您正在看的英语阅读是: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