【译注】这是一篇[爪译]的翻译文章，原文来自《纽约时报》2011-3-6，点这里查看英文原文On the Left Hand, There Are No Easy Answers.以下为中英对照译文，悦读愉快:)</p>
人不是对称的。在生命的早期即胚胎发育阶段，心左转，肝右转。肺虽然看上去对称，但其左右叶却有迥异的结构。
Humans are asymmetric animals. Early in our embryonic development, the heart turns to the left. The liver develops on the right. The left and right lungs have distinct structure.
不对称的内脏若长在相反的一侧，就是一些罕见的综合征（如Kartagener综合征，译者注）——我还记得第一次当我检查一位右位心的孩子时是多么的不安，对的，长在右边的心脏，心跳在你意想不到的地方。相比而言，人类另一种基本的不对称却很常见，那就是左右利手，它反映了大脑结构和功能的不对称性，但这种不对称，却不是那么好理解。
There are certain rare syndromes in which the usual asymmetry of organs is reversed — I remember how disconcerting it was the first time I examined a child with dextrocardia, a heart on the right side, and heard the heart sounds in unexpected places. But when it comes to handedness, another basic human asymmetry, which reflects the structure and function of the brain, the reversed pattern is relatively common, and for all that, not easily understood.
左撇子的美国总统：杰拉尔德·福特，比尔·克林顿和奥巴马（图片来源：纽约时报）
几个世纪以来，左撇子被视为是“有罪的”和“与魔鬼的交易”，左撇子的孩子都要纠正过来。而现在这种羞辱已消失殆尽。除此之外，美国过去七年内的四位总统——福特，老布什，克林顿和奥巴马——都是左撇子（里根有时候也被称为是均利手）。
Over the centuries, left-handers have been accused of criminality and dealings with the devil, and children have been subjected to “re-education.” In recent years the stigma has largely vanished; among other things, four of our last seven presidents — Ford, the elder Bush, Clinton, Obama — have been left-handed. (Reagan is sometimes cited as ambidextrous.)
但左右利手之谜依然存在。约90%的人是右利手，10%是左利手，这个比例随时间流逝依旧恒定。
But the riddle of what underlies handedness remains. Its proportions — roughly 90 percent of people are right-handed and 10 percent left-handed — stay consistent over time.
“这仍是个谜”，遗传学家Clyde Francks说道， 2007年牛津大学的研究者发现了与左利手有关的基因变异，他是此研究的第一作者。
“This is really still mysterious,” said Clyde Francks, a geneticist and the lead author of a 2007 study in which Oxford University researchers identified a genetic variant linked to left-handedness.
惯用手（左手或右手）和大脑的不对称性有关，而这些目前还不甚明朗，Francks博士说；在了解脑的不对称性方面，实际上我们才刚刚开始。
Hand dominance (whether left or right) is related to brain asymmetry. And that, Dr. Francks said, “is not at all understood; we’re really at the very beginning of understanding what makes the brain asymmetrical.”
尽管我们的近亲——灵长类的大脑也存在着不对称性，但普遍认为人类的大脑在不对称性方面最为突出，而且对于大脑不对称性的理解能够告诉我们更多关于这些问题的答案：我们是谁，我们的大脑是如何工作的。
Though brain asymmetries exist in our closest primate relatives, there seems to be general consensus that the human brain is more profoundly asymmetric, and that understanding that asymmetry will show us much about who we are and how our brains work.
脑的不对称性，左右半球功能的分布，是理解语言、思维、记忆甚至创造力的关键。很多年来，左右利手被认为是理解左右脑内部平衡的一个外部线索。
Brain lateralization, the distribution of function into right and left hemispheres, is crucial for understanding language, thought memory and perhaps even creativity. For many years, handedness has been seen as a possible proxy, an external clue to the balance in the brain between left and right.
对于右利手来说，语言活动主要是在左脑。尽管很多左利手者的左脑也有语言优势，但相当多的人语言区域更均匀地分布在两个脑半球，或主要在右脑。
For right-handed people, language activity is predominantly on the left side. Many left-handers also have left-side language dominance, but a significant number have language either more evenly distributed in both hemispheres or else predominantly on the right side of the brain.
