听力原文：Lie detectors, those controversial assessors of truth, are making their way into

听力原文： Lie detectors, those controversial assessors of truth, are making their way into everyday life. Insurance companies use them to help catch people filing fraudulent claims. Suspicious spouses use hand-hand versions to judge whether their significant others are cheating. Interrogators for the US government use them to double check analysis of who might be terrorists.

Polygraphs, which have been used for decades, have been joined by new systems that purportedly analyze a person's voice, blush, pupil size and even brain waves for signs of deception. The devices range from costly experimental devices that use strings of electrodes or thermal imaging to ＄19. 95 palm-sized versions.

No studies have ever proven that lie detectors work. Many show that they assess truth as accurately as a coin flip; in other words, not at all. Still, some people have come to depend on them. The recent proliferation of lie detectors has reignited a decades-old debate over the ethics and politics of when and how they should be used and whether such important questions as guilt or innocence should be left to machines.

Mankind has looked for centuries for a physical indicator that would expose a liar. The Romans studied the entrails of suspected liars. In China, rice was shoved into the mouths of interviewees to measure how dry they were -- the drier the mouth, the more likely the person was lying, it was thought. Other cultures tried various chemical concoctions, but they worked no better than chance.

Especially since September 11, law enforcement agencies consider lie detection systems critical to their investigations. The CIA, FBI and Defense Department have spent millions of dollars on them. In an unusual plea made soon after the terrorist attacks, the government asked for the public's help in building counterterrorism technologies, among them a portable polygraph.

In the United States, there is a double standard when it comes to the use of polygraphs. Although the so-called lie detector is considered an important law enforcement tool, polygraph data are inadmissible as evidence in a court of law. The US Supreme Court forbade private companies from using them to screen job applicants, but allowed the government to use them for the same purpose.

As debate about polygraphs rages, the devices are being phased out in favor of voice analyzers, which are more portable and easier to use. A voice analyzer device typically consists of a telephone and microphone attached to a computer that packs neatly in a briefcase, or attached to any PC with the proper software installed. Most of the analyzers can be used in person or over the phone. Conversations can be tested in real time or recorded for later analysis.

First, the questioner asks an interviewee about something he or she would have no reason to lie about, such as "When's your birthday？" Then he asks what he really wants to ask. The device makes an assessment about whether the subject is telling the truth based on the differences between the inaudible microtremors in the voice during the first round of questioning and those in the second.

The federal government officially says it does not use these voice lie detectors. Still, the voice technology has its true believers, among them more than 1,200 police departments nationwide and tens of thousands of consumers.

The slightly more sophisticated Truster software program that runs on a desktop computer gives text rating of truthfulness. The companies that market these technologies say they are more than 80 percent accurate.

Though skeptical, Rick Garloff, a 35-year-old American, still said even if the systems are not great lie detectors, they are wonderful lie deterrents. He once used the Truster on his 9-year-old son, to see if he had forgotten to close a door, accidentally letting the d