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.

對戀愛中人們大腦的掃描，也有助于使科學對各種形式愛情的領會變得更為精確。Rutgers 大學的一位研究人員Helen Fisher，同時是一本關于愛情的新書作者，她提出，愛會以三種滋味出現：欲望，浪漫的戀愛和長期的附屬關系。三種滋味的愛情雖有一些重疊，但本質上是截然不同的現象，并且具有各自的情緒和激發系統，以及相伴的體內化學物質。這些系統通過進化后以分別讓交配，伴侶聯接和養育子女成為可能。

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.

首先當然是欲望，包括對性的強烈渴求。蒙特利爾Concordia大學的一位心理學家，Jim Pfaus說道，貪欲的性行為其結果和使用鴉片引起的狀況頗相類似：一種令人興奮的混合化學變化，包括血液復合胺(5羥色氨)，催產素，抗利尿激素和內非肽(身體內的海洛英的天然同等物) 的水平升高。“這可能提供許多功能，如放松身體，產生快樂和滿足感, 也可能導致把某些特征與剛才的全部經歷聯結起來，”Pfaus博士補充道。

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).

接下來便是兩性吸引，雙方處于相愛的狀態 (就是我們所知的浪漫的、或強迫性的戀愛)。這是純粹的欲望的升華，它使人們總能回到某個特定配偶身邊。這種狀態的特征，是興奮感和對情感對象打擾式的和強迫性的思戀。一些研究員提到，這一心理狀態可能和狂躁狀態的躁郁癥有相同的神經化學特征。Fisher博士的工作揭示了戀愛人群真實的行為模式，比如：試圖喚起被愛者的報答——類似于強迫性混亂癥(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.

這又產生一個問題，即是否可能和處理OCD一樣，用病理學方式來“處治”這種浪漫狀態。任何沉醉于愛情的青少年，他們的父母可能都想知道相應的答案。Fisher博士提出，抑制浪漫愛情的可能性確實存在，但只能是在感情發展的最初階段。OCD的特征，是血液中一種叫血液復合胺(5羥色氨)的含量較低。如果Prozac等藥物讓血液中的復合氨在大腦中停留得比正常時間更久，這些藥品就可能阻止浪漫感覺的出現。(這也意味著服用抗抑郁藥物的人們可能正在危及他們彼此相愛能力。)真摯浪漫的愛情一旦開始，它就成為了地球上最強大的動力之一。Fisher博士說，這種欲望比食欲強大得多，一點兒血液中的復合氨不太可能扼殺心中如此強烈的情感。

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.

盡管浪漫的愛情如此奇妙，但它卻并不穩定——這絕非養兒育女的良好基礎。而愛情的最后階段，即長期的附屬關系，卻使父母在養育孩子方面得以精誠合作——這種狀態，Fisher博士認為，它的特征恰恰是平穩感、安全感、社會性的慰籍以及情感的最佳結合。

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.”

因為三個階段的系統彼此獨立，所以他們可能同時工作而導致危險的后果。如Fisher博士解釋的那樣，“你可能對長期配偶有深深的附屬感，同時你又因另一人而感受到浪漫的愛情，其間，你又由于第三位異性而產生性驅動力。”這種獨立性意味著你可能同時愛上多個異性而導致妒忌、私通和離婚——盡管也有可能是亂交、一夫多妻、和隨之而來的額外生育，即最終一個更大的預期基因賭注。正如Fisher博士所述，“我們不是為快樂卻是為了生殖而被創造的。”

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.

愛情的各階段在性別之間略有差別。例如，與女性相比，男性的欲望更容易被視覺刺激喚醒。這或許就是為什么視覺色情對男性而言更加流行。雖然男人和女人用同樣的強度表達浪漫的愛情，也同樣會被可靠、和藹、健康、聰明和有教養的伴侶所吸引，但不同性別在選擇配偶時還是有著一些顯著的不同。男性更易被年輕和美貌所吸引，而女性更多會青睞于金錢、教育和地位。當人們看到蒼老而丑陋的男人手挽著年輕美麗的女子漫步道旁，大多數都會設想此公不是腰纏萬貫，便有大權在握。