国家地理-2008-07-12 Lie Detector 测谎仪的奥秘（在线收听）

It might be the cheeks flushing with embarrassment or a voice choking with emotion. Our physical reactions can reveal what we truly feel. And some think they can show when someone's lying.

Typically when a person tells a lie, they begin to sweat. I'm sure we've all seen the 1940s and 50s interrogation movies where the person in the hot seat has a sweaty brow or a sweaty upper lip or perhaps sweat dripping down from their sideburns.

"All right, if you lean forward in the chair, put your arms up (in) front of you, like you're gonna dive into a swimming pool. Put this around your stomach.  "

Jack Trimarco uses physical sensations to probe for truth. His primary tool? The lie detector, or polygraph.

 "This cuff is just like the one of the doctor."

Polygraph, its work's very similar to any other biofeedback instrument. It simply records deviations from a person's physiological norm, such as someone's blood pressure going up and then coming back down, or perhaps a decrease or an increase in pulse rate, or sweat pore  activity.

"Are you sometimes known as Bobbie?"

"Yes."

A polygraph examiner knows what to look for when questioning someone.

 "D o you intend to be completely truthful with me?"

"Yes."

 Any deviation from normal could signal deception. Our body can give us away.

 "And are you sure that I won't try to trick you on this test?"

"Yes."

 We may think we're being cool, but when we're stressed, our network of nerves starts to prepare our body for action as if it's under attack. It's a response that harks back to our ancient ancestors -- fight or flight.

 It starts by triggering your stress hormone -- adrenalin. Your heart rate increases to pump more blood to your muscles as if you were about to go into battle. Your breathing deepens as vital oxygen reaches your muscles. And you begin to sweat -- the body cools so that you won't overheat when rushed into action. The brain won't let us stop the survival strategy. These basic nervous functions are automatic. That's why a polygraph can often uncover a liar.

 1. hot seat: (n., slang) 1. The electric chair used to cause death by electrocution in legal executions.

                       (informal ) 2.A position in which you can easily get into trouble.

                          e.g. A judge in a beauty contest is on the hot seat.

 2. sideburns: pl.n.（复数名词）Growths of hair down the sides of a man's face in front of the ears, especially when worn with the rest of the beard shaved off. 连鬓胡子：在耳朵前面沿着脸侧部向下生长的毛发，尤指胡子刮去之后留下的残茬

 3. hark back: To return to a previous point, as in a narrative.

e.g. he keeps harking back to his music-hall days

 4. adrenalin: [生化]肾上腺素

5. rush sb into sth