很明显，惯用手有遗传性。牛津研究组2007年的那篇文章找出了一个叫LRRTM1的基因，他们对有阅读障碍的儿童进行研究，并证明这与左撇子的发展相关。
Handedness clearly runs in families. The 2007 paper by the group at Oxford identified a gene, LRRTM1, that they discovered in the course of studying children with , and which turned out to be associated with the development of left-handedness.
荷兰Max Planck心理语言研究所的Francks博士回忆，当初这个研究曾作为头条新闻引起了广泛的关注，更是因为这个基因不合时宜地也在精神分裂症患者身上发现，尽管这其中的关系不是那么简单或者已被研究透彻。“我们不是在寻找一个惯用手或精神分裂症的基因”，他说，“我们在寻找微妙的关系”。基因反映了神经元互相联络的方式，但其中的机制仍需研究。
Dr. Francks, who is now at the Max Planck Institute for Psycholinguistics in the Netherlands, recalls that the discovery made headlines and attracted a great deal of attention, the more so because this gene was also found disproportionately in people with schizophrenia, even though none of these connections are simple or well understood. “We’re not looking for a gene for handedness or a gene for schizophrenia,” he said. “We’re looking for subtle relationships.” The gene affects the ways that neurons communicate with one another, he said, but its mechanisms still need to be studied.
Daniel Geschwind博士是UCLA医学院人类遗传学、神经病及精神病学的教授，他对语言与惯用手的关系很感兴趣，对惯用手的研究能帮助我们理解人脑的进化。“惯用手有遗传基础，但是同身高、体重等其他特征一样，它也是复杂的”，他说，“不是由单基因控制的，这也跟环境因素有关，是个非常复杂的问题”。
Dr. Daniel Geschwind, a professor of human genetics, neurology and psychiatry atUniversity of California, Los Angeles, School of Medicine, is interested in the connections between language and handedness, and the ways that handedness can help us understand the evolution of the human brain. “Handedness has a genetic basis, but like other complex traits — height, weight — it is complex,” he said. “It’s not a single gene that leads to it. There’s a strong environmental component, too. It’s a very tricky problem.”
当我们试图将其他特征划分为全或无时，惯用手最好看做是一个连续的谱系，两端是绝对的左撇子和右撇子，中间则有过渡，对习惯用哪只手有不同程度的偏爱。
As with other traits that we are tempted to classify as either/or, handedness is probably better viewed as a spectrum encompassing the very strongly right-handed or left-handed, and a range of those who prefer to use one hand or the other, but have different degrees of comfort and competency with the nondominant hand.
总之，Geschwind博士说，左撇子的大脑不对称性较少，两侧大脑半球的功能分布更加均衡。“也许左撇子更准确的叫法是非右利手”，他说道，“他们中很多人的右手都很灵活，能做精细的动作。”
In general, said Dr. Geschwind, left-handers have less asymmetric brains, with more even distribution over the two hemispheres. “Perhaps a more accurate conceptual way to think about them is as non-right-handers,” he said. “Many of them are much more likely to be ambidextrous and have fine motor abilities with their right hands.”
由于左撇子一直当做是了解大脑复杂的解剖结构的一把钥匙，研究人员在不断寻找、争辩左撇子与其他一些情况的关系，包括与免疫失调、学习和阅读障碍、预期寿命减少及精神分裂症。
Because left-handedness has been seen as a key to the complex anatomy of the brain, researchers continue to look for — and debate — links to many other conditions, including immune disorders, learning disabilities and dyslexia, reduced life expectancy and schizophrenia.
这其中的任何一项都是个难题。尤其是左撇子和精神分裂症之间拉扯不断的关系，但精神分裂症很复杂，而且可能因种族而异，研究表明不同种族的人得精神分裂症的种类也不同；去年的一项研究发现，非右利手患精神分裂症或神经认知障碍的风险并未增加。
None of it turns out to be simple. The idea of links to schizophrenia has been particularly persistent, but schizophrenia is a complicated and probably heterogeneous disorder, and studies of different populations show different patterns; last year, a study found no increased risk with non-right-handedness for schizophrenia or poorer neurocognition.
