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左撇子,别自卑!

你是左撇子吗?如果答案肯定,你就属于在人群中只占十分之一的少数派。在学习、生活中,也许你曾遭遇过一些尴尬和痛苦,比如,吃饭的时候怕和你的筷子打架,谁都不愿意挨着你坐。比如,从左至右的书写过程中,手指会蹭花刚刚写下的字。再比如,手工课上用剪刀会让你的左手酸疼……不仅如此,在曾经愚昧的社会时期,左撇子还因为是少数派而常常遭受歧视,甚至在今天的英文中,还有“Sb. has two left feet”(某人有双蠢笨的脚)这样蔑视左撇子的俚语,而right(右)则代表“正确、可以、权力”等等积极的含义。 随着社会的开明程度不断提高,左撇子们的境遇变得越来越好,甚至在某些领域还独占鳌头。比如,在体育竞赛中,左撇子的击剑手、棒球投球手、拳击手,相比于同实力右撇子选手,则更容易获得胜利。再来看一个事实,在美国的倒数前7任总统中,有4位都是左撇子——福特、老布什、克林顿和奥巴马(图1)。左撇子并非生理缺陷,而是正常的遗传现象,科学家称它为“偏侧优势”。

【图1:美国的左撇子总统们,图片出处:http://www.nytimes.com/2011/03/0 ... r=1&ref=science】

动物世界中的左撇子

动物世界中也有偏侧优势的现象吗?有,没准你家的猫咪就是常喜欢用左前爪的左撇子呢。来自英国的研究人员以42只家猫为研究对象,让它们完成一项复杂的取食任务——从一个窄口罐子中取出金枪鱼肉(图2)。结果发现,在十几次的取食测试中,21只母猫有20只都使用右爪。而21只公猫中有20只习惯用左爪……研究人员说,家猫对左右爪的使用偏好只有在完成一些较复杂的任务时才十分明显。这就好比对人来说,打开一扇门用左右手都可以轻松搞定,但涉及用筷子或写字这样的复杂行为时,就开始体现出左手或右手使用偏好。用你家里的猫咪验证一下这个实验吧?当然,前提是你家的咪咪没有进行过阉割手术。

【图2:检测猫咪的偏侧优势,图片出处:http://www.guokr.com/article/507 ... mp;utm_campaign=rec 】

按照上面的实验结论,猫咪们是“男左女右”的坚定执行者,宠物狗们则没有这么统一。澳大利亚悉尼大学兽医学院的保罗·麦克里维(Paul McGreevy)博士领导的研究小组在对270只种类不同的狗进行长期观测后发现,15%的狗是右撇子,15%的狗则是“左撇子”,剩下70%的狗没有明显的使用偏好。麦克里维认为,左撇子或右撇子的狗更容易被训练成为适合特定工作的狗,比如导盲犬或警犬。那些对左爪或右爪缺乏使用偏好的狗更容易对声音产生恐惧。他说:“如果一只狗被打雷声或鞭炮声吓得半死,显然它不适合做缉毒犬或导盲犬。”推广麦克里维博士的方法,可以帮助人们在训练特种狗(图3)和挑选优秀的宠物狗时,节约大量的时间和金钱。

【图3:有偏侧优势的狗有出色的表现,图片出处:http://www.guokr.com/article/507 ... mp;utm_campaign=rec】

如何判断你家的宠物狗是“左撇子”还是“右撇子”?并不是一件容易的事情。麦克里维和他的研究小组准备了一种圆筒状的容器,里面盛好狗食。接受测验的狗要吃容器里的食物,就必须用一只爪子按住容器,使之静止不动。每只狗接受100次这样的测验,然后研究人员根据这100次内这只狗使用左爪和右爪的偏好,判断这只狗是“左撇子”还是“右撇子”。有时候,仅判断一只狗的偏侧性就需要花费4小时左右时间。如果你的时间充裕,不妨在家中试试看? 家里养的宠物鹦鹉的同学们!如何来检测你家的鹦鹉是哪侧优势呢?可以准备一些水果给它,看它最经常用哪只爪子来抓。科学家们的研究指出,大部分鹦鹉都是左撇子(图4)。

【图4:大部分鹦鹉是左撇子,图片出处:http://news.bbc.co.uk/earth/hi/e ... 9382000/9382181.stm】

想一想,在田径场上跑步时,你喜欢逆时针还是顺时针跑?大部分人及正规的竞赛都选择逆时针方向奔跑,这是因为我们人类的心脏在身体的左侧,相对右侧更沉,逆时针绕圈更稳定。因此,右腿比左腿迈的步子更大的“左腿主导马”(左撇子马),因左拐时更具优势而更受到骑手们的青睐。有些驯马者还会采用遮住马的左眼,鼓励马儿更大幅度地去迈右腿的方式来调整那些“右腿主导马”(右撇子马),以便它们能更好地竞赛。 软体动物蜗牛,好像没有明显的肢体来表决自己对于左还是右更青睐,但通过它们硬壳上的清晰螺纹,科学家发现,在已知的70000种蜗牛中只有大约10%是左旋的(左撇子),右旋的(右撇子)占了绝大多数(图5)。

