英语听力文摘 测谎仪
Lying to a Machine
不说谎的人觉得它很神秘，说谎的人觉得它很可怕，这就是神奇的测谎仪。面对不断攀升的犯罪，善良的人们总是期望借助科学的灵丹妙药，将所有犯罪分子手到擒来。测谎技术的推广者们正在说服人们相信，测谎仪就是这种灵丹妙药。现代科学证实，人在说谎时生理上的确发生着一些变化，有一些肉眼可以观察到，如出现抓耳挠腮、腿脚抖动等一系列不自然的人体动作。还有一些生理变化是不易察觉的，如：呼吸速率和血容量异常，出现呼吸抑制和屏息;脉搏加快，血压升高，血输出量增加及成分变化，导致面部、颈部皮肤明显苍白或发红等等。这一切都逃不过测谎仪的“眼睛”.据测谎专家介绍：测谎一般是从三个方面测定一个人的生理变化，即脉搏、呼吸和皮肤电阻(简称“皮电”)。其中，皮电最敏感，是测谎的主要根据，通常情况下就是它“出卖”了你心里的秘密。目前全国已有不少城市把测谎仪引入到公安、司法界。
In an ideal world, a lie detector machine would measure some involuntary response which everyone has when they lie, but not when they tell the truth. Unfortunately, there is no such response and, because of this, no such thing as a perfect lie detector. The so-called lie detector tests you’ve heard of are usually polygraph tests. How does this test work, and how accurate is it?
A polygraph generally measures four things. Electrodes on your palm measure how much you sweat. A rubber tube(橡皮管) strapped around your chest detects changes in breathing. A blood pressure cuff measures both pulse and blood pressure.
During the course of the test, the examiner usually asks about a dozen questions. Most of these are neutral–like “What is your name?”–but mixed in are the important questions–”Did you kill your wife?” for example. In theory, if a subject lies on an important question, his polygraph response will be different from the truthful responses to the neutral questions. Does this really work? It’s true that a polygraph can measure emotional stress, and it’s also true that most people have greater emotional stress when they lie. Unfortunately, many people are likely to have an emotional response to the important question, whether they lie or not. After all, “Did you kill your wife?” is more emotionally charged than “What’s your name?” This effect is so great, one study has shown that you’ve got a fifty-fifty chance of failing a polygraph test, even if you’re innocent! Because of these odds, lie detector tests are not allowed as evidence in court cases(诉讼案件).
