What exactly is a lie? Is it anything we say which we know is untrue? Or is it something more than that? For example, suppose a friend wants to borrow some money from you. You say “I wish I could help you but I'm short of money myself." In fact,  you are not short of money but your friend is in the habit of not paying his debt and you don't want to hurt his feelings by reminding him of this. Is this really a lie ?

    Professor Jerald Jellison of the University of Southern California has made a scientific study on lying.  According to him, women are better liars than men, particularly when telling a "white lie," such as when a woman at a party tells another woman that she likes her dress when she really thinks it looks awful. However, this is only one side of the story. Other researchers say that men are more likely to tell more serious lies, such as making a promise which they have no intention of fulfilling.  This  is the kind of lie politicians  and businessmen are  supposed to be particularly skilled at:the lie from which the liar hopes to profit or gain in some way.
        
    Research has also been done into the way people's behavior changes in a number of small,apparently unimportant ways when they lie. It has been found that if they are sitting down at the time, they tend to move about in their chairs more than usual. To the trained observer they are saying,"I wish I were somewhere else now." They also tend to touch certain parts of the face more often, in particular the nose. One explanation of this may be that lying causes a slight increase in blood pressure. The tip of the nose is very sensitive to such changes and the increased pressures make it itch.
        
    Another gesture which gives liars away is what the writer Desmond Morris in his book Manwatching calls “the mouth cover." He says there are several typical forms of this,such as covering part of the mouth with the fingers, touching the upper-lip or putting a finger of the hand at one side of the mouth.Such a gesture can be understood as an unconscious attempt on the part of the liar to stop himself or herself from lying.
        
    Of course, such gestures as rubbing the nose or covering the mouth, or moving about in a chair cannot be taken as proof that the speaker is lying. They simply tend to occur more frequently in this situation. It is not one gesture alone that gives the liar away but a whole number of things, and in particular the context in which the lie is told.

谎言究竟是什么？是说一一些我们知道不是真实的事情？还是甚于这些？例如，假设一个朋友向你借钱。你说“我希望能帮助你，但我现在自己也缺钱”。实际上，你并不缺钱，但是你的这位朋友却有欠钱不还的习惯，而你又不想提醒他这点而伤害他的感情。这是一个真正的谎言吗？

南加州大学的Jerald Jellison教授做过一个关于说谎的科学研究。他的研究显示女人比男人更善于说谎，特别是说“善意的谎言”，例如在一个派对上一个女人对另一个女人说她喜欢对方的衣服而实际上她认为那衣服很难看。然而这只是故事的一方面。其他的研究者称男人更倾向于说一些较严重的谎言，例如承诺他们从来没想过要实现的承诺。政客和商人似乎特别擅长于此类谎言：说谎者可从谎言中获利或在某些方面得到好处。

同样也有人研究当人们说谎时他们行为的一些细小的、看似不重要的改变。结果表明如果他们当时坐着，那么他们会比往常更多地在椅子上动来动去。在受过训练的观察者看来，他们这样做是在说“我希望我是在另外一个地方”o他们也会更多地触摸脸部的某些部分，特别是鼻子。一个解释是说谎会使血压产生微小的变化。鼻尖对这样的变化非常敏感，血压的增加使得它发痒。

另一个将说谎者出卖的拳动是在Desmond Morris的书《人类观》(Manwatching)中提到的“捂嘴”。他说有几种典型的动作形式，例如用手指掩住嘴的一部分，摸上嘴唇或者一个手指支在嘴角。这样的行为可以看做是一种阻止说谎者继续说谎的下意识举动。

当然，这些举止，例如摸鼻子或者掩盖嘴唇，或者在椅子上动来动去，都不能作为讲话者正在说谎的证据。只是这些行为在这样的情况下更容易发生。不是一个举止就可以将说谎者出卖，而是一系列的事情，特别是说谎者说谎的上下文背景。