渴求。蒙特利尔Concordia大学的一位心理学家,Jim Pfaus说道,贪欲的性行为其结果和使用鸦片引起的状况颇相类似:一种令人兴奋的混合化学变化,包括血液复合胺(5羟色氨),催产素,抗利尿激素和内非肽(身体内的海洛英的天然同等物) 的水平升高。“这可能提供许多功能,如放松身体,产生快乐和满足感, 也可能导致把某些特征与刚才的全部经历联结起来,”Pfaus博士补充道。

Then there is attraction, or the state of being in love (what is sometimes known as romantic or obsessive love). This is a refinement of mere lust that allows people to home in on a particular mate. This state is characterised by feelings of exhilaration, and intrusive, obsessive thoughts about the object of one\'s affection. Some researchers suggest this mental state might share neurochemical characteristics with the manic phase of manic depression. Dr Fisher\'s work, however, suggests that the actual behavioural patterns of those in love—such as attempting to evoke reciprocal responses in one\'s loved one—resemble obsessive compulsive disorder (OCD).

接下来便是两性吸引,双方处于相爱的状态 (就是我们所知的浪漫的、或强迫性的恋爱)。这是纯粹的欲望的升华,它使人们总能回到某个特定配偶身边。这种状态的特征,是兴奋感和对情感对象打扰式的和强迫性的思恋。一些研究员提到,这一心理状态可能和狂躁状态的躁郁症有相同的神经化学特征。Fisher博士的工作揭示了恋爱人群真实的行为模式,比如:试图唤起被爱者的报答——类似于强迫性混乱症(OCD)。


That raises the question of whether it is possible to “treat” this romantic state clinically, as can be done with OCD. The parents of any love-besotted teenager might want to know the answer to that. Dr Fisher suggests it might, indeed, be possible to inhibit feelings of romantic love, but only at its early stages. OCD is characterised by low levels of a chemical called serotonin. Drugs such as Prozac work by keeping serotonin hanging around in the brain for longer than normal, so they might stave off romantic feelings. (This also means that people taking anti-depressants may be jeopardising their ability to fall in love.) But once romantic love begins in earnest, it is one of the strongest drives on Earth. Dr Fisher says it seems to be more powerful than hunger. A little serotonin would be unlikely to stifle it.


Wonderful though it is, romantic love is unstable—not a good basis for child-rearing. But the final stage of love, long-term attachment, allows parents to co-operate in raising children. This state, says Dr Fisher, is characterised by feelings of calm, security, social comfort and emotional union.


Because they are independent, these three systems can work simultaneously—with dangerous results. As Dr Fisher explains, “you can feel deep attachment for a long-term spouse, while you feel romantic love for someone else, while you feel the sex drive in situations unrelated to either partner.” This independence means it is possible to love more than one person at a time, a situation that leads to jealousy, adultery and divorce—though also to the possibilities of promiscuity and polygamy, with the likelihood of extra children, and thus a bigger stake in the genetic future, that those behaviours bring. As Dr Fisher observes, “We were not built to be happy but to reproduce.”


The stages of love vary somewhat between the sexes. Lust, for example, is aroused more easily in men by visual stimuli than is the case for women. This is probably why visual pornography is more popular with men. And although both men and women express romantic love with the same intensity, and are attracted to partners who are dependable, kind, healthy, smart and educated, there are some notable differences in their choices. Men are more attracted to youth and beauty, while women are more attracted to money, education and position. When an older, ugly man is seen walking down the road arm-in-arm with a young and beautiful woman, most people assume the man is rich or powerful.


These foolish things / 这些愚蠢的玩意儿

Of course, love is about more than just genes. Cultural and social factors, and learning, play big roles. Who and how a person has loved in the past are important determinants of his (or her) capacity to fall in love at any given moment in the future. This is because animals—people included—learn from their sexual and social experiences. Arousal comes naturally. But long-term success in mating requires a change from being naive about this state to knowing the precise factors that lead from arousal to the rewards of sex, love and attachment. For some humans, this may involve flowers, chocolate and sweet words. But these things are learnt.


