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（重叠，重复） 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.
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（血清素）, oxytocin（催产素）, vasopressin（加压素） 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.
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
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（扼杀，窒息） 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.
相关单词：helping
helping解释：n.食物的一份&adj.帮助人的，辅助的
helping例句：
The poor children regularly pony up for a second helping of my hamburger. 那些可怜的孩子们总是要求我把我的汉堡包再给他们一份。
By doing this, they may at times be helping to restore competition. 这样一来, 他在某些时候,有助于竞争的加强。
相关单词：lust
lust解释：n.性(淫)欲；渴(欲)望；vi.对…有强烈的欲望
lust例句：
He was filled with lust for power.他内心充满了对权力的渴望。
Sensing the explorer's lust for gold, the chief wisely presented gold ornaments as gifts.酋长觉察出探险者们垂涎黄金的欲念，就聪明地把金饰品作为礼物赠送给他们。
相关单词：attachment
attachment解释：n.附属物，附件；依恋；依附
attachment例句：
She has a great attachment to her sister.她十分依恋她的姐姐。
She's on attachment to the Ministry of Defense.她现在隶属于国防部。
相关单词：overlap
overlap解释：v.重叠，与…交叠；n.重叠
overlap例句：
The overlap between the jacket and the trousers is not good.夹克和裤子重叠的部分不好看。
Tiles overlap each other.屋瓦相互叠盖。
相关单词：phenomena
phenomena解释：n.现象
phenomena例句：
Ade couldn't relate the phenomena with any theory he knew.艾德无法用他所知道的任何理论来解释这种现象。
The object of these experiments was to find the connection,if any,between the two phenomena.这些实验的目的就是探索这两种现象之间的联系，如果存在着任何联系的话。
相关单词：craving
craving解释：n.渴望,热望
craving例句：
a craving for chocolate 非常想吃巧克力
She skipped normal meals to satisfy her craving for chocolate and crisps. 她不吃正餐，以便满足自己吃巧克力和炸薯片的渴望。
相关单词：lustful
lustful解释：a.贪婪的；渴望的
lustful例句：
Adelmo agreed and duly submitted to Berengar's lustful advances. 阿德尔摩同意了并适时地顺从了贝仁格情欲的增长。
The lustful scenes of the movie were abhorrent to the old lady. 电影里淫荡的画面让这老妇人厌恶。
相关单词：satiety
satiety解释：n.饱和；(市场的)充分供应
satiety例句：
There is no satiety in study.学无止境。
Their presence in foods induces satiety at meal time.它们在食物中的存在诱导进餐时的满足感。
相关单词：obsessive
obsessive解释：adj. 着迷的, 强迫性的, 分神的
obsessive例句：
Some people are obsessive
He's becoming more and more obsessive
相关单词：refinement
refinement解释：n.文雅；高尚；精美；精制；精炼
refinement例句：
Sally is a woman of great refinement and beauty. 莎莉是个温文尔雅又很漂亮的女士。
Good manners and correct speech are marks of refinement.彬彬有礼和谈吐得体是文雅的标志。
相关单词：mere
mere解释：adj.纯粹的；仅仅，只不过
mere例句：
That is a mere repetition of what you said before.那不过是重复了你以前讲的话。
It's a mere waste of time waiting any longer.再等下去纯粹是浪费时间。
相关单词：intrusive
intrusive解释：adj.打搅的；侵扰的
intrusive例句：
The cameras were not an intrusive presence.那些摄像机的存在并不令人反感。
Staffs are courteous but never intrusive.员工谦恭有礼却从不让人感到唐突。
相关单词：evoke
evoke解释：vt.唤起，引起，使人想起
evoke例句：
These images are likely to evoke a strong response in the viewer.这些图像可能会在观众中产生强烈反响。
Her only resource was the sympathy she could evoke.她以凭借的唯一力量就是她能从人们心底里激起的同情。
相关单词：disorder
disorder解释：n.紊乱，混乱；骚动，骚乱；疾病，失调
disorder例句：
When returning back,he discovered the room to be in disorder.回家后，他发现屋子里乱七八糟。
It contained a vast number of letters in great disorder.里面七零八落地装着许多信件。
相关单词：inhibit
inhibit解释：vt.阻止，妨碍，抑制
inhibit例句：
Don't let ego and greed inhibit clear thinking and hard work.不要让自我和贪婪妨碍清晰的思维和刻苦的工作。
They passed a law to inhibit people from parking in the street.他们通过一项法令以阻止人们在街上停车。
相关单词：stifle
stifle解释：vt.使窒息；闷死；扼杀；抑止，阻止
stifle例句：
She tried hard to stifle her laughter.她强忍住笑。
It was an uninteresting conversation and I had to stifle a yawn.那是一次枯燥无味的交谈，我不得不强忍住自己的呵欠。
相关单词：spouse
spouse解释：n.配偶(指夫或妻)
spouse例句：
Her spouse will come to see her on Sunday.她的丈夫星期天要来看她。
What is the best way to keep your spouse happy in the marriage?在婚姻中保持配偶幸福的最好方法是什么？
相关单词：jealousy
jealousy解释：n.妒忌，嫉妒，猜忌
jealousy例句：
Some women have a disposition to jealousy.有些女人生性爱妒忌。
I can't support your jealousy any longer.我再也无法忍受你的嫉妒了。
相关单词：promiscuity
promiscuity解释：n.混杂，混乱；（男女的）乱交
promiscuity例句：
Promiscuity went unpunished, divorce was permitted. 乱交挨不着惩罚，离婚办得成手续。 来自英汉文学
There is also no doubt that she falls into promiscuity at last. 同时无疑她最后也堕入性乱。 来自互联网
相关单词：genetic
genetic解释：adj.遗传的，遗传学的
genetic例句：
It's very difficult to treat genetic diseases.遗传性疾病治疗起来很困难。
Each daughter cell can receive a full complement of the genetic information.每个子细胞可以收到遗传信息的一个完全补偿物。
相关单词：stimuli
stimuli解释：n.刺激（物）
stimuli例句：
It is necessary to curtail or alter normally coexisting stimuli.必需消除或改变正常时并存的刺激。
My sweat glands also respond to emotional stimuli.我的汗腺对情绪刺激也能产生反应。
相关单词：intensity
intensity解释：n.强烈，剧烈；强度；烈度
intensity例句：
I didn't realize the intensity of people's feelings on this issue.我没有意识到这一问题能引起群情激奋。
The strike is growing in intensity.罢工日益加剧。