我们有时担心孩子过早地表现出左或右利手的倾向，尤其是在1岁以内。如果婴幼儿对使用一只手表现出特别强烈的偏好，可能提示另一侧的大脑有神经损伤。
In pediatrics, we sometimes worry about children who manifest handedness too early, before their first birthday. The concern is that if a very young child seems to strongly prefer one hand, there may actually be some problem — perhaps some kind of neurological damage — on the other side.
左撇子有时被视为病态。Cesare Lombroso是19世纪臭名昭著的医生，他鉴定出不同的面部（和种族）特征的犯罪倾向，还称左撇子为病态、原始、野蛮和犯罪。而我是听着这样的故事长大的一代人：在恶劣的（旧国家的）旧时代，愚蠢无知的人试图迫使左撇子的孩子用右手。听我爸爸说，在我叔叔还是孩子的时候，他的左手不得不反绑在身后。
Left-handedness has sometimes been treated as pathological. Cesare Lombroso, the infamous 19th-century physician who identified various facial (and racial) features with criminal traits, also saw left-handedness as evidence of pathology, primitivism, savagery and criminality. And I was brought up with the story that a generation ago, in the bad old days (and in the old country), foolish unenlightened people tried to force left-handed children to convert and use their right hands. My father said that my uncle, his older brother, had had his left hand tied behind his back as a child.
我一位同事的丈夫Anthony Gentile是位基金经理，今年41岁，在辛辛那提之外的地区长大。他告诉我说，虽然他是个左撇子，但被教育用右手写字——尽管他可以用右手写字母，可他从来不会正确地拿笔。“我左手能正确地拿笔，但没法协调地写，拿笔看上去一切正常，但就是没法写出任何字母。”
A colleague’s husband, Anthony Gentile, a fund manager who is 41 and grew up outside Cincinnati, told me that though he was always left-handed, he was taught to write with his right hand — though he can form the letters, he could never learn to hold the pencil correctly in that hand. “I can hold the pencil properly in my left hand, but I don’t have the coordination to write,” he told me. “It looks like I’m holding the pencil properly, but I am unable to make any letters.”
左撇子在人口中的比例似乎是相对恒定的，在10%。让我们回到洞穴绘画研究中，看看远古猎人是用哪只手持长矛，以及对古代文物进行考古分析。因此，尽管对左撇子有偏见，而且他们在发育上可能会有一些风险，Geschwind博士说，“左撇子的优势也很明显，但没有人知道它为什么这样。”
The percentage of left-handers in the population seems to be relatively constant, at 10 percent. And this goes back to studies of cave paintings, looking at which hands hunters are using to hold their spears, and to archaeological analyses of ancient artifacts. So though there has been prejudice against left-handers, and though there may be some developmental risks, said Dr. Geschwind, “there clearly must be advantages as well. The reason why it maintains that way, nobody knows what it is.”
的确，统计出有多少总统是左撇子这件事，确实增加了左撇子形象的魅力。经常有数字引述有多少建筑师或者麻省理工的教授是左撇子。而另一方面，当我们终于盼到冬季结束时，也许我们应该庆祝左撇子真正的伟大之处在于他们对运动控制、力量和最高的技巧和智慧的整合。沃伦斯帕恩，桑迪科法克斯，惠特尼福特，任何人吗？萨巴西亚，乔恩莱斯特，克里夫李？
Indeed, there seems to be a certain fascination with figuring out the areas (like the presidency) in which left-handers seem to shine. Numbers are sometimes quoted about how many architects are left-handed, or how many M.I.T. professors. On the other hand (so to speak), at a moment when we can finally hope for an end to winter, maybe we should celebrate the left-handers whose greatness truly lies in the ways they integrate motor control, strength and the highest kinds of skill and intelligence. Warren Spahn,Sandy Koufax, Whitey Ford, anyone? C. C. Sabathia, Jon Lester, Cliff Lee?