If humans become conditioned by their experiences, this may be the reason why some people tend to date the same “type” of partner over and over again. Researchers think humans develop a “love map” as they grow up—a blueprint that contains the many things that they have learnt are attractive. This inner scorecard is something that people use to rate the suitability of mates. Yet the idea that humans are actually born with a particular type of “soul mate” wired into their desires is wrong. Research on the choices of partner made by identical twins suggests that the development of love maps takes time, and has a strong random component.


Work on rats is leading researchers such as Dr Pfaus to wonder whether the template of features found attractive by an individual is formed during a critical period of sexual-behaviour development. He says that even in animals that are not supposed to pair-bond, such as rats, these features may get fixed with the experience of sexual reward. Rats can be conditioned to prefer particular types of partner—for example by pairing sexual reward with some kind of cue, such as lemon-scented members of the opposite sex. This work may help the understanding of unusual sexual preferences. Human fetishes, for example, develop early, and are almost impossible to change. The fetishist connects objects such as feet, shoes, stuffed toys and even balloons, that have a visual association with childhood sexual experiences, to sexual gratification.


So love, in all its glory, is just, it seems, a chemical state with genetic roots and environmental influences. But all this work leads to other questions. If scientists can make a more sociable mouse, might it be possible to create a more sociable human? And what about a more loving one? A few people even think that “paradise-engineering”, dedicated to abolishing the “biological substrates of human suffering”, is rather a good idea.


As time goes by / 时光流逝

Progress in predicting the outcome of relationships, and information about the genetic roots of fidelity, might also make proposing marriage more like a job application—with associated medical, genetic and psychological checks. If it were reliable enough, would insurers cover you for divorce? And as brain scanners become cheaper and more widely available, they might go from being research tools to something that anyone could use to find out how well they were loved. Will the future bring answers to questions such as: Does your partner really love you? Is your husband lusting after the au pair?

通过彼此关联的医学、遗传基因和心理学的检查,预测人际关系最终结果的研究进展和关于忠诚度的遗传基础信息,能使求婚变得更像工作申请。如果这个结论足够可信,保险公司会为你的婚姻投保吗?当脑扫描仪变得更便宜更普及,它能由研究工具变成任何人都可以用于发现他们被爱到何种程度的手段吗?未来会不会就如下问题为人类找到答案:你的伴侣是否真的爱你? 你的丈夫是否正对来家打工的留学女生暗送秋波?

And then there are drugs. Despite Dr Fisher\'s reservations, might they also help people to fall in love, or perhaps fix broken relationships? Probably not. Dr Pfaus says that drugs may enhance portions of the “love experience” but fall short of doing the whole job because of their specificity. And if a couple fall out of love, drugs are unlikely to help either. Dr Fisher does not believe that the brain could overlook distaste for someone—even if a couple in trouble could inject themselves with huge amounts of dopamine.

接下来当然会有相应的药物。尽管Fisher博士对此有所保留。我们还是想问:药物是否可能帮助人们坠入爱河,或者破镜重圆? 或许不能完全做到,但却可能部分地提高“恋爱体验”。对此另一位学者Pfaus博士如是说:药物达不到整体提高的效果,因为药毕竟是药,这就是它的特殊性。如果一对夫妇不再相爱,药物多半无能为力。Fisher博士不相信大脑可以忽略对某人的厌恶——即使对婚姻危机中的夫妇大量注射的多巴氨,也于事无补。

However, she does think that administering serotonin can help someone get over a bad love affair faster. She also suggests it is possible to trick the brain into feeling romantic love in a long-term relationship by doing novel things with your partner. Any arousing activity drives up the level of dopamine and can therefore trigger feelings of romance as a side effect. This is why holidays can rekindle passion. Romantics, of course, have always known that love is a special sort of chemistry. Scientists are now beginning to show how true this is.


【原载《经济学人》◎周亦丹 译】