【图5:大部分软体动物的壳是右旋的,图片地址:http://en.wikipedia.org/wiki/Gastropod_shell

2009年一篇来自著名科学杂志Nature的文章指出,决定蜗牛的壳左右旋转的是一个名叫Nodal的基因。该基因在蜗牛受精卵分裂成4个细胞时开始起作用,如果将这个基因掩盖住,不让它作用,蜗牛的壳的螺旋现象就消失了。

【图6:a,e为对照;b,c,d,f,g,不同程度地掩盖了Nodal基因,正常情况下产生的螺旋消失了。图片出处:http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2661027/

结语

其实,在动物世界中,无论是哺乳动物、鸟类、鱼类还是无脊椎动物,这样的偏侧优势现象到处都是。它的成因,是演化长河中,和多变的环境不断相互适应的过程中,变得日趋复杂的神经系统。

参考资料

  1. 美国总统中的左撇子们:http://www.nytimes.com/2011/03/0 ... r=1&ref=science
  2. 猫咪的性激素决定左右撇(英国贝尔法斯特女王大学一个研究小组在2009年8月第78期《动物行为学》杂志上报告):http://www.sciencedirect.com/sci ... i/S0003347209002644
  3. 狗狗左撇子:http://standeyo.com/NEWS/06_Animals/060904.dog.paws.html
  4. 鹦鹉大多数是左撇子:(1)Zeigler, H. Phillip & Hans-Joachim Bischof, eds. Vision, Brain, and Behavior in Birds. Cambridge, MA: MIT Press, 1993. 239. (2)http://news.bbc.co.uk/earth/hi/e ... 9382000/9382181.stm
  5. 蜗牛的壳:http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2661027/
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22 Responses to “[少儿科普]动物中也有“左撇子””

  1. 大兔子说道:

    本人是左撇子,用筷子和用笔因为强制纠正都是右手,其它自学的(比如打羽毛球,掷铅球)都是左手

    • 雄心勃勃的左撇子说道:

      我和你一样,吃饭和写字都是右手其他都左手,因为别老爸强行用棍子揍出来的,现在想想,挺庆幸,用左手最不方便的两件事儿,被揍了过来,呵呵

  2. 周明玮说道:

    我在这里举几个动物“右撇子”的例子:乌鸦制作工具,撕扯树叶从右边下口;89%的海象觅食时习惯使用右肢,77%的座头鲸喜欢用右侧的鳍状肢拍打水面;因为右旋的蜗牛明显多于左旋的蜗牛,所以以蜗牛为食物的钝头蛇右下颚的牙齿多于左下颚的;鸡在寻找地上的种子时习惯用右眼对着地面;有三种蟾蜍习惯用右前肢拂拭脸上的碎渣。(以上资料出自2007年第6期《野生动物小哥白尼》《动物右撇子小分队》。

  3. Illusiwind说道:

    喵星人又胜出了……

  4. 我是搓板说道:

    图5没有等轴侧视图不幸福_(:э」∠)_

  5. 我以为说道:

    外国人常见用左手写字 不代表他们是左撇子 怎么还有这么多人搞不清 包括本文作者.....他们只是左手写字而已 其他都还是用右手...因为从学写字开始没有被强制用哪只手 喜欢哪个就哪个...如果咱们这的写字教育不强制用右手 那至少也会有一般的人群用左手写字 ...

    • 我以为说道:

      自由领导人民

    • watson说道:

      这样啊。。。只听说欧美秘书会专门训练左手写字右手拿电话。。。实在不理解他们为什么不右手写字左手拿电话

  6. 播放说道:

    "这是因为我们人类的心脏在身体的左侧,相对右侧更沉,逆时针绕圈更稳定。"这个说法应该是错的,肝比心脏重大概5倍,在右侧。如果一个器官能决定哪边更沉,那就应该是右侧的肝脏。

  7. adfg说道:

    我哥是左撇子,但我喜欢和他吃饭时坐他左边,我觉得筷子打架好玩!嘻嘻嘻嘻嘻嘻嘻嘻嘻嘻嘻嘻嘻嘻

  8. 乐刚说道:

    听说左撇子的人普遍都很聪明啊,是不是从小左右脑一起开发的原因呢。。

  9. 大奇说道:

    左撇子是天生的,没有刻意开发,从小思维方式、思考方式都和绝大多数人不一样,这才是问题所在,当然左手确实更灵活更有力!每天无时无刻不在自主思考,过耳不忘、过目不忘,嘿嘿!左撇子的世界是多姿多彩的~很难被外界左右的~

  10. 晨曦过早说道:

    我亲戚家有个表妹,他们班有个叫任昊的,就是左撇子,笨得很呢!

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